TEST YOURSELF: Key - Word Meanings

Topic Notes
1. CELLS  
Cell Basic unit of life. Unicellular organisms like bacteria only have one cell. Multi-cellular organisms have many cells.
Organelle Microscopic structures in more advanced cells, which do a particular function in that cell. eg. the nucleus, chloroplasts, mitochondria. ( NB Bacteria cells are so simple they do not have any organelles)
Tissue Group of cells of the same type doing a particular function. eg. the blood, xylem, phloem
Organ Group of tissues doing a particular function between them .eg. the heart, kidney, leaf
Organ system Group of organs doing a particular function between them. eg. the circulatory system
Diffusion Molecules and ions diffuse from regions of higher concentration to regions of lower concentration down a gradient. Eg O2 into muscle cells.
Osmosis Osmosis is the diffusion of water through a selectively permeable membrane.
Partially permeable Something that selects or allows small molecules to pass through it but not large ones.
Concentration gradient Where two areas have different concentrations of the same molecule. The more different, the steeper the gradient and the faster diffusion / osmosis will occur.
Active Transport Movement of molecules against the diffusion gradient, using energy from respiration.
Replication Exact copying of DNA.
Mitosis Produces 2 genetically identical copies of a cell. Important in growth and repair.
Meiosis Cell division, which reduces (halves) the number of chromosomes. Meiosis separates the maternal and paternal chromosomes in a cell to produce four genetically different cells with half the usual number of chromosomes.
Light energy Photosynthesis needs light energy. It changes light energy into chemical energy.
Glucose This is the sugar made in photosynthesis. It is also found in fruits and in your blood. Both plant and animal cells use glucose as a source of energy during respiration.
Sucrose This is a ‘double-sugar’ you use to sweeten your tea and to make jam. Sugar cane and sugar beet store sucrose instead of starch. It is made of glucose and fructose joined together.
Reducing Sugar A sugar that turns yellow / orange when heated with Benedict’s solution. Eg glucose.
Starch Most plants store starch. They can turn starch back into glucose when they need it for respiration. The ‘starch test’ is to add iodine solution…it should turn blue-black.
Chlorophyll This is the green pigment found in plant cells that carries out photosynthesis..
Chloroplasts These are tiny bodies found in palisade cells of leave. They are green because they contain chlorophyll.
Carbon dioxide We excrete this gas , but plants absorb it in - they must have it for photosynthesis.
Palisade mesophyll cell This is the kind of leaf mesophyll cell you need to know about. You should be able to label a diagram of a palisade mesophyll cell. It is the site of photosynthesis in a leaf.
Variegated Some leaves have white bits as well as green bits; they are called variegated leaves. Photosynthesis does not happen in the white bits.
Limiting Factor CO2, temperature and light are the 3 main ones. If any are in short supply, photosynthesis will be limited (less efficient).
Transpiration This is the loss of water vapour from leaves by evaporation. It is much faster when stomata are open than when they are closed.
Transpiration stream Water travels up xylem vessels from the roots to the leaves in the transpiration stream.
Root hair cells These are tiny hairs covering the ends of the smallest roots. They have a very large surface area. They absorb water and mineral salts (N,P,K, Mg) from the soil.
Xylem vessels These are microscopic hollow cells / tubes found in a plant's stem and ‘veins’. They carry water and mineral salts up a plant from its roots to its leaves.
Phloem tissue Small, living cells in the stem and veins that transport sucrose up and down the plant.
Guard cells Two guard cells surround each stoma. They can open and close the stoma.
Stomata Stomata are tiny holes in the epidermis (skin) of a leaf. They are usually found on the undersides of leaves. Each stoma is surrounded by two guard cells.
Auxin This is a plant hormone that causes cells to divide and grow.
Hormone This is a chemical messenger (in animals, hormones travel in the blood – and are made by ductless glands)..
Tropism This is a growth movement of part of a plant towards or away from a stimulus such as light, gravity or moisture
Phototropism A response to (+) or away (-) from light.
Geotropism A response to or away from gravity.
Epiglottis This is a little flap on the back of the throat; it closes the top of the trachea when we swallow so that food does not go down ‘the wrong way’.
Trachea This is the proper name for the windpipe. It has ‘C-shaped’ rings of cartilage support.
Bronchus The trachea divides into two tubes called bronchi.
Bronchioles Each bronchus divides into many smaller tubes called bronchioles. These can expand.
Goblet cells These are cells in the lining of the trachea and bronchi, which make mucus.
Gaseous exchange This means oxygen getting into the blood and carbon dioxide going out by diffusion.
Intercostal muscles Intercostal means 'between the ribs'. One set of intercostal muscles makes the ribcage bigger (inspiration) and another set makes it smaller (expiration).
Mucus This is a white slimy protein, which traps germs and bits of dirt which get breathed in. This stops the delicate tissues of the lung from being damaged.
Cilia These are tiny hairs which beat continuously to move the mucus up the bronchi and trachea.
