Photosynthesis Overview

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Questions and Answers

What is the main purpose of photosynthesis?

To convert sugars into energy

To capture energy from the sun and produce sugars (correct)

To produce energy in the form of ATP

To release oxygen as a byproduct

Where do the light-dependent reactions of photosynthesis occur?

In the chloroplast outer membrane

In the chloroplast stroma

In the chloroplast thylakoid membrane (correct)

In the cytoplasm of the cell

What are the components produced during the light-dependent reactions?

H+ ions, electrons, and oxygen gas (correct)

ADP and NADPH

Glucose and oxygen

ATP and carbon dioxide

What role does compartmentalization of the chloroplast play in photosynthesis?

It decreases competition between reactions Signup and view all the answers

Which photosystems are involved in the light-dependent reactions?

Photosystem 1 and 2 Signup and view all the answers

What is the primary role of NADP in the light-dependent reactions?

To act as the final electron acceptor Signup and view all the answers

What process produces ATP during the light-dependent reactions?

Photophosphorylation Signup and view all the answers

Which of the following correctly explains the role of the proton gradient in ATP production?

It generates a flow of protons through ATP synthase to produce ATP. Signup and view all the answers

What is chemiosmosis?

The use of a proton gradient to form ATP. Signup and view all the answers

How many ATP molecules are produced during oxidative phosphorylation?

30 or more Signup and view all the answers

Which molecule acts as an electron carrier in the Krebs cycle?

FADH2 Signup and view all the answers

What is the main purpose of the Calvin cycle?

To convert CO2 into organic carbohydrates Signup and view all the answers

What happens to electrons at the end of the electron transport chain in mitochondria?

They are accepted by oxygen to form water. Signup and view all the answers

Which of the following is NOT used to generate ATP during cellular respiration?

Glucose directly Signup and view all the answers

What is phosphorylation?

The addition of a phosphate group to a molecule Signup and view all the answers

Which enzyme synthesizes ATP during chemiosmosis?

ATP synthase Signup and view all the answers

Which process occurs in the cytosol of eukaryotic cells?

Glycolysis Signup and view all the answers

What byproduct is formed when oxygen accepts electrons in the electron transport chain?

Water Signup and view all the answers

Study Notes

Photosynthesis

Photosynthesis captures solar energy to produce sugars, occurring in prokaryotes (like cyanobacteria) and eukaryotic autotrophs.
In eukaryotes, photosynthesis takes place in chloroplasts.
Chloroplasts are double-membrane organelles, compartmentalized into thylakoids (stacked into grana) and stroma (fluid region).
Compartmentalization increases surface area and reduces competition, enhancing reaction efficiency.
Two main processes: light-dependent reactions (thylakoid) and Calvin cycle (stroma).

Light-Dependent Reactions

Occur in the thylakoid membrane and compartment.
Thylakoid membrane contains proteins (e.g., Photosystem II, proton pump, Photosystem I) and other electron transport proteins.
Water is split, releasing H⁺ ions (protons), electrons, and oxygen.
Electrons enter Photosystem II.
Photosystems contain chlorophyll, absorbing light energy to excite electrons.
Excited electrons travel through an electron transport chain (ETC).
Energy released during electron transfer powers the proton pump.
Proton pump actively transports protons from stroma to thylakoid compartment.
This creates a proton gradient (difference in proton concentration and charge across the thylakoid membrane).
This gradient is needed to produce ATP.
Lower-energy electrons enter Photosystem I.
Photosystem I re-excites electrons using absorbed light energy.
Excited electrons are picked up by NADP⁺, converting it to NADPH, an electron carrier.
NADPH carries electrons to the Calvin cycle.

ATP Production

ATP synthase is a membrane enzyme.
Chemiosmosis is the flow of protons down the concentration gradient through ATP synthase.
ATP synthase uses this energy to produce ATP from ADP and inorganic phosphate (photophosphorylation).
The original energy source is light.
Both NADPH and ATP from light-dependent reactions support the Calvin cycle.

Calvin Cycle

Occurs in the stroma of the chloroplast.
CO₂ is converted into organic carbohydrates (sugars) through a series of enzyme-catalyzed reactions.
NADPH and ATP power these reactions.
Conversion of NADPH to NADP⁺ and ATP to ADP releases energy to facilitate metabolic processes.

Cellular Respiration

Cellular Respiration is a series of enzyme-catalyzed reactions with three major steps:
- Glycolysis (cytosol)
- Krebs Cycle (mitochondrial matrix)
- Electron Transport Chain & Oxidative Phosphorylation (inner mitochondrial membrane).
Glycolysis breaks down glucose into pyruvate, producing 2 ATP and NADH.
Pyruvate enters the mitochondria, further oxidized in the Krebs Cycle to produce more NADH, FADH₂, 2 ATP, and CO₂.
Electron carriers (NADH and FADH₂) enter the Electron Transport Chain (ETC).
ETC is a series of protein channels in the inner mitochondrial membrane.
Electrons are passed, generating energy to actively transport protons from the matrix to the intermembrane space, creating a proton gradient.
Oxygen acts as the final electron acceptor in the ETC, forming water.
ATP synthase uses the flow of protons (chemiosmosis) down their gradient to produce ATP (oxidative phosphorylation).
Without oxygen, the ETC and ATP production stop, limiting cellular function.

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Description

Explore the intricate process of photosynthesis, where solar energy is transformed into sugars. Learn about the distinct stages, including light-dependent reactions and the Calvin cycle, and discover the role of chloroplasts and thylakoids in this essential biological function.