Module 2 – Foundations in biology Flashcards
(240 cards)
1
Q
C2) How do you do gram stain technique
A
Used to separate bacteria into two groups: Gram-positive bacteria and Gram-negative bacteria
Crystal violet is first applied to a bacteria specimen on a slide, then iodine, which fixes the dye
The slide is washed with alcohol
Gram-positive bacteria retain the crystal violet stain and will appear blue or purple under a microscope
Gram-negative bacteria have thinner cell walls and therefore lose the stain. They are then staying with safranin dye,which is called a counterstain. These bacteria will then appear red
Gram-positive bacteria are susceptible to the antibiotic penicillin, which inhabits the formation of the cell walls
Gram-negative bacteria have much thinner cell walls is not susceptible to antibiotic pencilling
2
Q
C2) How do you do the acid-fast technique
A
Are used to differentiate between species of mycobacterium from other bacteria.
A liquid solution is used to carry carbolfuchsin dye into the cells being studied
The cells are washed with a die loot acid solution.
Mycobacteria are not affected by the I said alcohol and retain the stain- bright red
Are the bacteria lose the stain and are exposed to a methylene blue stain, which is blue
3
Q
C2) What are the features of a light microscope
1) expense
2) Radiation used
3) Size
4) Maximum magnification
5) Maximum resolution
6) Type of image produced
7) sample preparation
8) Vacuum needed?
A
1) not expensive
2) Light
3) Small and portable
4) x 1500
5) 200 nm
6) 2d
7) Sample procedure
8) No-can you live in specimen
4
Q
C2) What are the features of a scanning electron microscope
1) expense
2) Radiation used
3) Size
4) Maximum magnification
5) Maximum resolution
6) Type of image produced
7) Vacuum needed?
A
1) Expensive to buy and operate
2) Beam of electrons
3) Large
4) X 500,000
5) 2.2 nm
6) 3D
7) Yes-dead
5
Q
C2) What are the features of a transmission electron microscope
1) expense
2) Radiation used
3) Size
4) Maximum magnification
5) Maximum resolution
6) Type of image produced
7) Vacuum needed?
A
1) Expensive to buy and operate
2) Beam of electrons
3) Large
4) X 1,000,000
5) 0.1 nm
6) 2D
7) Yes-dead
6
Q
C2) What other parts of an animal cell
A
Cell-surface membrane
Cytosol
Ribosome
Centriole
Rough endoplasmic reticulin
Smooth endoplasmic reticulin am
Cytoskeleton
Secretion vesicles
Mitochondria
Golgi apparatus
Nucleus
Nucleolus
Golgi Vesicles
Microtubule network
7
Q
C2) What are the parts of an plant cell
A
Cell membrane
Cell wall
Ribosome
Rough endoplasmic reticulin
Smooth endoplasmic reticulin
Mitochondria
Golgi apparatus
Nucleus
Nucleolus
Golgi Vesicles
Chloroplast
Vacuole membrane
Raphide crystal
Druse Crystal
cytoplasm
Large central vacuole
Amyloplast (starch grain)
8
Q
C2) What are the structural components of cytoskeleton of a cell
A
MICROFILAMENTS – Fibres made from the protein Actin. They are responsible for movement of the cell and cytoplasm during Cytokinesis.
MICROTUBULES – Formed by the globular protein Tubulin. They polymerise to form tubes that determine the shape of the
cell. They also act as tracks for organelles moving around the cell.
INTERMEDIATE FIBRES – Gives strength to
cells and helps maintain integrity.
9
Q
C2) What is the function of the cytoskeleton of a cell
A
Providing mechanical strength to cells
Aiding transport within cells
Enabling cell movement.
10
Q
C2) What are the structural components of the nucleus of a cell
A
Double Nuclear Envelope – A double membrane which
compartmentalises the Nucleus and prevents damage. Protects the DNA.
Nuclear Pores – Allows molecules to enter and leave the cell
Nucleolus – Site of ribosome production. Composed of RNA and
proteins.
Chromatin – is the DNA. Contains the Genetic Code which controls the activity of the cell.
11
Q
C2) What is the function of the nucleus of a cell
A
1) Controls all the activity of the cell.
2) Where the Genetic Code (DNA) of the cell is stored, replicated, and copied into RNA (transcribed).
The Nucleus is attached to the Rough ER so the mRNA can easily get to ribosomes.
12
Q
C2) What are the structural components of the Rough Endoplasmic Reticulum of a cell
A
System of hollow tubes and
membrane bound sacs which form sheets called cisternae.
attached to the nucleus and covered with ribosomes.
Consists of an interconnected system of
flattened sacs.
13
Q
C2) What is the function of the Rough Endoplasmic Reticulum of a cell
A
Site of protein synthesis.
14
Q
C2) What are the structural components of the smooth Endoplasmic Reticulum of a cell
A
similar to RER but lacks ribosomes -is a system of interconnected tubules.
15
Q
C2) What is the function of the smooth Endoplasmic Reticulum of a cell
A
responsible for carbohydrate & lipid synthesis, and storage.
16
Q
C2) What are the structural components of the ribosome of a cell
A
A 2 subunit organelle.
Made from RNA and protein.
Not membrane bound.
Very small organelles: about 22nm in diameter.
Found free floating in the cytoplasm or attached to the Rough ER
17
Q
C2) What is the function of the ribosome of a cell
A
These are where protein is made.
They assemble amino acids into proteins in chains using mRNA.
18
Q
C2) What are the structural components of the mitochondria of a cell
A
Oval shaped.
Surrounded by two membranes (double membrane).
The inner membrane forms finger-like structure called cristae which increases the surface area.
The solution inside is called a matrix which contains enzymes for respiration.
Mitochondrial DNA – Small amounts of DNA, enable mitochondrion to reproduce and create enzymes.
19
Q
C2) What is the function of the mitochondria of a cell
A
Site of aerobic respiration.
As a result of respiration, they produce ATP (energy carrier in cells).
20
Q
C2) What are the structural components of the Golgi apparatus of a cell
A
Stack of flattened, membrane bound sacs (cisternae).
These are continuously formed from the ER at one end and budding off as Golgi vesicles at the other.
21
Q
C2) What is the function of the Golgi apparatus of a cell
A
Allows internal transport.
Receives proteins from the RER
Modifies and processes molecules (such as new lipids and proteins) and packages them into vesicles.
These may be Secretion vesicles (if the proteins need to leave the cell) or lysosomes (which stay in the cell).
Makes lysosomes
Lipid synthesis
22
Q
C2) What are the structural components of the lysosome of a cell
A
They are spherical sacs surrounded by a
single membrane.
23
Q
C2) What is the function of the lysosome of a cell
A
They contain powerful hydrolytic
digestive enzymes known as lysozymes.
Their role is to break down worn out components of the cell or digest invading cells.
24
Q
C2) What are the structural components of the cilia of a cell
A
‘Hair like’ extensions that protrude from some animal cell types.
In cross section they have an outer membrane and a ring of nine pairs of protein microtubules inside with two microtubules in the middle.
Known as a 9 +2 arrangement.
Arrangement allows movement.
25
C2) What is the function of the cilia of a cell
```
sensory function (e.g. nose), beat
creating a current to move fluid/mucous/objects
```
For locomotion
26
C2) What are the structural components of the flagellum of a cell
Similar to cilia but longer.
They stick out from the cell surface and are surrounded by the plasma membrane.
Like cilia they have a 9 +2 arrangement.
27
C2) What is the function of the flagellum of a cell
(Whip-like) enables a cells mobility.
The microtubules contract to make the flagellum move.
Propel cells forward e.g. sperm cells.
28
C2) What are the structural components of the chloroplast of a cell
Double membrane which encloses the
stroma.
Stroma contains: Starch grains, lipid stores, DNA, RNA, ribosomes.
Series of membrane-bound flattened sacs called thylakoids in the stroma.
Thylakoids stacked together are called grana.
Grana are linked together by lamellae.
The grana contain chlorophyll
29
C2) What is the function of the chloroplast of a cell
Photosynthetic reactions
30
C2) What are the structural components of the Large Permanent Vacuole of a cell
Single membrane bound (membrane is called a tonoplast).
Contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes etc).
Selectively permeable barrier
31
C2) What is the function of the Large Permanent Vacuole of a cell
Stores cell cap
Support herbaceous plants by making cells turgid.