Alveoli These are the tiny air sacs in the lungs – they have a huge surface area, but are only one cell thick. All gas exchange takes place here..
Large surface area Added together, the alveoli have an enormous surface area (70 square metres) through which gaseous exchange can happen.
Bronchitis Caused by the effects of tar in cigarette smoke. Paralyses cilia and causes over-production of mucus in the trachea and bronchioles.
Emphysema Break down of the alveoli – less surface area to absorb gases like oxygen.
Lung Cancer Caused by cancer-causing chemicals (carcinogens) in tar. Tumours form.
Carbon Monoxide Toxic gas in cigarette smoke. Binds irreversibly with blood haemoglobin, meaning less oxygen can be carried.
Nicotine Addictive component of cigarette smoke. Cause platelets to clump together in blood, leading to strokes and heart attacks.
Red Blood Cells These blood cells contain haemoglobin and carry oxygen.
Haemoglobin This is the protein in red blood cells, which turns into oxyhaemoglobin in the lungs.
White Blood Cells Phagocytes engulf bacteria and form ‘pus’; B-lymphocytes produce antibodies that attach to foreign antigens; T-lymphocytes reject foreign cells like transplanted tissues.
Platelets These are fragments of cells, which help to clot our blood when we cut ourselves.
Plasma This is the liquid part of blood. It contains nutrients, hormones, antibodies, fibrinogen, and waste products like urea and dissolved CO2.
Transport This is the main job of the blood. Substances are carried around the body in our blood.
Artery This is a thick walled muscular, elastic blood vessel. It carries blood away from the heart at high pressure to other parts of the body.
Vein This is a thin walled, valved blood vessel, which carries blood back to the heart.
Capillary This is a very narrow one-cell walled blood vessel, which carries blood through our tissues. Exchanges between cell and blood occur at the capillaries.
Enzymes These are the biological catalysts, which are needed to break down your food, and carry out all chemical reactions in cells. Eg. Catalase, protease, amylase, lipase
Saliva Saliva contains an enzyme called salivary amylase which digests starch to maltose sugar, and mucus which makes the food in your mouth slippery and easy to swallow.
Amylase Enzyme that digests starch into maltose.
Protease Enzyme that digests proteins to amino acids.
Lipase Enzyme that digests fats to fatty acids and glycerol.
Denaturing The enzyme structure is destroyed by heating above 50°C
Optimum The ‘best’ conditions for an enzyme eg. Pepsin works best in acid conditions of stomach.
Peristalsis The rhythmic contractions of circular and longitudinal muscles that moves food along the gut.
Stomach The part of the gut where proteins are first digested (by protease). HCl kills microbes.
Duodenum This is the first part of the small intestine. Bile secreted by the liver makes the contents of the duodenum alkaline and helps to emulsify (increase surface area) the fats and oils in our food.
Ileum This is the longest part of the small intestine. Here food is completely digested. The products of digestion are absorbed by villi, which have a large surface area to speed up absorption.
Villi Tiny finger-like projections that increase surface area for absorption of small molecules.
Liver Heaviest organ of the body, responsible for processing all the food absorbed by digestion.
Colon This is the large intestine; it is where all the water in our food and drink is absorbed into the blood.
Absorption This is the diffusion of useful substances into our blood and lymphatic systems.
Assimilation This is when the absorbed food becomes a part of your body. It is either used to provide energy, or it is used to help growth and repair of tissues. The liver is the main organ.
Mitochondria Small structures (‘organelles’) inside active cells. They carry out aerobic respiration.
Aerobic Requires oxygen to respire. This sort of respiration releases the most ATP energy.
Anaerobic Respires in the absence of oxygen. Plants / yeast produce ethanol, animals produce lactate (lactic acid).
Metabolism All the chemical processes in our cells. Your ‘basal metabolic rate’ or BMR is a measure of how active you are..
Lactic acid (lactate) A toxic chemical produced in anaerobic respiration of animals, it causes cramp.
Energy Released (not ‘produced’) in respiration & required for other activities.
ATP A high energy chemical made during respiration and used in cells as an energy store.
CNS The Central Nervous System consists of the brain and spinal cord.
Neurone This is a nerve cell. It carries an electrical impulse when it is stimulated.
Sensory Sensory neurones carry impulses from sense organs into the CNS.
Motor Motor neurones carry impulses out of the CNS to effector organs.
Intermediate neurones These nerve cells carry messages around the CNS.
Sense organ For example, the eye, ear, taste buds, skin, nose.
Receptor Structure in the skin that detects a stimulus. Eg ‘touch receptor’, ‘rod or cone cells in retina’
Effector A muscle or gland which has an effect when it is stimulated by a motor neurone impulse.
Reflex arc A nerve pathway which produces an automatic response. The brain is not involved.
Reflex A rapid, automatic, life-saving response that was present at birth. Eg. Blink-reflex.
Stimulus For example, light, heat, sound, gravity, smell, taste, or temperature.
Response This is the effect produced by an effector organ, for example you salivate when you taste something.
