Quick Revision

Nucleus - contains DNA

Nucleolus - in nucleus, manufactures ribosomes

Endoplasmic reticulum - move materials from one part of the cell to another

Golgi apparatus - where proteins are converted to their final form

Lysosomes - contain digestive enzymes

Chloroplasts - contain pigments important to photosynthesis

Mitochondria - site of ATP production

Ribosomes - manufacture of proteins

Centrioles and microtubules - support, cell locomotion, forming spindle in nuclear division

Cell wall - support, prevents cell from bursting by taking in too much water

Osmosis: the net movement of water molecules through a partially permeable membrane from an area of higher water potential to an an area of lower water potential.

Facilitated diffusion: This is where polar molecules are transported across membranes. Molecules bind with transport proteins which change shape and move the molecules across the membrane. No metabolic energy is required.

Examples of active transport: the calcium pump (skeletal muscles), the sodium-potassium pump (nerve cells).

Endocytosis: An active process whereby substances are taken into the cell by infoldings of the surface membrane. (Exocytosis is similar.)

Mitosis: Mitosis is a type of cell division where the daughter cells have the same number of chromosomes as the parent cell and are genetically identical to the parent cell. Mitosis takes place in four stages: prophase, metaphase, anaphase and telophase.

During prophase, each chromosome forms two chromatids joined by a centromere. Two centrioles begin to move forming a spindle and the nuclear envelope breaks down.

During metaphase, the chromosomes are attached to the spindle fibres and line up at the equator of the cell.

During anaphase, the centromeres split and the chromatids are pulled to opposite poles of the cell.

During telophase, the nuclear envelope reforms and the cell membrane narrows at the middle, forming two daughter cells

 

Sucrose = glucose + fructose; main form in which carbohydrate is transported in plants

Maltose = 2 glucose; found in some germinating seeds eg barley
Lactose = glucose + galactose; found in milk

Lipids - insoluble in water, soluble in organic solvents

Fats & oils - compounds of glycerol and fatty acids

Structure of proteins
Primary - Order of the amino acids
Secondary - The way the chain folds/turns on itself due to hydrogen bonding
Tertiary - Cross-links including hydrogen bonds, inonic bonds and sulphur bridges
Quaternary - The arrangement of two or more polypeptides eg haemoglobin
Collagen - fibrous protein; great tensile strength; found in bones, tendons, skin etc; structure = triple helix
Insulin - globular protein, folded chain held together by 2 disulphide bridges with the loop removed