Module 6: Autotrophy & Photosynthesis

heterotroph hypothesis

idea that states that the first cell on Earth were anaerobic, heterotrophic prokaryotes

First Organisms

-Heterotrophic

-Anaerobic (no oxygen used)

-Ate carbon and released CO2

First PHOTOSYNTHETIC Organisms

-3.5 bya

-Cyanobacteria

-Autotrophic

-Used light energy and CO2 to make own food while O2 was released as byproduct

Ozone Layer

-Made of O3

-Made land habitable

Photosynthesis Equation

6CO2 + 6H2O --> C6H12O6 + 6O2

Light Reaction (Summary)

-Chlorophyll absorbs light in the thylakoid membrane

-Photolysis: H2O --> 2H+, 2e-, and 1/2 O2

-Light --> chem. energy (ATP and NADPH)

Carbon Reaction (Summary)

-3-carbon sugars created from chem. energy of light

-Combine to produce glucose

Bundle Sheath

-In C4 plants, not all

Stomata

-Under leaves

-Lets material in

-Guard cells open and shut around stoma

Open Stomata

-Sunlight

-High humidity/rain

-Low CO2

-K+ intake

Closed Stomata

-Darkness

-Low humidity

-High CO2

-K+ output

Photons

-Packets of light energy

Light

-Electric and magnetic vibrations

-Wavelength determines color and energy of light

• shorter= higher energy

Electromagnetic Spectrum

Pigment

-Molecule that release e- when energized by photons

Chlorophyll a

-Dark green; located in photosystem II

Chlorophyll b

-Light green; located in photosystem I

Carotenoids

-Accessory pigment

-In carrots (good way to remember)

Absorption Spectrum

-X-axis: amount of light absorbed

-Y-axis: wavelength

-Green is not absorbed, which is why plants are green

Chloroplast

A plastid containing chlorophyll, the site of photosynthesis

Photosynthesis molecular equation

6CO2 + 6H2O -Light→ C6H12O6 + 6O2

Photosynthesis word equation

Carbon dioxide + water -light→ oxygen + carbohydrates

Thylakoids

the disk-shaped structures inside chloroplasts

light reactions occur inside their membranes

Granum

stack of thylakoids

Lumen

fluid INSIDE the thylakoid

Stroma

-fluid OUTSIDE the thylakoid or inside the chloroplast -Calvin Cycle occurs here

Location of Photosynthesis

Chloroplast in palisade mesophyll

Meaning of "Photosynthesis"

Photo: reactions that occur in the thylakoids

Synthesis: PGAL formation

Photosystem 2

Water gets oxidized by photons and split by photolysis

Photosystem 1

-receives e- from the first ETC

Location of Calvin Cycle

The stroma

Protons from H2O

Power chemiosmotic phosphorylation

Faciliated Diffusion

How protons move through ATP synthase

Thylakoid Membrane

Site of chlorophyll molecules

Contains PS1 and PS2

Composed of phospholipids and proteins

G3P/PGAL

Formed immediately after reduction of BPG by NADPH

BPG

P-C-C-C-P

Formed when PGA is phosphorylated by ATP

PGA

P-C-C-C

Formed when unstable 6-C intermediate splits in two

RuBP

P-C-C-C-C-C-P

5 carbon molecule that is combined with CO2

Order of Carbon Reactions

Rubisco fixes CO2 to RuBP

PGA is formed from an unstable 6-carbon intermediate

PGA is phosphorylated to form BPG

NADPH reduces BPG to form PGAL/G3P

G3P molecules are arranged to produce RuBP

Order of Light Reactions

Light excites electrons in PS2

Electrons from PS2 pass along the ETC

The ETC uses energy from electrons to move H+ across the membrane

H+ gradient is established

H+ diffuses through ATP synthase

Energy of H+ flow used by ATP synthase to make ATP

Photorespiration

A respiratory process in C3 plants by which they take up oxygen during the Calvin cycle and give out some carbon dioxide, contrary to the general pattern of photosynthesis

Occurs in when the oxygen is trapped inside the leaves of C3 plants

Photoinhibition

Light-induced damage to photosynthetic proteins from a basic solution or hydrogen peroxide

Photosystems

Clusters of photosynthetic pigments and proteins