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.

Endosymbiosis is where a cell engulfs another cell and it continues to live inside the cell.

The engulfed cell provides something for the host cell, and gets something in return. Both cells benefit.

Under the microscope there is little change during interphase.
However interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm. (It is subdivided into G1, S, G2 phases of the cell cycle)
DNA replication occurs during the S-phase.

This protein is found in the human liver, where the hormone adrenaline indirectly stimulates it to mobilise stored energy inside liver cells in the "fight or flight" response.

The fact that it is a transmembrane protein is essential for this function.

It is interesting to note that this protein is also secreted by Anthrax bacteria as a toxin.
It upsets the metabolism of host cells when it enters them.

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.

According to cell theory, living organisms are composed of cells.
Cells come from pre-existing cells and cells are the smallest using of life.

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.

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.

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

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

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

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).

Channel proteins are used for facilitated diffusion down the concentration gradient.

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.

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

Stem cells can divide and differentiate along different pathways. For a single fertilised egg cell to grow into an embryo both these processes are necessary.

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.

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.

Cytokinesis occurs after mitosis in plant and animal cells.
Animal cells form a cleavage furrow (looks like a wasps waist) as they don't have cell walls.

The two daughter cells are the same size, so cytokinesis is equal.