Question 1

The sodium-potassium pump is called an electrogenic pump because it ________.

Accepted Answer

A)  pumps equal quantities of Na⁺ and K⁺ across the membrane in opposite directions 
B)  is used to drive the transport of glucose against a concentration gradient 
C)  decreases the voltage difference across the membrane 
D)  generates voltage across the membrane 
A)  pumps equal quantities of Na⁺ and K⁺ across the membrane in opposite directions 
B)  is used to drive the transport of glucose against a concentration gradient 
C)  decreases the voltage difference across the membrane 
D)  generates voltage across the membrane

Question 2

In what way do the membranes of a eukaryotic cell vary?

Accepted Answer

A)  Phospholipids are found only in certain membranes. 
B)  Certain proteins are unique to each membrane. 
C)  Only certain membranes of the cell are selectively permeable. 
D)  Some membranes have hydrophobic surfaces exposed to the cytoplasm while others have hydrophilic surfaces facing the cytoplasm. 
A)  Phospholipids are found only in certain membranes. 
B)  Certain proteins are unique to each membrane. 
C)  Only certain membranes of the cell are selectively permeable. 
D)  Some membranes have hydrophobic surfaces exposed to the cytoplasm while others have hydrophilic surfaces facing the cytoplasm.

Question 3

In some cells, there are many ion electrochemical gradients across the plasma membrane even though there are usually only one or two proton pumps present in the membrane. The gradients of the other ions are most likely accounted for by ________.

Accepted Answer

A)  cotransport proteins 
B)  ion channels 
C)  pores in the plasma membrane 
D)  passive diffusion across the plasma membrane 
A)  cotransport proteins 
B)  ion channels 
C)  pores in the plasma membrane 
D)  passive diffusion across the plasma membrane

Question 4

Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes?

Accepted Answer

A)  the sodium-potassium pump 
B)  aquaporins 
C)  gated ion channels 
D)  ATP 
A)  the sodium-potassium pump 
B)  aquaporins 
C)  gated ion channels 
D)  ATP

Question 5

For the following questions, match the labeled component of the cell membrane in the figure with its description.
- 
Which component in the accompanying figure is a microfilament (actin filament)of the cytoskeleton?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
A)  A 
B)  B 
C)  C 
D)  D

Question 6

Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and -1.0 M. Cubes of sweet potato (1 cm³)were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. From the data given, which statement most accurately describes what is occurring in response to a particular unknown solution?
$$\begin{array} { | l | l | l | l | } 
\hline \text { Unknown } & \text { Percent change in } & \text { Percent change in } & \text { Percent change in } \
& \text { Graup 1 } & \text { Guss } & \text { mass } \
\hline \text { A } & 6.6 & 7.8 & \text { Group 3 } \
\hline \text { B } & 3.1 & 3.7 & 7.5 \
\hline E & - 2.7 & - 3.5 & 2.9 \
\hline \text { D } & 0.7 & 0.5 & - 2.5 \
\hline \text { E } & - 11.6 & - 12.3 & 1.1 \
\hline & - 5.2 & 6.2 & - 12.6 \
\hline
\end{array}$$

Accepted Answer

A)  Unknown solution E contains the highest concentration of sucrose, and the change in mass is due to the active transport of sucrose out of the cell. 
B)  Osmosis of water molecules from unknown solution B likely caused the increase in mass observed. 
C)  Passive transport of sucrose out of the potato cells explains the change in mass observed for unknown solution F. 
D)  Unknown solution C represents a sucrose concentration slightly higher than the molarity of sweet potato cells, thus water is transported out of the cells. 
A)  Unknown solution E contains the highest concentration of sucrose, and the change in mass is due to the active transport of sucrose out of the cell. 
B)  Osmosis of water molecules from unknown solution B likely caused the increase in mass observed. 
C)  Passive transport of sucrose out of the potato cells explains the change in mass observed for unknown solution F. 
D)  Unknown solution C represents a sucrose concentration slightly higher than the molarity of sweet potato cells, thus water is transported out of the cells.

Question 7

Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer?

Accepted Answer

A)  transmembrane proteins 
B)  integral membrane proteins 
C)  peripheral membrane proteins 
D)  cholesterol 
A)  transmembrane proteins 
B)  integral membrane proteins 
C)  peripheral membrane proteins 
D)  cholesterol

Question 8

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

Accepted Answer

A)  spread in a continuous layer over the inner and outer surfaces of the membrane. 
B)  confined to the hydrophobic interior of the membrane. 
C)  embedded in a lipid bilayer. 
D)  randomly oriented in the membrane, with no fixed inside-outside polarity. 
A)  spread in a continuous layer over the inner and outer surfaces of the membrane. 
B)  confined to the hydrophobic interior of the membrane. 
C)  embedded in a lipid bilayer. 
D)  randomly oriented in the membrane, with no fixed inside-outside polarity.

Exam 7: Membrane Structure and Function

The sodium-potassium pump is called an electrogenic pump because it ________.

In what way do the membranes of a eukaryotic cell vary?

In some cells, there are many ion electrochemical gradients across the plasma membrane even though there are usually only one or two proton pumps present in the membrane. The gradients of the other ions are most likely accounted for by ________.

Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes?

For the following questions, match the labeled component of the cell membrane in the figure with its description. - Which component in the accompanying figure is a microfilament (actin filament)of the cytoskeleton?

Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer?

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

Evolution, the Themes of Biology, and Scientific Inquiry

The Chemical Context of Life

Water and Life

Carbon and the Molecular Diversity of Life

The Structure and Function of Large Biological Molecules

A Tour of the Cell

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

Cell Communication

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Chromosomal Basis of Inheritance

The Molecular Basis of Inheritance

Gene Expression: From Gene to Protein

Regulation of Gene Expression

Viruses

DNA Tools and Biotechnology

Genomes and Their Evolution

Descent with Modification: A Darwinian View of Life

The Evolution of Populations

The Origin of Species

The History of Life on Earth

Phylogeny and the Tree of Life

Bacteria and Archaea

Protists

Plant Diversity I: How Plants Colonized Land

Plant Diversity II: The Evolution of Seed Plants

Fungi

An Overview of Animal Diversity

An Introduction to Invertebrates

The Origin and Evolution of Vertebrates

Vascular Plant Structure, Growth, and Development

Resource Acquisition and Transport in Vascular Plants

Soil and Plant Nutrition

Angiosperm Reproduction and Biotechnology

Plant Responses to Internal and External Signals

Basic Principles of Animal Form and Function

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Osmoregulation and Excretion

Hormones and the Endocrine System

Animal Reproduction

Animal Development

Neurons, Synapses, and Signaling

Nervous Systems

Sensory and Motor Mechanisms

Animal Behavior

An Introduction to Ecology and the Biosphere

Population Ecology

Community Ecology

Ecosystems and Restoration Ecology

Conservation Biology and Global Change

Filters