BIO 20 Ch. 7 Photosynthesis Quiz
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Questions and Answers

What is photosynthesis?

Plants use the sun's energy to convert water and carbon dioxide into sugars, and release oxygen as a by-product.

What are autotrophs?

Organisms that make their own food.

Define photoautotrophs.

An organism that harnesses light energy to drive the synthesis of organic compounds from carbon dioxide.

What are heterotrophs?

<p>An organism that obtains organic food molecules by eating other organisms or their by-products.</p> Signup and view all the answers

The _____ in plant cells capture light energy that comes from the sun.

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

What are chemoautotrophs?

<p>Prokaryotes that use inorganic chemicals as their energy source and are the producers in deep-sea vent communities.</p> Signup and view all the answers

What do 'self-feeding' photoautotrophs require from the environment to make their own food?

<p>Light, carbon dioxide, and water.</p> Signup and view all the answers

______ are the major sites of photosynthesis in most plants.

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

What is chlorophyll?

<p>A light-absorbing pigment in chloroplasts that plays a central role in converting solar energy to chemical energy.</p> Signup and view all the answers

What is mesophyll?

<p>Spongy tissue in the interior of the leaf where most chloroplasts are found.</p> Signup and view all the answers

What are stomata?

<p>Small openings on the underside of a leaf through which oxygen and carbon dioxide can move.</p> Signup and view all the answers

A typical mesophyll cell has about __ to __ chloroplasts.

<p>30, 40</p> Signup and view all the answers

What is stroma?

<p>Fluid portion of the chloroplast; outside of the thylakoids.</p> Signup and view all the answers

____ in the ____ form the framework within which many of the reactions of photosynthesis occur.

<p>Membranes, chloroplast</p> Signup and view all the answers

Which of the following organelles can open or close? Thylakoids are found in the __________.

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

What are thylakoids?

<p>Membranous structures within a chloroplast that serve as the site for light harvesting in photosynthesis.</p> Signup and view all the answers

Write the equation for photosynthesis.

<p>6 CO2 + 6 H2O ------&gt; C6H12O6 + 6 O2</p> Signup and view all the answers

What happens when CO2 and water are converted to sugar and O2?

<p>CO2 is reduced to C6H12O6; H2O is oxidized to O2.</p> Signup and view all the answers

Scientists used isotopes to identify the source of oxygen released during photosynthesis. What did they discover?

<p>O2 comes from the water, not CO2</p> Signup and view all the answers

What is the chemical formula for glucose?

<p>C6H12O6</p> Signup and view all the answers

During photosynthesis CO2 is reduced to _____ as _____ and ________ _______ are added to it.

<p>Sugar: electrons: hydrogen ions</p> Signup and view all the answers

During photosynthesis water molecules are ______.

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

Which of the following statements regarding the reduction of CO2 to sugar during photosynthesis is correct? Electrons (with accompanying protons)

<p>from water are transferred to CO2 during photosynthesis</p> Signup and view all the answers

What are the two stages of photosynthesis?

<p>Light reactions and Calvin cycle.</p> Signup and view all the answers

What are light reactions?

<ul> <li>Occurs in thylakoids</li> <li>Convert light energy to chemical energy and release O2</li> </ul> Signup and view all the answers

During light reactions _____ is split, providing _________ and giving off _____ as a by-product.

<p>water: electrons: O2</p> Signup and view all the answers

________ _______ is used to drive the transfer of _______ and ___ from water to the electron acceptor ______, reducing it to _______.

<p>Light energy: electrons: H+: NADP+: NADPH</p> Signup and view all the answers

What does NADPH temporarily store?

<p>Electrons and hydrogen ions.</p> Signup and view all the answers

What are the inputs of the light reaction?

<ol> <li>ADP + P</li> <li>NADP+</li> <li>H2O</li> <li>Light energy</li> </ol> Signup and view all the answers

What are the outputs of the light reaction?

<ol> <li>ATP</li> <li>NADPH</li> <li>O2 (waste product)</li> </ol> Signup and view all the answers

Describe the Calvin cycle.

<ul> <li>Occurs in the stroma of the chloroplast</li> <li>A series of reactions that assembles sugar molecules using CO2 and the energy-rich products of the light reaction.</li> </ul> Signup and view all the answers

What is carbon fixation?

