Test 2 CH 14 pt.2

Question 1

Photosynthesis Overview

Answer 1

Question 2

comparison of mitochondria and chloroplast

Answer 2

Question 3

Chloroplast structure

Answer 3

Question 4

Summary of Photosynthesis in Chloroplast (Stage 1)

Answer 4

Location: Thylakoid membrane

📍 Main goal: Convert light energy into chemical energy (ATP & NADPH)

Light energy is absorbed by chlorophyll, exciting electrons.

Water (H₂O) is split to provide electrons, releasing oxygen (O₂) as a byproduct.

Electrons move through the photosynthetic electron transport chain, pumping protons (H⁺) to create a gradient.

ATP is synthesized via chemiosmosis (by ATP synthase).

NADPH is produced, carrying electrons for the next stage.

Outputs: ATP, NADPH (energy carriers), and O₂ (waste).

Question 5

Summary of Photosynthesis in Chloroplast (stage 2)

Answer 5

📍 Location: Stroma (fluid inside the chloroplast)

📍 Main goal: Use ATP & NADPH to fix CO₂ into organic molecules (sugar, amino acids, fatty acids).

Carbon dioxide (CO₂) enters the cycle.

ATP & NADPH provide energy and electrons to power carbon fixation (turning CO₂ into glucose precursors).

The cycle produces sugar, amino acids, and fatty acids, which can be used for plant growth and metabolism.

Outputs: Glucose precursors, amino acids, fatty acids (used to make larger molecules).

Question 6

Big Picture Summary of Photosynthesis in Chloroplast (Stage 1 and 2)

Answer 6

🔆 Stage 1 (Light Reactions): Converts light into ATP & NADPH, releases O₂.

🌱 Stage 2 (Calvin Cycle): Uses ATP & NADPH to turn CO₂ into sugars and other organic molecules.

This is how plants trap sunlight energy and turn it into food! 🌿⚡

Question 7

Photophosphorylation

Answer 7

light energy + ETC+ chemiosmosis which ATP synthesis is by

Question 8

Photosphorylation explanation

Answer 8

1. Light Excites Electrons in Photosystem II (PSII):

-Light energy is absorbed by Photosystem II (PSII), exciting electrons (e⁻) in chlorophyll.

-These high-energy electrons leave PSII and travel down the electron transport chain (ETC).

-To replace lost electrons, water (H₂O) is split, releasing oxygen (O₂) and protons (H⁺) into the thylakoid space.

2. Electron Transport and Proton Pumping:

-Electrons pass through plastoquinone (Q) and the cytochrome b₆-f complex.

-As electrons move through the cytochrome b₆-f complex, H⁺ ions (protons) are pumped from the stroma into the thylakoid space.

-This creates a proton gradient, with high H⁺ concentration inside the thylakoid space and low H⁺ concentration in the stroma.

3. Chemiosmosis and ATP Synthesis:

-The H⁺ gradient stores potential energy.

-Protons flow back into the stroma through ATP synthase (yellow structure in the diagram).

-As protons pass through ATP synthase, ATP is generated from ADP + Pi (phosphate) via chemiosmosis.

Question 9

Key Concepts for photophosphorylation

Answer 9

✅ Photophosphorylation = ATP synthesis using light energy, ETC, and chemiosmosis.
✅ ETC pumps protons into the thylakoid space, creating a proton gradient.
✅ ATP synthase uses the proton gradient to generate ATP.
✅ This ATP will be used in the Calvin cycle to power sugar synthesis.

Bigger picture:
🔆 Light powers electron movement → ETC pumps H⁺ → Proton gradient forms → ATP synthase makes ATP 💡➡️⚡➡️🔋

This process is essential for photosynthesis, as it provides the energy (ATP) needed for the Calvin cycle! 🌿🚀

Question 10

ETC in the thylakoid membrane

Answer 10

1. Light Excites Electrons in Photosystem II (PSII):

Light energy is absorbed by Photosystem II (PSII), exciting electrons (e⁻) in chlorophyll.

These high-energy electrons leave PSII and move down the electron transport chain (ETC).

To replace lost electrons, water (H₂O) is split by a water-splitting enzyme, releasing:
-Oxygen (O₂) as a byproduct
-Protons (H⁺) into the thylakoid space
-Electrons (e⁻) that replace those lost by PSII

2. Electron Transport and Proton Pumping:

Electrons move through the ETC, passing through plastoquinone (Q) and the cytochrome b₆-f complex.

Cytochrome b₆-f pumps protons (H⁺) into the thylakoid space, creating a proton gradient.

Electrons then pass to plastocyanin (PC), which carries them to Photosystem I (PSI).

3. Light Excites Electrons in Photosystem I (PSI):

Another photon of light excites electrons in PSI, boosting them to an even higher energy level.

