Biology Unit2 part 1 AQA

Life and Cells

Plants and animal cells all have

• a Nucleus (genetic material)
• Cytoplasm (chemical reactions)
• Cell Membrane (what goes in and out)
• Mitochondria (Respiration)
• Ribosomes (proteins)

Plant Cells have these plus

• Cell wall made of cellulose (support)
• Permanent Vacuole (cell sap)
• Chloroplasts (Photosynthesis)

Cells---->tissue----->organ---->organism

Specialised Cells

Palisade cells are adapted for PS

• full of chloroplasts
• tall so lots of surface area
• thin so can fit a lot in
• grouped together to make palisade layer

Guard Cells are adapted to open and close stomata

• Special kidney shape opens and closes
• Lots of water fills up cells and makes them go turgid which makes stomata open so PS can take place
• When short of water guard cells become flaccid making stomata close . less water vapour escapes
• Sensitive to light so only open when PS can take place

Red blood cells are adapted to carry oxygen

• Concave shape for large surface area to absorb O2. also helps it move smoothly
• Packed with haemoglobin (absorb O2)

Sperm and egg cells specialised for Reproduction

• egg cell has huge food reserves to feed embryo
• egg's membrane instantly changes its structure when 1 sperm cell fuses with the egg
• Sperm cell has has a long tail and a streamlined head to help it swim to the egg
• sperm cell also has large amount of mitochondria to give it energy to swim.
• Also carries enzymes to digest through egg's membrane

 Diffusion

Diffusion is the passive movement of particles from an area of high concentration to an area of low concentration.

Happens in gases and liquids as these are free to move unlike solids.

The bigger the difference in concentration the faster the rate of diffusion.

Osmosis

Same as diffusion except goes through partially permeable membrane and is the movement of water molecules from high concentrations of water to low concentrations.

Photosynthesis(PS)

Carbon dioxide + Water ----> glucose + oxygen

• Uses sunlight to produce glucose
• Happens in the chloroplasts filled with chlorophyll 
• Leaves in green plants 

Four things needed

• Light (sun)
• chlorophyll 
• Carbon dioxide (air)
• Water (roots via osmosis)

Rate of Photosynthesis

Limiting factors are

• light
• CO2 
• temperature (usually too low or high for enzymes if a limiting factor)
• water

This slows down PS…