Biological Molecules Flashcards
(343 cards)
1
Q
What are the two types of Glucose that make up nearly every sugar?
A
Alpha Glucose and Beta Glucose.
2
Q
What super weird analogy do you use to remember how to draw alpha and Beta glucose.
A
Santa! Santa is the biggest alpha of them all, so for alpha glucose you use the catchphrase “ho ho ho” but spell it “HHO HOH HOH” these are 1 top and 2 bottom molecules bonded to the bottom three carbons (the fourth, in between HHO and HOH, is always OHH). Beta Glucose is HHO HOH OHH, the oh representing the underwhelming nature of a beta.
3
Q
How do you form Maltose?
A
By the condensation of 2 beta glucose molecules. Therefore, it is a disaccharide.
4
Q
How do you form Sucrose?
A
By the condensation of 1 glucose and 1 fructose molecule. Therefore, it is a disaccharide.
5
Q
How do you form Lactose?
A
By the condensation of 1 glucose and 1 galactose molecule.Therefore, it is a disaccharide.
6
Q
How do you form fructose?
A
fructose is a monosaccharide, made up of 6 carbons, with the formula C6 H12 O6.
7
Q
How do you form Galactose?
A
Galactose is a monosaccharide, made up of 6 carbons, with the formula C6 H12 O6.
8
Q
How do you form Glycogen?
A
By the condensation of many alpha glucose molecules. Therefore, it is a polysaccharide with the formula C180 000 H360 000 and O180 000. It is only found in animals.
9
Q
How do you form Starch?
A
By the condensation of many alpha glucose molecules. Therefore, it is a polysaccharide.
10
Q
How do you form Cellulose?
A
By the condensation of many beta glucose molecules. Therefore, it is a polysaccharide. It is only found in plants.
11
Q
What is a condensation reaction?
A
When two monosaccharides react with each other and release a hydrogen forming a hydrogen bond and creating the disaccharide/polysaccharide product.
12
Q
What is a Hydrolysis reaction?
A
The breaking down of poly/disaccharides into monomers via reacting a hydrogen molecule with it, forming it to break the hydrogen bond.
13
Q
What is a reducing sugar?
A
A sugar that can donate electrons to (reduce) another chemical.
14
Q
How can you test for reducing sugars? (give method)
A
Using the Benedict’s test. Add 2cm cubed of the food sample in liquiud form to a test tube. Add an equal volume of benedict’s reagent. Heat the mixture in a water bath for five minutes. In terms of concentration of sugars, the colour of the solution can indicate this.
Clear-none, Green-very low, yellow-low, orange-medium, red-high. The concentration goes up in order of the colour spectrum.
15
Q
Why is starch a good storage molecule?
A
Because it is coiled, it can be densely packed into small areas. It is also insoluble, so it does not cause osmosis and is therefore not likely to cause cells to become damaged or burst. Has many short branches so lots of enzymes can access and break it down into glucose monomers at one time.
16
Q
Why is glycogen a good storage molecule?
A
It is insoluble so therefore does not tend to draw water into the cell via osmosis and doesn’t diffuse out of cells. It is compact so a lot can be stored in a small space. It has more branches than starch so more enzymes can be reacted on it at one time to form glucose monomers. This is important, as animals are more active than plants so have a higher respiratory and metabolic rate.
17
Q
Why is Cellulose a good structural molecule?
A
Forms long, straight and unbranched chains,which lie parallel to each other and form hydrogen bonds between the layers. These molecules are grouped to form microfibrils, which then form fibres, which give it even more structural strength.
18
Q
What are the two main types of lipids we need to know about?
A
Triglycerides and phospholipids.
19
Q
What is the structure of a triglyceride?
A
A glycerol head with three fatty acid tails.
20
Q
What makes Triglycerides such good stores of energy?
A
- They have high energy because of all the carbon and hydrogen bonds.
- They have a low mass to energy ratio, meaning they release more energy per gram than carbohydrates.
- They have large insoluble molecules
- Release water when oxidised as of high ratio to hydrogen to oxygen
21
Q
What is the main difference between phosphate molecules and triglycerides?
A
Phosphate molecules still have a glycerol molecule, however, one of the fatty acid tails is replaced by a phosphate molecule.
22
Q
Name one use of Phospholipids.
A
They are used to make up cell membranes, alongside glycoproteins and glycolipids.
23
Q
What is a glycolipid?
A
A phospholipid combined with carbohydrates. It is important in cell recognition.
24
Q
Are phospholipids polar or non-polar? Why?
A
Polar. This is because they have hydrophillic heads and hydrophobic tails (the head is the phospholipid).
25
How do phospholipids react in water?
They form spherical, bilayer membranes.
26
What are proteins?
Proteins are usually large molecules made up of amino acids.
27
Why are fats better for energy storage?
They have a higher energy:mass ratio, meaning they release more energy per gram. They also are good for waterproofing as they are insoluble.
28
What is the structure of wax?
A long chain alcohol bonded to fatty acids with ester bonds.
29
What are the uses of wax?
Waxes are found in nature as coatings on leaves and stems. Wax waterproofs the leaves of the plant.
30
Describe how to draw an amino acid molecule.
In the centre is an alpha carbon, with a solitary h bond directly above it and the variable "R" group directly below it. This vertical column is called the side chain. To the left is the amino group. The alpha carbon is bonded to a nitrogen, with a hydrogen atom above it and a hydrogen atom to the left of the nitrogen. So it kind of looks like a right angle triangle, with N as the right angle and the 2 Hs as the other two corners. To the right is the Carboxyl group. This also looks like a right angle triangle, but mirror reflected (the other way round). It has a carbon bonded to the alpha carbon, with an oxygen double bonded just above it and an OH molecule just to the right.
31
What is the formula of a basic amino group?
-NH2
32
What is the formula of a basic Carboxyl group?
-COOH
33
Describe the primary structure of protein.
Primary structure is the sequence of amino acids into a polypeptide chain. It is vital in the function of the protein as it is determined by what amino acids are present, how many acids there are and what order they are in. If any of these change, it could change the structure of the protein.
34
Describe the secondary structure of protein.
The peptide bond that forms amino acids into polypeptides is an ionic bond. Because of this, the polypeptide molecules move round as they are attracted to the opposite charge. this draws them into a shape, most often an alpha helix or a beta pleated sheet.
35
Describe the Tertiary structure of protein.
Tertiary structure is the result of further twisting of the secondary structure. This occurs because of different bonds forming within the structure. These bonds are either disulfide bonds, ionic bonds between loose/unreacted carboxyl and amino groups and hydrogen bonds.
36
Describe the Quartinary structure of protein.
When all the polypeptides bond to make a large protein molecule. However, some smaller proteins stop at tertiary bonds.
37
Name the two main categories of proteins and give an example of each type.
Fibrous proteins e.g. Collagen
| Globular Protein e.g. haemoglobin
38
Why do fibrous proteins form such strong tissues?
The proteins form into long parallel chains and these chains are then linked into cross-bridge hydrogen bonds, which are weak on their own, but make the molecules very strong because of their multitude.
39
Describe the structure of Collagen.
The primary structure of a polypeptide chain. The secondary structure is a very tightly coiled alpha helix. The tertiary structure is also a helix shape. The quarternary structure is three of these coiled polypeptide chains twisted together, like a plait or a rope.
40
What is collagen?
Collagen is a fibrous protein found in tendons and skin of animals. it has a lot of glycerine, so can be visualised as the weird, carnivore-plasm stuff next to animal bones.
41
What is an enzyme?
An enzyme is a large protein that acts as a biological catalyst.
42
What is the active site of an enzyme?
The are that a substrate fits with an enzyme and interacts.
43
What is the Enzyme-substrate-complex?
When the enzyme is completely connected to the substrate.
44
what is activation energy?
The energy needed to commence a reaction.
45
What conditions are needed for a reaction to take place?
