Chapter 6: Energy for Life

Photosynthesis

transforms solar energy into chemical energy of carbohydrates.

Producers

Feed themselves and all the consumers.

Carbon dioxide enters leaves through what?

Stroma

Roots absorb

water

CO2 + H20 diffuse into…

mesophyll cells and then into chloroplasts.

Chloroplasts

• double membrane surrounds stroma

  • third membrane forms thylakoids

Grana

stacks

Begins with end products of cellular respiration, hydrogen atoms removed from water are added to carbon dioxide, oxygen is a by product of oxidation of water, and end product is CH2O or glucose (C6H12O6).

• Solar energy is required.

Photosynthetic Process

Light Reaction

Thylakoid membrane

Chlorophyll absorbs solar energy + energizes electrons

Water is oxidized, releasing electrons, hydrogen ions + oxygen.

NADP+ —> NADPH

Calvin Cycle

Occur in Stroma

CO2 taken up

ATP + NADPH used to reduce CO2 to a carbohydrate

Photosynthetic Pigments

Chlorophylls + Carotenoids

Chlorophylls

absorb violet, blue + red wavelengths better than other colors.

Because green is reflected, leaves appear green.

Carotenoids

Accessory Pigments

appear yellow or orange.

absorb violet, blue and green.

Photosystem I

absorption of solar energy.

energizes electrons

Electrons captured by another electron acceptor molecule.

NADP+ to NADPH

Photosystem II

Absorption of solar energizes electrons.

Electrons escape to electron acceptor molecule.

Will be used to make ATP

Calvin Cycle Reactions

making sugars.

powered by ATP + NADPH generated by light reactions.

Occurs in stroma of chloroplasts.

End product is glucose (C6H12O6)

Fixation of Carbon Dioxide

CO2 from atmosphere attached to RuBP by RuBP carboxylase (rubisco)

6 carbon molecules split into two 3 carbon molecules.

Reduction of Carbon Dioxide

uses NADPH (for electrons) and some ATP (for energy) from light reactions.

Forms G3P, which can become glucose.

G3P

Plants can make any molecules through this.

Form amino acids, fatty acids, and glycerol

Form glucose for energy needs

Form sucrose for transport through plant

Form starch for storage

Form cellulose for cell walls.