Biology definitions from aqa specification

monomers

the smaller repeating units from which larger molecules are made

Condensation reaction

joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

Hydrolysis reaction

breaks a chemical bond between two molecules and involves the use of a water molecule.

Monosaccharides

monomers from which larger carbohydrates are made

Glyosidic bond

formed from a condensation reaction between two monomers

Amino acids

monomers from which proteins are made

DNA molecule

double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs.

RNA molecule

relatively short polynucleotide chain

ATP structure

a nucleotide derivative and is formed from a molecule of ribose, a molecule of adenine and three phosphate groups.

Large latent heat of vaporisation

providing a cooling effect with little loss of water through evaporation

High heat capacity

buffering changes in temperatures

Cytokinesis

division of cytoplasm into two cells

Simple diffusion

movement of small/non polar molecule from area of high concentration to area of low concentration, through phospholipid membrane.

facilitated diffusion

movement of larger/polar molecules from area of high concentration to a area of low concentration through channel/carrier proteins in the phospholipid membrane.

Osmosis

the passage of water from a region of high water potential to a region where its water potential is lower, through a selectively permeable membrane.

Active transport

movement of a substance from a region where it is in a low concentration to a region where it is in a high concentration. The process energy released from hydrolysis of ATP.

Antigen

molecule that triggers a immune response by lymphocytes

Antibody

a protein produced by lymphocytes in response to the presence of the appropriate antigen.

Active immunity

resistance to disease resulting from the activities of an individual's own immune system whereby an antigen induces plasma cells to produce antibodies.

Passive immunity

resistance to disease that is acquired from the introduction of antibodies from another individual, rather than an individual's own immune system

Locus

fixed position of a gene on a particular DNA molecule

Histones

proteins that associate wit DNA of eukaryotic cells to form chromosomes

Intron

non coding DNA

Exon

DNA that codes for genetic sequences

Universal

same base pairs code for the same amino acid

Non overlapping

codons do not share amino acids

Degenerate

more than one codon codes for the same amino acid

codon

sequence of three adjacent nucleotides in mRNA that code for one amino acid.

Genome

complete set of genes in a cell

proteome

range of proteins that a cell is able to produce

transcription

production of mRNA from DNA

Translation

production of polypeptides from sequence of codons carried by mRNA.

meiosis

2 nuclear divisions result in formation of 4 genetically different haploid daughter cells from a single diploid parent cell.

Genetic diversity

number of different alleles of genes in a population

Species

a group of organisms that can breed together to produce fertile offspring.

Hierarchy

which smaller groups are placed within larger groups, with no overlap between groups.

species richness

measure of the number of different species in a community.

index of diversity

relationship between the number of species in a community and the number of individuals in each species.

Gross primary production

chemical energy store in plant biomass, in a given area or volume.

Net primary production

chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.

Homeostasis in mammals

physiological control systems that maintain the internal environment within restricted limits.

Negative feedback

restores systems to their original level

Genotype

genetic constitution of an organism.

Phenotype

expression of this genetic constitution and its interaction with the environment.

Population

group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed.

Evolution

Change in allele frequencies in a population.

Community

populations of different species.

Ecosystem

A community and the non-living components of its environment.

Carrying capacity

size of a population that a species can supports

Conservation

method of maintaining ecosystems and the living organisms that occupy them. It requires planning and organisation to make best use of resources while preserving the natural landscape and wildlife.

Succession

Change in a ecosystem over time