Random questioning Flashcards
1
Q
Explain the process of DNA replication
A
- DNA double helix must first be unzipped and the hydrogen bonds between complementary base pairs broken. (DNA helicase)
- The exposed single-stranded DNA acts as a template to which free nucleotides can pair through complementary base pairing.
The enzyme DNA polymerase then joins the nucleotides together through condensation reactions.
This creates phosphodiester bonds between adjacent nucleotides producing a new sugar-phosphate backbone.
The action of DNA polymerase results in the synthesis of two identical molecules of DNA.
Each molecule is composed of one old strand and one new strand, and so the method of DNA replication is semi-conservative.
2
Q
What can be used as evidence for proving the semi-conservative replication of DNA?
A
- E. colibacteria were grown on a medium containing only 15N. These bacteria only incorporated 15N into their DNA
- A control colony of bacteria was also grown on a medium containing the lighter 14N. These bacteria only incorporated 14N into their DNA
- Some bacteria were then transferred from the 15N medium to the lighter14N medium
- The bacteria were grown for enough time to undergo one round of replication
- The DNA of all three bacterial colonies was extracted
- The mass of the DNA molecules was compared by centrifuging the extracted DNA in a special solution. The heavier the DNA, the nearer the bottom of the tubeit collected
The results were as follows:
• The light DNA (control colony grown in 14N medium) collected in a band near the top of the centrifuge tube
• The heavy DNA (parent colony grown in 15N medium) collected in a band near the bottom of the centrifuge tube
• The DNA from the transferred bacteria collected in the middle of the centrifuge tube
This provided conclusive evidence that each replicated DNA molecule must contain both heavy and light strands, supporting the semi-conservative replication model.
( Meselson and Stahl )
3
Q
What is ATP and what is it composed of?
A
It is a phosphorylated nucleotide composed of organic base adenine, ribose sugar and 3 phosphate groups
4
Q
What 3 ways can ATP be synthesised?
A
- during photosynthesis using light energy (photophosphorylation) occurs in chloroplast in plant cells
- by using energy from electron transfers during respiration ( oxidative phosphorylation) occurs in mitochondria in plant and animal cells
- by transferring Pi from donor molecules to ADP during respiration (substrate level phosphorylation) occurs in cell cytoplasm and mitochondria of plant and animal cells
5
Q
Explain with references to changes in protein shape how reaction with ATP might cause a channel protein to open or close.
A
ATP is often hydrolysed by channel proteins to form ADP and Pi releasing energy.
ADP and Pi have different charge profiles to ATP’s so the hydrolysis reaction could cause the channel protein to open or close because ADP and Pi could interact with the ionic bonding in the proteins tertiary structure, affecting the 3D shape.
The released energy could also affect the secondary or tertiary bonding in the protein.
6
Q
Explain how DNA polymerase utilises triphosphate in the replication of DNA
A
Phosphodiester bonds must be formed between adjacent free acitivated nucleotides in DNA replication.
The activated nucleotides are nucleoside triphosphate.
The formation of the phosphodiester bonds requires energy, which is provided by the hydrolysis of the “unstable” covalent bonds between the phosphate groups of the activated nucleotides.
7
Q
ATP serves as a great immediate energy source because?
A
- Energy can be supplied to the cell in optimal amounts
- ATP hydrolysis is a single reaction that occurs easily due to unstable bonds - Energy can be supplied to the cell in optimal amounts
- ATP hydrolysis only releases a small. manageable amount of energy so less is wasted as heat
8
Q
What can the energy released by ATP hydrolysis be used for?
A
To drive biological processes :
- metabolic processes (synthesise biological molecules e.g carbohydrates_
- Active transport (ATP is used to change the shape of carrier proteins
- Movement ( ATP is used for muscle contraction)
- Secretion (ATP is needed for the formation of vesicles which will then be released from the cell)
- Molecule activation (ATP is used to phosphorylate other molecules to make them more reactive)
9
Q
Tears have a high concentration of salt in them,
describe how tears might act as an antibacterial (using knowledge of water potential)
A
- Tears could have a water potential thats more negative than the bacteria.
