Question 1

Water flows into the source end of a sieve tube because ________.

Accepted Answer

A)  sucrose has diffused into the sieve tube, making it hypotonic 
B)  sucrose has been actively transported into the sieve tube, making it hypertonic 
C)  water pressure outside the sieve tube forces in water 
D)  the companion cell of a sieve tube actively pumps in water 
E)  sucrose has been transported out of the sieve tube by active transport 
A)  sucrose has diffused into the sieve tube, making it hypotonic 
B)  sucrose has been actively transported into the sieve tube, making it hypertonic 
C)  water pressure outside the sieve tube forces in water 
D)  the companion cell of a sieve tube actively pumps in water 
E)  sucrose has been transported out of the sieve tube by active transport B

Question 2

Which of the following statements about bulk flow are correct?
I. Bulk flow is driven primarily by pressure potential.
II. Bulk flow depends on a difference in pressure potential at the source and sink.
III. Bulk flow depends on the force of gravity on a column of water.
IV. Bulk flow may be the result of either positive or negative pressure potential.

Accepted Answer

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

Question 3

Phloem transport of sucrose is often described as going from source to sink. Which of the following is most likely to function as a source?

Accepted Answer

A)  a growing leaf in early spring 
B)  a growing root in late summer 
C)  a bulb in early spring 
D)  a shoot tip in late fall 
A)  a growing leaf in early spring 
B)  a growing root in late summer 
C)  a bulb in early spring 
D)  a shoot tip in late fall C

Question 4

As an undergraduate research assistant, you are assisting with a radioisotope tracer experiment. You expose a mature leaf on one side of the lower shoot of a sugar beet plant to 14CO2 and then track the movement of the 14C atoms by radiography. Where are you LEAST likely to detect 14C?

Accepted Answer

A)  the treated leaf 
B)  the shoot apical meristem 
C)  the roots 
D)  a mature upper leaf on the opposite side of the plant from the treated leaf 
E)  a young leaf directly above the treated leaf 
A)  the treated leaf 
B)  the shoot apical meristem 
C)  the roots 
D)  a mature upper leaf on the opposite side of the plant from the treated leaf 
E)  a young leaf directly above the treated leaf

Question 5

Irrigation reduces soil quality, but rains usually do not. Why?

Accepted Answer

A)  Rains deliver less water to soil than irrigation does. 
B)  Water used for irrigation contains fertilizer and pesticides that affect soil quality. 
C)  Rainwater contains lower amounts of salt. 
D)  The fast water flow during irrigation removes organic material from soil. 
E)  The fast water flow during rains is able to remove toxic materials from topsoil. 
A)  Rains deliver less water to soil than irrigation does. 
B)  Water used for irrigation contains fertilizer and pesticides that affect soil quality. 
C)  Rainwater contains lower amounts of salt. 
D)  The fast water flow during irrigation removes organic material from soil. 
E)  The fast water flow during rains is able to remove toxic materials from topsoil.

Question 6

Which of the following transmembrane transport mechanisms requires the expenditure of energy?

Accepted Answer

A)  channel 
B)  antiporter 
C)  facilitated diffusion 
D)  aquaporin 
A)  channel 
B)  antiporter 
C)  facilitated diffusion 
D)  aquaporin

Question 7

Which of the following would tend to increase transpiration?

Accepted Answer

A)  a rainstorm 
B)  sunken stomata 
C)  dry soils 
D)  higher stomatal density 
E)  spiny leaves 
A)  a rainstorm 
B)  sunken stomata 
C)  dry soils 
D)  higher stomatal density 
E)  spiny leaves

Question 8

What drives the flow of water through the xylem?

Accepted Answer

A)  passive transport by the endodermis 
B)  the number of companion cells in the phloem 
C)  the evaporation of water from the leaves 
D)  active transport by sieve-tube elements 
E)  active transport by tracheid and vessel elements 
A)  passive transport by the endodermis 
B)  the number of companion cells in the phloem 
C)  the evaporation of water from the leaves 
D)  active transport by sieve-tube elements 
E)  active transport by tracheid and vessel elements

Question 9

Active transport involves ________.

Accepted Answer

A)  diffusion of solute through the lipid bilayer of a membrane 
B)  pumping of solutes across the membrane 
C)  production of adenosine triphosphate (ATP) 
D)  transport of solute down a concentration gradient 
A)  diffusion of solute through the lipid bilayer of a membrane 
B)  pumping of solutes across the membrane 
C)  production of adenosine triphosphate (ATP) 
D)  transport of solute down a concentration gradient

Question 10

Why does overwatering a plant kill it?

