Pasteur's famous experiments with swan neck flasks showed that broth kept in a flask where no dust could settle in the nutrient medium, and thus no living cells could get in, would not go mouldy.

This disproved the theory of spontaeous generation.

The first cell must have come from non-living material. This material must have contained molecules which today we consider as organic, carbon containing molecules.

Skill: Identification of phases of mitosis in cells viewed with a microscope or in a micrograph
(prophase, metaphase, anaphase and telophase).

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.

If you look closely at X, it points to the cell wall, outside the plasma membrane, it is close to the plasma membrane, but not touching the chloroplast.

The pale area below Y is the vacuole.

Organelle Y is a mitochondrion, you can tell this by its size, and the presence of membranes inside.

There are ethical concerns about the use of embryo stem cells.

The research is expensive, and potential treatments are also likely to be expensive, and probably not available to all.

Many people who are against stem cells say that it is because cells are taken from human embryos, which have the potential for human live, and should be protected. There are other sources of stem cells, they argue.

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.

Comment: During differentiation genes may be activated or repressed causing the formation of different proteins by the ribosomes but other organelles such as mitochondria continue to function in the same way

Comment: SI units always have a differential of 1000. The unit without the prefix is the standard SI unit (metre, m). B and D are clearly wrong, eliminate those answers first.

It is unicellular (one cell) and a eukaryote (has a nucleus) and not autotrophic.

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

The organelle shown is the nucleus, it stores the genetic information, DNA and is the location of DNA replication and Transcription.

Protein channels cross the membrane to allow hydrophilic substances to pass through the membrane.

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

The saline drip must be isotonic to human blood to not cause water gain or loss from tissues.

Pasteur demonstrated that broth would go cloudy only when air was allowed to contact the broth, bringing microbes. He disproved Spontaneous Generation.

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.