Helps maintain shape and gives support by maintaining turgor pressure.
Sugars and amino acids act as a temporary food store.
32
C2) What does the DNA look like in a prokaryotic cell
The structure of DNA is fundamentally the same as in eukaryotic cells but it is packed differently
Prokaryote generally only have one molecule of DNA, A chromosome, which is supercoiled to make it more compact.
The genes on the chromosomes are often grouped into operons, meaning a number of jeans are switched on or off at the same time
33
C2) What does the ribosomes look like in a prokaryotic cell
Are smaller than those in eukaryotic cells.
The relative size is determined by the rate of which they settle, or form a sediment in solution.
The larger eukaryotic ribosomes are designed 80s in the smaller prokaryotic ribosomes are 80s
Both are necessary for protein synthesis, although the larger 80s ribosomes are involved in the formation of more complex proteins
34
C2) What does the cell wall look like in a prokaryotic cell
Made from peptidoglycan, also known as murein
A complex polymer formed from amino acids and sugars
35
C2) What does the flagella look like in a prokaryotic cell
The flagella of prokaryotes is thinner than the equivalent structure of eukaryotes and does not have the 9+2 arrangement
The energy needed to move the flagellum is supplied by the process of chemiosmosis, not from ATP as in eukaryotic cells
36
C2) What are the features of a Eukaryotic cell
1) Nucleus
2) DNA
3) DNA orientation
4) Extra chromosomal DNA
5) Organelles
6) Cell wall
7) Ribosomes
8) Cytoskeleton
9) Reproduction
10) Cell type
11) Cell-surface membrane
1) Present
2) linear
3) Associated with proteins called histones
4) Only present in the certain organelles such as chloroplasts and mitochondria
5) Both membrane-bound and non-membrane-bound
6) Chitin in fungi, Celulose in plants, not present in animals
7) Larger, 80s
8) Present, more complex
9) asexual or sexual
10) Unicellular and multicellular
11) Present
37
C2) What are the features of a prokaryotic cell
1) Nucleus
2) DNA
3) DNA orientation
4) Extra chromosomal DNA
5) Organelles
6) Cell wall
7) Ribosomes
8) Cytoskeleton
9) Reproduction
10) Cell type
11) Cell-surface membrane
1) Not present
2) Circular
3) Proteins fold and condense DNA
4) Circular DNA called plasmids
5) Non membrane-bound
6) Peptidoglycan
7) Smaller, 70s
8) Present
9) Binary fusion
10) Unicellular
11) Present
38
C4) why are enzymes important
So that chemical reactions can happen very fact
Enzymes are biological catalysts
They are globular proteins that interact with substrate molecules
39
C4) What is the role of enzymes in a reaction?
Involves in the synthesis of large polymer-based components
Digestion is also catalysed by range of enzymes
40
C4) How does an enzyme action work?
For a reaction to happen molecules need to collide in the right orientation. When High temperatures and pressure are applied the speed of the molecules will increase, so will the number of successful collisions and the overall rate of reaction
Different enzymes are produced by living organisms as each enzyme catalyses one biochemical reaction of which there are thousands in every given cell. This is termed the specificity of the enzyme
Energy needs to be supplied for most reactions to start this is called activation energy.
41
C4) What is the meaning of anabolic reactions
The chemical reactions required for growth are anabolic (building up) reactions and they are all catalysed by enzymes
42
C4) what is the meaning catabolic reactions.
Energy is released from large organic molecules like glucose, in metabolic pathways consisting of many catabolic (barking down) reactions. Catabolic reactions are also catalysed by enzymes
43
C4) What is the meaning of Metabolism
Reactions rarely happen in isolation but as part of a multi-step pathways. Metabolism is the sum of all the different reactions and reaction pathways. Can only happen because of the control and order imposed by enzymes .
44
C4) What is Vmax
Enzymes can only increase the rate of a reaction to a certain point
45
C4)How does an enzyme affect the activation energy of a reaction
The amount of energy needed is so large it prevents a reaction in happening. Enzymes help the molecules collide successfully and therefore reduce the activation energy required
46
C4) What is the lock and key hypothesis
In the same way that only the right key will fit into a lock only a specific substrate will fit the active site of an enzyme
When the substrate is bonded to the active site and enzyme substrate complex is formed.
The substrate that reacts and the product are formed in a enzyme product complex
47
C4) what is the active site
An area within the tertiary structure of the enzyme, that has a shape complimentary to the shape of a specific substrate molecule
48
C4) how is the substrate broken down in the active site.
The substrate is held in away by the enzyme that the right atom groups are close enough to react. the R-groups within the active site of the enzyme will also interact with the substrate, forming temporary bonds. This puts strain on the bonds within the substrate helping the reaction to occur
49
C4) What is the induced fit hypothesis of an enzyme
Research suggests that the active site of the enzyme actually changes shape slightly as the substrate enters.
This is a modification on the lock and key hypothesis.
The initial interaction between the enzyme and substrate is relatively weak but these week interactions rapidly changes the enzymes Tertiary structure that strengthen binding, putting strain on the substrate molecule. This can weaken a particular bond in the substrate therefore lowering the activation energy for the reaction
50
C4) What are intracellular enzymes
Enzymes that work within a cell
51
C4) How does an intracellular enzyme help
The synthesis of polymers from monomers. For example polysaccharides from glucose require enzymes
An example of this is hydrogen peroxide
52
C4) what are extracellular enzymes
All of the reactions happening within cells need substrates to make the product. The substrate need to be constantly supplied to cells. Nutrients present in the diet or environment of the organism supply these substrates
Nutrients are supplied in the form of polymers such as proteins and polysaccharides. These large molecules can’t enter cells directly. They need to be broken down
Enzymes are released from cells to break down these large nutrient molecules into smaller molecules in the process of digestions. These are called extracellular enzyme they work outside the cell that made them.
53
C4) How is starch digested
It begins in the mouth and continues in the small intestine
1) Starch polymers are broken down into maltose a disaccharide. The enzyme involved is called amylase produced by the saliva glands and the pancreas. Released in the saliva into the mouth and in pancreatic juice into the small intestines
2) maltose is broken down into glucose which is a monosaturated using the enzyme maltase which is present on the small intestine
54
C4) how is protein digested
Trypsin is a protease enzyme that catalyse proteins into smaller peptides which can then be broken down into amino acids.
Trypsin is produced in the pancreas and released with the pancreatic juice into the small in testing and acts on proteins.
55
C4) how can an enzyme structure be affected
By factors such as temperature and pH. They cause a change in the shape of the active site.
56
C4) how does temperature affect the rate of a reaction of an enzyme
Increasing the temperature, increases the kinetic energy of the particles. As temperature increases the particles move faster and collide more frequently.
Increasing the temperature will result in more frequent successful collisions between substrate and enzyme leading to an increase in the rate of reaction
57
C4) What is the definition of the temperature coefficient of the reaction
In enzyme
Is a measure of how much the rate of a reaction increases with a 10°C rise in temperature
For an enzyme reaction it is usually two meaning that the rate of reaction doubles with a 10°C temperature increase
58
C4) how does enzymes denature from temperature
As enzymes are proteins high temperatures affect the bonds holding the protein together making it vibrate more.
As the temperature increases the vibration increases onto the bonds strain and then break
The breaking of these bonds result in changes in the tertiary structure of the protein
Meaning it has denatured
When an enzyme is denatured the shape of the active site has changed and no longer complimentary to substrate therefore enzyme Will not function as a catalyst
59
C4) what is the optimal temperature of an enzyme
Optimal temperature is the temperature at which enzymes have the highest rate of activity.
In the human body optimum temperature is around 40°C
In thermophilic bacteria (Hot Springs) the optimal temperature is around 70°C
In psychrophilic organisms (cold areas) the optimal temperature is below 5°C
60
C4) how does denaturing above and below the optimal temperature affect the rate of a reaction
Denaturing above the optimal temperature, decreases the rate of reaction rapidly. This is because all of the enzyme molecules have a change in the active site and and it happens at about the same temperature so the loss of activity is rapid
Denaturing below the optimal temperature, decreases The rate of reaction. This is because the enzyme has not denatured they are just less active
61
C4) how do enzymes adapt to extremely cold environment
They tend to be more flexible structures, particularly that the active site making them less stable than enzymes to work at higher temperatures. Smaller temperature changes will denatured them
62
C4) how to enzymes adapt to extremely hot environments
The enzymes in these organisms are more stable than enzymes in other organisms this is due to the increased number of bonds, particularly hydrogen bonds and sulfer bridges in the tertiary structure.