Accepted Answer

A)  Water does not have all the necessary minerals a plant needs to grow. 
B)  Water neutralizes the pH of the soil. 
C)  The roots are deprived of oxygen. 
D)  Water supports the growth of root parasites. 
E)  Water lowers the water potential of the roots. 
A)  Water does not have all the necessary minerals a plant needs to grow. 
B)  Water neutralizes the pH of the soil. 
C)  The roots are deprived of oxygen. 
D)  Water supports the growth of root parasites. 
E)  Water lowers the water potential of the roots.

Question 11

Which theory of water transport in xylem can also be used to explain the primary movement of water in nonvascular plants such as mosses?

Accepted Answer

A)  cohesion-tension 
B)  capillarity 
C)  proton pump 
D)  air pressure 
A)  cohesion-tension 
B)  capillarity 
C)  proton pump 
D)  air pressure

Question 12

Which cells in a root form a protective barrier to the vascular system where all materials must move through the symplast?

Accepted Answer

A)  pericycle 
B)  cortex 
C)  epidermis 
D)  endodermis 
E)  exodermis 
A)  pericycle 
B)  cortex 
C)  epidermis 
D)  endodermis 
E)  exodermis

Question 13

What drives the flow of water through the xylem?

Accepted Answer

A)  passive transport by the endodermis 
B)  the number of companion cells in the phloem 
C)  the evaporation of water from the leaves 
D)  active transport by parenchyma cells within xylem tissue 
E)  active transport by tracheid and vessel elements 
A)  passive transport by the endodermis 
B)  the number of companion cells in the phloem 
C)  the evaporation of water from the leaves 
D)  active transport by parenchyma cells within xylem tissue 
E)  active transport by tracheid and vessel elements

Question 14

Which of the following supports the finding that sugar translocation from mesophyll cells into companion cells is an active (energy-requiring) process?

Accepted Answer

A)  Sucrose occurs in higher concentrations in companion cells than in the mesophyll cells where it is produced. 
B)  Movement of water occurs from xylem to phloem and back again. 
C)  ATPase proteins are not associated with sucrose transport. 
D)  Channel and carrier proteins are abundant in the plasma membranes of the mesophyll cells. 
A)  Sucrose occurs in higher concentrations in companion cells than in the mesophyll cells where it is produced. 
B)  Movement of water occurs from xylem to phloem and back again. 
C)  ATPase proteins are not associated with sucrose transport. 
D)  Channel and carrier proteins are abundant in the plasma membranes of the mesophyll cells.

Question 15

Compared to a cell with few aquaporins in its membrane, a cell containing many aquaporins will ________.

Accepted Answer

A)  have a faster rate of osmosis 
B)  have a lower water potential 
C)  have a higher water potential 
D)  have a faster rate of active transport 
E)  be flaccid 
A)  have a faster rate of osmosis 
B)  have a lower water potential 
C)  have a higher water potential 
D)  have a faster rate of active transport 
E)  be flaccid

Question 16

When an animal cell is placed in a hypotonic solution and water enters the cell via osmosis, the volume of the cell increases until it bursts. This does NOT happen to plant cells, because ________.

Accepted Answer

A)  they have large central vacuoles, which provide abundant space for storage of incoming water 
B)  the composition of their plasma membranes differs from that of animal-cell plasma membranes in a way that provides much greater strength 
C)  they have cell walls, which prevent the entry of water by osmosis 
D)  they have cell walls, which provide pressure to counteract the pressure of the incoming water 
E)  certain gated channel proteins embedded in their plasma membranes open as osmotic pressure decreases, allowing excess water to leave the cell 
A)  they have large central vacuoles, which provide abundant space for storage of incoming water 
B)  the composition of their plasma membranes differs from that of animal-cell plasma membranes in a way that provides much greater strength 
C)  they have cell walls, which prevent the entry of water by osmosis 
D)  they have cell walls, which provide pressure to counteract the pressure of the incoming water 
E)  certain gated channel proteins embedded in their plasma membranes open as osmotic pressure decreases, allowing excess water to leave the cell

Question 17

Most of the water taken up by a plant is ________.

Accepted Answer

A)  used as a solvent 
B)  used as a hydrogen source in photosynthesis 
C)  lost during transpiration 
D)  converted to carbon dioxide 
E)  used to keep cells turgid 
A)  used as a solvent 
B)  used as a hydrogen source in photosynthesis 
C)  lost during transpiration 
D)  converted to carbon dioxide 
E)  used to keep cells turgid

Question 18

Water potential in plants consists mainly of ________.

