Photosynthesis
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UofC BIOL211 Topic 6: Photosynthesis
106 Terms
What is photosynthesis
The process of converting light energy into chemical energy
What is the main purpose of photosynthesis
Produce energy
Which organisms perform photosynthesis
Plants, algae, and certain bacteria
Where does photosynthesis occur in plants
Chloroplasts
What is the main energy source for photosynthesis
Sunlight
What is the main carbon source for photosynthesis
Carbon dioxide
What gas is released during oxygenic photosynthesis
Oxygen
What molecule is produced during photosynthesis that stores chemical energy
Sugar
What is the overall purpose of the light reactions
Convert light energy into ATP and NADPH
What is the overall purpose of the Calvin cycle
Use CO₂ to produce carbohydrate precursors
What are the two major stages of photosynthesis
Light reactions and the Calvin cycle
What is the relationship between photosynthesis and cellular respiration
Their overall chemical processes are complementary
What is the overall equation for photosynthesis
6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂
Where does the oxygen released by photosynthesis come from
Water
What happens to carbon dioxide during photosynthesis
It is reduced and incorporated into organic molecules
Where do the light reactions occur
Thylakoid membranes
Where does the Calvin cycle occur
Stroma
What is a chloroplast
The organelle where photosynthesis occurs
What is a thylakoid
A flattened membrane
What is a granum
A stack of thylakoids
What are grana
Multiple stacks of thylakoids
What is the stroma
The fluid
What is the thylakoid membrane
The membrane containing photosystems and electron transport proteins
What is the thylakoid lumen
The space inside a thylakoid
Where do protons accumulate during the light reactions
In the thylakoid lumen
Where is ATP produced during the light reactions
At ATP synthase in the thylakoid membrane
Where does the Calvin cycle obtain ATP and NADPH
From the light reactions
What is light
Electromagnetic radiation
What is a photon
A discrete packet of light energy
What is wavelength
The distance between successive wave peaks
What is the electromagnetic spectrum
The full range of electromagnetic radiation
What is visible light
The portion of the electromagnetic spectrum detectable by human eyes
What is the relationship between wavelength and energy
Shorter wavelengths have higher energy
What is the relationship between frequency and energy
Higher frequency means higher energy
What is the approximate visible light range
About 400–700 nm
What is violet light
Visible light with a relatively short wavelength
What is red light
Visible light with a relatively long wavelength
What is the function of light in photosynthesis
Excite electrons in pigments
What happens when a pigment absorbs a photon
An electron is excited to a higher energy level
What is a pigment
A molecule that absorbs particular wavelengths of light
What is the main photosynthetic pigment in plants
Chlorophyll a
What is chlorophyll
A pigment that absorbs light energy
What is chlorophyll a
The primary reaction
What is chlorophyll b
An accessory pigment that broadens light absorption
What are accessory pigments
Pigments that capture light and transfer energy to chlorophyll a
What is a carotenoid
An accessory pigment that absorbs light and helps protect against excess light
Why do plants have different pigments
To absorb a wider range of wavelengths
What gives leaves their green appearance
Green light is reflected or transmitted more than strongly absorbed wavelengths
What is an absorption spectrum
A graph showing how strongly a pigment absorbs different wavelengths
What is an action spectrum
A graph showing the effectiveness of different wavelengths in driving photosynthesis
What is the difference between an absorption spectrum and an action spectrum
Absorption measures light absorbed; action measures photosynthetic effectiveness
Which wavelengths do chlorophylls generally absorb strongly
Blue and red light
Which wavelengths are generally less absorbed by chlorophyll
Green wavelengths
What is a photosystem
A pigment
What are the two photosystems in oxygenic photosynthesis
Photosystem II and Photosystem I
What is the reaction center
The region where excited electrons are transferred to an electron acceptor
What is the primary electron acceptor
A molecule that receives an excited electron
What is the light
harvesting complex
What is resonance energy transfer
Transfer of excitation energy between pigment molecules
What is the reaction
center chlorophyll
What is Photosystem II's reaction
center chlorophyll
What is Photosystem I's reaction
center chlorophyll
What does P680 refer to
The reaction center of Photosystem II
What does P700 refer to
The reaction center of Photosystem I
What is the main function of Photosystem II
Use light energy to drive electron transfer and water oxidation
What is the main function of Photosystem I
Use light energy to re
Where do the light reactions occur
Thylakoid membranes
What are the main products of the light reactions
ATP, NADPH, and oxygen
What molecule supplies electrons to Photosystem II
Water
What happens during photolysis of water
Water is split using light
What are the products of water splitting
Electrons, protons, and oxygen
Why is water split
To replace electrons lost by Photosystem II
Where does the oxygen released during photosynthesis originate
From water molecules
What happens to electrons in Photosystem II
Light excites them to a higher energy level
What happens to electrons after leaving Photosystem II
They pass through an electron transport chain
What is the role of the photosynthetic electron transport chain
Transfer electrons and help establish a proton gradient
What powers proton movement into the thylakoid lumen
Energy from electron transfer and associated proton
What is the purpose of the thylakoid proton gradient
Drive ATP synthesis
What is photophosphorylation
ATP production powered by light
What is the role of ATP synthase in chloroplasts
Produce ATP using proton flow
Which direction do protons flow through chloroplast ATP synthase
From the thylakoid lumen into the stroma
What happens to electrons in Photosystem I
Light excites them again
What is the final electron acceptor in linear electron flow
NADP+
What does NADP+ become when reduced
NADPH
What enzyme helps produce NADPH
Ferredoxin
What is the role of NADPH
Carry high
What is the role of ATP in the Calvin cycle
Provide energy
What is the role of NADPH in the Calvin cycle
Provide reducing power
What is linear electron flow
Electron movement from water through both photosystems to NADP+
Which photosystem acts first in linear electron flow
Photosystem II
Which photosystem acts second in linear electron flow
Photosystem I
What is the original electron source
Water
What is the final electron acceptor
NADP+
What are the main products of linear electron flow
ATP, NADPH, and oxygen
What happens to water during linear electron flow
It is oxidized
What happens to NADP+ during linear electron flow
It is reduced to NADPH
Why is linear electron flow important
It provides ATP and NADPH for the Calvin cycle
What is cyclic electron flow
Electron flow involving Photosystem I that returns electrons to the electron transport pathway
Which photosystem is involved in cyclic electron flow
Photosystem I
What is the main product of cyclic electron flow
ATP