The shapes of these enzymes and the active site are more resistant to change as the temperature rises
63
C4) how does PH affect an enzyme reaction
As enzymes are proteins, the hydrogen bonds and ionic bonds between amino acid r groups hold proteins in the precise 3-D shape because of interactions between polar R groups
The change in pH refers to a change in the hydrogen ion concentration. More hydrogen ions present in the low pH environment. Fewer hydrogen ions present in high pH environments
Hydrogen ions interact with polar r groups therefore increasing hydrogen ions increases the interactions. So more hydrogen ions present the less r groups are able to interact with each other this leads to bonds breaking and shapes changing. Reverse for lower PH
The active site will be at the right shape at a certain hydrogen ion concentration known as the optimal PH
When the pH changes The structure of the enzyme and therefore the active site is altered
64
C4) what is a renaturation of an enzyme
If the pH returns to the optimal then the protein will resume its normal shape and catalyse the reaction again
65
C4) How does an increased Number of substrate molecule affect the rate of a reaction
Leads to a higher collision rate with the active site of the enzyme and formation of a more enzyme substrate complexes therefore an increased rate of reaction
66
c4) how does an increased number of enzyme concentration affect the rate of a reaction
Will increase the number of available active sites in a particular area leading to an increase in enzymes from free complexes at a faster rate therefore increase the rate of a reaction
67
C4) what happens when the rate of reaction increases to V-max
At this point all of the active site occupied by substrate particles and no more enzyme substrate complex is can be formed into products are released from the active site
68
C4) what is an enzyme inhibitor
What are the two types of enzyme inhibitors
Inhibitors are molecules that prevent enzymes from carrying out the normal function of catalystis
Competitive and non-competitive enzyme inhibitors
69
C4) How does competitive inhibitor affect the rate of a reaction
Competitive inhibitors reduce the rate of reaction from a given concentration of substrate but does not change the Vmax of the enzyme it inhibits
If Substrate concentration is increased enough there will be so much more substrate than inhibitors that the original Vmax can still be reached
70
C4) how does it and non-competitive inhibition work
The inhibitor binds to the enzyme at a location other than the active site this is called an allosteric site
The binding of the inhibitor causes the tertiary structure of the enzyme to change meaning the active site changes shape
This results in the active site no longer being complimentary shape to the substrate so unable to bind to the enzyme
The enzyme cannot carry out its function and is inhibited
71
C4) What are examples of irreversible noncompetitive inhibitors
Irreversible inhibitors cannot be removed from the part of the enzyme they are attached to. They are often very toxic but not always.
Protein pump inhibitors are used to treat long-term indigestion. They Irreversibly block and enzyme system responsible for secreting hydrogen ions into the stomach
72
C4) why is end product inhibition important
A control mechanism for the reaction.
Excess products are not made and resources are not wasted.
It is an example of non-competitive reversible inhibition
73
C4) what are cofactors and co-enzymes
Some enzymes need a non-protein helper component in order to carry out the function as biological catalysts
They may transfer atoms or groups from one reaction to another in a multistep pathway or may actually form part of the active site of an enzyme this component is called a cofactor
If the cofactor is an organic molecule it is called a coenzyme
74
C4) how are coenzymes obtained
They are derived from vitamins, a class of organic molecules found in the diet.
For example vitamin B5 which is used to make coenzyme A essential in the breaking down of fatty acids and carbohydrates in respiration
75
C4) what is precursor activation
Many enzymes are produced in an inactive form known as inactive precursor enzymes
Particular enzymes can cause damage within the cell producing them water tissues where they are released, or enzyme this action needs to be controlled and only activated under certain conditions
76
C4) how are precursor enzyme activated
Precursor enzymes often need to undergo change in the tertiary structure particularly to the active site.
This can be achieved by the addition of a cofactor.
Before the cofactors added the precursor protein is called an apoenzyme. When the cofactors and in the enzyme is activated it is called a holoenzyme
Sometimes the change is brought about by the action of another enzyme. Sometimes a change in conditions such as pH or temperature and bring about the change these types are called proenzymes
77
C4) what is the prosthetic group
They are cofactors, required by certain enzymes to carry out the catalytic function.
Whilst some cofactors are loosely or temporarily bonded to the enzyme protein in order to activate them.
Prosthetic group are tightly bound and form a permanent feature of the protein
78
C4) how are inorganic cofactors obtained
Obtained via the diet and minerals including iron, calcium, chloride and zinc ions.
For example the enzyme amylase which breaks down starch is contain a chloride ions, necessary for the formation of a correctly shaped Active site
79
C4) how does competitive inhibition work
A molecule or part of a molecule with a similar shape to the substrate can fit into the active site of an enzyme
This blocks the substrate from entering the active site preventing the enzyme from catalysing the reaction
The ends and cannot carry out its functions and is inhibited
The non-substrate molecule that binds to the active site is a type of inhibitor. Substrate and inhibitor molecule present in a solution will compete with each other to buy into the active site of the enzyme. This will reduce the number of substrate molecules binding to active site in a given time and slow down the rate of a reaction. The degree of inhibition will depend on the relative concentration of substrate, inhibitor and enzyme
Most competitive inhibitor only bind temporarily to the active site, so it is reversible. An exception is aspirin
80
C4) what are examples of competitor inhibitors
Statins are competitive inhibitor is of an enzyme use in the synthesis of cholesterol. Statins are regularly prescribed to help reduce blood cholesterol concentration which can result in heart disease
Aspirin irreversibly inhibits the active site of COX enzymes
81
C4) What are the effects of non-competitive inhibitors on the rate of reaction
Increasing the concentration of enzymes or substrate will not overcome the effects of non-competitive inhibitors.
Increasing the concentration of inhibitors how old will decrease the rate of a reaction further as more active sites become unavailable
82
C4) what is the meaning of end product inhibtion
Term used for enzyme inhibition that occurs when the product of the reaction X as a inhibitor to the enzyme that produces it – Negative feedback
83
C4) what is the temperature coefficient
R1 / R2
84
C4) what is an example for cofactors and prosthetic group
Cl – as a cofactor for amylase
Zn2+ as a prosthetic group for carbonic anhydrase a
85
C5)What are Intrinsic proteins
Are transmembrane protein that are in bedded in both layers of the membrane
Have amino acids with hydrophobic r groups on the external surface which interact with the hydrophobic core of the membrane keeping them in place
86
C5) what are the two intrinsic proteins and how are they held in position
Channel proteins provide a hydrophobic channel that allows passive movement down a concentration gradient. Held in position by interactions between the hydrophobic core of the membrane and hydrophilic or groups on the outside of the protein
Carrier proteins plays a role in both passive, down a concentration gradient and active transport, against a concentration gradient by changing the proteins shape
87
C5) What are the uses of glycoproteins within the cell surface membrane
Intrinsic proteins that are embedded in the cell surface membrane with attach carbohydrate chains
Plays a role in Cell adhesion cells joining together to form a tight junction and as receptors for chemical signals
Helps with cell signalling-when the chemical binds to the receptor the cell responds causing a direct response (neurotransmitters at a synaptic junction) or a cascade of events (hormones)
88
C5) what is the plasma membrane
The cell-surface membrane which separates the cells from its external environment
89
C5) what is the importance of glycolipids on the cell surface membrane
They are lipids with attached carbohydrate chains
These molecules are called antigens and can you be recognised by the cells of the immune system as self and nonself
90
C5) what extrinsic proteins
Are present in one side of the bilayer
Normally have hydrophobic r group on the outer surface and interact with the polar heads of the phospholipid bilayer
Can we present in either layer and some moves between layers
91
C5) What is the importance of cholesterol in the cell surface membrane
Cholesterol is a lipid with a hydrophobic end and a hydrophilic end
Regulate the fluidity of the membrane
Cholesterol molecules positioned between phospholipids in a membrane bilayer
The hydrophilic end interacting with the heads and the hydrophobic end interacting with the tails pulling them together. Therefore adding stability to the membranes without making them rigid
The cholesterol molecule prevents the membrane becoming too solid by stopping the phospholipid molecules grouping too closely and crystallising
92
C5) How can the cell-surface membrane be a site for chemical reactions
Proteins in the membrane forming organelles or present within organelles have to be in particular positions for chemical reactions to take place
93
C5) how does temperature affect the permeability of the cell surface membrane
Phospholipids are constantly moving within the membrane when the temperature increases the phospholipid gain more kinetic energy and will move more
Making the membrane more fluid leading to it losing its structure. Continued temperature increase will entirely break down the cell
The loss of structure increases the permeability of the membrane making it easier for particles to cross
Carrier and channel proteins in the membrane will denature at higher temperatures, which is involved in transport across the membrane
94
C5) Why do solvent affect the permeability of the plasma membrane
Water is essential in the formation of the phospholipid bilayer. The hydrophobic tail of a phospholipid is oriented away from water creating a hydrophobic core and the hydrophilic heads interact with water keeping the bilayer intact
Many organic solvents are less polar or more polar than water which will dissolve membranes and disrupt cells. This is why alcohol is used as an antiseptic wipe as it dissolves the membranes of bacteria in a wound
Pure or very strong alcohol are toxic as they destroy cells. Non-polar alcohol molecules can enter the cell membrane and
the presence of these molecules between the phospholipids disrupt the membrane
When the membrane is disrupted it becomes more fluid and more permeable.