- When bacteria comes into contact with tears, water may therefore move out of the bacteria by osmosis.
- This can affect rates of bacterial metabolic reactions hitch can slow or stop growth and/or survival
10
Q
Why do the eyes require tear fluid, but it isnt present on the skin?
A
The skin is protected by a layer of dead cells but the outermost layer of cells in the eye is alive.
11
Q
Cigarette smoke contains chemicals that can paralyse cilia. Explain why smoking leads to increased lung infections.
A
- Cillia wafts mucus (which traps pathogens) up to the top of the throat so they can be swallowed and sterilised by the stomachs HCL.
- Paralysed cilia cannot move the mucus so it sits in the bronchi/bronchioles for longer giving pathogens a longer window of opportunity to infect the cells of the lung
12
Q
Explain what is meant by degeneracy in the genetic code and how degeneracy could be advantageous to organisms
A
(define degeneracy then explain how that helps)
“Degeneracy” means that different codons can code for the same amino acid. This could be protective against mutations as there is a chance a codon could undergo a mutation (base substitution) to become another coding for the same amino acid (silent mutation)
13
Q
tRNA is a very short RNA molecule made of around how many nucleotides?
A
80
14
Q
Despite tRNA being single stranded, how does it still fold into a clover leaf shape?
A
tRNA can form complementary base pairs with itself, folding into a clover-leaf shape
15
Q
What section on a tRNA molecule do the amino acids attach to?
A
One end of the tRNA molecule extends further out, with its bases faced outwards, providing a site for amino acid attachment
16
Q
How many variety tRNA molecules can bind to the mRNA codons?
A
61 mRNA codons (not 64 because 3 code for stop)
17
Q
What happens to a ribosome once an mRNA has successfully translated its polypeptide?
A
The ribosome units separate form the mRNA strand and are quickly resused for another round of translation
18
Q
Which enzyme catalyses the linkage of adjacent RNA nucleotides during transcription in eukaryotes?
A
RNA polymerase
19
Q
What is an mRNA codon?
A
Each 3 bases of the mRNA sequence that corresponds to a single amino acid
20
Q
What is required to form peptide bonds between adjacent amino acids during translation?
A
ATP is required to form the peptide bond between 2 adjacent amino acids during the process of translation t the ribosomes
21
Q
mRNA leaves the nucleus by travelling through?
A
Nuclear pores.
mRNA is much smaller than a chromosome so it can be transported form the nucleus to the cytoplasm through nuclear pores
22
Q
Which RNA base temporarily forms hydrogen bonds with adenine in a DNA sequence?
A
Uracil
23
Q
What does RNA polymerase do?
A
RNA polymerase catalyses the formation of a strand of mRNA during transcription by joining adjacent RNA nucleotides.
24
Q
What is the role of tRNA?
A
Transfer the genetic information from mRNA into a sequence of amino acids
25
The ribosome translates mRNA into the corresponding ....?
amino acid
26
What happens to the 1st tRNA molecule after the ribosome has moved forward and a peptide bond is formed between the 2 amino acids?
The ribosomes moves along the mRNA strand by exactly 3 base pairs and the 1st tRNA is released. It is free to go and bind to another amino acid in the cell, tRNAs are recycled.
27
What happens to the structure of a polypeptide after it is released from the ribosome?
It folds into a specific tertiary structure determined by the amino acid sequence.
28
Compare the structure of DNA to that of mRNA
1. DNA is double stranded but mRNA is single stranded.
2. DNA contains bases adenine, thymine, cytosine and guanine WHILST RNA has uracil instead of thymine
3. DNA has deoxyribose sugar and RNA has ribose sugar
29
Describe the process of translation
1. The mRNA associates with a ribosome by binding to the small subunit at the start codon.
2. The first tRNA molecule (carrying amino acid methionine) then binds to the start codon by hydrogen bonding.
3. The tRNA's anticodon is complementary to the mRNA start codon.
4. Once this first tRNA has bound to the start codon, the large ribosomal subunit binds.
5. The second tRNA binds as it holds anticodons complementary to the 2nd codon of mRNA, and carries the amino acid specified by that codon.
