photosynthesis hl2

Photosynthesis

The process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose

Chloroplast

The organelle where photosynthesis takes place, containing thylakoids, grana, and stroma

Chlorophyll

The main photosynthetic pigment that absorbs light energy (primarily red and blue wavelengths) and reflects green

Light-dependent reactions

Reactions that occur in the thylakoid membranes and use light energy to produce ATP and NADPH

Light-independent reactions (Calvin Cycle)

Reactions that occur in the stroma and use ATP and NADPH to fix CO₂ into glucose

Photosystem II (PSII)

The first protein complex in the light-dependent reactions that absorbs light, splits water, and releases oxygen

Photolysis

The splitting of water molecules by light in PSII, producing electrons, protons (H⁺), and oxygen gas

Photosystem I (PSI)

The second protein complex in the light-dependent reactions that re-energizes electrons to produce NADPH

Electron transport chain (ETC)

A series of proteins in the thylakoid membrane that transfer electrons and pump protons to build a proton gradient

ATP synthase

An enzyme in the thylakoid membrane that uses the proton gradient to produce ATP from ADP + Pi

Chemiosmosis

The movement of protons across the thylakoid membrane through ATP synthase, driving ATP production

NADP⁺ reductase

The enzyme that transfers electrons to NADP⁺, into NADPH

Cyclic photophosphorylation

A pathway where electrons from PSI cycle back to the ETC, producing ATP but no NADPH or oxygen

Non-cyclic photophosphorylation

The main pathway where electrons flow from water to NADP⁺, producing ATP, NADPH, and oxygen

Calvin Cycle

A cycle of light-independent reactions that fixes CO₂ into carbohydrates using ATP and NADPH

Carbon fixation

The incorporation of CO₂ into RuBP (ribulose bisphosphate) by the enzyme rubisco

Rubisco

The enzyme that catalyzes the fixation of CO₂ to RuBP in the Calvin Cycle

3-phosphoglycerate (3-PGA)

The first stable product formed when CO₂ is fixed to RuBP

G3P (glyceraldehyde-3-phosphate)

A 3-carbon sugar produced in the Calvin Cycle that can be used to form glucose and other carbohydrates

Regeneration of RuBP

The process of using ATP to recycle G3P back into RuBP, allowing the Calvin Cycle to continue

Stroma

The fluid-filled space of the chloroplast where the Calvin Cycle takes place

Thylakoid

A flattened sac-like membrane in chloroplasts that contains pigments and is the site of light-dependent reactions

Granum (plural: grana)

A stack of thylakoids that increases surface area for light absorption

Action spectrum

A graph showing the rate of photosynthesis at different wavelengths of light

Absorption spectrum

A graph showing the specific wavelengths of light absorbed by pigments like chlorophyll

Limiting factors of photosynthesis

Factors such as light intensity, CO₂ concentration, and temperature that can restrict the rate of photosynthesis

Photorespiration

A wasteful process where rubisco fixes oxygen instead of CO₂

Stages limited due to dehydration

decrease in chlorophyll for light dependent reactions. Decrease of Co2 accumulation slows light independent reactions due to stomatal closure.

Relationship between spectrums

They mirror each other. Positive correlation between absorption spectrum and action spectrum.

Photosystem II most reactive to ____

680 nanometers

Photosystem I most reactive to _____

700 nanometers