General Biology 1 - Photosynthesis and Light Reactions
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Questions and Answers

What is the primary function of Photosystem II?

  • To synthesize ATP
  • To transport electrons to NADPH
  • To split water molecules (correct)
  • To absorb light and excite electrons (correct)

NADPH is formed by the photolysis of water during light-dependent reactions.

False (B)

What are the two main products of the light-dependent reactions?

ATP and NADPH

The split water molecules during light-dependent reactions release ______ as a waste product.

<p>oxygen</p> Signup and view all the answers

Which of the following statements regarding the electron transport chain in light-dependent reactions is true?

<p>It links Photosystem I and Photosystem II. (D)</p> Signup and view all the answers

Match the following components with their roles in the light-dependent reactions:

<p>Photosystem I = Absorbs longer wavelengths (P700) Photosystem II = Absorbs shorter wavelengths (P680) Chlorophyll = Captures light energy Electron Transport Chain = Transfers electrons between photosystems</p> Signup and view all the answers

Cyclic pathways involve the production of both ATP and NADPH.

<p>False (B)</p> Signup and view all the answers

The light-dependent reactions occur within the ______ of chloroplasts.

<p>thylakoid</p> Signup and view all the answers

What is one of the main products of the light-dependent reactions of photosynthesis?

<p>Oxygen (C)</p> Signup and view all the answers

Photosystem II is responsible for the formation of NADPH.

<p>False (B)</p> Signup and view all the answers

What energizes the electron transport chain during the light reactions?

<p>The energy from electrons ejected by chlorophyll</p> Signup and view all the answers

The diffusion of protons (H+) across the membrane into the thylakoid ______ drives the production of ATP.

<p>lumen</p> Signup and view all the answers

What occurs in the noncyclic pathway of light-dependent reactions?

<p>The formation of both ATP and NADPH occurs (D)</p> Signup and view all the answers

What is the role of ATP synthase in the light-dependent reactions?

<p>To synthesize ATP from ADP and inorganic phosphate</p> Signup and view all the answers

Match the following components with their functions in the light-dependent reactions:

<p>Photosystem I = Produces NADPH Photosystem II = Boosts electrons for electron transport ATP synthase = Synthesizes ATP Electron transport chain = Transports electrons between photosystems</p> Signup and view all the answers

The second electron transport chain transfers electrons to ______, resulting in its reduction to NADPH.

<p>NADP+</p> Signup and view all the answers

Which of the following describes the cyclic pathway of light-dependent reactions?

<p>Electrons return to the same photosystem. (A)</p> Signup and view all the answers

The light-dependent reactions occur in the stroma of the chloroplast.

<p>False (B)</p> Signup and view all the answers

What is produced in the noncyclic pathway of light-dependent reactions?

<p>NADPH and ATP</p> Signup and view all the answers

In photosynthesis, the breakdown of water using light energy is called __________.

<p>photolysis</p> Signup and view all the answers

Match the following terms with their descriptions:

<p>Photosystem I = Function in cyclic electron flow Photosystem II = Initiates the noncyclic pathway NADPH = Electron carrier in photosynthesis ATP = Energy currency of the cell</p> Signup and view all the answers

What is the primary role of the electron transport chain in the light-dependent reactions?

<p>Transport electrons and produce ATP. (C)</p> Signup and view all the answers

Only ATP is produced in the cyclic pathway of light-dependent reactions.

<p>True (A)</p> Signup and view all the answers

Where do the light-independent reactions take place in the chloroplast?

<p>Stroma</p> Signup and view all the answers

Flashcards

Light-dependent Reactions

Chlorophyll captures light energy, storing it as ATP and NADPH.

Photolysis

Splitting water molecules using light energy.

Photosystem II (P680)

A light-harvesting complex that absorbs specific light wavelengths and excites electrons.

Electron Transport Chain (ETC)

A series of proteins that transfer excited electrons, creating a proton gradient.

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Photon

A particle of light carrying electromagnetic energy.

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Chlorophyll

A pigment that absorbs light energy in photosynthesis.

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ATP and NADPH

Energy-carrying molecules produced during the light-dependent reactions, used in the Calvin cycle.

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Oxygen (O2)

A byproduct of water splitting during the light-dependent reactions.

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What drives ATP production in light reactions?

The diffusion of protons (H+) across the thylakoid membrane through ATP synthase drives the production of ATP molecules.

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What is the role of Photosystem I?

Photosystem I generates NADPH, a key molecule for the light-independent reactions.

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What is the final electron acceptor in the second electron transport chain?

NADP+ is the final electron acceptor in the second electron transport chain, getting reduced to NADPH.

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Where does the second electron transport chain occur?

The second electron transport chain is located in the thylakoid membrane.

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How are electrons replaced in Photosystem I?

Electrons in Photosystem I are replenished by electrons passed down from the first electron transport chain, originating from Photosystem II.

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What is the role of the first electron transport chain?

The first electron transport chain pumps protons into the thylakoid lumen, creating a proton gradient.

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Products of Light Reactions

The light reactions produce oxygen, ATP, and NADPH.

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Purpose of ATP and NADPH

ATP and NADPH from light reactions are utilized in the Calvin cycle to convert carbon dioxide into glucose.

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Cyclic Pathway

A photosynthetic pathway where electrons from photosystem I are used to generate ATP, returning to the same photosystem.

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Noncyclic Pathway

A photosynthetic pathway where electrons from photosystem II are used to generate ATP and NADPH, ending in photosystem I.

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Calvin Cycle

The light-independent reactions of photosynthesis, occurring in the stroma of chloroplasts, where carbon dioxide is fixed into glucose.

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Carbon Fixation

The first step of the Calvin cycle, where CO2 is incorporated into an organic molecule (RuBP) by the enzyme rubisco.