6. A condensation reaction takes place forming a peptide bond between the 2 amino acids, this also releases the methionine from the 1st tRNA
7. The ribosome then moves forward 3 bases and the 2st tRNA is released.
8. This continues extending the peptide by one amino acid each time, eventually a polypeptide will have been formed.
9. Translation stops when the stop codon is reached. (this codon has no complementary tRNA.
10. The subunits of the ribosome separate releasing the polypeptide.
30
How does cholesterol prevent the cell membrane from becoming too stiff?
Cholesterol prevents the cell membrane from becoming too stiff by preventing the phospholipids from grouping too close together
31
What is meant by. a partially permeable membrane?
It can control what passes into and out of cells. Some substances can pass through the membrane and others are prevented from passing.
32
Vaguly, how do particles cross the cell surface membrane with carrier proteins?
Carrier proteins transport specific molecules across the membrane by changing shape when the molecules bind to the protein.
33
What properties of cholesterol allow it to fit into the phospholipid bilayer?
small, and has hydrophobic and hydrophilic ends
34
What type of channels do channel proteins form?
Hydrophillic channels that allow specific water-soluble molecules to pass through the membrane
35
What is the function of cholesterol in the bilayer?
Wedges of cholesterol are inserted into the lipid bilayer to help regulate the fluidity of the membrane
36
How do components of the cell membrane move?
sideways along the membrane
37
What are 3 roles of peripheral proteins on the surface of the cell surface membrane?
cellular adhesion, recognition site, receptor molecule
38
How would proteins move in the membrane?
molecules can move laterally in the plasma membrane. This is because of the fluid mosaic structure of membranes - phospholipids and embedded proteins do not form strong or rigid bonds with each other.
39
How would the ratio of saturated to unsaturated phospholipids affect the fluidity of the membrane?
If there was higher saturated to unsaturated phospholipids in the membrane then fluidity would decrease. This is because unsaturated phospholipidsare 'kinked' preventing the close packing of molecules in the membrane decreasing the potential for compression
40
Explain what would happen to the speed of light sensing at low temperatures if the membrane of retinal cells had a low cholesterol content.
Cholesterol maintains fluidity at low temperatures. x protein and y protein must move around in order to interact and facilitate light sensing. This is quicker when the membrane is more fluid - so a low cholesterol content would slow light sensing at low temps
41
Describe the structure of the cell surface membrane with reference to the fluid mosaic model
mark 1. mention phospholipid bilayer
mark 2. describe the structure (hydrophilic polar phosphate head outwards, hydrophobic non-polar fatty acid tail inwards creating bilayer)
mark 3. mention cholesterol regulating the fluidity of the membrane
mark 4. protein channels (facilitate molecules in/out cell) carrier proteins (actively transport molecules in/out cell using ATP)
mark 5. glycoproteins and glycolipids have signalling roles
mark 6. describe how it is a fluid mosaic model
42
How do cell membranes selectively control which particles enter or leave the cell?
Channel and carrier proteins are specific to one type of particle. Cell membranes can therefore selectively control which particles can enter or leave the cell by which proteins are found on their membrane.
43
Where does tissue fluid drain?
into the lymphatic system and blood capillaries at the venous end of a capillary bed.
44
Why do foetal haemoglobin have a slightly higher affinity for oxygen than adult haemoglobin?
To ensure that the developing foetus can receive oxygen across the placenta
45
How much of carbon dioxide transported in the blood is dissolved directly in the blood plasma?
5%
46
Why does the transportation of carbon dioxide in the blood cause haemoglobin to have a lower affinity for oxygen?
The lower pH levels in the cell causes a conformational change in the tertiary structure of haemoglobin, making it harder for the oxygen molecules to bind to it.
47
What is the endothelium?
thin, inner layer of cells of the blood vessels
48
What is the role of arteries?
To carry away blood from the heart at high pressure
49
What blood vessel can help to control the flow of blood through the body?
Arterioles can contract their smooth muscle, thereby constricting their lumens. This controls the flow of blood through the body
50
From where and where to do venues deliver blood?
Venules deliver blood from the veins to the capillary beds.
51
What is the role of tissue fluid?
Animals with closed circulatory systems bathe their body tissues in tissue fluid.
Tissue fluid is used to exchange nutrients and gasses between cells of the body and the blood in the circulatory system.
52
What forces blood plasma through the capillary endothelium into existing tissue fluid?
High hydrostatic pressure
53
What causes the flow of lymph fluid in the lymphatic system?
Using a combination of hydrostatic pressure from the lymph capillaries and contraction of skeletal muscle.
54
Where is tissue fluid formed?
Arterial end of a capillary bed
55
How does the oncotic pressure of tissue fluid change from the arterial to the venous ends of a capillary bed?
It doesnt change.
| Oncotic pressure remains constant in the tissue fluid.
56
Compare the structure of arterioles to arteries
arterioles have similar structure to arteries but they are smaller and have relatively thinner muscles and elastic layers
57
Why do arterioles not require as much elastic layers / thinner muscles?
Because the blood pressure is decreasing
58
What is the main role of arterioles?
Contraction of smooth muscle (limiting the diameter of the vessel) constricts the arterioles and controls the flow of blood through the body
59
Describe the structure of capillaries
They have very thin walls consisting of just a single-celled layer of endothelium
60
Why is the lumen of capillaries narrow?
To squeeze red blood cells against the endothelium to improve transfer of oxygen.
Also the diffusion pathway of co2 or o2 is very short.
Gas / nutrient exchange is at maximum efficiency.
61
Because a lot of blood is now in contact with the capillary walls, what does this result in?
Increased resistance which greatly slows the flow of blood, reducing the pressure, saves a lot of damage in the capillary beds
62
What besides valves found in veins help push blood in the correct direction towards the heart and how?
Skeletal muscles compress the vein and pushed the blood along
63
Once exchange gases are in the body they must stay ...?
they need to stay dissolved in some solution
64
Why do exchange gases need to be dissolved in the body?
Because if they remain as gases, they will form bubbles in the blood which can impede blood flow and cause blockages
65
What is different between the contents of blood and tissue fluid?
Tissue fluid contains the same nutrients and gases that blood does but without most blood cells and proteins.
no red blood cells and no large proteins
66
What does the blood vessel walls allow to enter the tissue fluid?
```
Fluid (water)
Plasma
oxygen/carbon dioxide
nutrients
hormones
```
67
Define oncotic pressure
Refers to the amount of protein or solutes in a solution
68
Why is the oncotic pressure of the capillaries at the arterial end high and the oncotic pressure of the tissue fluid at the arterial end low?
Because there is a high volume of solutes ( different proteins nutrients and gases ) in the blood at the arterial end and low volume of solutes in the tissue fluid.
69
What resists movement of material from the blood to the tissue fluid in the capillaries?
Oncotic pressure
Because blood has large volume of solutes at the arterial end of the capillary bed, oncotic pressure forces fluid to remain within the blood to keep a balance between fluid and solutes.
70
How is tissue fluid still exerted at the arterial end of the capillary beds despite oncotic pressure resisting it?
There is a much greater hydrostatic pressure overcoming the weaker oncotic force
71
How do components begin to reenter the capillary bed at the venous end?
There is a greater hydrostatic pressure in the tissue fluid at the venous end compared to in the capillary bed at the venous end hence fluid beings to move from the tissue fluid back into the system
72
What happens at the venous end of the capillary beds?
Tissue fluid containing waste products of metabolism travels back into the blood forming blood plasma (high hydrostatic pressure of tissue fluid and low hydrostatic pressure of blood allows contents of tissue fluid to enter the capillary at venous end)
73
What happens to the excess tissue fluid?
It drains into the lymphatic system (lymphatic vessels are embedded within the capillary beds/tissue fluid)
74
What can happen if there is too much tissue fluid surrounding capillary beds?
