Animal and Plant Cells
Animal and Plant cells both contain a nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.
But plant cells also contain a cell wall, chloroplasts and a permanent vacuole.
The nucleus controls the cells activities. The cytoplasm is where chemical activities take place. The cell membrane controls what goes into and out of the cell. The mitochondria is the energy released during respiration. The ribosomes are where protein are made (synthesised).
The cell wall is for support. The chloroplasts contain chlorophyll for photosynthesis. The permanent vacuole contain cell sap.
NOT ALL PLANTS HAVE CHLOROPLASTS!
Development in organisms, so some cells become specialised to carry out particular jobs. Its called 'differentiation'.
There are many different specialed cells:
In plants some cells may become xylem or root hair cells.
in animals some cells will develop into nerve or sperm cells.
Differentiation happes much earlier in the development of animals than it does in plants.
How do substance get in and out of cells?
Molecules move randomly.
Diffusion is the random movement of molecules from an area of high concentration to an area of low concentration.
No energy required from the cell.
The larger the difference in concentration, the faster the diffusion.
- the diffusion of oxygen into cells of the body from the blood stream as the cells are respiring
- the diffusion of carbon dioxide on actively photosynthesising plant cells
- the diffusion of simple sugars and amino acids from the gut through the cell membranes.
Osmosis is the movement of WATER!
It requires no energy from the cell.
Osmosis is a special case of diffusion inclolcing a partially permeable membrane.
Moves from a dilute solution to a more concentrated solution. No solute molecules can move across the membrane.
Partially permeable means that the membrane only lets smaller molecule through and not anything else.
Cells need water to support them, and chemical reaction take place in solutions.