) Studies on the effects of hCG in humans have revealed the following information: Many different tissues are affected by hCG. Susceptible cells have glycoprotein receptors on their cell surface. These receptors are complementary to the shape of hCG molecules.
(i) What can be concluded from this information?
(hCG is a) peptide hormone / hCG is not a lipid-based hormone (hCG) binds to cell surface receptor idea that cell signalling is involved in action of hCG (hCG) uses cAMP / second messenger , to bring about response in cell
Another hormone produced during pregnancy is oestrogen. Oestrogen is lipid soluble.
Which molecule does oestrogen interact with when it changes cell activity
DNA / deoxyribonucleic acid
A hydatidiform mole is a rare complication of pregnancy that can occur after implantation of the fertilised egg in the uterus. It results in excessive production of hCG and damage to the lining of the womb, leading to miscarriage.
Suggest how a hydatidiform mole could increase hCG above normal levels
idea that (hydatidiform mole) cells produce more hCG than normal
(due to) expression / up regulation , of genes synthesising more , hCG / protein(s) idea that other tissues could be stimulated to produce more hCG than normal
During the light-independent stage of photosynthesis, triose phosphate (TP) is synthesised in the chloroplasts of plant cells.
(i) State two possible uses of this molecule within the plant.
synthesis of: (named) carbohydrate hexose sugars amino acids lipids
Summarise the importance of coenzymes in respiration. You should include details of the molecules and processes involved
• Coenzyme A: o transfers acetyl group from link reaction to Krebs cycle •
phosphorylation of glucose to form hexose-1,6bisphosphate in glycolysis
dephosphorylation of , TP in glycolysis
o dephosphorylation of / removal of phosphate group from , intermediate in Krebs cycle
o formation from substrate level phosphorylation
o formation from oxidative phosphorylation , harnessing chemical energy from chemisomosis
• NAD: o oxidation of triose (bis)phosphate in glycolysis
o oxidation of pyruvate in link reaction
o oxidation of intermediates in Krebs cycle
o reduction of cytochrome in oxidative phosphorylation
o reduction of pyruvate in lactate fermentation
o reduction of ethanal in alcoholic fermentation
• FAD: o oxidation of intermediates in Krebs cycle
The tissue labelled B is cambium.
What type of cell makes up this tissue
Enzymes digest insects that fall into Heliamphora traps.
Is the mode of action of these enzymes extracellular or intracellular? Explain your answer
extracellular because: digestion is occurring in (liquid in) trap / leaf not inside cells (enzymes are) released by plant cells , into (liquid in) trap (enzymes may also come from) bacteria (in trap)
State and explain three adaptations of plants like T. natans, which allow them to survive in water
air spaces in leaves/ stems allows leaves / stems to float , so they can access light , for photosynthesis
stomata on upper leaf surface to allow access to air , absorption of CO2
stem has air spaces oxygen can diffuse to roots , for aerobic respiration
roots may be reduced / absent not required to obtain water OR idea of not wasting resources
waxy surface / cuticle so water does not block stomata
reduced vascular tissues high water availability OR idea of not wasting resources
Hormone produced Role of hormone in body
aldosterone Na+ / K+ / ion , reabsorption in kidneys / concentration in blood OR water reabsorption OR control of blood pressure
medulla Hormone produced Role of hormone in body
adrenaline Increases heart rate.
, describe the relationship between the rate of diffusion and the surface area to volume ratio.
as SA:VOL ratio decreases rate of diffusion decreases OR as SA:VOL ratio increases rate of diffusion increases ; use of two pairs of figures with correct units (mms-1) for rate to illustrate trend ; ref to rate of diffusion in either of the first two cubes not fitting trend ;
(iii) Explain the significance of the relationship between rate of diffusion and the surface area to volume ratio for large plants.
(large plants) have a, small / low, SA : VOL ratio ; idea of diffusion too slow (to supply requirements) ; idea of need transport system (for water / minerals / assimilates) ; idea of need (special) surface area for, gaseous exchange / uptake of minerals ;
Explain why tissue fluid does not contain erythrocytes.
gap(s) between endothelium cells (too) small ; (erythrocytes) too large / cannot change shape (much) ; to, fit / move / pass, between (endothelium) cells OR through, gaps / pores / fenestrations;
Describe the role of haemoglobin in transporting oxygen around the body.
1 (haemoglobin has) high affinity for oxygen ; 2 oxygen binds to haemoglobin in, lungs / alveoli / high pO2 ; 3 oxyhaemoglobin ; 4 oxygen released, in tissues / where needed / where pO2 is low / where respiration is occurring ;
(i) Describe how the hydrogencarbonate ions are produced in the erythrocytes.
1 carbon dioxide, enters / diffuses into, erythrocytes ; 2 (carbon dioxide) combines / reacts, with water ; 3 correct ref to carbonic anhydrase; 4 forms carbonic acid ; 5 (carbonic acid) dissociates to form hydrogencarbonate ions and, hydrogen ions / protons ;
(ii) High concentrations of carbon dioxide in the blood reduce the amount of oxygen transported by haemoglobin.
Name this effect and explain why it occurs.
1 Bohr (effect / shift) ; Explanation (any 2 of the following marks) 2 reduces affinity (of Hb) for oxygen ; 3 formation of haemoglobinic acid / hydrogen ions interact with haemoglobin; 4 prevents, fall in pH / build-up of H+, in cells OR provides buffering effect ; 5 alter, structure / shape, of haemoglobin ; 6 more oxygen released where, needed / more respiration / carbon dioxide concentration high ; 7 CO2 binds to haemoglobin forming carbaminohaemoglobin ;
Name the type of cell present in meristematic tissue and describe how xylem vessel elements are produced from this type of cell
Type of cell stem (cells)
Description - any three from, by differentiation (cell) elongation deposition of lignin / lignification (of cell walls) end walls break down
The walls of blood vessels contain a polymer called collagen.
Name the type of monomer from which collagen is made and explain how two such monomers are joined together
Name amino acid
Joined by peptide , bond / link between amine group and carboxyl group (of different amino acid) condensation / water is produced
(c) Outline how the difference in lumen size between arteries and veins is related to their function
(in arteries) small lumen maintains pressure
(in veins) low resistance / friction needed because of , low pressure / slow flow
further detail idea that same flow rate is achieved by having a larger volume / cross sectional area
idea that large cross section compared to circumference means fewer particles colliding with wall / low friction / less resistance
Describe the events taking place at the points marked W, X, Y and Z and explain how these events are related to the changes in pressure shown in the diagram. (ho20 o2 depth practice paper set2
Chambers ventricles begin to contract at Y ventricles are relaxing between W and Y atria relaxed at W, X, Y and Z atrial contraction completed before Y.
Valves A-V / bicuspid , valve closes at Y and opens at X semilunar / aortic , valve opens at Z and closes at W.
Pressure At W ventricular pressure falls below aortic pressure At X ventricular pressure falls below atrial pressure At Y ventricular pressure rises above atrial pressure At Z ventricular pressure rises above aortic pressure.
M and N are formulae for two macromolecules,
M C55H98O6 N C18H30O16
Which of the formulae, M or N, corresponds to a triglyceride?
formula M because high ratio of hydrogen to oxygen