chapter 5 biology

autotrophs

“self feeders,” make energy-rich molecules (plants, some bacteria).

photosynthesis equation:

Energy (light) + 6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂

photosynthesis reaction type

Anabolic (builds molecules) & Endergonic (requires energy)

energy source for photosynthesis

Light energy (photons) from the sun.

light reaction location

thylakoid membranes.

Calvin Cycle

st

light reaction function

capture sunlight, make ATP & NADPH, release O₂

Calvin cycle function

use ATP & NADPH to build glucose

shorter wave length energy

more energy (blue/violet)

longer wavelength energy

less energy (red)

why plants are green?

Chlorophyll reflects green light & absorbs red/blue (green is rejected so that’s what we see)

photosystem structures

Pigment molecules (chlorophylls, carotenoids), reaction center, electron acceptors.

how photosystems trap light

Pigments absorb light → transfer energy to reaction center → excite electrons.

source of excited electrons

PSII → water splitting.
PSI → electrons from PSII.

oxygen generation:

Water is split (photolysis) → O₂ released as waste.

proton gradient

Electrons moving down ETC pump H⁺ into thylakoid lumen.

ATP from H⁺ Gradient

H⁺ flows back through ATP synthase → chemiosmosis makes ATP.

light reaction input

light, H₂O, NADP⁺, ADP + Pi

light reaction output

O₂, NADPH, ATP

light reaction connection to Calvin cycle

Products of light reactions (ATP & NADPH) = reactants for Calvin Cycle.

Calvin cycle input:

CO₂, ATP, NADPH

Calvin cycle output

G3P, ADP +Pi, NADP⁺

carbon fixation

CO₂ attached to RuBP (5C) → forms 3C molecules (G3P).

carbon fixation enzyme

Rubisco

why are 6 turns needed?

Each turn fixes 1 C → 6 CO₂ needed for 1 glucose (6C).

photosynthesis function

stores energy in glucose.

heterotrophs

“other feeders,” must eat other organisms (animals, fungi, humans).

respiration function

releases energy from glucose.