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Cell theory
Theory that states that all organisms are composed of cells, and that all cells come from pre-existing cells
Coarse focus
Dial used to initially focus a light microscope on a specimen
Differentiation
The alteration of a cell's morphology and physiology through changes in gene expression
Emergent property
A property of a system that emerges from the interaction of the elements of the system
Gene expression
The synthesis of a functional gene product, often protein, but also rRNA, tRNA or snRna
Growth
An increase in physical size
Homeostasis
The process in which an organism regulates activities within cells and their bodies to keep conditions stable
Magnification
Ratio of image size to actual size
Metabolism
The sum of all chemical reactions that occur within an organism or within a cell
Objective lens
The part of the microscope that gathers light from the specimen and focuses it to produce a real image
Paramecium
Genus of single-celled ciliated organisms
Reductionism
An approach to science that holds that a complex system can be best understood as the sum of its parts, and that variables can be studied in isolation
Response
In behavioural science, the behaviour that is the consequence of a stimulus
Scale bar
A means of visually indicating the magnification of an image
Stargardt's disease
A degenerative eye disease that has been the target of stem cell research
Stem cell
A relatively undifferentiated cell that can give rise to other types of cells and retains the ability to divide
System
A level of organisation that emerges due to the interaction of elements
Tissue
A group of cells with a common function and structure
Amphipathic
Molecule that has hydrophobic and hydrophilic regions
Cholesterol
A lipid that prevents the membrane from becoming too fluid and also prevents it from crystallising
Davson-Danielli model
Model of the cell membrane in which the phospholipid bilayer is between two layers of protein
Electron carriers
Proteins arranged in chains on the membrane to allow the transfer of electrons from one carrier to another
Fluid mosaic model
A model conceived by S.J Singer and Garth Nicolson in 1972 to describe the observed structural features of biological membranes
Fluidity
Refers to the viscosity of a lipid bilayer of the membrane that allows it to change shape
Glycoproteins
Proteins that contain oligosaccharide chains
Hormone-binding sites
Proteins on the outside of the membrane that allow specific hormones to bind
Hydrophilic
Molecules that are attracted to water
Hydrophobic
Molecules that are not attracted to water but are attracted to each other
Integral proteins
Proteins imbedded in the phospholipid bilayer
Peripheral proteins
Proteins on the surface of the plasma membrane
Permeability
The rate of passive diffusion of molecules through the membrane, which depends on the electric charge, size and polarity of the molecule
Phospholipid bilayer
Two layers of phospholipids arranged so that their hydrophobic tails are projecting inwards while their polar head groups are on the outside surfaces
Phospholipids
A lipid consisting of a glycerol bound to two fatty acids and a phosphate group
Singer-Nicholson model
Current model of membrane structure that incorporates a fluid mosaic structure in a discontinuous lipid bilayer
Transport pumps
Proteins in the plasma membrane that release energy and use it to move substances across the membrane
Endosymbiotic theory
A theory that some eukaryotic organelles, such as mitochondria and chloroplasts, originated as free-living prokaryotes that invaded primitive eukaryotic cells
Genetic code
A nearly universal sequence of nucleotides in DNA that determines the specific amino acid sequence in the synthesis of proteins
Louis Pasteur
French scientist that proved, among other things, that the emergent growth of bacteria in nutrient broths is due to biogenesis, not spontaneous generation
Spontaneous generation
Old theory that believed on the formation of living organisms from non-living matter
Sterilisation
Technique used for the elimination of microbiological organisms to achieve a sterile microbial environment
Anaphase
The stage of mitosis and meiosis in which the chromosomes move to opposite ends of the nuclear spindle
Binary fission
A type of asexual reproduction common among prokaryotes where one cell divides giving rise to two cells, each having the potential to grow to the size of the original cell
Cancer
General term for more than 100 diseases that are characterised by uncontrolled, abnormal growth of cells
Cell plate
A membrane that forms midway between dividing plant cells during cytokinesis and later becomes the cell wall
Centrioles
A self-replicating cylindrical organelle that is involved in the process of nuclear division
Centromere
The region joining the two sister chromatids where it becomes attached to the spindle fibres
Chromosomes
Linear strand of DNA bonded to proteins in the nucleus of eukaryotic cells that carries the genetic information
Cyclins
A family of closely related proteins that regulate the cell cycle in eukaryotic cells
Cytokinesis
The division of the cytoplasm and the plasma membrane, following the division of the nucleus, resulting in two cells in mitosis
Equatorial plate
The figure formed by the chromosomes in the centre of the spindle during mitosis
Metaphase
Stage in mitosis in which chromosomes be coma arranged at the equatorial plate
Metastasis
Characteristic of malignant tumours of transferring the disease from one organ to another not directly with it
Microtubule fibres
Hollow protein tubes seen during the mitosis of animal cells
Mitosis
The process where a single cell divides into two identical cells, each containing the same number of chromosomes and genetic content as that of the original cell
Mitotic index
The ratio between the number of cells in mitosis to the total of cells
Mutagens
Chemical agents that increase the rate of genetic mutation
Oncogens
A gene that causes normal cells to change into cancerous tumour cells
Prophase
First stage of mitosis during which the chromosomes become visible as pairs chromatids and the nuclear envelope disappears
Sister chromatids
Two identical strands of DNA joined by a common centromere
Spindle fibres
Network of filaments that collectively from a mitotic spindle in mitosis. They are involved in moving the chromosomes during nuclear division
Supercoiling
Twisting in the opposite direction to the turns of the double helix during the first stage of mitosis
Telophase
The final stage of mitosis in which the separated chromosomes reach the opposite poles of the dividing cell and the nuclei of the daughter cells form around them
Tumours
Abnormal proliferation of cells, either benign or malignant
Active transport
Movement of substances across membranes using energy in the form of ATP
ATP
(Adenosine triphosphate) energy molecule
Concentration gradient
A gradient resulting from an unequal distribution of ions across the cell membrane
Diffusion
Passive movement of particles from a region of higher concentration to a region of lower concentration
Endocytosis
The process in which the cell takes in materials from the outside by infolding of the membrane to form a vesicle
Exocytosis
The process in which the cell releases materials to the outside by discharging them as membrane-bounded vesicles that pass trough the cell membrane
Facilitated diffusion
Diffusion through a membrane that requires a protein
Hypertonic
A more concentrated solution relative to another fluid
Hypotonic
A less concentrated solution relative to another fluid
Osmoregulation
Control of the water balance of a living organism
Osmosis
Passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration
Secretion
When material is released from a cell
Semi-permeable membrane
Membrane that allows some substances to diffuse through but not others
Transport pumps
Proteins in the plasma membrane that use ATP to move substances across the membrane
Vesicles
A bubble-like membranous structure that stores and transports cellular products
Note 
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