It can cause swelling and increase the diffusion pathway
75
What is the lymphatic system?
a network of vessels and organs that help maintain the internal fluid environment of the body as well as transporting some proteins and fats
76
What is the journey of the lymphatic system?
the lymphatic systems transports lymphs around the body and eventually drains back into the blood in the chest
77
Explain how the lymphatic system flows
Through a combination of hydrostatic pressure from the lymph capillaries and contraction of skeletal muscles
78
What is the issue with lymph as a fluid
It is viscous so hard to flow
It is low pressure as there is no pump driving the movement of fluid through vessels (moves through slow capillary movement and contraction of muscles)
79
Haemoglobin can transport oxygen as its reaction is reversible, What do you call its forward and reverse reaction?
forward : association
| reverse : dissociation
80
Define dissociation
the separation of 2 molecules
| unloading of oxygen from haemoglobin
81
Describe the structure of haemoglobin
made up of 4 polypeptide chains each containing a prosthetic haem group
82
How many oxygen molecules can bind to 1 haemoglobin>
4
83
The haem groups of haemoglobin are buried/inaccessible within the structure so explain how oxygen molecules are able to bind to them.
Despite the haem groups being buried within the structure, after the 1st binding of an oxygen molecule, this creates a conformation change in the structure of the haemoglobin molecule.
The conformation change makes the haem groups more accessible to oxygen
84
Explain why in low oxygen levels there are very few haemoglobin bound to oxygen.
Because theres very little oxygen going around and its unlikely that the 1st oxygen molecule would be able to bind to the haem group buried within the structure.
So if the 02 is low then the amount of haemoglobin bound to oxygen will also be low
85
Why do different animals have different affinities for oxygen?
Because they contain different haemoglobin proteins
86
Why do animals living in high altitudes have higher affinities for oxygen?
Because oxygen is harder to find
87
Define the Bohr effect
The effect that increasing carbon dioxide concentration has on haemoglobin explaining how oxygen is released where it is needed
88
Explain how haemoglobin unloads oxygen at the tissues.
As tissue muscles respire, CO2 gets produced and it dissolved in the cytoplasm of red blood cells. (CO2 + H20 = H2CO3)
(H2CO3 reversible reaction to H+ and HC03-)
The production of H+ ions lowers the pH of the cytoplasm affecting the tertiary structure of haemoglobin.
Haemoglobin affinity for oxygen is reduced at lower pH and so oxygen is unloaded in respiring tissues
89
What protein facilitates the process of co-transport?
Carrier proteins facilitate co-transport by acting as pumps
90
Why can't facilitated diffusion alone maximise the uptake of glucose from the ileum into the epithelial cells?
FD alone cannot maximise the uptake of glucose as it can only result in equal concentrations of glucose on both sides of the epithelial cell membrane.
91
The co-transport of glucose is a type of ...?
Co-transport of glucose cannot occur without the active transport of sodium and is powered by the sodium concentration gradient.
Hence it is INDIRECT ACTIVE TRANSPORT.
92
Define active transport
Movement of particles from an area of low concentration to an area of high concentration across a cell membrane, using ATP and protein carriers.
93
Define co-transport
When the transport of one substance is coupled with the transport of another substance across a membrane.
Both substances must move in the same direction through the same protein carrier.
94
How do the glucose molecules pass from the epithelial cells into the blood?
By facilitated diffusion.
95
Co-transport of glucose can only occur when ....?
It can only occur alongside the active transport of sodium
96
Describe the sodium potassium pump transporting ions across the cell membrane
3 sodium ions removed from cell while 2 potassium ions move into the cell.
97
Co-transport uses energy from?
An existing concentration gradient set up by active transport.
98
Explain why ATP is used for active transport within the cell.
ATP contains 3 negatively charges phosphate groups covalently attached to each other.
When the bonds are hydrolysed, they release energy because these bonds are "unstable" due to the charges.
This energy is required to move substances against their concentration gradients, across a membrane I.e process of active transport
99
Describe how glucose is actively transported from the ileum into the blood.
Sodium ions are pumped forms the epithelial cells of the ileum into the blood by the sodium-potassium pump. This is an active process.
