PHOTOSYNTHESIS CELLULAR RESPIRATION Obtaining Energy Organisms are classified

PHOTOSYNTHESIS & CELLULAR RESPIRATION

Obtaining Energy • Organisms are classified according to how they get energy • Autotrophs – use energy from sunlight to make food • Heterotrophs – must get energy from food instead of directly from sunlight

Photosynthesis 6 CO 2 + 6 H 2 O → C 6 H 12 O 6 + 6 O 2 • Plants need: • sunlight • Water • Carbon dioxide • Plants make: • Glucose/sugar • oxygen

Photosynthesis Reactants vs. Products • Carbon Dioxide • Water • Sunlight • Glucose • Oxygen

Carbon Dioxide • reaches cholorplasts in the mesophyll cells by diffusing through the stomata into the leaf interior • Use of fossil fuels, deforestation, and other human activities have added excess carbon dioxide to the atmosphere • May enhance photosynthesis. • Plants may counter-balance by developing fewer stomata

• Less than 1% of all the water absorbed by plants is used in photosynthesis. • Most of the remainder is transpired or incorporated into plant materials. • If water is in short supply, stomata usually close and thus reduce the supply of carbon dioxide available for photosynthesis. Water

Light • About 40% of the radiant energy received on earth is in the form of visible light. • Leaves commonly absorb about 80% of the visible light reaching them. • Light intensity varies with time of day, season, altitude, latitude, and atmospheric composition. • Considerable variation in the light intensities necessary for optimal photosynthetic rates.

Location of photosynthesis • In a plant • In a leaf • In the mesophyll • In the chloroplasts • Thylakoids/Grana Stacks

Why are so many photosynthetic parts green? Sunlight on a Leaf Why leaves are green. Chromatography

Factors that affect photosynthesis • Light intensity • Light ↑ = photosynthesis ↑ • Temperature • Temp ↑ = photosynthesis ↑ • Carbon dioxide level • CO 2 ↑ = photosynthesis ↑ but then →

Cellular Respiration • THIS IS NOT BREATHING!!! • Cells make ATP (energy) by breaking down organic compounds (food) • BOTH autotrophs & heterotrophs can do • ATP is used to power all cellular activities

Cellular Respiration • C 6 H 12 O 6 + 6 O 2 → 6 CO 2 + 6 H 2 O + ATP • Exact opposite of photosynthesis • Heterotrophs need: • Heterotrophs make: • Food • Carbon dioxide • Oxygen • Water • Energy