AQA A Level Biology Topic 3 Exam Questions.docx

The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. Explain why - correct answer Loss of water High blood pressure leads to an accumulation of tissue fluid. Explain how [3] - correct answer High blood pressure = high hydrostatic pressure; Increase outward pressure from (arterial) end of capillary; (So) more tissue fluid The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriole end of the capillary. Explain why [3] - correct answer Water has left the capillary; Proteins too large to leave capillary; Increasing higher concentration of blood proteins; Describe and explain the mechanism that causes forced expiration [4] - correct answer Contraction of internal intercostal muscles; Relaxation of diaphragm muscles; Causes decrease in volume of thoracic cavity; Air pushed down pressure gradient; One theory of translocation states that organic substances are pushed from a high pressure in the leaves to a lower pressure in the roots. Describe how a high pressure is produced in the leaves. [3] - correct answer Water potential becomes lower; Water enters phloem by osmosis; Increased volume (of water) causes increased pressure; During their experiment, the scientists ensured the rate of photosynthesis of their plants remained constant. Explain why this was important [2] - correct answer Rate of photosynthesis related to rate of sucrose production; Rate of translocation higher when sucrose concentration is higher; Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. Details of breathing are not required. [5] - correct answer Trachea and bronchi and bronchioles; Down pressure gradient; Down diffusion gradient; Across alveolar epithelium; Across capillary endothelium; The oxygen dissociation curve for haemoglobin shifts to the right during vigorous exercise. Explain the advantage of this shift. [3] - correct answer Lower affinity for oxygen; (To) muscles; (For) rapid respiration; Explain how the body shape of a Weddel seal is an adaptation to living in a cold environment [2] - correct answer Small SA:Vol; reduces heat loss; Describe the role of enzymes in the digestion of proteins in a mammal. [5] - correct answer (Reference to) hydrolysis of peptide bonds; Endopeptidase act in the middle of protein/polypeptide OR Endopeptidase produces short(er) polypeptides/ increase number of ends; Exopeptidases act at end of protein/polypeptide OR Exopeptidase produces dipeptides/amino acids; Dipeptidase acts on dipeptide/amino acids OR Dipeptidase produces (single) amino acids; Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. [5] - correct answer Micelles contain bile salts and fatty acids/monoglycerides; Make fatty acids/monoglycerides (more) soluble (in water) OR Maintain high(er) concentration of fatty acids/monoglycerides to cell/lining (of the ileum); Fatty acids/monoglycerides absorbed by diffusion; Triglycerides (re)formed (in cells); Vesicles move to cell membrane; Cells lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions. Explain how. [3] - correct answer Sodium ions actively transported from ileum cell to blood; Maintains/forms diffusion gradient for sodium to enter cells from gut (and with it, glucose); Glucose enters by facilitated diffusion with sodium ions; Explain the advantages of lipid droplet and Michelle formation [3] - correct answer Droplets increase surface areas (for lipase/ enzyme action); (So) faster hydrolysis/ digestion (of triglycerides/ lipids); Micelles carry fatty acids and glycerol/ monoglycerides carry fatty acids and glycerol/monoglycerides to/through membrane/ to (intenstinal epithelial) cell; Describe the role of micelles in the absorption of fats into the cells lining the ileum. [3] - correct answer Micelles include bile salts and fatty acids; Make the fatty acids (more) soluble in water; Bring/release/carry fatty acids to cell/lining (of the ileum); Maintain high(er) concentration of fatty acids to cell/lining (of the ileum); Fatty acids (absorbed) by diffusion; Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake. [2] - correct answer 1. Large(r) organisms have a small(er) surface area:volume (ratio); OR Small(er) organisms have a large(r) surface area:volume (ratio); 2. Overcomes long diffusion pathway OR Faster diffusion; Accept short diffusion pathway Mammals such as a mouse and a horse are able to maintain a constant body temperature. Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse. [3] - correct answer Accept converse answers in relation to the horse. Mouse 1. (Smaller so) larger surface area to volume ratio; Accept larger SA:V. Must be comparative. 2. More/faster heat loss (per gram/in relation to body size); Ignore heat lost more easily/readily. Must be comparative. 3. (Faster rate of) respiration/metabolism releases heat;