Revision:Respiration and Osmosis

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Respiration

Respiration is a process that takes place in all living cells. Respiration transfers energy from food molecules in animals and plants energy from respiration is used to make smaller molecules from larger ones, to let muscles contract and to keep a constant body temperature.

• Respiration:

    respiration is the oxidation of food substances by the organism.

Aerobic Respiration

Aerobic respiration is what happens when there is enough oxygen available. This is the ideal way to convert glucose into energy.

Glucose + Oxygen ---> Carbon Dioxide + Water + Energy

C₆H₁₂O₆ + 6O₂ ---> 6CO₂ + 6H₂O + Energy

The amount of oxygen used matches the amount of carbon dioxide produced.

Anaerobic Respiration

Anaerobic respiration in humans produces energy from glucose without needing oxygen. This means that when there is a shortage of oxygen, cells can carry on respiring for a short time.

Anaerobic respiration releases lactic acid as a waste. This is a mild poison and can cause cramp.

Anaerobic respiration is not the best way to convert glucose into energy.

Glucose Energy + Lactic Acid

When you do some exercise and your body cannot supply oxygen to your muscles then anaerobic respiration is used. Lactic Acid builds up in the muscles. After resorting to anaerobic respiration, when you stop you'll have oxygen debt.

Yeast

Yeast is used for making bread and brewing beer, and in both cases the yeast does this by performing anaerobic respiration. Another word for this process is fermentation.

Glucose ---> Alcohol + Carbon Dioxide (+ energy)

Yeast is a microscopic fungus that can produce carbon dioxide and alcohol from glucose by fermentation. Animals do not use fermentation as a way of releasing energy from glucose.

Photosynthesis and Respiration

Photosynthesis and respiration are opposite processes. The equations are the same but in opposite directions.

Photosynthesis

Carbon dioxide + water ---> glucose + oxygen

Respiration

Glucose + oxygen ---> carbon dioxide + water

Photosynthesis requires energy and respiration releases energy.

Osmosis

Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration. A partially permeable membrane is just one with small holes in it. So small in fact, that only water molecules can pass through them, bigger molecules like glucose, cannot.

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