MODULES 1 and 2 Flashcards
(392 cards)
1
Q
What are prokaryotic organisms?
A
They are just one prokaryotic cell ( single cellular) Eg. bacteria
2
Q
What are Eukaryotic organisms?
A
Made up of many eukaryotic cells (multi cellular) Eg. plants and animals
3
Q
Differences between a plant and animal cell?
A
Plant has all organelles in an animal cell plus: Cell wall with plasmodesmata Vacuole Chloroplasts
4
Q
Description and function of plasma (cell surface) membrane?
A
Found on surface of animal cells, and inside cell wall of plant cells and prokaryotic cells. Made up mainly of lipids and protein Regulates movement of substances in and out of the cell Has receptor molecules that allow it to respond to chemicals like hormones
5
Q
Description and function of cell wall?
A
Rigid structure that surrounds plant cells it’s mainly made of cellulose Supports plant cells
6
Q
Description and function of the nucleus?
A
A large organelle surrounded by a nuclear envelope (double membrane) which contains many pores Contains chromatin (made up from DNA and proteins), and a structure called the nucleolus Controls the cells activities by controlling the transcription of DNA DNA contains instructions to make proteins The pores allow substances to move between the nucleus and the cytoplasum The nucleolus makes ribosomes
7
Q
Description and function of lysosomes?
A
A round organelle surrounded by a membrane Contains digestive enzymes which are kept separate from the cytoplasm by the surrounding membrane Used to digest invading cells or to break down worn out components of the cell
8
Q
Description and function of a ribosome?
A
Very small organelle which either floats free in the cytoplasm, or is attached to the rough endoplasmic reticulum Site where proteins are made
9
Q
Description and function of Rough endoplasmic reticulum?
A
A system of membranes covered with ribosomes Folds and processes proteins which have been made at the ribosomes
10
Q
Description and function of smooth endoplasmic reticulum?
A
Similar to RER except no ribosomes Synthesises and processes lipids
11
Q
Description and function of a vesicle?
A
Small fluid filled sac in the cytoplasm surrounded by a membrane Transports substances in and out of the cell
12
Q
Description and function of the golgi apparatus?
A
Fluid filled membrane bound flattened sacs Processes and packages new lipids and proteins Also makes lysosomes
13
Q
Description and function of a mitochondrion?
A
Have a double membrane Inner one is folded to form cristae Inside is the matrix which contains enzmyes for respiration Site of aerobic respiration and where ATP is produced
14
Q
Description and function of a choroplast?
A
Surrounded by a double membrane, and has membranes inside thylakoid membranes, which stack into grana Grana are linked together by lamellae Site of photosynthesis
15
Q
Description and function of centrioles?
A
Small hollow cyclinders made of microtubules Involved in seperation of chromosomes
16
Q
Description and function of Cilia?
A
Hair like substances found on the surface membrane of some animal cells Cross section has a ring of 9 pairs of protein microtubules inside with a pair in the middle aswell Allows movements of substances on the cell surface
17
Q
Description and function of a flagellum?
A
Like Cilia except longer Propels cells
18
Q
How are organelles involved in protein production?
A
Proteins are made at the ribosomes The Ribosomes on the rough endoplasmic reticulum make proteins that are excreted or attached to the cell membrane New proteins produced at the rough endoplasmic reticulum are folded and processed (sugar chains added) by the rough endoplasmic reticulum Then they are transported from the rough ER to the golgi apparatus in vesicles At the golgi apparatus the proteins undergo further processing Proteins enter more vesicles and are secreted out of the cell
19
Q
What is the cytoskeleton of a cell?
A
Network of protein threads running through a cell, arranged as microfilaments (small solid strands) and microtubules (tiny protein cylinders)
20
Q
4 Main functions of the cytoskeleton?
A
The microtubules and microfilaments support the cell’s organelles, keeping them in position. Helps strengthen the cell and maintain it’s shape Responsible for movement of materials within the cell, eg. chromosomes when they separate during cell division, relies on contraction of microtubules in the spindle Can cause the cell to move, eg in cillia or flagellum
21
Q
How does a prokaryote’s cell size comapare to a eukaryote’ss cell size?
A
prokaryote’s cell size is very small (less than 2 um diameter Eukaryotes much larger, (10-100 um)
22
Q
What’s the DNA like in a prokaryote’s cell compared to a eukrayotes cell?
A
prokaryote’s cell DNA is circular, whilst a eukaryotes is linear
23
Q
Where is the DNA found in a prokaryote’s cell compared to a eukaryotes cell?
A
In a prokaryote’s cell there is no nucleus, so DNA is free in the cytoplasm Whereas in a eukaryote, nucleus is present so it’s found within the nucleus
24
Q
What’s the cell wall in prokaryote’s cell like compared to a eukaryotes cell?
A
In a prokaryote’s cell it’s made of a polysaccharide, but not cellulose or chitin No cell wall in animal cells, cellulose in plants and chitin in fungi
25
How do the amount and type of organelles in a prokaryote's cell compare to a eukaryotes cell?
In a prokaryote's cell very few organelles and none are membrane bound In a eukaryotes cell, many membrane bound organelles present
26
How do the ribosomes differ in a prokaryote's cell compared to a eukaryotes cell?
Small ribosomes in a prokaryote's cell, and larger ribsomes in a eukaryotic cell
27
Structure of a bacterial cell?
Flagellum to propel cell DNA (bacterial chromosome) Plasmid (ring of DNA) Plasma membrane Cell wall Ribosomes
28
Magnification definition and formula?
How much bigger the image is than the specimen Magnification = image size / object size
29
Resolution definition?
How well a microscope can distinguish between 2 points that are really close to each other
30
How to convert between mm, um and nm?
mm = 1m x 10^-3 um= 1m x 10^-6 nm= 1m x 10^-9
31
Features of a light microscope?
Uses light Have lower resolution that electron microscopes (0.2um) Maximum magnification of a light microscope is x1500
32
Features of a scanning confocal microscope?
Use laser beams on a specimen tagged with fluorescent dye Laser causes dye to fluoresce, which is directed through a pinhole onto a detector connected to a computer which can produce a 3D image Pinhole creates a clearer image, as all out of focus light is blocked Can look at specimens at different depths
33
Features of a transmission electron microscope?
Uses electromagnets to focus a beam of electrons which is transmitted through the specimen, in which denser parts of the specimen absborb more electrons, which then appear darker in the image Only work on thin specimens Resolution of 0.0002 um Magnification of more than 1,000,000
34
Features of a scanning electron microscope?
Scans a beam of electrons across the specimen, knocking electrons off, which are collected in a cathode ray tube to form an image. Image can be 3D Resolution 0.002 um Magnification x 500,000
35
Using a light microscope, how do prevent the problem of the sample being transparent so the electrons pass straight through?
Can stain the sample, different parts take more up than others the contrast makes different parts show up
36
How do you stain samples for an electron microscope?
Objects are dipped into a solution of heavy metal, the metal ions scatter the electrons creating contrast again
37
How do you prepare a dry mount?
Use tweezers to put specimen on a slide, and put a cover slip on top
38
How do you prepare a wet mount?
Pipette a small drop of water onto the slide, use tweezers to put your specimen on top of water drop Put a cover slip on avoiding air bubbles Add a stain to one side of your specimen and put paper towel opposite side to draw it in
39
How do you find the value of each eye piece unit of an eyepiece graticule?
Use a stage micrometer, to measure what eyepiece unit is worth, need to re calibrate for different magnifications
40
Functions of water inside and outside of cells?
Water is a reactant in many important chemical reactions It's a solvent, so allows biological reactions to take place in solution Water transports substances, liquid and a solvent so very useful can transport substances such as glucose and oxygen Helps temperature control as has a high specific heat capacity and high latent heat of evaporation It's a habitat`
41
Why is water a polar molecule and what does this allow it to do?
Oxygen has a higher electronegativity than hydrogen, so attracts the electrons more making the oxygen delta negative, and the hydrogen's delta positive Hydrogen bonding, as the delta positve hydrogen's are attracted to the delta negative electrons of other water molecules
42
How can hydrogen bonding give water a high specific heat capacity?
Specific heat capacity is the energy required to raise the temperature of 1 gram of substance by 1 degree Hydrogen bonds between water molecules can absorb a lot of energy, meaning water requires a lot of energy to heat up Meaning it has a very stable temperature
43
How do hydrogen bonds give water a high latent heat of evaportation?
Hydrogen bonds mean that it takes a lot of energy to break the intermolecular forces between water molecules, so a lot of energy used up when water evaporates Good for cooling organisms, as when sweat evaporates it cools the surface of the skin
44
What's cohesion and why are water molecules very cohesive and what does this help them do?
Is the attraction water molecules of the same type Occurs in water molecules as they are polar Helps them flow so they are good for transporting substances
45
How does water's polarity make it a good solvent?
It can dissolve salts as the delta positively charged hydrogen's will surround the negatively charged ions, and the delta negative oxygens will surround the positively charged ions, seperating out the salt causing it to dissolve
46
Why is water less dense when it is a solid?
