AQA BIOLOGY
Enzyme
- a protein or RNA that acts as a catalyst and so alters the speed of a biochemical reaction.
Epidemiology
- the study of the spread of disease and the factors that affect this spread.
Eukaryotic cell
- a cell that has a membrane-bound nucleus and chromosomes. The cell also possesses a
variety of other membranous organelles, such as mitochondria and endoplasmic reticulum.
Facilitated diffusion
- diffusion involving the presence of protein carrier molecules to allow the passive movement
of substances across plasma membranes.
Gamete
- reproductive (sex) cell that fuses with another gamete during fertilization.
Gene
- section of DNA on a chromosome coding for one or more polypeptides.
Gene pool
- the total number of alleles in a particular population at a specific time.
Habitat
- the place where an organism normally lives and which is characterized by physical
conditions and the types of other organisms present.
,Haemoglobin
- globular protein in blood that readily combines with oxygen to transport it around the body.
It comprises four polypeptide chains around an iron-containing haem group.
Haploid
- term referring to cells that contain only a single copy of each chromosome, e.g. the sex cells
(gametes)
High-density lipoprotein (HDL)
- a compound of protein and lipid molecules found in blood plasma. It transports cholesterol
from other cells to the liver.
Histmine
- substance released on tissue injury that causes dilation of blood vessels.
Homologous chromosomes
- a pair of chromosomes, one maternal and one paternal, that have the same gen loci and
therefore determine the same features. They are not necessarily identical, however, as
individual alleles of the same gene may vary, e.g. one chromosome may carry the allele for
blue eyes, the other the allele for brown eyes, they are capable of pairing during meiosis.
Human genome
- the totality of the DNA sequences on the chromosomes of a single human cell.
Hydrogen bond
- chemical bond formed between the positive charge on a hydrogen atom and the negative
charge on another atom of an adjacent molecule, e.g. between the hydrogen atom of one
water molecule and the oxygen atom of an adjacent water molecule.
Hydrolysis
, - the breaking down of large molecules into smaller ones by the addition of water molecules.
Immunity
- the means by which the body protects itself from infection.
Interspecific variation
- differences between organisms of different species.
Intraspecific variation
- differences between organisms of the same species.
Ion
- an atom or group of atoms that has lost or gained one or more electrons. Therefore have
either a positive or negative charge.
Ion channel
- a passage across a cell-surface membrane made up of a protein that spans the membrane
and opens and closes to allow ions to pass in and out of the cell.
Isotonic
- solutions that possess the same concentration of solutes and therefore have the same water
potential.
Isotope
- variations of a chemical element that have the same number of protons and electrons but
different numbers of neutrons. While their chemical properties are similar they differ in mass.
One example is carbon which has a relative atomic mass of 12 and an isotope with a relative
atomic mass of 14.
Enzyme
- a protein or RNA that acts as a catalyst and so alters the speed of a biochemical reaction.
Epidemiology
- the study of the spread of disease and the factors that affect this spread.
Eukaryotic cell
- a cell that has a membrane-bound nucleus and chromosomes. The cell also possesses a
variety of other membranous organelles, such as mitochondria and endoplasmic reticulum.
Facilitated diffusion
- diffusion involving the presence of protein carrier molecules to allow the passive movement
of substances across plasma membranes.
Gamete
- reproductive (sex) cell that fuses with another gamete during fertilization.
Gene
- section of DNA on a chromosome coding for one or more polypeptides.
Gene pool
- the total number of alleles in a particular population at a specific time.
Habitat
- the place where an organism normally lives and which is characterized by physical
conditions and the types of other organisms present.
,Haemoglobin
- globular protein in blood that readily combines with oxygen to transport it around the body.
It comprises four polypeptide chains around an iron-containing haem group.
Haploid
- term referring to cells that contain only a single copy of each chromosome, e.g. the sex cells
(gametes)
High-density lipoprotein (HDL)
- a compound of protein and lipid molecules found in blood plasma. It transports cholesterol
from other cells to the liver.
Histmine
- substance released on tissue injury that causes dilation of blood vessels.
Homologous chromosomes
- a pair of chromosomes, one maternal and one paternal, that have the same gen loci and
therefore determine the same features. They are not necessarily identical, however, as
individual alleles of the same gene may vary, e.g. one chromosome may carry the allele for
blue eyes, the other the allele for brown eyes, they are capable of pairing during meiosis.
Human genome
- the totality of the DNA sequences on the chromosomes of a single human cell.
Hydrogen bond
- chemical bond formed between the positive charge on a hydrogen atom and the negative
charge on another atom of an adjacent molecule, e.g. between the hydrogen atom of one
water molecule and the oxygen atom of an adjacent water molecule.
Hydrolysis
, - the breaking down of large molecules into smaller ones by the addition of water molecules.
Immunity
- the means by which the body protects itself from infection.
Interspecific variation
- differences between organisms of different species.
Intraspecific variation
- differences between organisms of the same species.
Ion
- an atom or group of atoms that has lost or gained one or more electrons. Therefore have
either a positive or negative charge.
Ion channel
- a passage across a cell-surface membrane made up of a protein that spans the membrane
and opens and closes to allow ions to pass in and out of the cell.
Isotonic
- solutions that possess the same concentration of solutes and therefore have the same water
potential.
Isotope
- variations of a chemical element that have the same number of protons and electrons but
different numbers of neutrons. While their chemical properties are similar they differ in mass.
One example is carbon which has a relative atomic mass of 12 and an isotope with a relative
atomic mass of 14.