- reactants must collide with sufficient energy to alter the arrangement of their atoms
- The free energy of the products must be less than that of the substrates/reactants
- their must be sufficient activation energy
46
Why is the lock and key model now considered a historical/outdated model?
it was inaccurate, because though it did explain how a substrate fitted an active site specifically and broke it into smaller molecules, it eluded that the shape of an enzyme's active site was rigid and doesn't change and that an active site only fits one substrate. We have now replaced this with the induced fit model.
47
Describe the induced fit model.
It describes how an enzyme tends to form the shape of it's active site whilst it is in Enzyme-substrate-complex.
48
How does protein structure support the idea of the induced fit model.
The flexibility in the polypeptide chain allows the enzyme to shape it's active site around the substrate. This also contributes to the idea of denaturing, as the polypeptide chain in enzymes will lose it's structure/flexibility if the hydrogen bonds in the structure are broken, and these bonds can be broken very easily, the enzyme will not be able to fit around the substrate as easily, which cause it not to be able to fit and perform its function.
49
how can enzymes help in making bonds between molecules that would usually repel?
It can hold them together with it's tensile strength, like putting a rubber band around two halves of an apple.
50
How could you test for a lipid in a sample?
------The emulsion test-----
+ Take a completely dry and grease free test tube
+ Add 5cm^3 of ethanol to 2cm^3 of sample in the test tube and shake thoroughly to dissolve any lipids
+ Add 5cm^3 and shake gently
+ If a white emulsion appears, it indicates the presence of a lipid.
+ As a control, repeat the method using water instead of ethanol-- the water should stay clear.
51
What are nucleotides made up of?
A phosphate group, a 5 carbon sugar and a nitrogenous base.
52
What are the two main 5 carbon sugars that make up nucleic acids?
Ribose and deoxyribose.
53
You have a mnemonic for the nitrogenous bases, All Gangsters Carry Tea, what do these letters (AGCT) stand for?
```
A- adenine
G- guanine
C- cytosine
T- thymine
( uracil in RNA)
```
54
What is a chromatid?
One of the two identical X shaped arms of a chromosome.
55
What is a centromere?
The point at which two chromatids are joined together.
56
What happens in Interphase?
The cell is still functioning as it grows and the DNA replicates. When you see a cell going through interphase in a cell, you can't see the chromosomes.
57
What happens during Prophase?
The chromosomes condense and become visible through a microscope. The centrioles begin to move to opposite ends/poles of the cell. The spindle begins to form.
58
What happens during Metaphase?
The nuclear envelope breaks down. Chromosomes align along the equator/centre of the cell. Spindle fibres (microtubules) connect centrioles to centrosomes of chromosomes.
59
What happens during Anaphase?
Centromeres split, allowing chromatids to separate. chromatids move towards poles pulled by the spindle fibres.
60
What happens during telophase?
Spindle fibres disperse, nuclear envelope reforms, chromosomes decondense/unravel.
61
What type of proteins are antigens?
Globular proteins
62
What is the definition of an antigen?
An antigen is any part of the immune system that is recognised as foreign by our immune system.
63
What are the two types of defence/immune systems animals have?
Non specific and specific.
64
What are the features of the non-specific immune system?
Physical barriers to prevent the ingestion of antigens and phagocytosis.
65
What are the features of the specific immune system?
B lymphocytes and T-Lymphocytes.
66
What is a phagosome?
Where, in a phagocyte, the vesicle carrying the pathogen
67
What is lysozyme?
The enzyme found in lysosomes that breaks down the pathogen in phagocytosis.
68
Describe the journey of a pathogen during phagocytosis?
The pathogen travels through the cell membrane, but is then trapped in a vesicle. This vesicle then carris the pathogen to the phagosome, where it is stored to be broken down. Lysosomes are then secreted and they enter the phagosome, and break the pathogen down using lysozymes.
69
What sort of molecules can diffuse?
Only small, non-polar molecules can diffuse across cell surface membranes, such as oxygen and carbon dioxide.
70
Define Facilitated Diffusion in 5 features
+ It is a passive process
+ It relies on the kinetic energy of diffusing molecules
+ Occurs through trans membranes and carriers
+ Has to happen at these specific points in a cell membrane
+ Occurs down a concentration gradient
71
What are protein channels?
Water-filled hydrophilic channels. They only allow specific, water-soluble molecules to pass through. However, these ions are very selective and will remain closed unless specific ions are present. Can be drawn in a diagram to look like a fortune cookie with a hole in the middle (in the middle of a phospholipid bilayer).
72
What are Carrier Proteins? Four features
+Carry molecules.
+ The molecule has to be specific to the protein
+ The molecule binds to the protein, which causes to change shape, and is then reshaped when the molecule is released
+ Only uses the kinetic energy the molecule already has (Can be drawn in a diagram to look like a fortune cookie with a hole in the middle (in the middle of a phospholipid bilayer)).
73
What is water potential?
It can help quantify osmosis, as water always moves from a higher water potential to a lower water potential. 100% pure water has has a water potential of 0. Adding solutes reduces the water potential (so it is negative).
74
What happens when a cell is too hypertonic?
It becomes plasmolyzed. this means the cytoplasm shrinks, so everything inside the cell membrane looks smaller and shrivelled ( though membrane-bound organelles stay the same size). This means the cell membrane looks like it is shrinking away from the cell wall.
75
What do you call it when a animal cell becomes too hypotonic?What does it look like?
It can cause crenation. This looks like the cell shrivelling.
76
What do you call it when a animal cell becomes too hypotonic?
It becomes too turgid and can burst, which is called lysis.
77
Describe DNA replication
DNA replication needs to occur to pass genetic information on to the next generation. When DNA is replicated, it is done semi-conservatively, meaning that each time it is copied, only half of the information is made new.
78
Describe how to recognise glycolipids in a diagram of a phospholipid
Glycolipids are carbohydrates bound to lipids. The lipid portion/molecule would be embedded in the bilayer, with the chain of carbohydrates extending outside of the membrane. This is helpful because it as the carbohydrates can act as recognition and binding sites.
79
What is the usual function of a fibrous protein? Give an example
Fibrous proteins usually have structural functions. An example of this would be collagen, which is found in the tendons which join muscle to bone.
80
Describe the structure of Collagen-- Primary, Secondary, Tertiary, Quatinery and random feature
+ The primary structure is a polypeptide chain
+ The secondary structure is very tightly coiled
+ The tertiary structure is also a helix shape
+ The quaternary structure is three of these coiled polypeptide chains linked together
+ The high concentration of glycerine (an amino acid) helps it pack closely together
81
How do fibrous proteins form fibres?
The proteins form long parallel chains, these chains are then linked with hydrogen bond "bridges", which help them form very stable molecules.
82
What is the general function of globular proteins (give two examples)
Globular proteins perform metabolic functions. Enzymes and haemoglobin are examples of metabolic proteins.
83
What biological molecule controls the cell cycles to try and prevent uncontrolled cell replication (cancer).
Control Genes
84
Name 5 preventable Cancer causes (Doses)
```
Diet
Obesity
Sunlight Exposure
Exercise
Smoking
```
85
What are the three treatments for cancer?
Surgery, Radiotherapy, Chemotherapy
86
How do the four types of chemotherapy work?
clues--
1) deoxiribo-blockade
2) Pin curls
3) Tying DNA's Tubes
4) Stopping the "needle on a spinning wheel bran flakes"
1) Blocks enzymes that are necessary for protein synthesis
2) Prevents DNA unwinding (which is required for mitosis), like pinning a curl in place
3) Inhibits the synthesis of new nucleotides (stops mitosis reproduction)
4) Prevents the development of the spindle fibres ( essential for anaphase)
87
What is the function of smooth endoplasmic reticulum?
The synthesis of lipids and carbohydrates
88
What is the function of rough endoplasmic reticulum?
Aids the synthesis of proteins.
89
What is the function of golgi apparatus?
