definitions Flashcards
absorption
the movement of digested food molecules through the wall of the intestine into the blood or lymph
accommodation
the change of shape of the lens, in order to focus on objects at different distances
active immunity
defence against a pathogen by antibody production in the body
active site
the part of an enzyme molecule into which its substrate fits
active transport
the movement of molecules and ions in or out of a cell through the cell membrane, from a region of their higher concentration against a concentration gradient, using energy released during respiration
adaptation (adaptive feature)
a feature of an organism that helps it survive in its environment
adaptive features
the inherited functional features of an organism that increase its fitness
adipose tissue
tissue made up of cells in which fat is stored
adrenaline
a hormone secreted by the adrenal glands, which prepares the body for “flight or fight”
adult stem cell
a cell in an adult that can give rise to a limited range of specialised cells
aerobic respiration
the release of a relatively large amount of energy in cells by the breakdown of nutrient molecules in the presence of oxygen
allele
any of two or more alternative forms of a gene
alimentary canal
part of the digestive system; a long tube running from mouth to anus
alveolus (plural: alveoli)
an air sac in the lungs, where gas exchange occurs
amino acids
molecules that can link together in long chains to form proteins; they contain carbon, hydrogen, oxygen and nitrogen, and sometimes sulfur
amniotic fluid
fluid secreted by the amnion, which supports and protects a developing fetus
amylase
an enzyme which breaks down starch to maltose
anaerobic respiration
the release of a relatively small amount of energy by the breakdown of nutrient molecules in the absence of oxygen
anatomy
the detailed body structure of an organism
anther
the part of a stamen in which pollen is produced
antibiotic
a drug that kills bacteria in the human body, without damaging human cells
antibodies
chemicals secreted by lymphocytes, which attach to antigens and help to destroy them
antigens
chemicals on the surfaces of pathogens, which are recognised as foreign by the body
artery
a blood vessel that carries blood away from the heart
artificial selection
the choice by a farmer or grower of only the “best” parents to breed, generation after generation
asexual reproduction
the process resulting in the production of genetically identical offspring from one parent
assimilation
the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
atrioventricular valves
valves between the atria and ventricles in the heart that prevent blood flowing from the ventricles to the atria
auto-immune disease
a disease caused by a persons own immune system attacking parts of their body
auxin
a plant hormone that causes cells to elongate
axon
a nerve fibre that conducts impulses away from the cell body
balanced diet
a diet containing some of each of the different types of nutrients, in a suitable quantity and proportions
base
in DNA, one of four substances (A, C, G and T) that make up the genetic code
bile
a liquid made in the liver, stored in the gall bladder and emptied into the small intestine, where it helps to emulsify fats
binomial
a two-word Latin name for a species of organism
biuret test
a test for protein
breathing
muscular movements which cause air to move into and out of the lungs
bronchioles
the small tubes into which the bronchi branch
bronchus (plural: bronchi)
one of the two tubes into which the trachea branches, carrying air into each lung
capillaries
a tiny blood vessel that delivers blood to tissues
carbohydrase
an enzyme that catalyses the breakdown of carbohydrates
carbohydrates
starches and sugars
carcinogen
a substance which increases the risk of a persons body developing cancer
cardiac muscle
the muscle of which the heart is made
carnivore
an animal that gets its energy by eating other animals
carpel
the female part of a flower
catalase
an enzyme found in almost all living tissues, which catalyses the breakdown of hydrogen peroxide to water and oxygen
catalyst
a substance that speeds up a chemical reaction and is not changed by the reaction
cell membrane
a very thin layer of fat and protein that surrounds every living cell
cell sap
a solution of sugars and other substances inside the vacuole of a plant cell
