Bacterial conjugation

Bacterial conjugation, cutaway artwork. Conjugation is a form of sexual reproduction in which pieces of DNA (deoxyribonucleic acid) called plasmids (circular, shown in the cutaway portions) are transferred between bacteria through a structure called a pilus.

Antibiotic resistance

Artwork of bacterial cells becoming resistant to antibiotics. This resistance is acquired from a donor cell's plasmid (circular unit of deoxyribonucleic acid, DNA), which has resistance seen at upper left (red/yellow, red is resistance). Viral transmission involves a virus (pink, lower left) obtaining a resistant gene, and passing it to a bacterial cell that incorporates it into its plasmid. Bacterial cells also acquire segments of DNA released from dead cells (upper left). Mutations (not seen) may also occur, which may be antibiotic resistant and thus allow the bacteria to survive and reproduce.

Human immune response

Human immune response. Computer artwork showing the interactions of the various white blood cells (purple) involved during an immune response in the human body. Red blood cells (red, round) can also be seen in a blood vessel (bottom), in which the white blood cells migrate to the site where they are needed.

Human papilloma virus

Human papilloma virus (HPV). The protein coats, or capsids enclose their genetic material. The capsids are studded with surface proteins. HPV causes warts, which commonly grow on the hands, the soles of the feet, the body's mucous membranes and the genitals. It has also been linked with some skin and cervical cancers. The papilloma virus belongs to the papovavirus group, most of whose members are capable of inducing non- malignant tumours.

Blood pressure measurement

Blood pressure measurement. Doctor holding the pump of a sphygmomanometer as he measures a patient's blood pressure. Blood pressure is an important measure of health. High blood pressure (hypertension) puts a great deal of strain on the heart, and is one of the major risk factors in heart attacks and strokes.

Bacteriophage viruses

Bacteriophage viruses. Computer artwork of T- bacteriophages, or phages (small particles in image), infecting E. coli bacterium cells (larger, cylindrical particles in image). Phages are viruses that infect bacteria. T-phages consist of an icosahedral (20- sided) head, which contains the genetic material (either DNA or RNA), and a thick tail with several bent tail fibres. The tail is used to inject the genetic material into the host cell to infect it. The phage then uses the bacterium's genetic machinery to replicate itself. When a sufficient number have been produced the phages exit the cell by lysis, a process that kills the cell.

Insulin receptor, molecular model

Insulin receptor. Molecular model of the insulin receptor molecule (brown, orange, blue, grey and mauve) bound to an insulin molecule (red and yellow). Both the surface structure (blobs) and secondary structure (ribbons) of the receptor are shown. The insulin receptor is a transmembrane protein, that is it spans the cellular membrane (yellow and cream). Binding of insulin to the extracellular part of the protein activates a number of changes inside the cell that lead to the uptake of glucose, the synthesis of glycogen and fatty acids and glycolysis, the production of energy from glucose.