cell biology chapter 11

A house plant seems to be growing slowly and lacks its normal bright green color. You call a botanist for advice. She suggests that the plant may be deficient in magnesium (Mg2+). Why are these symptoms associated with Mg2+ deficiency? A) Mg2+ is important in the structure of many amino acids. B) Lack of Mg2+ in the soil allows pathogenic bacteria to grow. C) Mg2+ is required before NADPH can function. D) Mg2+ is an important component in chlorophyll. E) Cytochromes require Mg2+ to function properly.

. d. Mg2+ is an important component in chlorophyll.

Some herbicides, such as paraquat, work by causing the oxidation of NADPH to NADP. Although this is a potent herbicide, it also is toxic to humans, particularly when inhaled. How does paraquat interfere with photosynthesis and thus act as an herbicide? How might paraquat be causing toxicity for human cells?

By oxidizing NADPH to NADP directly, the amount of NADPH available for the Calvin cycle is minimized, and the plant literally starves to death. In human cells, any of the anabolic pathways that utilize NAPDH are compromised.

Hatch- Slack cycle

C4 plants

________ proteins stabilize the arrangement of the chlorophyll within a photosystem and modify the absorption spectra of specific chlorophyll molecules.

Chlorophyll-binding

________ (CAM) plants open their stomata only at night to minimize water loss.

Crassulacean acid metabolism

When atmospheric carbon dioxide concentrations decrease, the ________ cycle gives C4 plants an advantage over C3 when it comes to fixation.

Hatch-Slack

The endosymbiont theory attempts to explain the evolutionary origin of eukaryotes. Describe this theory in a paragraph. Be sure to use these terms: semiautonomous organelles, symbiotic relationship, protoeukaryote, purple bacteria, cyanobacteria, mitochondria, and chloroplasts.

Mitochondria and chloroplasts are semiautonomous organelles. They contain DNA, RNA, etc. b. Mitochondria may have evolved from purple bacteria, and chloroplasts may have evolved from cyanobacteria. c. A protoeukaryote developed from these symbiotic relationships.

The energy transduction reactions of photosynthesis convert solar energy into chemical energy in the form of ________ and ________.

NADPH, ATP

3-phosphoglycerate is to C3 plants as ________ is to C4 plants.

Oxaloacetate

________ (PC) is a copper-containing protein that, like plastoquinol, is a mobile electron carrier.

Plastocyanin

Why do tree leaves turn colors in autumn?

The chlorophyll within the leaves is no longer made because the plant has received signals to "overwinter." As a result, the decrease in the amount of chlorophyll allows the accessory pigments to become visible. Because these pigments are species specific, we see the range of colors characteristic for the fall season.

If you needed to design an herbicide that was effective against a variety of different plants, what would you propose as a method to target individually CAM plants, C4 plants, or a general herbicide?

The students need to realize that an effective general herbicide would need to target the photosynthetic pathway common to all of the groups suggested. Any answer that would interfere with transfer of electrons from plastoquinone to plastocyanin or prevent electron transfers to NADP would be good examples. The remaining two would need to target something unique to the CAM and C4 pathways, respectively. For CAM plants this may involve minimizing CO2 entry or target the conversion of oxaloacetate to malate. For C4 plants, blocking PEP carboxylase may be effective.

Rubisco is an important enzyme in the Calvin cycle. It catalyzes the addition of carbon dioxide and water to ribulose-1,5-bisphosphate, which then forms two molecules of 3-phosphoglycerate. Rubisco acts as a carboxylase and is essential for carbon fixation. a. Rubisco has an additional function. It can also function as an oxygenase. Why is this a problem for plants? b. Rubisco has a much lower affinity for oxygen than for carbon dioxide. Why is the oxygenase activity still a problem for plants? c. What is (are) the product(s) of the reaction when rubisco acts as an oxygenase? d. How does the plant deal with the product of the oxygenase reaction? e. The oxygenase activity of rubisco is particularly a problem for plants in arid environments. Can you explain why? f. What strategies do plants in arid environments use to deal with this problem?

a. If rubisco functioned solely as an oxygenase, carbon fixation would cease. b. The earth's atmosphere contains much higher concentrations of oxygen. c. Phosphoglycolate and 3-phosphoglycerate are the products rather than two molecules of 3-phosphoglycerate. d. The glycolate pathway is used to transform phosphoglycolate into 3-phosphoglycerate. e. Higher temperatures decrease carbon dioxide solubility relative to oxygen solubility. These plants close their stomata to reduce water loss. This will further reduce the concentrations of carbon dioxide in the leaf. f. C4 plants confine rubisco to cells containing high carbon dioxide levels. CAM plants only open their stomata at night.

