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OCR 21st century science B4

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on 12 November 2013

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Transcript of OCR 21st century science B4

OCR 21st century science B4
All living things require energy for respiration and photosynthesis is what allows plants to produce energy.
The chemical reactions of living things.
How do plants make food?
Structure of a cell

A basic unit of life is the cell. a plant structure looks like so ...
Plants use different types of respiration to obtain different types of energy.
The Processes of life.
Learn all you need to know for your B4 exam.
Organisms all use energy for many activities which include movement and production of large molecules required for growth
Enzymes are a protein that speed up chemical reactions and this is how they work...
2.) Substrate molecule fits in active site of enzyme
3.) Reaction occurs and products made; the enzyme speeds up this reaction
4.)Product molecules do not fit in enzymes as well so are released. The enzyme can then be used again with a new substrate molecule
1.) Substrate molecules move towards active site in enzyme
Enzymes a type of protein ,which are made of amino acids, and form to make complex 3d structures and give enzymes there certain shape and capability.
An enzyme works as lock and key, the enzyme the lock and the substrate the key
Enzymes have an ideal temperature and ph.If the pH or temperature exceeds optimum the enzyme will denature
Plants,as mentioned earlier need to make food for energy.The way in which they do this is through photo synthesis and this is the production of glucose.
The chemical reaction for photosynthesis is
(light energy)
carbon dioxide + water ----------> Glucose +oxygen
The sunlight is absorbed through a chemical in the chloroplasts called cellulose and this is where the photosynthesis takes place.The glucose is then converted into starch for storage and is used in resperation to release energy.
Animal cells and microorganisms such as yeast all have the nucleus, cytoplasm and a cell membrane but there are other variants.

The cell membrane controls what enters and leaves cells. It allows gases and water to pass in and out but no other chemicals.

The cell wall is made from cellulose which has the chloroplast where photosynthesis takes place.

The cytoplasm is where most of the chemical reactions occur. Its also contains mitochondria which contains the enzymes needed for the release of energy by aerobic respiration.

The nucleus contains the DNA which stores the genetic code. This carries information to make other proteins .

Transport in plants.
There are three different types of transport in plants and these are diffusion , diffusion by osmosis and active transport.
Diffusion is the movement of chemicals from high concentration to low concentration. It happens because of random movement of molecules and the movement does not stop.

It happens in photosynthesis when water is taken up by plant roots
when carbon dioxide enters the plant it leaves by diffusion
and oxygen also leaves plants by diffusion.

Diffusion is passive which means that it happens without requiring energy.
Is a type of diffusion but it only happens with water. This is how , for example, the cell wall works by letting in water but not chemicals.

It is when chemicals are separated by a partially permeable membrane.

On the whole it is the movement of water from high to low concentration.

The movement of water into roots from the soil occurs by osmosis
Active transport
Active transport is different to diffusion and osmosis because it is when the chemical is taken in and used to make proteins

For example the plants roots take up nitrates and use the nitrogen to make proteins.

Active transport is used instead of diffusion usually because the nitrates would be to big to take up by diffusion.

It is not passive as it takes energy from respiration to transport the chemicals across membranes.
The chemical that plants produces from photosynthesis (glucose) they use for respiration.

Respiration using oxygen is called aerobic respiration and the word equation is :

glucose + oxygen ------> carbon dioxide + water (+ energy released.)

Aerobic respiration takes place in animal, plant cells and some microorganism.

Aerobic respration is required because of the energy requires to synthesis of large molecules and movement

The food produced from photosynthesis for respiration and active transport.

Respiration happens in stages of enzyme controlled reactions.

symbol equation:

This is the production of energy without the use of oxygen. This happens in human cells when the muscle is being put through a lot of work in a short period of time.

In a plant this happens when the roots are waterlogged and bacteria is in deep puncture wounds.

Aerobic respiration releases on average more energy per molecule of glucose then anaerobic energy.

The word equation is:

Glucose -----> lactic acid +ENERGY

Type of anaerobic respiration. used by some microorganisms.

ethanol is a result of fermentation of yeast and this is use full to human.

Some plants produce alcohol from fermentation and the word equation is :

glucose ----> ethanol + carbon dioxide + ENERGY

This process is mainly important for alcohol production and bread making.

It is also important in biogas production.
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