Deck 25: Photosynthesis Nitrogen

Question 1

In chloroplasts

A) water is oxidized and NAD is reduced
B) water is reduced and NADP is oxidized
C) water is split and NADP is reduced
D) water is split and NAD is oxidized
E) water is produced and NADPH is oxidized

Answer 1

water is split and NADP is reduced

Question 2

Which is true about the differences between chloroplasts and mitochondria?

A) Both have electron transport systems embedded in their inner membranes.
B) Both serve as the only source of ATP for the cell.
C) Both use electron transport systems to pump protons (H+) into the lumen/matrix.
D) Both use proton (H+) gradients to energize ATP synthesis via similar ATP synthases.
E) Both release ATP to their inner regions (lumen or matrix).

Answer 2

Both use proton (H+) gradients to energize ATP synthesis via similar ATP synthases.

Question 3

What were the first organisms that had the ability to oxidize water to oxygen?

A) flowering plants
B) green sulfur bacteria
C) cyanobacteria
D) ferns
E) green plants

Answer 3

cyanobacteria

Question 4

The light reactions of photosynthesis occur in the _____ membrane of the chloroplast.

Question 5

Light-harvesting antennas gather photons and pass the energy to the ______.

A) reaction center
B) thylakoid
C) plastid
D) stroma
E) matrix

Question 6

The electron pathway from water to NADP⁺, referred to as the ____, allows two loci for photochemical events.

Question 7

______ carries electrons between PSII and PSI.

A) plastoquinone
B) carotene
C) NAD+
D) NADP+
E) ATP synthase

Question 8

PSII oxidizes ____.

Question 9

Electron transport through the cytochrome b₆f complex generates a(n) _____ gradient.

A) proton
B) H+
C) redox
D) light energy
E) Both A and B are correct

Question 10

During photosynthetic electron transport, protons are pumped from the ___ to the ___.

Question 11

The chloroplast ATP synthase move protons from ___ with release of ATP into the ___.

Question 12

Which of the following can happen when a photosynthetic pigment absorbs light?

A) energy lost as heat
B) energy given off by fluorescence
C) exciton transfer
D) photooxidation
E) all of the above

Question 13

Plastoquinone is similar to mitochondrial ubiquinone in that

A) Both are mobile carriers
B) Both go through a semiquinone redox state
C) Both carry two electrons
D) Both release one electron at a time to the next electron carrier in a Q cycle
E) All of the above are correct

Question 14

Plastocyanin has an important

A) water-splitting enzyme
B) quinone structure
C) Cu ion
D) heme structure
E) pigment

Question 15

Complete the following reaction: P680 + light $\rightarrow$ _____ $\rightarrow$ _____

A) P680*; P680^- + H⁺
B) P680*; P680⁺ + e^-
C) P680^-; P680*
D) P680⁺; P680*
E) none of the above

Question 16

Electrons are transferred from P680 to _____, then to cytochrome b₆f.

A) ubiquinone
B) plastoquinone
C) plastocyanin
D) P700
E) NADP⁺

Question 17

During the oxidation of water, where do the protons go?

A) thylakoid lumen
B) stroma
C) space between inner and outer chloroplast membrane
D) cytosol
E) protons are not released but transferred to proteins for metabolic use

Question 18

Cytochrome b₆f is most similar to mitochondrial _____ with the exception that electrons are passed to _____, not to cytochrome

A) complex I; plastocyanin
B) complex I; plastoquinone
C) complex III; plastocyanin
D) complex III; plastoquinone
E) none of the mitochondrial complexes are similar to cytochrome b₆f

Question 19

The active group of photosystem I is known as _____.

A) P800
B) P700
C) P660
D) P650
E) P450

Question 20

Which of the following shows the correct movement of electrons in the Z-scheme of photosynthesis?

A) H₂O $\rightarrow$ P700 $\rightarrow$ plastoquinone $\rightarrow$ cytochrome b₆f $\rightarrow$ plastocyanin $\rightarrow$ P680 $\rightarrow$ ferredoxin $\rightarrow$ NADP⁺
B) H₂O $\rightarrow$ P680 $\rightarrow$ plastocyanin $\rightarrow$ cytochrome b₆f $\rightarrow$ plastoquinone $\rightarrow$ P700 $\rightarrow$ ferredoxin $\rightarrow$ NADP⁺
C) H₂O $\rightarrow$ P680 $\rightarrow$ plastoquinone $\rightarrow$ ferredoxin $\rightarrow$ plastocyanin $\rightarrow$ P700 $\rightarrow$ cytochrome b₆f $\rightarrow$ NADP⁺
D) H₂O $\rightarrow$ P680 $\rightarrow$ plastoquinone $\rightarrow$ cytochrome b₆f $\rightarrow$ plastocyanin $\rightarrow$ P700 $\rightarrow$ ferredoxin $\rightarrow$ NADP⁺
E) H₂O $\rightarrow$ P680 $\rightarrow$ ferredoxin $\rightarrow$ plastoquinone $\rightarrow$ P700 $\rightarrow$ cytochrome b₆f $\rightarrow$ plastocyanin $\rightarrow$ NADP⁺

Question 21

Light dependent ATP production is called _____ and occurs in the _____ of chloroplasts.

A) photophosphorylation; thylakoid membrane
B) photophosphorylation; inner membrane
C) non-oxidative phosphorylation; thylakoid membrane
D) non-oxidative phosphorylation; inner membrane
E) chloroplast-associated phosphorylation; thylakoid membrane

Question 22

In the Calvin cycle, ______ is "fixed" to generate carbohydrate molecules.