Water molecules are held further apart in ice than they are in liquid, because each water molecule forms 4 hydrogen bonds to other water molecules making a lattice shape This is why ice floats
47
Why is ice floating useful to living organisms?
Ice acts as an insulating layer on top of the water, so the water bellow doesn't freeze killing the living organisms
48
Most carbohydrates are polymers, what's a polymer?
A molecule made up of many similar, smaller monomers bonded together
49
Structure of glucose?
It's a hexose ( 6 carbon) monosaccharide Alpha glucose: starting at top right then going clockwise C1 bonded to CH2OH O C2 bonded to H above and OH bellow C3 bonded to H above and OH bellow C4 bonded to OH above and H bellow C6 OH bellow and H above Beta: the same as alpha, except on C2 OH is above, and H is bellow
50
How is glucose's structure related to it's function?
It's the main energy source in animals as it's structure makes it soluble, so can be transported easily, and it's chemical bonds contain a lot of energy
51
What's ribose?
Monosaccharide with five carbon atoms so it's a pentose sugar Structure starting from Top of pentagon: O C1 OH above and H bellow C2 H above and OH bellow C3 H above and OH bellow C4 H bellow and CH2OH above
52
What elements do carbohydrates consist of?
Carbon Oxygen Hydroged
53
How do 2 monosaccharides bond together?
Via a condensation reaction A hydrogen atom from one monosaccharide binds to the OH group of another monosaccharide releasing a molecule of water, and forming a glycosidic bond (both molecules binded to each other by an oxygen) This a condensation reaction Forms a disaccharide
54
What's the reverse of a condensation reaction?
A hydrolysis reaction, water is removed to split a molecule
55
What does the disaccharide maltose consist of?
2 molecules of alpha glucose binded to each other via a glycosidic bond
56
What does the disaccharide sucrose consist of?
When alpha glucose and fructose join together via a glycosidic bond
57
What does the disaccharide Lactose consist of?
When Beta glucose is bonded to galactose
58
What's a polysaccharide?
When more than 2 monosaccharides join together
59
What do plants store excess glucose as?
Starch, when a plant needs energy breaks it down into glucose
60
What does starch consist of?
A mixture of the 2 polysaccharides of alpha glucose amylose and amylopectin
61
Describe the structure of amylose?
A long unbranched chain of alpha glucose. The angles of glycosidic bonds give it a coiled structure Condense structure makes it good for storage as can fit more into a smaller space
62
Describe the structure of amylopectin?
A long branched chain of alpha glucose, it's side chains allow the enzymes that break down the molecule to get at the molecule to break the glycosidic bonds. So glucose can be released quickly
63
How do animal cells store glucose?
Store it as glycogen, another polysaccharide of glucose
64
Structure of glycogen?
Polysaccharide of alpha glucose, similar to amylopectin, except that it has far more side branches coming off it, so energy can be released more readily, which is good for animals
65
Why is it useful that starch is insoluble in water?
Means it doesn't cause water to enter cells via osmosis, which would make them swell
66
Describe the structure and function of hydrogen bonds?
Long unbranched chains of beta glucose, the cellulose chains are linked by hydrogen bonds to form strong fibres called microfibrils The strong fibres provide strucutral support for the cell, eg. in plant walls
67
Explain the general structure of a triglyceride?
Glycerol bonded to 3 fatty acid chains Fatty acid chains are made of hydrocarbons (compounds that only contain hydrogen and carbon) The tails are hydrophobic, meaning the tails are insoluble in water
68
What elements do lipids contain?
Carbon, Oxygen and Hydrogen
69
How are triglycerides synthesised?
By the formation of an ester bond between each fatty acid and the glycerol molecule A condensation reaction occurs, between the OH group on the glycerol (prop-tri-ol) and the OH of the carboxylic group at the end of the hydrocarbon chain.
70
What's the process of synthesising a triglyceride called?
Esterfication
71
What's the type of reaction called which breaks down a triglyceride?
Hydrolysis
72
What's a saturated fatty acid?
Hydrocarbon chain containing no double carbon carbon double bonds (saturated with hydrogen)
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What's an unsaturated fatty acid?
Hydrocarbon chain which has at least one carbon carbon double bond, causing it to kink
74
Structure of phospholipids?
The same as a triglyceride, except missing a fatty acid chain, in replace for a phosphate group in the other direction. The phosphate group is hydrophillic (attracted to water) and the and the fatty acid chains are hydrophobic
75
Why are triglycerides good energy storage molecules in animals and plants?
The hydrocarbon tails contain a lot of chemical energy when they are broken down They are insoluble, so don't affect water potential of cell, causing water to move in via osmosis, they are insoluble as Triglycerides bundle together as insoluble droplets, as glycerol shields hydrophobic fatty acid chains as they all face inwards to form a sphere
76
Describe the structure and function of a phospholipid bilayer?
Formed from a double layer of phospholipids, tails facing inwards as hydrophobic and phosphate heads facing outwards as hydrophillic Centre of the bilayer is hydrophobic, preventing water soluble substances passing through
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What are the monomers of proteins?
Amino acids
78
What is a dipeptide?
When 2 amino acids join together
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What is a a polypeptide?
When more than 2 amino acids join together
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What are proteins made up of?
One or more polypeptides
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General structure of an amino acid?
Carbon in centre Amine group to the left (NH2) Carboxylic group to the right (COOH) Hydrogen bellow R group above
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What separates all amino acids?
They have different R groups
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How are amino acids joined together?
A condensation reaction occurs between the OH of the Carboxylic group and the H of the amine group, removing water and forming a peptide bond
84
How do you split 2 amino acids?
Via a hydrolysis reaction
85
What's the primary structure of a protein?
The sequence of amino acids in the polypeptide chain
86
What's the secondary structure of a protein?
When hydrogen bonds form between nearby amino acids This makes it coil into an alpha helix, or fold into a beta pleated sheet, this is the secondary structure
87
What's the tertiary structure of a protein?
The coiled or folded chain of amino acids is often coiled and folded further. More bonds form between different parts of the polypeptide chain, forming their final 3D structure
88
What's the Quaternary structure of a protein?
When a protein is made of several different polypeptide bonds held together by bonds, the quartenary structure is the way these polypeptide chains are assembled together Eg. haemoglobin is made up of 4 polypeptide chains
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What bonds are present in the primary structure of a protein?
Peptide bonds
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What bonds are present in secondary structure?
Hydrogen bonds
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What bonds are present in tertiary structure?
Ionic bonds between negatively charged R groups, and positively charged charged R groups Disulfide bonds, forms between 2 amino acids of csyteine, as it's sulphur containing Hydrophobic and hydrophillic interactions Hydrogen bonds
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What elements do proteins contain?
All contain Oxygen, Hydrogen, and Nitrogen Some contain sulphur
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Structure of a globular protein?
Hydrophillic R groups on the outside, making them soluble, so they're easily transported in fluids
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Structure and function of the globular protein haemoglobin?
Carries oxygen around the body in red blood cells It's a conjugated protein meaning it's a protein with a non protein group attached (prosthetic group) So each prosthetic group has a prosthetic group called haem, which contains iron, which oxygen binds to
95
Structure and function of the lipid cholesterol?
Has a hydrocarbon ring structure, attached to a hydrocarbon tail. The ring structure has a polar hydroxyl OH group attached to it Helps strengthen the cell membrane, by interacting with the phopholipid bilayer Has a small size and flattened shape, so can fit in between the phospholipid molecules in the membrane They bind to hyrophobic tails of the phospholipids, causing them to pack together more closely, this helps the membrane be less fluid and more rigid
96
Structure and function of the globular protein insulin?
Hormone secreted by the pancreas, helps regulate blood glucose level. Solubility important, as it can be transported in the blood to the tissues where it acts Consists of 2 polypeptide chains which are held together by disulphide bonds
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Structure and function of the globular protein amylase?
Enzyme, that catalyses the breakdown of starch in the digestive system Made of a single chain of amino acids, it's secondary structure contains both alpha helix, and beta pleated sheets
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3 Types of fibrous proteins?
Collagen Keratin Elastin All insoluble, strong and structural
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Structure and function of the fibrous protein collagen?
Found in animal connective tissue (bone, muscle) Very strong, minerals can bind to increase it's rigidity
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Structure and function of the fibrous protein keratin?
Found in external structures of animals, eg skin, hair and nails Can be flexible or very tough
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Structure and function of elastin?
Found in elastic connective tissue, such as skin and large blood vessels Elastic so allows tissues to return to their original shape after being stretched
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What's an ion with a positive charge called?
Cation
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What's an ion with a negative charge called?
Anion
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What does the inorganic ion Ca2+ do?
Involved in the transmission of nerve impulses Involved in release of insulin from pancreas Acts as a cofactor for many enzymes Important for many enzymess
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What does the inorganic ion Na+ do?
Important in generating nerve impulses for muscle contraction Regulating fluid balance in the body
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What does the inorganic ion K+ do?