<p>The incorporation of carbon into organic compounds.</p> Signup and view all the answers

______ provides the _______ for reducing _______ compounds in the Calvin cycle.

<p>NADPH: electrons: carbon</p> Signup and view all the answers

What are the inputs of the Calvin cycle?

<ol> <li>CO2</li> <li>ATP</li> <li>NADPH</li> </ol> Signup and view all the answers

What are the outputs of the Calvin cycle?

<ol> <li>G3P (3 carbon, 3 oxygen, 6 hydrogen)</li> <li>NADP</li> <li>ADP + P</li> </ol> Signup and view all the answers

The light reactions of photosynthesis yield __________. The Calvin cycle produces __________.

<p>O2, ATP, NADPH; sugar, ADP, NADP+</p> Signup and view all the answers

The reduction of NADP+ to NADPH in the light reactions occurs with the assistance of __________.

<p>electrons from water and energy from sunlight</p> Signup and view all the answers

What is wavelength?

<p>The distance between the crests of electromagnetic waves.</p> Signup and view all the answers

What is the electromagnetic spectrum?

<p>The full range of frequencies of electromagnetic waves.</p> Signup and view all the answers

What is chlorophyll A?

<p>A photosynthetic pigment that participates directly in the light reactions, absorbs mainly blue-violet and red light. Mainly reflects green.</p> Signup and view all the answers

What is chlorophyll B?

<ul> <li>Mainly absorbs blue and orange light and reflects olive green.</li> <li>Broadens the range of light a plant can use by conveying absorbed energy to chlorophyll A.</li> </ul> Signup and view all the answers

What are carotenoids?

<p>Usually various shades of orange and yellow. Helps broaden the spectrum of colors that can drive photosynthesis, however, most important function is photoprotection.</p> Signup and view all the answers

What is the most important function of carotenoid pigments in plants?

<p>protect cells from excess sunlight</p> Signup and view all the answers

What is a photosystem?

<p>A light-harvesting complex in the chloroplast thylakoid composed of pigments and proteins.</p> Signup and view all the answers

Describe the relationship between Photosystem 2 and Photosystem 1.

<ul> <li>Photosystem 2 functions first in the sequence of steps that make up the light reactions.</li> <li>Each has a characteristic reaction-center and a special pair of chlorophyll A molecules.</li> <li>Both work together to generate ATP and NADPH.</li> </ul> Signup and view all the answers

During the light reactions, __________ and an __________ transform __________ energy into __________ energy of ATP and NADPH.

<p>two photosystems; electron transport chain; light; chemical</p> Signup and view all the answers

What is the source of the electrons that are moving through the photosystems to NADPH?

<p>The electrons that end up reducing NADP+ to NADPH originally come from water.</p> Signup and view all the answers

In the thylakoid space water is split into __ electrons, __ hydrogen ion (H+), and __ oxygen atom (1/2 O2).

<p>2: 2: 1</p> Signup and view all the answers

What is the final electron acceptor in the light reactions of photosynthesis?

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

What is photophosphorylation?

<p>The production of ATP by chemiosmosis during the light reactions of photosynthesis.</p> Signup and view all the answers

Two separate processes occur in the light reactions of photosynthesis. In one, __________ is generated as the result of an electric transport chain. In the other, the high concentration of __________ in the thylakoid space drives the synthesis of __________.

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

List the steps of the Calvin cycle.

<ol> <li>Carbon fixation. The enzyme rubisco combines CO2 with RuBP, then the 6-carbon molecule splits into two 3-carbon molecules.</li> <li>Reduction. ATP and NADPH are used to reduce the 3-carbon molecule to G3P.</li> <li>Release of 1 molecule of G3P. For every 3 CO2 molecules that are fixed, 1 G3P is released.</li> <li>Regeneration of RuBP. The remaining 5 G3P molecules are rearranged, using ATP, to regenerate 3 molecules of RuBP.</li> </ol> Signup and view all the answers

To synthesize 1 glucose molecule, the Calvin cycle uses ___ CO2, ___ ATP, ___ NADPH.

<p>6: 18: 12</p> Signup and view all the answers

At which step of the 4-step Calvin cycle is G3P produced?

<p>reduction, step 2</p> Signup and view all the answers

How many molecules of ATP and NADPH are required to make one molecule of G3P in the Calvin cycle?

