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Biology Revision Year 2 > Exam Questions > Flashcards

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1
Q

explain what is meant by a reflex action

A

an involuntary response to a stimulus

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2
Q

explain the type of receptor involved in pulling the hand away from a hot surface

A

thermoreceptor

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3
Q

describe the pathway taken by the nerve impulse from receptor to effector

A

sensory neurone to intermediate to motor

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4
Q

why is blood leaving the heart through the aorta at a higher pressure than blood leaving the pulmonary artery?

A

thicker muscle means stronger contraction of left ventricle

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5
Q

which nerve would scientists stimulate to cause a fall in cardiac output?

A

parasympathetic

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6
Q

why does stimulation of the parasympathetic cause a fall in cardiac output?

A

sinoatrial node sends fewer impulses, so the heart beats less often ( CO = HR x stroke volume)

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7
Q

what event in the heart causes a pulse?

A

ventricular systole

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8
Q

why is counting 20 seconds and multiplying by 3 less accurate than counting for 60 seconds?

A

any error is multiplied by 3

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9
Q

what causes vision in the fovea?

A

the prescence of cones to detect colour, each receptor connects to a different neurone

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10
Q

group b had the root tip removed and continued to grow horizontally - what conclusion can we draw from this?

A

IAA is produced in the root tip

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11
Q

group c had the upper half of the root tip removed, and grew downwards but less steeply - what conclusion can we draw from this?

A

less IAA is produced so there is less inhibition of growth in the lower side

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12
Q

explain the effect of temperature on the rate at which NAA is taken up by the lower surface of the leaf

A

increasing the temperature increases the kinetic energy, increasing the rate of diffusion

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13
Q

there are differences in the properties of the cuticle on the upper and lower surfaces of the leaves. Suggest how these differances might explain the difference in uptake rate.

A

upper layer has thicker cuticle - slowing rate of diffusion

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14
Q

explain why it takes time for the rod cells to recover their sensitivity to light after moving into darkness?

A

the rhodopsin has been bleached by the light, time is required for resynthesis of rhodopsin

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15
Q

one reason that the reaction time is slower when body temperature falls is because nerve impulse conduction is slower. Explain how a lower temperature leads to a slower nerve impulse conduction

A

slows rate of diffusion of K+ amd Na+

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16
Q

other than temperature, give 2 factors that affect the rate of nerve impulse conduction

A

myelination, diameter of axon

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17
Q

why is the genetic code described as being universal? (1)

A

in all organisms, the same triplet codes for the same amino acid

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18
Q

The genetic code uses four different bases, what is the maximum number of different DNA triplets that can be made using these four bases?

A

64

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19
Q

What is epigenetic inheritance? (2)

A

Changes to inherited gene function without altering the DNA base sequence, caused by an environmental factor.

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20
Q

BMI = mass in kg/ (height in metres)*2 calculate the BMI of a boy weighing 70kg and 170cm tall

A

24

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21
Q

what is a tumour?

A

a collection of cells growing out of control

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22
Q

what is cancer?

A

when cells from a tumour have spread/ metastasis has happened

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23
Q

what is the genome of an organism?

A

all genes present in a haploid set of chromosomes

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24
Q

Explain how methylation of a tumour suppressor gene can lead to cancer (3)

A

the methyl group attaches to a cytosine base and stops transcription protein that prevents cell division not produced no control of mitosis —-> cancer

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25
Q

Deletion changes the nature of the protein (in diagram) but substitution does not. Suggest why (3)

A

deletion causes frame shift code is degenerate so amino acid not altered

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26
Q

Give 2 factors (other than cost) that should be considered when selecting an antibiotic to treat a bacterial disease (2)

A

side affects, interaction with other drugs, allergies, conditions

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27
Q

A mutation in a tumour suppressor gene can result in the formation of a tumour. explain how (2)

A

tumour suppressor gene inactivated increasing rate of cell division

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28
Q

some cancer cells have a receptor protein in their cell surface membrane that binds to a hormone called a growth factor, This stimulates cancer cells to divide. this can be prevented using monoclonal antibodies, suggest how (3)

A

Antibody has a specific tertiary structure complementary to the receptor protein preventing the growth factor from binding

