Biology Unit 2

Features of an Animal Cell:

• Nucleus = controls the cells activities
• Cytoplasm = where chemical reactions take place
• Cell Membrane = controls the movement of materials in and out of the cell
• Mitochondria = where energy is released during aerobic respiration
• Ribosomes = where protein synthesis takes place

Features of Plant Cells

• Plant cells contain everything in an animal cell

They also have:

•  Cell wall = rigid and made of cellulose for support and structure
• Chloroplasts = contain chlorophyll for photosynthesis. They absorb light energy to make food
• Permanent Vacuole = containing cell sap

• Much smaller than animal and plant cells - can only be seen with very powerful microscopes
• Have a cell membrane and a cell wall which surround cytoplasm
• Do not have a nucleus
• Genetic material is in the cytoplasm
• When they multiply they form a colony

• A single-celled organism
• Have a nucleus, cytoplasm and a membrane surrounded by a cell wall

As an organism matures, each cell develops into a particular type. The structure of a cell is linked to it's function:

• Many mitochondria - needs a lot of energy e.g. muscle cell
• Many ribosomes - is making a lot of protein e.g. gland cells which produce enzymes
• Cells with tails - able to move e.g. sperm cells
• Receptor cells - have special structures which enable them to detect stimuli e.g. cone cells in eye are light sensitive
• Neurons - specialised to carry impulses from receptors to the CNS
• Plant cells - many chloroplasts to carry out photosynthesis
• Root hair cells - increase the surface area of the root to absorb water and mineral ions efficiently

• Molecules in gases and liquids - move around randomly (because of the energy they have)

Diffusion

• The spreading out of the particles of a gas, or of any substance in solution
• The net movement into or out of cells depends on the concentration of the particles on each side of the cell membrane
• Because the particles move randomly, there will be a net (overall) movement from an area of HIGH CONCENTRATION to an area of LOW CONCENTRATION
• Difference in concentration between two areas = CONCENTRATION GRADIENT
• Larger the difference in concentration = faster the rate of diffusion

Examples

• Diffusion of oxygen into the cells of the body from the bloodstream (as the cells respire)
• Diffusion of carbon dioxide into actively photosynthesising plant cells
• Diffusion of simple sugars and amino acids from the gut through cell membranes

A tissue = a group of cells with similar structure and function.

Animal tissues include:

• Muscle Tissue = can contract to bring about movement
• Glandular Tissue = to produce substances such as enzymes or hormones
• Epithelial Tissue = covers some parts of the body

Plant tissues include:

• Epidermal Tissue = covers the plant
• Mesophyll = can photosynthesise
• Xylem and Phloem = transport substances around the plant

Organs are made of tissues.

The stomach organ is made of:

• Muscular tissue = churn the stomach contents
• Glandular tissue = produce digestive juices
• Epithelial tissue = cover the inside an outside of the stomach

Leaf, Stem and Root are plant organs which contain epidermal tissue, mesophyll, xylem and phloem

• Groups of organs from organ systems to perform a particualr function e.g. difestive system

Food you eat - must be changed from insoluble molecules into soluble molecules.

Soluble molecules can be absorbed into the blood.

The Digestive System is responsible for this process:

Digestive System = a muscular tube which includes:

• Glands - such as the pancreas and salivary glands (which produce digestive juices)
• Stomach and small intestine - where digestion occurs
• Liver - produces bile
• Small intestine - absorption of of soluble food occurs
• Large intestine - water is absorbed from the undigested food (producing poo)