NSSCAS Biology 8223 flashcards
NSSCAS Biology 8223 · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Prokaryotic ribosome type
- 70S ribosomes are found in prokaryotes; they are smaller than the 80S eukaryotic ribosomes and are not attached to membrane-bound organelles.
- Resolution
- The minimum distance at which two points can be seen as separate objects. It depends on the wavelength of the radiation used and limits useful magnification.
- Condensation reaction
- A reaction in which two molecules join with the loss of a small molecule, usually water. It forms glycosidic, peptide and ester bonds between monomers.
- Benedict's test
- A test for reducing sugars: add Benedict's reagent and heat in a water bath; a brick-red precipitate forms if a reducing sugar is present.
- Induced-fit model
- The active site of an enzyme is not exactly complementary to the substrate but moulds slightly around it when the enzyme-substrate complex forms, straining bonds.
- Competitive inhibitor
- A molecule similar in shape to the substrate that binds to the active site and blocks it. Its effect is reduced by increasing substrate concentration.
- Fluid mosaic model
- A model of membrane structure in which a phospholipid bilayer contains proteins, cholesterol and glycoproteins that can move within the membrane.
- Osmosis
- The net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.
- Anaphase
- A stage of mitosis in which centromeres divide and spindle fibres pull chromatids to opposite poles, so each pole receives one copy of each chromosome.
- Crossing over
- Exchange of sections of chromatids between homologous chromosomes at chiasmata during prophase I of meiosis, producing new combinations of alleles.
- Semi-conservative replication
- DNA replication in which each new DNA molecule contains one original strand and one newly synthesised strand, because each strand acts as a template.
- Transcription
- The synthesis of mRNA from a DNA template strand by RNA polymerase, with uracil pairing with adenine, before mRNA leaves the nucleus.
- Translocation
- The movement of sucrose and amino acids in phloem sieve tubes from sources, where they are made, to sinks, where they are used or stored.
- Cohesion-tension theory
- Water molecules cohere in the xylem as transpiration pulls from the leaves, creating tension that draws a continuous water column up the plant.
- Counter-current flow
- The flow of water over fish gills in the opposite direction to blood flow, maintaining a diffusion gradient along the whole gill lamella.
- Anaerobic respiration
- Respiration without oxygen: glucose is partially broken down to lactate in mammals or ethanol and carbon dioxide in yeast, releasing a small amount of ATP.
- Photolysis
- The splitting of water molecules by light energy in the thylakoid membranes, producing electrons, protons and oxygen as a by-product.
- Limiting factor
- The factor in shortest supply that restricts the rate of a process such as photosynthesis; increasing it raises the rate until another factor limits.
- Negative feedback
- A control mechanism in which a change from the norm is detected and a response reverses it, restoring the internal environment towards its set point.
- Resting potential
- The potential difference across a neurone membrane when not conducting an impulse, typically about −70 mV, maintained by the sodium-potassium pump.
- Lincoln index
- A method of estimating population size: multiply the number in the first sample by the number in the second sample, then divide by the number of marked recaptures.
- Climax community
- The final, stable stage of succession, in which the species composition remains roughly constant because the community is in equilibrium with the environment.
- Cell fractionation
- The process of breaking cells open in a cold, isotonic, buffered solution and centrifuging at increasing speeds to separate organelles by density.
- Phospholipid
- A lipid made of glycerol joined to two fatty acids and one phosphate group, giving a hydrophilic head and hydrophobic tails that form bilayers.
- Active site
- The region of an enzyme where the substrate binds; its shape and charge are complementary to the substrate and determine enzyme specificity.
- Water potential
- The potential of water molecules to move; pure water at standard conditions has a water potential of 0 kPa, and adding solute lowers it.
- Meiosis
- A reduction division producing four genetically different haploid cells from one diploid cell, involving two divisions, crossing over and independent assortment.
- Codon
- A sequence of three bases on mRNA that codes for a specific amino acid or a stop signal during translation at the ribosome.
- Transpiration
- The loss of water vapour from the leaves of a plant through stomata, mainly by evaporation from the surfaces of mesophyll cells.
- Glycolysis
- The first stage of respiration in the cytoplasm, where glucose is split into pyruvate, producing a net gain of two ATP and two reduced NAD.
- Calvin cycle
- The light-independent stage of photosynthesis in the stroma, where carbon dioxide is fixed onto RuBP and reduced to triose phosphate using ATP and reduced NADP.
- Synapse
- A junction between a neurone and another cell where a neurotransmitter is released across a cleft to transmit a signal to the postsynaptic membrane.
- Ecosystem
- A community of interacting organisms together with the abiotic factors of their environment, through which energy and nutrients flow.