Chapter 8

_______ is the process that converts solar energy into chemical energy within chloroplasts.

photosynthesis

_____ are self-feeders that sustain themselves without eating anything derived from other organisms.

_____ produce organic molecules from CO2

autotrophs, producers

Leaves appear green because chlorophyll is poor at ?

absorbing green wavelengths

Leaves efficiently absorb light across most of the?

visible spectrum

Chlorophyll pigments are embedded in the _____ and are integral to light absorption.

thylakoid membrane

3 examples of accessory pigments

carotenoids, xanthophylls anthocyanins

________ absorb light from regions of the visible spectrum that are poorly absorbed by chlorophyll.

accessory pigments

A _____ consists of light-harvesting complexes that surround a reaction center complex.

Photosystem

Pigment molecules bound to proteins in photosystems are called?

light-harvesting complexes

Light-harvesting complexes transfer the energy of photons to the?

reaction center

The reaction center complex of a photosystem contains a special pair of _____ molecules

Transfers an excited electron a ?

chlorophyll a molecules

primary electron acceptor

Absorption of light by chlorophyll:

Light energy absorbed by Chlorophyll in solution is released as ___ and ____.

heat and fluorescence

Absorption of light by chlorophyll:

Light energy absorbed by chlorophyll in the photosystem of a plant cell can be transferred to an ______ chlorophyll?

adjacent chlorophyll

The special arrangement of chlorophyll molecules allows energy to be passed from the ______ chlorophylls to the _____.

antenna, reaction center

Outputs of light reactions:

inputs:

Solar energy (light)

H2O → ?

NADP+ —> ?

ADP —> ?

O2, NADPH, ATP

2 possible routes for electron flow during light reactions — Linear electron flow:

Involves both PS __ and ___.

Uses ____ energy.

Produces what 3 things?

I and II

light

O2, ATP, NADPH

2 possible routes for electron flow during light reactions — Cyclic electron flow:’

Involves only PS __.

Produces only _____.

Doesn’t produce what two things?

I, ATP, O2, NADPH

This is step ___ of the linear electron flow:

A photon hits a pigment in the light-harvesting complex of PS II and its energy is passed among pigment molecules until it reaches P680

1

Step 1 of LEF: A photon hits a pigment in the light-harvesting complex of PS __ and its energy is passed among pigment molecules until it reaches ___.

II, P680

This is step ___ of LEF:

An excited electron from P680 is transferred to the primary electron acceptor (we now refer to is as P680+)

2

Step 2 of LEF: An excited electron from P680 is transferred to the _____ (we now refer to is as P680+

primary electron acceptor

This is step ___ of LEF:

an enzyme catalyzes the split of H2O into 2 e-, 2 H+, and an O atom;
• 2 e- are transferred to the P680+ pair, reducing it back to P680
• 2 H+ are released into the thylakoid space
• O atom combines with another O atom to form O2

3

Step 3 of LEF:

an enzyme catalyzes the split of H2O into __, __, and an O atom;
• 2 __ are transferred to the P680+ pair, reducing it back to P680
• 2 __ are released into the thylakoid space
• O atom combines with another O atom to form __.

2 e-, 2 H+,

electrons

protons

O2

This is step ___ of LEF:

Electrons are passed in series of redox reactions from the primary electron acceptor of PS II down an ETC to PS I;
• ETC includes electron carrier plastoquinone (Pq), a cytochrome complex, and a protein called pastocyanin (Pc)
• Energy released by electron transfer is used to pump H+ into the thylakoid space, creating a protein gradient across the thylakoid
membrane

4

Step 4 of LEF:

Electrons are passed in series of redox reactions from the primary electron acceptor of PS __ down an ETC to PS __;
• ETC includes electron carrier ____ (Pq), a cytochrome complex, and a protein called ____ (Pc)
• Energy released by electron transfer is used to pump ____ into the thylakoid space, creating a protein gradient across the ____
membrane

II, I

plastoquinone, pastocyanin

H+, thylakoid

This is step ___ of LEF:

Potential energy stored in the proton gradients drives the production of ATP by chemiosmosis

5

Step 5 of LEF:

Potential energy stored in the proton gradient drives the production of ATP by?

Chemiosmosis

This is step ___ of LEF:

In PS I (like PS II), transferred light energy excites P700, which loses an electron to the primary electron acceptor
• P700+ (P700 that is missing an e-) accepts an e- passed down from PS II via the ETC

6

Step 6 of LEF:

In PS I (like PS II), transferred light energy excites P___, which loses an electron to the primary electron acceptor
• P700+ (P700 that is missing an e-) accepts an e- passed down from PS ___ via the ETC

P700, II

This is step ___ of LEF:

Electrons are passed down from the primary electron acceptor of PS I down a second ETC to the protein ferredoxin (Fd)
• There is no proton gradient or ATP produced by this ETC

7

Step 7 of LEF:

Electrons are passed down from the primary electron acceptor of PS I down a second ETC to the protein ferredoxin (Fd)
• There is no ____ or ____produced by this ETC

proton gradient, ATP

This is step __ of LEF:

The enzyme ____ catalyzes the transfer of e- from Fd to NADP+
• __ e- are needed to reduce NADP+ to NADPH
• e- of NADPH are at a ___ energy level than they were in H2O, so are more readily available for the reaction of the Calvin Cycle
• The formation of NADPH also removes a H+ from the ____.

