Long questions Flashcards
5b) Explain the roles of specific enzymes in prokaryote DNA replication. (7) (may 2016)
«DNA» gyrase relieves strains «in the double helix»
b. helicase unwinds the double helix by breaking hydrogen bonds between the two strands of DNA
«DNA» primase adds an RNA primer
DNA polymerase III adds «DNA» nucleotides in a 5’ to 3’ direction
DNA polymerase III adds nucleotides at the primer
DNA polymerase I replaces RNA with DNA
«DNA» ligase links Okazaki fragments
DNA polymerase I/DNA polymerase III proofreads for mistakes
6c) Explain how the structure of the nephron and its associated blood vessels enable the kidney to carry out its functions. (8) (May 2016)
a. osmoregulation is a function of the kidney
b. ultrafiltration in the glomerulus (Reject ultrafiltration in the Bowman’s capsule)
c. basement membrane/filtration slits/podocytes act as filter/prevent loss of «large» «proteins»/prevent loss of blood cells
d. high «blood» pressure in glomerulus due to larger afferent than efferent arteriole
e. «selective» reabsorption of useful substances in proximal convoluted tubule
f. microvilli maximises large surface area / pump proteins to reabsorb specific solutes
g. descending limb in loop of Henle permeable to water
h. active transport of Na+ out of ascending limb «from filtrate to medulla»
i. ascending limb is impermeable to water
j. loop of Henle creates hypertonic conditions in medulla
k. distal convoluted tubule adjusts pH/adjusts concentration of Na+/K+/H+
l. water reabsorbed in collecting duct
m. collecting duct permeability to water varies due to number of aquaporins/ADH
n. osmoregulation by varying the amount of water reabsorbed «in the collecting duct»
7c) In hot, dry conditions plants lose water rapidly due to transpiration. Explain how the structures and processes of the plant allow this water to be replaced. (8) (may 2016)
Answer has to include structures (roots, leaves, adaptations) and processes (xylem, capillary action)
a. evaporation of water «in leaf/mesophyll» creates transpiration pull
b. water drawn out of xylem by capillary action/adhesion «to cellulose»
c. low pressure/pulling force in xylem
d. hydrogen bonds make water cohesive/allow water to be pulled up under tension
e. xylem resists tension with lignified walls
f. water travels from the roots to the leaves in xylem
g. water absorbed in roots by osmosis
h. active transport of ions/solutes into roots enable osmosis
i. extensive root systems/many root hairs
j. thick, waxy cuticle reduces transpiration
k. small/no leaves
l. few stomata/rolled leaves
m. hairs on leaf surface «to reduce air flow near the leaf
n. stomata open at night to reduce water loss
(6b) Explain transcription. [7] (Nov 2021)
a synthesis of mRNA
b RNA nucleotides linked together to form a strand;
c RNA strand assembled on DNA template / copy made of sense strand;
d RNA polymerase carries out transcription/links RNA nucleotides;
e RNA polymerase uncoiling/separation of DNA strands;
f 3’ end of nucleotides linked to 5’ end of (growing RNA) strand;
g complementary base pairing
h uracil instead of thymine in RNA;
i RNA polymerase binds to a promoter;
j regulated by transcription factors (enhancers, silencers) /DNA binding proteins/nucleosomes;
(6c) Distinguish between continuous and discrete variation, using examples. [4] (Nov 2021) (topic 10.2)
a no distinct categories / many possible phenotypes (continuous) distinct categories / few possible phenotypes (discrete) b multiple genes/polygenic (continuous) one/few influencing genes (discrete) c environmental influences (continuous) not influenced by environment (discrete) d height/weight/skin colour (continuous) blood groups/number of eggs (discrete)
(7a) Outline how the properties of water make it an ideal transport medium in plants. [4] (Nov 2021)
a polarity of water;
b hydrogen bonds between water molecules;
c cohesion between water molecules/water molecules stick together;
d cohesion allows tensions/low pressures/transpiration pull/movement upward/against gravity;
e adhesion to cellulose generates tensions (in xylem)
f solvent for many substances
g liquid at most temperatures experienced by plants / liquid so can flow;
(7b) Distinguish between the xylem and phloem of plants. [4] (Nov 2021)
a transports water/mineral ions organic compounds b from roots to leaves from source to sink c dead cells (xylem) living cells (Phloem) d continuous tubes (xylem) sieve plates (Phloem) e flow due to low pressures/tension (xylem) due to high pressure/pressure gradient (phloem) f thicker walls (xylem) thinner walls g lignified walls gives support (xylem) does not provide support/strength h wider lumen (xylem) narrower lumen (phloem)
(7c) Explain how the light-independent reactions of photosynthesis rely on the light-dependent reactions. [7] (Nov 2021)
(Mention products in light-dependent, how they are made briefly, where and how they are used in light independent, light-independent products run out in darkness so Calvin cycle is indirectly dependent on light)
a light-dependent reactions produce ATP and reduced NADP;
b ATP generated by chemiosmosis/by photophosphorylation/by ATP synthase;
c reduced NADP produced using electrons from Photosystem I;
d RuBP + CO2 to glycerate 3-phosphate (in light independent reactions);
e glycerate 3-phosphate reduced to triose phosphate
f ATP and reduced NADP used in the light-independent reactions;
g reduced NADP provides electrons/hydrogen / to reduce glycerate 3- phosphate to triose phosphate;
h ATP provides energy (for reduction of glycerate 3-phosphate);
i ATP needed to regenerate RuBP
j ATP/reduced NADP run out in darkness
k Calvin cycle only possible with light/is indirectly dependent on light;
(8b) Explain the production of antibodies in humans. [7] (Nov 2021)
a antigens stimulate antibody production;
b antibodies produced by lymphocytes;
c phagocytes engulf pathogens and display antigens from them;
