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Aqa Maintenance of Life - Revision Guide

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Introduction

2. AQA MAINTENANCE OF LIFE - REVISION GUIDE 1. CELLS animals and plants consist of cells. All cells have the following in common: * NUCLEUS - containing chromosomes which carry the genes controlling the cell's characteristics * CELL MEMBRANE - allows movement of substances into and out of the cell. * CYTOPLASM - where chemical reactions take place under the control of enzymes. * MITOCHONDRIA - where respiration takes place (energy is released). 2. DIFFERENCES BETWEEN ANIMAL and PLANT CELLS * CELL WALL - made up of cellulose to give the plant support * CHLOROPLASTS - containing chlorophyll required for photosynthesis * LARGE VACUOLE - containing cell sap (a solution of substances in water for support and storage). 3. PHOTOSYNTHESIS -Photosynthesis describes how green plants make their own food (glucose). They take very simple substances from the environment to do this. Light CARBON DIOXIDE + WATER --> GLUCOSE + OXYGEN Chlorophyll Leaves have chloroplasts containing chlorophyll. Chlorophyll enables the plant to absorb light energy needed for photosynthesis. This light energy is used to convert carbon dioxide and water into glucose. Oxygen is released as a waste product. WHAT CAN LIMIT THE RATE OF PHOTOSYNTHESIS? ...read more.

Middle

OSMOSIS - 'movement of water particles from a region of high concentration to a region of low concentration across a partially permeable membrane'. ACTIVE TRANSPORT - 'an energy requiring process by which cells take substances against a concentration gradient'. This enables plants to absorb mineral ions from very dilute solutions. 7. CENTRAL NERVOUS SYSTEM - The Central nervous system consists of the brain and spinal cord. A network of nerves connects the brain and spinal cord to the body. Messages travel throughout the nervous system via nerve impulses. Nerve impulses are electrical impulses. SENSE ORGANS, RECEPTORS and STIMULI SENSE ORGANS RECEPTOR STIMULUS Eye (sight + balance) Light Light Ear (hearing + balance) Sound Sound Nose (smell) Chemical Chemical Tongue (taste) Chemical Chemical Skin (touch) Pressure and Temperature Pressure Temperature REFLEX ACTIONS - an automatic response to a stimulus. REFLEX ARC - the route taken by a nerve impulse through the nervous system. A reflex arc consists of three parts: 1. Sensory neurone - carrying a nerve impulse from a receptor to the spinal cord or brain. 2. Relay neurone - carrying the impulse through the spinal cord. 3. Effector/Motor neurone - carrying the impulse from the spinal cord to the effector. ...read more.

Conclusion

RECEPTOR RESPONSE BRAIN decrease in temperature EFFECTOR sweating/ capillaries dilate Example 2. Water Control STIMULUS (increased water in the blood) RECEPTOR RESPONSE BRAIN decreased water in the blood EFFECTOR less ADH secreted ADH - ANTI -DIURETIC HORMONE - causes the kidneys to absorb more water Example 3. Glucose Control STIMULUS (increased glucose in the blood) RECEPTOR RESPONSE BRAIN decreased glucose in the blood EFFECTOR more insulin secreted INSULIN - removes glucose from the blood and stores it as glycogen in the liver. 13. DRUGS (substances which alters the way the body works) * Tobacco Smoking- contains harmul chemicals e.g, -Tar deposits in the lungs and causes cancer. -Nicotine (the addictive part) causes constriction of blood vessels and makes the hard beat faster. -Carbon monoxide prevents haemoglobin from carrying as much oxygen. Carbon monoxide combines irreversibly with the haemoglobin in red blood cells SMOKING DURING PREGNANCY INCREASES THE CHANCES OF DISABILITY AND PREMATURE LABOUR. THE FOETUS IS DEPRIVED OF OXYGEN LEADING TO A LOW BIRTH WEIGHT. * Alcohol Abuse - causes impairment of judgement, slowing down reactions and possible damage to brain and liver cells. * Solvent Abuse - causes hallucinations and damage to lungs, liver and brain.. ADDICTION - drug use may lead to addiction. This is a state in which the body can not function normally without the drug and a person may suffer withdrawal symptoms without them. 1 ...read more.

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