3-7Cells capture and release energy

What do these cells have in common?

All cells need energy

• Plants..sunlight• Animals..from food

• All cells use chemical energy.

• To stay alive, cells must be able to release the chemical energy in the bonds.

Chemical energy is the energy stored in the bonds between atoms of every molecule.

Glucose is the major energy source for most cells.

When you need energy, cells release chemical energy from glucose.

How energy is released.When you need energy, cells release chemical energy from glucose. You need food energy to run, walk and even sleep. Your cells use energy from food to carry out all of their activities.

Some cells capture light energy

• The source of energy for almost all organisms comes from the sunlight.

• Plants change the energyin sunlight into a form ofenergy their cells can use –the chemical energy in glucose.

All organisms benefit from the ability of plants to convert sunlight to food energy.

Photosynthesis

Plants must have chloroplast which contain chlorophyll, a light absorbing pigment that traps the energy of the sun.

Process of Photosynthesis

• I) The starting materials..

The plant takes in carbon dioxide from the air and water from the soil.

• II) The process..– Carbon dioxide and water

enter the plant’s chloroplast.

– Chlorophyll captures energy from sunlight, which is used to change carbon dioxide and water into new products.

• III) The products..

The plant releases most of the oxygen to the air as a waste product and keeps the glucose for its energy.

Plants do not immediately use all of the glucose they make. Some are linked together to make large carbohydrates called

starch.

All cells release energy

• Cells need energy to function.• Sugar must be broken down into individual

molecules before it can be used.• Chemical energy is stored in the bonds.• When a bond is broken, usable energy is

released. • Two basic processes..

Cellular Respiration

• Cells use oxygen to release energy stored in sugars.

• Most of the energy used by the cells in your body is provided by cellular respiration.

• Takes place in mitochondria.

The starting materials

The process

• Glucose is broken down into smaller molecules.

• This releases a small amount of energy.• These molecules move into the mitochondria.• Oxygen enters the cell and travels into

mitochondria.

The process continues

• As the molecules are broken down further, hydrogen is released in a way that allows cells to capture energy in a usable way.

• The hydrogen combines with oxygen to form water.

The products

The products

• Some of the energy released during cr is transferred to other molecules.

• It is carried to where it is needed in the cell.• The rest of the energy is released as heat.• Carbon dioxide formed during cr is released by

the cell.

Fermentation..the process by which cells release energy without oxygen.

CR the cell first breaks glucose into smaller molecules. This releases a small amount of energy.

No Oxygen

• Without oxygen, cr cannot continue.• In eukaryotic cells, instead of entering the

mitochondria , these smaller molecules stay in the cytoplasm, where fermentation occurs.

Two types of fermentation

• Alcoholic fermentation

• Lactic acid fermentation

Foods made from alcoholic and lactic acid fermentation

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Energy and exercise

• During hard or prolonged exercise, your muscle cells may use up all their stores of energy and oxygen.

• Then your muscles rely on fermentation to break down sugars.

• When your cells use fermentation to release energy, one of the waste produces is lactic acid, which causes a burning sensation in your muscles.

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