definitions

Question 1

activation energy

Answer 1

the activation energy is the energy required to bring about a reaction. it is lowered by the presence of enzymes

Question 2

active immunity

Answer 2

resistance to disease resulting from an individuals own immune system whereby an antigen induces plasma cells to produce antibodies

Question 3

active transport

Answer 3

movement of substances fromn an area of low concentration to an area of high concentration, requiring the expendature of metabolic energy

Question 4

allele

Answer 4

one of a number of alternative forms of a a gene. e.g the shape of a pea gene has 2 alleles

Question 5

antibody

Answer 5

a protein produced by lymphocytes in response to an appropriate antigen

Question 6

antibiotic

Answer 6

a substance produced by living organisms to destroy or inhibit microorganisms

Question 7

autosomes

Answer 7

a chromosome that is not a sex chromosome

Question 8

apoplastic pathway

Answer 8

route through cell walls and intercellular spaces in plants by which water and dissolved substances are transported

Question 9

anticodon

Answer 9

a sequence of 3 adjacent nucleotides on a molecule of tRNA that is complementary to a codon on mRNA

Question 10

biodiversity

Answer 10

the range and variety of genes, species and habitats in a particular region

Question 11

biomass

Answer 11

the total mass of living material measured in a specific period over a given period of time

Question 12

carcinogen

Answer 12

a chemical, form of radiation or other agent that causes cancer

Question 13

chromatid

Answer 13

one of the two strands of a chromosome that are joined together by a single centromere prior to cell division

Question 14

chromatin

Answer 14

the material that makes up chromosomes. it consists of DNA and a protein histone

Question 15

chromosome

Answer 15

a thread like structure made of protein and DNA by which hereditary is physically passed from one generation to the next

Question 16

codon

Answer 16

a sequence of 3 adjacent nucleotides in mRNA that codes for one amino acid

Question 17

condensation

Answer 17

chemical process by which two molecules combine to form a more complex one with the elimination of a simple substance, usually water.

Question 18

co transport

Answer 18

the transport of another substance coupled with the transport of another substance across a plasma membrane in the same direction with the same protein carrier

Question 19

crossing over

Answer 19

the process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that their alleles are explained

Question 20

denaturation

Answer 20

permanent changes due to the unraveling of the three-dimensional structure of a protein as a result of factors such as change in temperature or pH

Question 21

diffusion

Answer 21

the movement of molecules or ions from a region where they are in high concentration to one where their concentration is lower

Question 22

diploid

Answer 22

a term applied to cells in which the nucleus contains two sets of chromosomes

Question 23

endocytosis

Answer 23

the inward transport of large molecules through the cell-surface membrane

Question 24

facilitated diffusion

Answer 24

diffusion involving the presence of protein carrier molecules to allow the passive movement of substances across plasma membranes

Question 25

gene pool

Answer 25

the total number of alleles in a particular population at a specific time

Question 26

habitat

Answer 26

the place where an organism normally lives and which is characterised by physical organisms present

Question 27

haploid

Answer 27

term referring to cells that contain only single copy of each chromosome

Question 28

homologous chromosome

Answer 28

a pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features. they are not necessarily identical however, as individual alleles may vary.

Question 29

hydrolysis

Answer 29

the breaking of large molecules into smaller ones by the addition of water molecules.