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29
Q

If the DNA of the cell is damaged, a protein called p53 stops the cell cycle. Mutation in the gene for p53 could cause cancer to develop. Explain how (3)

A

p53 is non functional or not coded for the cell cycle continues in the damaged cell (no apoptosis) resulting in uncontrolled cell division

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30
Q

Name 2 enzymes involved in semi conservative DNA replication (2)

A

DNA polymerase DNA helicase

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31
Q

When ATR phosphorylates enzymes, they become able to bind to their substrates. Use your knowledge of enzyme structure to suggest why (2)

A

the addition of the phosphate group alters the tertiary structure, making it complementary to the substrate

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32
Q
A

1 Closed, open, closed

2 Closed, closed, open

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33
Q

Describe how the resting potential is established in an axon by the movement of ions across the membrane. (2)

A

Active transport Na+ out, diffusion of K+ out

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34
Q

Why doesn’t every stimulus trigger an action potential? (3)

A

refractory period

the membrane is hyperpolarised

threshold cannot be reached - greater stimulation required

35
Q

What is the role of ATP in the contaction of myofibril

A

hydrolysis of ATP on myosin head causes myosin to bend, pulling actin molecules

allows the actin to detach

36
Q

Describe how calcium ions are involved in synaptic transmission (2)

A

Ca2+ enters presynaptic neurone

increase permeability of the presynaptic neurone causing fusion of the vesicles with the membrane

37
Q
A
38
Q

Explain how DNA structure is related to it’s function (6)

A

Long - so can store a lot of information

Helix - so compact

Base sequences store information code for amino acids/ proteins

Double stranded so semi conservative replication takes place

Hydrogen bonds between base pairs so stable/strong or weak so allow strand seperation

39
Q

More cancer cells could be destroyed if the grug was administered more frequently

Suggest why the drug was not given more frequently. (2)

A

Side effects

too many healthy cells killed - more time needed to allow recovery of healthy cell

40
Q

Oestrogen is a hormone that affects transcription. It forms a complex with a receptor in the cytoplasm of target cells. Explain how an activated oestrogen receptor affects the target cell (2)

A

Oestrogen-oestrogen receptor complex forms a transcription factor stimulates RNA polymerase

this increases transcription

41
Q

Describe how genetic fingerprinting may be carried out on a sample of DNA (6)

A

DNA is cut using a restriction enzyme

carry out gel electrophoresis to seperate strands based off length of VNTRs sequence

do southern blotting method

apply probe - flourescence or radioactivley labelled

42
Q

Explain how genetic fingerprinting allows scientists to identify father of a cub (2)

A

The bands in the cub that don’t come from mother must be in father’s DNA fingerprint

43
Q

(gel electrophoresis) Two bands are usually seen for each person tested. Suggest why only one band was seen for person L?

A

Homozygous fragments, same mass

44
Q

Why is a log scale is used to record the number of cells (1)

A

records rapid/exponential growth

45
Q

Heat stress is a condition that often occurs in plants exposed to high temperatures for a prolonged period of time. Heat stress is a major factor in limiting the rate of photosynthesis

Heat stress decreases the light dependent reaction of photosynthesis. Explain why this leads to a decrease in the light - independent reaction.

A

less ATP and NADH ( products of light dependent reaction) which slows down the light independent reaction

46
Q

A decrease in the activity of the enzyme rubisco would limit the rate of photosynthesis. Explain why. (2)

A

less CO2 reacts with RuBP, less GP

47
Q

Describe how alterations to tumour supressor genes can lead to the development of tumours (3)

A

hypermethylation

mutation

tumour supressor genes are not transcribed

OR

amino acid sequence/ primary structure altered

uncontrolled cell division

48
Q

Describe how you would calculate mean percentage cover for beach grass on a sand dune (3)

A

use random sampling technique - grid, random sampling

large sample

divide total percentage by no. quadrats

49
Q

The scientists concluded that the results shown in Figure 5 were due to succession

explain why. (4)

A

the grass is a pioneer species

it alters the conditions

less hostile more suitable for other species

50
Q

In genetic crosses the observed phenotypic ratios are often not the same as the expected ratio.

