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AH Biology > past paper questions > Flashcards

past paper questions Flashcards

1
Q

explain how the action of protein kinase can switch a target protein from inactive to active

A

the kinase phosphorylates the target protein, causing it to change conformation

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2
Q

explain the importance of a system being able to return the target protein to its active state

A

it allows the target protein to respond again

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3
Q

name the process where the binding of oxygen to one subunit of haemoglobin alters the affinity of the remaining subunits

A

cooperative binding

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4
Q

tissues with higher metabolic rates require more oxygen. these tissues produce more carbon dioxide, which dissolves in tissue fluids to form carbonic acid. what impact does this have on the release of oxygen?

A

the acid means there is a lower pH, which means there is a lower affinity for binding to oxygen in haemoglobin, so there is a greater release of oxygen

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5
Q

explain the term cooperativity in binding in relation to oxygen binding to haemoglobin

A

Binding (to one subunit of one
oxygen) makes the binding of
other oxygen more likely

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6
Q

Explain why the rate of uptake by GLUT transporters levels off at high
glucose concentrations

A

most binding sites on the glut transporters are filled

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7
Q

name a purpose of the sodium potassium pump

A

generates an ion concentration gradient for maintenance of resting potential in cells and neurons

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8
Q

a decrease in the activity of glucose symport proteins in the cells lining the small intestine could be caused by an increase in the…

A

sodium ion concentration in the cells

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9
Q

describe the mechanism by which a hydrophobic signalling molecule causes an effect within the target cell

A
  • diffuses through the cell membrane
  • binds to receptor which switches off transcription / binds to a transcription factor
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10
Q

how can a signalling molecule have different effects on different tissues

A

they have different transduction pathways and may have different responses to receptor binding

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11
Q

what is a peptide hormone an example of

A

a hydrophilic extracellular signalling molecule

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12
Q

why is there not a rapid increase in the transport of glucose into muscle and fat cells via glut4 in individuals with type 2 diabetes

A

the insulin receptors lose sensitivity, and the glut4 is not recruited and transported to the membrane from intracellular stores

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13
Q

explain why rod cells can function in low light intensity

A

higher degree of amplification

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14
Q

explain the importance of potassium channels in nerve transmission

A

ions flow out of the cell in opposite direction. this returns it to the resting membrane potential

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15
Q

rod cells are more sensitive than cone cells at low light intensities. how is this sensitivity achieved?

A

high degree of amplification

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16
Q

in cone cells, the light sensitive molecule retinal combines with a membrane protein to form photoreceptor proteins. name this membrane protein

A

opsin

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17
Q

name the additional wavelength range to which organisms are sensitive

A

UV

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18
Q

name the light sensitive molecule in animals that combines with the protein opsin to form photoreceptors of the eye

A

retinal

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19
Q

describe the role of bacteriorhodopsin in archaea

A

absorbs light to pump protons to generate a potential difference

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20
Q

describe the structure of spindle fibres and explain their role in the movement of chromosomes during cell division

A

cell division requires remodelling of the cytoskeleton.
spindle fibres are made of microtubules - hollow cylinders made of tubulin
they attach to chromosomes kintechores in the centromere region. they radiate from the MTOC
the spindle fibres contract and shorten and separate chromatids

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21
Q

name the globular protein of which microtubules are composed

A

tubulin

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22
Q

name the structure from which microtubules radiate

A

the microtubule organizing centre

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23
Q

state the cause of cell death during apoptosis

A

destruction of the cell by digestive enzymes / caspases

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24
Q

describe the action of caspases in cell destruction

A

they are proteases and digest proteins

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25
Q

Cholera is a disease caused by the bacterium Vibrio cholerae. It causes
severe watery diarrhoea, which can lead to dehydration and even death.
The bacterium produces cholera toxin which interferes with the control
of the CFTR protein channel by constantly activating a kinase enzyme. describe the reaction catalysed by a kinase enzyme

A

phosphorylation

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26
Q

Cholera is a disease caused by the bacterium Vibrio cholerae. It causes
severe watery diarrhoea, which can lead to dehydration and even death.
The bacterium produces cholera toxin which interferes with the control
of the CFTR protein channel by constantly activating a kinase enzyme. Explain how the production of cholera toxin by Vibrio cholerae can
lead to more water being drawn out of the epithelial cells

A

constantly activated kinase leads to constant phosphorylation of CFTR. the ion channels is always open, so there is an increased movement of the chlorine ions out of the cell.

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27
Q

alpha helices in proteins are stabilised by

A

hydrogen bonds

28
Q

what impact does an increase in temperature have on the delivery of oxygen to cells

A

the affinity of haemoglobin decreases, resulting in an increase delivery to cells

29
Q

state the cause of death in apoptosis

A

destruction of the cell by proteases

30
Q

what are factors that can increase transmission of parasites

A
  • inadequate sanitation
  • contaminated drinking water
  • high abundance of parasites
  • overcrowding of hosts
31
Q

how does patchiness arise during the development of tortoisehell cats

A

in each cell, one of two of the X chromosome inactivates, meaning only the allele on the active X chromosome is expressed.
this inactivation is random in each cell, and as the cells multiply they form patches, where the dominant allele is expressed in some cells, and recessive is expressed in others.

