Question 1

The cell membrane is often referred to as asymmetrical or "mosaic".This means that

Accepted Answer

A) both layers of the phospholipid bilayer are not identical in terms of protein type or number and phospholipid type. 
B) only certain substances can pass through the phospholipid bilayer freely,while others require the help of membrane proteins. 
C) the phospholipids of the membrane can flip-flop such that phospholipids from the inner layer are exchanged with those from the outer layer. 
A) both layers of the phospholipid bilayer are not identical in terms of protein type or number and phospholipid type. 
B) only certain substances can pass through the phospholipid bilayer freely,while others require the help of membrane proteins. 
C) the phospholipids of the membrane can flip-flop such that phospholipids from the inner layer are exchanged with those from the outer layer.

Question 2

Why does cholesterol lower membrane permeability?

Accepted Answer

A) It is polar. 
B) It fills gaps in membranes and increases hydrophobic interactions. 
C) It participates in hydrogen bonding in the membrane interior. 
D) It is small relative to most phospholipids. 
A) It is polar. 
B) It fills gaps in membranes and increases hydrophobic interactions. 
C) It participates in hydrogen bonding in the membrane interior. 
D) It is small relative to most phospholipids.

Question 3

Which of the following crosses lipid bilayers the fastest?

Accepted Answer

A) a sodium ion 
B) a small,polar molecule like water 
C) a large,polar molecule like glucose 
D) a small,nonpolar molecule like oxygen (O₂) 
A) a sodium ion 
B) a small,polar molecule like water 
C) a large,polar molecule like glucose 
D) a small,nonpolar molecule like oxygen (O₂)

Question 4

Why do lipid bilayers form spontaneously?

Accepted Answer

A) The process is endergonic. 
B) The process is exergonic. 
C) The process leads to a huge decrease in entropy and no change in potential energy. 
D) The process is endothermic. 
A) The process is endergonic. 
B) The process is exergonic. 
C) The process leads to a huge decrease in entropy and no change in potential energy. 
D) The process is endothermic.

Question 5

Which of the following is not true of osmosis?

Accepted Answer

A) It is a special case of diffusion. 
B) It is an energy-demanding or "active" process. 
C) Water moves from areas of high water concentration to areas of low water concentration. 
A) It is a special case of diffusion. 
B) It is an energy-demanding or "active" process. 
C) Water moves from areas of high water concentration to areas of low water concentration.

Question 6

What do phospholipids and triglycerides have in common?

Accepted Answer

A) They both contain serine or some other organic compound. 
B) They both have three fatty acids. 
C) They both have a glycerol backbone. 
D) They both have a phosphate. 
A) They both contain serine or some other organic compound. 
B) They both have three fatty acids. 
C) They both have a glycerol backbone. 
D) They both have a phosphate.

Question 7

Which of the following is not a difference between passive facilitated transport and active transport?

Accepted Answer

A) Active transport requires energy input in the form of ATP,while facilitated transport does not. 
B) Active transport moves substances against their concentration gradient,while facilitated transport moves substances down their concentrations gradient. 
C) Active transport requires a membrane protein to move molecules across the plasma membrane,while facilitated transport does not. 
D) Active transport and facilitated transport both play a role in maintaining proper concentrations of substances in the intra- and extracellular environments. 
A) Active transport requires energy input in the form of ATP,while facilitated transport does not. 
B) Active transport moves substances against their concentration gradient,while facilitated transport moves substances down their concentrations gradient. 
C) Active transport requires a membrane protein to move molecules across the plasma membrane,while facilitated transport does not. 
D) Active transport and facilitated transport both play a role in maintaining proper concentrations of substances in the intra- and extracellular environments.

Question 8

You make two sucrose solutions,one of 0.5M and one of 2M and go out for lunch.When you return,you realize that you forgot to label the beakers! You remake the solutions,but give the undergrads in your lab an experiment to determine which beaker holds which solution.They fill two balloons,which are semi-permeable to water,but not to sucrose,with a 0.75M sucrose solution.One balloon is then placed in each of the unknown sucrose solution beakers.After several hours,they observe that the balloon in beaker 1 has swelled,while the balloon in beaker 2 has shrivelled.This indicates that beaker one contained the ________ sucrose solution,while beaker 2 contained the ________ sucrose solution.

