Photosynthesis in C3 Plants
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Questions and Answers

What characterizes C3 plants in relation to photosynthesis?

  • The initial product of photosynthesis has three carbon atoms. (correct)
  • The first carbon compound produced contains four carbon atoms.
  • They exclusively use light-dependent reactions to generate energy.
  • They produce glucose without the need for a carbon source.

Which statement accurately describes carbon fixation in the Calvin cycle?

  • The reaction functions independently without any specific enzymes.
  • CO2 is converted into organic molecules with the help of RuBisCO. (correct)
  • RuBP combines with energy-rich molecules to produce glucose directly.
  • It refers to the conversion of glucose into carbon dioxide.

During the reduction phase of the Calvin cycle, which process occurs?

  • Conversion of the 6-carbon compound into CO2.
  • RuBP is regenerated back to its original state without CO2.
  • ATP is used to oxidize G3P into a higher energy compound.
  • 3-PGA is converted into G3P through a reduction reaction. (correct)

What role does RuBisCO play in the Calvin cycle?

<p>It facilitates the reaction between CO2 and RuBP, initiating carbon fixation. (D)</p> Signup and view all the answers

Which of the following correctly identifies the primary products recycled back to the light-dependent reactions?

<p>NAD+ and ADP (D)</p> Signup and view all the answers

What is the primary function of chlorophyll in chloroplasts?

<p>To capture light energy for photosynthesis (D)</p> Signup and view all the answers

Which pigment absorbs light in the chloroplasts during photosynthesis?

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

What structural component of the chloroplasts contains chlorophyll?

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

During the fall, what happens to chlorophyll in most plants?

<p>It is greatly reduced, revealing other pigments (D)</p> Signup and view all the answers

What is the role of the stroma in chloroplasts?

<p>It acts as a fluid medium where the Calvin cycle occurs (A)</p> Signup and view all the answers

Which statement is correct regarding chlorophyll a and chlorophyll b?

<p>Chlorophyll a is primarily responsible for light absorption, while chlorophyll b assists in the process. (D)</p> Signup and view all the answers

In which part of the chloroplast does the light reaction of photosynthesis primarily occur?

<p>Within the thylakoid compartments (D)</p> Signup and view all the answers

What is the primary function of the light-dependent reactions in photosynthesis?

<p>To convert light energy into chemical energy (D)</p> Signup and view all the answers

Which process describes the combination of CO2 with hydrogen from water in photosynthesis?

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

What molecules are produced in the light-dependent reactions and are used in the light-independent reactions?

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

In photosynthesis, which term refers to the loss of electrons or the gain of oxygen?

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

Where do the light reactions of photosynthesis primarily occur?

<p>Within the chloroplasts (D)</p> Signup and view all the answers

What is released into the atmosphere as a byproduct of the light reactions?

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

What is the primary role of chlorophyll in the light reactions of photosynthesis?

<p>To absorb light energy (A)</p> Signup and view all the answers

During which phase of photosynthesis is glucose synthesized?

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

Which of the following best describes the process of water-splitting during photosynthesis?

<p>Water molecules are dissociated to release electrons (B)</p> Signup and view all the answers

What process replaces the missing electron in the special pair during photosynthesis?

<p>Electron sourced from PSII (C)</p> Signup and view all the answers

What is the end product when the high-energy electron is passed to NADP+?

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

Where does the Calvin Cycle occur within the chloroplast?

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

How many ATP molecules are consumed in six turns of the Calvin Cycle?

<p>18 (C)</p> Signup and view all the answers

Which of the following is a requirement for the light-independent reactions?

<p>CO2 (C)</p> Signup and view all the answers

What type of plants predominantly use the Calvin Cycle as described?

<p>C3 plants (B)</p> Signup and view all the answers

What are the substrates used by the Calvin Cycle to produce glucose?

<p>CO2 and Hydrogen (D)</p> Signup and view all the answers

Which part of the chloroplast is involved in the formation of NADPH during photosynthesis?

<p>Thylakoid (D)</p> Signup and view all the answers

Which of these best describes the function of ATP in the Calvin Cycle?

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

Which statement about the electron transport chain is incorrect?

<p>It directly produces glucose. (C)</p> Signup and view all the answers

What is the primary function of Photosystem II in the light reactions of photosynthesis?

<p>To extract electrons from water and produce O2 (A)</p> Signup and view all the answers

What is produced as a by-product during the light-dependent reactions when water molecules are split?

<p>O2 (A)</p> Signup and view all the answers

Where are Photosystem II and its associated reactions located within plant cells?

<p>In the thylakoid membrane (D)</p> Signup and view all the answers

Which component acts as an electron acceptor associated with Photosystem II?

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

How do the electrons flow after being extracted from water in Photosystem II?

<p>They flow down an electron transport chain (B)</p> Signup and view all the answers

In addition to producing O2, what is another key role of the electron flow in Photosystem II?