Produce secretory enzymes, such as those secreted by the pancreas. Secretes carbohydrates (i.e. cellulose) lipids, and enzymes like lysozymes.
90
What is the function of lysosomes?
Aids phagocytosis
Releases enzymes to the outside of the cell, in order to destroy material around the cell
digests worn out organelles to re-use the base components
Completely break down cells after they have died
Basically the over-protective mother of the cell
91
Name the three most important features of the mitochondria.
Double membrane- outer flat one and inner, heavily folded christae membrane.
Christae- Folded membrane, allows for more reactions to take place as there is a larger surface area
Matrix- The fluid that reactions such as respiration takes place in, thicker than the cytoplasm.
92
Name the four most important units in the nucleus
The Nuclear envelope
The Nuclear pores - important for molecules such as ribosomes and RNA
Nucleoplasm- goo in the nucleus
Chromosomes
the nucleolous- the largest structure in the nucleus, makes ribosomes
93
Name the two most important units in the chloroplasts
Grana and Stroma
94
What is the structure and function of Grana?
Grana are made up of stacks of circular, coin-like discs called thylakoids. These are the site of light- dependant reactions such as photosynthesis.
95
What is the structure and function of the stroma?
Colourless fluid surrounding the grana, contains the enzymes required for photosynthesis as well as DNA and ribosomes.
96
What are the maximum magnification and minimum resolution of light microscopes?
Maximum Magnification = x 1500
| Minimum Resolution = 200 um
97
Name three features of light microscopes
Uses waves of light energy
Shows the real object colour in the image
Creates a 2 dimensional image
98
Name three features/strengths of using a TEM microscope?
+ Highest magnification and resolution as there is a shorter wavelength of electrons
+ Focuses using an electromagnet
+ works by shining a beam of electrons through a thin specimen an then focusing these to form a digital image
99
name 4 drawbacks of using a TEM microscope
```
Produces a 2D digital image
Can not look at living cells/specimen
Must be in a vacuum
Complicated preparation may create artefact
Does not produce true colour image
```
100
how does an SEM microscope work?
It passes a beam of electrons over the surface of the specimen, calles a scanning beam
The specimen will have been coated in heavy metals, so the electrons will be reflected to form an image
this means it produces a 3D image using a condenser electromagnet. This is good as the specimen doesn't need to be thin.
101
What are 2 uses of monoclonal antibodies?
Cancer and Pregnancy tests
102
What does the structure of a monoclonal antibody look like
Antibodies are composed of 4 poly peptide chains: 2 heavy chains, 2 light chains. These chains are joined by disulfide bonds. Overall, this forms a Y shaped structure - The "stem"/vertical bit of the y is the constant region, that stays the same for every antibody, while the "arms"/ v-shaped bit of the y is the variable region, that is specificly shaped for binding to a specific antigen.
103
Where do T lymphocytes mature?
In the thymus gland
104
What type of immunity are T cells part of?
Cell-Mediated immunity
105
What are the 2 types of T cell?
Helper T cells (Th), Cytotoxic T cells (Tc)
106
what is the role of Th cells in cell-mediated immune response?
Activated T cells divide by mitosis to produce Th cell clones. This is done because, once the original T cell has binded to the antigen-presenting cell, The Th cell clones have receptors specific to that antigen, so it can recognise pathogens with the same antigen. Basically, these cells recognise pathogens, help activate mitosis ( which in turn can activate Tc cells, phagocytosis and B cells) and can form memory cells.
107
What is the role of Tc cells in cell cell-mediated immune response?
Tc cells are activated by the releasing of Cytokines. They produce the protein perforin which forms "pores" or holes in the target cells membrane. They are triggered by Th cells, and are used to break down pathogens and antigen presenting cells. they can cause cell death.
108
What are two main features of Cell Mediated immunity?
It requires the use if T cells and it requires antigen Presenting cells
109
How are T cells adapted for their function?
They have receptor proteins on their outer membranes, which are specific in order to bind to a specific antigen.
110
What are 2 key features of Humoral Immunity?
B lymphocytes and antibodies.
111
How can antigens break down a pathogen? (three ways)
Agglutinate cells together or to the pathogen/Antigen-presenting cell
Stop pathogens invading body cells
Bind to free toxin proteins
112
How is the B cells structure related to what pathogen it engulfs?
The B cell has antibodies on it's outer membrane. It will only bond with pathogens/Antigen resenting cells with corresponding antigens to the antibodies on their cell surface.
113
How are Th cells used in humoral immunity?
After the B cell has engulfed the pathogen (so now displays it's antigens), corresponding receptor proteins on T cells will bind to these antigens and trigger the antigen-presenting B cell to clone by mitosis.
114
What are the 2 types of B cell an activated B cell will become after mitosis?
Plasma cells- cells that secrete antibodies that are relative to the antigen from the pathogen they engulfed, so can recognise that pathogen in future
Memory Cells- Stay in the blood until the pathogen enters the body in future, as it has the corresponding antibodies to recognise it and break it down.
115
How are cancer cells recognisable to monoclonal antibodies?
They have specific surface antigens called tumor markers which monoclonal antibodies can bind to.
116
How can monoclonal antibodies help treat cancer?
Monoclonal Antibodies can be specifically produced to bond to tumor markers on cancer cells. Anti-cancer treatment drugs can be attached to these antibodies, which are released when the antibodies bind to the antigens.
117
What is one positive of using Monoclonal Antibodies to treat Cancer?
This treatment method reduces side effects as the drugs will only attack cancer cells specifically, whereas chemotherapy and radiotherapy are often not so specific.
118
What is HcG?
A hormone produced in the placenta of pregnant women, which can be found in her urine.
119
How can monoclonal antibodies be used to detect pregnancy in pregnancy tests alongside HCG.
Monoclonal Antibodies are immobilised and attached to coloured beads in pregnancy tests
When urine containing HCG hits the stick, the HCG will bind to the antibodies.
This HCG-Antibody-colour complex will then move along the stitch until it is trapped by another type of antibody.
These accumulate and produce a blue line to indicate pregnancy (though the line will not appear without HCG)
120
Name one ethical issue towards the use of Monoclonal Antibodies
To actually produce this antibody, mice are used. However, these antibodies are cloned by the use of tumor cells. This raises ethical issues as of the exploitation of animals and the fact that tumor cells can mutate uncontrollably and are usually just generally unsafe.
121
Name an illness Monoclonal antibodies can't treat
Judging by the failed drug trial of 2006, monoclonal antibodies can not treat multiple sclerosis.
122
what does the Specific Immune System consist of?
Humoral and Cell Mediated Immunity (T and B lymphocytes)
123
What does the Non- Specific Immune System Consist of?
Phagocytosis and Physical Barriers such as skin and cilia.
124
What is Primary Immune Response?
The response that occurs when an unfamiliar pathogen first invades the cell. As the pathogen is unfamiliar, there will not be any pre-existing memory cells or antigens for it, so relatively few specific T and B cells can recognise it, and few clones of these corresponding T and B cells will be made. This is when symptoms are most likely to occur.
125
What are Memory Cells?
Cells that are produced from activated by specific T and B cells, so have relevant antigens and antibodies to a specific pathogen. They remain in your blood for a number of years, so can recognise the pathogen in future.
126
What is secondary Immune Response?
Occurs when the same pathogen infects a person for the second time. Memory cells for the pathogen are present, so the pathogen's elimination is much faster. The memory cells don't need to specify, so the T cells can immediately divide into Tc cells and the B cells into plasma cells when activated, so the pathogen is broken down much faster, usually before symptoms can set in.
127
Give an example of active immunity?
Vaccinations
128
What are the two types of organisms in vaccinations?
Attenuated Microorganisms (The organisms are still alive, but are slightly weakened or diminished), or Dead Microorganisms (would still present the antigens needed to make memory cells).
129
Give an example of naturally occurring Passive Immunity
Heredity, mother-to-baby immunity, usually due to memory cells being passed through blood from the placenta.
