The 64 codons in the genetic code give rise to the same amino acids in nearly all organisms, There is very little variaion. If the genetic code had evolved several times in the history off life, there would be many differences.

Cytokinesis occurs after mitosis in plant and animal cells. The chromosomes are uncoiled.

Plant cells build a new cell wall which divides the cytoplasm.
Animal cells form a cleavage furrow (likes a wasps waist) as they don't have cell walls.

Cell A is swollen turgid, it is in a hypotonic solution or an isotonic solution.

The cells B, C and D show increasing signs of plasmolysis, and so they must be in hypertonic solutions.

Skill: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions. (Practical 2)

When a sample of cells show no change in mass, then the net movement of water by osmosis must be zero. This shows the concentration of the cytoplasm of the cells. In this graph it would be about 0.3 mol

Know how to idenfity the organelles in eukaryotes and draw their compartmentalised structure.
The rER has parallel membranes covered in dots, which are ribosomes, used for making proteins, for secretion from the cell.

Eukaryote cells (approx. 100µm in diameter) are much larger than prokaryote cells (approx 1µm) and so the concentration of reactants in the cytoplasm would be more dilute if all the metabolism happened in the cytoplasm.

Specialist organelles, like mitochondria keep the enzymes for aerobic respiration in one place, which increases their concentration, and increases the rate of reactions.

Specialised tissues can develop by cell differentiation in multicellular organisms.

Differentiation involves the expression of some genes and not others in a cell.

Calculate specimen size using magnification?

First change the size measurement into µm units = 20000µm

Then divide by the magnification. 20000 / 3000 = 20 / 3 = 6.6 µm

Many transmembrane proteins are involved in transport of molecules across membranes. These can either provide a sort of molecular pore through which ions or molecules can pass (facilitated diffusion), or they can use ATP to actively move molecules, even against the concentration gradient (active transport).These are just two examples, transport can also occur by simple diffusion through the phospholipid bilayer, or by endocytosis.

Hypertonic solutions have a higher concentration of solutes, and lower water potentials than cells.

Comment: The multicellular condition allows for differentiation into cells of different types and also replacement of cells when injured or damaged.

A fungal hypha has many nuclei in a hypha but no cross walls to divide the hypha into cells.

The cells produced by mitosis differentiate into mature cells and replace the cells lost at the surface.

Channel proteins penetrate the membrane and have a central hydrophilic area (yellow in the diagram which is shown from above).

Ribosomes on the RER manufacture protein. This is packaged in vesicles by the Golgi Body and moves to the surface of the cell where the vesicle and plasma membrane fuse and exocytosis of the protein occurs.

The first cells must have arisen spontaneously from non-living matter, probably in volcanic vents, but the universal nature of cell ultrastructure and of the genetic code makes it likely that this only happened once.

The irregular sizes and insolubility of hydrophobic membrane proteins indicated that they could not be a surface layer as proposed by Davison-Danielli. This was confirmed by fluoresecent antibodies showing that proteins were both within and on the membrane.

The organelle is a cell component with a membane, the mitochondrion, it is adapted to aerobic respiration.

There are 3 complete cells in prophase (chromosomes visible in a nucleus..

There is no net water movement, gain and loss from the tissue is equal in both directions.