Autotrophs and Heterotrophs Quiz

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Questions and Answers

Which of these is NOT a characteristic of autotrophs?

  • They use photosynthesis to produce energy
  • They obtain carbon from inorganic molecules
  • They make their own food
  • They rely on other organisms for food (correct)

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

False (B)

What is the name of the pigment that absorbs light energy during photosynthesis?

Chlorophyll

The process of photosynthesis converts ____ and ____ into sugars and oxygen.

<p>CO2, H2O</p> Signup and view all the answers

Match the following terms with their corresponding descriptions:

<p>Autotroph = An organism that can make its own food from inorganic sources Heterotroph = An organism that obtains food from other organisms Chlorophyll = The green pigment that captures light energy in plants Thylakoid membrane = The inner membrane of a chloroplast where light-dependent reactions take place Stroma = The fluid-like cytoplasm inside a chloroplast where light-independent reactions take place</p> Signup and view all the answers

Which of the following colors of light is most effective in driving photosynthesis?

<p>Blue (B), Red (D)</p> Signup and view all the answers

The light-independent reactions of photosynthesis require light energy to proceed.

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

What is the primary product of the light-dependent reactions of photosynthesis?

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

Longer wavelengths of light have more energy than shorter wavelengths.

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

Which of these is NOT a pigment found in plants?

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

The process by which light energy breaks down a water molecule is called ______.

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

What is the primary function of accessory pigments in photosynthesis?

<p>To maximize the range of wavelengths that photosynthetic cells can absorb.</p> Signup and view all the answers

Match the following pigments with their corresponding colors:

<p>Chlorophyll a = Dark green Chlorophyll b = Light green Xanthophyll = Yellow Anthocyanin = Red and purple Carotenoids = Red, orange, and yellow</p> Signup and view all the answers

Which of the following statements is TRUE about the cyclic pathway of photosynthesis?

<p>It occurs when the noncyclic pathway stalls due to excess light energy. (C)</p> Signup and view all the answers

The Calvin-Benson cycle, also known as the ______ reactions, uses ATP and NADPH to build sugars from CO2.

<p>light-independent</p> Signup and view all the answers

What is the role of Rubisco in the Calvin-Benson cycle?

<p>Rubisco fixes carbon by attaching CO2 to RuBP.</p> Signup and view all the answers

Photorespiration is an efficient process that allows plants to produce sugar even in low CO2 conditions.

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

What is the main sugar produced by plants and transported throughout the plant?

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

Tiny, closable gaps on the surfaces of leaves and stems that allow for gas exchange are called ______.

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

Briefly describe the difference between C3 plants and C4 plants.

<p>C3 plants use only the Calvin cycle to fix carbon, while C4 plants have an additional step using PEP carboxylase to fix carbon, allowing them to better adapt to hot, dry conditions.</p> Signup and view all the answers

What is the primary reason plants lose their green color in the fall?

<p>Chlorophyll degrades faster than other pigments. (B)</p> Signup and view all the answers

The noncyclic pathway of photosynthesis produces ATP, NADPH, and glucose.

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

The electron transfer phosphorylation process uses the energy from electron flow to power ______ production.

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

Why is cyclic photophosphorylation important for photosynthesis? (Mention at least two reasons)

<p>The cyclic pathway helps generate extra ATP when the noncyclic pathway does not produce enough for sugar production. It also allows light-dependent reactions to continue when the noncyclic pathway stalls, for example, when there is excess light energy and PS2 minimizes its electron release to avoid forming harmful free radicals.</p> Signup and view all the answers

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Flashcards

Autotroph

Organisms that make their own food using energy from the environment.

Heterotroph

Organisms that consume other organisms for food and carbon.

Photosynthesis

The process where light energy is converted into chemical energy, producing glucose.

Light-dependent reaction

First stage of photosynthesis where light energy converts into ATP and NADPH.

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Light-independent reaction

Second stage of photosynthesis using ATP and NADPH to synthesize sugars.

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Thylakoid membrane

Inner membrane of chloroplasts where light-dependent reactions occur.

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Stroma

Fluid surrounding thylakoid membranes where light-independent reactions take place.

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Visible light

Electromagnetic radiation that drives photosynthesis, ranging from 380 to 750 nm wavelengths.

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White light

Light that contains all wavelengths visible to the human eye.

