Cell biology

Medicines often need to get inside cells to have their impact. They exert their effects in many different ways. Drugs work at the level of the cells of the body. There are several key principles of drug action:

• Most drugs act at specific receptorsreceptors
  Protein molecules attached to cells that only bind to specific molecules with a particular structure. on the external or internal cell membranemembrane
  A thin, flexible sheet-like structure that acts as a lining or a boundary in an organism. s of body cells
• Drugs interfere with the physiological or biochemical processes of the body or in the pathogens which cause disease
• Drugs often bind to a single type of receptor but this type of receptor may be present in many different types of cell.

Drugs may be taken into cells by diffusiondiffusion
The spreading out of the particles of a gas or any substance in solution down a concentration gradient. through the membrane, facilitated diffusion, active transportactive transport
The process which uses energy to move substances against a concentration gradient or across a partially permeable membrane using a special transport protein. or pinocytosispinocytosis
Energy-requiring process by which a cell takes small amounts of liquid into membrane-bound vesicles. .

Many drugs act as agonistagonist
Drugs that bind to receptors on or in a cell and stimulate a response. s or antagonistantagonist
Drugs that block receptors on or in a cell and prevent an unwanted response (in people) or may prevent a desirable response causing death (in pathogens). s. Agonists bind to receptors on or in a cell and stimulate a response. Antagonists block receptors on or in a cell and prevent an unwanted response (in people) or may prevent a desirable response causing death (in pathogens).

Medicines often affect cell membranecell membrane
The membrane which forms the boundary between the cytoplasm of a cell and the medium surrounding it and controls the movement of substances into and out of the cell. s or get inside of cells to have an effect. Understanding some of the ways different drugs work is a useful way of clarifying transport and control mechanisms in cells.

Antibioticantibiotic
Medicine that is used to treat bacterial infections and works by killing or stopping the growth and reproduction of bacteria. These can be specific to a particular bacteria or act on groups of related bacteria. s

Bacteriabacteria
Single-celled organism. Has a cell wall, cell membrane, cytoplasm. Its DNA is loosely-coiled in the cytoplasm and there is no distinct nucleus. are prokaryotes and there are many features of prokaryoticprokaryotic
A unicellular organism that lacks a membrane bound nucleus or any other membrane bound organelle. cells that are different from our eukaryoticeukaryotic
Cells that make up animals, plants, fungi and protista. They are three-dimensional, membrane-bound sacs containing cytoplasm, a nucleus and a range of membrane-bound organelles. cells. Antibiotics are drugs that target bacteria and cure bacterial diseases. They either kill the bacteria or stop them growing – but it is important that they do not destroy the human cells as well, so many of their actions affect bacterial cells only.

Animation showing how different antibioticantibiotic
Medicine that is used to treat bacterial infections and works by killing or stopping the growth and reproduction of bacteria. These can be specific to a particular bacteria or act on groups of related bacteria. s have their effect on bacteriabacteria
Single-celled organism. Has a cell wall, cell membrane, cytoplasm. Its DNA is loosely-coiled in the cytoplasm and there is no distinct nucleus. l cells in different ways:

Drugs affecting the nervous systemnervous system
The system which coordinates the actions of the body in response to changes in the environment using electrical signals travelling through a system of nerves.

Many drugs and poisons affect the nervous system in one way or another. They may increase or depress stimulation of particular nerve pathways, or block transmission of the impulse completely. They may bind to membranemembrane
A thin, flexible sheet-like structure that acts as a lining or a boundary in an organism. receptorsreceptors
Protein molecules attached to cells that only bind to specific molecules with a particular structure. or interfere with enzyme action inside or outside of the cell as in the diagram below.

Animation showing some of the ways different drugs affect the nervous systemnervous system
The system which coordinates the actions of the body in response to changes in the environment using electrical signals travelling through a system of nerves. at a cellular level: