Diffusion is the movement of particles from an area of lower concentration to an area of higher concentration.
This is described as down a concentration gradient.
It is a passive process (does not require energy)
Factors Affecting Diffusion
1. Concentration gradient (the difference in concentrations)
2. Surface Area:Volume Ratio
3. Adjust temperature
Factors which Speed Up Diffusion:
Steep concentration gradient
Large surface area:volume ratio
Osmosis: The Movement of Water
Osmosis is the diffusion of water molecules across a partially-permable membrane from a higher concentration to one with a lower water potential.
When we talk about the number of water molecules free to move we say 'water potential'
The higher the water potential=the more molecules that can move
Water particules are not free to move if they are interracting with a solute dissolbed in the soloution
The more solute molecules you have dissolved, the fewer free water molecules and the lower the water potential
Effects of Osmosis on Plant Cells
Turgid = Cell has absorbed water and swelled. The cytoplasm is under pressure and is pushing against the cell wall
Flaccid = Cell has lost water and isn't swollen. The plant may droop
Plasmolysed = Cell has lost water and the cytoplasm has shrunk. The membrane is pulled away from the cell.
Normal = water uptake = water loss
It's important for plant cells to be turgid as it gives support to the non-woody plants and holds the stem upright. They are also important for opening and closing the stomata.
Lipids - Fats and Oils
Made of hydrogen, carbon and oxygen
Made of 1 fatty glycerol molecule and 3 fatty acids
Made of carbon, oxygen and hydrogen
Clucose molecules join together to form chains
They can form starch (plants), glycogen (fungi) and cellulose
Proteins - Amino Acid
Made of hydrogen, carbon, oxygen, nitrogen and sometimes sulpher
Made of subunits called amino acids, which join together to form chains (proteins)
There are 20 different types of Amino Acid
Starch - iodine soloution (orange-black)
Glucose - Benedict soloution (blue-red)
Protein - Buiret soloution (blue-purple)
Enzymes are proteins. They are biological catalysts, meaning they speed up the rate of reaction without being used themselves. They cause reactions to take place in cells (metabolic reactions)
Enzymes break down things and put them back together
They have an active site (where the reactions take place)
They also have an optimum pH
They can be denatured by extremes of temperatures of pH