Biology Revision – cells and osmosis

Cells

Cell membrane – controls movement in and out. Thin membrane, holds the cell together.
Nucleus – controls processes in cell. Contains chromosomes
Cytoplasm – produces energy, makes things, stores food
Cell wall – made of cellulose, a rubbery material makes cell strong
Sap vacuole – has watery fluid (sap), pushed cytoplasm sideways
Chloroplast – contains chlorophyll which is used for photosynthesis
Mitochondrion – releases energy for the cell
Glycogen – stored animal food, mostly glycogen
Starch – plants food storage, equivalent to glycogen  

Turgid –when a plant cell is full of water (firm)
Flaccid –limp (no water)

The characteristics of living things
Movement
Respiration
Sensitivity
Growth
Reproduction
Excretion
Nutrition

Osmosis                                                                                                      
Diffusion – this is the movement of molecules or atoms from an area of their high concentration to their low concentration.
Osmosis – this is a special kind of diffusion involving only water. Water moves from an area of its high concentration (weak solution) to its low concentration (strong solution) across a selectively permeable membrane

 
Two ways of investigating osmosis -1) using selectively permeable visking tubing, or
2) Using dyed agar jelly cubes.

Diffusion is fastest when there is a larger surface area.

A potato left in strong sugar solution will go flaccid as the water inside it will go by osmosis into the lower concentration of water in the sugar solution. A potato left in water will go turgid as the water will go by osmosis into the potato, as there is a lower concentration of water there.

Examples: