TYS 2021 Flashcards
The human body prevents bloods loss from injury by producing a blood clot.
Describe how a blood clot is formed. [2]
- When there is a wound, the platelets will secrete
thromokinase which converts the inactive prothrombin into the active form of the enzyme thrombin, in the prescence of calcium ions. [1] - Thrombin will convert the soluble fibrinogen protein into insoluble fibrin threads which will form a mesh to trap red blood cells to form a blood clot. [1]
Suggest why some farmers restrict the movement of the animals they are growing for food. [3]
- Movement involves contraction of muscles, requiring energy [1]
- Restricting movement will reduce energy lost as heat to the surroundings [1]
- More energy can be used for growth instead, and the animals will gain more weight faster [1]
Explain the mode of action of enzymes in human digestion. [3]
- Enzymes are proteins with specific active sites that binds to a complementary site of the substrate. [1]
- They form an enzyme-substrate complex. Bonds in the substrate will be broken in this complex. [1]
- The products are the subtrate that have been broken down into simpler molecules. The enzyme remains unchanged and able to form the complex with another molecule of substrate. [1]
PKU causes a buildup of the amino acid phenylalanine in the blood. The amino acid is obtained through the diet. People with PKU do not produce the enzyme that is needed to break down phenylalanine.
A baby with PKU is growing inside the uterus of a mother with PKU. The baby is developing normaly.
Suggest why the baby in the uterus does not show any symptoms of PKU. [2]
- The amino acid phenylalanine is small enough to diffuse across the placenta into the maternal
bloodstream [1] - The enzyme to breakdown phenylalanine is present in the mother’s blood as she is normal
Hence there is no build-up of phenylalanine as the fetus develops normally inside the uterus [1]
Define excretion. [3]
- Excretion is the removal of toxic waste products or excess substances from the human body [1]
- Such as carbon dioxide produced during respiration and excreted via the lungs,
And urea produced by the deamination of excess amino acids and excreted via the kidneys. [1]
Describe the effect of the anti-diuretic hormone on the collecting duct. [2]
ADH makes the cells of the wall of the collecting duct more permeable to water [1]
So more water is reasborbed from it into the blood [1]
Dialysis is used as the treatment for kidney failure.
Describe the similarities and differences between dialysis fluid and blood plasma. [3]
- Similarities: dialysis fluid has similar concentration of glucose, amino acids and mineral salts as blood plasma. The water potential of both fluids are similar as well.
- Differences: Dialysis fluid does not contain any urea at all. It flows in the opposite direction to the flow of blood
Dialysis is used as the treatment for kidney failure.
Describe the function of dialysis fluid in dialysis. [2]
- The dialysis fluid removes urea from blood. There is a concentration gradient where urea exists in higher concnetration in blood plasma than in the dialysis fluid. Hence urea diffuses from blood plasma into the dialysis fluid. [1]
- Useful substances such as glucose or amino acids can diffuse from the dialysis fluid into the blood plasma if these are under the normal concentration. Medication for the patient can also be supplied in this way. [1]
Describe how, in biotechnology, a human gene can be inserted into bacteria to produce insulin.
- The human insulin gene is identified in th human DNA in the chromosome.
- It is cut out using 2 restriction enzymes at the
restriction sites to obtain sticky ends. - Use the same 2 restriction enzymes to cut open a bacterial plasmid to produce sticky ends complementary to the insulin gene
- Insert the insulin gene into the plasmid by using DNA ligase to form bonds between the complementary base pairs of the sticky ends to form a recombinant plasmid
- Introduce this recombinant plasmid into a host bacterium using heat or electric shock treatment to open up pores in the cell membrance for the entry of the plasmid
- A transgenic bacterium is formed, and will express the insulin gene to produce insulin protein
- Which is extracted and purified before being used by diabetic patients
Explain the principles of homeostasis. [2]
- Homeostasis is maintenance of a constant internal environment which ensures that the composition of body fluids are kept within narrow limits. [1]
- It involves a negative feedback process that brings about opposite effects to the changes detected [1]
- with a corrective mechanism to bring about the reverse effect of the stimulus detected. A feedback is sent to the receptor when the normal is reached, causing the corrective mechanism to stop. [1]
Describe how the hypothalamus coordinates the maintenance of a constant body environment. [3]
- Hypothalamus receives information about temperature changes from the environment and the blood temperature. [1]
- When temp (external and blood) is higher or lower than the norm, hypothalamus is stimulated and sends out nerve impulses to the relevant body parts via motor neurons [1]
- where the corrective mechanism brings about a series of changes to bring temperature back to the norm. [1]
Fig. 9.1 is a graph showing the rate of photosynthesis and respiration of a plant throughout the day. The area under the graph for photosynthesis seems equal to that of the graph showing respiration.
The overall mass of this living plant is not increasing. Use the information in Fig 9.1 to explain why there is no overall increase in mass. [4]
- There is no overall increase in mass as the rate of respiration equals the rate of photosynthesis. [1]
- For an increase in mass in the plant, the amount of glucose produced by photosynthesis has to be greater than the amount of glucose used during respiration. The glucose produced that’s not used up during respiration will be converted to other forms such as starch and sucrose (stored), cellulose, amino acids and fats. [1]
- The amount of glucose produced by photosynthesis during the day/ when light E is available are mostly used up by the plant during respiration. [1]
- This can be seen from the area on the graph below rate of respiration which is almost similar to the area under rate of photosynthesis [1]
Describe two functdions of the ovaries of a healthy young woman who is not pregnant. [3]
Ovaries produce sex hormones oestrogen and
progesterone [1]
which are responsible for the development and maintenance of secondary sexual characteristics in females. [1]
Ovaries also produce ova, which are released from the ovaries when they mature. [1]
