serious life processes chaoter 1

accuracy (of experimental results)

Closeness of an experimental result to its true value.

active site

Area on the surface of an enzyme where the substrate attaches and products are formed.

active transport

Movement of molecules or ions against a concentration gradient, using energy from respiration.

adenosine triphosphate (ATP)

Chemical present in all cells which acts as an energy 'currency'. ATP is made by respiration and used up by any process that needs a supply of energy.

aerobic respiration

Reaction that releases energy from food. Uses oxygen and produces carbon dioxide and water.

agar

Jelly-like substance used as a culture medium for growing microorganisms.

algae

Photosynthetic protoctists. Mostly unicellular, some multicellular forms (seaweeds).

anaerobic respiration

Reaction that releases energy from food, without using oxygen. Produces lactate in mammals, carbon dioxide and ethanol in yeast.

bacteria (singular = bacterium)

Small single-celled organisms with no nucleus.

capsule (of bacteria)

Slime layer covering some bacterial cells. Protects the bacterium and stops it drying out.

catalyst

Chemical that increases the rate of a reaction but remains unchanged at the end of the reaction.

cell membrane

Thin surface layer around the cytoplasm of a cell. Forms a partially permeable barrier between the cell contents and the outside of the cell.

cell wall

Non-living layer outside the cell membrane of certain types of cell. Made of cellulose (plants and algae), chitin (fungi) or peptidoglycan (bacteria).

cell

Basic structural unit of living organisms.

chitin

Substance that makes up the cell wall of fungi and the outside skeleton of insects.

control

Part of an experiment which is set up to show that other variables are not having an effect on the outcome of the experiment.

controlled variables

Variables in an experiment other than the independent variable, which are kept constant by the person carrying out the experiment so that they do not affect the results.

cytoplasm

Jelly-like material that makes up most of a cell; the site of chemical reactions of a cell.

denaturing

Process where the structure of a protein is damaged by high temperatures (becomes denatured). If the protein is an enzyme, it will no longer catalyse its reaction.

differentiation

Process taking place during the development of an embryo, where cells become specialised to carry out particular functions.

diffusion

Movement of molecules or ions down a concentration gradient.

enzyme

Protein that acts as a biological catalyst.

eukaryotic

Cells that have a nucleus (the cells of all living organisms except bacteria).

lactate

Waste product of anaerobic respiration in muscle cells.

lock and key model

Model of enzyme action where the substrate is the 'key', fitting into the 'lock', which is the active site of the enzyme.

metabolism

Chemical reactions taking place inside cells.

mitochondrion (plural = mitochondria)

Organelle that carries out aerobic respiration, releasing energy for the cell. Place where most of the cell's ATP is made.

multicellular

Composed of many cells.

nucleus

Cell organelle that contains chromosomes. Controls the activities of the cell.

organ system

Collection of different organs working together, e.g. the heart and blood vessels of the circulatory system.

organ

Structure in the body of an animal or plant that is a collection of different tissues working together to perform a function.

organelle

Part of the cell with a particular function, e.g. the nucleus.

osmosis

Net diffusion of water molecules across a partially permeable membrane from a solution with a high water potential to a solution with a low water potential.

partially permeable membrane

Membrane (e.g. the cell surface membrane) that is permeable to some molecules but not permeable to others.

precision

(of experimental results) Smallest increment that can be usefully measured, i.e. the smallest division on the scale of any measuring instrument being used.

reliability

(of experimental results) Measure of how similar the results are, if the experiment is carried out several times.

respiration

Chemical reaction taking place in cells, where glucose is broken down to release energy.

selectively permeable

A membrane that allows certain molecules or ions to pass through it by means of active or passive transport.

substrate

Molecule upon which an enzyme acts.

tissue

Collection of similar cells working together to perform a function.

vacuole

Membrane-bound space in a plant cell, filled with a solution of sugars and salts called cell sap.