Of the following plastids, which is not paired with the proper contents? A) amyloplasts; amylase B) chromoplasts; non-chlorophyll pigments C) chloroplasts; chlorophyll D) proteinoplasts; protein E) elaioplasts; lipids

a. amyloplasts; amylase

NADP+ is the coenzyme of choice in ________ reactions, while NAD+ is the coenzyme of choice in ________ reactions. A) anabolic; catabolic B) catabolic; anabolic C) metabolic; anabolic D) anabolic; both catabolic and anabolic E) both catabolic and anabolic; catabolic

a. anabolic; catabolic

Biosynthesis of sucrose occurs in the A) cytoplasm. B) stroma. C) thylakoid lumen. D) intermembrane space. E) stroma thylakoids.

a. cytoplasm

Which of the following products cannot be used in the Calvin cycle? A) phosphoglycolate B) NADPH C) 3-phosphoglycerate D) CO2 E) ribulose-1, 5-bisphosphate

a. phosphoglycolate

The Calvin cycle occurs in the ________ region of the chloroplast. A) stroma B) grana C) thylakoid lumen D) thylakoid membrane E) outer membrane

a. stroma

All of the following are true regarding anoxygenic photosynthesis except A) a water molecule is split. B) sulfide or thiosulfate can act as electron donors. C) absorbed light energy is typically in the near ultraviolet and far red ranges of the light spectrum. D) NADPH is regenerated by photoreduction. E) it is a light-driven oxidation-reduction process.

a. water molecule is split.

Green and purple bacteria are ________. This group of organisms removes electrons from sulfide, thiosulfate, and succinate to generate NADPH.

anoxygenic phototrophs

What is the advantage to having various types of chlorophylls and accessory pigments for the photosynthetic process? A) It allows for a variation in color amongst plants. B) It allows for light in many wavelengths to be utilized for photosynthesis. C) It allows light to be harvested specifically in a step-wise manner. D) It shifts the equilibrium of photosynthesis toward the formation of products. E) both choices C and D

b. It allows for light in many wavelengths to be utilized for photosynthesis.

Which of the following statements regarding CAM plants is true? A) Stomata are open during the day. B) Malate is stored in large vacuoles. C) CO2 is transported directly into mesophyll cells. D) They assimilate 25% less CO2 than C3 plants. E) both choices B and C

b. Malate is stored in large vacuoles.

Which of the following minerals are directly involved with light absorption in photosynthesis? A) Zn B) Mg C) Fe D) Ca E) Na

b. Mg

Which of the following initially traps solar energy in the process of photosynthesis? A) water B) chlorophyll C) triose phosphate D) NADP+ E) ATP

b. chlorophyll

Which two triose phosphates are produced during the Calvin cycle and are the starting points for starch and sucrose synthesis? A) 3-phosphoglycerate and glyceraldehyde-3-phosphate B) dihydroxyacetone phosphate and glyceraldehyde-3-phosphate C) ribulose-1,5-bisphosphate and glycerol phosphate D) dihydroxyacetone phosphate and glycerate-1,3-bisphosphate E) 3-phosphoglycerate and ribulose-1,5-bisphosphate

b. dihydroxyacetone phosphate and glyceraldehyde-3-phosphate

Plastoquinol transfers electrons from A) cytochrome b6/f complex to coenzyme Q. B) photosystem II to photosystem I. C) water to photosystem II. D) light harvesting complex II to photosystem II. E) cytochrome b6/f to plastiquinone.

b. photosystem II to photosystem I.

In the Calvin cycle, the enzyme that catalyzes the capture of carbon dioxide and the formation of 3-phosphoglycerate is A) phosphoglycerokinase. B) ribulose bisphosphate carboxylase/oxygenase (rubisco). C) triose phosphate isomerase. D) phosphoribulokinase. E) glyceraldehyde-3-phosphate dehydrogenase.

b. ribulose bisphosphate carboxylase/oxygenase (rubisco).

Carbon dioxide generally enters the plant through pores called A) mesophyll. B) stomata. C) the cuticle. D) connexons. E) bacteriochlorophylls.

b. stomata.

