Chromosomes condense by supercoiling during mitosis. This makes the chromosomes visible.

The DNA replicates during interphase, not prophase.

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

Membrane proteins are diverse in terms of structure, position in the membrane and function.
Peripheral proteins are attached to the membrane but found on its surface.

Students are expected to be able to recognise and draw the simple structure of Prokaryote cells.

There is no compartmentation in prokaryote cells, and as membranes can be seen in structure B (a mitochondrion) it is not a prokaryote.

To explain how the structure of prokaryotes allows them to divide by binary fission you could mention:

• Prokaryotes have a single chromosome, eukaryotes have multiple chromosomes
• Prokaryotes have no nuclear membrane, which eukaryotes have.

The characteristics of living things (Mr H. Gren - metabolism, response, , homeostasis, growth, reproduction, excretion & nutrition)

The fly is responding to the closing trap, and the trap has responded to the presence of the fly.

Stem cells can divide and this help researchers to grow them in the lab.

They can differentiate along different pathways in embryonic development which makes stem cells useful for therapeutic uses (e.g. Stargart's disease) because they can be grown into many different tissues.

The lack of a membrane bound nucleus (nucleoid) classifies a cell as prokaryotic.

The ribosome is too small to be seen in the electron microscope, the other organelles were seen in the light microscope before the electron microscope was invented.

Extrinsic proteins are on the outside of the membrane, glycoproteins have carbohydrate prosthetic (side) groups (shown by the hexagonal shape).

Protein (5) has both hydrophilic and hydrophobic areas to act as an integral protein. The central channel is hydrophilic.

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 genetic code is universal (the codons code for the same amino acid in all organisms) but there are a very few exceptions, mostly in Archaea. A mutation does not alter the genetic code, it alters the base sequence of DNA.

Mitochondrial DNA is a single helical molecule, not associated with protein and circular in shape. The same as prokaryote nucleoid DNA.

In cell 2, the chromatids are aligned on the equator (seen from above)- Metaphase. In cell 1, the chromatids are moving towards the poles - Anaphase.

Similarity in structure and function are taken as evidence of a common ancestor. All of the other statements are partially true but do not provide an explanation.

Flagellae are locomotory structures found in some Monera (bacteria), and some eukaryotic cells such as male gametes and Protoctista. Mitochondria are not found in prokaryotes. Pseudopodia are involved in locomotion but only in cells without an external wall. Fimbriae in bacteria allow for binding to a host or substrate, the same name is given to projections in the oviduct that aid movement of the ovum towards the uterus.

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.