LC Biology flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Hypothesis
- A testable, falsifiable prediction about the relationship between variables; it must be supported or rejected by experimental evidence rather than by opinion.
- Independent variable
- The factor deliberately changed or manipulated by the investigator in an experiment, so that its effect on the measured dependent variable can be observed.
- Binomial nomenclature
- The two-part scientific naming system in which the genus name is capitalised and the species name is lowercase, both italicised, for example Homo sapiens.
- Benedict's test
- A test for reducing sugars in which the sample is heated with blue Benedict's reagent; a green to brick-red precipitate indicates increasing sugar concentration.
- Biuret test
- A qualitative test for protein in which Biuret reagent added to the sample changes from blue to purple or violet when peptide bonds are present.
- Rf value
- In chromatography, the distance travelled by a pigment divided by the distance travelled by the solvent front; it is constant for a substance under fixed conditions.
- Enzyme active site
- The specific region of an enzyme where the substrate binds; its shape is complementary to the substrate, giving enzymes their specificity.
- Denaturation
- Loss of an enzyme's three-dimensional shape and active site caused by high temperature or extreme pH, permanently destroying catalytic function.
- Bile function
- Bile, made in the liver and stored in the gall bladder, emulsifies lipids into small droplets, increasing surface area for lipase digestion.
- Villus
- A finger-like projection of the small intestine lining containing blood capillaries and a lacteal, increasing surface area for absorption of digested nutrients.
- Osmosis
- The passive movement of water across a selectively permeable membrane from a region of higher water potential to a region of lower water potential.
- Active transport
- Movement of ions or molecules against a concentration gradient using carrier proteins and energy from ATP, as in root hair cells absorbing minerals.
- Mitosis
- Nuclear division producing two genetically identical diploid daughter cells; it underlies growth, repair and asexual reproduction in organisms.
- Meiosis
- Two successive nuclear divisions producing four genetically varied haploid gametes, with crossing over and independent assortment generating genetic variation.
- Fluid mosaic model
- Description of the cell membrane as a phospholipid bilayer with embedded proteins, cholesterol and glycoproteins that can move laterally within the layer.
- Semi-conservative replication
- DNA replication in which the double helix unwinds and each original strand acts as a template, so each new molecule keeps one parental strand.
- Monohybrid ratio
- The outcome of crossing two heterozygotes for one gene, giving a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio in the offspring.
- Restriction enzyme
- An enzyme that cuts DNA at a specific recognition sequence, producing fragments used in genetic engineering and gel electrophoresis.
- Aerobic respiration
- The controlled release of energy from glucose using oxygen, producing carbon dioxide, water and ATP in the cytoplasm and mitochondria.
- Anaerobic respiration
- Release of energy from glucose without oxygen, producing lactic acid in muscle cells or ethanol and carbon dioxide in yeast.
- Limiting factor
- The factor in shortest supply that restricts the rate of a process such as photosynthesis, even when other factors are increased.
- Capture-recapture
- A population estimate method in which animals are caught, marked and released, then a second sample is taken; N equals marked times total caught divided by recaptures.
- Eutrophication
- Nutrient enrichment of water by fertiliser runoff causing algal blooms, decomposition and oxygen depletion that kills aquatic animals.
- Nitrogen fixation
- Conversion of atmospheric nitrogen into ammonia or nitrates by bacteria such as Rhizobium in root nodules, making nitrogen available to plants.
- Trophic level
- A feeding position in a food chain, such as producer, primary consumer or secondary consumer, through which energy passes.
- ADH
- Antidiuretic hormone released by the pituitary gland; it increases water reabsorption in the kidney tubules, producing smaller volumes of concentrated urine.
- Alveolus
- A tiny air sac in the lungs with thin, moist walls and a rich blood supply, providing a large surface area for gas exchange.
- Reflex arc
- The neural pathway of an involuntary response, passing from receptor through sensory, relay and motor neurones to an effector.
- Counter-current flow
- Arrangement in fish gills where blood flows opposite to water, maintaining a diffusion gradient and maximising oxygen uptake.
- Menstrual cycle hormones
- FSH stimulates follicle development, oestrogen thickens the uterus lining, LH triggers ovulation and progesterone maintains the lining.
- Transpiration
- Loss of water vapour from plant leaves through stomata, creating the pull that draws water up the xylem from the roots.
- Phototropism
- Growth response of a plant shoot toward light, caused by auxin accumulating on the shaded side and stimulating greater cell elongation there.