Unit 5 Biology

Question	Answer
Stimulus/Stimuli	A change in an organism's environment (internal or external) that can be detected by receptor cells.
Receptor	A specialised cell that detects stimuli and initiates nerve impulses. May be individual cells or concentrated in sense organs (e.g eye)
Taxis/Taxes	Behavioural response in which an organisms shows directional movement to (positive) or away (negative) from a stimulus.
Kinesis/Kineses	A change in the speed of random movement of an organism in response to a environmental stimulus.
Tropisms	Growth (in plants) in response to a directional stimulus. Can be positive (growing towards the stimulus) or negative (growing away from the stimulus)
Reflex	A reflex is a fixed movement of some part of an organism/animal in response to a particular stimulus.
Sensory Neurone	A nerve cell that carries impulses from a receptor to the CNS
Motor Neurone	A nerve cell that carries impulses away from the CNS to the effectors.
CNS	Central Nervous System - the brain & spinal cord. The CNS processes incoming information and produces a response.
Effectors	Organs that bring about a response - usually muscles or glands.
Myogenic	(E.G HEART) The muscle contraction originates from within the muscle itself.
Medulla Oblongata	Location of the cardiovascular centre that controls heart rate
Acetylcholine (Ach)	Neurotransmitter secreted from the synapses of many nerves, including most of the PNS.
Acetylcholinesterase	Enzyme found in the synaptic cleft of cholinergic nerves, where it breaks down the acetylcholine into Ethanoic Acid & Choline. Prevents overstimulation.
Actin	Protein found in muscle contraction.
Action Potential	A nerve impulse - a wave of depolarisation that spreads along the axon.
Addition (Genetics)	Type of genetic mutation in which a base is added, causing frameshift in one direction. Causes many codons to be changed.
Auxin	Plant growth regulator (aka plant hormone).
Adenyl Cyclase*	Enzyme in mechanism of hormone action. Activated when a hormone fits into a receptor cell on the cell surface membrane, which activates a second messenger, leading to enzymes in the cell being activated/deactivated.
Adrenaline	Fast-acting hormone. Secreted by adrenal glands. Prepares body for action; raised heartbeat, BP, and glucose levels.
Adrenergic Synapse	In the SNS, a synapse that secretes noradrenaline.
Anti-codon	Seq^n of 3 BASES found on tRNA that codes for a specific amino acid. Binds to complementary codon on mRNA during translation.
BMR	Basal Metabolic Rate. Measured as O2 consumption per unit body mass per unit of time when the organism is at rest.
Blind Spot	Point on the retina where the optic nerve joins. No rods/cones.
Carcinogen	A cancer causing agent.
Cholinergic Synapse	Synapse that secretes acetylcholine.
Cloning	The process of making a genetically identical copy.
Codon (aka triplet)	A group of three bases in DNA or RNA that codes for an amino acid.
cDNA	Complementary DNA which has been made from mature RNA by REVERSE TRANSCRIPTION.
Reverse Transcriptase	Enzyme that catalyses the process of reverse transcription.
Cyclic AMP	The second messenger in hormone action. The enzyme adenyl Cyclase turns ATP into this.
Cystic Fibrosis	Recessive genetic disease in which a faulty allele fails to make membrane protein CFTR. Symptom: buildup of sticky mucus in the lungs, pancreas, and reproductive system.
Degenerate Code	64 Codons, 20 amino acids. Some amino acids have more than one codon.
Deletion (Genetics)	Type of gene mutation in which a base is lost, causing a frameshift.
Dideoxy Sequencing	Technique used to find the base sequence of a piece of DNA.
DNA Polymerase	Enzyme that catalyses the addition of complementary nucleotides during DNA replication.
Ectotherm	An animal whose core body temperature is similar to that of the environment. They can thermoregulate, but only by modifying behaviour.
Endotherm	An animal that can maintain a stable core body temperature regardless of the environmental temperature.
EPSP	Excitatory PostSynaptic Potential - a charge that builds up in a neurone after synaptic transmission. If a threshold is exceeded, an impulse is generated.
Fovea	Region of the retina where cones are concentrated.
Frameshift	In mutation, a situation where a base is lost or added, causing all other bases to move along in a particular direction.
FSH	Follicle Stimulating Hormone
Glucagon	Hormone, secreted by alpha cells in the islets of Langerhans in the pancreas, in response to LOW BLOOD GLUCOSE LEVELS.
Gluconeogenesis	The production of new glucose from non-carbohydrate sources (e.g proteins or lipids). Happens during fasting/dieting/starving when glucose and glycogen levels are low.
Glycogen	The main storage carbohydrate in animals. Highly branched polymer of glucose.
Glycogenesis	The production of glycogen by the polymerisation of glucose.
Glycogenolysis	The breakdown of glycogen to release glucose. Stimulated (indirectly) by Glucagon.
Homeostasis	The ability of an organism to maintain a constant internal environment/maintained within certain limits.
Hormone	Chemical, secreted by endocrine glands, that has an effect on a target organ or cell.
Hypothalamus	Part of the brain which is sensitive to many different internal and external stimuli. Controls the secretions of the pituitary gland and the whole endocrine system. THERMOREGULATION. Heat loss/gain centres located here.
In Vitro	Carried out outside of an organism. "In Glass"
In Vivo	Process happening in living cells, tissues or whole organisms. "In Life"
Insulin	Hormone made by BETA cells in the islets of Langerhans (pancreas). Works by stimulating cells to open extra glucose channels in cell membranes, so it can leave the blood and enter cells where it can be metabolised.
Iodopsin	Light-sensitive pigment found in CONE CELLS on the retina.

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