Cell Structure

A eukaryotic cell (animal and plant cell) = cell membrane, cytoplasm and genetic material in a nucleus. Whereas a prokaryotic cell (bacterial cell) = a lot smaller, cytoplasm, cell membrane which is surrounded by a cell wall. The BIG difference between the two is that the eukaryotic has a nucleus and the prokaryotic DOES NOT! The genetic material in the prokaryotic is contained in rings of DNA called Plasmids.

Animal Cells contain:

• Nucleus (controls the cell
• Cytoplasm (where chemical reactions happens)
• Cell membrane (controls what moves in and out the cell)
• Mitochondria (where aerobic respiration happens)
• Ribosomes (for protein synthesis)

Plant cells contain the above as well as:

• Choloroplast (filled with cholorophyll used for photosynthesis)
• Permanent Vacuole filled with Cell sap (keeps the cell firm)
• Cell Wall (strengthens cells)

The muscle is a cell but lots of those cells can make a muscle tissue. The stomach is an organ which absorbs water from undigested food; it's a part of the digestive system. The liver is also an organ which is a part of the digestive system which breaks down large insoluble molecules into smaller soluble molecules.

Cells = Tissue = Organ = Organ System = Organism

Differentiation is the rocess where cells become specialised. In animal cells it occurs in the embryo and is permanent. Whereas in plant cells it can occur at anytime and is reversible.

Why do you need more cells?

• Growth
• Repair
• Replacement

Electron microscopes have a much higher magnification resolving power than light microscopes. This means that we can see more sub-cellular structures (ribosomes) and have a better understanding of their functions.

Image size divided by Object size = Magnification

Substances may move in and out of cells across the cell membrane via diffusion. Diffusion is the particles of any solution moving from a higher concentration to an area of lower concentration. It happens down a concentration gradient which is the difference of two areas of concentration. Cells can increase the surface area by having folded membranes which increases the rate of diffusion.

Features of an efficient exchange surface:

• Big surface area
• Thin Membrane
• Efficient blood supply
• Being well ventilated (animals)

It's the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.

It moves substances from a more dilute solution to a more concentrated solution against the concentration gradient which requires energy from respiration released by mitochondria. Active transport allows sugar molecules to be absorbed from lower concentrations in the gut into the blood. This is because blood has a higher sugar concentration. Suar molecules are used for cell respiration.