IB Biology Topic 1: Cell Biology

Cell theory

The theory that cells form the fundamental structural and functional units of all living organisms.

Differentiation

The expression of a particular gene(s) and not others in order for cell specialisation.

Emergent properties

The idea that the sum of an organism is more than the parts interacting and combining. Living things become more complex as they move (from individual cells to organ systems).

Multicellular

An organism made out of more than one cell.

Specialisation

The structural adaption of a cell to suit a particular function (Eg: Red blood cells have no nucleus to make room for space to carry oxygen).

Stem Cells

Undifferentiated cells that have a capacity to divide into cells of the similar type, or to specialise into different types of cells.

Surface Area to Volume Ratio

The amount of surface area per unit of volume for an object. Has effect on the size a cell can grow.

Unicellular

A single-celled organism that carries out all the functions of life by itself.

Binary fission

division of pre-existing cells or by prokaryotic cells for asexual reproduction. Single chromosome is replicated and moves to the opposite ends of the cell and detaches to form a copy of the chromosome.

Eukaryotic

have compartments for the chromosomes, this has advantages such as the pH and other damaging substances are maintained within the membrane of an organelle.

Gamete

a mature sexual reproductive cell, as a sperm or egg, that unites with another cell to form a new organism.

Mitochondria

responsible for aerobic respiration. Converts chemical energy into ATP (Adenosine Triphosphate) using oxygen.

Prokaryotic

simplest cell structure without compartments or a nucleus. Have naked DNA and no mitochondria. Filled with cytoplasm.

Amphipathic

(of a molecule, especially a protein) having both hydrophilic and hydrophobic parts.

Cholesterol

a compound of the sterol type found in most body tissues. Cholesterol and its derivatives are important constituents of cell membranes and precursors of other steroid compounds, but high concentrations in the blood are thought to promote atherosclerosis.

Fluid Mosaic Model

A model that describes the structure of cell membranes. In this model, a flexible layer made of lipid molecules is interspersed with large protein molecules that act as channels through which other molecules enter and leave the cell.

Hydrophilic

attracted to water

Hydrophobic

repelled by water

Integral Protein

a type of membrane protein that is permanently attached to the biological membrane.

Peripheral Protein

proteins that adhere only temporarily to the biological membrane with which they are associated. These molecules attach to integral membrane proteins, or penetrate the peripheral regions of the lipid bilayer.

Phospholipid Bilayer

a two-layered arrangement of phosphate and lipid molecules that form a cell membrane, the hydrophobic lipid ends facing inward and the hydrophilic phosphate ends facing outward.

Artificial cell

is an engineered particle that mimics one or many functions of a biological cell.

Amphipathic

having both hydrophilic and hydrophobic parts.

Bilayer

a film two molecules thick (formed e.g. by lipids), in which each molecule is arranged with its hydrophobic end directed inwards towards the opposite side of the film and its hydrophilic end directed outwards.

Cell division

the division of a cell into two daughter cells with the same genetic material.

Endocytosis

the taking in of matter by a living cell by invagination of its membrane to form a vacuole.

Endosymbiotic

a smaller organism that lives within another organism, the theory of how eukaryotic cells were formed.

Gene

a unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Hypothesis

a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation.

Nucleus

a dense organelle present in most eukaryotic cells, typically a single rounded structure bounded by a double membrane, containing the genetic material.

Polymer

a substance which has a molecular structure built up chiefly or completely from a large number of similar units bonded together.

Spontaneous generation

the supposed production of living organisms from nonliving matter, as inferred from the apparent appearance of life in some supposedly sterile environments.

Zygote

a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.

Endocytosis

The taking in of matter by a living cell by invagination of its membrane to form a vacuole.

Golgi apparatus

A complex of vesicles and folded membranes within the cytoplasm of most eukaryotic cells, involved in secretion and intracellular transport.

Exocytosis

A process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

Simple diffusion

The term simple diffusion refers to a process whereby a substance passes through a membrane without the aid of an intermediary such as a integral membrane protein.

Osmosis

A process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one

Facilitated diffusion

Facilitated diffusion (also known as facilitated transport or passive-mediated transport) is the process of spontaneous passive transport (as opposed to active transport) of molecules or ions across a biological membrane via specific transmembrane integral proteins.

Active transport

The movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.

Mitosis

A type of cell division that results in two daughter cells each having the same number of chromosomes as the parent nucleus.

G1 phase

Stage at which cellular components(excluding chromosomes) are replicated.

S phase

Chromosomes are duplicated.

G2 phase

Cell rechecks duplicated chromosomes to repair any mistakes.

Chromosome

A threadlike structure made up of nucleotides and proteins, carry genetic information.

Sister chromatids

A pair of identical replicated DNA connected at the centromere.

Centromere

The point at which sister chromatids are attached.

Supercoiling

Repeatedly coiling DNA molecule to make chromosome shorter and wider.

Cytokinesis

Cytoplasmic division at the end of cell division, resulting in two daughter nuclei.

Cyclins

Proteins involved in the control of the cell cycle.

Mutagens

An agent that is carcinogenic.

Oncogens

A gene in which under certain circumstances, may become cancerous.

Metastasis

The growth of a secondary tumor away from the primary site.