Diatoms have both chorophyll a and chlorophyll ________.

c

Which of the following compounds is not a source of electrons for anoxygenic photosynthesis? A) SH- B) S2O32- C) H2O D) succinate E) All of the above are used.

c. H2O

Which of the following statements correctly characterizes the relationship between NADP+/NADPH and NAD+/NADH? A) Both are used extensively during photosynthesis in oxygenic phototrophs. B) Neither are helpful to oxygenic phototrophs. C) NADP+/NADPH has an extra phosphate compared to NAD+/NADH. D) NADP+/NADPH is used primarily for catabolic reactions. E) Only NAD+/NADH is used to transport electrons and protons.

c. NADP+/NADPH has an extra phosphate compared to NAD+/NADH.

The relationship between photosystem I (PSI) and photosystem II (PSII) is correctly described by which of the following statements? A) PSI absorbs only short wavelengths of light. B) Electrons are excited by PSI or PSII, but not both. C) PSI is designated P700, whereas PSII is designated P680. D) The absorption maximum of PSII is 700 nm. E) The absorption maximum of PSI is 680 nm.

c. PSI is designated P700, whereas PSII is designated P680.

Bacteria do not have organelles. How are they able to carry out photosynthesis? A) They are parasites of plants that do have organelles. B) They interact in a symbiotic relationship with eukaryotic plants. C) They use their cell membrane to carry out photosynthesis. D) DNA in the nucleoid captures solar energy. E) 70S ribosomes function as photosystems.

c. They use their cell membrane to carry out photosynthesis.

Which of the following is not an essential feature of electron transfer from water to NADP+? A) photosystem II complex B) photosystem I complex C) coenzyme Q D) plastocyanin (PC) E) cytochrome b6/f complex

c. coenzyme Q

Photoheterotrophs are best described as organisms that obtain energy to make ATP A) from organic compounds but use sunlight to produce carbon sources. B) and organic compounds from sunlight. C) from sunlight but cannot make organic compounds from CO2. D) from some forms of chemicals. E) from organic compounds.

c. from sunlight but cannot make organic compounds from CO2.

The ATP synthase complex in the thylakoid membrane A) contains an embedded CF1 component and a protruding CFo component. B) is identical to the FoF1 complex of mitochondria. C) performs photophosphorylation in oxygenic phototrophs. D) contains an assembly of hydrophobic polypeptides that function in ATP synthesis. E) all of the above

c. performs photophosphorylation in oxygenic phototrophs.

The endosymbiotic theory states that mitochondria originated from A) a routine step in evolution. B) the fusion of several prokaryotes. C) purple bacteria entering and remaining in the cytoplasm of another cell. D) the slow evolution of various organelles over millions of years, particularly during the time of the dinosaurs. E) a long, intense period of lightning.

c. purple bacteria entering and remaining in the cytoplasm of another cell.

The regeneration of what CO2 acceptor molecule allows for continuous carbon assimilation in the Calvin cycle? A) glyceraldehyde-3-phosphate B) dihydroxyacetone phosphate C) ribulose-1,5-bisphosphate D) glycerate-1,3-bisphosphate E) 3-phosphoglycerate

c. ribulose-1,5-bisphosphate

Calvin cycle

carbon assimilation

sucrose synthesis

cytoplasm

Bacteriochlorophyll differs from chlorophyll a and b in structure and function. Which of the following statements correctly contrasts these types of chlorophyll? A) Bacteriochlorophyll has a porphyrin ring, whereas chlorophyll does not. B) Chlorophyll has a phytol side chain, but bacteriochlorophyll does not. C) Chlorophyll has a methyl group attached to the porphyrin ring, whereas bacteriochlorophyll has a formyl group. D) Bacteriochlorophyll has a saturated carbon-carbon bond at one location in the porphyrin ring, whereas chlorophyll does not. E) both choices A and D correctly contrast these types of chlorophyll.

d. Bacteriochlorophyll has a saturated carbon-carbon bond at one location in the porphyrin ring, whereas chlorophyll does not.

Which of the following statements is correct regarding cyclic photosynthetic pathways? A) Water molecules need to be split. B) Both PSI and PSII are required. C) Proton gradients are not formed. D) No exogenous electron source is required. E) all of the above

d. No exogenous electron source is required.

Plastocyanin (PC) A) is a mobile electron carrier. B) is also called plastoquinol. C) carries only a single electron at a time. D) both choices A and C E) choices A, B, and C

d. both choices A and C

The proplastids associated with giving flowers and fruits their distinctive colors are the A) chloroplasts. B) elaioplasts. C) amyloplasts. D) chromoplasts. E) plastids.

d. chromoplasts.

