CELLS CAPTURE AND RELEASE ENERGY ALL CELLS NEED

CELLS CAPTURE AND RELEASE ENERGY • ALL CELLS NEED ENERGY • SOME CELLS CAPTURE LIGHT ENERGY • ALL CELLS RELEASE ENERGY

ALL CELLS NEED ENERGY • Cells need a constant supply of energy (Plants from sun; Animals from food) • Chemical Energy: energy stored in bonds between atoms. • Glucose: main source of energy for most cells. • Cells use energy to carry out all of their activities.

SOME CELLS CAPTURE LIGHT ENERGY • Plants change Solar Energy into usable Chemical Energy (in glucose) by photosynthesis. • This takes place in CHLORPLASTS that have green chlorophyll (a light absorbing pigment that traps sun’s energy) • Plant takes in CO 2 and Water (H 2 O) • Energy from sun used to rearrange into GLUCOSE (sugar) and OXYGEN (released into air). • Plants can store glucose as large starch molecules (as in potato & carrot) to be used later or eaten by animals.

CELLS RELEASE ENERGY • Cellular Respiration = cells using O 2 to release energy stored in sugar (glucose); occurs mostly in the mitochondria • Glucose gets broken down (with O 2) into CO 2 and WATER; the exact opposite of photosynthesis • C 6 H 12 O 6 + 6 O 2 --- 6 H 2 O + 6 CO 2 + energy

Cells Release Energy Con’t. • FERMENTATION= cells release energy without oxygen (O 2); occurs entirely in the cytoplasm (not mito. ) • Alcoholic ferm. = Glucose alcohol + CO 2 + little energy; occurs in bread rising • Lactic acid ferm. = Glucose lactic acid + little energy; occurs in yogurt & cheese making

ENERGY AND EXERCISE • Muscle cells release ENERGY via cellular respiration & lactic acid fermentation • Normally muscles use OXYGEN (aerobic respiration) and release lots of ENERGY • In strenuous exercise, no time for oxygen, less energy released (tire out) and LACTIC ACID forms to irritate & “burn” muscle. • When you take a break, lactic acid gets broken down into CO 2 + H 2 O and burning sensation goes away.