Cheat sheet 5: Photosynthesis

Photosynthesis

The process by which light energy is converted into chemical energy in the form of glucose.

Chloroplast

A double-membraned organelle in plant cells where photosynthesis takes place.

Thylakoid

A membrane-bound compartment inside chloroplasts that contains chlorophyll and is the site of the light-dependent reactions.

Granum

A stack of thylakoids within the chloroplast, where light reactions occur.

Chlorophyll

A green pigment found in plants that absorbs light energy for photosynthesis.

Light Reaction

- The electrons trapped in PSII are energized by light.

- 2 electrons are passed to a primary electron acceptor and move through the ETC

- These two electrons lose their energy, which is used to form 1.5 ATP

(ETC ends at PSI. Electrons are re-energized and passed to a different primary electron acceptor. can do cyclic or non cylic path)

Calvin cycle (dark reactions)

The light-independent reactions of photosynthesis that fix carbon dioxide into glucose (2 G3P)

What is the reaction in the calvin cycle that is catalyed by the enzyme RuBisCo?

1st step Carboxylation: 6 CO2 + 6 RuBP > 12 PGA

What does the reduction step (2nd step) do

12 ATP + 12 NADPH coverts 12 PGA to 12 G3P or 12GAL

The byproducts NADP + ADP go into non cyclic photophosphorlation

What does the regeneration step (3rd step) do of the Calvin cycle?

6 ATP convert 10 G3P to 6 RuBP

What does the carbohydrate synthesis step of the calvin cycle do?

remaining 2 G3P used to from glucose!

Photolysis

The process of splitting water molecules into oxygen, protons, and electrons during the light reactions.

Cyclic Photophosphorylation

A process in which 2 electrons from photosystem I (PSI) go back through the ETC and generate 1 ATP

(these 2 electrons are recycled into PSI and can either go through the cyclic or non cycle pathway again)

Non-Cyclic Photophosphorylation

2 electrons go through an ETC and combine with NADP+ and H+ to from NADPH

(this NADPH is used in the calvin cycle to create glucose)

RuBisCO

An enzyme that catalyzes the first step of the Calvin Cycle, fixing carbon dioxide into an organic molecule.

G3P

A three-carbon sugar produced during the Calvin Cycle that can be used to form glucose.

Chemiosmosis

The movement of ions across a selectively permeable membrane, generating ATP through ATP synthase.

C4 Photosynthesis

Alters location of photosynthesis

• CO2 moved to bundle sheath cells to minimize photorespiration & H2O loss

• Produces an intermediary 4-carbon

compound & uses 1 extra ATP

CAM Photosynthesis

Alters timing of photosynthesis

• Fixes CO2 at night instead of

day to minimize

photorespiration & H2O loss

Action Spectrum

A graph that shows the effectiveness of different wavelengths of light in driving photosynthesis.

(Chloroplast highly effective at absorbing red and blue light. Green wavelength are reflected)

Stroma

The fluid-filled space in chloroplasts where the Calvin Cycle takes place.

Stroma Lamellae

location of cyclic photophosphorylation

Thylakoid Membrane

The membrane surrounding thylakoids, where the light-dependent reactions occur.

(Location of ETC/ Structure that absorbs light)

Thylakoid Lumen

Location of photolysis. H+ ions accumulates due to ETC

ATP Synthase

An enzyme that synthesizes ATP from ADP and inorganic phosphate using a proton gradient.

Photons

Particles of light that provide the energy needed for photosynthesis.

Carotenoids

Pigments in plants that absorb light energy and protect chlorophyll from damage.

Intermembrane Space

The space between the inner and outer membranes of the chloroplast.