G Flashcards
G Protein
Type of trimeric membrane protein, associated with specific transmembrane receptors, that plays a role in signal transduction.
G proteins bind guanine nucleotides; when bound to GDP the G protein is inactive, but when bound to GTP it is active. The alpha subunit of the G protein moves through the membrane and acts in subsequent steps in the signal transduction pathway.
G Protein–Coupled Receptor
A transmembrane receptor that interacts with a G protein.
GABA
gamma-aminobutyric acid
A neurotransmitter; primarily inhibitory in the vertebrate central nervous system.
Gallbladder
An organ that stores bile produced in the liver.
Gamete
The germ cell of sexually reproducing species; small gametes are sperm and large gametes are ova.
Gametogenesis
Production of mature gametes in the ovary or testis.
Ganglion
plural: ganglia
A cluster of neuronal cell bodies. Ganglia act as integrating centers.
Ganglion Cell
An interneuron in the retina of vertebrates.
Gap Junction
Aqueous pore between two cells that allows ions and small molecules to move freely from cell to cell; formed by proteins called connexins in the vertebrates and innexins in the invertebrates.
Gas Gland
A region of the vasculature of the swim bladder that secretes gases.
Gastric
Pertaining to the stomach.
Gastrointestinal Tract
The digestive tract, alternately termed GI tract, or intestinal tract.
Gastrovascular Cavity
A space that performs the functions of digestion and circulation; found in organisms such as cnidarians.
Gene
A region of DNA that, when transcribed, encodes a protein or an RNA.
Gene Duplication
The process of DNA mutation by which a genome can acquire an additional copy of genes.
Generator Potential
A change in the membrane potential in the sensory terminal of a primary afferent neuron. It is a graded potential proportional to the signal intensity.
If it exceeds threshold, it will trigger action potentials in the axon of the sensory neuron.
Genetic Drift
A change in gene frequencies in a population over time as a result of random events.
Genome
All of the genetic material of an organism; the complete set of DNA in both the nucleus and mitochondria.
Genotype
The specific genetic makeup of an organism.
Germ Cell
A cell that produces the haploid gametes of a sexually reproducing species.
Gestation
The period of embryonic development within the uterus of a viviparous or ovoviviparous species.
Giant Axons
Unusually large-diameter axons that are present in some invertebrates and vertebrates.
Gills
Respiratory surfaces that originate as out-pocketings of the body surface; generally used for gas exchange in water.
Gland
A specialized organ that secretes hormones.
Glial Cells (glia)
A group of several types of cells that provide structural and metabolic support to neurons.
Gliocytes
A type of invertebrate glial cell.
Gliotransmitters
Chemicals released from glial cells that influence communication among neurons and glia.
Globin
The protein component of hemoglobins.
Globulins
A type of protein found in blood. Alpha and beta globulins are transport proteins; gamma globulins are involved in the immune system.
Glomerular Filtration Rate (GFR)
The total amount of filtrate per unit time passing through the glomeruli into the tubules of the kidneys.
Glomerulus
A knot-like cluster of capillaries that acts as a biological filter in the nephrons of many vertebrate kidneys. It permits fluids and small molecules to pass freely from the plasma to the tubule lumen.
Glottis
A small flap of tissue located between the pharynx and trachea of air-breathing vertebrates.
Glucagon
A hormone produced by the vertebrate pancreas that inhibits glycogen synthesis and stimulates glycogen breakdown, resulting in an increase in blood glucose.
Glucocorticoids
Steroid hormones involved in the stress response that regulate carbohydrate, protein, and lipid metabolism.
Gluconeogenesis
The production of glucose from non-carbohydrate precursors; the
main part of the pathway is a reversal of glycolysis, enabled by three enzymes that bypass the two irreversible steps in glycolysis.
Glycogen
A glucose polysaccharide that forms the main carbohydrate energy store of animals.
Glycogenesis
Synthesis of glycogen from glucose or glycolytic intermediates.
Glycogenolysis
The breakdown of glycogen to form glucose-6-phosphate.
Glycolipid
A glycosylated lipid common in the extracellular side of some plasma membranes.
Glycolysis
The breakdown of carbohydrates to form pyruvate, or when oxygen is limiting, other end products such as lactate.
Glycoprotein
A protein that has been modified by the addition of carbohydrates.
Glycosaminoglycan
A non-proteinaceous component of the extracellular matrix.
Glycosuria
High levels of glucose in the urine.
Glycosylation
The addition of carbohydrate groups to proteins, lipids, or carbohydrates within the endoplasmic reticulum or Golgi apparatus.
Goblet Cell
A goblet-shaped mucus-secreting cell found in the intestinal and respiratory surfaces.
Goldman Equation
The equation that predicts the membrane potential across a cell membrane resulting from the distribution of multiple ions in relation to their permeabilities.
Golgi Apparatus
An intracellular organelle involved in the processing of proteins prior to export.
Gonadotropin
A hormone that regulates the activity of reproductive tissues; FSH and LH are the main gonadotropins in vertebrates, and allatotropin and allatostatin are the main gonadotropins in arthropods.
Gonads
The organs that produce the gametes in males (testes) and females (ovaries).
Gonadotropin-Releasing Hormone (GnRH)
A hypothalamic hormone that regulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary of vertebrates.
Gonadotropins
A family of proteins, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), and chorionic gonadotropin (CG).
Graded Potential
Changes in the membrane potential of a cell that vary in magnitude with the stimulus intensity; results from the opening and closing of ion channels.
Graham’s Law
Describes the rate of diffusion of a gas in liquid; states that the rate of diffusion of a gas is proportional to its solubility and inversely proportional to the square root of its molecular mass.
Granulosa Cells
The inner layer of somatic cells of a follicle that surround the primary oocyte.
Gray Matter
see also white matter
Areas of the vertebrate central nervous system that are rich in cell bodies.
Growth Factor
A group of peptide hormones that stimulate cells to proliferate (hyperplasia) or grow in size (hypertrophy).
Growth Hormone
A peptide hormone derived from the anterior pituitary that mediates somatic cell growth.
Guanine
A purine nitrogenous base component of nucleotides, including nucleic acids.
Guanosine
A nucleoside of guanine and a ribose sugar.
Guanosine Triphosphate (GTP)
A high-energy phosphate compound in energy metabolism; also the substrate for guanylate cyclase, forming the second messenger cGMP.
Guanylate Cyclase
Enzyme that converts GTP to cGMP in response to signaling molecules such as nitric oxide; has soluble and membrane-bound forms.
Gustation
Detection of ingested chemicals: the sense of taste.
Gustducin
A G protein–coupled receptor involved in the sense of taste that detects sweet tastants.
Gut Reactor Theory
Mathematical explanation of the optimal function of various types of digestive tracts, modeled after chemical reactors.
Gyri
singular: gyrus
Wrinkles on the surface of the brains of many mammals.
