Higher Human Biology 2010 Answers (Section A) 1) C – R must be the inhibitor because it changes the shape of the active site on the enzymes, and P must be the substrate because it is catabolised. 2) D If the concentrations of Q & S are high, they prevent reactions P & R from occurring because they act as inhibitors, so the concentration of O builds up and reached a high concentration which then prevents reaction M from occurring. The only reaction that can occur then without being restricted by inhibition is the reaction from L to N. 3) D – Each base is attached one nucleotide, and each nucleotide has one sugar. So of there are 120 guanine bases, there must be 120 cytosine bases. This means there are 240 sugars so far. If there are 60 adenine bases, there must also be 60 thymine bases. This adds another 120 (60 + 60) bases. So the total is 120 + 120 which means there must be 360 sugar molecules in the fragment 4) B DNA sequence CGT – TAC GTG mRNA sequence GCA – AUG CAC tRNA sequence CGU – UAC – GUG Amino acid ala – met – his 5) D – Nucleolus: Darkstaining body within the nucleus where ribosomal RNA is synthesized. 6) A – There are proteins in cell membranes which actively transport materials across the membrane using ATP as a source of energy, this is called active transport. 7) C – From the graph, it is clear that at 2% Oxygen concentration, 80 units of sodium ion are taken up every minute. So in a five minute period, 400 units will be taken up (80 x 5) 8) D – Viruses are made of a protein coat containing a DNA or RNA core. When they combine with host cells, they inject their DNA or RNA into the cell. The host cell then comes under the command of the new genetic instructions and makes new viruses using nucleotides, amino acids and enzymes supplied by the host cell. 9) C – During the first meiotic division, the chromosomes find their homologous partners and the chromatids become intertwined at chiasmata. At these points the chromatids often break and rejoin with their opposite number and genes cross over from one chromatid to another. 10) D Both males and females are affected so the gene for deafness cannot be sexlinked.; Furthermore, the parents are unaffected, but three of their children are so the gene must be recessive. 11) A – Karyotypes show the number, shape and size of the chromosomes, not the actual genetic material, and PKU is a result of an inborn error of metabolism so it is attributed to an error in the genes. It is an inherited disorder and can be traced to a tiny mutation in a single gene on chromosome 12. Karyotypes only show the arrangement. It would be possible to detect Down’s syndrome, the sex of the fetus and evidence of nondisjunction since these all involve full chromosomes.
12) A – Alleles A and B are both codominant but completely dominant to O. So the father must have genotype OO, and the mother must have phenotype AB. The child can only have genotypes AO or BO, and since alleles A & B are both dominant to O which is recessive, his phenotype must be A or B
12)C – 1 & 2 are unaffected but they have 3 affected children. Since the allele for CS is recessive, 3 & 5 must have genotypes cc. This means 1 & 2 must also have these alleles. However, 1 & 2 have two unaffected children (4 & 5) who must have genotypes Cc or CC. Because 1 & 2 have both affected & unaffected children, they must be heterozygous as each must carry the recessive allele ( c ) as they have two affected children, both of whom must have two recessive alleles, and they have two unaffected children, both of whom must have Cc or CC. 13) A – LH (ICSH) stimulates the interstitial cells to produce testosterone. 14) B – After ovulation, LH stimulates the development of the graafian follicle into the corpus luteum. 15) D – Using percentage multiplied by number of sperm, A has 20M active sperm/cm³, B has 18M active sperm/cm³, C has 15 active sperm/cm³, D has 24M active sperm/cm³. 16) B 17) C – Carbon dioxide only diffuses out of cells as it is a waste product of respiration. 18) A is produced by heart contractions 19) B – Each box represents 0.1 sec, and one heart beat lasts 0.5 sec. So there will be two heart beats each second, and 120 heart beats each minute (2 beats x 60) 20) A – The atria contract in order to pump blood into the ventricles, then the ventricles contract in order to pump blood around the body and to the lungs to be oxygenated. 21) B – When the partial pressure of oxygen in the tissue is low, the haemoglobin is unable to keep all its oxygen and unloads some of it, so the higher the pressure the higher the affinity of haemoglobin for oxygen. If the temperature rises, the haemoglobin’s affinity for oxygen decreases, and more oxygen is unloaded. So the answer must be B. 22) C – Relaxation of the hair erector muscles means that hair traps will not be raised and air cannot be trapped to act as an insulator so more heat will be lost. Furthermore, vasodilation is the widening of the arterioles allowing more blood to flow near the surface of the skin, helping heat to escape more easily. Both of these factors result in a decrease in body temperature and help to maintain it. 2
23) B – The individual enters the warm area after 10 minutes. At 10 minutes, his/her sweat production is at a steady 1.5cm³/min. For this to increase by 100%, it must increase by 1.5cm³/min, this means that the sweat production must be 3cm³/min when it increases by 100%. The sweat production increases to this figure at 23 minutes which is 13 minutes after entering the warm area. (The horizontal scale is 1 minute per box; the vertical scale is 0.1cm³/min per box) 24) C 25) A – The word “ball” is seen by the right eye and this information travels to the left cerebral hemisphere. The man can only say “ball” because there is no language control in the right cerebral hemisphere so he is unable to say “snow”. 26) D – Diverging pathways allow one signal from the brain to be sent to many destinations simultaneously. For example, when catching a ball, all the muscles of the arm which have to be contracted or relaxed at the correct moment can do so in synchronisation. 27) D – Impulsive means “Acting or speaking too quickly (upon impulse) without first thinking of the consequences.” `Deindividuation` is a state of lowered selfawareness, a temporary loss of personal identity resulting from becoming part of a group. The individual will do things without thinking which he/she would not do on their own. 28) B The conversion of ammonium to nitrate is performed primarily by soil living bacteria and other nitrifying bacteria. 29) C – The left hand side graph shows that 400 males for every 100, 000 aged 5564 die from heart disease, annually. The population size chart shows that there are 1.5M males aged 5559, and 1.5M males aged 60 – 64, so the total number of males in that age group is 3M(1.5M + 1.5M). The ratio of deaths from heart disease for males:number of males is 4:1000 (from the bar chart on the left hand side). So this means 4 males must die for every 1000 males in the 3M population of males aged 55 – 64. Calculation: 1000 males4 die of heart disease 3 000 000 males (3 000 000/ 1000 x 4) die of heart disease annually for a Population of 3M men ages 55 – 64.