Which three organelles are involved in the glycolate pathway? A) lysosome, chloroplast, rough endoplasmic reticulum B) mitochondrion, nucleus, lysosome C) peroxisome, smooth endoplasmic reticulum, chloroplast D) peroxisome, chloroplast, mitochondrion E) Golgi complex, peroxisome, lysosome

d. peroxisome, chloroplast, mitochondrion

The process by which photosynthetic organisms use light energy for ATP production is known as A) photorespiration. B) photosynthesis. C) phototaxis. D) photophosphorylation. E) photoligase

d. photophosphorylation.

Based upon the comparisons of anoxygenic and oxygenic photosythesis, the entry of oxygen into the atmosphere is most directly attributed to A) photosystem I. B) the Calvin cycle. C) photoreactivation. D) photosystem II. E) bacteriorhodopsin.

d. photosystem II.

Which of the following is not an accessory pigment used to absorb photons that cannot be captured by chlorophyll? A) beta-carotene B) a phycobilin C) lutein D) phycochlorophyll E) phycocyanin

d. phycochlorophyll

Which of the following pigments is found exclusively in red algae? A) chlorophyll a B) chlorophyll c C) lutein D) phycoerythrin E) β-carotene

d. phycoerythrin

The transfer of energy from a photoexcited electron to another electron of an adjacent pigment molecule is known as A) photoexcitation. B) quantum leap. C) photophosphorylation. D) resonance energy transfer. E) photorespiration.

d. resonance energy transfer.

NADPH contains the pentose sugar ________ and the nitrogenous base ________. A) glucose; thymine B) deoxyribose; cytosine C) deoxyribose; nicotinamide D) ribose; adenine E) ribose; nicotinamide

d. ribose; adenine

The plants referred to as C3 and C4 plants get this designation based on the number of carbons in the first detectable product of carbon dioxide fixation. The C3 product is ________, whereas the C4 product is ________. A) glycerol; malate B) triose phosphate; oxaloacetate C) 3-phosphoglycerate; malate D) ribose; phosphoenolpyruvate E) 3-phosphoglycerate; oxaloacetate

e. 3-phosphoglycerate; oxaloacetate

Which of the following statements accurately describes the Calvin cycle? A) It is a carbon assimilation process. B) In this process, carbon dioxide is reduced to organic sugars. C) It occurs in the chloroplast stroma. D) The Calvin cycle is a means of carbon fixation. E) all of the above

e. all of the above

The Emerson enhancement effect A) was proposed by Robert Emerson in the 1980s. B) states that there are three or four separate photoreactions. C) is a synergistic phenomenon. D) is the result of two distinct photosystems. E) both choices C and D

e. both choices C and D

The Hatch-Slack cycle occurs in which of the following types of plants? A) algae B) C3 plants C) C4 plants D) tropical grasses E) both choices C and D

e. both choices C and D

In a chloroplast, the stroma is the A) cytochromes associated with the thylakoids. B) stack of thylakoids. C) region between in the inner and outer membranes. D) connection between the grana. E) central semifluid region.

e. central semifluid region.

anoxygenic phototrophs

electron donor is carbon dioxide

oxygenic phototrophs

electron donor is water

photoautotrophs

energy from sunlight, carbon from CO2

photohetrotrophs

energy from sunlight, carbon from organic sources

chromoplast

flower color

photoreduction

light-dependent generation of NADPH

elaioplast

lipid storage

The Calvin cycle in C3 plants occurs in ________ cells, whereas the Calvin cycle in C4 plants occurs in the ________.

mesophyll; bundle sheath

Light behaves as a stream of discrete particles called ________, each carrying a ________ (indivisible packet) of energy.

photons; quantum

The light-dependent generation of NADPH is referred to as ________.

photoreduction

The glycolate pathway is also called ________, because CO2 is released and oxygen is consumed in a light-dependent manner.

photorespiration

chloroplast

photosynthesis

proplastid

plastid precursor

Chlorophyll is comprised of a central ________ containing a(n) ________ ion and a(n) ________ side chain.

porphyrin ring; Mg, phytol

glycolate pathway

salvage pathway

amyloplast

starch storage

starch synthesis

stroma

crassulacean acid metabolism (CAM)

succulents

concentration of protons

thylakoid lumen

electron transport

thylakoid membrane