Important in generating nerve impulses for muscle contraction Regulating fluid balance in the body Activates essential enzymes needed for photosynthesis
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What does the inorganic ion H+ do?
Affects the pH of substances Important for photosynthesis reactions that occur in the thylakoid membranes inside chloroplasts
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What does the inorganic ion NH4+ do?
Absorbed from soil by plants as an important source of Nitrogen
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What does the inorganic ion NO3 - (nitrate) do?
Absorbed from soil by plants, and is an important source of Nitrogen
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What does the inorganic ion HCO3- (hydrogen carbonate) do?
Acts as a buffer, which helps maintain the pH in the blood
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What does the inorganic ion Cl- do?
Involved in the chloride shift, which helps maintain the pH of the blood during gas exchange Acts as a cofactor for amylase
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What does the inorganic ion PO4(3-) do?
Involved in photosynthesis and respiration reactions Needed for synthesis of nucleotides
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What does the inorganic ion OH- do?
Affects the pH of substances
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What are reducing sugars?
All the monosacchardies, and the disacharides maltose and lactose
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How do you test for a reducing sugar?
Add benedict's reagent and heat, will go from blue to brick red The higher the concentration of the reducing sugar, the further the colour change
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How do you test for a non reducing sugar?
If the test for the reducing sugar is negative, then add dilute HCl and heat in a water bath Nuetralise it with Sodium Now do the Benedict's test again
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What can be used to test for glucose?
Test strips
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How can you test for starch?
Add Iodine dissolved in potassium iodide solution, if present, sample will change from browny orange to a dark blue/black colour
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Can you test for proteins?
Use the Biruet test Solution needs to be alkaline, so add a few drops sodium hydroxide solution Add some copper sulphate solution, if it goes stays blue there's no protein, if goes purple protein is present
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How do you test for lipids?
The emulsion test Shake the substance with ethanol then pour into water Solution will go milky if a lipid is present
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How do you use calorimetry to measure the concentration of a glucose solution?
Create glucose concentrations using dilution factor 2 on 40m/M to create a 20, 10, 5 and 2.5 and a negative control of water You will have added benedict's reagent, so the higher the concentration gradient of glucose, the lower the absorbance as more benedict's reagent used up, as will have also remove precipitate by centrifuging it Now create a calibration curve by plotting absorbance on y axis, and concentration on x axis (use red filter) Now can use graph to find link the absorbance of a solution with an unknown concentration, with it's concentration
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What's a biosensor?
A device that uses a biological molecule such as an enzyme
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How would you use paper chromatography to identify unknown amino acids?
Have a mobile phase, a liquid solvent which allows the amino acids to move Have a stationary phase, where the molecules can't move eg chromatography paper Put concentrated dots of the amino acids at the end of the chromatography paper, put in solvent and they'll move up the paper at different rates so they'll seperate out Spray with ninhydrin spray, to make them purple so more visible Calculate the R value of each value (distance moved by amino acid/ distance moved by solvent) then compare R value with a data base to work out what amino acids they are)
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Function of an enzyme?
To speed up metabolic reactions, by acting as a biological catalyst
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An example of an intracellular enzyme (works within cells)?
The enzyme catalase breaks down hydrogen peroxide to harmless oxygen and water Hydrogen peroxide is the toxic by product of some cellular reactions, and can kill cells
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2 Examples of extracellular enzymes (work outside cells)?
The enzyme Amylase is found in saliva and is secreted into the mouth by cells in the saliva gland, it catalyses the hydrolyses of starch into maltose The enzyme trypsin catalyses the hydrolysis of peptide bonds so breaks down large polypeptides. It's produced in the pancreas, and secreted into the small intestine
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What type of protein are enzymes?
Globular
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What do enzymes have which makes them specific to certain molecules?
An active site with a specific shape, which is where the molecule binds to, so they have to be complementary
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What level of structure determines the active site?
Tertiary structure
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How do enzymes reduce activation energy and therefore speed up the rate of reaction?
When a substance binds to an enzyme, an enzyme substrate complex is formed, this then lowers the activation energy (amount of energy that needs to be supplied to the chemicals before the reaction will start) If 2 substrate molecules need to be joined, then attaching the enzyme holds them closer together, reducing any repulsion between the molecules so they can bind more easily If the enzyme is catalysing a break down reaction, fitting into the active site puts a strain on the bonds in the substrate, this strain means the substrate molecule breaks up more easily
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Describe the lock and key model?
The substrate binds to the active site of the enzyme as complementary , and forms an enzyme substrate complex An enzyme product complex is then formed and products are released, leaving the enzyme unchanged after the reaction
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What does the induced fit model add to the lock and key model?
That when the substrate binds to active site, the active site changes shape slightly to fit the substrate more closely
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Explain the process of heating an enzyme up to denaturation?
Initially rate of reaction will increase, as the increase in thermal energy means an increase in kinetic energy, meaning molecules move faster so more frequent collisions and also more successful collisions, so more enzyme substrate complexes formed per unit time. However if temperature reaches a certain point, starts to denature. The rise in temperature makes the molecules vibrate more, which then starts to break bonds in tertiary structure (weakest to strongest). Causes tertiary shape to change, and enzyme and substrate are no longer complementary
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What is the temperature coefficient (Q10)?
Shows how much the rate of reaction changes when there's an incresase of 10 degrees Before the optimum enzymes have a value of around 2
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What can a different pH do to the optimum, do to an enzyme?
H+ ions and OH- ions can disrupt the hydrogen and ionic bonds, causing the tertiary structure to change and therefore the active, decreasing the rate of reaction
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What does increasing the enzyme concentration do?
Makes it more likely for a substrate and an enzyme to collide and for an enzyme-substrate complex, therefore increases the rate of reaction, but only up to a certain point as if there's a limited amount of substrate
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What's the saturation point?
When adding more substrate doesn't make a difference, as all the active sites are taken up
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2 ways to measure the rate of an enzyme controlled reaction?
Measure how fast the product of the reaction appears, eg in the reaction of catalase on hydrogen peroxide, measure how much Oxygen is produced in an upside down cylinder in water Can measure the disappearance of substrate, eg the enzyme amylase catalyses the reaction of starch to maltose, so during the reaction can keep adding sample to pottasium iodide and iodine solution, untill it doesn't go blue/black, then you know all starch has disappeared.
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What's a cofactor?
Non protein substance, that attaches to an enzyme allowing it to work
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Example of a inorganic cofactor?
Chloride ion, helps amylase enzyme bind to starch Aren't affected during the reaction
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What can an organic cofactor be known as?
Coenzymes, usually are sources from vitamins
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What do coenzymes do during a reaction?
They participate in the reaction, so are changed Often act as carries, moving chemical groups between different enzymes
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What's a cofactor known as if it's tightly bound to an enzyme, and an example?
Prosthetic group, eg Zn(2+) in cabonic anhydrase (which catalyses the production of carbonic acid, from water and CO2)
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Explain what a competitive inhibitor is and how it works?
They are molecules that have similar shape to that of substrate molecules They compete with the substrate molecules to bind to the active site, but no reaction takes place, so they block the place for the substrate to react
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Explain what a non competitive inhibitor is and how it works?
Molecules that bind to the enzyme at the alosteric site Causes the active site to change the shape so the substrate molecules can no longer bind to it
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What makes an inhibitor reversible or non reversible?
Reversible if they're bonded via weaker bonds such as hydrogen bonds Irreversible if they are bonded via strong hydrogen bonds
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Examples of enzyme inhibitors?
Some drugs, and metabolic poisions
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How are metabolic pathways regulated by end-product inhibition?
Metabollic pathway is a series of connected metabolic reactions, so the product of the first reaction takes part in the second reaction, each reaction is catalysed by a different enzyme Many enzymes are inhibited by the product of the reaction they catalyse, this is known as product inhibition End product inhibition is when the final product of the metabolic pathway, inhibits an enzyme which acts earlier on in the pathway So when there's too much of final product will inhibit an earlier enzyme more, preventing too much being made
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Why are some enzymes sometimes synthesised as inactive precursor enzymes?
So they don't damage the cells they are synthesised in
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Functions of membranes at the surface of cells (plasma membranes)?
They are barriers between the cell and the environment They're partially permeable and control what substances enter and leave the cell They allow recognition by other cells They allow cell communication
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Functions of membranes within cells?
Compartmentalises organelles, acting as a barrier between the organelle and cytoplasm Can form vesicles to transport substances between different areas of the cell They control which substances enter, and leave the organelle Can be the site of a chemical reaction
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What are cell membranes made up of?
Lipids (mainly phospholipids) Proteins Carbohydrates (usually attached to proteins or lipids)
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Describe the basic structure of a cell membrane?
Phospholipid molecules form a continuous double layer (bilayer) Bilayer is fluid as phopholipids are continuously moving Cholesterol molecules are present in the bilayer Proteins scattered thoughout the bilayer (like tiles) Some proteins have carbohydrates attached = glycoproten Some lipids also have a polysaccharide chain attached = glycolipid
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How do phopholipids form a barrier to dissolved substances?
