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?

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

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

chloroplasts Signup and view all the answers

What are chemoautotrophs?

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

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

Light, carbon dioxide, and water. Signup and view all the answers

______ are the major sites of photosynthesis in most plants.

Leaves Signup and view all the answers

What is chlorophyll?

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

What is mesophyll?

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

What are stomata?

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

A typical mesophyll cell has about to chloroplasts.

30, 40 Signup and view all the answers

What is stroma?

Fluid portion of the chloroplast; outside of the thylakoids. Signup and view all the answers

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

Membranes, chloroplast Signup and view all the answers

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

stomata; stroma Signup and view all the answers

What are thylakoids?

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

Write the equation for photosynthesis.

6 CO2 + 6 H2O ------> C6H12O6 + 6 O2 Signup and view all the answers

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

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

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

O2 comes from the water, not CO2 Signup and view all the answers

What is the chemical formula for glucose?

C6H12O6 Signup and view all the answers

During photosynthesis CO2 is reduced to ___ as _ and _ are added to it.

Sugar: electrons: hydrogen ions Signup and view all the answers

During photosynthesis water molecules are ______.

Oxidized 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)

from water are transferred to CO2 during photosynthesis Signup and view all the answers

What are the two stages of photosynthesis?

Light reactions and Calvin cycle. 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.

water: electrons: O2 Signup and view all the answers

____ _ is used to drive the transfer of ___ and _ from water to the electron acceptor , reducing it to _.

Light energy: electrons: H+: NADP+: NADPH Signup and view all the answers

What does NADPH temporarily store?

Electrons and hydrogen ions. 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?

The incorporation of carbon into organic compounds. Signup and view all the answers

__ provides the _ for reducing _____ compounds in the Calvin cycle.

NADPH: electrons: carbon 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 .

O2, ATP, NADPH; sugar, ADP, NADP+ Signup and view all the answers

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

electrons from water and energy from sunlight Signup and view all the answers

What is wavelength?

The distance between the crests of electromagnetic waves. Signup and view all the answers

What is the electromagnetic spectrum?

The full range of frequencies of electromagnetic waves. Signup and view all the answers

What is chlorophyll A?

A photosynthetic pigment that participates directly in the light reactions, absorbs mainly blue-violet and red light. Mainly reflects green. 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?

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

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

protect cells from excess sunlight Signup and view all the answers

What is a photosystem?

A light-harvesting complex in the chloroplast thylakoid composed of pigments and proteins. 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.

two photosystems; electron transport chain; light; chemical Signup and view all the answers

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

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

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

2: 2: 1 Signup and view all the answers

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

NADP+ Signup and view all the answers

What is photophosphorylation?

The production of ATP by chemiosmosis during the light reactions of photosynthesis. 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 __.

NADPH; H+; ATP 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.

6: 18: 12 Signup and view all the answers

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

reduction, step 2 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?

9 ATP; 6 NADPH Signup and view all the answers

What are C3 plants?

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. Signup and view all the answers

What is photorespiration?

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

What are C4 plants?

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. Signup and view all the answers

What are CAM plants?

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. Signup and view all the answers

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

carbon dioxide; oxygen; sugars 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?

50%; stored or made into cellulose Signup and view all the answers

What is the greenhouse effect?

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

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

carbon dioxide, methane, water vapor; insulation 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.