130
Give an example of artificial passive immunity
Antibodies from the blood plasma of a previously infected person being injected into someone currently infected (or at risk of infection). Though this does assist the body's natural immune response, these antibodies can't form long term immunity on their own.
131
Name a pathogen subject to antigenic variability?
Influenza (hence why we are always getting new vaccines).
132
Describe antigenic variability
If the antigens on a pathogen remain constant, we remain immune to that pathogen. However, if a pathogen mutates and presents different antigens, the body does not have memory cells that recognise them, so requires new primary response, so people can experience symptoms of infection.
133
What sort of pathogen is HIV?
A Virus
134
How is HIV spread?
Via bodily fluids (i.e. blood or sexual fluids).
135
What does HIV stand for?
Human Immunodeficiency Virus
136
What is the genetic material within HIV?
RNA
137
What are the 7 stages of HIV replication?
Binding, Fusion, Reverse Transcription, Integration, Replication, Assembly and Budding.
138
What happens in the binding stage of HIV replication?
HIV tends to replicate using Th cells. The antigen on the HIV binds to a protein on the helper cells membrane called CD4. CD4 is most often found in Th cells.
139
What happens in the Fusion stage of HIV replication?
The capsule of the HIV molecule fuses with the Th cells cell membrane.
140
What happens in the Reverse Transcription stage of HIV replication?
The HIV reverse transcripts its DNA into RNA
141
What happens in the Integration stage of HIV replication?
The Viruses new DNA is moved into the nucleus of the Th cell, where it is inserted into the DNA of the actual human cell. Like a DNA sandwich, where the virus DNA is the filling and the Th cells DNA is the bread.
142
What happens in the Replication stage of HIV replication?
The HIV DNA uses it's genetic information to create messenger RNa. It does this using the Th cells protein synthesis enzymes. This mRNA contains the instructions for making new HIv molecules. This mRNA then passes out of the nucleus through a nucleic pore.
143
What happens in the Assembly stage of HIV replication?
The new parts of the HIV created in the Th cell are then assembled into new molecule on the cell membrane.
144
What happens in the Budding stage of HIV replication?
The HIV molecules break away from the Th cells with a piece of it's cell surface membrane used to create it's new lipid envelope, a bit like a patchwork quilt. This prevents it from being recognised in future.
145
How does HIV cause AIDS?
HIV can weaken the normal immune system, causing AIDS. they do this by reducing the amount of Th cells in a persons immune system. Therefore, AIDS sufferers will be infected a lot easier, and infections will be a lot more dangerous.
146
What does the ELISA test stand for?
The Enzyme Linked Immunosorbent Assay
147
How does the ELISA test work?
It uses antibodies to detect presence and quantity of specific antigens. It is very sensitive, it can detect even very small amounts of antigens. Can detect HIV, Tuberculosis, Hepatitis and can even test for the presence and amount of drugs in a person's system.
148
Why don't antibiotics work on viruses.
antibiotics work by disrupting a pathogen's metabolic processes or cell structures, but in a virus, there are no metabolic processes to disrupt. It also can not disrupt cell structures as viruses work within our own body cells and contain some of our cell material. The protein coat on viruses also mean that the antibiotics can not bind to it.
149
What is the energy in active transport made by?
ATP
150
What are two features all exchange surfaces that relate to surface area and thickness?
All exchange surfaces are adapted to have a large surface area relative to the volume of the organism and are very thin so that diffusion can occur across a short distance
151
What are the elements of Gas Exchange in Insects?
Spiracles, Tracheae and Trachioles
152
What are spiracles?
They are stomata-like structures in the skin/exoskeleton of the insect. They are little holes in the walls of the insect that take up gas.
153
What are the Tracheae?
They are tubular structures attached to the spiracles. Like the Trachea in the lungs. It transports the gas within the insect.
154
What are trachioles?
They are like the broncioles as they branch out from the Tracheae and deliver blood to the tissues of the insect, to exchange the gas.
155
How are diffusion gradients used in gas exchange in insects?
Different diffusion gradients exist along the length of the tracheal system, with the ends of the trachioles having the lowest concentration of oxygen and the highest concentration of CO2, as a result of nearby respiration, and causing the trachioles to draw oxygen further along the system.
156
How do insects use muscles to aid gas exchange?
Insects flex their bodies by contracting their muscles. This expands and compresses the system. Air sacs between the tracheae and the trachioles expand and compress. This fluctuating pressure moves air in and out of the body, ventilating the system.
157
How is water used in gas exchange in insects?
The trachiole ends are filled with water. During periods of intense activity, lactose (from lactic acid) builds up. As lactose is a solute, water is drawn into the cells to rebalance the cells. Therefore the trachioles move the water in the system, and this diffuses by osmosis into the cells, allowing more room for gas in the trachioles, increasing gas exchange.
158
How can Benedict's test be adapted for non-reducing sugars?
You would have to hydrolyse the disaccharide/polysaccharide into the reducing monosaccharides. If reducing sugars were not already present, you would have t add 2cm cubed of the food sample to 2cm cubed of hydrochloric acid (in order to hydrolyse the sample). You would then slowly add Sodium Hydrogencarbonate to the mixture, to neutralise the acid (benedict's reagent doesn't work in acidic conditions) and make sure it is alkaline using litmus/pH paper. Add 2 cm cubed of benedict's reagent to the sample and heat for 5 minutes in a water bath and follow the colour scale to quantify your results.
159
Why are polysaccharides good storage molecules?
Because they are such large storage molecules, they are insoluble.
160
What monosaccharide is cellulose made up of?
beta glucose
161
How can cellulose form strong structures?
As every other glucose molecule is flipped 180 degrees,
exposed OH- groups are can be bonded to the other Glucose molecules in other chain molecules, forming hydrogen bonds between these molecules. These form microfibres that can eventually form fibres.
162
What are the four uses of lipids?
Energy source, Waterproofing, Insulating and Protection.
163
Why are triglycerides often present in animals/plants in desserts or hot climates?
As they have a higher ratio of hydrogen molecules to Oxygen molecules, they can release water when oxidised, making them a very good emergency water source.
164
How can you test for proteins?
Using the biurets test. To a liquid food sample, add an equal amount of sodium hydroxide solution. Add a few drops of very dilute (0.05%) copper sulfate solution and mix gently. if peptide bonds are present, the solution will turn purple.
165
How can competitive inhibitors affect enzyme action and how can one reduce this?
If a inhibitor has a shape similar to that of the substrate, it can occupy the active site of the enzyme instead of the substrate, preventing the enzyme from breaking the substrate down. You can help tis by increasing the amount of substrate.
166
Name two examples of competitive inhibitors and their substrates,
Malonate can inhibit the breakdown of succinate
| Penicillin can inhibit the enzyme transpeptidase.
167
What are non competitive inhibitors and how do they affect enzyme action?
Non competitive inhibitors bond with the enzymes at a site that is not the active site, but does cause the enzyme to change shape. Therefore, the substrate can still fit the active site, but not in a way that it can form a complex and be broken down.
168
What is the structure of an ATP molecule?
ATP has a chain of three phosphate groups, bonded to a ribose sugar molecule and an adenine base.
169
What sort of molecule is ATP?
A nucleotide
170
Why is ATP a good energy store?
Becuase of its three phosphate groups, which are bonded unstably, so can easily be broke apart and release a considerable amount of energy.
171
What is the equation for the hydrolysis of ATP?
ATP + Water → ADP + Phosphate Molecule + Energy
172
Name 5 uses of ATP?
- Metabolic processes like forming starch from glucose or amino acids from peptides
- Movement (e.g. providing the energy for muscle contraction)
- Energy needed for Active Transport
- Secretion: ATP is needed to form lysosomes
- ATP can lower the activation energy of certain molecules, increasing reactivity
173
What is the role of DNA Helicase in DNA replication?
DNA Helicase is responsible for separating the two strands of DNA by breaking the hydrogen bonds between them.