Some cells need intact cell membranes for specific functions for example transmission of a nerve impulse by Neurons, when its membrane is disrupted the nerve impulse no longer transmits as normal for example the changes in peoples behaviour when on alcohol
95
C5) Why are membranes considered to be partially permeable
Diffusion can only happen if the membrane is permeable to the particle for nonpolar molecules such as oxygen defuses through freely down a concentration gradient
The hydrophobic interior of the membrane repels substances with a positive or negative charge so they cannot pass through.
Polar molecules such as water can diffuse through but at a very slow rate. Smaller polar molecules pass through easier the larger ones
96
C5) what is facilitated diffusion
When polar molecules pass through a channel protein to diffuse across the membrane
Movement of molecules is down a chemical gradient and does not require external energy
The rate of facilitated diffusion is dependent on temperature, concentration gradient, membrane surface area and thickness but is also affected by the number of channel proteins present
97
C5) why can a membrane be considered to be selectively permeable
Membranes with protein channels can be selectively permeable as most protein channels are specific to one molecule or ion
98
C5) What is active transport
The movement of molecules into out of the cell from a region of lower concentration to a region of higher concentration requiring the use of ATP and a carrier protein
ATP is needed as particles are moving up a concentration gradient in the opposite direction of diffusion
The process is selective- specific substrates are transported by specific carrier proteins
99
C5) What are the stages of active transport
The molecule or ion to be transported binds to receptors in the channel of the carrier protein on the outside of the cell
On the inside of the cell ATP binds to the carrier protein and is hydrolysed into ADP and phosphate
Binding of the phosphate molecule to the carrier protein causes the protein to change shape opening up the inside of the cell
The molecule or ion is released to the inside of the cell
The phosphate molecule is released from the carrier protein and condenses with ADP to form ATP
The carrier protein returns to its original shape
100
C5) What is bulk transport
A different form of active transport
Larger molecules such as enzymes and hormones which are too big to move through channel or carrier proteins
ATP energy is required for movement of Vesicle along the cytoskeleton, changing the shape of cells to engulf material and diffusion of cell membranes as vehicles form
101
C5) how does endocytosis occur
Bulk transport of materials into the cell
Two types of endocytosis: phagocytosis for solids and pinocytosis for liquids the process is the same
1) The cell-surface membrane first invaginates (Bends inwards) When it comes into contact with the material to be transported
2) The membrane enfolds the material until eventually the membrane fuses forming a Vesicle
3) The Vesicle pinches off and moves into the cytoplasm forming a endosome which transfer the material for further processes
102
c5) how does exocytosis occur
Secretory versicles produced mainly by the Goldie apparatus moved towards and fuses with the cell-surface membrane the contents of the vehicle is released outside the cell
1) The secretary versicles moves out of the cytoplasm to transfer the material outside of the cell
2) The membrane unfolds the material until eventually the membrane fuses
3) The cell-surface membrane invaginates (Bends inwards) When it comes into contact with the material to be transported out
103
C5) What is the effect of osmosis on plants and animal cells
The diffusion of water into a solution lead to an increase in the volume of the solution
If the solution is in a closed system this results in an increase in pressure called hydrostatic pressure
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C5) How does osmosis affect animal cells
If an animal cell is placed in a solution with a higher water potential than the cytoplasm, Water will move into the cell increasing the hydrostatic pressure inside. The cell surface membrane cannot stretch much and cannot withstand the increased pressure, the cell wall will burst called cytolysis
If an animal cell is placed in a solution with a lower water potential than The cytoplasm water is lost to the solution. It will cause a reduction in the volume of the cell and the cell surface membrane Will become crenated
105
C5) What are the effects of osmosis on plant cells
Plant cells have a strong Celulose cell wall surrounding the cell surface membrane.
When water enters by osmosis the increased hydrostatic pressure pushes the membrane against the rigid cell wall this pressure is called Turgor. As the Turgor pressure increases it resist the entry of further water and is said to be turgid
When plant cells are placed in a solution with a lower water potential than its own water is lost from the cell by osmosis leading to a reduction in the volume of the cytoplasm which eventually pours the cell-surface membrane away from the cell wall this is called plasmolyse
106
C6) What is the Cell Cycle
The cell cycle is the process that all body cells (in multicellular organisms) use to grow and divide.
It starts with a cell that has already been produced by cell division and ends with this cell dividing to produce 2 genetically identical daughter cells.
107
C6) What are the 2 ways that eukaryotic cells divide
Mitosis: division into two daughter cells that are genetically identical to each other and to the parent cell.
Meiosis: division into four unique daughter cells with half the chromosomes of the
parent cell.
108
C6) Why is the cell cycle important
Produces genetically identical daughter cells (i.e. clones –maintains same number of chromosomes as the parent cell).
Growth of tissue/organism (not of cells)
Replacement of worn out/damaged cells
Repair of body tissues (e.g. bone, muscle etc)
Asexual reproduction/cloning
109
C6) What are the stages of the cell cycle
The cell cycle has two stages:
Interphase: G1, S and G2 phases
mitotic Phase:Mitosis and Cytokinesis
110
C6) What happens in G1
First growth phase of cell, synthesis of proteins, organelles replicate e.g. mitochondria, ribosomes etc. Cell increases in size.
End of G1 checkpoint.
111
C6) What happens in S
Synthesis phase. Replication of each chromosome in the nucleus
112
C6) What happens in G2
Second growth phase, cell continues to grow in size. Duplicated DNA is checked for errors. Energy stores (i.e. ATP molecules) are increased.
End of G2 checkpoint.
113
C6) What happen in G0 phase
phase where the cell leaves the cell cycle either temporarily or permanently.
Why?
Differentiation (& no longer able to divide)
DNA may be damaged
As you age the number of these cells in your body increases
Few types of cells can be stimulated to go back into the cell cycle from G0
114
C6) What is checked for at the G1 checkpoint
Cell size
Nutrients
Growth factors
DNA damage
115
C6) What is checked for at the G2 checkpoint
Cell size
DNA replication
DNA damage
116
C6) What is checked for at the spindle assembly checkpoint
Chromosome attachment to spindle
117
C6) What happens if the DNA is not checked
Mutations
Faulty DNA produced
Error in copying daughter cells
Daughter cells will not receive identical genetic information
Proteins not made or do not function properly
118
C6) What is the structure of a chromosome
Chromosomes are only visible during cell division.
Each chromosome consists of two chromatids joined somewhere along its length at the centromere.
Genetic information (genes/alleles) carried on each chromatid is identical.
During interphase DNA combines with proteins chalked histones to form chromatin
119
C6) What is a Homologous Chromosomes?
A pair of chromosomes – one maternal (from mother) and one paternal (from father)
The chromosomes carry the same genes but may carry different forms of the genes. A alternate form of the same gene is called an allele.
120
C6) What is the definition of sister chromatids
identical, carry the same versions of all their genes because one was produced as an exact copy of the other
121
C6) What does the acronym to remember the stages of mitosis and meiosis
PMAT
```
P = Prophase
M = Metaphase
A = Anaphase
T = Telophase
```
122
C6) What happens during prophase in the cell cycle
Chromosomes condense and thicken (and therefore become visible)
Consists of sister chromatids (2) joined at the centromere.