A) water
B) H+
C) O2
D) N2
E) CO2

Question 23

The most abundant biological catalyst is ______.

A) RuBisCO
B) ATP synthase
C) hexokinase
D) nitrogenase
E) water-splitting enzyme

Question 24

In the rubisco mechanism, what performs the nucleophilic attack on carbon dioxide?

A) water
B) enediolate intermediate
C) enol intermediate
D) a carboxylate
E) none of the above

Question 25

Why does rubisco make up about half of the protein content in a typical chloroplast?

A) most of the enzyme is in an oxidized state, waiting for the production of NADPH to reactivate it
B) it has an extremely high K_m for CO₂, thus a large number of enzymes increased the chance of substrate binding
C) since oxygen is also a substrate, those enzymes that bind oxygen are sequestered
D) it is a very inefficient enzyme, catalyzing only three reactions per second
E) none of the above

Question 26

If carbon dioxide is used as a substrate, the major products of rubisco are _____; if oxygen is used as a substrate, the major products of rubisco are _____.

A) 2 molecules of 3-phosphoglycerate; 2-phosphoglycolate and 3-phosphoglycerate
B) 2 molecules of 3-phosphoglycerate; glyoxylate and 3-phosphoglycerate
C) 3-phosphoglycerate and glyceraldehyde-3-phosphate; 2-phosphoglycolate and 3-phosphoglycerate
D) 3-phosphoglycerate and glyceraldehyde-3-phosphate; glyoxylate and 3-phosphoglycerate
E) none of the above

Question 27

In C₄ plants, CO₂ (as bicarbonate) is condensed with _____ to yield _____ in the mesophyll cells.

A) pyruvate; oxaloacetate
B) 3-phosphoglycerate; malate
C) lactate; fumarate
D) phosphoenolpyruvate; oxaloacetate
E) oxaloacetate; $\alpha$ -ketoglutarate

Question 28

In C₄ plants, _____ is found in the mesophyll cells to capture CO₂ while _____ is found in the bundle sheath cells to which releases CO₂.

A) phosphoenolpyruvate carboxylase; malate
B) pyruvate carboxylase; malic enzyme
C) pyruvate carboxylase; $\alpha$ -ketoglutarate dehydrogenase
D) pyruvate kinase; pyruvate dehydrogenase
E) none of the above

Question 29

Regeneration of the rubisco substrate, ribulose-1,5-bisphosphate involves which of the following sugars?

A) a tetrose-phosphate
B) a pentose-phosphate
C) a hexose-phosphate
D) a heptose-phosphate
E) all of the above

Question 30

The production of one molecule of glucose requires _____.

A) 6 CO₂, 9 ATP, 6 NADPH
B) 6 CO₂, 18 ATP, 12 NADPH
C) 6 CO₂, 6 ATP, 9 NADPH
D) 6 CO₂, 12 ATP, 18 NADPH
E) 3 CO₂, 9 ATP, 6 NADPH

Question 31

What causes carboxylation of a critical lysine residue that coordinates Mg²⁺ in the rubisco active site to occur?

A) when ATP levels are high due to high activity of the light reactions
B) when NADPH level are high due to high activity of the light reactions
C) when pH is low due to low activity of the light reactions
D) when pH is high due to high activity of the light reactions
E) when reduced ferredoxin is high due to high activity of the light reactions

Question 32

Fixation of one molecule of CO₂ in the Calvin cycle requires ___ ATP and ___ NADPH.

Question 33

Diazotrophs

A) may be free-living cyanobacteria
B) may be symbionts living in root nodules of legumes
C) supply plants with nitrogen for production of plant biomolecules
D) can process atmospheric nitrogen into ammonia
E) All of the above are correct

Question 34

Nitrogenase contains ___, unusual electron carrier(s).

A) FeMo cluster
B) 8Fe:7S cluster
C) 4Fe:4S cluster
D) Both A and B are correct
E) All of the above are correct

Question 35

Reduction of N2 requires

A) energy
B) ATP hydrolysis
C) water-splitting enzyme
D) an enzyme similar to RuBisCo
E) Both A and B are correct

Question 36

Which is true about nitrogenase?
I. Holds N2 to a metal ion during catalysis
II. Has N2 as its only substrate
III. Cleaves a triple bond
IV. Generates ammonia

A) I and II
B) III and IV
C) III only
D) I, III and IV
E) II and IV

Question 37

How is ammonia toxic to many species?
I. Its effect on choline production makes it neurotoxic
II. It acidifies physiologic fluids
III. It depletes citric acid cycle intermediates
IV. It can interfere with nucleotide biosynthesis

A) I and II
B) II, III and IV
C) III only
D) I and IV
E) I, II, III and IV

Question 38

The overall reduction of one N2 molecule requires

A) 8 protons, 8 electrons, 16 ATP
B) 8 protons, 8 electrons, 8 ATP
C) 16 electrons
D) 16 protons, 8 electrons, 16 ATP
E) 8 protons, 16 electrons, 16 ATP

Question 39

Although not completely clear, nitrogenase moves electrons from

A) the P center to the FeMo cluster to the 4Fe:4S center
B) the 4FE:4S center to the P center to the FeMo cluster
C) the FeMo cluster to the P center to the 4Fe:4S center
D) the FeMo cluster to the P center to the 8Fe:7S cluster
E) the 8Fe:7S cluster to the P center to the FeMo cluster