This causes the epithelial cells to have a low concentration of sodium ions, creating a concentration gradient between he cells and the lumen of the ileum, where the concentration of sodium ions is higher.
Sodium ions move into the cells down the concentration gradient via the sodium-glucose cotransporter protein, this protein transports glucose into the cell at the same time as sodium.
This means that glucose is moved against its concentration gradient.
The molecules of glucose then move into the blood by facilitated diffusion.
100
What do antigens allow the immune system to do?
Recognise different types of cells and produce a response to foreign antigens.
101
What can antibodies also be referred as?
Immunoglobulins
102
Why is the constant region of an antibody called a constant region?
Because it is the same in all antibodies and can bind to receptors present on immune cells.
103
What is formed when an antibody binds to an antigen?
Antigen-antibody complex
104
What does the binding of antibodies to the antigens on the cancer cells do?
The binding blocks chemical signals from stimulating the uncontrolled growth of cancer cells
105
What is herceptin used to treat?
Breast cancer. It is a specialised monoclonal antibody with a cytotoxic drug attached to it.
When the monoclonal antibody binds to the antigens on the cancer cell, the drug can kill it.
106
What reduces the immune response to a transplant?
Immunosuppressants
107
What does the constant region of a antibody bind to on the phagocyte?
Opsonin receptors
108
Describe how the structure of an antibody is related to its function.
Antibodies have a constant region.
This acts as a binding site for phagocytes, so helps antibodies to act as opsonins.
Antibodies have variable regions which bind specific pathogenic antigens with complementary shapes to the variable region.
The shape of the carbide region varies between antibodies.
Antibodies have hinge regions which increase their flexibility and help their role in agglutination.
109
What is cell-mediated immunity?
Recognition of antigens by T lypmphoytes and their subsequent response
110
What from T cells allow the stimulation of B cell development?
T helper cells release cell signalling molecules called cytokines to help stimulate other immune cells.
T helper cells stimulate B cells to develop and produce antibodies.
111
Why is the secondary immune response very rapid?
The secondary immune response is very rapid because clonal selection and clonal expansion are skipped due to the presence of memory cells.
112
What is clonal selection?
The process of a single B/T lymphocyte out of millions found in our body, being complementary to the antigen found on our infected body cell.
As the receptor on the lymphocyte is complementary to he shape of the specific antigen, they bind and this contact and subsequent activation is clonal selection
113
The contact between the lymphocyte receptor and antigen can be achieved either directly or indirectly, describe the difference
Direct: lymphocytes comes across the pathogenic cells in the lymph nodes. (receptors on lymphocyte bind to pathogen antigen)
Indirect: lymphocyte comes across an antigen presenting cell which phagocytsed the pathogen. (receptors on lymphocytes bind to antigen (not of pathogen) of antigen-presenting cell
114
What is clonal expansion?
The increase in the number of cells (lymphocytes) by mitotic division.
115
What is the chemical released by T killer cells to kill infected cells?
Perforin
116
What do T helper cells release to help stimulate other immune cells?
cytokines
117
How do helper T cells stimulate b lymphocytes to produce antibodies?
Helper T cells secrete cytokines which bind to specific B cells and tells the right B cells to make the correct antibodies.
118
What are T regulatory cells?
They inhibit the immune response when the pathogen has been destroyed. (prevent damage of healthy cells)
119
In what way are cellulose microfibrils arranged in the cell wall of plant cell?
The macrofibrils wrap around plant cells in multiple layers and at difference angles, providing extra strength to the plant cell wall.
120
What is starch stored in>
Amyloplasts
121
Why is the cell-surface membrane a good electrical insulator?
The selective permeability of the membrane allows it to act as an electrical insulator by preventing movement of charged ions across the cell membrane.
122
Why does a carbon-carbon double bond in an unsaturated fatty acid affect its melting point?
The double bond gives the fatty acid chain a kink(lipid molecules further apart), increasing fluidity and decreasing melting point
123
What do triglycerides provide for metabolic reactions?
They provide a good source of water for metabolic reactions as water is released when triglycerides are broken down in respiration.
124
Which property of the bilayer keeps the membrane stable?