174
What is the role of DNA Polymerase in DNA replication?
Helps bind the loose nucleotides to the DNA strand in semi-conservative replication.
175
What enzyme is used in transcription of DNA into Pre-mRNA?
RNA Polymerase
176
What is Transcription?
The process of making pre-mRNA out of a DNA template strand. in transcription, corresponding mRNA bases bond to a DNA template strand.
177
What does RNA Polymerase do in transcription?
It binds to a specific section in the DNA and breaks apart the strands to expose the bases. It also helps join the mRNA nucleotides to the template strand. It detaches itself and the fully-formed, single-stranded pre-mRNA molecule when it reaches the stop codon.
178
What is a stop Codon?
A specific codon within DNA bases that cause the RNA polymerase to stop bonding the bases and detach the now formed pre-mRNA molecule.
179
How is DNA conserved in transcription?
the DNA double helix is split into separate strands by RNA Polymerase. The bases are then used to organise the pre-MRNA transcription to have corresponding MRNA bases. After the pre-mRNA has been coded, the DNA strand separates and rejoins it's other strand, forming a whole molecule again.
180
What two types of DNA are there?
Exons and Introns
181
What are Introns?
DNA that does not code for the synthesis of proteins.
182
what is the difference between pre-mRNA and mRNA?
pre mRNA contains exons and introns, but mRNA only contains exons.
183
What is Splicing?
Splicing is when pre-mRNA is converted into MRNA by removing the introns and splicing the exons together.
184
How do Prokaryotes use splicing?
They don't. Prokaryotes do not have introns so they do not require splicing.
185
How do mutations relate to splicing?
Mutations can effect the splicing of pre-mRNA.
186
What causes Alzheimer's?
Alzheimer's is caused by splicing failures, as introns are left in the mRnA. Therefore, Non-functional polypeptides are made.
187
What is translation?
The process by which the codon sequence in the RNA molecule is is converted into an amino acid sequence.
188
How are nuclear pores important in translation?
the mRNA leaves the nucleus via the nuclear pores, then synthesizes a polypeptide.
189
How are ribosomes important in the translation of mRNA?
during translation, a ribosome will attach to the start codon of the mRNA. Ribosomes have 2 codon binding sites so two tRNA with relevant anticodons bind to the molecule.
Once these two tRNA molecules have bonded together (using an enzyme and ATP) the ribosome then moves along the mRNA to the next codon, and stops when it reaches the stop codon (when the polypeptide chain is formed).
190
How is tRNA used in translation?
tRNA is very important as it has an anticodon binding site as well as an amino acid on each end of one molecule. AS ribosomes have two codon bonding sites, two tRNA molecules bond to it and the mRNA at one time. A peptide bond then forms between the 2 amino acid on the tRNA molecules. They do this using an enzyme and ATP. As the ribosome moves onto the next codon, the first tRNA and it's amino acid is released, while a new tRNA arrives at the next codon, and it's amino acid binds to the second tRNA molecule. This continues until all the tRNA molecules and their amino acids are released and a polypeptide chain is formed.
191
What is post-translational modification?
Proteins often need to be altered before they become fully functional. They can be modified other enzymes after translation to make sure they function.
192
What happens when a protein is post-translationally modified?
The polypeptide chain made in the translation is usually coiled or folded to form it's secondary structure, this structure is then folded to produce the tertiary structure, and (if quaternary structure is required), additional polypeptide chains are linked to this structure.
193
What sort of proteins does active transport require?
Carrier Proteins
194
What are the two substructures in gills and how do they connect?
The gill filaments and the gill lamellae. The Gill filaments look like filaments, or the tentacle-like parts of an anemone. The gill lamellae are located on these filaments, sticking up at a right angle to the filament.
195
What is the countercurrent flow principle?
In order for sufficient gas exchange to occur in fish, the flow of deoxygenated blood and oxygenated water must be in opposite directions.
196
Why is the countercurrent flow principle a good adaptation for gas exchange (or superior to concurrent flow)?
In fish, oxygen is gained by diffusion from surrounding water into the bloodstream. If the two streams are going in seperate directions, there will be less steep diffusion gradient, and the reaction will reach equilibrium at a higher oxygen saturation level because of this, as the oxygen saturation levels will increase similarly, meaning more oxygen can be exchanged. In concurrent flow there is a larger concentration gradient, meaning oxygen is exchanged too quickly, and the reaction will reach equilibrium sooner, at a lower oxygen saturation. This means less oxygen is absorbed.
197
What is a substitution of bases mutation?
When a pre-existing nucleotide in a DNA molecule is replaced with a different nucleotide with a different base. This will disrupt the sequence of codons and will therefore cause a different amino acid to be produced.
198
What effect will substitution of bases mutation have on the final polypeptide?
It will have one different amino acid due to the replacement of one base, and the disruption of the codon sequence because of this. This could possibly affect the tertiary or quaternary structure of the protein.
199
What is deletion of bases mutation?
When a single nucleotide is deleted from the structure of the DNA, causing the polypeptide it is part of to lose its function.
200
What effect will deletion of bases mutation have on the final polypeptide?
The final polypeptide might not function properly as the deletion of one nucleotide results in the deletion of one base, meaning the bases in each of the triplets that code for an amino acid will be changed, as the bases will have all moved up the sequence by one base. This will change the secondary structure, and may later affect the tertiary and quaternary structure.
201
What is a chromosome mutation?
When either the number of chromosomes or structure of the chromosomes are changed.
202
What 2 forms are there of chromosome mutations?
Changes in number of whole sets of chromosomes (i.e. in polyploidy) and changes in the number of individual chromosomes (i.e. homologous chromosomes not separating properly).
203
Describe the difference between the 2 forms of chromosome mutation?
If there is a change in the number of chromosomes, there is an irregular number of sets of chromosomes throughout the body, in all its nuclei, and usually occurs in plants. If there is a change in the number of individual chromosomes only affects one specific chromosome, but still presents itself in every body cell.
204
From top to bottom, describe the structure of a plant tissue.
Waxy Cuticle, Upper Epidermis, Spongy Mesophyll, Vascular Bundle, Lower Epidermis (with guard cells and stomata), Waxy Cuticle.
205
What is the analogy you use to remember leaf tissue structure?
A cheese and burger-sausage ception sandwich (obvi plant based version).
Top waxy cuticle= top bun
Upper Epidermis= smooth american cheese (just there for protection, adds no taste (or special function))
Palisade Mesophyll- A lettuce leaf
Spongy Mesophyll- A spongy tofu "burger", full of air pockets.
Vascular Bundle- Veggie Sausage (in the tofu burger)- contains different dead and alive beans (Xylem and Phloem)
Lower Epidermis- Special, emmental style soya cheese, with holes (stomata) and herb bits (guard cells)
Bottom Waxy Cuticle- Lower Bun
206
What does the top and bottom waxy Cuticle do?
It waterproofs the leaf and reduces water loss. The lower waxy cuticle contains the stomata.
207
What does the upper epidermis do?
literally just protects the cell.
208
What is the role of Palisade Mesophyll?
It is the site of photosynthesis, contains a lot of chloroplasts.
209
What is the role of Spongy Mesophyll?
Increases the surface area of the cell, as it contains many air pockets, and circulates the gas.
210
What is the role of the Vascular Bundle?
Contains Xylem and Phloem tissue, to transport water and minerals. It is running through the spongy mesophyll.
211
What is the role of the lower epidermis?
Contains the guard cells and stomata, so is essential for gas exchange. It also protects the cell.
212
What is the role of the stomata?
Where uptake of gases from the air occurs. It does this due to the two guard cells beside it opening and closing.
213
How does the guard cell open and close the stomata?
If the two guard cells on either side of the stomata are turgid, the stomata will be open.
214
What is the role of the stomata?
Where uptake of gases from the air occurs. It does this due to the two guard cells beside it opening and closing.
215
How does the guard cell open and close the stomata?
