• Cyanobacteria: 2.4 bya
• Eukaryote Photosynthesis: 1.4 bya

1st fossil evidence for photosynthesis in red algae.

Photosynthesis

Is glucose anabolic - creates carbohydrates.

Metabolism

Catabolic (breakdown bonds) & anabolic (building bonds)

Cellular Respiration

Catabolic

Uses sugar to make ATP.

Spontaneous electron transport pulled by O2.

Photosynthesis

Anabolic

Uses light to make sugar.

Light driven electron transport.

Proton Gradient

Creates potential energy.

Electron transfers drive H+s (hydrogen ions) across the inner membrane.

Oxidative Phosphorylation

Makes ATP

ATP Synthase Enzyme

Chloroplasts

Chloroplast

Has two membranes.

Thylakoid Membranes

Contains thylakoid lumen.

When stacked: granum

Stroma

Fluid around thylakoid lumen.

Light Dependent Reactions

Occur in the thylakoid membrane.

Makes ATP and NADPH and O2 from ADP and NADPH

Light Independent Reactions Calvin Cycle Depends on Light Dependent Reactions

Occur in stroma

Uses ATP and NADPH and CO2 to make sugar.

ATP

High-energy

3 negative phosphates

NADPH

Electron carrier

Light Dependent Reactions

Electron Transport Chain Creates photon gradient (potential energy).

Excited molecules must return to their ground state.

Light energy can be most as

• Heat
• Fluorescence (light)
• Transfers to another molecule (chlorophyll)

Forster Resonance Energy Transfer

How photons excite electrons.

Antenna Complex

Light harvesting

PQ A lipid

Accepts electrons

Reaction Center

Accepts and donates and electron to and from chlorophyll.

Water donates an electron to chlorophyll and gives off oxygen.

Redox Reactions

Stands for REDuction/OXygen.

Gains electrons or loses electrons.

Reduction

GAIN electrons +e

Oxidation

LOSE electrons -e

PhotoSystem II

Makes ATP. Photons can be scattered, reflected, transmitted, or absorbed.

Chlorophyll

Reflects green light

Absorbs photons.

Photons excite electrons, increasing energy,

• Electron is less stable, more reactive.
• Some electrons escape to the electron transport chain.

PhotoSystem I

Makes NADPH. Goes through electron transport chain again, second photon is used to re-excite the electron.

Study Guide

• When did photosynthesis first evolve and in what type of cells?
• When did photosynthesis arise in eukaryotes? a. the first fossil evidence of this is from what group of organisms?
• Which major groups of animals photosynthesize, which do not? a. which organisms have photosynthesizing symbionts? b. which organisms 'steal' chloroplasts from prey algae?
• What is the overall reaction for photosynthesis?
• How does this compare to cellular respiration?
• Fill out the chart comparing photosynthesis and respiration (last slide!).
• Compare photophosphorylation and oxidative phosphorylation a. where do they happen, what drives each one.
• How is photosynthesis split into two sets of reactions?
  a. What are they called?
  b. Where does each take place?
• Describe the structure of the chloroplast and the compartments within. What was the origin of the chloroplast again? a. Where do light-dependent reactions take place? b. Where do light-independent reactions take place? c. Why do both stop in darkness
• What is light?
  a. Describe its properties.
  b. How is the wavelength related to light energy? c. How is light energy related to the visible spectrum colors?
• What kinds of molecules absorb light?
• What happens when a photon of light is absorbed in terms of electrons?
• Understand all the forms of chlorophyll in the reaction centers
• Where is Chlorophyll, within the cell?
  a. How is it anchored in place? b. What molecule regenerates chlorophyll?
• How many photosystems are there in plants?
• What wavelengths of light are useful in photosynthesis? a. what wavelengths are absorbed by plant pigments b. what wavelengths are not c. how is this related to the visible color of photosynthetic organisms?
• Understand the following terms and what role they play in the light reactions of photosynthesis: a. Chlorophyll b. Photosystem II (P680) and Photosystem I (P700) c. Plastoquinone/Cytochrome/ d. NADP+/NADPH e. ATP synthase
• Describe the Z-scheme of photosynthesis: is the light dependent/independent? a. What is the sequence of events?
  b. What are the final products?
  c. What is the role of H2O?
  d. What role do H+ protons play? e. How does pH change in different compartments? f. How is ATP synthesized? (there are TWO places)
• What happens during the light-independent reactions?
  a. Describe the Calvin Cycle (C3).
  b. How do the light-independent reactions relate to the light reactions?
• What is Rubisco?
  a. What does it do in the cell? b. Where does it do its job? c. What factors affect Rubisco activity?
• What are the two main classes of biochemical pathways in Metabolism.
• How are glycolysis and photosynthesis related?
  a. What are the energy carriers for each?
• How are the metabolic processes in the plant cell inter-related?