They have a head and a tail, the head is hydrophillic (attracts water) and the tail is hydrophobic (repels water) They arrange themselves in a bilayer, heads on outside, tails on the inside The centre of the bilayer is hydrophobic, so the membrane doesn't allow water-soluble substances through it, however does allow fat-soluble substances through
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What cholesterol do to the membrane?
Fits between the phospholipids, and bind to the hydrophobic tails, causing them to pack more closely
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What do proteins do in the membrane generally?
Control what leaves and enters, and act as receptors
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What glycolipids and glycoproteins do in the membrane generally?
Act as receptors for messenger molecules
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Explain the general process of cell signalling?
One cell releases a messenger molecule, (eg a hormone) This molecule travels to another cell The messenger molecule is detected by the cell as it binds to a receptor on it's cell membrane, the receptors will be complementary to the molecule
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What is glucagon?
A hormone that's released when there isn't enough glucose in the blood, it binds to receptors on liver cells, causing the liver to breakdown stores of glycogen to glucose
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Describe a drug that binds to cell receptors?
Cell damage causes the release of histamine, which binds to receptors of other cells and causes inflamation. Antihistamine binds to there receptor cells and blocks histamine binding and causing inflamation
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How can membrane permeability be investigated?
Using beetroot cell that contain a coloured pigment that leaks out, the more permeable it is the more pigment will leak out. Leave in solution of water, then measure the solution produced with a calorimeter, so the higher the absorbance, the more permeable it is
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Affect of increasing temperature on the cell membrane?
Temperature bellow 0 degrees: Very little energy, so phospholipids packed together very tightly and membrane is rigid. But channel proteins and carrier proteins may deform, increasing the permeability. Ice crystals may form and pierce the membrane, making it highly permeable when it thaws Temperature between 0 and 45 degrees: The phospholipids can move around and aren't as tightly packed, so the membrane is partially permeable, so as temperature increases they move around more and become more permeable Temperature above 45 degrees: The phospholipid bilayer starts to melt (break down) and the membrane becomes more permeable Water inside the cell expands putting pressure on the membrane Channel proteins and carrier proteins deform so they can't control what enters or leaves the cell, making it even more permeable
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How do solvents affect the cell membrane?
Increases the permeability as the solvent dissolves the lipids in the cell membrane, so it loses structure
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What's diffusion?
The net movement of particles from an area of high concentration to an area of low concentration No ATP is required, it is a passive process
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What type of molecules can diffuse through the cell membrane?
Small, non polar molecules such as Oxygen and Carbon Dioxide, as can fit in between spaces between phospholipids Water also can because it's small enough, even though it's polar
167
4 factors the rate of diffusion depends upon?
The concentration gradient, the higher it is the faster the rate of diffusion The thickness of the exchange surface, the thinner it is the faster the rate The surface area, the larger the surface area the faster the rate The temperature- higher the temp the faster it is as particles have more kinetic energy so move faster
168
How can you investigate diffusion in model cells?
Make up some agar jelly, with phenolphthalein (pH indicator which is pink in alkaline conditions, and colourless in acidic conditions), and sodium hydroxide, so the jelly will be a shade of pink Put the agar cubes into dilute hydrochloric acid, and time how long it takes for the HCl to diffuse into the agar cube neutralising it and making it colourless Can use this to investigate surface area, concentration gradient, and temperature
169
What's facillitated diffusion?
When larger molecules, Ions and polar molecules don't diffuse directly through the phospholipid bilayer, so they diffuse through carrier proteins or channel proteins Moves particles down a concentration gradient, and doesn't require ATP
170
How do carrier proteins move large molecules into or out of a cell?
A large molecule attaches to a carrier protein in the membrane The protein then changes shape This releases the molecule on the opposite side of the membrane
171
What do carrier proteins do?
Form pores in the membrane for specific charged particles to diffuse through
172
Describe the process of active transport?
A molecule attaches to a carrier protein, causing it to change shape and allow the molecule across, requires ATP and moves particles from low concentration to a high concentration
173
Describe cells taking substances in by endocytosis?
Some substances to large to be taken into a cell by carrier proteins So the cell surrounds the substance with a section of it's plasma membrane, the membrane then pinches off to form a vesicle inside cell containing the ingested substance = endocytosis Process uses ATP for energy
174
Describe cells secreting substances by exocytosis?
Vesicles containing the substances pinch off from the sacs of the golgi apparatus and move towards the plasma membrane They then fuse with the plasma membrane and release their contents outside the cell Uses ATP as an energy source
175
What is osmosis?
The diffusion of water molecules across a partially permeable membrane down a water potential gradient.
176
What is water potential?
The likelihood of water molecules to diffuse out of or into a solution Pure water has the highest water potential of 0
177
What happens to an animal cell if it's in a solution where the water potential outside is higher, the same or lower?
Higher: Net movement of water into the cells causing them to burst The same: water molecules pass into and out of the cell in equal amounts, so the cell stays the same Lower: net movement is out of the cell, the cell shrinks
178
What happens to an plant cell if it's in a solution where the water potential outside is higher, the same or lower?
Higher: Net movement of water is into the cell. The vacuole swells, the vacuole and cytoplasm push against the cell wall, making the cell turgid The same: Water molecules move into and out of the cell, in equal amounts. The cell stays the same. Lower: Net movement of water is out of the cell, the cell becomes flaccid. The cytoplasm and the membrane pull away from the cell wall. This is called plasmolysis
179
Experiment to investigate water potential?
Prepare different sucrose concentration solutions Weigh potato chips and one in each oconcentration for 20 minutes Measure the percentage mass change, and plot it against concentration of sucrose solution on the x axis The place where they have equal water potentials is where line crosses x axis (works with eggs that have their shells dissolved aswell
180
Experiment to investigate water potential?
Prepare different sucrose concentration solutions Weigh potato chips and one in each oconcentration for 20 minutes Measure the percentage mass change, and plot it against concentration of sucrose solution on the x axis The place where they have equal water potentials is where line crosses x axis (works with eggs that have their shells dissolved aswell
181
What happens to an plant cell if it's in a solution where the water potential outside is higher, the same or lower?
Higher: Net movement of water is into the cell. The vacuole swells, the vacuole and cytoplasm push against the cell wall, making the cell turgid The same: Water molecules move into and out of the cell, in equal amounts. The cell stays the same. Lower: Net movement of water is out of the cell, the cell becomes flaccid. The cytoplasm and the membrane pull away from the cell wall. This is called plasmolysis
182
What happens to an animal cell if it's in a solution where the water potential outside is higher, the same or lower?
Higher: Net movement of water into the cells causing them to burst The same: water molecules pass into and out of the cell in equal amounts, so the cell stays the same Lower: net movement is out of the cell, the cell shrinks
183
What is water potential?
The likelihood of water molecules to diffuse out of or into a solution Pure water has the highest water potential of 0
184
What is osmosis?
The diffusion of water molecules across a partially permeable membrane down a water potential gradient.
185
Describe cells secreting substances by exocytosis?
Vesicles containing the substances pinch off from the sacs of the golgi apparatus and move towards the plasma membrane They then fuse with the plasma membrane and release their contents outside the cell Uses ATP as an energy source
186
Describe cells taking substances in by endocytosis?
Some substances to large to be taken into a cell by carrier proteins So the cell surrounds the substance with a section of it's plasma membrane, the membrane then pinches off to form a vesicle inside cell containing the ingested substance = endocytosis Process uses ATP for energy
187
Describe the process of active transport?
A molecule attaches to a carrier protein, causing it to change shape and allow the molecule across, requires ATP and moves particles from low concentration to a high concentration
188
What do carrier proteins do?
Form pores in the membrane for specific charged particles to diffuse through
189
How do carrier proteins move large molecules into or out of a cell?
A large molecule attaches to a carrier protein in the membrane The protein then changes shape This releases the molecule on the opposite side of the membrane
190
What's facillitated diffusion?
When larger molecules, Ions and polar molecules don't diffuse directly through the phospholipid bilayer, so they diffuse through carrier proteins or channel proteins Moves particles down a concentration gradient, and doesn't require ATP
191
How can you investigate diffusion in model cells?
Make up some agar jelly, with phenolphthalein (pH indicator which is pink in alkaline conditions, and colourless in acidic conditions), and sodium hydroxide, so the jelly will be a shade of pink Put the agar cubes into dilute hydrochloric acid, and time how long it takes for the HCl to diffuse into the agar cube neutralising it and making it colourless Can use this to investigate surface area, concentration gradient, and temperature
192
4 factors the rate of diffusion depends upon?
The concentration gradient, the higher it is the faster the rate of diffusion The thickness of the exchange surface, the thinner it is the faster the rate The surface area, the larger the surface area the faster the rate The temperature- higher the temp the faster it is as particles have more kinetic energy so move faster
193
What type of molecules can diffuse through the cell membrane?