If the two guard cells on either side of the stomata are turgid, the stomata will be open.
216
what are three reasons that Humans need such a large volume of Oxygen to be taken up by the lungs?
Because we are large organisms, we have many living cells that require the oxygen
Because we maintain a relatively high body temperature, so we have high metabolic/respiratory rates.
217
How thick is the wall of each alveolus? Why is this helpful?
The wall of each alveolus is never more than 0.3μm. This allows the diffusion pathway between the air in the lungs and the blood in the capillaries to be very short.
218
How many alveoli are there in each lung? How is this useful?
There are 3 million alveoli in each lung. This creates a very large surface area, so a smaller surface area to volume ratio, which increases the rate of diffusion. The mount of area for gases to diffuse across is useful.
219
What is the total surface area of alveoli in the lungs?
70㎡
220
How are the capillaries useful for diffusion from the alveoli (aside from the obvious reasons)?
Each alveolus is covered by a dense network of pulmonary blood capillaries. As deoygenated blood flows through these capillaries, and the air in the alveoli is oxygenated, this helps create a concentration gradient. They also help create a large surface area.
221
Where do the pulmonary capillaries surrounding the alveoli run to/from?
they either lead to the pulmonary artery or the pulmonary vein. The capillaries carrying deoxygenated blood lead to the pulmonary artery (go away from the heart), while the capillaries carrying the newly fortified blood lead to the pulmonary veins (go towards the heart).
222
How do red blood cells function in a way that encourages gas exchange in the alveoli?
As the red blood cells from the pulmonary artery/vein pass through the capillaries on the alveoli, they slow down, allowing them to spend more time in the capillaries, resulting in more diffusion.
223
What is inspiration?
breathing in
224
What is expiration?
breathing out
225
What role does the diaphragm play in inspiration?
The diaphragm contracts and moves downwards.
226
What role do the external intercostal muscles play in inspiration?
The intercostal muscles (muscles between the ribs) contract, causing the ribcage to move up and out.
227
How is air sucked into the lungs during inspiration?
When the diaphragm contracts and move downwards and the intercostal muscles cause the ribcage to move up and out, the volume of the lungs increases, causing there to be an excess of empty volume, so the air pressure decreases, so in order to reinstate the air pressure, air is drawn in.
228
How is water used in the alveoli structure?
The inner surface of the alveoli has a thin layer of water on it. This makes sure that the surface the gases diffuse across is always moist, so any gases can be dissolved before entering the bloodstream.
229
What role does collagen play in the alveolus structure?
Alveoli are surrounded by a collagen cable. This allows the alveoli to stretch and shrink back to shape, which assists in pulling in and pushing out air.
230
How many daughter cells does meiosis produce?
4 (usually 2 in mitosis)
231
Name two functions of meiosis?
It helps us turn diploid cells into haploid cells, which is required in making gametes for sexual reproduction. It can also cause genetic variation.
232
What happens in meiosis 1 (first division)?
The homologous chromosomes pair up and their chromatids wrap around each other. The homologous pair then separate, so there is one one chromosome from the pair in each of the daughter cells (that are now diploid) .
233
What happens in meiosis 2 (second division)?
In each daughter cell (which is now haploid), the two chromatids in the chromosome are pulled apart. When the daughter cells are formed, there is now one chromatid in each of the four daughter cells.
234
How is genetic variation via meiosis helpful?
Offspring of sexual reproduction can have genetic variations that can provide adaptations that improve chances of survival.
235
What are the two methods for genetic variation via miosis?
Independent segregation of the homologous chromosomes and crossing over ( which creates new combinations of maternal and paternal alleles)
236
What is one way genetic variation via mitosis can be harmful?
It can lead to genetic diseases/disorders such as down syndrome.
237
What is nondisjunction?
Nondisjunction is where chromosomes fail to separate in meiosis. This can either be due to the homologous chromosome pair failing to segregate into individual chromosomes in meiosis 1 or can be due to the chromatids from these chromosomes failing to separate during meiosis 2. This will create a gamete/daughter cell with the wrong number of chromosomes .
238
Why can nondisjunction cause disease?
Nondisjunction produces gametes and offspring with the incorrect number of chromosomes. This embryo may die as of this, be severely impacted or carry a genetic disease.
239
What is a gene locus?
A fixed position on a chromosome that is occupied by a gene.
240
What are homologous chromosomes?
A pair of chromosomes, one maternal and one paternal, that have the same gene loci.
241
What happens during crossing over?
During meiosis 1, one of the homologous chromosomes in a pair touches the other. These chromosomes then become twisted around each other, and break off parts of the chromosome. when recombination occurs, the broken off section from one chromosome will attach to the opposite chromosome in the pair, so this chromosome now has a small section of the other chromosomes genetic material in it's structure.
242
What happens during Independent Assortment/Segregation?
In meiosis, one chromosome from each homologous chromosome enters the gamete (that create daughter cells), and which chromosomes/chromatids enter the daughter cells is dictated by how the chromosmes are arranged on the equator of the cell. The way these are ordered dictate which information enters the daughter cells.
243
How many different ways and combinations of chromatids and chromosomes can enter the daughter cells?
There are 2²³ different ways that our chromosomes could separate into daughter cells.
244
How can mutation increase genetic diversity in a population?
Many mutations can have no effect on an organism. However, some mutations result in new alleles of a gene, that can increase the genetic diversity of a population. If a genetic mutation causes an adaptation for survival, this may diversify and eventually become the majority for a population.
245
How would a random mutation affect natural selection of an organism?
This mutation could cause a beneficial survival adaptation, that would result in the organism having an advantage over others in the population. These specimen will be stronger/have more access to resources. They would therefore be more likely to survive, reproduce and pass their mutated genes down. As the superior gene is passed down over time, it will increase the frequency of the gene in the population, so less of the population have the original, mutated gene.
246
What are polygenes?
Multiple genes that make up for one specific characteristic. These characteristics are usually more influenced by the environment than by a single gene (i.e. obesity or alzheimers)
247
how does environment affect polygenes?
The environment of an organism can cause polygenes to be affected and for the organism to vary from the mean of the population in this specific characteristic (e.g. not being the mean height).
248
What are the two different types of selection?
Stabilising Selection and directional selection.
249
What is stabilising selection?
In stabilising selection, the average individuals (e.g. average height in a population (5ft 4 women)) are the best adapted for survival. Extreme levels of this characteristic can cause complications (e.g. crazy height or dwarfism can cause health risks), so the average tend to survive better.
250
What is directional selection?
Organisms with extreme characteristics in there phenotype compared to the rest of the population (like one giraffe having a long neck) are best adapted for survival. As they have the outstanding characteristic, they will have superior access to resources (i.e. the tall leaves) over the rest of the population.
251
What are the three types of adaptation?
Anatomical, physiological and behavioral.
252
What is anatomical adaptation?
A adaptation that changes the physical features of an organism in order to help it survive.
253
What are physiological adaptations?
Metabolic or physiological changes in an organism e.g. venomous or poisonous skin/glands.
254
What are behavioral adaptations?
behaviors we evolve to help us survive, e.g. parental attachment or birds flying south for the winter.
255
what do the salivary glands do?
They secrete saliva to help lubricate the food for mastecation and digestion. They also produce salivary amylase.
256
what does the stomach do?
It stores and digests food. It especially breaks down proteins, as the stomach's contents has a low pH, so the acid easily breaks up the protein. It has sphinctor muscles at each end to allow it to open for food and keep the stomach acid inside when closed.
257
what does the pancreas do?
The pancreas is a large gland that secretes pancreatic juice which helps digest food after it leaves the stomach. The pancreas contains proteases, lipases and pancreatic amylase.
258
what is peristalsis?
The process by which food moves through the digestive system by the contraction of muscles.
259
What is bolus of food?
food after it is passed through the digestive system.
260
What does bile do?
Bile neutralises the hydrochloric acid in the stomach and contain bile salts that emulsify lipids. It is secreted from the gall bladder.
