A greater concentration of IAA builds up on the shaded side of the shoot 5. Rhodopsin is easily broken down in low light intensity Since more that one rod cell is connected Past aqa biology essay questions the same neuron, only one impulse will be generated.
How bacteria affect human lives. ATP is released by mitochondria, providing energy to recombine acetyl and choline.
Cells in the tip of the shoot produce IAA, which is then transported down the shoot. The hormonal system — Chemicals are transported in the blood plasma which then reach target certain cells, thus stimulating them to carry out a function.
The influx of calcium ions causes presynaptic vesciles containing acetylcholine to fuse with the presynaptic membrane, releasing the neurotransmitter into the synaptic cleft 3.
Temperature — Higher temperature, faster nerve impulse. The hormone-receptor complex activates an enzyme inside the cell that produces a secondary messenger chemical 3.
Hairs flatten, reduces the insulating layer of air, so more heat can be lost to the environment Behavioural mechanisms — seeking shade, burrows, etc Control of body temperature Mechanisms to control body temperature are coordinated by the hypothalamus in the brain The hypothalamus has a thermoregulatory centre divided into two parts: This allows energy to be conserved.
Principles of coordination In mammals, there are two main forms of coordination: A common example of this type of coordination is the inflammation of certain tissues when they are damaged or exposed to foreign agents.
A threshold must be reached in the bipolar cells to which they are attached to and so since they can all contribute to reaching this threshold, they will function at lower light intensities Rod cells breakdown the pigment rhodopsin to generate an action potential.
A Few Points Raised By The Exam Boards Feedback The essay is designed to assess whether you can bring together material from a range of topics to illustrate and explain an important concept or idea.
How the structure of cells is related to their function. The number of impulses in a given time larger stimulus, more impulses per second Having neurons with different threshold values — depending on which neurons are sending impulses, and how frequently impulses are sent, the brain can interpret the strength of the stimulus Section However in this case it slows down growth rather than speeds it up.
The response is quick, yet short lived and only acts on a localised region of the body. It is a self-propagating wave of electrical disturbance that travels along the surface of an axon membrane.
Describe how these and other inorganic ions are used in living organism. The target cells have complementary receptors on the cell surface membrane Hormones are affective in small quantities set have widespread and long-lasting affects Some hormones work via the secondary messenger model: The muscle fibre and the neuron make up one motor unit When only a small force is needed only a few motor units are stimulated When a nerve impulse reaches the neuromuscular junction, the synaptic vesicles join with the presynaptic membrane and release acetylcholine which diffuses across to the postsynaptic membrane and stimulates it to allow sodium ions to enter.AQA – Biology Unit 5 The Essay: 2 Marking the essay Scientific content Is the essay Good (12 marks) Medium (8 marks) Poor (4 marks)?
Put a tick in the box for each significant Final mark Over the past few years, biologists have found more of these plant-sucking pests in southern England. A handout for pupils covering key things to think about when attempting the AQA Essay along with a powerpoint to go through the key parts in lessons.
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