Co-ordination This means producing a sensible response when you are stimulated. For example, when you taste something nice you salivate, you don't scratch your toe.
8. EYES  
Cornea Curved transparent part at the front of the eye that refracts (bends) most light.
Iris Coloured part of the eye. Muscles can open or close the pupil to let more or less light in.
Accommodation The ‘fine – focussing’ of the eye carried out by the lens.
Retina Contains light sensitive cells. Rods are sensitive to dim light, cones work best in bright light and can detect colour (R,G,B)
Blind Spot Point where the optic nerve leaves the back of the eye.
Hormone Chemical released from a ductless gland. Hormones travel in the blood.
ADH Anti Diuretic Hormone - released from pituitary gland to control water loss from collecting ducts of kidney.
Insulin Released from ‘ islet cells ‘ of the pancreas. Insulin lowers blood glucose by helping liver cells to store glucose as glycogen.
Glucagon Hormone that raises blood glucose ( as does ‘Adrenalin’) in the opposite way to insulin.
Diabetic Person who cannot produce enough insulin. Glucose is detected in urine. Leads to coma and death unless treated with genetically engineered insulin.
FSH Follicle Stimulating Hormone – released from pituitary gland, causing an egg to develop in the female ovary.
Oestrogen Released from ovary as egg / follicle is developing. Causes uterus lining to thicken in preparation for a possible egg implantation. Inhibits FSH action.
LH Lutenising Hormone. Released from pituitary gland around ‘day 14’ of cycle. Causes the egg to be released from follicle.
Progesterone Last of the four hormones to be released in the cycle. Produced in ovary from the remains of the follicle. Keeps the uterus lining well supplied with blood. If no egg-implantation (‘pregnancy’), Progesterone levels fall and lining is lost (menstruation).
‘The Pill’ Contains oestrogen ( to prevent FSH working – hence no follicle can develop).
Nephron The functioning unit of a kidney. There are a million nephrons per kidney.
Cortex The outer layer of a kidney, containing glomeruli and Bowman’s Capsules
Medulla The middle layer of a kidney, containing collecting ducts and loops of henle.
Glomerulus (-i) A knot of capillaries where the blood is filtered out.
Bowman’s Capsule Surround the glomerulus and collects the filtrate.
First Coiled Tubule Where all glucose is reabsorbed back into blood. Also 95% of water and salts are re-absorbed here.
Loop of Henle Regulates water balance. Desert animals have longer Loops of Henle.
Collecting Duct Place where ADH (see above), acts to make final adjustments to water balance. More ADH = more water conserved by the body.
Osmoregulation The constant process of maintaining steady levels of water in the blood.
Homeostasis The constant process of maintaining steady levels of sugar, water, salt, temperature etc. in the body. Osmoregulation is an example of homeostasis.
DNA De-oxy-ribo-Nucleic-Acid. Long double-helix molecule responsible for the division of cells and having the code to make proteins for the cell.
Chromosomes Lengths of DNA found in the nucleus of cells. Human cells have 23 pairs of chromosomes
Genes Shorter lengths of DNA arranged along a chromosome. Each gene codes for a characteristic protein of the body.
Allele Each parent contributes one allele, making PAIRS of alleles in the offspring. So an allele is one-half of a gene.
Dominant The allele codes for the correct protein. Only one allele is needed (out of two) for this.
Recessive The allele has had a mutation at some point and no longer codes for the original protein. BOTH alleles must be recessive in order for the offspring to show the result.
Homozygous Both alleles are the same – either both dominant or both recessive.
Heterozygous Gene consists of one of each type (one dominant, one recessive)
Genotype The combination of alleles ‘homozygous dominant’, ‘heterozygous’ etc.
Phenotype The physical expression of the genotype – i.e. what the creature looks like.
Gamete Contains HALF the chromosome number of the parent
HGP Human Genome Project – set up to identify every one of the 20 000 genes in a human cell.
Clone An exact genetic copy of another cell – a result of mitosis.
Stem Cell A privileged cell from an embryo with the potential to be ‘cloned’ into any organ or tissue of the body.
Genetic Engineering The placing of a gene into a ‘foreign’ host DNA, so that the host produces a useful product of that gene eg. Human insulin gene inserted into bacteria.
Eutrophication Over-growth of algae in ponds and lakes, caused by nitrate fertilisers washing off from fields. When the algae finally die, oxygen levels of the water fall dangerously low.
Acid Rain Caused by emissions of NO2 and SO2 from fossil fuel combustion, which dissolve in rain water to form acids
‘Green house effect’ Carbon dioxide from combustion of fossil fuels traps long – wave radiation in the atmosphere. May result in changed weather patterns, melting of ice caps etc.
‘Ozone Hole’ Caused by release of CFC’s (chloro-fluoro-carbons) from refrigerators and air-con systems.
Alternative Fuel A more sustainable form of energy release that causes less pollution. Eg solar panels, wind turbines, bio-gas, hydro-electric, nuclear.