Accepted Answer

A) 0)5M,2M 
B) 2M,0,5M 
C) unable to determine given the information provided. 
A) 0)5M,2M 
B) 2M,0,5M 
C) unable to determine given the information provided.

Question 9

You want to view a cross section of a particular cell at extremely high magnification.What tool would you use?

Accepted Answer

A) scanning electron microscope 
B) transmission electron microscope 
C) light microscope 
D) confocal microscope 
A) scanning electron microscope 
B) transmission electron microscope 
C) light microscope 
D) confocal microscope

Question 10

Which of the following best describes how gramicidin functions?

Accepted Answer

A) It acts by active transport. 
B) It causes membranes to fuse with one another. 
C) It forms a channel in the membrane. 
D) It removes electrical charges from solutes. 
A) It acts by active transport. 
B) It causes membranes to fuse with one another. 
C) It forms a channel in the membrane. 
D) It removes electrical charges from solutes.

Question 11

In marshes and other wet areas where vegetation is rotting,the water surface often has an oily sheen due to insoluble compounds.What are these molecules?

Accepted Answer

A) nucleic acids 
B) proteins 
C) lipids 
D) carbohydrates 
A) nucleic acids 
B) proteins 
C) lipids 
D) carbohydrates

Question 12

You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids.After testing the permeability of this membrane to glucose,you increase the proportion of unsaturated phospholipids in the bilayer.What will happen to the membrane's permeability to glucose?

Accepted Answer

A) You can't predict the outcome.You simply have to make the measurement. 
B) Permeability to glucose will increase. 
C) Permeability to glucose will decrease. 
D) Permeability to glucose will stay the same. 
A) You can't predict the outcome.You simply have to make the measurement. 
B) Permeability to glucose will increase. 
C) Permeability to glucose will decrease. 
D) Permeability to glucose will stay the same.

Question 13

In secondary active transport

Accepted Answer

A) two molecules are simultaneously moved across the cell membrane down their concentration gradients with the help of transport proteins. 
B) water is moved across the cell membrane based on solute concentration. 
C) a gradient is set up by a pump which then provides the potential energy to move a different molecule against its concentration gradient. 
D) Molecules are able to cross the plasma membrane unassisted with the help of ATP. 
A) two molecules are simultaneously moved across the cell membrane down their concentration gradients with the help of transport proteins. 
B) water is moved across the cell membrane based on solute concentration. 
C) a gradient is set up by a pump which then provides the potential energy to move a different molecule against its concentration gradient. 
D) Molecules are able to cross the plasma membrane unassisted with the help of ATP.

Question 14

Proteorhodopsin consists of a single polypeptide chain.What is the highest level of structure found in this protein?

Accepted Answer

A) primary 
B) secondary 
C) tertiary 
D) quaternary 
A) primary 
B) secondary 
C) tertiary 
D) quaternary

Question 15

GLUT-1 is an example of what?

Accepted Answer

A) a membrane-bound pump that moves large molecules against a gradient by using ATP 
B) a protein that is toxic to cells because it opens channels in membranes 
C) a recognition protein that identifies cells as belonging to the body 
D) a transport protein that facilitates diffusion of a large molecule across cell membranes 
A) a membrane-bound pump that moves large molecules against a gradient by using ATP 
B) a protein that is toxic to cells because it opens channels in membranes 
C) a recognition protein that identifies cells as belonging to the body 
D) a transport protein that facilitates diffusion of a large molecule across cell membranes

Question 16

Which of the following is the best explanation for why cholesterol decreases the permeability of biological membranes?

Accepted Answer

A) Cholesterol binds to the outside surface of a membrane,thus blocking the movement of solutes. 
B) Because cholesterol is amphipathic,it forms tiny vesicles that trap solutes. 
C) Because cholesterol is amphipathic,it fits in between the phospholipids and blocks diffusion through the membrane. 
D) Cholesterol has four rings in its structure that can sequester (trap)solutes. 
A) Cholesterol binds to the outside surface of a membrane,thus blocking the movement of solutes. 
B) Because cholesterol is amphipathic,it forms tiny vesicles that trap solutes. 
C) Because cholesterol is amphipathic,it fits in between the phospholipids and blocks diffusion through the membrane. 
D) Cholesterol has four rings in its structure that can sequester (trap)solutes.