32
Q

state the term used to describe an individual able to produce gametes that differ in their sex chromosomes

A

heterogametic

33
Q

suggest one reason why controlling parasitic disease with drug treatment has proved to be so difficult

A

drugs toxic to parasites also toxic to human cells

34
Q

describe how complementary shape and chemistry of an enzyme and its substrate are essential to an enzymes function

A

induced fit. lowers activation energy.

35
Q

describe the role of caspases in apoptosis

A

they are proteases that destroy the cell and activate other enzymes like DNAase

36
Q

a vital stain…

A

only stains dead cells

37
Q

what would decrease haemoglobins affinity for oxygen

A

an increase in temperature and a decrease in pH

38
Q

how do black grouse mate

A

polygamy

39
Q

would improved vector control be an appropriate measure to reduce parasitic infections

A

no

40
Q

describe the mechanism by which a steroid hormone causes an effect in a target cell

A

diffuses through the cell membrane and binds to a transcription factor

41
Q

how is protein electrophoresis used to separate proteins

A

charge separates proteins in the gel on the basis of size shape and charge

42
Q

how can antibodies be used to detect the presence of proteins

A

antibody labelled by fluorescence, and this detects if the antibody has bound to the protein, showing its presence

43
Q

suggest one reason why counting latrines is an appropriate indirect sampling technique for water voles

A

species may be elusive

44
Q

describe how an environmental factor can influence the sex ration of offspring in reptiles

A

temperature of egg incubation

45
Q

explain why males are more likely to be affected by diabetes insipidus than females

A

males lack the homologous alleles on the Y chromosome so the recessive allele is always expressed.

46
Q

with reference to the red queen hypothesis, discuss the importance of sexual reproduction in defence against parasites

A

parasites benefit at the expense of the host. the host and the parasite coevolve.
in coevolution, a change in the traits of one species acts as a selection pressure on the other species.
RQ hypthesis states that species have to adapt to avoid extinction. so hosts that are better able to tolerate parasites have greater fitness and survive.
sexual reproduction generates genetic variation which provides these raw materials for genetic variation.

47
Q

explain what is meant by horizontal gene transfer

A

transfer of genetic material outwith reproduction/ within the same generation

48
Q

what are the different protein locations within the cell

A
  • polar r groups are mostly at the surface of a soluble protein
  • soluble proteins are found in the cytoplasm
  • membrane proteins are integral or peripheral.
  • some integral proteins are transmembrane, such as channels and transporters.
  • the peripheral proteins have hydrophilic r groups interacting with hydrophilic heads of the phospholipids
  • the membrane has hydrophobic and hydrophilic regions
49
Q

what are the different types of transporter proteins

A

channels and pumps are transmembrane proteins that control ion concentration and maintain concentration gradients.
different cells have different channels
movement through channels is passive
transporter proteins change conformation to transport the molecules across the membrane
this conformational change requires phosphorylation by ATP
an example of a pump is the sodium potasium pump which generations ion gradients for glucose symport.

50
Q

how do ligand gated channels open

A

by the binding of a signal molecule

51
Q

how do voltage gated channels open

A

by changes in ion concentration

52
Q

in animal rod cells rhodopsin absorbs a photon of light intiating the following cell events

A

activation of hundreds of g protein molecules
activation of thousands of molecules of an enzyme
sufficient product formation is triggered
nerve impulse is generated

53
Q

what is the benefit to the parasite if its vector lives longer

A

allows more time for reproduction

54
Q

state an advantage of using an in vivo trial

A

allows the overall effect of a drug to be observed

55
Q

why would a placebo group be included in a trial

A

to provide results in the absence of the drug

56
Q

describe an ethical issue associated with in vivo

A

right to withdraw and justification of research. informed consent.

57
Q

name the type of cell that undergoes meiosis

A

gamete mother cell

58
Q

explain the importance of potassium channels in nerve transmission

A

potassium ions flow out of the cell and return the cell to resting membrane potential.

59
Q

name the level of protein structure describing several connected polypeptide units

A

quaternary

60
Q

suggest why invasive populations are found to be composed of only parthonogenic females

A

parasite density is low

61
Q

what is a retrovirus

A

one that inserts its genome into the host genome

62
Q

if the interactions between the phospholipids on the membrane are disrupted, how could this then lead to cell death

A

would allow leakage of material in and out of th cell, which could be severe enough to lead to the lysis of the cell

63
Q

describe the chemical reaction that ATPase catalyse

A

hydrolysis

64
Q

why may something be moving into a cell against its concentration gradient

A

because the effect of the electrical potential difference is greater than that of the concentration gradient

65
Q

how can vaccinations lead to herd immunity

A

non vaccinated people are also protected

66
Q

what is meant by morphology

A

the form and structure of an organism or part of an organism

67
Q

other than morphology, what else can be used to construct a phylogenetic tree

A

protein structure

AH Biology (60 decks)

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