Biology Unit 2 Notes

Biology Unit 2 Notes

Biology unit 2 exam

Cells:

Animal and plant cells have:
Nucleus - controls the cells activities
Cytoplasm - where chemical reactions take place
Cell membrane - controls what goes in and out the cell
Mitochondria - where energy is released during respiration
Ribosome’s - where proteins are made

Plant cells also have:
Cell wall - for support
Chloroplasts - absorbs light energy to make food in the plant cells (also contains chlorophyll for photosynthesis)
Permanent vacuole - filled with cell sap (helps to support the cell)

Specialised cells:

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A tissue à a group of similar cells carrying out a particular function
An organ à a group of different tissues carrying out a particular function
A system à a group of different organs carrying out a particular function

How do substances get in and out the cell:

Molecules move randomly because of the energy they have DIFFUSION is the random movement of molecules from an area of high conc. To an area of low conc.

Diffusion:

Diffusion à spreading of particles of a gas or any substance in a solution resulting in net movement from a region of higher concentration

Oxygen required for respiration passes through cell membranes by diffusion
The greater the diff in conc. The faster the rate of diffusion
Increasing the temp. results in more movement in the particles ergo faster the rate of diffusion
Increasing the surface area of a membrane increases the rate of diffusion

**net movement = particles moving in - particles moving out**

Osmosis:

Osmosis is a special case of diffusion. Osmosis is the movement of water from an area of high water conc. (dilute solution) to an area of low water conc. (concentrated solution) through a partially permeable membrane.

Osmosis in animal cells:
If an animal cell is placed in a solution that has a higher solute concentration than the cytoplasm, then water will leave the cell by osmosis, until it shrinks and dies.
If an animal cell is placed in...