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A2 Biology Unit 5

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AQA A2 Biology Unit 5 Contents
Specification Human Nervous system Nerve Cells The Nerve Impulse Synapses Receptors Muscle Animal Responses Control of Heart Rate The Hormone System Homeostasis Temperature Homeostasis Blood Glucose Homeostasis Control of Mammalian Oestrus Plant Responses The Genetic Code Transcription Translation Gene Mutations Stem Cells Control of Gene Expression Biotechnology PCR DNA sequencing Southern Blot Genetic Fingerprinting In vivo cloning Genetically Modified Organisms Gene Therapy Genetic Screening and Counselling 2 4 6 10 14 18 25 28 30 33 34 38 42 44 47 50 52 54 58 62 66 69 72 75 77 80 85 89 92

Molecular Genetics

These notes may be used freely by A level biology students and teachers, and they may be copied and edited. Please do not use these materials for commercial purposes. I would be interested to hear of any comments and corrections. Neil C Millar (nmillar@ntlworld.co.uk) Head of Biology, Heckmondwike Grammar School High Street, Heckmondwike, WF16 0AH Jan 2012

HGS Biology A-level notes

NCM 11/12

A2 Biology Unit 5

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Biology Unit 5 Specification
Control Systems Organisms increase their chance of survival by responding to changes in their environment. The Nerve Impulse The structure of a myelinated motor neurone. The establishment of a resting potential in terms of differential membrane permeability, electrochemical gradients and the movement of sodium and potassium ions. Changes in membrane permeability lead to depolarisation and the generation of an action potential. The all-or-nothing principle. The passage of an action potential along nonmyelinated and myelinated axons, resulting in nerve impulses. The nature and importance of the refractory period in producing discrete impulses. Factors affecting the speed of conductance: myelination and saltatory conduction; axon diameter; temperature. Synapses The detailed structure of a synapse and of a neuromuscular junction. The sequence of events involved in transmission across a cholinergic synapse and across a neuromuscular junction. Explain unidirectionality, temporal and spatial summation and inhibition. Predict and explain the effects of specific drugs on a synapse (recall of the names and mode of action of individual drugs will not be required). Receptors Receptors only respond to specific stimuli. The creation of a generator potential on stimulation. • The basic structure of a Pacinian corpuscle as an example of a receptor. Stimulation of the Pacinian corpuscle membrane produces deformation of stretchmediated sodium channels leading to the establishment of a generator potential. • Differences in sensitivity and visual acuity as explained by differences in the distribution of rods and cones and the connections they make in the optic nerve. Muscle The sliding filament theory of muscle contraction. Gross and microscopic structure of skeletal muscle. The ultrastructure of a myofibril. The roles of actin, myosin, calcium ions and ATP in myofibril contraction. The role of ATP and phosphocreatine in providing the energy supply during muscle contraction. The structure, location and general properties of slow and fast skeletal muscle fibres Animal Responses A simple reflex arc involving three neurones. The importance of simple reflexes in avoiding damage to the body. Taxes and kineses as simple responses that can maintain a mobile organism in a favourable environment. Investigate the effect of external stimuli on taxes and kineses in suitable organisms. Control of Heart Rate The role of receptors, the autonomic nervous system and effectors in controlling heart rate. Hormones Nerve cells pass electrical impulses along their length. They stimulate their target cells by secreting chemical neurotransmitters directly on to them. This results in rapid, short-lived and localised responses. Mammalian hormones are substances that stimulate their target cells via the blood system. This results in slow,...
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