Question 1

How do phospholipids interact with water molecules?

Accepted Answer

A) The polar heads avoid water;the nonpolar tails attract water (because water is polar and opposites attract). 
B) Phospholipids don't interact with water because water is polar and lipids are nonpolar. 
C) The polar heads interact with water;the nonpolar tails do not. 
D) Phospholipids dissolve in water. 
A) The polar heads avoid water;the nonpolar tails attract water (because water is polar and opposites attract). 
B) Phospholipids don't interact with water because water is polar and lipids are nonpolar. 
C) The polar heads interact with water;the nonpolar tails do not. 
D) Phospholipids dissolve in water.

Question 2

You have just discovered an organism that lives in extremely cold environments.Which of the following would you predict to be true about the phospholipids in its membranes,compared to phospholipids in the membranes of organisms that live in warmer environments?

Accepted Answer

A) The membrane phospholipids of cold-adapted organisms will have longer hydrocarbon tails. 
B) The membrane phospholipids of cold-adapted organisms will have more saturated hydrocarbon tails. 
C) The membrane phospholipids of cold-adapted organisms will have more unsaturated hydrocarbon tails. 
A) The membrane phospholipids of cold-adapted organisms will have longer hydrocarbon tails. 
B) The membrane phospholipids of cold-adapted organisms will have more saturated hydrocarbon tails. 
C) The membrane phospholipids of cold-adapted organisms will have more unsaturated hydrocarbon tails.

Question 3

To determine if membrane proteins affect membrane permeability,you could isolate the proteins from the lipid components of the membrane by using detergents.Then you could separate the individual proteins and test each of them in a planar bilayer.What technique could you use to separate the proteins from one another after they have been isolated from the membrane?

Accepted Answer

A) gel electrophoresis 
B) freeze-fracture electron microscopy 
C) diffusion 
D) amino acid analysis 
A) gel electrophoresis 
B) freeze-fracture electron microscopy 
C) diffusion 
D) amino acid analysis

Question 4

Which of the following is the best explanation for why vegetable oil is a liquid at room temperature while animal fats are solid?

Accepted Answer

A) Vegetable oil has more double bonds than animal fats. 
B) Vegetable oil has fewer double bonds than animal fats. 
C) Animal fats have no amphipathic character. 
D) Vegetable oil has longer fatty-acid tails than animal fats have. 
A) Vegetable oil has more double bonds than animal fats. 
B) Vegetable oil has fewer double bonds than animal fats. 
C) Animal fats have no amphipathic character. 
D) Vegetable oil has longer fatty-acid tails than animal fats have.

Question 5

In an experiment involving planar bilayers,a solution of table salt (sodium and chloride ions in water)is added on the left side of the membrane while pure water is added on the right side.After 30 minutes the researchers test for the presence of ions on each side of the membrane.The right side tests negative for ions.What can you conclude?

Accepted Answer

A) The experiment failed. 
B) The water somehow blocked the movement of ions across the membrane. 
C) The left side would probably also test negative for ions. 
D) Ions cannot cross planar bilayers. 
A) The experiment failed. 
B) The water somehow blocked the movement of ions across the membrane. 
C) The left side would probably also test negative for ions. 
D) Ions cannot cross planar bilayers.

Question 6

Steroid hormones are large communication molecules that are modified cholesterol molecules.How do you think they enter a cell?

Accepted Answer

A) Their size probably allows them to diffuse through the plasma membrane. 
B) Their lipid nature probably allows them to diffuse through the plasma membrane. 
C) Their protein nature probably allows them to diffuse through the plasma membrane. 
D) They must require a protein transporter,because the plasma membrane is completely impermeable to molecules. 
A) Their size probably allows them to diffuse through the plasma membrane. 
B) Their lipid nature probably allows them to diffuse through the plasma membrane. 
C) Their protein nature probably allows them to diffuse through the plasma membrane. 
D) They must require a protein transporter,because the plasma membrane is completely impermeable to molecules.

Question 7

Valine,a nonpolar amino acid,shows up in the wrong place in the hemoglobin of sickle-cell anemia,causing the disease.This is due to a genetic mutation.The result of this mutation is that hemoglobin molecules-which transport oxygen in red blood cells-stick together,causing the red blood cells to become distorted,but without having any significant effect on oxygen binding.Based on what you know about protein structure and the polarity of amino acids,predict where the mutated valine would most likely be found.

Accepted Answer

A) on the surface of hemoglobin 
B) in the deep interior of hemoglobin 
C) in the oxygen binding site of hemoglobin 
D) along a nonpolar region of a β-pleated sheet 
A) on the surface of hemoglobin 
B) in the deep interior of hemoglobin 
C) in the oxygen binding site of hemoglobin 
D) along a nonpolar region of a β-pleated sheet

Exam 6: Lipids, membranes, and the First Cells

How do phospholipids interact with water molecules?

You have just discovered an organism that lives in extremely cold environments.Which of the following would you predict to be true about the phospholipids in its membranes,compared to phospholipids in the membranes of organisms that live in warmer environments?

Which of the following is the best explanation for why vegetable oil is a liquid at room temperature while animal fats are solid?

Steroid hormones are large communication molecules that are modified cholesterol molecules.How do you think they enter 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 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 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

Behavioral Ecology

Population Ecology

Community Ecology

Ecosystems

Biodiversity and Conservation Biology

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