Unifying concept that states that cells are a fundamental unit of structure, function and organisation in all living organisms
In complex organisms, cells are organised into tissues,organs, and organ systems
Organelles in eukaryotic cells
Nucleus
Nucleolus
80S ribosomes
Rough and smooth endoplasmic reticulum
Mitochondria
Centrioles
Lysosomes
Golgi apparatus
Cell wall
Chloroplasts
Vacuole and tonoplast
Prokaryotic cells

Cells that do not have a nucleus, or any interior compartments
Eukaryotic cells

Cells that have a nucleus, and various other interior compartments, called organelles
Cell membrane (or plasma membrane)
Thin, flexible layer round the outside of all cells made of phospholipids and proteins
Separates the contents of the cell from the outside environment
Controls the entry and exit of materials
Nucleus

Largest organelle
Surrounded by a nuclear envelope
Contains nucleoplasm and chromatin
Mitochondria

Sausage-shaped organelle where aerobicrespiration takes place and ATP is synthesised. Contains a double-membrane with cristae
Chloroplast

Organelle where photosynthesis takes place, found in photosynthetic organisms (plants and algae)
Ribosomes

Sites of protein synthesis, found either free in the cytoplasm or attached to the rough endoplasmic reticulum
Endoplasmicreticulum (ER)

Series of membrane channels involved in synthesising and transporting materials
Rough ER is studded with ribosomes
Smooth ER does not have ribosomes and is used to process lipids
Golgi body (or Golgi apparatus)

Series of flattened membrane vesicles that transport proteins destined for extracellular use from the ER to the cell membrane for export
Vacuoles

Membrane-bound sacs containing water or dilute solutions of salts and other solutes
Plant cell vacuoles help to keep the cell rigid or turgid
Lysosomes

Small membrane-bound vesicles containing digestiveenzymes, used to break down unwanted materials
Cytoskeleton
Network of protein fibres extending throughout all eukaryotic cells, used for support, transport and motility
Centrioles

Two centrioles found near the nucleus, used in cell division to make the spindle fibres that move the chromosomes
Cell extensions
Cilia
Flagella
Microvilli
Cytoplasm (or cytosol)

Solution within the cell membrane, containing enzymes and other materials needed for the cell to function
Cell wall

Thick layer outside the cell membrane, made of different materials in different cell types
Magnification and resolution can be achieved using light and electron microscopy
Staining specimens is important in microscopy as it increasescontrast so intra-cellular structures are visible
Types of passive transport
Diffusion
Facilitated diffusion (through carrier proteins and protein channels)
Osmosis
Properties of molecules that affect transport
Solubility
Size
Charge
Water potential
Turgorpressure + osmoticpotential
Active transport

Requires energy from the hydrolysis of ATP
Endocytosis and exocytosis

Processes for transporting large molecules into and out of cells through the formation of vesicles
Flagella
Longer than the cell, usually only one or two, used for motility (e.g. sperm)
Microvilli

Short extensions found in certain cells such as in the epithelial cells of the intestine and kidney, where they increase the surface area for absorption of materials
Cytoplasm (or Cytosol)
The solution within the cell membrane, containing enzymes for glycolysis (part of respiration) and other metabolic reactions together with sugars, salts, amino acids, nucleotides and everything else needed for the cell to function
Cell Wall

A thick layer outside the cell membrane, made of different materials in different cell types
Materials cell walls are made of
Cellulose (plant)
Chitin (fungal)
Peptidoglycan (bacterial)
Cell walls

Used to give strength and rigidity to cells and to resist osmotic lysis
Made of a network of fibres that give strength but are freely permeable to solutes (unlike membranes)
Layers of plant cell walls
Middle lamella (outer layer, made of calcium pectate)
Secondary cell wall (inner layer, thick, network of cellulose, hemicellulose and pectin)
Plant cell walls are usually studded with channels called plasmodesmata, which link the cytoplasms of adjacent cells, forming a symplast (a continuous cytoplasm)
Tissue
A group of similar cells performing a particular function
Organ
A group of physically-linked different tissues working together as a functional unit
Organ system
A group of organs working together to carry out a specific complex function
Prokaryotic cells

Smaller than eukaryotic cells
Do not have a nucleus or membrane-bound organelles