Two centrioles migrate to opposite poles of the cell (in animal and some plant cells)
Spindle fibres attach to specific areas on the centromeres and start to move the chromosomes to the centre (equator) of the cell.
Nuclear envelope disappears.
123
C6) What happens during Metaphase in the cell cycle
Brief phase
Individual chromosomes are moved by the spindle fibres to align at the metaphase plate/equator at the centre of the cell.
Chromosomes are attached to the spindle fibres by the centromere.
124
C6) What happens during Anaphase in the cell cycle
Centromeres holding the pairs of chromatids in each chromosome divide.
Chromatids separate
Spindle contracts (fibres shorten)
Each chromatid is pulled by their centromere to opposite poles of the cell.
125
C6) What happens during Telophase in the cell cycle
Chromatids have reached opposite poles of the cell. They uncoil and become long and thin again.
They are now called chromosomes
Spindle fibres disappear
Nuclear envelope reforms and enclose around the chromosomes at each pole.
126
C6) What happens in cytokines in the cell cycle
This is the phase where the cytoplasm divides.
In animal cells a ‘cleavage furrow’ forms. In plant cells a ‘cell plate’ forms.
This results in 2 genetically identical daughter cells being formed.
127
C6) What is meiosis
Meiosis is the process of cell division which produced four daughter cells which are not identical - they are different from each other. They have half the number of
chromosomes as the parent cell, making them haploid.
The process involves 2 nuclear divisions.
128
C6) What is the Importance of meiosis
Takes place in sex organs
Gametes produced here
Important to have genetically different gametes
This promotes genetic variation and allows for Natural Selection to take place
129
C6) What happened during interphase?
Before mitosis can occur, each DNA molecule (chromosome) in the nucleus is replicated during the interphase.
Each chromosome is converted into two identical DNA molecules called chromatids.
The two chromatids are joined together at a region called the centromere.
Condensed chromosomes combined with histone proteins are called chromatids.
130
C6) What are the stances of meiosis
two-stage process:
Meiosis I introduces genetic diversity by randomly dividing a cell’s genes in two. It results in two haploid cells.
Meiosis II is similar to mitosis. It splits each chromosome into its two chromatids and places one in each daughter cell. It results in four haploid gametes.
131
C6) What is the difference between Haploid and Diploid cells
A human somatic (body) cell contains
46 chromosomes. These consist of 23 pairs of homologous chromosomes.
Sex cells, or gametes, have only one copy of each chromosome: they are haploid. A somatic cell, containing two of each, is called diploid.
132
C6) How does genetic variation occur during meiosis?
Sexual reproduction creates genetic
diversity within a population, which is vital to a species’ survival.
Two processes during meiosis determine the unique genetic make-up of the four daughter cells:
During meiosis I, homologous pairs of chromosomes swap parts of their genetic material. This is crossing over.
The chromosomes from each pair are randomly allotted to the daughter cells by independent assortment.
133
C6) What happens in prophase 1 of the meiosis cycle
Chromosomes condense
Nuclear envelope disintegrates
Spindle formation begins.
Homologous chromosomes pair up forming bivalents.
Crossing over of genetic information occurs.
134
C6) What happens in Metaphase 1 of the meiosis cycle
Homologous pairs of chromosomes
assemble along the metaphase plate (instead of individual chromosomes – as in mitosis).
The orientation of each homologous pair is random and independent of any other homologous pair.
This is called independent assortment.
135
C6) What happens in Anaphase 1 of the meiosis cycle
The homologous chromosomes separate.
Each homologous chromosome (consisting of two chromatids) moves to opposite sides of the cell
The result is that 23 chromosomes (each
consisting of two chromatids) move to one pole, and 23 chromosomes (each consisting of two chromatids) move to the other pole.
136
C6) What happens in Telophase 1 of the meiosis cycle
Very similar to telophase in mitosis
Chromosomes assemble at each pole
Nuclear envelope reforms
Chromosomes uncoil
Cell undergoes cytokinesis
137
C6) How does Independent (random) assortment of chromosomes during anaphase 1 work
When homologous pairs line up along the equator of the cell during metaphase 1 and get separated during anaphase 1 of meiosis 1 it is completely random which chromosome from each pair ends up in the daughter cell.
This gives rise to new combinations of alleles.
138
C6) What happens in Prophase 2 of the meiosis cycle
Beginning of second division:
Chromosomes pair up and re-condense
Nuclear envelop breaks down again
Spindle fibres reform
139
C6) What happens in Mataphase 2 of the meiosis cycle
Chromosomes (sister chromatids)
are a lined on the equator by the spindle fibres.
Centrioles move to opposite poles of the cell.
140
C6) What happens in Anaphase 2 of the meiosis cycle
Centromere divides
Sister chromatids are separated
Spindle fibres contract
Chromatids move to the poles of the cells
This is the same as anaphase in mitosis
141
C6) What happens in Telophase 2 of the meiosis cycle
Chromatids uncoil
Spindle fibres break down
Nuclear envelopes reform
The cell undergoes Cytokinesis
4 haploid daughter cells are produced
142
C6) How does crossing over during prophase 1 work
During prophase 1 of meiosis 1 homologous chromosomes pair up as bivalents.
Chiasmata (‘twisting around each other’) form between chromatids of different but homologous chromosomes.
The chromatids still have the same genes but now have a different combination of alleles.
143
C6) What happens in Cytokinesis of the meiosis cycle
Cytoplasm and surface membrane divide, creating four independent haploid daughter cells.
144
C6) What is a Stem cell
Before a cell has differentiated, or specialised, it is called a stem cell
A stem cell is a cell that has not yet become a specialised cell
(undifferentiated).
A stem cell:
Can replicate many times (self renewal)
Has the potential to become specialised (i.e. different types of cell) (potency)
145
C6) what are embryonic stem cells
Embryonic stem cells are stem cells found in embryos are known as embryonic stem cells and can develop into almost every cell type under the right conditions in a lab.
Present a very early stage of embryo development.
Embryonic stem cells are totipotent before 7 days and pluripotent after the blastocyst forms.
146
C6) What are adult stem cells
Adult stem cells are stem cells found in adult tissues (such as bone marrow, brain, muscle, liver stem cells). These cells can only differentiate into the same type of cell as the tissue they came from e.g. liver stem cells can only become liver cells.
Present throughout life from birth.
Found in specific areas e.g. bone marrow and are mulitopotent.
Could be artificially triggered to become pluripotent.
Can be harvested from umbilical cords of newborn babies.
In animals, adult stem cells are used to replace damaged cells.
147
C6) What are the different potencies of stem cells
Totipotent – Totipotent stem cells that are able to differentiate into any type of cell found in body and into extra embryonic cells such as those in the placenta. These cells are found in the embryo at an early stage called the blastocyst. The ‘total’ individual. E.g. zygote
Pluripotent – Can form any cell type (e.g. embryonic stem cells) but not the whole organism.
Multipotent – Can differentiate into a number of closely related cell types within a certain type of tissue (e.g. haematopoeitic adult stem cells in bone marrow give rise to different types of blood cells).
Unipotent – Can not differentiate, but are capable of self renewal (e.g. progenitor cells, muscle stem cells)
148
C6) what are the sources of plant stem cells
They are present in the meristematic tissue (meristems) implants. This tissue is found wherever growth is occurring in plants.
This tissue is also located sandwiched between the phylum and xylem tissues and this is called the Vascular Cambium
149
C6) What are four uses of stem cells
Heart disease- muscle tissue in the heart is damaged as a result of a heart attack, normally irreparably - been tried experimentally with some success already
Parkinson‘s disease- the symptoms are caused by the death of dopamine production cells in the brain; drugs currently only delay the process of the disease
Muscular degeneration- this condition is responsible for causing blindness in the elderly and diabetes; scientists are currently researching the use of stem cells in its treatment and early results are very encouraging
Spinal injuries- scientists have resolved some movement to the hindlimbs of rats with damage to spinal cords using stem cell implants
150
C6) What areas have stem cells already been used in
The treatment of burns- stem cells grown on biodegradable meshes can produce new skin for burning patients, Quicker than the normal process of taking a graft from another part of the body
Drug trials- potential new drugs can be tested on the cultures of stem cells before being tested on animals and humans
151
C6) what are the ethical dilemmas to do with stem cells
The destruction of the embryo when stem cells of collected - not only religious but also moral beliefs as people believe life begins at conception and therefore this would be murder.