suggest two reasons why

A

Small sample size; Fusion/fertilisation of gametes is random; Linked Genes; Epistasis; Lethal genotypes;

51
Q

Furosemide and CVT are used to remove excess fluid from the body. Scientists investigated the affects of these drugs on the body, suggest and explain one reason why they were given the same amount of food (2)

A

affects water potential, and so affects the volume of urine produced

52
Q

Furosimide inhibits the absorbtion of sodium and chloride ions from the filtrate produced from the filtrate produced in the nephrons

Explain how furosimide causes an increase in the volume of urine produced (3)

A

water potential of filtrate is decreased

less water is reabsorbed by osmosis

collecting duct is where osmosis occurs

53
Q

Dopamine is a neurotransmitter released in some synapses of the brain. The transmission of dopamine is similar to that of acetylcholine. Dopamine stimulates the production the nerve impulses in postsynaptic neurones.

Describe how.

A

dopamine diffuses across the synapses

dopamine attaches to receptors

stimulates the movement of sodium ions triggering an action potential

54
Q

GABA is a neurotransmitter released in some inhibitory synapses in the brain. GABA causes negatively charged chloride ions to enter postsynaptic neurones.

Explain how this inhibits postsynaptic neurones. (3)

A

neurone becomes hyperpolarised

more stimulation required

to trigger action potential

55
Q

What is precipated DNA? (1)

A

DNA, the transcription factor, and the antibody

56
Q

Soybeans are used in a number of processed foods. However, soybeans contain a protein known as P34 that causes an allergic response in some people. Scientists have created transgenic soybeans that produce single-stranded cDNA, which prevents transcription of the P34 gene. They used recombinant plasmids as vectors to transform soybean cells. After they had screened these cells for production of the P34 protein, they cultured the transformed cells to form soybean plants.

Suggest how single-stranded cDNA could prevent transcription of the P34 gene (1)

A

Binds to P34 gene/DNA/mRNA

OR

Binds to transcription factor gene/DNA

OR

Binds to promoter;

57
Q

Describe the roles of two named types of enzymes used to insert DNA fragments into box plasmids. (2)

A

Restriction (endonuclease/enzyme) to cut plasmid/vector; 2. Ligase joins gene/DNA to plasmid/vector;

58
Q

Red/Green colour blindness affects men more than women

explain why (2)

A

The gene is on the X chromosome

women can be heterozygous carriers whereas men only require one allele to express the condition

59
Q

The use of iPS cells could have advantages over gene therapy to treat red green colour blindness, suggest why (3)

A

iPS cells one time treatment/less chance of rejection / long term
virus could cause side affects

60
Q
A

C - Myosin

D- mitochondrion

E - Myofibril

61
Q

During vigorous exercise the pH of skeletal muscle tissue falls. This fall in muscle pH leads to a reduced ability for calcium ions to stimulate muscle contraction. Suggest how (3)

A
  1. Low pH changes shape of calcium ion receptors
  2. Fewer calcium ions bind to tropomyosin
  3. Fewer tropomyosin molecules move away;
  4. Fewer binding sites on actin revealed;
  5. Fewer cross-bridges can form

OR Fewer myosin heads can bind;

62
Q

The nerve pathway may be considered a reflex arc suggest why (1)

A
63
Q

Atrazine binds to proteins in the electron transfer chain in chloroplasts of weeds, reducing the transfer of electrons down the chain. Explain how this reduces the rate of photosynthesis in weeds. (4)

A

Reduced transfer of protons across thylakoid membrane OR Reduced chemiosomotic gradient/proton gradient across thylakoid membrane; (So) less ATP produced; (So) less reduced NADP produced; (So) light-independent reaction slows/stops OR Less reduction of GP to triose phosphate;

64
Q

Explain the loop of the curve in the loop of henle in figure 4 (3)

What is the evidence in figure 4 that ADH was being secreted (2)

A

1) Concentration rises in descending limb because sodium ions enter and water lost; Concentration falls in ascending limb because sodium ions (and chloride) ions actively removed; But water remains (in ascending limb) because its walls are impermeable (to water);
2) Concentration rises in collecting duct because it loses water by osmosis; ADH increases permeability (of walls of collecting duct) to water;