<p>Pumping hydrogen ions across the membrane (B)</p> Signup and view all the answers

What energy source is primarily captured by Photosystem II to initiate the light-dependent reactions?

<p>Photons from light (A)</p> Signup and view all the answers

Which of the following statements is false about the role of Photosystem II?

<p>It stores electrons instead of releasing them. (A)</p> Signup and view all the answers

What is the consequence of the electron flow triggering hydrogen ion pumping in Photosystem II?

<p>It increases the potential for ATP synthesis. (B)</p> Signup and view all the answers

Which process occurs directly after the electrons are extracted from water in Photosystem II?

<p>They enter a series of redox reactions in the electron transport chain. (A)</p> Signup and view all the answers

Flashcards

Heterotrophs: What do they consume?

Organisms that obtain their energy by consuming other organisms, either living or dead.

What is Photosynthesis?

The process by which plants convert light energy into chemical energy in the form of glucose.

What is Chlorophyll?

The green pigment found in chloroplasts that absorbs light energy for photosynthesis.

What are Chloroplasts?

Organelles within plant cells that are responsible for photosynthesis.

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What is Stroma?

The fluid-filled space within a chloroplast that surrounds the thylakoids.

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What are Grana?

Stacks of flattened membrane sacs within a chloroplast where chlorophyll is located.

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What are Thylakoids?

Flattened, membrane-bound compartments inside chloroplasts where light-dependent reactions of photosynthesis occur.

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What is Oxidation?

The loss of electrons from a substance; it involves the gain of oxygen.

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What is Reduction?

The gain of electrons to a substance; it involves the loss of oxygen.

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What is the Light-dependent reaction?

The first phase of photosynthesis, where light energy is converted into chemical energy in the form of ATP and NADPH.

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What is the Light-independent reaction?

The second phase of photosynthesis, where the chemical energy stored in ATP and NADPH is used to convert carbon dioxide into glucose.

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What is the Calvin Cycle?

A complex set of chemical reactions that occur in the stroma of chloroplasts, where carbon dioxide is converted into glucose.

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What is Water-splitting?

The process by which water molecules are split apart to release oxygen during photosynthesis.

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What is NADPH?

A molecule that carries electrons and acts as a reducing agent during photosynthesis, donating electrons to the Calvin Cycle.

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Photosystem II

The first protein complex in the light-dependent reactions of oxygenic photosynthesis. It captures photons and uses the energy to extract electrons from water molecules.

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Plastoquinone

A molecule involved in electron transport in photosynthesis, particularly in photosystem II. It acts as an electron acceptor in the process.

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Photosystem I

The second protein complex in the light-dependent reactions of oxygenic photosynthesis. It captures photons and uses the energy to generate high-energy electrons that are used to produce NADPH.

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Electron Transport Chain

A series of proteins and organic molecules embedded within the thylakoid membranes of chloroplasts. Electrons flow through this chain, releasing energy that is used to pump hydrogen ions across the membrane.

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Light-dependent Reactions

The process by which the energy from light is used to create ATP and NADPH, key molecules used in the Calvin cycle to produce glucose.

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Water Splitting

The process of converting molecules of water into oxygen gas, hydrogen ions, and electrons. This process occurs in photosystem II.

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Thylakoid Membranes

Tiny flat sacs within the chloroplast where light-dependent reactions take place.

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ATP

The main energy-carrying molecule used by cells. It is generated during the light-dependent reactions of photosynthesis.

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NADPH

A molecule that carries high-energy electrons from the electron transport chain to the Calvin cycle. It is generated during the light-dependent reactions of photosynthesis.

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Calvin Cycle

A series of reactions that utilize energy from ATP and NADPH to convert carbon dioxide into glucose.

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RuBP (Ribulose bisphosphate)

A five-carbon sugar molecule found in chloroplasts, with a phosphate group on each end. It serves as the initial substrate for carbon dioxide fixation during the Calvin cycle.

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6-C compound

A six-carbon compound formed when carbon dioxide combines with RuBP. It is immediately broken down into two molecules of 3-PGA.

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3-PGA (3-phosphoglyceric acid)

A three-carbon compound produced from the breakdown of the 6-C compound. It is then converted into G3P using energy from ATP and NADPH.

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Carbon Fixation

The process in which carbon dioxide is 'fixed' from an inorganic form into an organic molecule (3-PGA) within a plant cell.

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C3 Plants

Plants like corn and wheat that initially fix carbon dioxide into a 3-carbon compound. They are the most common type of plants.

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Stroma

The fluid-filled space within a chloroplast that surrounds the thylakoids, where the Calvin Cycle takes place.

