AS Level Biology

Activation Energy

The energy that needs to be supplied before a chemical reaction will start

Active site

the part of an enzyme where a substrate molecule binds

Active transport

Movement of molecules and ions across a plasma membrane against the concentration gradient using energy

adaptation

A characteristic that increases an organism's chances of survival

Affinity for Oxygen

the tenancy a molecule gas to bind with oxygen

Allele

an alternative form of a gene

Aeolus

a microscopic air sac in the lungs where gas exchange occurs

Amino Acid

A monomer of proteins

Aneurysm

A balloon like swelling of an artery

Antibiotic

A chemical used to teat bacterial diseases

Antibiotic Resistance

When bacteria are able to survive in the presence of antibiotics

Antibody

A protein produced by B cells in response to the presence of a pathogen

Antigen

A molecule found on the surface of a cell. A foreign antigen triggers an immune response.

Antigenic Variability

Where pathogens change their antigens

Apoplast pathway

A route that water takes through a plant root to the xylem through cell walls.

Arteriole

A blood vessel that branches off an artery

Asthma

A respiratory condition where the airways become inflames and irritated, usually because of an allergic reaction to substances such as pollen and dust

Atheroma

A fibrous plaque caused by the build up and hardening of white blood cells, lipids and connective tissue

Atrioventricular node

A group of cells in the heart wall that are responsible for passing waves of electrical activity from the SAN onto the bundle of his

Atrioventricular valve

A valve in the heart linking the atria to the ventricles

B cell

a type of white blood cell involved in the immune response, it produces antibodies

Base

A nitrogen containing molecule that forms part of a DNA nucleotide

Benedict's test

A biochemical test for the presence of sugars

Biodiversity

The variety of living organisms and ecosystems on earth

Biuret test

A biochemical test for the presence of polypeptides and proteins

Bohr effect

An effect by which an increase of carbon dioxide in the blood results in a reduction of hemoglobin's affinity for oxygen

Bundle of His

A group of muscle fibers in the heart responsible for conducting waves of electrical activity from the AVN to the purkyne fibers

Carbohydrase

An enzyme that catalyzes the hydrolysis of carbohydrates

Cardiac Cycle

An ongoing sequence of conraction and relaxation of the atria and ventricles that keeps blood continuously circulating blood round the body

Cardiac output

The volume of blood pumped by the heart per minute

Cardiovascular disease

any disease associated with the heart and blood vessels

Casparian strip

a waxy strip in the cell wall of an endodermis cell

Catalyst

A chemical that speeds up a chemical reaction without being used up or changed itself.

Causal relationship

Where a change in one variable causes a change in another

Cell fractionation

A method that separates the organelles in a cell

Cellular immune response

the immune response that involves T cells

Cellulose

A polysaccharide made of long unbranched chains of beta glucose

Centrometer

The point at which two strands of a chromosome are joined together

Chloroplast

An organelle present in plant cells where photosynthesis occurs

Chromatid

One arm of a double stranded chromosome

Chromosome

A thread like structure made up of one long DNA molecule

Competitive inhibitor

A molecule that had a similar shape to a sbstrate and blocks an enzymes active site

Condensation reaction

A reaction that releases a small molecule (usually water) when it links molecules together

Conjunction

When two bacteria come together and exchange genetic material

Control experiment

An extra experiment set up to eliminate the effect of some variables that cannot be controlled

Control Group

A group in a study that is treated in exactly the same way as the experimental group apart from the factor you're investigating

Control Variable

A variable you keep constant throughout an experiment

Coronary artery

A artery supplying the heart muscle with blood

Correlation

A relationship between two variables

Cortex (plants)

The outer later of cells n a plant root

Counter Current System

The system in which blood flows in one direction and water flows in the opposite direction across the gills of a fish

Crossing over

When chromatids twist around each other and bits of them swap over during meiosis

Cytoplasm

A gel like system where most of the chemical reactions in a cell happen

Denatured

The point at which an enzyme no longer functions as a catalyst

Deoxyribose

The pentose sugar in DNA

Dependent variable

the variable you measure

Dicotyledonous plant

A type of flowering plant

Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration

Digestion

The process of breaking down food into substances that can be used by the body

Dipeptide

A molecule formed from two amino acids

Diploid

When a cell contains two copies of each chromosome

Disaccharide

A molecule formed from two monosaccharides

Deoxyribonucleic acid

The molecule in cells that stores genetic information

DNA helicase

An enzyme that breaks the hydrogen bodns between two polynucleotide DNA strands during DNA replication

DNA hybridisation

A technique that combines single stranded DNA sequences from two species to determine how similar they are

DNA polymerase

An enzyme that joins together the nucleotides on a new strand of DNA during DNA replication

DNA sequencing

the process of determining the base order of a section of DNA

Double blind trial

A study involving a control group and an experimental group where neither the scientists nor the participants know which group the participants are in

Double helix

the structure of a DNA molecule

Emphysema

A lung disease caused by smoking or long term exposure to air pollution where foreign particles become trapped in the alveoli

Endodermis

A single layer of cells between the cortex and xylem

Endoplasmic reticulum

A system of membranes enclosing a fluid filled space which is involved with lipid and protein processing

Endothelium

the inner lining of a blood vessel

Enzyme

A protein that lowers the activation energy by providing an alternative diffusion pathway

Enzyme-Substrate Complex

The intermediate formed when a substrate molecule binds to the active site of an enzyme

Episermis

The outer most layer of cells on a leaf

Eukaryote

Organism made up of a cell containing a nucleus

Exon

A section of DNA within a gene that codes for amino acids

Facilitated diffusion

the diffusion of particles through carrier proteins or channel proteins in the plasma membrane

Fibrosis

The formation of scar tissue in the lungs which can be the result of an infection or exposure to substances such as asbestos

Fluid mosaic model

A model describing the arrangement of molecules in a cell membrane

Founder effect

The reduction in genetic diversity that occurs when just a few organisms from a population start a new colony

Gamete

A sex cell

Gene

a section of DNA which codes for a protein

Gene flow

Different alleles being moved between populations when individuals migrate from one population to another

Genetic bottleneck

an event that causes a big reduction in a population and reduces genetic diversity

Genotype

the alleles an organism has

Glycogen

A polysaccharide made from a long very branched chain of alpha clucose

Glycosidic bond

A bond formed between monosaccharides

Golgi apperatus

A group of fluid filled flattened sacs involved with processing and packaging lipids and proteins and making lysosomes

Granum

A structure in chloroplasts formed from the stacking of thylakoid membranes

Guard Cell

A cell that controls the opening and closing of a stomata

Haemoglobin

An oxygen carrying protein found in red blood cells

Haploid

When a cell contains one copy of each chromosome

Heart rate

the number of heart beats per minute

Heard immunity

Where vaccinated people are protected because the occurrence of the disease is reduced by the number of people who are vaccinated

Histone

Protein that DNA is wound around in order to fit into the nucleus

Homologous pair

A pair of matching chromosomes, each chromosome containing the same gene but different alleles

Horizontal gene transmission

When genes are passed on horizontally to other members of the same or different species without reproduction occurring

Humoral immune response

The immune response that involves B Cells and the production of antibodies