Cell

Top section - Epidermis

• The top is packed with chloroplasts for photosynthesis. More of them are crammed at the top of the cell - so they're nearer the light.
• Tall shape means a lot of surface area exposed down the side for adsording CO2 from the air in the leaf.
• Thin shape means that you can pack loads of them in at the top of the leaf 

Top section - Epidermis            Middle section - mesophyll            Bottom section - epidermis

Structure of the leaf

• Carbon dioxide diffuses into the air spaces within the leaf, then the CO2 diffuses into the cells.
• The stomata controlls the CO2 & O2 & the other gases and water entering and exiting the leaf. The size of stamatas are controled by the guard cells (guardinans of the floud gates).
• O2 diffuse out of the cell.

Guard Cells

• Kidney shape which opens and closes the stomata.
• When the plant is short of water, the guard cells lose water and become flaccid, making the stomata close.
• Thin outer walls and thickened inner walls make opening and closing work.
• They're also sensitive to light and close at night to save water without losing out on photosynthesis.

• Stage 1-Interphase: In a cell that's not dividing, the DNA is all spread out  in long strings.
• Stage 2-Prophase: If the cell gets a signal to divide, it needs to duplicate its DNA - only one copy for each new cell. DNA is copied and forms X-shaped chromosomes.
• Stage 3-Metaphase: The chromosomes then line up at the centre of the cell
• Stage 4-Anaphase: Then cell fibre pull them apart. The two arms of each chromome go to oppsite ends of the cells.
• Stage 5-Telophase: Membranes from around each of the sets of chromosomes. these become the nuciei of the two new cells.
• Stage 6-Cytokinesis: Then the cells divide. Know you have two new cells containing the same DNA

• Stage 1: Before the cell starts to divide, it duplicates its DNA - one arm of each chromosomes is an exaxt copy of the other arm.
• Stage 2 :In the first division in meiosis the chromosome paires line up in the centre of the cells.
• Stage 3: The pairs are then pulled apart, so each new cells only has one copy of each chromosomes. some of both parent's chromosomes go into each new cell.
• Stage 4: In the second divison the chromosomes line up again in the centre of the cell. it's a lot like mitosis. The arms of the chromosomes are pulled apart.
• Stage 5: You get four gametes each with only a single set of chromosomes in it.