2010 Jun Unit 5 Flashcards
Does tRNA contain h bonds
yes
There is a large increase in the permeability in Na+ ions. Explain why. During action potential
Ion channel proteins open Sodium in Makes inside axon less negative/depolarisation /reaches threshold More channels open/positive feedback
During an action potential, the membrane potential rises to +40 mV and then falls.
Potassium channels open;
Potassium out;
Sodium channels close
After exercise, some ATP is used to re-establish the resting potential in axons. Explain
how the resting potential is re-established
Active transport against the concentration
of sodium from axon
LH increases, Progesterone increases. LH decreases
LH increase
Progesterone increases
Progesterone inhibits LH
LH falls
Explain how an activated oestrogen receptor affects the
target cell.
Transcription factor binds to promoter region
Stimulates RNA Polymerase
Increase transcription
Oestrogen only affects target cells. Explain why oestrogen does not affect other cells
in the body
Other cells do not have oestrogen receptors
Oestrogen and Endoxifen are similar shape.
O and E are of similar shape
E binds to the receptor
Prevents transcription
Give two characteristic features of stem cells.
Keeps dividing
Can differentiate
One of the viral enzymes makes a DNA copy of the virus RNA. Name this enzyme
Reverse transcriptase
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.
Causes frame shift
Changes primary structure
Changes tertiary structure
Some of the children in the trial developed cancer. How might the insertion of the DNA
have caused cancer?
Affects tumour suppressor gene;
Inactivates (tumour suppressor) gene;
Rate of cell division increased
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?
There are many succinate dehydrogenase
Slow fibres) have lots of mitochondria/ (slow fibres)
respire aerobically
Use evidence from the diagram to describe the distribution of mitochondria inside the
slow muscle fibres. Explain the importance of this distribution.
Near edge
Short distance for diffusion of oxygen
Oxygen used by mitochondria
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
Measure with graticule/eyepiece scale;
Calibrate against something of known size
A student found the mean diameter for 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
At random to avoid bias
A large number to be representative/minimise the effect of anomalies
Explain how the glucagon would affect the person’s blood glucose concentration.
Glycogen to glucose/glycogenolysis
By activating enzymes
Gluconeogenesis
Explain why the labelled DNA probe could be used to find out whether the haplotypes
were the same
complementary DNA;
Binds to both (haplotypes);
The label would show up in both
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
Genetic bottleneck
Little genetic variation
Suggest an explanation for the number of haplotypes in the wolves that have spread to
France.
All descended from Italian wolves/founder effect;
The wolf numbers are given per unit area. Explain why
Allows comparison;
Different (sized) areas covered
