QCAA Biology EA flashcards
QCAA Biology EA · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Prokaryotic cell
- A cell lacking a membrane-bound nucleus and organelles; its DNA is a single circular chromosome in the nucleoid, and it may contain plasmids.
- Eukaryotic cell
- A cell containing a membrane-bound nucleus and organelles such as mitochondria, endoplasmic reticulum and Golgi apparatus; found in protists, fungi, plants and animals.
- Fluid mosaic model
- The description of the plasma membrane as a phospholipid bilayer studded with proteins, cholesterol and glycolipids that move laterally, giving the membrane a mosaic appearance.
- Surface area to volume ratio
- The ratio of a cell's outer surface area to its internal volume; it decreases as cell size increases, limiting the efficiency of diffusion into and out of the cell.
- Mitochondrion
- A double-membraned organelle where aerobic cellular respiration occurs; the Krebs cycle takes place in the matrix and the electron transport chain on the inner membrane.
- Chloroplast
- A plant organelle containing thylakoids and stroma where photosynthesis occurs; light-dependent reactions happen on thylakoid membranes and the Calvin cycle in the stroma.
- Endomembrane system
- A network of membranes including the nuclear envelope, endoplasmic reticulum, Golgi apparatus, vesicles and lysosomes that synthesises, modifies, packages and transports proteins and lipids.
- Mitosis
- A type of cell division producing two genetically identical diploid daughter cells; used for growth, repair and asexual reproduction in multicellular organisms.
- Meiosis
- A reduction division producing four genetically varied haploid gametes from one diploid cell; involves two divisions and crossing over, generating genetic diversity.
- Homeostasis
- The maintenance of a relatively stable internal environment within narrow limits despite external changes, achieved mainly through negative feedback mechanisms.
- Negative feedback
- A control mechanism in which a deviation from a set point triggers a response that reverses the deviation, restoring the internal environment toward its normal range.
- Positive feedback
- A control mechanism in which a change is amplified rather than reversed; examples include oxytocin release during childbirth and clotting cascades.
- Thermoregulation
- The control of body temperature through physiological responses such as sweating, vasodilation, shivering and vasoconstriction, and behavioural responses such as seeking shade.
- Osmoregulation
- The control of water and solute balance in the body, regulated by ADH released from the posterior pituitary, which increases water reabsorption in kidney collecting ducts.
- Insulin
- A hormone released by pancreatic beta cells when blood glucose is high; it promotes cellular glucose uptake and glycogen formation, lowering blood glucose concentration.
- Glucagon
- A hormone released by pancreatic alpha cells when blood glucose is low; it promotes glycogen breakdown and gluconeogenesis, raising blood glucose concentration.
- Nephron
- The functional unit of the kidney; filtration occurs at the glomerulus, reabsorption in the proximal tubule, and fine-tuning of water and salts in the loop of Henle and collecting duct.
- Alveolus
- A tiny air sac in the lungs with thin walls, a moist surface and a large total surface area; the site of gas exchange between air and blood.
- Guard cells
- Pairs of specialised epidermal cells surrounding a stoma; they open the stoma when turgid and close it when flaccid, regulating gas exchange and water loss.
- Semi-conservative replication
- The process by which DNA is copied so that each new double helix contains one original parental strand and one newly synthesised complementary strand.
- Transcription
- The synthesis of mRNA from a DNA template by RNA polymerase in the nucleus; the mRNA carries the genetic message to ribosomes for translation.
- Translation
- The process on ribosomes where tRNA delivers amino acids in the order specified by mRNA codons, forming a polypeptide chain.
- Codon
- A sequence of three nucleotides in mRNA that specifies a particular amino acid or a stop signal during translation; the genetic code is degenerate and universal.
- Law of segregation
- Mendel's principle that the two alleles of a gene separate during gamete formation, so each gamete receives only one allele.
- Independent assortment
- Mendel's principle that alleles of different genes on different chromosomes are distributed to gametes independently of one another during meiosis.
- Genotype
- The combination of alleles present in an organism for a particular gene or set of genes; for example, homozygous dominant, heterozygous or homozygous recessive.
- Phenotype
- The observable characteristics of an organism resulting from the interaction of its genotype with the environment.
- Test cross
- A cross between an individual of unknown genotype and a homozygous recessive individual, used to determine whether the unknown is homozygous dominant or heterozygous.
- Frameshift mutation
- A mutation caused by the insertion or deletion of nucleotides not in multiples of three, shifting the reading frame and altering all downstream amino acids.
- Species richness
- The number of different species present in a community; one component of species diversity, along with species evenness.
- Simpson's diversity index
- A measure of biodiversity calculated as D = 1 − Σ(n/N)², where n is the number of individuals of each species and N is the total number of individuals; higher values indicate greater diversity.
- Trophic level
- A feeding position in a food chain, such as producer, primary consumer or secondary consumer; energy decreases at each successive level.