Photosynthesis and Respiration

Photosynthesis

• Cells need a source of energy to function like a lightbulb needs electricity and a car needs gasoline.
• All organisms obtain energy from food.
• Consumers eat other organisms for food.
• Producers, such as plants, get light energy from the sun to make their own food.
• Photosynthesis converts light energy into food.
• Photosynthesis happens in plant cells and leaves.
• Carbon dioxide enters cells through tiny holes in the leaf.
• Water absorbed by the plant's roots travels to the leaf cells.
• Light energy, carbon dioxide, and water react in chloroplasts.
• The photosynthesis reaction produces glucose (sugar) and oxygen.
• Glucose travels to the rest of the plant to be used or stored.
• Oxygen exits the leaf through tiny holes.

Respiration

• Organisms get energy from food, but it needs to be converted into a usable form.
• Respiration converts energy from food into a usable form.
• Respiration happens in two stages.
• First, glucose from food enters the cell and is broken down into smaller molecules.
• This process releases a small amount of energy.
• The smaller molecules react with oxygen inside the cell's mitochondria
• This reaction produce carbon dioxide, water, and a large amount of energy.
• The cell then has energy to carry out its functions.

Fermentation

• Cells mainly use respiration for energy because it is plentiful.
• Respiration however, requires oxygen.
• If oxygen is unavailable, cells use fermentation.
• Fermentation is an alternate form of converting energy.
• Fermentation releases a small amount of energy and does not need oxygen.
• Muscle cells normally use respiration for energy.
• During exercise, muscle cells use energy faster than oxygen can be delivered.
• Muscle cells then switch to fermentation to still have a small amount of energy.
• Fermentation lets muscle cells keep working until oxygen supply is restored.