Question 17

The text states that ribonucleotides can diffuse through some types of liposomes.It's likely that the lipids present early in chemical evolution had short chains.Would liposomes formed from these types of lipids be more or less permeable to ribonucleotides than if early cells formed from long-chained lipids?

Accepted Answer

A) more permeable 
B) less permeable 
C) same permeability 
A) more permeable 
B) less permeable 
C) same permeability

Question 18

What is the most important factor in explaining why diffusion occurs spontaneously?

Accepted Answer

A) It leads to an increase in entropy. 
B) It leads to a decrease in entropy. 
C) The process is exothermic. 
D) The process is endothermic. 
A) It leads to an increase in entropy. 
B) It leads to a decrease in entropy. 
C) The process is exothermic. 
D) The process is endothermic.

Question 19

Which of the following increases the strength of the hydrophobic interactions in lipid bilayers and thus makes them less permeable to polar molecules?

Accepted Answer

A) the presence of double bonds 
B) increasing temperature 
C) removing cholesterol 
D) increasing length of the hydrocarbon chains 
A) the presence of double bonds 
B) increasing temperature 
C) removing cholesterol 
D) increasing length of the hydrocarbon chains

Question 20

Which of the following means of transport would most likely be used for moving a medium-sized molecule (like a monosaccharide or an amino acid)from a low concentration on the outside of a cell to a high concentration on the inside of a cell?

Accepted Answer

A) facilitated diffusion through an ion channel protein 
B) facilitated diffusion through a transporter protein 
C) active transport through a "pump" protein 
D) passive transport 
A) facilitated diffusion through an ion channel protein 
B) facilitated diffusion through a transporter protein 
C) active transport through a "pump" protein 
D) passive transport

Exam 6: Lipids, membranes, and the First Cells

The cell membrane is often referred to as asymmetrical or "mosaic".This means that

Why does cholesterol lower membrane permeability?

Which of the following crosses lipid bilayers the fastest?

Why do lipid bilayers form spontaneously?

Which of the following is not true of osmosis?

What do phospholipids and triglycerides have in common?

Which of the following is not a difference between passive facilitated transport and active transport?

You want to view a cross section of a particular cell at extremely high magnification.What tool would you use?

Which of the following best describes how gramicidin functions?

In marshes and other wet areas where vegetation is rotting,the water surface often has an oily sheen due to insoluble compounds.What are these molecules?

You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids.After testing the permeability of this membrane to glucose,you increase the proportion of unsaturated phospholipids in the bilayer.What will happen to the membrane's permeability to glucose?

In secondary active transport

Proteorhodopsin consists of a single polypeptide chain.What is the highest level of structure found in this protein?

GLUT-1 is an example of what?

Which of the following is the best explanation for why cholesterol decreases the permeability of biological membranes?

What is the most important factor in explaining why diffusion occurs spontaneously?

Which of the following increases the strength of the hydrophobic interactions in lipid bilayers and thus makes them less permeable to polar molecules?

Which of the following means of transport would most likely be used for moving a medium-sized molecule (like a monosaccharide or an amino acid)from a low concentration on the outside of a cell to a high concentration on the inside of a cell?

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

Inside the Cell

Cell-Cell Interactions

Cellular Respiration and Fermentation

Photosynthesis

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

Analyzing and Engineering Genes

Genomics

Principles of Development

An Introduction to Animal Development

An Introduction to Plant Development

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

Water and Sugar Transport in Plants

Plant Nutrition

Plant Sensory Systems, signals, and Responses

Plant Reproduction

Animal Form and Function

Water and Electrolyte Balance in Animals

Animal Nutrition

Gas Exchange and Circulation

Electrical Signals in Animals

Animal Sensory Systems and Movement

Chemical Signals in Animals

Animal Reproduction

The Immune System in Animals

An Introduction to Ecology

Behavioural Ecology

Population Ecology

Community Ecology

Ecosystems

Biodiversity and Conservation Biology

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