Photosynthesis Light Reactions & Calvin Cycle
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Questions and Answers

What is the purpose of the light reaction?

Turn light into NADPH and ATP.

What is the purpose of the Calvin Cycle?

To produce glucose, CO2, and energy from ATP and NADPH.

Where does the Calvin Cycle take place?

Stroma.

Where does the light reaction take place?

<p>Thylakoid membrane.</p> Signup and view all the answers

Is light necessary for the light reaction?

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

Is light necessary for the Calvin Cycle?

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

What molecules are needed for the light reaction?

<p>Light protons, NADP+, and ADP.</p> Signup and view all the answers

What molecules are needed for the Calvin Cycle?

<p>NADPH, ATP, CO2, and RuBP.</p> Signup and view all the answers

What is the NADPH/NADP+ relationship for the light reaction?

<p>NADP+ for the Calvin Cycle turns into NADPH.</p> Signup and view all the answers

What is the NADPH/NADP+ relationship for the Calvin Cycle?

<p>NADPH is used and turned into NADP+.</p> Signup and view all the answers

What is the ATP/ADP relationship for the Calvin Cycle?

<p>ATP is used and turned into ADP.</p> Signup and view all the answers

What is the ATP/ADP relationship for the light reaction?

<p>ADP from the Calvin Cycle is turned into ATP.</p> Signup and view all the answers

What are all products of the light reaction?

<p>ATP, NADPH, and O2 as a byproduct.</p> Signup and view all the answers

What are all products of the Calvin Cycle?

<p>ADP, NADP+, and glucose.</p> Signup and view all the answers

Describe the energy made and used in the light reaction.

<p>Light energy is used; ATP is made.</p> Signup and view all the answers

Describe the energy made and used in the Calvin Cycle.

<p>ATP is used; glucose is made.</p> Signup and view all the answers

What enzyme is needed for the light reaction?

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

What enzyme is needed for the Calvin Cycle?

<p>Ribisco.</p> Signup and view all the answers

What is another name for the Calvin Cycle and why is this misleading?

<p>Light-independent reaction; it still uses the material of the light reaction but no light is needed.</p> Signup and view all the answers

What is the function of CO2 in the Calvin Cycle?

<p>Used for ribisco carbon fixation.</p> Signup and view all the answers

What happens when CO2 enters the cell?

<p>Used in carbon fixation; ribisco active site forms unstable 6-carbon molecules.</p> Signup and view all the answers

What is ribisco?

<p>The enzyme reaction active site.</p> Signup and view all the answers

What is the name of the 3-carbon molecule formed?

<p>3PGA is turned into PGAL.</p> Signup and view all the answers

How are NADPH and ATP used?

<p>ATP provides energy; NADPH provides electrons.</p> Signup and view all the answers

How many turns of the Calvin Cycle must occur to make one molecule of glucose and why?

<p>Six; because glucose needs to be energized and sustainable.</p> Signup and view all the answers

What is the purpose of the light reaction of photosynthesis?

<p>The light reaction generates O2, ATP, and NADPH.</p> Signup and view all the answers

What does the chloroplast use the sun's energy for?

<p>To excite the electrons and split H2O.</p> Signup and view all the answers

Where do the electrons go at the end of the electron transport chain?

<p>Electrons are gained by NADPH.</p> Signup and view all the answers

From where does the light reaction get more electrons?

<p>From H2O.</p> Signup and view all the answers

What is given off as a waste product?

<p>O2.</p> Signup and view all the answers

What happens to the leftover hydrogen atoms?

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

From where does the cell get the energy to add the third phosphate group onto ADP?

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

What are the products of the light reactions?

<p>NADPH, O2 byproduct, ATP energy for glucose.</p> Signup and view all the answers

What are autotrophs?

<p>Organisms that self-create food.</p> Signup and view all the answers

What are heterotrophs?

<p>Organisms that eat other living things.</p> Signup and view all the answers

What are photoautotrophs?

<p>Organisms that use photosynthesis.</p> Signup and view all the answers

What are the structures of chloroplasts?

<p>Thylakoid stacks, thylakoid membrane, stroma, surrounds chlorophyll.</p> Signup and view all the answers

What are the functions of the stomata?

<p>To release H2O, to release oxygen, to take in CO2.</p> Signup and view all the answers

Why are most of the stomata on the bottom of the leaf?

<p>To protect it and stop water evaporation.</p> Signup and view all the answers

Why are the epidermis layers packed so tightly together?

<p>To provide protection and reduce water loss.</p> Signup and view all the answers

Study Notes

Light Reactions

  • Purpose is to convert light energy into chemical energy forms, specifically NADPH and ATP.
  • Occur in the thylakoid membrane of chloroplasts.
  • Light is crucial for splitting water (H2O) molecules and exciting electrons.
  • Primary reactants include light protons, NADP+, and ADP.
  • Products generated include ATP, NADPH, and oxygen (O2) as a byproduct.
  • Electrons from H2O move through the electron transport chain and ultimately contribute to NADPH formation.
  • Light energy excites electrons and helps form ATP by adding a phosphate group to ADP through hydrogen ions.

Calvin Cycle

  • Purpose is to synthesize glucose using CO2 and energy from ATP and NADPH, also called light-independent reactions, although it relies on products from light reactions.
  • Takes place in the stroma of chloroplasts.
  • Key reactants include NADPH, ATP, CO2, and RuBP.
  • Carbon fixation occurs when CO2 combines with RuBP, facilitated by the enzyme RuBisCO.
  • 3-carbon molecule 3PGA is generated, which is converted into PGAL.
  • Each glucose molecule requires six turns of the cycle to ensure adequate energy and sustainability.
  • ATP provides energy while NADPH supplies electrons during the process.
  • Final products include ADP, NADP+, and glucose.

Enzymes and Energy Relationships

  • Light reactions utilize ATP synthase to convert ADP to ATP.
  • Calvin Cycle relies on RuBisCO for carbon fixation, converting ATP to ADP in the process.
  • NADP+ is reduced to NADPH during light reactions, whereas NADPH is oxidized back to NADP+ in the Calvin Cycle.

Autotrophs and Heterotrophs

  • Autotrophs create food autonomously, primarily through photosynthesis.
  • Heterotrophs obtain energy by consuming other organisms.
  • Photoautotrophs specifically utilize light to create organic substances.

Chloroplast Structures

  • Composed of thylakoid stacks (membrane) surrounded by stroma which contains chlorophyll, responsible for capturing light energy.

Stomata Functions

  • Stomata control gas exchange; they release water vapor and oxygen while taking in carbon dioxide (CO2).
  • Most stomata are located on the underside of leaves to reduce water evaporation and provide protection.
  • Epidermis layer is tightly packed to enhance structural integrity and limit water loss.

Waste Products and Byproducts

  • Oxygen is released as a waste product from light reactions.
  • Leftover hydrogen is used in ATP formation during light reactions.

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Description

Explore the processes of light reactions and the Calvin cycle in photosynthesis. This quiz covers the conversion of light energy to chemical energy, the role of chloroplasts, and the importance of key reactants and products. Test your understanding of how glucose is synthesized using ATP, NADPH, and CO2.

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