d T-cells activated by binding antigen/by macrophage displaying antigen;
e activated T-cells cause activation of B-cells;
f mitosis/division of (activated) B-cells (to produce a clone of cells)
g plasma cells formed from divided B-cells;
h plasma cells secrete antibodies;
i clonal selection / plasma cells make same type of antibody/antibody specific to same antigen;
j some activated B-cells become memory cells;
(6a) Explain how circulation of the blood to the lungs and to other systems is separated in humans and what the advantages of this separation are. [8] (Nov 2016)
(Mention double circulation, difference of left right ventricle and atrium, aorta and pulmonary artery, reasons for low pressure to lungs and high pressure to systems, separation of oxygenated and deoxygenated blood)
a. double circulation / pulmonary and systemic circulations (Points may be earned using an annotated diagram)
b. heart is a double pump / heart has separate pumps for lungs and other systems
c. deoxygenated blood pumped to the lungs and oxygenated to other organs
d. each side of the heart has an atrium and a ventricle
e. left ventricle pumps blood to the systems and right ventricle pumps blood to the lungs
f. left atrium receives blood from the lungs and right atrium receives blood from systems
g. left ventricle pumps blood via the aorta and right ventricle pumps blood via the pulmonary artery
h. left atrium receives blood via the pulmonary vein and right atrium receives blood via the vena cava
i. lungs require lower pressure blood / high pressure blood would damage lungs
j. high pressure required to pump blood to all systems apart from lungs
k. pressure of blood returning from lungs not high enough to continue to tissues
l. oxygenated and deoxygenated blood kept separate to ensure all tissues receive blood with high oxygen saturation
(6b) Describe what happens in alveoli. [4] (Nov 2016)
(function, action of gas exchange, transport method, how is oxygen transported, pressure/volume of alveoli, pneumocytes)
a. gas exchange
b. oxygen diffuses from air to blood and carbon dioxide diffuses from blood to air
c. oxygen binds to hemoglobin in red blood cells
d. pressure inside decreases as air enters during inspiration
e. blood flow through capillaries / concentration gradients of gases maintained
f. type II pneumocytes secrete surfactant to prevent sides of alveolus adhering
(6c) Distinguish between the composition of the blood of the renal artery and the blood of
the renal vein. [3] (Nov 2016)
a. less urea in renal vein
b. less oxygen in the renal vein
c. more carbon dioxide in renal vein
d. less glucose in renal vein
e. concentration of sodium ions/chloride ions/pH at normal level in the renal vein whereas it is
variable in renal artery
f. solute concentration/osmolarity at normal level in the renal vein whereas it is variable in renal artery
(c) Growth in living organisms includes replication of DNA. Explain DNA replication. [8] (Nov 2016)
a. helicase unwinds the double helix
b. gyrase relieves strains during uncoiling
c. helicase separates the two strands of DNA/breaks hydrogen bonds
d. each single strand acts as a template for a new strand / process is semi-conservative
e. DNA polymerase III can only add nucleotides to the end of an existing chain/to a primer
f. (DNA) primase adds RNA primer
g. DNA polymerase (III) adds nucleotides in a 5’ to 3’ direction
h. complementary base pairing / adenine to thymine and cytosine to guanine
i. DNA polymerase (III) moves towards the replication fork on one strand and away from it on the
other strand
j. continuous on the leading strand and discontinuous on the lagging strand
k. DNA polymerase I replaces RNA with DNA
l. ligase joins the fragments together
(8a) Explain the processes by which light energy is converted into chemical energy. [8] (Nov 2016)
(Mention the process is photosynthesis, light dependent in detail as it is asking the conversion of light energy to chemical energy, the products made in light dependent used in Calvin, briefly mention products made in calvin)
a. plants convert light to chemical energy by photosynthesis
b. chlorophyll/photosynthetic pigments absorb light
c. electrons are excited to higher energy level
d. excited electrons pass along chain of electron carriers
e. energy from electrons used to pump protons across thylakoid membrane/into thylakoid space
f. chemiosmosis used to make ATP
g. ATP synthase generates ATP
h. pigments arranged in photosystems
i. electrons from Photosystem II flow via the electron chain to Photosystem I
j. electrons from Photosystem I are used to reduce NADP
k. ATP and reduced NADP used in the Calvin cycle
l. Glucose produced containing energy
- (a) Autosomal genes are located in chromosomes that are not sex chromosomes. The inheritance of autosomal genes is affected by whether the genes are linked or unlinked. Explain the two types of inheritance, using the example of parents that are heterozygous for two genes A and B. [7] (May 2021 TZ2)
a. unlinked genes are on different chromosomes / vice versa ✔
b. unlinked alleles are inherited independently / vice
versa ✔
c. (In unlinked inheritance) there is an equal chance for all 4 options to occur / AB, Ab, aB, ab / vice versa ✔
d. (dihybrid crosses involving) linked genes do not produce Mendelian ratios ✔
e. (excluding recombinants) there is a 1:1 chance of inheriting the different options/AB or ab ✔
f. in linked characteristics alleles might not migrate together if there is crossing over/ recombinants are formed ✔
g. crossing over occurs in prophase I of meiosis ✔
h. when the sister chromatids migrate in meiosis II the characteristics forming gametes are different/Ab, aB ✔
i. formation of recombinants causes changes in ratio
j. correct named example of inheritance of linked/unlinked characteristics ✔
k. Punnett/paired diagrams of both unlinked and linked characteristics ✔
l. genes which are linked but are far apart on the chromosome can display independent assortment ✔