Lack of consensus about the rights of the embryo itself and who owns the genetic material being used in the research
Umbilical stem cells came over these ethical dilemmas but these are less useful than embryonic stem cells
152
C6) What is the meaning of a specialised cell
I saw that has differentiated to carry out a specific function
153
C6) how are Erythrocytes specialised for their function
Flattened biconcaved shape to increase the surface area to volume ratio essential to transport oxygen around the body
No nuclei or many organelles this increases the space available for haemoglobin the molecule that carries oxygen
Flexible so they can squeeze through narrow capillaries
154
C6) how are neutrophils specialised for their function
Essential role in the immune system
Multilobed nucleus making it easier for them to squeeze through small gaps to get to the sight of infection
Granular cytoplasm contains many lysozymes that contain enzymes used to attack pathogen
155
C6) how are Sperm cells specialised for their function
Function is to deliver genetic material to the female gamete the ovum
Have a flagellum so they are capable of movement and contain many mitochondria to supply the energy needed to swim
Acrosome on the head of the sperm contains digestive enzymes which are released to digests the protective layer around the ovum and allows the sperm to penetrate leading to fertilisation
156
C6) how are Palisade cells specialised for their function
Present in the Mesophyll containing chloroplasts to absorb large amounts of light for photosynthesis
Rectangular box shapes, closely packed to form a continuous layer
They have a thinwall increasing the rate of diffusion of carbon dioxide
Large vacuole to maintain turgor pressure
Chloroplast can move within the cytoplasm in order to absorb more light
157
C6) how are root hair cells specialised for their function
At the surface of roots need the growing tips
Large extension is called root hairs which increases the surface area of the cells
Maximise the uptake of water and minerals from the soil because of the large permanent vacuole, thin Celulose cell wall
158
C6) how are a pair of guard cells specialised for their function
On the surface of leaves form small opening is called The stomata,Necessary for carbon dioxide to enter plants for photosynthesis
Guard cells lose water and become less swollen as a result of osmotic forces, they change shape and stomata closes to prevent further water loss from the plant
The cell wall of a Guard cell is thicker on one side so the cell does not change shape symmetrically as its volume changes
159
C6) what is the meaning of tissue
Made up of a collection of differentiated cells that have a specialised function
160
C6) What are the Four main categories of tissues in animals
Nervous tissue - adapted to support the transmission of electrical impulses
Epidermal tissue – an adapter to cover body surfaces, internal and external
Muscle tissue - adapted to contract
Connective tissue - adapted either to hold other tissues together or as a transport medium
161
C6) what is the structure of squamous epithelium
Made of squamous epithelium cells
Known as pavement epithelium due to its flat appearance
Very thin due to the flat cells that make it up and because it is only one cell thick
Present when rapid diffusion across its surface is essential
Forms the lining of the lungs and allows rapid diffusion of oxygen
162
C6) What is the structure of ciliated epithelium
Made up of ciliated epithelium cells
Hairlike structures called cilia that moves in a rhythmic manner
Goblet cells are also present releasing mucus to trap any unwonted particles present in the air
Prevents the particle from reaching the alveoli inside the lungs
163
C6) What is the structure of cartilage
Connective tissue found in the outer ear
Contains fibres of the proteins elastin and collagen
Is a firm flexible connective tissue composed of chondrocyte cellEmbedded in an extra cellular matrix
Prevents the bones rubbing against each other causing damage
164
C6) what is the structure of muscle
Needs to be able to shorten in length in order to move bones
Different types of muscle fibres. Skeletal muscle fibres contain myofibrils contains contractile proteins
165
C6) what is the structure of epidermis
Single layer of closely packed cells covering the surface of the plant
Covered by a waxy waterproof cuticle to reduce the water loss
Stomata formed by a pair of Gard cells can open and close are present in the epidermis
166
C6)What is the definition of an organ
A collection of tissues that are adopted to perform a particular function in an organism
Made up of muscle tissues and connective tissue
167
C6)What is the definition of an organ system
Is comprised of a number of organs working together to carry out a major function in the body
168
C3) what are the roles of these cations
1. Calcium ion
2. Sodium ions
3. Potassium ion
4. Hydrogen ion
5. Ammonium ion
1. Nerve impulse transmission
Muscle contraction
2. Nerve impulse transmission
Kidney function
3. Nerve impulse transmission
Stomatal opening
4. Catalysis of reaction
PH determination
5. Production of nitrate ions by bacteria
169
C3) what are the roles of these anions
1. Nitrate ion
2. Hydrogen carbonate ion
3. Chloride ion
4. Phosphate ions
5. Hydroxide ion
1. Nitrogen supply to plants for amino acid and protein formation
2. maintenance of blood pH
3. balance positive charge of sodium and potassium ions in cells
4. cell membrane formation
Nucleic acid and ATP formation
Bone formation
170
C3) what is the bond that holds water molecules together and what is its characteristics
Hydrogen bond
Hydrogen bonds are relatively weak interactions, which break and reform between the constantly moving water molecule
171
C3) How is water a polar molecule
1) The atoms with the greater share of the negative electrons Will be slightly electronegative while the other item would be slightly electropositive
2) oxygen always has a much greater share of the electrons in an O-H Bond
3) oxygen and hydrogen bonded together is called an hydroxyl group
4) water contains two of these hydroxyl groups
172
C3) how does hydrogen bonds hold water molecules (H2O) together
Polar molecules interact with each other as the positive and negative regions of the molecule attract each other and form an hydrogen bond
173
C3) what are the characteristics of water.
high boiling point - takes a lot of energy to increase the tamp of water and change it to gas because of the hydrogen bonding
when frozen into ice it is less dense than other substances in solid form - because the hydrogen bonds are fixed to there positions father apart in a solid
water has cohesive properties - it can move as one mass because the molecules are attracted to each other
water is adhesive - water molecules are attracted to other materials
water has a skin of surface tension - as they are more cohesive to each other
174
C3) how is water important for life
water acts as a solvent - the solutes in an organism can be dissolved in it because it is a polar molecules
water acts as a medium for chemical reactions and also help transport dissolved component into and out of cells
water makes a very efficient transport medium within living things - cohesion between water molecules means that they stick together when transported through the body. Adhesion occurs between water molecules and other polar molecules and surfaces. Effects of adhesion and cohesion results in water exhibiting capillary action this means water can rise up a narrow tube against the force of gravity
Water acts as a coolant - helping to buffer temperature changes during chemical reactions because of the large amount of energy required to overcome hydrogen bonding
Water is stable - it does not change temperature will become aghast easily therefore providing a constant environment
175
C3) why is glucose a polar molecule and soluble in water. Why is this important
Because of the hydrogen bonds between the hydroxyl group and water molecules
Solubility in water is important because it means glucose is dissolved in the cytosol of a cell
176
C3) how is maltose (disaccharides) created
Condensation reaction between two alpha glucoses
177
C3) how is Cane sugar created (Sucrose)
Fructose + glucose = sucrose (disaccharides)
178
C3) what are Fructose and galactose
They are also hexose monosaccharides, six carbon molecule
Fructose is sweeter than glucose
Glucose is sweeter than galactose
179
C3) How is lactose created
Galactose + glucose = lactose (disaccharide)
180
C3) What are pentose monosaccharides
Sugars containing five carbon atoms.
To pentose sugars are important components of biological molecules:
Ribose is a sugar present in RNA nucleotides
Deoxyribose is the sugar present in DNA nucleotides
181
C3) what is the relationship between starch and glucose
Many alpha glucose is joined by glycosidic bonds form 2 slightly different polysaccharides known collectively as starch. Starch made by photosynthesis is stored as starch in chemical energy stores
182
C3) How is amylase formed
One of the polysaccharides in starch
Alpha glucose molecules joined together only buy 1-4 glycosidic bonds.
