Cell Processes and Energy

Organisms Require Energy Two organelles are responsible for providing energy to living things: Chloroplasts Mitochondria

Chloroplasts Found mainly in plant cells. The site of photosynthesis

Photosynthesis The process by which a cell captures energy in sunlight and uses it to make food. Photo = light Synthesis= putting together Photosynthesis means using light to make food

Photosynthesis is a two stage process Stage One Capturing the sun’s energy Takes place in the Chloroplasts Pigments (chlorophyll and others) capture the light energy and use it to power the second stage (similar to solar cells powering a calculator)

Photosynthesis - Stage Two The second stage also takes place in the chloroplast Water (H2O) and Carbon Dioxide (CO2) undergo a series of chemical reactions. *Water enters a plant through its roots. *Carbon dioxide enters the plant through the stomata ( tiny openings in the leaves)

The Chemical Reaction The chemical reactions are powered by energy from the sun. The atoms in carbon dioxide and water are separated and joined to form oxygen and glucose (a simple sugar) light energy 6CO2 + 6H2O  C6H12O6 + 6O2 carbon dioxide + water yields glucose + oxygen raw materials products

Storing Energy During the process of photosynthesis the cell stores energy in glucose (sugar) *Some of the glucose is used as food *Some is converted into other molecules, such as cellulose. *Some is stored for later use

Mitochondria When the cell or organism needs energy, the mitochondria go to work. The process by which cells break down simple food molecules to release energy is called respiration

Respiration is also two stage process. Stage one occurs in the cytoplasm, where glucose molecules are broken down into simpler forms. A small amount of energy (ATP) is released

Respiration - Stage Two Stage two takes place in the mitochondria. Oxygen is required for this stage and a large amount of energy (ATP) is released.

Respiration Equation C6H12O6 + 6O2  6CO2 + 6H2O Glucose + Oxygen Yields Carbon + Water + Energy(ATP) Dioxide Notice the equation is opposite that of photosynthesis Together the two process keep the levels of CO2 and O2 fairly constant

Fermentation Some cells are able to obtain energy from food without using oxygen. This process is called fermentation. Less energy is released when oxygen is not used. There are two types of fermentation * Alcoholic Fermentation * Lactic Acid Fermentation