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Prism

A transparent object that disperses white light into colors.

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Photon

A packet of light energy that travels in waves.

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Pigment

Molecules that absorb specific wavelengths of light.

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Chlorophyll a

The main photosynthetic pigment in plants that appears green.

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Accessory pigments

Additional pigments that help absorb a wider range of light wavelengths.

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Photolysis

The process where light energy splits water molecules in photosynthesis.

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Noncyclic pathway

A light-dependent pathway that produces ATP and NADPH from light energy.

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Calvin-Benson cycle

Cycle that uses ATP and NADPH to convert CO2 into sugars.

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Photorespiration

A process where Rubisco attaches oxygen instead of CO2, wasting energy.

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Rubisco

An enzyme that fixes carbon during the Calvin cycle.

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Electron transfer phosphorylation

Process where electron flow creates a hydrogen ion gradient to produce ATP.

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Cyclic pathway

A photosynthesis process using only PS1 that produces ATP without NADPH.

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Carotenoids

Accessory pigments that reflect red, orange, and yellow light.

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Stomata

Tiny openings on plant surfaces allowing gas exchange.

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Study Notes

Autotrophs and Heterotrophs

  • Autotrophs produce their own food using energy from the environment (photosynthesis).
  • They obtain carbon from inorganic molecules like carbon dioxide.
  • Photosynthesis converts carbon dioxide and water into glucose using sunlight.
  • Heterotrophs are consumers, obtaining carbon from other organisms.

Photosynthesis Equation

  • CO2 + H2O → sugars + O2

Two Stages of Photosynthesis

  • Light-dependent reactions convert light energy into chemical energy (ATP).
  • Light-independent reactions (Calvin-Benson cycle) use ATP and NADPH to synthesize sugars.

Location of Photosynthesis

  • Thylakoid membrane: site of light-dependent reactions in chloroplasts.
  • Stroma: site of light-independent reactions in chloroplasts.

Visible Light and Photosynthesis

  • Theodor Engelmann's experiments showed that the color of light affects photosynthesis rate.
  • Red and blue light were most effective.
  • Light is electromagnetic radiation; energy is related to wavelength.
  • Shorter wavelengths carry more energy.
  • Pigments absorb specific wavelengths of light.

Photosynthetic Pigments

  • Chlorophyll a: primary pigment, absorbs red and blue, reflects green.
  • Accessory pigments (chlorophyll b, carotenoids, xanthophylls, anthocyanins): broaden the range of absorbed wavelengths.
  • These pigments also give plants their colors and function as antioxidants.
  • Beta-carotene is an example of an accessory pigment in carrots.
  • Pigments are broken down in the winter and recycled.

Light-Dependent Reactions (Noncyclic Pathway)

  • Photosystem II (PSII) absorbs light, releases electrons which enter electron transport chain.
  • Water is split to replace lost electrons, producing oxygen.
  • Electron transfer chain releases energy, creating a proton (H+) gradient across the thylakoid membrane.
  • Electrons are passed to Photosystem I (PSI).
  • PSI absorbs light, releases electrons which are used to reduce NADP+ to NADPH.
  • The H+ gradient drives ATP production through ATP synthase.

Light-Dependent Reactions (Cyclic Pathway)

  • Uses only PSI.
  • Electrons return to PSI to create additional ATP, but not NADPH..
  • Important for generating extra ATP when NADPH production is limited or when light intensity is high.

The Calvin-Benson Cycle

  • The Calvin-Benson cycle is the light-independent reactions of photosynthesis.
  • Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) fixes carbon by attaching CO2 to RuBP.
  • This forms a six-carbon molecule, which splits into 2 PGA molecules (phosphoglycerate).
  • ATP and NADPH are used to convert PGA to PGAL (phosphoglyceraldehyde).
  • 5 PGAL are used to regenerate RuBP.
  • Remaining PGAL are exported to the cytoplasm for carbohydrate production (e.g., sucrose, starch)

Photorespiration

  • Stomata close to conserve water, resulting in increased O2 levels and reduced CO2 levels.
  • Rubisco can add oxygen to RuBP instead of CO2, leading to photorespiration.
  • Photorespiration is less efficient than using CO2 in the Calvin cycle & produces CO2.
  • C3 plants with photorespiration are less efficient in hot conditions.

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