Excited electrons are transferred to ferredoxin (Fd), then to ferredoxin-NADP⁺ reductase (FNR).

FNR reduces NADP⁺ to NADPH, which carries high-energy electrons to the Calvin cycle for sugar production.

4. ATP Synthesis via Chemiosmosis:

The H⁺ concentration inside the thylakoid space is now much higher than in the stroma, forming a proton gradient.

Protons (H⁺) flow back into the stroma through ATP synthase, which uses this energy to produce ATP from ADP + Pi.

ATP will also be used in the Calvin cycle to synthesize sugars.

Question 11

Photosynthetic light reactions

Answer 11

Light provides the energy to reduce NADPH

-electrons move from H20 to NAD+ + H20

Question 12

Key takeaways of ETC in thylakoid membrane and bigger picture

Answer 12

✅ PSII absorbs light → electrons are energized → water is split to replace lost electrons, releasing O₂.
✅ ETC pumps protons (H⁺) into the thylakoid space, building a proton gradient.
✅ PSI absorbs light → electrons are energized again → NADPH is produced.
✅ ATP synthase uses the proton gradient to generate ATP.
✅ ATP & NADPH power the Calvin cycle (next stage of photosynthesis).

Big Picture Summary:
☀️ Light energy → ⚡ Excited electrons → 🌊 Water splitting (O₂ released) → 🔋 ATP & NADPH made → 🌱 Energy for the Calvin cycle

This is how plants convert sunlight into chemical energy! 🌿⚡

Question 13

Chlorophyll Molecule

Answer 13

Hydrophobic tail
anchors in thylakoid
membrane
Porphyrin ring with
Mg++ ion.

Light absorbed by exciting
electrons alternating in
double and single bonds

Question 14

How are Chlorophyll molecules arranged within photosystems

Answer 14

1. Light Absorption:

Light (photons) excites electrons in chlorophyll molecules.
The light-harvesting antenna complexes contain multiple chlorophyll molecules that capture and transfer energy.

2. Energy Transfer in Antenna Complexes:

Energy is passed from one chlorophyll molecule to another in a process called resonance energy transfer.
The goal is to direct the energy toward a reaction center.

3. Reaction Center & Special Pair:

The reaction center contains a special pair of chlorophyll molecules that can transfer an excited electron.
This electron transfer is the first step in the light-dependent reactions of photosynthesis.

4. Role of the Thylakoid Membrane:

The photosystem is embedded in the thylakoid membrane.
This setup is essential for photosynthesis as it facilitates the electron transport chain.

Why This Is Important for Photosynthesis?
This setup allows plants and photosynthetic organisms to convert light energy into chemical energy, which is used to power the Calvin cycle and produce glucose.

Question 15

Key Takeaways of how chlorophyll molecules are arranged within photosystems

Answer 15

Photosystems are protein-pigment complexes in the thylakoid membrane.

Light energy excites chlorophyll molecules, transferring energy through resonance energy transfer.

The reaction center chlorophyll special pair donates an excited electron, starting the electron transport chain.

This process is essential for photosynthesis, as it helps generate ATP and NADPH.

Question 16

Reaction Center

Answer 16

In a reaction center, a high-energy electron is transferred from the chlorophyll
special pair to a carrier that becomes part of an electron-transport chain.

Question 17

Two Photosystems Move Electrons from H20 to NADP+

Answer 17

 Photosystem II reduces Photosystem I, using
excitation of a chlorophyll and an electron transport chain

 Reduction of PSII uses electrons from H2O, producing O2 as a result
- PSII contains a water-splitting enzyme

 Photosystem I passes the electrons down an
electron transport chain to NADP+, reducing it to NADPH, using the excitation of another chlorophyll.

Question 18

Z- scheme of non-cyclic electron flow in photosynthesis

Answer 18

1.Light Absorption in Photosystem II (PSII) (680 nm)

Light excites electrons in PSII, boosting them to a higher energy level.

These high-energy electrons are transferred to a molecule called plastoquinone (Q).

To replace lost electrons, water is split (photolysis), producing:
-O₂ (oxygen gas, released)
-Protons (H⁺, contributing to the proton gradient)
-Electrons (used to replace lost electrons in PSII)

2.Electron Transport & ATP Production

-Electrons move down an electron transport chain (ETC) via the cytochrome b₆f complex.

-As electrons move, H⁺ ions are pumped into the thylakoid lumen, creating a proton gradient.

-This gradient drives ATP synthase, generating ATP (used later in the Calvin cycle).

3. Light Absorption in Photosystem I (PSI) (700 nm)

-The electrons from PSII arrive at PSI, but they have lost energy.

-Light excites them again to a higher energy state.

-High-energy electrons are transferred to ferredoxin (Fd).