261
what does the ileum do?
secretes digestive enzymes and has a massive surface area due to the epithelial tissue lining being covered in villi (that are covered in micro-villi).
262
what does the large intestine do?
It absorbs water, in order to re-absorb the water released by digestive enzymes.
263
How is the saliva important for breaking down carbohydrates?
The saliva contains salivary amylase. In the breakdown of carbohydrates through the digestive system, this amylase breaks down starch into maltose ( a disaccharide).
264
How is the pancreas important for breaking down carbohydrates?
Pancreatic amylase is secreted by the pancreas into the ileum. When maltose molecules pass through the ileum, this pancreatic amylase breaks down the maltose into alpha glucose.
265
How are alkaline salts used in the digestion of carbohydrates?
Alkaline salts are secreted into the pancreatic juice in order to make sure that the pancreatic amylase that digests carbohydrates in the digestive system is in an environment with the correct pH.
266
How do lipases digest lipids?
By breaking the ester bonds.
267
What products are made when lipases break down lipids?
The lipid (usually a triglyceride) releases fatty acids and monoglycerides (in the case of triglycerides, two fatty acids and a monoglyceride)
268
What are monoglycerides?
Monoglycerides are a glycerol molecule bonded to a single fatty acid.
269
How are bile salts used in lipid digestion?
Bile salts emulsify the lipids, meaning they break the lipids into micelles. This allows the lipases to work more effectively on the fat.
270
What enzyme breaks down proteins?
Peptidases
271
Name two carbohydrases
Salivary amylase and pancreatic amylase
272
What are the three different types of peptidases?
Endopeptidases, exopeptidases and dipeptidases
273
What do endopeptidases do?
They break down peptide bonds in the control region of the protein, creating smaller polypeptide chains.
274
What do exopeptidases do?
They hydrolyse the peptide bonds between the peptide molecules in the peptide chain.
275
What do dipeptidases do?
They hydrolyse the peptide bonds in the dipeptide molecules separated from the polypeptide chains by exopeptidases to release amino acids.
276
Why are dipeptidases different from endopeptidases and exopeptidases?
Dipeptidases are membrane bound. They are attached to the epithelial cells on the wall of the ileum.
277
What is the basic structure of a villus?
The outer epithelial cells cover the vills, creating a barrier. This encases a lacteal surrounded by capillaries that absorb glucose and amino acid.
278
What does the lacteal do?
The lacteal absorbs fatty acids and glycerol from digestion. They are lymphatic vessels.
279
How are micelles from triglycerides transported in the epithelial cells in the ileum?
The micelles diffuse across the cell surface of the epithelial cells in the ileum. They are then taken to the endoplasmic reticulum of the epithelial cells and are reassembled into new triglycerides. These are then transported into the golgi apparatus, where they associate with cholesterol and lipoproteins to for chylomicrons. These are then ejected out of the cell and into the lacteal via exocytosis in order to later be absorbed into the bloodstream.
280
Name four features of red blood cells
They are flexible in order to allow them to fit through capillaries
They are missing a nucleus to allow more room for oxygen
It is bi-concave, to create a larger surface area and increase absorption
They are stored in the bone marrow
281
What is the structure of haemoglobin? (ions, chains and shape)
The globular protein has a quaternary structure, with four polypeptide chains and containing four iron ions.
282
How is haemoglobin used in red blood cells?
It is the molecule in red blood cells that allows for the cell to carry respiratory gases (like oxygen).
283
How is haemoglobin specialised for oxygen storage?
Haemoglobin has an affinity for oxygen, it can carry four oxygen molecules, as they can easily bind to the four iron ions haemoglobin carries.
284
How are concentration gradients used in the passage of oxygen into the haemoglobin of red blood cells?
Oxygen can move from the lungs to the blood plasma to the red blood cells because of a concentration gradient (lower concentration in the red blood cells). In order to maintain this oxygen is stored in the red blood cells as oxyhaemoglobin, as the oxygen binds to the haem group of the haemoglobin. Therefore, their is oxygen in the blood plasma and oxyhaemoglobin in the red blood cell, so the concentration gradient is still maintained.
285
How does oxygen bind to haemoglobin?
The oxygen binds to the iron ions in the "haem" group of the haemoglobin.
286
What is pO2?
The amount of oxygen in the lungs is referred to as it's partial pressure for oxygen (pO2) or it's oxygen tension.
287
How does pO2 relate to oxygen absorption?
When the pO2 is high, more oxygen and haemoglobin come in contact. Therefore, the higher the pO2, the more oxyhaemoglobin is created.
288
What is the pO2 like in respiratory tissue?
The pO2 is low
289
what happens to haemoglobin at a low pO2?
At a low pO2, oxygen dissacociates from the haem droup of oxyhaemoglobin and releases oxygen (e.g. in respiring tissue). At low pO2, lots of oxyhaemoglobin is formed at high pO2, oxyhaemoglobin is broken down.
290
What is phlogeny?
The evolutionary relationship between organisms
291
What is courtship behavior and why is it important?
Behaviors animals exhibit to help attract a mate. It is essential for survival, and allows the individual to identify a mate of their species who is capable of breathing, form a bond with their mate and synchronise mating.
292
What is phylogenic classification?
A way in which species are grouped based on evolutionary origins and relationships.
293
What are taxons and what is their use in phylogentic classification?
Taxons are smaller groups of a type of organism within the larger type of organism (i.e. genus within family, or species within genus--- i.e. the species aye aye within the genus of lemurs).
294
What is the mnemonic for taxonomy?
Dodgy king prawn curry or fat greasy sausage------
| Domain, Kingdom, Phylum, Class, Class, Order, Family, Genus, species
295
Describe the binominal system?
To write the name of a species binominally, the first is the genus (aka the genetic name) and the second name is the species.
296
WHat three ways is Carbon Dioxide transported through the circulatory system?
+ DIssolved in the blood (5% CO2 in the bloodstream)
+ Associated with haemoglobin to form a molecule called carbaminohemoglobin (10% CO2)
+ Dissolved into carbonic acid in the blood plasma
297
How can hydrogen affect the formation of oxyhaemoglobin?
H+ ions can bind to the FE2+ ions on the Haem group of haemoglobin. These hydrogen ions therefore compete with the oxygen to bind to these ions.
298
What is carbonic acid made of?
Hydrolysed CO2
299
How do we calculate the number of chromosome combinations in the daughter cells produced in sexual reproduction?
(2 ᷠ )² - Where "n" is the number of homologous chromosomes.
300
How does crossing over affect the number of chromosome combinations possible in daughter cells?
It greatly increases it as it causes there to be new genetic material within the homologous pair.
301
define genetic diversity
The total number of different alleles in a population.
302
What is an example of a species with reduced genetic diversity and how can this effect the survival of that species?
Genetic diversity is reduced when a species has fewer different alleles. These "different alleles" could be controlling specific characteristics, that could affect how the specimen survives environmental change. Specimen with this different allele and special characteristic may be more likely to survive harsh environmental conditions and changes.
303
How does genetic diversity effect natural selection?
Genetic diversity allows for many different alleles within a population, which also allows for many different interspecific characteristics, which could be used to adapt to harsh conditions. This allows natural selection to occur, as the animals without this adaptation would most likely die, while the allele-carrying specimen would produce offspring that also had the allele, increasing the frequency of it in the population.
304
What occurs during diastole of the heart?
Blood fills the atria from the pulmonary vein and the vena cava. Therefore, the pressure in the atria increases. The atrioventricular valves open when the pressure in the atria reaches a certain threshold, causing the blood to naturally drop into the ventricles due to gravity. At this point, the semi-lunar valves are closed.
305
What occurs during Atrial systole?
(after diastole causing the atria to fill up with blood, and the atrioventricular valves have closed) The atrial walls contract, the atrioventricular valves open and blood flows into the ventricles (whose walls are relaxed at this point) T this point, the semi-lunar valves are closed, in order to prevent backflow.
