Glossary of Terminology 

Amino acids:
The basic units of proteins, each amino acid has a NH₂-C(R)-CO₂H structure, with a variable R-group. There are altogether 20 types of amino acids.

Antibodies:
Alsp known as Immunoglobulins (Ig). Diverse molecules that binds to specific antigens and illicits an immune response.

Albumin:
Gobular proteins found in the blood which as as transport molecules within the circulatory system.

B cells:
Also known as B Lymphocytes. A class of white blood cells which carry out humoral immune response. They mature in the bone marrow.

Cholesterol:
The precursor from which other steroids, such as the sex hormones, are synthesised. They are also important components of animal cell membranes, although a high concentration of cholesterol in the blood may contribute to atherosclerosis.

Cystic duct:
The duct which converges with the left and right hepatic ducts to form the common bile duct.

Cytokines:
Molecules which are secreted by one cell as a regulator of neighbouring cells.

Cytoplasm:
A structureless matrix found in cells made up of 90% water, organic molecules, inorganic ions and waste products. It acts as a store of vital chemicals and is the site of vital chemical pathways, such as glycolysis, and protein synthesis (translation).

Cytotoxic cells:
T cells which are able to destroy infected cells and cancer cells.

DNA:
Deoxyribonucleic acid. This makes up the genetic information found in all living cells.

DNA polymerase:
An enzyme which catalyses the replication of DNA.

Enzymes:
Biological catalysts which speed up the rate of chemical reactions in biological systems. They are made up of protein, usually in the globular form, and are sensitive to fluctuations in pH and temperature from the optimum.

Erythrocytes:
Also known as red blood cells.

Fatty acids:
Long-chain unbranched carboxylic acids. An major constituent of fatty acid lipids, e,g, triacylglycerides.

Ferritin:
The form in which iron obtained from the breakdown of old erythrocytes is stored in the liver. It is a complex of iron abd beta-globulin.

Gallbladder:
A small pear-shaped organ 3 to 6 inches in lenght, and lies under the liver in the upper right side of the abdomen. It is a reservoir for bile.
 
Gastrointestinal tract:
Also known as the digestive tract.

Genome:
The genetic complement of a cell.

Globulin:
Very large golbular proteins in the blood that transport hormones, cholesterol, lipids, iron and vitamins.

Glucagon:
A pancreatic enzyme which catalyses glycogenolysis.

Glycerol:
An important constituent of triacylglycerides, which contains three carbon atoms, each attached to three hydroxyl groups.

Glycogen:
A major storage polysaccharide in animals, a polymer of glucose molecules.

Glycogenolysis:
The release of glucose molecules from glycogen stored in the liver, catalysed by glucagon.

Haemoglobin:
A globular protein found in red blood cells which play a vital role in oxygen transport. It exhibits quartenary structure, with 2 alpha-subunits and two beta-subunits. Each subunit has a heme group, which is the essential site for oxygen binding.

Hepatocytes:
Also known as liver cells

Hexose sugar:
Sugars with 6 carbon atoms, each attached to 6 hydroxyl groups. e.g. glucose, galactose, fructose.

Hydrophobic:
"Water fearing"; does not mix with water.

Immune system:
Our body's natural defense system, involving antibodies and a class of white blood cells called lymphocytes.

Inferior vena cava:
One of the two blood vessels which directs blood from lower systemic circulation in the veins back into the right atrium.

Kidney:
A pair of bean-shaped organs which play a crucial role in regulating the amount of waste materials and other chemicals in our blood. It also maintains our blood volume at a constant level.

Lipase:
An enzyme which catalyses the breakdown of fats.

Macrophage cells:
White blood cells that roam the body, engulfing bacteria and the debris of dead cells by phagocytosis. The largest, most effective and longest-living phagocytic cells.

Major histoincompatibility complex (MHC):
A collection of surface antigens (proteins) which belong to either Class 1 or Class 2 subtypes. The surface antigens are coded for in the major histoincompatibility gene complex. Class 1 MHC antigens are found on almost every cell in the body. Class 2 MHC antigens are restricted to macrophages and B-cells.

Methylation:
The addition of a -CH₃ group to a chemical substance.

Monocytes:
White blood cells that circulate in the blood for a few hours, then migrate into tissues where they develop into macrophages.

Natural killer cells:
White blood cells that do not attack microorganisms directly, but rather destroy the body's own infected cells, especially cells that harbour viruses, which can reproduce within host cells. They also kill aberrant cells that could form tumours. The mode of attack is not by phagocytosis but by lysis of the target cell.

Oxidation:
Occurs during a chemical reaction, and involves either the addition of oxygen, the removal of hydrogen, or the increase in the oxidation number of a substance.

Pancreas:
A pink slender organ between the stomach and the small intestine that consists mostly of exocrine tissue that produces digestive enzymes and exports them to the small intestine via the pancreatic duct. It also contains endocrine cells, the Islets of Langerhans, which produce the hormones insulin and glucagon.

Plasma:
The liquid matrix in which the blood cells and blood proteins are suspended in. It contains an extensive variety of solutes dissolved in water. Water accounts for about 90% of blood plasma.

Phagocytosis:
The act of "engulfing".

Phospholipids:
Essential component of all cell membranes. A phospholipid molecule is amphipatic, i.e. it contains both hydrophobic and hydrophilic parts. They are structurally related to fats, but have only two fatty acid molecules rather than three. The third fatty acid is replaced by a phosphoric acid group.

Polysaccharide:
A large molecule (macromolecule) made up of many units of simple sugars chemically linked together by glycosidic linkages.

Protein:
Large molecule made up of many amino acids chemically linked together by amide linkages. Biologically important as enzymes, structural protein and connective tissue.

Reduction:
Occurs during a chemical reaction, and involves the removal  of oxygen, the addition of hydrogen, or the reduction in the oxidation number of a substance.

Respiration:
The process of extracting energy from food consumed. Can be crudely viewed as "breathing".

Stomach:
An organ located on the left side of the abdominal cavity, just below the diphragm. It is the vital organ which stores consumed food and also carries out the first steps of food digestion.

T cells:
Also known as T lymphocytes. White blood cells which function in cell-mediated response. They originate from stem cells in the bone marrow but mature in the thymus.

Tumours:
A lump due to uncontrolled cell division, and may be benign or malignant. Malignant tumours cause cancer. Tumours are able to spread to other parts of the body (metastasize) and begin secondary growths at these other sites.

Virus:
Disease-causing agents which are much smaller than bacteria. They also contain genetic information, either in the form of DNA or RNA. They are able to replicate inside host cells.

Vitamins:
Important cofactors which are required by some enzymes for their normal functioning. 

References:
Hwa Chong Junior College, 1996, Biology lectures
Neil.A.Campbell, 1993, Biology 3rd Edition 

For more Information :
Dr Sing Kong Yuen

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