The hydrophilic heads form 2 rows on the outside while the hydrophobic ails are sheltered in the middle.
The closed structure is stable because it avoids the exposure of the hydrophobic hydrocarbon tails to water.
125
What initiates a colour change when Benedictus reagent is used to test for a reducing sugar?
Copper (II) sulfate is reduced to copper (I) oxide
126
What 2 reagents are used in the buiret test?
Sodium hydroxide and copper (II) sulphate
127
What is a conjugated protein?
a protein that functions with other non-peptide groups attached to it
128
Which group within an amino acid donates an -OH when forming a peptide bond?
The carboxyl group donates an -OH whilst the amino group donates an -H to form a peptide bond and a molecule of water is produced
129
After forming the enzyme-substrate complex, how can the enzyme act to further lower the activation energy of the reaction?
The active site puts pressure on the substrate.
This pressure helps bonds within the substrate to break or form, allowing the metabolic reaction to occur.
130
What is an anabolic reaction?
2 substrates are being put together to form a single product
131
Where is amylase secreted?
salivary glands and the pancreas
132
Give an example of a single celled organism which uses diffusion for gas exchange
Amoeba proteus
133
Why can't insects carry out gas exchange via simple diffusion?
Their exoskeletons are too thick
134
What lines the tracheal walls to prevent them from collapsing?
Chitin
135
What is the special fluid found in tracheal systems used for?
For carrying dissolved oxygen
136
How does end-product inhibition work?
The final product inhibits enzyme function in the metabolic pathway that produces it, thus reducing the production of more end-products.
137
Why is species richness an insufficient measure of biodiversity?
Because say for example 2 fields had the same species richness so the same number of different species, but on field 1 there are many many of different species thriving but in field 2 there are only a few of each of the different species so whilst variety is still there, it isnt abundant,
138
What is polyploidy?
A chromosome mutation that occurs when the whole set of chromosomes is duplicated
139
Why does chemotherapy affect hair cells?
Chemotherapy targets cells which have a fast growth rate as tumors are fast dividing cells and it just so happens that hair cells also have a fast growth rate.
140
sodium ions play a key role in regulating osmotic pressure, how does this all plant cells to remain turgid?
Sodium ions within the plant cells lower its water potential enough so that it draws water in via osmosis causing the cell to swell/be turgid.
141
sodium ions play a key role in regulating osmotic pressure, how does this all regulate the absorption of water in the kidney?
The kidney filters blood out and when it filters out sodium, when taking back that sodium, water molecules follow with it
142
What is cardiac muscle?
A specialised type of muscle found in the walls of the heart. (can contract automatically without signal from the brain)
143
Describe the structure of cardiac muscle
It consists of branched myofibrils (cardiac myocyte) separated by intercalated discs.
144
What is fibrillation and what can it be caused by?
The uncoordinated contraction of the muscles in the heart.
muscles in the atria naturally contracts faster than muscle in the ventricles which can lead to fibrilallation.
145
What can a fibrillating heart increase the chances of and why?
a fibrillating heart pumps blood much more inefficiently and increases the chances of angina and myocardial infarction/heart attack .
(angina is heart pain due to heart struggling to pump blood around the body and the heart itself gets starved of oxygen.)
(myocardial infarction/heart attack is where part of the heart muscle actually dies and cannot be replaced because of the lack of oxygen.)
146
Describe the structure of xylem vessels
dead cells stacked end to end.
no cytoplasm or organelles and no cell walls at their ends that would slow the flow of water
lined with a waterproof coat made of lignin
147
What does the xylem transport
| ?
water and mineral ions from the roots upwards
148
Describe what a transpiration stream is
As water diffuses out of the leaf, it gets replaced by the water from the xylem vessels.
There is a constant stream travelling from the roots, through the stream and out of the leaves.
149
What are glycoproteins?
Proteins with a chain of carbohydrate molecules attached
150
What are the roles of glycoproteins?
- act as recognition sites for the immune system
- help cells adhere to form tissue
- provide stability to cell membrane
- act as cell receptors and play a role in cell communication