306
What occurs during Ventricular Systole?
The ventricle walls contract, after blood has been pumped into them during atrial systole (so the atrioventricular valves are now closed to prevent backflow into the atria). This causes pressure to build up in the ventricles. Once the amount of pressure in the ventricles exceeds the amount of pressure in the aorta and pulmonary artery, the blood is pushed into these arterial vessels via the muscular ventricle wall.
307
What is the role of the Vena Cava?
The vena cava brings blood to the heart. Specificallym it brings deoxygenated blood to the heart from all respiratory tissues (except the lungs). It supplies blood to the right atrium. The vena cava can also contain pocket valves.
308
What is the role of the Aorta?
The aorta is one of the main arteries in the body. It carries blood from the left ventricle to arterioles travelling to respiring tissue. They contain semi-lunar valves to prevent backflow.
309
What is the role of the Pulmonary Vein?
The pulmonary veins are connected to the left atrium. They bring oxygenated blood from the lungs to the heart. The actual structure of the vein is similar to that of the vena cava (same layers of tissue as the artery, but with thinner elastic and muscular layers and a wider lumen). They are supplied with oxygenated blood from the capillaries in the alveoli, and can contain pocket valves.
310
What is the role of the Pulmonary Artery?
The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. It has similar structure to the Aorta (tough and fibrous outer layer, thick muscular walls, thick elastic walls and endomorphic layer with small lumen).
311
Where can we find the right atrioventricular valve?
Between the right atrium and the right ventricle.
312
Where can we find the left atrioventricular valve?
Between the left atrium and the left ventricle.
313
What are the walls of the right and left atrium like?
The walls of the atria are quite thin and elastic. These allow them to stretch and contract as they collect blood.
314
What is the difference between the walls of the left and right ventricle?
The left ventricle has much thicker, more muscular walls, as it must pump blood at high pressures into the aorta, in order for the blood to reach everywhere in the body, including extremities.
315
What is the general structure of an artery?
The arteries have thick muscular walls, thick elastic walls, a thin and smooth layer (to reduce friction and allow smoother blood flow) and a small lumen. The muscular walls allow the arteries to contract to push blood through the vessels. The small lumen is used to maintain high pressure. The arteries can contain arterial valves (such as the semi-lunar valves in the aorta), but usually just in the heart.
316
What is the general structure of a vein?
They have similar structure to the arteries, but have thinner muscular and elastic walls, as well as a larger lumen. Thy therefore do not contract as much, and have lower pressure within the vessels, so contain valves to prevent backflow (such as pocket valves).
317
What is the general structure of a capillary?
Capillaries are small vessels, with walls that are only one cell thick. They are highly branched and have small pores in their walls, called endothelial cells. This is so plasma can leak out of these pores (which is one way the pressure remains so low in the capillaries).
318
What is tissue fluid?
Tissue fluid is a watery liquid that contains glucose, amino acids, fatty acids, ions and oxygen. Tissue fluid carries these substances TO the tissues and carries away carbon dioxide and other waste material.
319
How can hydrostatic pressure result in tissue fluid?
The pumping of the heart can cause the capillaries to have high, hydrostatic pressure. In order to combat this, blood plasma leaves the capillaries via pores. This blood plasma contains tissue fluid. (However, this outward force created by the hydrostatic pressure is contested by hydrostatic pressure outside the capillaries and the water potential gradients).
320
What do the ends/walls of the tubular phloem tissue made out of?
Sieve plates
321
What are the branch-like structures in the lumen of phloem tissues?
Sieve tube elements
322
What is one weakness of sieve tube elements?
SIeve tube elements can not keep themselves alive as they can not respire for themselves, so have to be aided by companion cells which respire for them.
323
What do phloem tissues transport?
Phloem tissue transports solutes (carbohydrates such as sucrose) made in the sources to the sink cells.
324
What type of transport is phloem tissue involved in?
translocation
325
What two substances (solutes) can be transported in translocation?
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soluble carbohydrate (such as sucrose)
Hormones
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326
What are the two things that ensure that translocation occurs FROM the source cells TO the sink cells?
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Concentration gradient (there is always a high concentration of the solute in the source cells than in the phloem vessel or the sink cells)
Pressure-
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327
What is a potometer?
An apparatus used to measure the the rate of transpiration
328
Why is it unexpected that xylem cells are so strong? What makes them strong?
They are dead, empty cells, so would be expected to be weak, but they are strengthened with lignin.
329
What occurs in the mesophyll cells during transpiration?
The water vapour accumulates in the spongy mesophyll tissues/air sacs in the leaves. This vapour then leaves he cell via the stomata, once they open. The water in the leaves is then replaced by water drawn up the plant by the phloem cells.
330
What is cohesion?
A force resulting from attraction between molecules of the same substance- e.g. between the negative and positively charged ions in different water molecules, causing them to stick together.
331
What is adhesion?
A force resulting in attraction between molecules of different substances, like when water molecules stick to the cell walls of the wall of the cells that make up xylem tissue.
332
How are cohesion and adhesion important in the theory of transpiration pull/the cohesion-tension theory?
Water is drawn up and out of the xylem vessels, ou of the stomata. The tension therefore creates a water-potential gradient, drawing more water up the vessel. The water is drawn up continuously, due to cohesion between the molecules, and the water does not drop down the vessel (as gravity would suggest) due to adhesion between te water molecules and the vessel walls,
333
What evidence is there to support the idea of cohesion-tension theory?
- Changing rates of transpiration can cause the diameter of the trunks, resulting in expansion due to the pressure of water in the xylem tubes
- If a xylem vessel is broken and air enters it, the tree can no longer take up water.
- When a xylem vessel is broken, it does not leak. If the movement of the water was just due to pressure, the water would be expected to leak, and the lack of leakage shows that water movements is more because of cohesion-tension.
334
How is tension created in transpiration?
When water is released out the stomata, it creates tension (negative pressure). This creates a lower water potential at the end of the xylem (before the stomata), which creates a water potential gradient that draws the water up the plant.
335
briefly describe how one would use a potometer to test the rate of transpiration
The potometer is filled completely with water, ensuring there are no air bubbles.
A leafy shoot is fitted inside it whilst still submerged in water.
An air bubble is introduced into the capillary tube
As the water is transpired out of the plant, the bubble will be moved along the capillary tube. The distance moved indicates the rate of transpiration.
336
What is the definition of forced expiratory volume?
maximum volume of air that can be breathed out in one second.
337
What is the definition of tidal volume?
It is the volume of air in each breath
338
What happens at the arterial end of a capillary to produce tissue fluid?
Water moves out of the capillary, glucose and oxygen move out of the capillary and hydrostatic pressure inside the capillaries is higher than the hydrostatic pressure in the tissue fluid.
339
What makes a lipid saturated?
If there are no carbon to carbon double bonds, so all the carbon atoms are linked to the maximum number of hydrogen ions that is possible.
340
How can a lipid be mono-unsaturated or polyunsaturated?
If there is a single double bond it is monounsaturated, if there are multiple double bonds, it is polyunsaturated.
341
What type of molecule is water (relating to poles)? How does this make it useful?
It is a polar molecule that can act as a universal solvent.
342
What are 3 ways that specific and non-specific immunity differ?
- Non-specific immunity occurs in all organisms, is faster than specific immunity and is the same for all pathogens.
- Specific immunity occurs only in vertebrates, has a slower response and is specific to each pathogen.
343
What are the stages of phagocytosis?
- The phagocyte detects and moves towards chemicals released by a pathogen
- Receptors on the phagocyte attach to chemicals on the surface area of the pathogen
- Pathogen is engulfed into a vesicle which is then carried to the phagosome, which then fuses with the phagosome and releases the pathogen into it.
- Lysosomes are then released, which release lysozymes, which then breaks down the pathogen
- The hydrolysed products are then absorbed by the phagocyte