NADP+ reductase

2

higher

stroma

The first stage in the production of ATP via the oxidation of glucose molecules is referred to as?

glycolysis

The oxidation of pyruvate occurs in the?

mitochondrial matrix

Protons in the mitochondrion flow through an ATP synthase from the ? to the?

intermembrane space to the matrix

The energy required to drive the synthesis of the majority of the ATP generate during aerobic respiration comes most directly from the flow of protons through an _____ complex.

ATP synthase complex

The terminal acceptor of a mitochondrial electron transport chain is?

oxygen

Light energy is converted to chemical energy in the?

thykaloid

The terminal electron acceptor of a photosynthetic electron transport chain is?

NADP+

The enzyme called rubisco connects a __- carbon molecule to __- carbon molecule

1, 5

The primary source of high-energy electrons in the Calvin cycle is?

NADPH

In Cyclic Electron Flow, photoexcited electrons cycle back from the ____ to the _____ complex instead of being transferred to NADP+.

Fd (ferredoxin), cytochrome

In Cyclic Electron Flow, electrons are passed to a P____ chlorophyll in the PS reaction center via the ___ molecule.

P700, PS1, plastocyanin (Pc)

Cyclic electron flow uses only PS ?

PS I

Cyclic electron flow produces ____, but no _____ or ____ results form this process.

ATP, NADPH, oxygen

In CEF, several groups of _____ bacteria have only a single PS related to either PS I or PS II.

photosynthetic

For photosynthetic bacteria, _____ electron flow is the only means of generating ATP during photosynthesis.

cyclic

For photosynthetic bacteria, photosynthesis may have first evolved in the ______ of these bacteria in a form similar to cyclic electron flow.

ancestors

Cyclic electron flow is probably, in part, an “_______ leftover” in organisms with both photosystems.

evolutionary

Cyclic electron flow may have some photoprotective capability; plants that do not have it grow well in light, but cannot grow well in _____ light.

intense

Mitochondria and chloroplasts generate ATP by the same ______ mechanism.

However, they use different energy sources to do so. Mitochondria transfer _____ energy into ATP while chloroplasts transfer _____ energy into ATP.

chemiosmosis

food energy, solar energy

Calvin cycle outputs.

ATP —> ?

NADPH —→

CO₂ —→ ?

ADP, NAD+, G3P sugar

Calvin cycle inputs:

? —→ ADP

? ——> NADP+

? ——> G3P (glyceraldehyde-3-phosphate) sugar

ATP, NADPH, CO2

The calvin cycle:

Carbon enters the cycle as ___ and leaves as a sugar called ?

To synthesize 1 G3P, the cycle must turn ___ times by fixing 3 molecules of ___.

CO2, G3P

3, CO2

The calvin cycle occurs in the _____ and consists of 3 phases: ____, ____, and ____.

stroma, carbon fixation, reduction, regeneration of the CO2 acceptor

Phase 1 of the Calvin cycle — carbon fixation:

Inputs:

_____ enzyme

how many CO2, how many RuBP. This is the “CO2 ____”

Outout:

____ 6-carbon intermediates, splits into ?

rubisco, 3 CO2, 3 ribulose bisphosphate (RuBP), acceptor

3, 6 molecules 3-phosphoglycerate

Phase 2 of the Calvin cycle —- Reduction:

Inputs (3)?

6 × 3-phosphoglycerate

6 x ATP

6 NADPH

Phase 2 of the Calvin cycle —- Reduction:

outputs (6)?

how many G3P exit the cycle? This makes how much glucose?

6 × 1,3-bisphosphoglycerate

6 x ADP

6 x NADP +

6 x P_i

6 G3P

1 G3P exits the CC, make ½ glucose

The Calvin cycle phase 3 —— Regeneration of RuBP:

inputs? (2)

5 x G3P

3 x ATP

The Calvin cycle phase 3 —— Regeneration of RuBP:

outputs? (3)

3 x ADP

2 x P_i

3 x RuBP

How many CO2, ATP, and NADPH are needed to make 1 G3P?

3 CO2, 6 ATP, 6 NADPH

Glucose has 6 carbons. How many of the following are needed to make 1 glucose: CO2, G3P, # turns of calvin cycle?

6 CO2, 2 G3P, 6 turns of the calvin cycle

Starch granules in a chloroplast:

Any excess carbohydrates that are produced in the calvin cycle are converted to ____ and stored.

• Can be used the ____ in the absence of light.

starch, night

2 Major photosyntheic challenges:

1) Excess ____ energy can damage the cell.

2) Rubisco can either catalyze ____ or ____ to RuBP.

CO2, O2

Photorespiration occurs when rubisco adds ____ instead of ____ to RuBP.

Consumes ___, releases ____.

O2, CO2

ATP, CO2

Review of photosynthesis:

Light reactions:

carried out by molecules in the ?

Convert light energy to the chemical energy of ____ and ____.

Split ____ and release ___.

Calvin cycle reactions:

Take place in the _____

Uses ATP and NADPH to convert ____ to the sugar ____.

Return what 3 things to the light reactions?

thykaloid membranes, ATP and NADPH, split H2O and release O2

stroma, CO2, G3P, returns ADP, inorganic phosphate (Pi) and NADP+ to the light reactions.