Small, non polar molecules such as Oxygen and Carbon Dioxide, as can fit in between spaces between phospholipids Water also can because it's small enough, even though it's polar
194
What's diffusion?
The net movement of particles from an area of high concentration to an area of low concentration No ATP is required, it is a passive process
195
How do solvents affect the cell membrane?
Increases the permeability as the solvent dissolves the lipids in the cell membrane, so it loses structure
196
Affect of increasing temperature on the cell membrane?
Temperature bellow 0 degrees: Very little energy, so phospholipids packed together very tightly and membrane is rigid. But channel proteins and carrier proteins may deform, increasing the permeability. Ice crystals may form and pierce the membrane, making it highly permeable when it thaws Temperature between 0 and 45 degrees: The phospholipids can move around and aren't as tightly packed, so the membrane is partially permeable, so as temperature increases they move around more and become more permeable Temperature above 45 degrees: The phospholipid bilayer starts to melt (break down) and the membrane becomes more permeable Water inside the cell expands putting pressure on the membrane Channel proteins and carrier proteins deform so they can't control what enters or leaves the cell, making it even more permeable
197
How can membrane permeability be investigated?
Using beetroot cell that contain a coloured pigment that leaks out, the more permeable it is the more pigment will leak out. Leave in solution of water, then measure the solution produced with a calorimeter, so the higher the absorbance, the more permeable it is
198
Describe a drug that binds to cell receptors?
Cell damage causes the release of histamine, which binds to receptors of other cells and causes inflamation. Antihistamine binds to there receptor cells and blocks histamine binding and causing inflamation
199
What is glucagon?
A hormone that's released when there isn't enough glucose in the blood, it binds to receptors on liver cells, causing the liver to breakdown stores of glycogen to glucose
200
Explain the general process of cell signalling?
One cell releases a messenger molecule, (eg a hormone) This molecule travels to another cell The messenger molecule is detected by the cell as it binds to a receptor on it's cell membrane, the receptors will be complementary to the molecule
201
What glycolipids and glycoproteins do in the membrane generally?
Act as receptors for messenger molecules
202
What do proteins do in the membrane generally?
Control what leaves and enters, and act as receptors
203
What cholesterol do to the membrane?
Fits between the phospholipids, and bind to the hydrophobic tails, causing them to pack more closely
204
How do phopholipids form a barrier to dissolved substances?
They have a head and a tail, the head is hydrophillic (attracts water) and the tail is hydrophobic (repels water) They arrange themselves in a bilayer, heads on outside, tails on the inside The centre of the bilayer is hydrophobic, so the membrane doesn't allow water-soluble substances through it, however does allow fat-soluble substances through
205
Describe the basic structure of a cell membrane?
Phospholipid molecules form a continuous double layer (bilayer) Bilayer is fluid as phopholipids are continuously moving Cholesterol molecules are present in the bilayer Proteins scattered thoughout the bilayer (like tiles) Some proteins have carbohydrates attached = glycoproten Some lipids also have a polysaccharide chain attached = glycolipid
206
What are cell membranes made up of?
Lipids (mainly phospholipids) Proteins Carbohydrates (usually attached to proteins or lipids)
207
Functions of membranes within cells?
Compartmentalises organelles, acting as a barrier between the organelle and cytoplasm Can form vesicles to transport substances between different areas of the cell They control which substances enter, and leave the organelle Can be the site of a chemical reaction
208
Functions of membranes at the surface of cells (plasma membranes)?
They are barriers between the cell and the environment They're partially permeable and control what substances enter and leave the cell They allow recognition by other cells They allow cell communication
209
Describe the cell cycle briefly?
Order: Cell division: M phase- cell division and cytokenesis Interphase: cell growth and reproduction G1 G1 checkpoint S G2 checkpoint
210
What occurs at G1 checkpoint and G2 checkpoint?
G1 checkpoint: Cell checks that the chemicals required for replication are present, and for any DNA damage before entering the s Phase G2 checkpoint: The cell checks if all the DNA has been replicated without damage, to see if it can enter the M phase
211
The 6 steps in cell division?
Interphase Prophase (Mitosis) Metaphase (Mitosis) Anaphase (Mitosis) Telophase (Mitosis) Cytokenesis
212
What occurs during interphase?
The cell carries out normal functions, but also prepares to divide Cell's DNA is replicated, to double it's genetic content, the organelles are also replicated so it has spare ones ATP content is increased (provides energy for cell division)
213
What's a chromosome, a chromatid, sister chromatids, homologous pairs and a centromere?
A chromosome is half the X before replication in interphase, and is the whole X shape after replication A chromatid is the part of the X which would be there before replication SIster chromatids, and the bottom or top 2 parts of the X paired up Homologous pairs are when there's 1 chromosome from the mum and 1 from the dad, they have the same genes in the same order, but will have different allels Centromere joins the 2 strands of the chromosome in the middle
214
Describe what occurs in the first step of mitosis, prophase?
Chromosomes condense Centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called spindle Nuclear envelope breaks down and chromosomes lie free in the cytoplasm
215
What occurs in the second step of mitosis, metaphase?
The chromosomes line up along the middle of the cell (laying sideways), and become attached to the spindle by their centromers Metaphase checkpoint, checks to see that all chromosomes are attached to the spindle before it can continue
216
What occurs in anaphase, the 3rd of mitosis?
Centromers divide Separating each pair of sister chromatids, the spindles contract pulling the chromatids to the opposite ends of the cell
217
What occurs in telophase, the 4th step of mitosis?
The chromatids reach the opposite poles of the spindle, and uncoil becoming long and thin again, so they're now called chromosomes again A nuclear envelope forms around each group of chromosomes so there are now 2 nuclei Cytokenesis occurs next 9 (not part of mitosis)
218
Describe cytokenesis?
The cytoplasm divides, a cleavage furrow forms to divide the cell membrane Produces 2 daughter cells which are genetically identical to each other and the original cell
219
Uses of mitosis?
Need for growth of multicellular organisms Repairing damaged tissue Method of asexual reproduction
220
What occurs in sexual reproduction?
2 gametes (an egg and a sperm), join together at fertilisation to form a zygote
221
Where does meiosis occur?
Occurs in sexual reproductive organs to produce gametes
222
What's a gamete and what type of cell are they?
Produced in sexual reproductive organs, and contain half the amount of chromosomes of a normal cell, so they are haploid cells, and are all gentically different to each other as contain different combinations of chromosomes
223
How many chromosomes do human cells have?
46, so 23 homologous pairs
224
What are the steps in meiosis?
Interphase (DNA replicated) Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Cytokenesis Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Cytokenesis
225
What occurs in prophase 1, the first step of meiosis?
(DNA has already been replicated in interphase) Chromosomes condense, and arrange themselves into homologous pairs Crossing over occurs Centrioles start moving to opposite ends of the cells, forming the spindle fibres Nuclear envelope breaks down
226
What occurs in metaphase 1, the second step of meiosis?
The homologous pairs line up across the centre of the cell, and attach to the spindle fibres by their centromers
227
What happens in anaphase 1, the third step of meiosis?
The spindles contract, separating the homologous pairs, one chromosome goes to each end of the cell
228
What occurs in telophase 1, the 4th step of meiosis?
Nuclear envelope forms around each group of chromosomes, and then cytokinesis occurs and 2 haploid daughter cells are produced (still double stranded)
229
What happens in meiosis 2?
All the same steps as mitosis Produces 4 genetically different haploid daughter cells (single stranded chromosomes) = gametes
230
Describe chromatids crossing over in Prophase 1?
Homologous pairs have come together and pair up, the chromatids twist around each other, and bits of chromatids swap over The chromosomes still contain the same genes, but have different alleles
231
2 ways meiosis creates cells which are genetically different?
Crossing over if the chromatids Independent assortment of chromosomes
232
Describe the independent assortment of chromosomes?
Each homologous pair of chromosomes in your cells is made up of one chromosome from your mum (maternal), and one from your dad (paternal) When the homologous pairs line up in metaphase 1, and are separated in anaphase 1, it's random which chromosome from each pair ends up in which daughter cell So all 4 daughter cells have different combinations of maternal and paternal chromosomes
233
What are stem cells?
Unspecialised cells, that can develop into different types of cells
234
Where are stem cells most commonly found?
In human embryos
235
What's the process of a stem cell dividing to become a new cell which then becomes specialised?
Differentiation
236
What do adult stem cells in the bone marrow differentiate into?
They divide and differentiate to replace worn out erythrocytes (red blood cells) and Nuetrophils (white blood cells)
237
In plants what do the stem cells in the meristems differentiate into?
Xylem vessels and phloem sieve tubes
238
Why could stem cells be used to cure nuerone disorders such as Alzheimers and parkinsons?
In Alzheimers nerve cells in the brain die in increasing numbers, resulting in memory loss. Stem cells could be used to regrow healthy nerve cells In parkinsons loss of nerve cell which produces dopamine for movement, can regrow these with nerve cells
239
How are nuetrophils (type of white blood cell) adapted to perform their function?