The angle of the bonding means that the long chain glucose twist to form a helix which is further stabilised by hydrogen bonding within the molecule
Making the polysaccharide more compact and less soluble than glucose molecules are used to make it
183
C3) How is amylopectin formed
The second polysaccharide formed in starch
Made by 1-4 glycosidic bonds between alpha glucose molecules but unlike amylase there are also glycosidic bonds forming by condensation reaction between carbon 1 and carbon 6 on 2 glucose molecules
Allowing amylopectin a branching structure with 1-6 branching points approximately once every 25 glucose subunits
184
C3) How is glycogen adapted for its function
Glycogen form more branches than amylopectin which means it is more compact and less space is needed for it to be stored this is important because animals are mobile
The branching of these poly saccharides make them very compact ideal for storage
Branching also means that there are many free ends where glucose molecules can be added or removed allowing the process of storing and releasing glucose molecules to speed up
185
C3) What are the key properties of amylopectin and glycogen
That they are insoluble, branched and compact
186
C3) How is cellulose formed
2 Beta glucose molecules are unable to join together in the same way as alpha glucoses because the hydroxyl groups of carbon 1 and carbon 4 are too far apart to react in a condensation reaction
Only way beta glucose molecules can join together is if alternate beta molecules are turned upside down
When this occurs it is unable to coil or form branches. A straight chain molecule is formed called cellulose
187
C3) What is the test for reducing sugars
Benedict’s reagent = copper II sulphate
1) placed the sample to be tested in a boiling tube. If it is not in liquid form grind it up and blend it with water
2) add an equal volume of Benedict’s reagent
3) heat the mixture gently in a boiling water bath for five minutes
Reducing sugars will react with the copper ions in the reagent. Resulting in addition of electrons to the blue Cu2+ reducing to brick red Cu+
The results could be Blue showing none, green colour showing low concentrations, yellow amber orange showing medium concentration and red showing high concentration
188
C3) What is the test for non-reducing sugars
Non-reducing sugars do not react with benedict’s solution
Sucrose is the most common non-reducing sugar
If sucrose is first boiled with hydrochloric acid it will give a positive result when warmed with benedict’s solution. Because sucrose has been hydrolysed into glucose and fructose
189
C3) what are lipids and what are their properties
Fats are molecules containing carbon, hydrogen and oxygen. Fats are lipids that are solid at room temperature and oils all lipids that are liquid at room temperature
Lipids are not soluble in water because lipids are nonpolar molecules because the electrons are equally distributed than polar molecules
190
C3) What is Triglycerides made off
One glycerol member of a group of molecules called alcohols
Three fatty acids member of a group of molecules called carboxylic acid’s consisting of a carboxyl group with a hydrocarbon chain
191
C3) what is the difference between saturated and unsaturated fats
Fatty acid chains that have no double Bonds present between the carbon atoms are called saturated because all the carbon atoms form bonds with hydrogen atoms
fatty acid with double Bonds between some of the carbon atoms are called unsaturated
Monounsaturated means one double bond between carbon atoms while polyunsaturated means 2 or more double bonds
Double bonds cause the molecule to Kings and bend and they cannot pack so closely together therefore making them liquid at room temperature I therefore describing oils
192
C3) what type of Triglyceride is healthier
I plants containing unsaturated triglycerides occurring naturally as oils tend to be more healthier in the human diet than saturated triglyceride
193
C3) How do phospholipid behave when interacting with water
A layer on the surface of the water with the phosphate heads in the water and the fatty acid tales sticking out of the water because of this they are called surface active agent
Or form a bilayer where the hydrophobic tails point inwards to the centre protected by the hydrophilic heads with a 2 layered sheet formation
194
C3 what are the characteristics of sterols
Another type of lipids found in cells.
They are not fat oils and have little in common with them structurally
Complex alcohol molecules based on a four carbon ring structure with a hydroxyl group at one end
They have a dual hydrophobic/hydrophilic characteristic. The hydroxyl group is polar and therefore hydrophilic. The rest of the molecule is hydrophobic
195
C3) what is the structure of cholesterol
Is a sterol
Manufactured primarily in the liver and intestines
When it is added to the cell membrane it regulate their fluidity by keeping membrane fluid at lower temperatures and stopping them becoming too fluid at higher temperatures
196
C3) how is the phospholipid formed
The phosphate ions PO3- have extra electrons and so are negatively charged and make them soluble in water
One fatty acid chains in a triglyceride molecule is replaced with a phosphate group
197
C3) Is the role of lipids
Because lipids are nonpolar the rules include:
Membrane formation and the creation of hydrophobic barriers
Electrical insulation necessary for impulse transmission
Waterproofing in birds feathers and paint leaves
Triglycerides have an important role in long-term energy store. Stored under the skin around vital organs which provide:
Thermal insulation to reduce heat loss
Cushioning to protect vital organs such as the heart and kidneys
Buoyancy for aquatic animals
198
C3) What is food synergy
It is believed that nutrition does not work in isolation but as part of the combined efforts of a whole range of Nutrients.
199
C3) What are the different amino acid is found in cells
20 different amino acids are commonly found in cells
Five of these are said to be non-essential as our bodies are able to make them from other amino acids
Nine are essential and can be obtained from what we eat
Six are said to be conditionally essential as they are only needed by infants and growing children
200
C3) what enzyme binds Multiple peptides together
The enzyme peptidyl transferase present in the ribosome catalyse the joining together of many amino acids with peptide bonds to make polypeptides
201
C3) What is the food test for lipids
The emulsion test
The sample is mixed with ethanol which is then mixed with water and shaking
If a white emulsion forms as a layer on top of the solution it is a positive indication of lipids if not then it is a negative result
202
C3) what is the primary and secondary structure of a protein
Primary structure - is a sequence in which the amino acids are joined. It is directed by information carried within DNA. Only bond involved is the peptide bond
Secondary structure- the oxygen, hydrogen and nitrogen atoms of the basic repeating sequence of amino acid interact. Hydrogen bonds may form within the amino acid chain into a alpha helix.
Polypeptide chains can lie parallel to one another joined by hydrogen bonds forming a beta plated sheet
203
C3) what is the Quaternary structure of a protein
The Association of two or more individual proteins called subunits.
The interactions between the subunits are the same as in the tertiary structure except they are between different protein molecules
Protein subunits can be identical or different. Enzymes often consist of two identical subunits whereas insulin has two different subunits.
204
C3) how does hydrophobic and hydrophilic interactions occur within a protein
As proteins are assembled in aqueous environment of the cytoplasm.
the way a protein foods will depend on whether r groups are hydrophobic or hydrophilic. Hydrophilic groups are on the outside of the protein while hydrophobic groups are on the inside of the molecule shielded from the water in the cytoplasm
205
C3) what is the food test for proteins
Peptide bonds form violet coloured complexes with copper ions in alkaline solutions.
Add equal volumes of 10% sodium hydroxide. Then add 1% copper sulphate solution until it is blue.
A mixture of an alkaline and copper sulphate solution is called biret reagent
206
C3) What is the tertiary structures of proteins
Tertiary structure - folding of a protein into its final shape. The coiling or folding of proteins into the secondary structure brings R groups of different amino acids closer together so they are close enough to interact and further folding of the sections will occur
Hydrophobic and hydrophilic interactions - weak interactions between polar and nonpolar r groups
Hydrogen bonds - these are weakest of the bonds formed
Ionic bonds - these are stronger than hydrogen bonds and form between oppositely charged r groups
Disulphide bridges- these are covalent and the strongest of the bonds but only form between R groups that contain sulphur atoms
These produce a variety of complex shape proteins with specialised characteristics and functions
207
C3) what are the characteristics of globular proteins
A compact, water-soluble and usually roughly spherical in shape
They form when proteins fold into the tertiary structure in the way in which the hydrophobic r groups of the amino acids are kept away from the aqueous environment, The hydrophilic r groups are on the outside of the protein meaning protein is water-soluble
Solubility is important for many different functions of globular proteins.
208
C3) what are the characteristics of insulin
Is a globular protein.
Is a hormone involved in regulating blood glucose concentration.
Hormones are transported in the blood system so need to be soluble.
Hormones also have to fit into specific receptors on the cell surface membranes to have The effect therefore need to have specific shape
209
C3) what are the characteristics of conjugated proteins
Conjoined proteins are globular proteins that contain a non-protein component called a prosthetic groups
Proteins without A prosthetic groups are called simple proteins
Different types of prosthetic groups. Lipids or carbohydrates can combine with proteins forming lipoproteins or glycoproteins. Metal ions and molecules made from minerals can form prosthetic groups
Haem groups are prosthetic groups. They contain iron II ions. Catalase and haemoglobin both contain in groups
210
C3) How is haemoglobin a conjugated protein
Haemoglobin is the red, oxygen carrying pigment found in red blood cells.
