Topic 1 Cell Biology Review

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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