<p>9 ATP; 6 NADPH</p> Signup and view all the answers

What are C3 plants?

<p>A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate.</p> Signup and view all the answers

What is photorespiration?

<p>Reaction in which rubisco attaches oxygen instead of carbon dioxide to ribulose bisphosphate (RuBP).</p> Signup and view all the answers

What are C4 plants?

<p>A plant that prefaces the Calvin cycle with reactions that incorporate CO2 into four-carbon compounds, the end product of which supplies CO2 for the Calvin cycle.</p> Signup and view all the answers

What are CAM plants?

<p>Plants that close their stomata during the day, collect CO2 at night, and store the CO2 in the form of acids until it is needed during the day for photosynthesis.</p> Signup and view all the answers

Plants remove __________ from the atmosphere and return __________ to the atmosphere. The other product(s) of photosynthesis is (are) __________.

<p>carbon dioxide; oxygen; sugars</p> Signup and view all the answers

About __________ % of the products of photosynthesis are used to power cellular respiration and to make organic molecules that the plant cells need. What happens to the rest of the products?

<p>50%; stored or made into cellulose</p> Signup and view all the answers

What is the greenhouse effect?

<p>Warming that results when solar radiation is trapped by the atmosphere.</p> Signup and view all the answers

List the three most important greenhouse gases. What positive effect do these gases exert on Earth's atmosphere?

<p>carbon dioxide, methane, water vapor; insulation</p> Signup and view all the answers

Study Notes

Photosynthesis Overview

  • Photosynthesis transforms sunlight, water, and carbon dioxide into glucose and oxygen.
  • Autotrophs create their own food; photoautotrophs specifically use light for this process.
  • Heterotrophs consume other organisms or organic by-products for energy.

Chloroplasts and Structure

  • Chloroplasts are organelles in plant cells that capture light energy.
  • Major sites of photosynthesis are primarily located in leaves, with most chloroplasts found in mesophyll tissue.
  • Chlorophyll is the key pigment that absorbs light, critical for converting solar energy into chemical energy.

Photosynthesis Reactions

  • The overall equation is 6 CO2 + 6 H2O → C6H12O6 + 6 O2.
  • During photosynthesis, CO2 is reduced to glucose (C6H12O6), and water is oxidized to oxygen (O2).

Light Reactions

  • Occur in the thylakoid membranes of chloroplasts, converting light energy to chemical energy (ATP and NADPH).
  • Water is split during light reactions, providing electrons and releasing O2 as a by-product.
  • The main inputs for light reactions include ADP + P, NADP+, H2O, and light energy; outputs are ATP, NADPH, and O2.

Calvin Cycle

  • The Calvin cycle occurs in the chloroplast stroma and utilizes CO2 and products of light reactions to synthesize sugar.
  • Key steps include carbon fixation, reduction of 3-carbon molecules to G3P, and regeneration of RuBP.
  • Inputs consist of CO2, ATP, and NADPH; outputs include G3P, NADP+, and ADP + P.

Carotenoids and Pigments

  • Chlorophyll A primarily absorbs blue-violet and red light, reflecting green light, while chlorophyll B broadens light absorption range.
  • Carotenoids protect plants from excessive sunlight and broaden the light spectrum usable for photosynthesis.

C3, C4, and CAM Plants

  • C3 plants use the Calvin cycle directly for CO2 incorporation, producing a three-carbon compound.
  • C4 plants initially convert CO2 into four-carbon compounds for later use in the Calvin cycle.
  • CAM plants absorb CO2 at night and store it for use during the day, minimizing water loss.

Importance of Photosynthesis

  • Photosynthesis plays a crucial role in converting atmospheric CO2 into organic compounds and releasing oxygen.
  • Approximately 50% of photosynthesis products are utilized for cellular respiration and organic molecule synthesis; excess is stored as cellulose.

Greenhouse Effect

  • The greenhouse effect is the warming caused by gases like carbon dioxide, methane, and water vapor trapping solar radiation, which provides insulation for the planet.

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Description

Test your knowledge on photosynthesis with this quiz based on Chapter 7 of BIO 20. Learn about the processes and organisms involved in photosynthesis, including autotrophs and heterotrophs. Perfect for reinforcing your understanding of plant biology and energy conversion.

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