Accepted Answer

A)  solute potential and osmotic potential 
B)  solute potential and membrane potential 
C)  pressure potential and solute potential 
D)  pressure potential and membrane potential 
E)  solute potential only 
A)  solute potential and osmotic potential 
B)  solute potential and membrane potential 
C)  pressure potential and solute potential 
D)  pressure potential and membrane potential 
E)  solute potential only

Question 19

Which of the following would be LEAST likely to affect osmosis in plants?

Accepted Answer

A)  temperature 
B)  a difference in solute concentrations 
C)  receptor proteins in the membrane 
D)  aquaporins 
E)  a difference in water potential 
A)  temperature 
B)  a difference in solute concentrations 
C)  receptor proteins in the membrane 
D)  aquaporins 
E)  a difference in water potential

Question 20

If ΨP = 0.3 MPa and ΨS = −0.45 MPa, the resulting Ψ is ________.

Accepted Answer

A)  +0.75 MPa 
B)  −0.75 MPa 
C)  −0.15 MPa 
D)  +0.15 MPa 
E)  −0.42 MPa 
A)  +0.75 MPa 
B)  −0.75 MPa 
C)  −0.15 MPa 
D)  +0.15 MPa 
E)  −0.42 MPa

Exam 35: Water and Sugar Transport in Plants

Water flows into the source end of a sieve tube because ________.

Phloem transport of sucrose is often described as going from source to sink. Which of the following is most likely to function as a source?

As an undergraduate research assistant, you are assisting with a radioisotope tracer experiment. You expose a mature leaf on one side of the lower shoot of a sugar beet plant to 14CO2 and then track the movement of the 14C atoms by radiography. Where are you LEAST likely to detect 14C?

Irrigation reduces soil quality, but rains usually do not. Why?

Which of the following transmembrane transport mechanisms requires the expenditure of energy?

Which of the following would tend to increase transpiration?

What drives the flow of water through the xylem?

Active transport involves ________.

Why does overwatering a plant kill it?

Which theory of water transport in xylem can also be used to explain the primary movement of water in nonvascular plants such as mosses?

Which cells in a root form a protective barrier to the vascular system where all materials must move through the symplast?

What drives the flow of water through the xylem?

Which of the following supports the finding that sugar translocation from mesophyll cells into companion cells is an active (energy-requiring) process?

Compared to a cell with few aquaporins in its membrane, a cell containing many aquaporins will ________.

When an animal cell is placed in a hypotonic solution and water enters the cell via osmosis, the volume of the cell increases until it bursts. This does NOT happen to plant cells, because ________.

Most of the water taken up by a plant is ________.

Water potential in plants consists mainly of ________.

Which of the following would be LEAST likely to affect osmosis in plants?

If ΨP = 0.3 MPa and ΨS = −0.45 MPa, the resulting Ψ is ________.

Biology and the Tree of Life

Water and Carbon: the Chemical Basis of Life

Protein Structure and Function

Nucleic Acids and the Rna World

An Introduction to Carbohydrates

Ecosystems and Global Ecology

Lipids, Membranes, and the First Cells

Inside the Cell

Energy and Enzymes: an Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

Cellcell Interactions

The Cell Cycle

Meiosis

Mendel and the Gene

Dna and the Gene: Synthesis and Repair

How Genes Work

Transcription, Rna Processing, and Translation

Control of Gene Expression in Bacteria

Control of Gene Expression in Eukaryotes

The Molecular Revolution: Biotechnology and Beyond

Genes, Development, and Evolution

Evolution by Natural Selection

Evolutionary Processes

Speciation

Phylogenies and the History of Life

Bacteria and Archaea

Protists

Green Algae and Land Plants

Fungi

An Introduction to Animals

Protostome Animals

Deuterostome Animals

Viruses

Plant Form and Function

Plant Nutrition

Plant Sensory Systems, Signals, and Responses

Plant Reproduction and Development

Animal Form and Function

Water and Electrolyte Balance in Animals

Animal Nutrition

Gas Exchange and Circulation

Animal Nervous Systems

Animal Sensory Systems

Animal Movement

Chemical Signals in Animals

Animal Reproduction and Development

The Immune System in Animals

An Introduction to Ecology

Behavioral Ecology

Population Ecology

Community Ecology

Biodiversity and Conservation Biology

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