Autotrophs and Heterotrophs Quiz

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Questions and Answers

What is the primary source of carbon for autotrophs?

  • Photosynthesizers
  • Inorganic molecules (correct)
  • Sunlight
  • Organic molecules

Heterotrophs are able to produce their own food through photosynthesis.

False (B)

What is the name of the process by which autotrophs convert light energy into chemical energy?

Photosynthesis

The two stages of photosynthesis are the ______ reaction and the ______ reaction.

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

Match the following terms with their corresponding definitions:

<p>ATP = A high-energy molecule used to power cellular processes NADPH = An electron carrier involved in photosynthesis Thylakoid membrane = The location of the light-dependent reactions in chloroplasts Stroma = The fluid-filled space within chloroplasts where the light-independent reactions occur</p> Signup and view all the answers

Which of the following is NOT a characteristic of photons?

<p>Their wavelength and energy are inversely related. (D)</p> Signup and view all the answers

Pigments absorb all wavelengths of light equally.

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

What is the primary photosynthetic pigment in plants, cyanobacteria, and photosynthetic protists?

<p>Chlorophyll a</p> Signup and view all the answers

The accessory pigment, ______, gives carrots their orange color.

<p>beta-carotene</p> Signup and view all the answers

Match the accessory pigments with their corresponding reflected colors:

<p>Xanthophyll = Yellow Anthocyanin = Red and purple Carotenoids = Red, orange, and yellow</p> Signup and view all the answers

What is the primary reason that leaves turn yellow or orange in the fall?

<p>Breakdown of chlorophyll and slower recycling of accessory pigments. (D)</p> Signup and view all the answers

The noncyclic pathway of photosynthesis produces ATP, NADPH, and carbon dioxide.

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

What is the process called where light energy breaks down water molecules during photosynthesis?

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

The electron transfer chain in the thylakoid membrane is responsible for generating a ______ gradient.

<p>hydrogen ion</p> Signup and view all the answers

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

<p>It is used to generate extra ATP when the noncyclic pathway stalls. (C)</p> Signup and view all the answers

The Calvin-Benson cycle is also known as the light-dependent reactions of photosynthesis.

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

What is the name of the enzyme that fixes carbon dioxide to RuBP in the Calvin-Benson cycle?

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

The first stable intermediate formed in the Calvin-Benson cycle is a ______ -carbon compound.

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

Which of the following is NOT a consequence of photorespiration?

<p>Increased efficiency of photosynthesis. (A)</p> Signup and view all the answers

C3 plants are adapted to minimize photorespiration.

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

What is the name of the tiny gaps on the surfaces of leaves and stems that allow for gas exchange?

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

Flashcards

Autotroph

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

Heterotroph

Organisms that consume other organisms for food and energy.

Photosynthesis

The process where light energy creates glucose from carbon dioxide and water.

Light-dependent reactions

Reactions in photosynthesis that convert light energy into chemical energy (ATP).

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Light-independent reactions

Reactions that synthesize glucose using ATP and NADPH from previous reactions.

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Thylakoid membrane

The site in chloroplasts where light-dependent reactions occur.

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Stroma

The fluid outside thylakoids where light-independent reactions occur.

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Wavelength

The distance between two consecutive peaks of waves; measured in nanometers.

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White light

Light that contains all wavelengths of visible light, appearing colorless.

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Prism

A transparent object that bends light, separating it into different colors.

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Photon

A discrete packet of light energy; its energy relates to its wavelength.

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Pigment

Molecules that absorb specific wavelengths of light and reflect others, giving color.

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Chlorophyll a

The primary pigment in plants that absorbs mainly red and blue light, reflecting green.

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Accessory pigments

Pigments other than chlorophyll a that absorb different wavelengths of light.

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Carotenoids

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

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Photosystem

Large protein complexes in thylakoid membranes that convert light energy to chemical energy.

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Noncyclic pathway

A light-dependent pathway producing ATP, NADPH, and O2 using both PS2 and PS1.

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Photolysis

The process of breaking down water molecules by light energy to release O2.

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Calvin-Benson Cycle

A light-independent cycle that uses ATP and NADPH to fix CO2 into sugars.

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Photorespiration

A process where Rubisco attaches O2 instead of CO2, reducing sugar efficiency.

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Stomata

Tiny openings in leaves that allow for gas exchange but can close to conserve water.

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Rubisco

An enzyme that facilitates the fixation of carbon dioxide in the Calvin Cycle.

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ATP synthase

Enzyme that synthesizes ATP using hydrogen ion gradients from light reactions.

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Study Notes

Autotrophs and Heterotrophs

  • Autotrophs produce their own food through photosynthesis, obtaining energy and carbon from inorganic sources like carbon dioxide.
  • Photosynthesis converts light energy into chemical energy, using carbon dioxide and water to create glucose and releasing oxygen.
  • Heterotrophs are consumers, obtaining carbon from other organisms (autotrophs).

Two Stages of Photosynthesis

  • Photosynthesis equation: CO2 + H2O → sugars + O2
  • Light-dependent reactions convert light energy to chemical energy (ATP), creating ATP and NADPH.
  • Light-independent reactions (Calvin cycle) use ATP and NADPH to synthesize sugars.

Photosynthesis Location

  • Thylakoid membrane: Inner membrane of chloroplast, site of light-dependent reactions.
  • Stroma: Fluid surrounding thylakoid membrane, site of light-independent reactions.

Visible Light and Photosynthesis

  • Theodor Engelmann's experiments demonstrated that different wavelengths of light affect photosynthesis rates, with red and blue light being most effective.
  • Visible light wavelengths range from 380 to 750 nm.
  • Photon: Packets of light energy (energy is inversely proportional to wavelength).
  • Pigment: Molecules that absorb specific wavelengths of light.

Photosynthetic Pigments

  • Chlorophyll a: Primary pigment, absorbs red and blue light, reflects green.
  • Accessory pigments (e.g., chlorophyll b, carotenoids, xanthophylls, anthocyanins) broaden the range of absorbed light wavelengths.
  • Accessory pigments provide color to plants and act as antioxidants.
  • Plants conserve resources in winter, causing leaves to change color as chlorophyll is recycled and other pigments become more visible.

Light-Dependent Reactions (Noncyclic and Cyclic Pathways)

  • Photosystem (PS): Protein complexes containing pigments that convert light energy to chemical energy.
  • Noncyclic pathway: Primary pathway in plants, producing ATP, NADPH, and oxygen (O2).
    • Photolysis: Water is split to provide electrons to PS2.
    • Electron transfer chain creates a hydrogen ion gradient.
    • ATP synthase uses the gradient to produce ATP.
    • NADP+ is reduced to NADPH.
  • Cyclic pathway: Uses PS1 to produce additional ATP when needed.
    • Does not produce NADPH or O2.
    • Important for generating extra ATP when light-dependent reactions are overtaxed.

Calvin-Benson Cycle

  • Light-independent reactions.
  • Rubisco fixes CO2 to RuBP, creating a 6-carbon molecule which splits to form 3PGA.
  • ATP and NADPH provide energy and electrons to convert 3PGA to PGAL.
  • PGAL is used to synthesize sugars (sucrose, starch) and regenerate RuBP.

Photorespiration in C3 plants

  • Stomata close to conserve water, reducing CO2 intake and increasing O2 concentration.
  • Rubisco binds O2 instead of CO2, leading to photorespiration (ATP/energy loss).
  • C3 plants compensate for photorespiration by producing large amounts of Rubisco.

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