Cells part 2

microscopes, et all

What does a light microcope use?

Light rays which reflect off a mirror

What does an electron microscope use?

Beams of electrons

Benefits and drawbacks of using an electron microscope

Benefits:

• Higher resolution + magnification

• view organelle which are not visible with a light microscope

Drawbacks:

• Very expensive

• Requires a dead specimen

Define diffusion

The net movement of particles from an area of high concentration to an area of low concentration

Factors affecting diffusion

• Concentration gradient

• Temperature

• Surface area

Define osmosis

The movement of water molecules from an area of high water concentration to an area of low water concentration through a partially permeable membrane.

Define active transport

The movement of molecules from an area of low concentration to an area of high concentration using energy (from respiration)

What do chromosomes do? How many pairs do we have?

carry genetic information

23 pairs

When do cells divide?

• When an organism grows

• When an organism becomes too damaged and needs to produce new cells

Explain what happens during mitosis

1. cell begins to divide

2. DNA is replicated

3. Membrane breaks down and chromosomes line up across the centre of the cell

4. One set of chromosomes are pulled to the polar ends of the cell and the nucleus divides

5. Cytoplasm and cell membranes divide to form 2 daughter cells