Their flexible shape allows, them to ingest foreign particles or pathogens. The lysosomes in their cytoplasm contain digestive enzymes to break down the engulfed particles
240
How are erythrocytes adapted to perform their function?
The bioconcave disc shape provides a large surface area for gas exchange They have no nucleus, so there's more for haemoglobin
241
How are epithelial cells (cover the surfaces of organs) adapted to perform their function?
CIliated epithial cells (in the air ways) have cilia that beat to move particles away Squamous epithelial cells (in the lungs) are very thin to allow efficent diffusion of gases
242
How are sperm cells adapted to perform their function?
Have a flagellum so they can swim to the egg Have lots of mitochondrion to provide energy to swim The acrosome (head) contains digestive enzymes, that enable the sperm to penetrate the surface of the egg
243
How are palisade mesophyll cells in leaves adapted to perform their function?
They do most of the photosynthesis, so they contain many chloroplasts, so can absorb a lot of sunlight The walls are thin, so CO2 can easily into the cell
244
How are root hair cells adapted to their perform their function?
Absorb mineral ions from the soil, so have a large surface area for absorption, and a thin permeable cell wall for entry of water and ions The cytoplasm contains extra mitochondria to provide the energy required for active transport
245
How are guard cells adapted to perform their function?
Found in pairs with a gap between them to form a stoma, which is a tiny pore in the surface of the leaf used for gas exchange In the light, guard cells take up water and become turgid, forcing them open, and allowing gas exchange for photosynthesis
246
What's a tissue?
A group of cells that are specialised to work together to perform a particular function
247
What does the tissue squamous epithelium do?
A single layer of flat cells lining a surface, found in the alveoli of the lungs
248
What does the tissue ciliated epithelium do?
Layer of cells covered in cilia, it's found on the surfaces where things need to be moved, eg in the trachea to move mucus
249
What do muscle tissues do and what does it consist of?
Made up of muscle fibres, there are 3 types of muscle tissue, smooth (found in lining of stomach wall), cardiac (found in heart), and skeletal which is used to move
250
What does the tissue cartilage do?
Type of connective tissue found in the joints Formed when cells called chondrolasts secrete an extracellular matrix in which they become trapped in
251
What does xylem tissue do?
Transports water around the plant Supports the plant Contains dead hollow xylem vessel cells and living parenchyma cells
252
What's an organ?
Group of different tissues that work together to perform a particular function Eg. the lungs and leaves
253
What's an organ system?
Organs working together to perform a particular function, eg. respiratory system or circulatory system
254
What does phloem tissue do?
Transports sugars around the plant, arranged in tubes made up of sieve tube elements and companion cells
255
What occurs at G1 checkpoint and G2 checkpoint?
G1 checkpoint: Cell checks that the chemicals required for replication are present, and for any DNA damage before entering the s Phase G2 checkpoint: The cell checks if all the DNA has been replicated without damage, to see if it can enter the M phase
256
The 6 steps in cell division?
Interphase Prophase (Mitosis) Metaphase (Mitosis) Anaphase (Mitosis) Telophase (Mitosis) Cytokenesis
257
What occurs during interphase?
The cell carries out normal functions, but also prepares to divide Cell's DNA is replicated, to double it's genetic content, the organelles are also replicated so it has spare ones ATP content is increased (provides energy for cell division)
258
What's a chromosome, a chromatid, sister chromatids, homologous pairs and a centromere?
A chromosome is half the X before replication in interphase, and is the whole X shape after replication A chromatid is the part of the X which would be there before replication SIster chromatids, and the bottom or top 2 parts of the X paired up Homologous pairs are when there's 1 chromosome from the mum and 1 from the dad, they have the same genes in the same order, but will have different allels Centromere joins the 2 strands of the chromosome in the middle
259
Describe what occurs in the first step of mitosis, prophase?
Chromosomes condense Centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called spindle Nuclear envelope breaks down and chromosomes lie free in the cytoplasm
260
What occurs in the second step of mitosis, metaphase?
The chromosomes line up along the middle of the cell (laying sideways), and become attached to the spindle by their centromers Metaphase checkpoint, checks to see that all chromosomes are attached to the spindle before it can continue
261
What occurs in anaphase, the 3rd of mitosis?
Centromers divide Separating each pair of sister chromatids, the spindles contract pulling the chromatids to the opposite ends of the cell
262
What occurs in telophase, the 4th step of mitosis?
The chromatids reach the opposite poles of the spindle, and uncoil becoming long and thin again, so they're now called chromosomes again A nuclear envelope forms around each group of chromosomes so there are now 2 nuclei Cytokenesis occurs next 9 (not part of mitosis)
263
Describe cytokenesis?
The cytoplasm divides, a cleavage furrow forms to divide the cell membrane Produces 2 daughter cells which are genetically identical to each other and the original cell
264
Uses of mitosis?
Need for growth of multicellular organisms Repairing damaged tissue Method of asexual reproduction
265
What occurs in sexual reproduction?
2 gametes (an egg and a sperm), join together at fertilisation to form a zygote
266
Where does meiosis occur?
Occurs in sexual reproductive organs to produce gametes
267
What's a gamete and what type of cell are they?
Produced in sexual reproductive organs, and contain half the amount of chromosomes of a normal cell, so they are haploid cells, and are all gentically different to each other as contain different combinations of chromosomes
268
How many chromosomes do human cells have?
46, so 23 homologous pairs
269
What are the steps in meiosis?
Interphase (DNA replicated) Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Cytokenesis Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Cytokenesis
270
What occurs in prophase 1, the first step of meiosis?
(DNA has already been replicated in interphase) Chromosomes condense, and arrange themselves into homologous pairs Crossing over occurs Centrioles start moving to opposite ends of the cells, forming the spindle fibres Nuclear envelope breaks down
271
What occurs in metaphase 1, the second step of meiosis?
The homologous pairs line up across the centre of the cell, and attach to the spindle fibres by their centromers
272
What happens in anaphase 1, the third step of meiosis?
The spindles contract, separating the homologous pairs, one chromosome goes to each end of the cell
273
What occurs in telophase 1, the 4th step of meiosis?
Nuclear envelope forms around each group of chromosomes, and then cytokinesis occurs and 2 haploid daughter cells are produced (still double stranded)
274
What happens in meiosis 2?
All the same steps as mitosis Produces 4 genetically different haploid daughter cells (single stranded chromosomes) = gametes
275
Describe chromatids crossing over in Prophase 1?
Homologous pairs have come together and pair up, the chromatids twist around each other, and bits of chromatids swap over The chromosomes still contain the same genes, but have different alleles
276
2 ways meiosis creates cells which are genetically different?
Crossing over if the chromatids Independent assortment of chromosomes
277
Describe the independent assortment of chromosomes?
Each homologous pair of chromosomes in your cells is made up of one chromosome from your mum (maternal), and one from your dad (paternal) When the homologous pairs line up in metaphase 1, and are separated in anaphase 1, it's random which chromosome from each pair ends up in which daughter cell So all 4 daughter cells have different combinations of maternal and paternal chromosomes
278
What are stem cells?
Unspecialised cells, that can develop into different types of cells
279
Where are stem cells most commonly found?
In human embryos
280
What's the process of a stem cell dividing to become a new cell which then becomes specialised?
Differentiation
281
What do adult stem cells in the bone marrow differentiate into?
They divide and differentiate to replace worn out erythrocytes (red blood cells) and Nuetrophils (white blood cells)
282
In plants what do the stem cells in the meristems differentiate into?
Xylem vessels and phloem sieve tubes
283
Why could stem cells be used to cure nuerone disorders such as Alzheimers and parkinsons?
In Alzheimers nerve cells in the brain die in increasing numbers, resulting in memory loss. Stem cells could be used to regrow healthy nerve cells In parkinsons loss of nerve cell which produces dopamine for movement, can regrow these with nerve cells
284
How are nuetrophils (type of white blood cell) adapted to perform their function?
Their flexible shape allows, them to ingest foreign particles or pathogens. The lysosomes in their cytoplasm contain digestive enzymes to break down the engulfed particles
285
How are erythrocytes adapted to perform their function?
The bioconcave disc shape provides a large surface area for gas exchange They have no nucleus, so there's more for haemoglobin
286
How are epithelial cells (cover the surfaces of organs) adapted to perform their function?
CIliated epithial cells (in the air ways) have cilia that beat to move particles away Squamous epithelial cells (in the lungs) are very thin to allow efficent diffusion of gases
287
How are sperm cells adapted to perform their function?
Have a flagellum so they can swim to the egg Have lots of mitochondrion to provide energy to swim The acrosome (head) contains digestive enzymes, that enable the sperm to penetrate the surface of the egg
288
How are palisade mesophyll cells in leaves adapted to perform their function?
They do most of the photosynthesis, so they contain many chloroplasts, so can absorb a lot of sunlight The walls are thin, so CO2 can easily into the cell
289
How are root hair cells adapted to their perform their function?
