Photosynthesis Overview and Plant Types
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Questions and Answers

In C3 plants the conservation of water promotes _____

photorespiration

In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells.

cytoplasm

C4 plants differ from C3 and CAM plants in that C4 plants _____.

transfer fixed carbon dioxide to cells in which the Calvin cycle occurs

Which of these equations best summarizes photosynthesis?

<p>6 CO2 + 6 H2O → C6H12O6 + 6 O2</p> Signup and view all the answers

Where does the Calvin cycle occur?

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

The light reactions of photosynthesis use _____ and produce _____.

<p>water...NADPH</p> Signup and view all the answers

Plants are photoautotrophs. What does this mean?

<p>They use light energy to drive the synthesis of organic molecules from inorganic materials.</p> Signup and view all the answers

Under what conditions do photosynthesis and cellular respiration occur in most plants?

<p>Photosynthesis occurs only in the light, and cellular respiration occurs in both the dark and the light.</p> Signup and view all the answers

_____ has a longer wavelength than _____.

<p>Red has a longer wavelength than green.</p> Signup and view all the answers

In the electromagnetic spectrum, the type of radiation that we call visible light occurs between _____.

<p>ultraviolet radiation and infrared radiation.</p> Signup and view all the answers

Which of the following is a product of the light reactions of photosynthesis?

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

Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be reddish yellow. What wavelengths of visible light are absorbed by this pigment?

<p>blue and violet</p> Signup and view all the answers

As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in one hour. You find that 30,000 molecules of ATP were consumed, but only 20,000 molecules of NADPH were consumed. What is the source of the extra ATP molecules?

<p>cyclic electron flow</p> Signup and view all the answers

Carbon dioxide is split to form oxygen gas and carbon compounds in which of the following metabolic pathways?

<p>neither photosynthesis nor respiration</p> Signup and view all the answers

Which process produces oxygen?

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

Which set of reactions uses H2O and produces O2?

<p>The light-dependent reactions</p> Signup and view all the answers

What is the importance of the light-independent reactions in terms of carbon flow in the biosphere?

<p>The light-independent reactions turn CO2 into usable carbon in the form of sugars.</p> Signup and view all the answers

True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.

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

Which of the following molecules is the primary product of photosystem I?

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

What is the biological significance of the light-independent reactions of photosynthesis?

<p>They convert carbon dioxide to sugar.</p> Signup and view all the answers

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?

<p>The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.</p> Signup and view all the answers

Which molecule is regenerated in the regeneration phase of the Calvin cycle? Without regeneration of this molecule, the Calvin cycle would stop.

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

The overall function of the Calvin cycle is _____.

<p>making sugar</p> Signup and view all the answers

Which of the following sequences correctly represents the flow of electrons during photosynthesis?

<p>H2O → NADPH → Calvin cycle</p> Signup and view all the answers

CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they _____.

<p>fix CO2 into organic acids during the night.</p> Signup and view all the answers

Why are C4 plants able to photosynthesize with no apparent photorespiration?

<p>They use PEP carboxylase to initially fix CO2.</p> Signup and view all the answers

In which of the following plants would Photosystem II be most efficient?

<p>A plant that produces few hydroxyl radicals and superoxides.</p> Signup and view all the answers

Which of the following is the product of the electron transport system in Photosystem II?

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

You apply this research to the world's number one food crop, rice. Which of the following are you looking for using mass spectrometry?

<p>Modified amino acid residues</p> Signup and view all the answers

Why are reactive oxygen species problematic in Photosystem II?

<p>They damage proteins.</p> Signup and view all the answers

If plants could be genetically altered to improve Photosystem II, which of the following would occur?

<p>The altered plants would release more oxygen.</p> Signup and view all the answers

Why are plants classified as producers?

<p>Plants are classified as producers because they fix inorganic carbon into organic molecules.</p> Signup and view all the answers

Study Notes

Photosynthesis Overview

  • Photosynthesis Equation: 6 CO2 + 6 H2O → C6H12O6 + 6 O2 summarizes the overall process.
  • Location of Calvin Cycle: Occurs in the stroma of chloroplasts.
  • Role of Light Reactions: Use water to produce NADPH, oxygen, and ATP.

Plant Types and Photosynthesis

  • C3 Plants: Face photorespiration due to water conservation limiting CO2 availability.
  • C4 and CAM Plants: Fix carbon in the cytoplasm of mesophyll cells, allowing them to minimize photorespiration.
  • C4 Plants: Transfer fixed CO2 to the cells where the Calvin cycle occurs separately.

Importance of Light Reactions

  • Light Reactions Products: Generate NADPH, ATP, and oxygen as by-products.
  • Role of NADPH: Supplies energy for sugar production during the Calvin cycle.

Light-independent Reactions

  • Importance: Convert CO2 into usable sugars, crucial for carbon flow within the biosphere.
  • RuBP Regeneration: Essential for the Calvin cycle to continue, enabling continued carbon fixation.

Electrical Flow in Photosynthesis

  • Electron Flow Sequence: H2O → NADPH → Calvin cycle illustrates how electrons move through the process.
  • Photosystem II: Produces oxygen by splitting water and generating reactive oxygen species, which can damage proteins.

Plant Adaptations

  • CAM Plants: Adapted to close stomata during the day, fixing CO2 into organic acids at night to conserve water.
  • C4 Plants and PEP Carboxylase: Efficient photosynthesis without photorespiration via unique CO2 fixation.

Experimental Applications

  • Oxygen Production: Plants modified to improve Photosystem II could enhance oxygen release.
  • Mass Spectrometry in Rice: Identifying modified amino acid residues for agricultural research.

General Photosynthesis Facts

  • Photoautotroph Definition: Plants that use light energy to synthesize organic molecules from inorganic materials.
  • Reactive Oxygen Species: By-products of photosynthesis that can cause damage yet are part of essential processes.

Plant Classification

  • Producers: Plants fix inorganic carbon into organic molecules, fulfilling a critical role in ecosystems.

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Description

Explore the essential processes of photosynthesis, including the equations that define it and the roles of light and light-independent reactions. This quiz covers the distinctions between C3, C4, and CAM plants, highlighting how these variations adapt to their environments. Test your knowledge of the Calvin cycle and the importance of light reactions in energy production.

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