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Reduction

The second step of the Calvin cycle, where energy from ATP and NADPH is used to convert 3-PGA to G3P.

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Regeneration

The third step of the Calvin cycle, where RuBP is regenerated so the cycle can continue.

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What is the difference between cyclic and noncyclic pathways?

Cyclic pathways use only photosystem I to generate ATP, while noncyclic pathways use both photosystems I and II to generate ATP and NADPH.

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What is the relationship between light-dependent and light-independent reactions?

Light-dependent reactions capture light energy and produce ATP and NADPH, which are used in light-independent reactions (Calvin Cycle) to convert CO2 into glucose.

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Study Notes

General Biology 1 - 12 STEM

  • This course covers Biology for students in Science, Technology, Engineering, and Mathematics (STEM) programs.
  • It includes study of 12 STEM topics.

Activity 1

  • Focuses on the vital role of the sun for organisms on Earth.

Week 3 Part A: Light-Dependent Reactions

  • This section details the patterns of electron flow through light reaction events.
  • Specific learning objectives are outlined.

Learning Objectives (Page 4)

  • Explain light-dependent reactions during photosynthesis.
  • Describe electron flow during light reactions.
  • Differentiate cyclic and noncyclic pathways of light reactions.

Activity 2

  • Analyzes the process of photosynthesis from a diagram.
  • Explains reactants and products as a chemical reaction.
  • Clarifies the concept of autotrophs in relation to plants.

Photosynthesis as a Chemical Reaction (Page 6)

  • Input: 6 Carbon Dioxide + 6 Water + Light energy
  • Output: Glucose + 6 Oxygen + Chlorophyll

Stages of Photosynthesis (Page 7)

  • Photosynthesis is a series of chemical reactions that convert carbon dioxide and water into glucose and oxygen.
  • Occurs in both presence and absence of sunlight.
  • Comprises light-dependent and light-independent reactions.

Location of Photosynthesis (Page 8)

  • Photosynthesis takes place in the chloroplast.
  • Specific structures within the chloroplast are identified, including the outer and inner membranes, thylakoid, and stroma.

Exercise 1: Guide Questions (Page 10)

    1. Role of photosystems in the thylakoid membrane of the chloroplast
    1. Electron flow within the thylakoid membrane
    1. Definition of photolysis
    1. ATP synthase's function in light-dependent reactions.
    1. Three important products of light-dependent reactions.

Light-dependent Reactions (Pages 11-14, 15)

  • Light-dependent reactions occur when solar energy is available.
  • These reactions happen in the thylakoid membrane of chloroplasts.
  • Primary function is converting solar energy into chemical energy.
  • Chlorophyll replaces "lost" electrons by splitting water molecules (photolysis).
  • Oxygen is a by-product of water splitting.
  • Electrons move through an electron transport chain to produce ATP and NADPH.

Electron Flow in Light Reaction (Pages 17-28)

  • Photosystem I and Photosystem II are key multi-protein complexes for harvesting photons.
  • Chlorophyll captures kinetic energy from photons.
  • Excited electrons are ejected from chlorophyll and moved to a specialized electron carrier.
  • Electrons are replaced through photolysis of water molecules, releasing oxygen.
  • Electron transport chain pumps hydrogen ions across thylakoid membrane, generating ATP.
  • The electron transport chain passes electrons to NADP+ reducing it to NADPH. This section describes the process in detail, including specific steps and molecules involved.

Products of Light-dependent Reactions (Page 28)

  • Oxygen, ATP, and NADPH.
  • These products are essential for the next stage of photosynthesis, the light-independent stage.

How do cyclic and noncyclic pathways differ? (Pages 29-30)

  • Cyclic pathway - electrons return to the same photosystem, only produces ATP
  • Noncyclic pathway - electrons from PSII are used by PSI, produces both ATP and NADPH.

Activity 3 (Page 37)

  • Investigates photosynthesis in the absence of light.

Activity 4 (Page 38)

  • Has guide questions about Light-independent Reactions.

Learning Objectives - Light-Independent Reactions (Page 35)

  • Elucidate different phases of the Calvin Cycle.
  • Identify factors that affect phases of the Calvin Cycle.
  • Determine the inputs and outputs of photosynthesis in both light-dependent and light-independent reactions.
  • Simulate the process of photosynthesis.

Light-independent reactions (Calvin Cycle) (Pages 36-43, 45-55)

  • Calvin Cycle takes place in the stroma.
  • Carbon dioxide enters the cycle.
  • RuBP is used to fix carbon dioxide, resulting in glucose.
  • ATP and NADPH from light-dependent reactions are essential inputs for the cycle.
  • The cycle includes carbon fixation, reduction, and regeneration phases in order to produce glucose, ultimately.
  • The main product of the cycle is glucose.
  • The cycle must complete six turns to synthesize one glucose molecule.

Summary of Chemical Reactions in Photosynthesis (Page 56)

  • Shows overall reactions in the two stages.

Exercise 3: Guide Questions (Page 57)

    1. Calvin cycle is the enzyme-mediated stage.
    1. Phase of the Light-independent reaction is the carbon fixation.
    1. Phase of light-independent reaction is reduction.
    1. Regenerates RuBP to prepare for succeeding carbon fixation.
    1. Glyceraldehyde-3-phosphate (G3P).

Let's Sum It Up! (Page 58)

  • Diagram showing the overall process of photosynthesis, its stages, and location.

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General Biology 1 12 STEM PDF

Description

This quiz focuses on the role of the sun and light-dependent reactions in photosynthesis as part of the General Biology 1 course for STEM students. It covers key concepts such as electron flow, cyclic and noncyclic pathways, and the chemical process of photosynthesis. Assess your understanding of these vital biological processes.

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