Exam questions Flashcards
It is thought that the differences may be caused by epigenetic changes. Explain how these changes might affect the functioning of the genome. (3 marks)
- methylation of DNA base, therefore the expression of the gene is changed
- if histones are modified, this may affect the binding of other proteins to DNA because DNA is wrapped around histones, therefore genes may become activated or repressed
A diagram shows the structure of two molecules retinal and retinol. Retinol is the most common form of dietary vitamin A and retinal is part of the structure of rhodopsin. Suggest how a deficiency of vitamin A would adversely affect a person’s vision (3 marks)
- retinol is used to make retinol
- they both have very similar structures
- less vitamin A would cause less retinol to be produced and less retinol causes less retinol meaning less rhodopsin can be made so bleaching is less likely to occur, which means hyperpolarisation is less likely to occur, in the rod cell
Explain the role of DNA primers in sequencing (2 marks)
- primers have a specific base sequence
- bind to complementary bases of the DNA be amplified
- therefore, provide a site for DNA polymerase to bind
Body farms use the bodies of pigs to study the changes in insect species on a body after death
Describe how this study could be carried out (3 marks)
- standardised pigs studied (size/breed)
- environmental conditions/abiotic factors controlled like monitoring the temperature
- record the presence of different species of insects
- regular intervals like every day
Diet is one factor that affects the development of CVD. Explain how the diet of a person could affect the development of CVD. (4)
- high salt intake
- which increases blood pressure
- high blood pressure causes damage to endothelium of artery
- high intake of cholesterol (saturated fat)
- high LDL’s (saturated fat) linked to atheroma (plaque formation)
When are the different bonds used?
-glycosidic =2 monosaccharides to form disaccharide
-ester=lipids
-peptide = proteins
Compare and contrast the structure of a disaccharide with glycogen. (4)
Similarities
* both contain carbon, hydrogen and oxygen
* both contain glycosidic bonds
* both contain glucose
Differences
* glycogen contains 1,4 and 1,6-glycosidic bonds whereas disaccharides only contain one type of glycosidic bond
* glycogen only contains glucose whereas disaccharides can contain glucose and other monosaccharides
Describe how the atrioventricular (AV) valves work during one cardiac cycle.(2)
- the valves are open { when atria contract / atrial
systole / when blood pressure greater in atria
(than ventricles) } - the valves close { when ventricles contract /
during ventricular systole/when pressure greater
in ventricles (than atria) } - valves prevent backflow of blood into the atria
during ventricular systole
The structure of the pulmonary vein is different from the structure of the pulmonary artery.
Explain how this difference is related to the function of the pulmonary vein (2)
- { larger lumen / less muscle (in walls) / thinner
walls } - explanation { larger lumen as blood pressure
lower / less muscle because contraction not
needed to push blood back to the heart }
What do platelets release?
Thromboplastin
Which enzyme that converts a soluble plasma protein into an insoluble protein at location Q?
Thrombin
One of the poisons in the berries can bind to acetylcholine receptors on the surface membrane of cells in the SAN. This prevents acetylcholine binding to the receptors if it is in low concentration. This person was treated with a drug that stopped acetylcholinesterase from being released into the synaptic gap. Explain how this drug lowered the heart rate of this person.
- acetylcholine was not broken down (as quickly)
- therefore {maintaining/increasing} the concentration of acetylcholine in the synaptic gap
- so able to compete with the poison
- and so able to receptors (on the cell surface the membrane of cells of the SAN)
Describe how macrophages ingest the bacteria. (2)
- phagocytosis
- formation of membrane extension around bacteria binding to bacteria
- bacteria inside a vesicle
(c) In a person with TB, the dormant bacteria in tubercles may be activated after several years. The
bacteria multiply rapidly, resulting in severe lung damage.
The bacteria are released from the tubercles. These bacteria can inhibit the activity of T cells and infect
other organs.
Explain why the activity of these bacteria and the inhibition of T cells means that a person may quickly
develop severe symptoms leading to death.
- further lung damage/severe breathing problems
- Mycobacterium get into the blood/lymph
- organ failure leads to death
- reduced immune response due to loss of T cells
- the role of T helper cells (productions of cytokines)
- effect of no T killer cells (infected cells will not be destroyed)
- effect of no B cells (no antibody produced)
- secondary/opportunistic causing death
