WRONG Qs Term 2 Flashcards
Describe the role of a ribosome in the production of a polypeptide (3 marks):
- mRNA binds to ribosome
- two codons
- allows tRNA with anticodons to bind
Describe two functions of the structure the phospholipid bilayer (2 marks):
- form water impermeable barrier to water-soluble substances
- permeable/ allows non-polar molecules to pass through
Describe one function of the extrinsic proteins (1 mark):
Extrinsic protein for cell recognition
Describe the behaviour and appearance of chromosomes during mitosis (5 marks):
1) during prophase, chromosomes coil/ condense
2) chromosomes appear as two sister chromatids joined at the centromere
3) chromosomes line up on the equator
4) chromosomes attached to spindle fibres
5) by their centromere (during anaphase)
6) the centromere splits
7) sister chromatids are pulled to opposite poles of the cell
8) chromatids uncoil and become larger/thinner
Describe and explain the processed that occur during meiosis that increase genetic variation (4 marks):
1) homologous chromosomes pair up
2) independent segregation
3) maternal and paternal chromosomes are re-shuffled in any combination
4) crossing over leads to exchange of parts of non-sister chromatids
5) both create new combinations of alleles
Four ways in which the structure of a capillary adapts for the exchange of substances between blood and the surrounding tissue (4 marks):
- one cell thick- short diffusion distance
- permeable capillary wall
- fenestrations- allows large molecules through
- small diameter- large SA:V ratio
Explain how tissue fluid formation is formed and how it may be returned to the circulatory system (6 marks):
1) hydrostatic pressure of blood at arterial end
2) fluid/ water/ soluble molecules pass through
3) proteins/ large molecules remain
4) lowers water potential- becomes more negative
5) water moves back into venous end of the capillary via osmosis/ diffusion
6) lymph system collects any excess tissue fluid which returns to blood
How does the elastic tissue help to smooth out the flow of blood in the blood vessel? (2 marks)
1) stretches
2) expands to accommodate an increase in blood pressure
What causes the pressure of blood to decrease? (1 mark)
Left ventricle relaxes
What causes blood pressure to stay above 10kPa? (2 marks)
Elastic tissue
Recoils
Why is there a net loss of water from a capillary at the arterial end? (2 marks)
At arterial end, hydrostatic pressure greater than pressure of water potential gradient
Why does tissue fluid accumulate in the tissues of people who do not eat enough protein (2 marks)?
- less protein in blood
- WP gradient is lower
A woman takes moderate exercise. Explain what causes her heart rate to increase whilst she exercises (6 marks):
1) rate of respiration increases
2) CO2 concentration increases/ pH falls
3) chemoreceptors in aortic
4) send impulses to medulla
5) increased frequency of impulses
6) along sympathetic pathway in sinoatrial node
Describe the route taken when electrical impulses are transmitted from the sinoatrial node to the muscles of the ventricles in a healthy heart (2 marks)
- through the cardiac muscle
- to atrioventricular node
- along bundle of His
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