1.2: Cell structure and organisation

Multicellular

Multicellular

Made up of more than one cell.

Specialised

Cells that are adapted to carry out a particular function.

Ultrastructure

Detailed structure of a cell.

Prokaryote

Cell lacking a nucleus and membrane-bound organelles.

Eukaryote

Cell containing a nucleus and other organelles bound by membranes.

Cell membrane

Thin layer of tissue made of proteins and phospholipids.

Organelles

Tiny cell structures that carry out a specific function within the cell.

Cytoplasm

A jellylike fluid inside the cell in which the organelles are suspended.

Nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction.

Nuclear envelopes

A double membrane that surrounds the nucleus in the cell.

Nuclear pores

Holes in the nuclear envelope that allow materials to pass in and out of the nucleus.

Chromatin

Fluid inside the nucleus.

Nucleolus

Found inside the nucleus and produces ribosomes.

Mitochondria

Site of ATP synthesis.

Cristea

Inner folds in the mitochondria that increase surface area so more ATP can be produced.

Matrix

A solution containing many compounds, inside the mitochondria.

ER

A system of membranes that is found in a cell's cytoplasm and that assists in the production, processing, and transport of proteins and in the production of lipids.

Cisternae

Flattened, membrane-bound compartments that make up the ER and the golgi body.

Rough ER

ER that is dotted with ribosomes, transports the proteins made by them.

Smooth ER

ER that is free of ribosomes. Associated with synthesis and transport of lipids.

Ribosomes

Site of protein synthesis.

Large subunit

Biggest part of the ribosome; two tRNA attatchment sites.

Small subunit

Smallest part of the ribosome; one mRNA attatchment sites.

Golgi body

A structure in a cell that receives proteins and other newly formed materials from the ER, packages them, and distributes them to other parts of the cell.

Vesicles

Small membrane sacs that specialize in moving products into, out of, and within a cell.

Lumen

Space within the golgi body.

Lysosome

An organelle containing digestive enzymes, which is a temporary vacuole formed by the golgi body. Isolate and contain potentially harmful digestive enzymes and release them to recycle worn out organelles. They can also digest material brought into the cell.

Centriole

Cell organelle that aids in cell division in animal cells only.

Vacuole

A sac inside a plant cell that acts as a storage area.

Tonoplast

Membrane surrounding the vacuole.

Cell wall

A rigid layer mainly made of cellulose.

Pectin

A polysaccharide matrix where cellulose fibres are embedded.

Pits

Pores that allow movement through cell wall.

Plasmodesmata

Channels that connect cells to each other, formed out of strands of cytoplasma.

Symplast

The network of plasmodesmata that links plant cells.

Apoplast

The space outside the plasma membrane within which material can diffuse freely.

Chloroplast

An organelle found in plant and algae cells where photosynthesis occurs.

Thylakoids

Flattened membrane sacs inside the chloroplast, used to convert light energy to chemical energy.

Intergranal lamellae

A pair of membranes that contain chlorophyll. In the chloroplasts they link the thylakoids of one granum with the thylakoids of another granum.

Stroma

In plants, the solution that surrounds the thylakoids in a chloroplast.

Unicellular

Made of a single cell.

Peptidoglycan

A protein-carbohydrate compound that makes the cell walls of bacteria rigid.

Capsule

A sticky layer that surrounds the cell walls of some bacteria, protecting the cell surface and sometimes helping to glue the cell to surfaces.

Mesosomes

Folds of plasma membrane which can perform aerobic respiration.

Photosynthetic lamellae

Can be used in prokaryotic cells to perform photosynthesis or carry out nitrogen fixation.

DNA molecule

Loose in cytoplasm of prokaryotic cell.

Plasmids

Circular DNA molecules that can replicate independently of the main chromosomes of bacteria.

Pili

String-like, and help bacteria attach to surfaces and other cells (usually during sexual reproduction).

Virus

A tiny, nonliving particle that invades and then reproduces inside a living cell.

Acellular

Not made up of or containing cells.

Virion

A virus outside of a cell.

Bacteriaphage

A virus that infects bacteria.

Host cell

The cell that the virus infects.

Nucleic acid

The core of viruses, DNA or RNA.

Capsid

Outer protein coat of a virus.

Endosymbiotic

The theory that membranes absorbed mitochondria and chloroplasts millions of years ago.

Epithelial

Type of tissue that is a continuous layer, covering internal and external surfaces of the body. No blood vessels but may have nerve endings. Usually protective, secretory or absorption tissues.

Cuboidal

The simplest form of epithelium tissue, in a cube shape and one cell thick, for example in the kidney.

Columnar

Type of epithelium tissue with elongated cells; taller than they are wide, for example in the small intestine.

Basement membrane

Epithelial tissue sits on this; made of collagen and protein.

Squamous

Type of epithelium tissue, forms walls in alveoli. Flattened, very thin cells.

Stratified

Type of epithelial tissue that is made from multiple layers, with the top layers dead to avoid damage to the ones below, for example skin.

Ciliated

Type of epithelial tissue that is found in parts of the body where substances or particles need to be moved, for example fallopian tubes.

Cilia

The hairlike projections on the outside of cells that move in a wavelike manner, on ciliated epithelium.

Microvilli

Increases surface area, on columnar epithelium.

Muscle

Type of tissue that consists of highly specialised contractile cells of fibres held together by connective tissue.

Skeletal

Type of muscle tissue that is attached to the skeleton and contraction generates locomotion, powerful but tires easily. Is striated and voluntary.

Smooth

Type of muscle tissue that is spindle-shaped cells arranged in sheets or bundles. Cells are shorter and thinner, and don't fatigue easily. It is controlled by nerve from the autonomic system, for example in the digestive system. Is unstriated, and involuntary.

Cardiac

Type of muscle tissue found only in the heart, that contracts rhythmically. It is involuntary and straited.

Connective tissue

A tissue that provides support for the body and connects organ and tissues

Loose connective

A connective tissue that is found between layers of tissues.

Adipose

Stores fat as source of energy, protection, thermal insulation and buoyancy.

Cartilage

Found at the ends of bones and reduces friction during movement, some is flexible.

Differentiation

Process in which cells become specialised in structure and function.

Organ

A collection of tissues that carry out a specialised function of the body.

Involuntary

A muscle that is not under conscious control.

Unstriated

Muscle without striped fibres, such as smooth muscle.

Organ system

A group of organs that work together to perform a specific function.

Organism

A living thing.

Flagellum

A long, hairlike structure that grows out of a cell and enables the cell to move

Fibrous

Type of connective tissue that is found in tendons and join muscle to bone.

Chloroplast envelopes

Double membrane that surrounds the chloroplast.