Absorb mineral ions from the soil, so have a large surface area for absorption, and a thin permeable cell wall for entry of water and ions The cytoplasm contains extra mitochondria to provide the energy required for active transport
290
How are guard cells adapted to perform their function?
Found in pairs with a gap between them to form a stoma, which is a tiny pore in the surface of the leaf used for gas exchange In the light, guard cells take up water and become turgid, forcing them open, and allowing gas exchange for photosynthesis
291
What's a tissue?
A group of cells that are specialised to work together to perform a particular function
292
What does the tissue squamous epithelium do?
A single layer of flat cells lining a surface, found in the alveoli of the lungs
293
What does the tissue ciliated epithelium do?
Layer of cells covered in cilia, it's found on the surfaces where things need to be moved, eg in the trachea to move mucus
294
What does phloem tissue do?
Transports sugars around the plant, arranged in tubes made up of sieve tube elements and companion cells
295
What's an organ system?
Organs working together to perform a particular function, eg. respiratory system or circulatory system
296
What's an organ?
Group of different tissues that work together to perform a particular function Eg. the lungs and leaves
297
What does xylem tissue do?
Transports water around the plant Supports the plant Contains dead hollow xylem vessel cells and living parenchyma cells
298
What does the tissue cartilage do?
Type of connective tissue found in the joints Formed when cells called chondrolasts secrete an extracellular matrix in which they become trapped in
299
What do muscle tissues do and what does it consist of?
Made up of muscle fibres, there are 3 types of muscle tissue, smooth (found in lining of stomach wall), cardiac (found in heart), and skeletal which is used to move
300
Describe the cell cycle briefly?
Order: Cell division: M phase- cell division and cytokenesis Interphase: cell growth and reproduction G1 G1 checkpoint S G2 checkpoint
301
What occurs at G1 checkpoint and G2 checkpoint?
G1 checkpoint: Cell checks that the chemicals required for replication are present, and for any DNA damage before entering the s Phase G2 checkpoint: The cell checks if all the DNA has been replicated without damage, to see if it can enter the M phase
302
The 6 steps in cell division?
Interphase Prophase (Mitosis) Metaphase (Mitosis) Anaphase (Mitosis) Telophase (Mitosis) Cytokenesis
303
What occurs during interphase?
The cell carries out normal functions, but also prepares to divide Cell's DNA is replicated, to double it's genetic content, the organelles are also replicated so it has spare ones ATP content is increased (provides energy for cell division)
304
What's a chromosome, a chromatid, sister chromatids, homologous pairs and a centromere?
A chromosome is half the X before replication in interphase, and is the whole X shape after replication A chromatid is the part of the X which would be there before replication SIster chromatids, and the bottom or top 2 parts of the X paired up Homologous pairs are when there's 1 chromosome from the mum and 1 from the dad, they have the same genes in the same order, but will have different allels Centromere joins the 2 strands of the chromosome in the middle
305
Describe what occurs in the first step of mitosis, prophase?
Chromosomes condense Centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called spindle Nuclear envelope breaks down and chromosomes lie free in the cytoplasm
306
What occurs in the second step of mitosis, metaphase?
The chromosomes line up along the middle of the cell (laying sideways), and become attached to the spindle by their centromers Metaphase checkpoint, checks to see that all chromosomes are attached to the spindle before it can continue
307
What occurs in anaphase, the 3rd of mitosis?
Centromers divide Separating each pair of sister chromatids, the spindles contract pulling the chromatids to the opposite ends of the cell
308
What occurs in telophase, the 4th step of mitosis?
The chromatids reach the opposite poles of the spindle, and uncoil becoming long and thin again, so they're now called chromosomes again A nuclear envelope forms around each group of chromosomes so there are now 2 nuclei Cytokenesis occurs next 9 (not part of mitosis)
309
What does phloem tissue do?
Transports sugars around the plant, arranged in tubes made up of sieve tube elements and companion cells
310
What's an organ system?
Organs working together to perform a particular function, eg. respiratory system or circulatory system
311
What's an organ?
Group of different tissues that work together to perform a particular function Eg. the lungs and leaves
312
What does xylem tissue do?
Transports water around the plant Supports the plant Contains dead hollow xylem vessel cells and living parenchyma cells
313
What does the tissue cartilage do?
Type of connective tissue found in the joints Formed when cells called chondrolasts secrete an extracellular matrix in which they become trapped in
314
What do muscle tissues do and what does it consist of?
Made up of muscle fibres, there are 3 types of muscle tissue, smooth (found in lining of stomach wall), cardiac (found in heart), and skeletal which is used to move
315
What does the tissue ciliated epithelium do?
Layer of cells covered in cilia, it's found on the surfaces where things need to be moved, eg in the trachea to move mucus
316
What does the tissue squamous epithelium do?
A single layer of flat cells lining a surface, found in the alveoli of the lungs
317
What's a tissue?
A group of cells that are specialised to work together to perform a particular function
318
How are guard cells adapted to perform their function?
Found in pairs with a gap between them to form a stoma, which is a tiny pore in the surface of the leaf used for gas exchange In the light, guard cells take up water and become turgid, forcing them open, and allowing gas exchange for photosynthesis
319
How are root hair cells adapted to their perform their function?
Absorb mineral ions from the soil, so have a large surface area for absorption, and a thin permeable cell wall for entry of water and ions The cytoplasm contains extra mitochondria to provide the energy required for active transport
320
How are palisade mesophyll cells in leaves adapted to perform their function?
They do most of the photosynthesis, so they contain many chloroplasts, so can absorb a lot of sunlight The walls are thin, so CO2 can easily into the cell
321
How are sperm cells adapted to perform their function?
Have a flagellum so they can swim to the egg Have lots of mitochondrion to provide energy to swim The acrosome (head) contains digestive enzymes, that enable the sperm to penetrate the surface of the egg
322
How are epithelial cells (cover the surfaces of organs) adapted to perform their function?
CIliated epithial cells (in the air ways) have cilia that beat to move particles away Squamous epithelial cells (in the lungs) are very thin to allow efficent diffusion of gases
323
How are erythrocytes adapted to perform their function?
The bioconcave disc shape provides a large surface area for gas exchange They have no nucleus, so there's more for haemoglobin
324
How are nuetrophils (type of white blood cell) adapted to perform their function?
Their flexible shape allows, them to ingest foreign particles or pathogens. The lysosomes in their cytoplasm contain digestive enzymes to break down the engulfed particles
325
Why could stem cells be used to cure nuerone disorders such as Alzheimers and parkinsons?
In Alzheimers nerve cells in the brain die in increasing numbers, resulting in memory loss. Stem cells could be used to regrow healthy nerve cells In parkinsons loss of nerve cell which produces dopamine for movement, can regrow these with nerve cells
326
In plants what do the stem cells in the meristems differentiate into?
Xylem vessels and phloem sieve tubes
327
What do adult stem cells in the bone marrow differentiate into?
They divide and differentiate to replace worn out erythrocytes (red blood cells) and Nuetrophils (white blood cells)
328
What's the process of a stem cell dividing to become a new cell which then becomes specialised?
Differentiation
329
Describe cytokenesis?
The cytoplasm divides, a cleavage furrow forms to divide the cell membrane Produces 2 daughter cells which are genetically identical to each other and the original cell
330
Uses of mitosis?
Need for growth of multicellular organisms Repairing damaged tissue Method of asexual reproduction
331
What occurs in sexual reproduction?
2 gametes (an egg and a sperm), join together at fertilisation to form a zygote
332
Where does meiosis occur?
Occurs in sexual reproductive organs to produce gametes
333
What's a gamete and what type of cell are they?
Produced in sexual reproductive organs, and contain half the amount of chromosomes of a normal cell, so they are haploid cells, and are all gentically different to each other as contain different combinations of chromosomes
334
How many chromosomes do human cells have?
46, so 23 homologous pairs
335
What does phloem tissue do?
Transports sugars around the plant, arranged in tubes made up of sieve tube elements and companion cells
336
What's an organ system?
Organs working together to perform a particular function, eg. respiratory system or circulatory system
337
What's an organ?
Group of different tissues that work together to perform a particular function Eg. the lungs and leaves
338
What does xylem tissue do?
Transports water around the plant Supports the plant Contains dead hollow xylem vessel cells and living parenchyma cells
339
What does the tissue cartilage do?
Type of connective tissue found in the joints Formed when cells called chondrolasts secrete an extracellular matrix in which they become trapped in
340
What do muscle tissues do and what does it consist of?
Made up of muscle fibres, there are 3 types of muscle tissue, smooth (found in lining of stomach wall), cardiac (found in heart), and skeletal which is used to move
341
What does the tissue ciliated epithelium do?
Layer of cells covered in cilia, it's found on the surfaces where things need to be moved, eg in the trachea to move mucus
342
What does the tissue squamous epithelium do?
A single layer of flat cells lining a surface, found in the alveoli of the lungs
343
What's a tissue?