It is a Quaternary protein made from four polypeptide, 2 alpha and 2 beta subunits
Each subunit contains a prosthetic haem groups. The iron II ions present in the prosthetic groups are each able to combine reversibly with oxygen molecules allowing haemoglobin to transport oxygen around the body.
211
C3) how is catalase a conjugated protein
Catalase is an enzyme which means it increases the rate of reaction and each enzyme is specific to a particular reaction or type of reaction
Catalase is a Quaternary protein containing 4 haem prosthetic groups
The presence of iron II ions in the prosthetic groups allow catalase to interact with hydrogen peroxide and speed up its breakdown
Hydrogen peroxide is a common byproduct of metabolism but is damaging to cells if allowed to accumulate
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C3) what is a fibrous protein
Formed from long insoluble molecules.
This is due to the presence of High proportion of amino acids with hydrophobic r groups in their primary structure. Containing a limited range of amino acids usually with small r groups
Very repetitive primary structure of amino acids
Very organised structure is reflected in the rose fibrous proteins have. Keratin, elastin and collagen are examples of fibrous proteins
Fibrous protein tend to be strong, long molecules which are not folded into complex three-dimensional shapes like globular proteins
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C3) What are the characteristics of keratin
A group of fibrous proteins present in hair, skin and nails
Has large proportion of the sofa containing amino acid, cytosine.Resulting in strong disulphide bonds forming strong, inflexible and In soluble materials.
The degree of disulfide bonds determines the flexibility, hair contains fewer bonds making it more flexible than males.
The unpleasant smell produced when the hair is burnt is due to the presence of relatively large quantities of sulfur in these proteins
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C3) what are the characteristics of elastin
A fibrous protein found in elastic fibres
Elastic fibres are present in the walls of the blood vessels and in the alveoli of the lungs- gives the structures the flexibility to expand when needed but also to return to normal size
Quaternary protein made from many stretchy molecules tropoelastin
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C3) what are the characteristics of collagen
Fibrous protein
Is a connective tissue found in skin, tendons,Ligaments and the nervous system
A number of different forms but all are made up of three polypeptide wound together in a long and strong rope like structure
Collagen has flexibility
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C3)What are nucleic acids are made of
Contains the elements carbon, hydrogen, oxygen, nitrogen and phosphorus
Large polymers formed from many nucleotidesLinked together in a chain
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C3) what is the structure of a nucleotide
A pentose monosaccharide, contains five carbon atoms
A phosphate group, in organic molecule that is acidic and negatively charged
A nitrogenous base-complex organic molecules containing one or two carbon rings in its structure as well as nitrogen
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C3) What is deoxyribonucleic acid
The sugar in deoxyribonucleic acid is dioxiribose - are you sugar with one fuel oxygen atoms than ribose
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C3) why is DNA said to be antiparallel
Each strand of the DNA helix has a phosphate groupAt one end and a hydroxyl group at the other end
The two parallel strands are arranged so that they run in opposite directions
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c3) what is the importance of complimentary base pairing
Helps to maintain a constant distance between the DNA backbone resulting in parallel polynucleotide chains
Allowed DNA to have equal amounts of A and T as well as equal amounts of C and G
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C3)Why is ribonucleic acid important
The DNA of each eukaryotic chromosomes is a very long molecule, comprising of many hundreds of jeans and is unable to leave the nucleus in order to supply the information directly at the site of protein synthesis
To solve this short sections of the long DNA molecule corresponding to a single gene is transcribed into a similar short messenger RNA molecule
Each individual mRNA is therefore shorter than the whole chromosome of DNA
Polymer comprising of many monomer nucleotides
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C3) How is an RNA polymer created
RNA nucleotides are different to DNA nucleotides as the pentose sugar is ribose rather than deoxyribose
The RNA nucleotides form polymers in the same way as DNA nucleotides by the formation of phosphodiester bonds in condensation
RNA polymers are small enough to leave the nucleus and travel to the ribosomes where they are processed for protein synthesis
After protein synthesis the RNA molecules are derogated in the cytoplasm. The phosphodiester bonds are hydrolysed and the RNA nucleotides are released and reused
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C3) what are the stages of semiconservative replication
The unwinding and separating of the two strands of The DNA double helix is carried out by the enzyme DNA helicase. It travels along the DNA backbone breaking the hydrogen bonds between complimentary base pairs, unzipping
Free DNA nucleotides will then pair with a complimentary bases which have been exposed as the strands separate, Forming hydrogen bonds
DNA polymerase catalyses the formation of phosphodiester bonds between these nucleotides
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C3) what is degenerate code
As there are four different bases which means that there are 64 different base triplets or codons possible
this includes one code on the acts as the start codons, Signalling the start of a sequence that codes for a protein - methionine
Stop codons do not code for any amino acids and signal the end of the sequence
Having a single codon to signal the start of a sequence insures that the triplets of bases are read in frame meaning it is read from base 1 rather than base 2 or 3, so there are no overlapping
Only 20 different amino acids are regularly occurring in biological proteins, therefore many amino acids are coded for by more than one codon
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C3) what is the sense strand
Only one of the two strands of DNA contains the code for the protein to be synthesised
Runs from 5 to 3 end
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C3) what is the antisense strand
3 to 5 end
Is a complimentary copy of the sentence trend and does not code for a protein
It acts as a template strand during transcription, so that the complimentary RNA strand formed carries the same base sequences as the sense stand
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C3) what are the enzymes that control transcription
DNA helicase which helps with breaking off hydrogen bonds between the bases
RNA Polymerase which help with forming phosphodiester bonds between the RNA nucleotides
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C3) what is the importance of ribosomal RNA
Is one of the two subunits that make up ribosomes along with protein, composed of equal amounts
Important in maintaining the structural stability of the protein synthesis sequence and plays a biochemical role in catalysing the reaction
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C3) what is the importance of the ribosome in translation
The mRNA binds to a specific site on the small subunit of a ribosome
The ribosome holds mRNA in position while it is translated into a sequence of amino acids
Many ribosomes can follow on the mRNA behind the first, so that multiple identical polypeptide can be synthesised Simultaneously
Ribosomes act as the binding site for mRNA and tRNA E and catalyse the assembly of the protein
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C3)What is the importance of transfer RNA
Necessary for the translation of the mRNA
Composed of a strand of RNA folded in such a way that three bases, called anticodons are at one end of the molecule
Anti codon will bind to a complimentary codon on mRNA a following the natural base pairing rules. The tRNA molecules carry an amino acid corresponding to that codon
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C3) why do cells require energy
Synthesis-for example of large molecules such as proteins
Transport any further sample pumping molecules or ions across cell membranes
Movement-for example protein fivers in muscle cells and cause muscle contractions
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C3) what is the structure of ATP
Adenosine triphosphate are able to supply energy
Composed of a nitrogenous base, a pentose sugar and three phosphate groups
The base of the ATP is always Adenine
The sugar in ATP is ribose
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C3) why is ATP a bad long-term energy store
The instability of the phosphate bond in ATP means that it is a bad long-term energy Store
Fats and carbohydrates are much better for this Energy is released in the breakdown of the molecules in cellular respiration
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C3) what is phosphorylation
Occurs by reattaching a phosphate group to an ADP molecule
A water is removed in this process it is an example of a condensation reaction
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C3) why is ATP a good Immediate energy store
The interconversion of ATP and ATP is happening constantly in living cells, meaning cells do not need a large store of ATP
Due to the instability of ATP, cells do not store large amounts of ATP
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C3) what are the properties of ATP
Small - moves easily into, out of and within cells
Water-soluble - energy requiring process is happening aqueous environments
contains bonds between phosphate with immediate energy - large enough to be used for cellular reactions but not so large that energy is wasted as heat
Releases energy in small quantities - quantities are suitable to most cellular needs, so the energy is not wasted as heat
Easily regenerated - can be recharged with energy
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C3) what are the 3 tests for carbohydrates
Benedict's test
Iodine test for starch - yellow to purple/black
reagents strips - use a colour chart to determine the concentration of sugars
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C3) what are the different chemical elements that make up biological
molecules
C, H and O for carbohydrates
C, H and O for lipids
C, H, O, N and S for proteins
C, H, O, N and P for nucleic acids
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C3) what are the chemical tests for foods
biuret test for proteins
Benedict’s test for reducing and non-reducing sugars
reagent test strips for reducing sugars
iodine test for starch
emulsion test for lipids
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what is the formula for Rf
distance moved by the solute /
| distance moved by the solvent
