Cells Capture and Release Energy Section 2.2

Energy Energy is needed by organisms to stay alive – Plants get energy from the sun – Animals get energy from food

Energy Chemical energy is stored in the bonds of molecules – Cells need to break the bonds of molecules to release energy – Glucose is a major energy source of cells

Energy Photosynthesis – Plants take energy from the sun and change it to the chemical energy in glucose – The process takes place in cell with chloroplasts – Chlorophyll, a light absorbing pigment, traps the energy from sunlight

Energy Photosynthesis sunlight CO 2 + H 2 O C 6 H 12 O 6 + O 2 Chlorophyll Some glucose is changed to starch and stored for later use

Energy Energy is released from food when the chemical bonds are broken Cellular Respiration – Cells use oxygen to release stored energy in sugar – Takes place in the mitochondria – Takes place in animals and plants

Energy Cellular Respiration C 6 H 12 O 6 + O 2 H 2 O + CO 2 + Energy – Some energy is transferred to other molecules which carry energy to where it is needed – The rest of the energy is released as heat

Energy Fermentation – Cells release energy without oxygen – Cells break glucose down into smaller molecules and release small amounts of energy – Small molecules ferment in cytoplasm – Alcoholic fermentation (bread) or lactic acid fermentation (yogurt, cheese) can occur

Energy Exercise – Muscles store energy and oxygen – During long exercise, muscles use up energy – Fermentation occurs to provide energy and lactic acid builds up (burning) – You breathe hard to break down byproducts fermentation (burning goes away) – Reserves of energy an oxygen build up again

Energy