biology overall

• Abiotic components


  Components of an ecosystem that are non living
• Abiotic factors


  Non living components of an ecosystem that effect other living organisms
• Acetycholine


  Chemical that acts as a transmitter that diffuses across synaptic cleft
• Acetycholinesterase


  Enzyme in synaptic cleft that breaks down acetycholine. After it has triggered an action potential in the post synaptic neurone, acetycholine must be broken down otherwise it would remain in the synaptic cleft and continue to open sodium ion channels in the post synaptic membrane causing action potentials
• Acinus (plural acini)


  Small group of exocrine cells in a sac like structure. in the pancreas these surround a tubule and secrete into the tubule
• Action potential


  A brief reversal of teh potential across the membrane of a neurone causing a peak of +40mV compared to the resting potential of -60mV
• Adenyl cyclase


  An intracellular enzyme that converts ATP to cyclic AMP (CAMP)
• ADP


  Adenosine diphosphate
• Adrenal cortex


  Outer layer of the adrenal gland
• Adrenal gland


  One of the pair of glands lying above kidneys, which release adrenaline and a number of hormones known as corticoids (or corticosteroids) such as aldosterone
• Adrenaline


  Hormone released from medulla of adrenal glands which stimulates body to prepare for fight or flight
• Adrenal medulla


  Inner layer of adrenal gland
• Adrenocorticotropic hormone (ACTH)


  Hormone released by pituitary gland which stimulates adrenal cortex to produce corticosteroid hormones
• Actin and myosin


  Proteins involved in muscular contraction
• Agar


  Polysacharide of galactose obtained from seaweed which is used to thicken a medium into a gel.
• Agarose


  Type of sugar that can incorporated into a type of agar gel
• Alkaloids


  Organic nitrogen containing bases that have important physiological effects on animals, includes nicotine, quinine, strychnine and morphine
• Allele


  Version of a gene
• Allele frequency


  Propotion of a particular allele within the gene pool
• Allopatric speciation


  Formation of 2 different species from one original one due to geographic isolation
• Alpha cells


  Cells found in islets of langerhans that secrete glucagon
• Ammonification


  Production of ammonia by bacterial action in the decay of nitrgenous organic matter
• AMP


  Adeonside monophosphate
• Aneuploidy


  Abnormal chromosome number
• Antagonist


  Something that works against the other in opposite pairs, such as in the muscles that are arranged in opposing pairs, so one contracts and the other elongates
• ADH (antidiuretic hormone)


  Hormone made in hypothalamus, stored and released from pituitary gland, that controls permeability of collecting duct in walls of kidneys
• Apical dominance


  Inhibition of lateral buds fruther down shoot by chemicals produced by apicial bud at tip of plant shoot.
• Apoptosis


  Programmed cell death
• Artificial selection


  Selective breeding of organisms to produce desired phenotypes
• Ascending limb


  Part of loop of Henle that carries fluid back into distal tubule in cortex
• ATP


  Adenosine triphosphate
• Autoimmune response


  Response in which body's immune system attacks and destroys some of its own cells.
• Autonomic nervous stsrem


  Part of nervous system responsible for controlling involuntary motor activities of body
• Autoradiograms


  Photographs made when photographic film is exposed to molecules labelled with radioactivity
• Autosomal linkage


  Gene loci present on the same autosome (non sex chromosome) are often inherited together
• Autosome


  Chromosome not concerned with sex determination
• Autotrophic nutrition


  Nutrition where organic molecules are synthesised from inorganic molecules, i.e carbon dioxide and water. I.e photosynthesis where sunlight energy converted to chemical energy to synthesise large organic molecules from smaller inorganic ones. Chemosynthesis uses energy derived from chemical reactions (e.g nitrifying bacteria in soil)
• Auxins

  E.g IAA (indole 3 acetic acid)

  Promotes cell elongation

  Inhibits leaf abcission

  Inhibits growth of side shoots- maintains apical dominance

  Involved in tropisms

  Stimulates release of ethene

  Involved in food ripening
• Cytokines


  Promotes cell division

  Leaf expansion

  Delays leaf senescense

  Overcomes apicial dominance
• Ethene


  Promotes food ripening

  Promotes abscission in deciduous trees