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Study Notes

Photosynthesis Overview

  • Photosynthesis is the process where plants, some bacteria, and protists make their own food.
  • Autotrophs create organic matter (like glucose) from inorganic matter (like carbon dioxide).
  • Sunlight's energy is stored as chemical energy.
  • Photosynthesis is crucial because it creates most of the oxygen on Earth and provides the base of all food chains.
  • Photosynthesis involves converting carbon dioxide and water into glucose (sugar) and oxygen.

Importance of Photosynthesis

  • Creates organic molecules (glucose) from inorganic materials (carbon dioxide and water).
  • Supports all food chains and webs
  • Produces oxygen gas
  • Without photosynthesis, there would be little to no oxygen on Earth.

Why Plants are Green

  • Plants are green because chlorophyll absorbs most colors of light, with the exception of green, which it reflects.
  • Chlorophyll absorbs light energy for photosynthesis.
  • Chlorophyll is found within chloroplasts inside plant cells.
  • Chlorophyll molecules help capture light necessary to catalyze the reactions of the photosynthetic processes.
  • Different wavelengths of visible light are seen by the human eye as different colors.

Chloroplast Structure and Function

  • Chloroplasts house the pigments and components necessary for photosynthesis.
  • Chloroplasts contain chlorophyll.
  • Chlorophyll absorbs light for energy conversion.
  • The chloroplast contains stacks of thylakoids called grana, containing chlorophyll.
  • Stroma is a fluid surrounding the grana in the chloroplast.

Photosynthesis Steps

  • Two main stages: light-dependent reactions and light-independent reactions (Calvin cycle).
  • Light-dependent reactions: capture light energy and convert it into chemical energy in the form of ATP and NADPH.
  • Light-independent reactions (Calvin cycle): utilize ATP and NADPH from the light-dependent stage to fix carbon dioxide into glucose (sugar).

Photosynthesis Pigments

  • Chlorophyll a is the primary pigment responsible for absorbing light in the light-dependent reactions.
  • Chlorophyll b and carotenoids are accessory pigments enhancing light absorption.
  • Different pigments absorb light of different wavelengths.
  • Chloroplasts contain several pigments, including a and b, and carotenoids.
  • Chlorophyll absorbs most colors of light except for green, which it reflects.

Photosynthesis - Location and Structure

  • Photosynthesis occurs primarily in the leaves of plants.
  • Inside the leaves are chloroplasts, which contain stacks of thylakoids (grana).
  • The stroma is a fluid inside the chloroplast that acts as the site for the Calvin cycle.
  • Chlorophyll and other pigments within the thylakoid membranes are essential for absorbing light energy.
  • The chloroplast structure facilitates the processes of photosynthesis.

Fall Colors

  • Chlorophyll levels decrease in the fall, causing the green color to fade.
  • Other pigments (like carotenoids) become visible.
  • Carotenoids appear red or yellow in the fall.
  • Chlorophyll breaks down at a steady rate, as well as the need for replacement.
  • This results in the loss of the green color, revealing the existing carotenoids.

Photorespiration

  • Occurs under hot, dry conditions which favor water loss.
  • Oxygen is taken in instead of carbon dioxide in photorespiration.
  • This results in a loss of energy and the production of no sugar or ATP.
  • Stomatas close to conserve water during dry conditions.

Types of Photosynthesis Adaptations

  • C4 plants (e.g., grasses) spatially separate the light and dark reactions.

  • CAM plants (e.g., cacti, succulents) temporally separate light and dark reactions.

  • These adaptations reduce the amount of photorespiration allowing them to survive in specific environmental conditions.

  • C4 plants: have a special adaptation in which carbon is first fixed and then delivered to locations where the Calvin cycle is carried out (avoid photorespiration by concentrating CO2).

  • CAM plants: CO2 is fixed at night when stomata are open and used during the day when stomata are closed.

Light Reactions (Electron Transport)

  • Light reactions take place within the thylakoid membranes of the chloroplast.
  • Water is split, releasing oxygen as a byproduct.
  • Electrons are passed down an electron transport chain, generating ATP and NADPH.
  • ATP and NADPH are used in the Calvin cycle.
  • ATP synthesis and NADPH production take place in the thylakoid membrane.

Dark Reactions (Calvin Cycle)

  • The Calvin Cycle takes place in the stroma of the chloroplast.
  • CO2 enters the cycle and is converted into glucose using ATP and NADPH.
  • The cycle involves fixation, reduction, and regeneration.
  • Carbon dioxide from the atmosphere is incorporated into existing organic molecules so glucose can be created.
  • Calvin cycle does not need light to function and uses products from the light dependent stage.

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Description

This quiz explores the intricate details of photosynthesis, particularly focusing on C3 plants and the Calvin cycle. Questions cover key components like RuBisCO, chlorophyll, and the light-dependent reactions, ensuring a comprehensive understanding of the subject. Test your knowledge and see how well you grasp the processes involved in plant photosynthesis.

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