12 Respiration
12.1 Respiration
Core
• State the uses of energy in the body of humans: muscle contraction, protein synthesis, cell division, active transport, growth, the passage of nerve impulses and the maintenance of a constant body temperature
• State that respiration involves the action of enzymes in cells

12.2 Aerobic respiration
Core
• Define aerobic respiration as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy
• State the word equation for aerobic respiration as
glucose + oxygen → carbon dioxide + water
• Investigate the uptake of oxygen by respiring organisms, such as arthropods and germinating seeds
Supplement
• State the balanced chemical equation for aerobic respiration as

C6H12O6 + 6O2 → 6CO2 + 6H2O

• Investigate the effect of temperature on the rate of respiration of germinating seeds

12.3 Anaerobic respiration
Core
• Define anaerobic respiration as the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen
• State the word equations for anaerobic respiration in muscles during vigorous exercise (glucose → lactic acid) and the microorganism yeast (glucose → alcohol + carbon dioxide)
• State that anaerobic respiration releases much less energy per glucose molecule than aerobic respiration
Supplement
• State the balanced chemical equation for anaerobic respiration in the microorganism yeast as

C6H12O6 → 2C2H5OH + 2CO2

• State that lactic acid builds up in muscles and blood during vigorous exercise causing an oxygen debt
• Outline how the oxygen debt is removed during recovery, limited to:
– aerobic respiration of lactic acid in the liver
– continuation, after exercise, of fast heart rate to transport lactic acid in blood from muscles to the liver
– continuation, after exercise, of deeper breathing supplying oxygen for aerobic respiration of lactic acid

13 Excretion in humans
13.1 Excretion in humans
Core
• State that urea is formed in the liver from excess amino acids
• State that carbon dioxide is excreted through the lungs
• State that the kidneys excrete urea and excess water and salts
• Explain that the volume and concentration of urine produced is affected by water intake, temperature and exercise
• Identify on drawings, diagrams and images, the ureters, bladder and urethra
Supplement
• Describe the role of the liver in the assimilation of amino acids by converting them to proteins, including plasma proteins, e.g. fibrinogen
• Define deamination as the removal of the nitrogen-containing part of amino acids to form urea
• Explain the need for excretion, limited to toxicity of urea and carbon dioxide
• Outline the structure of the kidney, limited to the cortex, medulla and ureter
• Outline the structure and functioning of a kidney tubule, including:
– the role of the glomerulus in the filtration from the blood of water, glucose, urea and salts
– the role of the tubule in the reabsorption of all of the glucose, most of the water and some salts back into the blood, leading to the concentration of urea in the urine as well as loss of excess water and
salts (details of these processes are not required)
• Explain dialysis in terms of salt balance, the maintenance of glucose concentration and the removal of urea
• Describe the use of dialysis in kidney machines
• Discuss the advantages and disadvantages of kidney transplants, compared with dialysis

14 Coordination and response
14.1 Nervous control in humans
Core
• Describe a nerve impulse as an electrical signal that passes along nerve cells called neurones
• Describe the human nervous system in terms of:
– the central nervous system consisting of brain and spinal cord
– the peripheral nervous system
– coordination and regulation of body functions
• Identify motor (effector), relay (connector) and sensory neurones from diagrams
• Describe a simple reflex arc in terms of receptor, sensory neurone, relay neurone, motor neurones and effector
• Describe a reflex action as a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)
• Define a synapse as a junction between two neurones
Supplement
• Distinguish between voluntary and involuntary actions Describe the structure of a synapse, including the presence of neurotransmitter-containing vesicles, the synaptic cleft and neurotransmitter receptor molecules
• Describe how an impulse triggers the release of a neurotransmitter from vesicles into the synaptic gap and how the neurotransmitter diffuses across to bind with receptor molecules, in the membrane of the neurone after the synaptic gap, causing the impulse to continue
• State that in a reflex arc the synapses ensure that impulses travel in one direction only
• State that many drugs, e.g. heroin, act upon synapses

Source:
http://www.cie.org.uk/images/329744-2019-syllabus.pdf     p. 28 (14.2)
http://www.cie.org.uk/programmes-and-qualifications