4. Formation of NADPH

-Electrons from ferredoxin (Fd) are transferred to NADP⁺ reductase (FNR).
-This enzyme reduces NADP⁺ to NADPH using H⁺ ions.
-NADPH is later used in the Calvin cycle to help fix carbon into glucose.

Answer 19

Key Takeaways for Your Exam:

-Non-cyclic electron flow moves electrons linearly from H₂O → PSII → ETC → PSI → NADPH.

-Water is split at PSII, releasing O₂.

-ATP is made via the proton gradient created by cytochrome b₆f.

• NADPH is made at PSI and used in the Calvin cycle.

-The Z-shape represents the energy levels of electrons as they move through the process.

This is the main pathway of electron flow in light-dependent reactions, providing the energy needed for photosynthesis. Let me know if you need more details!

Question 20

Z-scheme of non-cyclic electron flow

Answer 20

in photosynthesis. It describes how electrons move through Photosystem II (PSII) and Photosystem I (PSI) to produce ATP and NADPH, which are needed for the Calvin cycle.

Question 21

Light-Independent reactions: Carbon Fixation Cycle

Answer 21

 Incorporates (inorganic) CO2 into organic molecules

 Does not use light directly

 Does use the energy of the light reactions in the form of ATP
and NADPH for reducing power

 Occurs in stroma

Question 22

1st step of Calvin Cycle Rubisco

Answer 22

Rubisco - Ribulose bisphophate carboxylase catalyzes the reaction that fixes carbon to an organic molecule

Rubisco is a slow enzyme, so chloroplast has many to combat its inefficiencies

Question 23

Calvin Cycle or Carbin fixation cycle

Answer 23

All ATP hydrolyzed
and NADPH oxidized
in the cycle comes
from the light
reactions

For every 3 CO2
fixed, 1 molecule of G3P
leaves the cycle to
make organic
molecules in the
plant cell, the
remaining 5 G3P
stay in the cycle to
regenerate ribulose
1,5-bisphophate to
keep the cycle going

Question 24

Fate of Glyceraldehyde 3-phosphate

Answer 24

-Transported to cytosol where its Converted to glucose
so, 2 molecules of G3P (3C) combine to make 1 molecule of
glucose (6C)

-Converted to disaccharides such as sucrose
-Converted to pyruvate
-Converted to intermediates of fatty acid and amino
acid synthesis
- Remain in stroma of chloroplast
-Stored as starch

Question 25

Summary of Photosynthesis

Answer 25

Summary of Photosynthesis

 Light Reaction in Thylakoid Membrane

 Light excites electrons in PSII

 Electrons derived from splitting of water by water splitting enzyme

 Electrons passed down ETC, protons pumped into thylakoid space

 Proton gradient used to drive ATP synthesis (photophosphorylation)

 Electrons donated to PSI

 Electrons in PSI excited by light

 Electrons passed down 2nd ETC, ultimately reduce NADP+ to NADPH

 Carbon Fixation in Stroma:

 CO2 enters Calvin Cycle
 Fixed to ribulose 1,5 bisphosphate by Rubisco
 ATP and NADPH from light reaction consumed
 Glyceraldehyde 3-phosphate produced as carbon source which is converted to glucose, sugar, etc.. and we eat it

Question 26

Calvin cycle

Answer 26

3 Main Phases of the Calvin Cycle:

1. Carbon Fixation (Yellow Section)
   CO₂ enters the cycle – 3 molecules of CO₂ combine with ribulose-1,5-bisphosphate (RuBP) (a 5-carbon molecule).
   This reaction is catalyzed by the enzyme Rubisco.
   The result is six molecules of 3-phosphoglycerate (3-PGA) (a 3-carbon compound).
2. Reduction (Red Section)
   ATP and NADPH are used to convert 3-PGA into G3P (glyceraldehyde-3-phosphate).
   6 ATP → 6 ADP (provides energy).
   6 NADPH → 6 NADP⁺ (provides high-energy electrons).
   This step creates G3P, a 3-carbon sugar that can later be used to form glucose.
3. Regeneration of RuBP (Blue Section)
   Out of 6 G3P molecules, only 1 leaves the cycle to form sugars, amino acids, or fatty acids.
   The remaining 5 G3P molecules are recycled to regenerate RuBP.
   This step requires 3 more ATP molecules, converting 3 ATP → 3 ADP.
   Key Takeaways
   ✅ What Goes In?

3 CO₂, 9 ATP, and 6 NADPH are used per cycle.
✅ What Comes Out?

1 G3P (used to build glucose & other molecules).
9 ADP and 6 NADP⁺ (returned to the light-dependent reactions).
✅ Why Is This Important?

The Calvin Cycle turns CO₂ into usable energy by forming organic molecules.
G3P is a key building block for glucose, starch, fats, and amino acids.
This cycle does not require light directly but relies on ATP & NADPH from the light reactions to function. Would you like a simpler breakdown or any part explained further? 😊