B2 Science Revision

Nucleus: Contains genetic material, which controls activities of the cell

Cytoplasm: Most chemical processes take place here , controlled by enzymes

Cell Membrane:Controls the movemont of substances into and out ofa cell

Mitochondria:Most energy is released by repiration here

Ribosomes:Protein synthesis happens here

Cell wall:Strengthens the cell

Chloroplasts:Contains chlorphyll, which absorbs light energy for photosynthesis

Permanent Vacuole:Filled with cell sap to help keep the cell turgid

Leaf Cell

Job/Adaption: Absorb light for photosynthesis - Contains lots of chloroplasts

Root Hair Cell

Job/Adaption: Absorbs water and mineral ions - Finger-like shape for a large surface area

Sperm Cell

Job/Apdation: Fertilises an egg - Head contains an enzyme to penetrate egg

Red Blood Cell

Job/Adaption: Carries oxygen to cells - Thin outer membrane so oxygen diffuses easily

Substances have to pass through the cell membrane to get into or out of the cell. Diffusion is a process that allows this to happen.

Diffusion: Particles diffuse from an area of high concentration to an area of low concentration

Diffusion happens in our:

Stomach: Digested food particles diffuse from the stomach cavity to blood in the villus.

Lungs:Oxygen moves from the alveoli into capillaries around the lung.

Plants also usually contain differentiated cells, tissues and organs.
Leaf- Carries out photosynthesis

Stem: Supports leaves and flowers           

Roots: Take minerals and water from the soil                                                               

Epidermal Tissue: Covers plant

Xylem: Transports water and minerals                                                                         

Mesophyll Tissue: Carries out photosynthesis

Phloem: Transports dissolved food

Leaves are adapted to absorb sunlight for photosynthesis.Photosynthesis: Carbon dioxide + Water ~~~~~~> Glucose + Oxygen

Light Intensity, Carbon Dioxide Concentration, Temperature are the three factors that can limit the speed of photosynthesis.

Light: Without light, a plant cannot photosynthesis quickly, even if there is plenty water and carbon dioxide. Increasing the light intensity boosts the spped of photosynthesis. EX: Artificial light extends time for photsynthesis so that photosynthesis can continue beyond daylight hours.

Temperature: If it gets too cold or hot, the rate of photosynthesis will decrease. EX: Heating can increase the rate of photsythesis, a good source is paraffin lamps which provide light, heat and carbon dioxide.

Carbon Dioxide: Photosynthesis is sometimes limited by the concentration of carbon dioxide in the air. Even if their is plenty of light, a plant cannot photsynthesis if there is insufficient carbon dioxide. EX: Adding carbon dioxide increases the rate.

Glucose is produced during photosynthesis and is used by the plants to make Cellulose and Proteins.

Cellulose: Which strengthens the cell wallProteins: Such as enzymes and chlorophyll.

Glucose is stored by plants and starch, fats and oils.

Enzymes: Biological catalysts that speed up reactions. Enzymes are protein molecules and are made up of amino acids. The enzyme is the lock and the reactant is the key.

A Catalyst is a substance which changes the rate of a chemical reaction without being changed itself. An Active Site is where substrates bind to an enzyme and undergo a chemical reaction. Activation Energy is the minimum amount of energy particles must hace to be able to react.

Most enzymes in the human body work best at about 37c.Over 40c most enzymes will stop working. The amino acids they are made from start to unravel and the shape of the active site changes. We say that the enzyme is denatured.