65
Q

Define epigenetics (2)

A

heritable change in gene function without altering the DNA base sequence

66
Q

Explain how increased Methylation could lead to cancer (4)

A

Methyl groups (could be) added to (both copies of) a tumour suppressor gene; The transcription of tumour suppressor genes is inhibited; Leading to uncontrolled cell division;

67
Q
A
68
Q

How does Fig.2 show eveidence of succession (5)

A
  1. (Overall, data show an) increase in species richness/increase in species diversity/increase in total number of living organisms;
  2. Baetis quilleri and/or Pentaneurini guttipennis are pioneers;
  3. (Pioneers cause) named change of environment eg provide food for other species;
  4. New species/example from data colonise once there is a change;
  5. Baetis quilleri/Pentaneurini guttipennis/Helicopsyche mexicana decline/outcompeted/eaten as succession continues;
69
Q

People suffering from pituitary dwarfism do not make enough human growth hormone (HGH). They can be treated using injections of HGH. A geneticist wants to transform the bacterium, Escherichia coli, to make HGH by adding the gene coding for HGH. The geneticist could obtain the HGH gene using any one of three methods.

  1. Use restriction enzymes to cut out a fragment of DNA containing the HGH gene from a human genome.
  2. Convert mRNA for HGH into cDNA using reverse transcriptase.
  3. Create the HGH gene using a ‘gene machine’.

The geneticist decided not to use restriction enzymes to cut out a fragment of DNA containing the HGH gene from a human genome. She made this decision because only methods 2 and 3 would produce DNA that E. coli could use to make HGH.

Explain why only methods 2 and 3 would produce DNA that E. coli could use to make HGH.

A
  1. Human DNA/human gene/HGH gene contains introns OR Methods 2 and 3 produce DNA/HGH without introns;
  2. E. coli cannot remove introns/cannot splice mRNA/cannot splice pre-mRNA;
70
Q

Describe how the geneticist would attempt to insert copies of the HGH gene into the plasmid (3)

A
  • cut with a restriction enzyme
  • leaves complementary sticky ends
  • add ligase
71
Q
A

Kinesis - the insect is not moving towards a specific region

72
Q
A

taxes

73
Q

The ratio of bar eyed flies to round eyes was not what the student expected.

suggest 2 reasons why (2)

A

random fertilisation

small population

selective advantage

74
Q

There were 850 fruit flies in one population. In this population, 510 fruit flies had the genotype WN WN , 255 had the genotype WN WV and 85 had the genotype WV WV . Calculate the actual frequency of the allele WV .

Do not use the Hardy-Weinberg equation in your calculation. [1 mark]

A
  1. 25
    because. … total no alleles = 850 x 2

total Wv alleles = (2x85)+255 = 425

425/ 1700 = 0.25

75
Q

Suggest and Explain two reasons why a poor supply of phosphate ions results in poor plant growth (2)

A

Phosphate for ATP

Phosphate for nucleotides

76
Q

Explain how the resting potential of -70 is maintained in the sensory neurone (2)

A

sodium pumped out, potassium pumped in

membrane is more permeable to potassium

77
Q

explain how pressure to the pacinian corpuscle produces change in the membrane potential (3)

A

pressure causes lamellae to stretch

ion channels open and sodium moves out

the more pressure there is the more sodium moves out

78
Q

the membrane potential at q was the same no matter how much pressure was placed on it explain why (2)

A

threshold is reached

all or nothing principle

79
Q

MS destroys the myelin sheath, Explain how this results in slower response to the stimuli (2)

A

less saltutory conduction

more depolarisation along length

80
Q

suggest two types of stimuli that may cause a blink reflex (1)

A

light, pressure, touch, temperature, chemical, temperature, noise, smell

81
Q

some dieseases cause blink rate, doctors do not often use blink rate to diagnose. suggest why? (2)

A

no normal blink rate for comparison, many factors affect blink rate

82
Q

Synapses are unidirectional. Explain how acetylcholine contributes to a synapse being unidirectional (2)

A

acetylcholine released from pre synaptic

binds to receptors on the post synaptic

83
Q
A

Biology Revision Year 2 (13 decks)

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