A group of cells that are specialised to work together to perform a particular function
344
How are guard cells adapted to perform their function?
Found in pairs with a gap between them to form a stoma, which is a tiny pore in the surface of the leaf used for gas exchange In the light, guard cells take up water and become turgid, forcing them open, and allowing gas exchange for photosynthesis
345
How are root hair cells adapted to their perform their function?
Absorb mineral ions from the soil, so have a large surface area for absorption, and a thin permeable cell wall for entry of water and ions The cytoplasm contains extra mitochondria to provide the energy required for active transport
346
How are palisade mesophyll cells in leaves adapted to perform their function?
They do most of the photosynthesis, so they contain many chloroplasts, so can absorb a lot of sunlight The walls are thin, so CO2 can easily into the cell
347
How are sperm cells adapted to perform their function?
Have a flagellum so they can swim to the egg Have lots of mitochondrion to provide energy to swim The acrosome (head) contains digestive enzymes, that enable the sperm to penetrate the surface of the egg
348
How are epithelial cells (cover the surfaces of organs) adapted to perform their function?
CIliated epithial cells (in the air ways) have cilia that beat to move particles away Squamous epithelial cells (in the lungs) are very thin to allow efficent diffusion of gases
349
How are erythrocytes adapted to perform their function?
The bioconcave disc shape provides a large surface area for gas exchange They have no nucleus, so there's more for haemoglobin
350
How are nuetrophils (type of white blood cell) adapted to perform their function?
Their flexible shape allows, them to ingest foreign particles or pathogens. The lysosomes in their cytoplasm contain digestive enzymes to break down the engulfed particles
351
Why could stem cells be used to cure nuerone disorders such as Alzheimers and parkinsons?
In Alzheimers nerve cells in the brain die in increasing numbers, resulting in memory loss. Stem cells could be used to regrow healthy nerve cells In parkinsons loss of nerve cell which produces dopamine for movement, can regrow these with nerve cells
352
In plants what do the stem cells in the meristems differentiate into?
Xylem vessels and phloem sieve tubes
353
What do adult stem cells in the bone marrow differentiate into?
They divide and differentiate to replace worn out erythrocytes (red blood cells) and Nuetrophils (white blood cells)
354
What's the process of a stem cell dividing to become a new cell which then becomes specialised?
Differentiation
355
Where are stem cells most commonly found?
In human embryos
356
What are stem cells?
Unspecialised cells, that can develop into different types of cells
357
Describe the independent assortment of chromosomes?
Each homologous pair of chromosomes in your cells is made up of one chromosome from your mum (maternal), and one from your dad (paternal) When the homologous pairs line up in metaphase 1, and are separated in anaphase 1, it's random which chromosome from each pair ends up in which daughter cell So all 4 daughter cells have different combinations of maternal and paternal chromosomes
358
2 ways meiosis creates cells which are genetically different?
Crossing over if the chromatids Independent assortment of chromosomes
359
Describe chromatids crossing over in Prophase 1?
Homologous pairs have come together and pair up, the chromatids twist around each other, and bits of chromatids swap over The chromosomes still contain the same genes, but have different alleles
360
What happens in meiosis 2?
All the same steps as mitosis Produces 4 genetically different haploid daughter cells (single stranded chromosomes) = gametes
361
What occurs in telophase 1, the 4th step of meiosis?
Nuclear envelope forms around each group of chromosomes, and then cytokinesis occurs and 2 haploid daughter cells are produced (still double stranded)
362
What happens in anaphase 1, the third step of meiosis?
The spindles contract, separating the homologous pairs, one chromosome goes to each end of the cell
363
What occurs in metaphase 1, the second step of meiosis?
The homologous pairs line up across the centre of the cell, and attach to the spindle fibres by their centromers
364
What occurs in prophase 1, the first step of meiosis?
(DNA has already been replicated in interphase) Chromosomes condense, and arrange themselves into homologous pairs Crossing over occurs Centrioles start moving to opposite ends of the cells, forming the spindle fibres Nuclear envelope breaks down
365
What are the steps in meiosis?
Interphase (DNA replicated) Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Cytokenesis Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Cytokenesis
366
Describe the cell cycle briefly?
Order: Cell division: M phase- cell division and cytokenesis Interphase: cell growth and reproduction G1 G1 checkpoint S G2 checkpoint
367
Where are stem cells most commonly found?
In human embryos
368
What are stem cells?
Unspecialised cells, that can develop into different types of cells
369
Describe the independent assortment of chromosomes?
Each homologous pair of chromosomes in your cells is made up of one chromosome from your mum (maternal), and one from your dad (paternal) When the homologous pairs line up in metaphase 1, and are separated in anaphase 1, it's random which chromosome from each pair ends up in which daughter cell So all 4 daughter cells have different combinations of maternal and paternal chromosomes
370
2 ways meiosis creates cells which are genetically different?
Crossing over if the chromatids Independent assortment of chromosomes
371
Describe chromatids crossing over in Prophase 1?
Homologous pairs have come together and pair up, the chromatids twist around each other, and bits of chromatids swap over The chromosomes still contain the same genes, but have different alleles
372
What happens in meiosis 2?
All the same steps as mitosis Produces 4 genetically different haploid daughter cells (single stranded chromosomes) = gametes
373
What occurs in telophase 1, the 4th step of meiosis?
Nuclear envelope forms around each group of chromosomes, and then cytokinesis occurs and 2 haploid daughter cells are produced (still double stranded)
374
What happens in anaphase 1, the third step of meiosis?
The spindles contract, separating the homologous pairs, one chromosome goes to each end of the cell
375
What occurs in metaphase 1, the second step of meiosis?
The homologous pairs line up across the centre of the cell, and attach to the spindle fibres by their centromers
376
What occurs in prophase 1, the first step of meiosis?
(DNA has already been replicated in interphase) Chromosomes condense, and arrange themselves into homologous pairs Crossing over occurs Centrioles start moving to opposite ends of the cells, forming the spindle fibres Nuclear envelope breaks down
377
What are the steps in meiosis?
Interphase (DNA replicated) Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Cytokenesis Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Cytokenesis
378
How many chromosomes do human cells have?
46, so 23 homologous pairs
379
What's a gamete and what type of cell are they?
Produced in sexual reproductive organs, and contain half the amount of chromosomes of a normal cell, so they are haploid cells, and are all gentically different to each other as contain different combinations of chromosomes
380
Where does meiosis occur?
Occurs in sexual reproductive organs to produce gametes
381
What occurs in sexual reproduction?
2 gametes (an egg and a sperm), join together at fertilisation to form a zygote
382
Uses of mitosis?
Need for growth of multicellular organisms Repairing damaged tissue Method of asexual reproduction
383
Describe cytokenesis?
The cytoplasm divides, a cleavage furrow forms to divide the cell membrane Produces 2 daughter cells which are genetically identical to each other and the original cell
384
What occurs in telophase, the 4th step of mitosis?
The chromatids reach the opposite poles of the spindle, and uncoil becoming long and thin again, so they're now called chromosomes again A nuclear envelope forms around each group of chromosomes so there are now 2 nuclei Cytokenesis occurs next 9 (not part of mitosis)
385
What occurs in anaphase, the 3rd of mitosis?
Centromers divide Separating each pair of sister chromatids, the spindles contract pulling the chromatids to the opposite ends of the cell
386
What occurs in the second step of mitosis, metaphase?
The chromosomes line up along the middle of the cell (laying sideways), and become attached to the spindle by their centromers Metaphase checkpoint, checks to see that all chromosomes are attached to the spindle before it can continue
387
Describe what occurs in the first step of mitosis, prophase?
Chromosomes condense Centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called spindle Nuclear envelope breaks down and chromosomes lie free in the cytoplasm
388
What's a chromosome, a chromatid, sister chromatids, homologous pairs and a centromere?
A chromosome is half the X before replication in interphase, and is the whole X shape after replication A chromatid is the part of the X which would be there before replication SIster chromatids, and the bottom or top 2 parts of the X paired up Homologous pairs are when there's 1 chromosome from the mum and 1 from the dad, they have the same genes in the same order, but will have different allels Centromere joins the 2 strands of the chromosome in the middle
389
What occurs during interphase?
The cell carries out normal functions, but also prepares to divide Cell's DNA is replicated, to double it's genetic content, the organelles are also replicated so it has spare ones ATP content is increased (provides energy for cell division)
390
The 6 steps in cell division?
Interphase Prophase (Mitosis) Metaphase (Mitosis) Anaphase (Mitosis) Telophase (Mitosis) Cytokenesis
391
What occurs at G1 checkpoint and G2 checkpoint?
G1 checkpoint: Cell checks that the chemicals required for replication are present, and for any DNA damage before entering the s Phase G2 checkpoint: The cell checks if all the DNA has been replicated without damage, to see if it can enter the M phase
392
Describe the cell cycle briefly?
Order: Cell division: M phase- cell division and cytokenesis Interphase: cell growth and reproduction G1 G1 checkpoint S G2 checkpoint
