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UNIT 5 - BIOLOGY > JUNE 2010 > Flashcards

JUNE 2010 Flashcards

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1
Q

During an action potential, the membrane potential rises to +40mV and then falls. Use information from the graph to explain the fall in membrane potential (3 marks)

A
  1. Potassium ion channels open
  2. Potassium ions flood in
  3. Sodium ion channels close
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2
Q

After exercise, some ATP is used to re-establish the resting potential in axons. Explain how the resting potential is re-established. (2 marks)

A
  1. Active transport against concentration gradient

2. Sodium pumped out and potassium in

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3
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 receptror affects the target cells (2 marks)

A
  1. Binds to a transciption factor that binds to promoter
  2. Stimulates RNA polymerase
  3. Causes transcription
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4
Q

Oestrogen only affect target cells. Explain why oestrogen does not affect other cells in the body (1 mark)

A
  1. Other cells do not have the oestrogen receptors
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5
Q

Some breast tumours are stimulated to grow by oestrogen. Tamoxifen is used to treat these breast tumours. In the liver, tamoxifen is converted into an active substance endoxifen.
Figure 2 shows a molecule of oestrogen and a molecule of endoxifen.
Use figure 2 to suggest how endoxifen reduces the growth rate of these breast tumours (2 marks)

A
  1. Similar shape to oestrogen
  2. Binds to receptor
  3. Receptor not activated
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6
Q

Give two characteristic features of stem cell (2 marks)

A
  1. They are undifferentiated

2. Constantly replacing themselves

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7
Q

The insertion of the DNA copy in one of the host cell’s genes may cause the cell to make a non-functional protein. Explain how. (2 marks)

A
  1. Alters the base sequence (causes a frame shift)
  2. Different sequence of Amino Acids in the polypeptide
  3. Alters tertiary sequence
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8
Q

Some of the children in the trial developed cancer. How might the insertion of the DNA have caused cancer? (2 marks)

A
  1. Affects the tumour suppressor gene
  2. Inactivates the tumour suppressor gene
  3. Rate of cell division increased
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9
Q

Five out of the 20 children in the trial developed cancers. Although the cancer was treated successfully, the doctors decided to stop the trial in its early stages. They then reviewed the situation and decided to continue. Do you agree with their decision to continue? Explain your answer. (2 marks)

A

Yes

  1. SCID patients unlikely to survive
  2. Cancer patients are treatable
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10
Q

Succinate dehydrogenase catalyses one of the reactions in the Krebs cycle. What is the evidence from the drawing that muscle fibre S is a slow muscle fibre? Explain your answer. (2 marks)

A
  1. Contains large amount of succinate dehydrogenase

2. Slow fibres haves lots of mitochondria as they respire aerobically

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11
Q

You could use an optical microscope and a slide of stained muscle tissue to find the diameter of one of the muscle fibres. Explain how. (2 marks)

A
  1. Measure with eyepiece graticule

2. Calibrate against something of known size

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12
Q

A student found the mean diameter of the slow muscle fibres in a section. Give two precautions that she should have taken when sampling the fibres. Give a reason for each precaution. (2 marks)

A
  1. Taken at random to avoid bias

2. Large enough sample to be representative

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13
Q

The girl who took part in the investigation was being successfully treated with insulin. The graph shows that on some occasions, the concentration of glucose in her blood was very high. Suggest why

A
  1. Just eaten
  2. Containing carbohydrates/glucose
  3. Glucose absorbed from instestine into blood
  4. Long time after insulin injection
  5. Does NOT convert glucose into glycogen
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14
Q

Use the graph to evaluate the use of the urine test as a measure of blood glucose concentration (3 marks)

A
  1. There are a range of values for a particular value
  2. Positive correlation
  3. Urine test only an arbitrary scale
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15
Q

For what purpose did they use:

i) the restriction endonuclease
ii) gel electrophoresis

A

i) to cut the DNA

ii) To seperate the pieces of DNA

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16
Q

Diabetic people who do not control their blood glucose concentration ma become unconscious and go into a coma. A doctor may inject a diabetic person who is in a coma with glucagon. Explain how glucagon would affect the person’s blood glucose concentration. (2 marks)

A
  1. Glycogen converted into glucose
  2. Glucagon activates enzymes
  3. Involved in gluconeogenesis
17
Q

Explain why the labelled DNA probe could be used to find out whether the haplotypes were the same. (2 marks)

A
  1. Complementary base sequence
  2. Binds to both
  3. Label will show up on both
18
Q

Two hundred years ago there were many wolves in Italy. By the 1970s there were fewer than 100 wolves left. Since 1980, wolves have increased in number and have spread to France.
Use this information to explain the number of haplotypes in the Italian wolves. (2 marks)

A
  1. Present population descended from small number

2. Little genetic variation

19
Q

The scientists analysed the DNA on the Y chromosome and the DNA in the mitochondria of the Swedish wolves. They concluded that the Swedish wolf population descended from one male wolf in Finland and one female wolf in Russia.
Explain why the DNA on the Y chromosome helped them to reach this conclusion. (1 mark)

A
  1. The Y chromosome is always inherited from the male parents, as it is only found in males
20
Q

Suggest why DNA in the mitochondria helped them to reach this conclusion. (1 mark)

A
  1. No mitochondria crome from the sperm as they are found in the egg
21
Q

The wold numbers are given per unit area. Explain why (2 mark)

A
  1. Allows comparison

2. As different sized areas are covered

22
Q

The ecologist calculated the total prey index for each of the places that had been studied. In order to do this, he gave each prey species a value based on how much food was available to wolves from the prey animal concerned. He called this value the prey index.
The ecologist considered that the prey index gave a better idea of the food available than the prey biomass in kg. Suggest why the prey index gives a better idea of food available. (2 marks)

A
  1. Wolves do not eat all of the animal

2. Inedible parts make up different proportions

23
Q

The ecologist calculated the total prey index by combining the prey indices and the total number of animals of each species present in 1000km^2. He plotted this information on the graph.
What does the graph suggest about the factors that determine wolf numbers in North America? Explain your answer. (2 marks)

A
  1. Number of prey limit the wolf numbers
  2. As prey increases so do wolf numbers
  3. Large range so other factors involved

UNIT 5 - BIOLOGY (5 decks)

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