Chapter 3

Construct a portion of cell membrane using the typical phospholipid symbols. Indicate the location of the cytoplasm and outside of the cell. Explain how the chemical characteristics of phospholipid molecules dictate membrane structure and cause it to be fluid in nature.

A bilayer forms due to the chemical nature of the hydrophilic and hydrophobic regions of the phospholipids. The hydrophilic heads are attracted to aqueous regions of the cytoplasm and extracellular fluid (or outside the cell). The hydrophobic tails cluster away from the aqueous regions. Kinks in the tails of unsaturated fatty acids increase the fluidity of the bilayer.

Choose the figure that depicts polymer synthesis.

A) Figure 1

Which of the following protein is correctly matched with its location?

A) Hemoglobin is found within the red blood cells.

Which fucntional group attached to a hydrocarbon chain will form an alcohol?

A) Hydroxyl

Which of the following represents a sulfhydryl group?

A) SH

How do the lipids of the cell membrane and the lipids found in butter and vegtable oil differ?

A) The number of fatty acids.

Your professor shows you a computer model of a protein and asks you to identify the structural level. It appears to consist of only one polypeptide chain and has a globular shape. What is your determination?

A) The protein has tertiary structure.

A dehydration reaction can also be called a(n) ________ reaction since it forms water.

A) condensation

Fish sperm is composed mostly of DNA. If we tested a sample chemically, we should find relatively high amounts of

A) nitrogenous bases, sugar, and phosphate groups.

Due to an increased risk of heart disease many doctors have suggested shifting our diet to include more unsaturated fats and less saturated fats. As you cook dinner tonight the recipe calls for two Tbs of oil. Which of the following would be the healthiest choice?

A) olive or safflower oil

What are the basic structures that make up a nucleotide?

A) pentose sugar, phosphate, and nitrogen-containing bas

Which of the following is a function of a steroid?

A) sex hormone

A polysaccharide is a polymer made up of which kind of monomers?

A) simple sugars

At the molecular level, cells from different types of organisms vary in their tolerance to temperature and pH. This variation can mostly likely be attributed to

A) the types of enzymes present in the cells.

A strand of DNA has the following base sequence: ATTGCGAATGGCA. Construct the complementary strand of DNA.

Adenine and thymine and cytosine and guanine are complementary base pairs. The complementary strand has the sequence: TAACGCTTACCGT.

Organic molecules are those that contain at least

C) carbon and hydrogen.

Which carbohydrate is found in the cell walls of plants?

C) cellulose

A hydrocarbon is hydrophobic

C) except when it has a polar functional group attached.

Which of the following is the primary function of carbohydrates in living organisms?

Carbohydrates are used as an immediate energy source.

Which of the following is NOT a function of proteins?

E) insulation

A carbon atom can form up to three single covalent bonds with other atoms.

FALSE

Migratory birds store energy as glycogen which is lighter than fat.

FALSE

Starch is a polysaccharide that stores energy in animal cells

FALSE

Waxes consist of a glycerol bonded to three long-chain fatty acids.

FALSE

Which of the following carbohydrates would NOT be a molecule used for energy storage?

B) Cellulose

Which statement is true about RNA?

B) One of the bases from DNA is replaced by uracil.

Which of the following is true about the differences between organic and inorganic molecules?

B) Organic molecules contain at least carbon and hydrogen and inorganic molecules do not.

You come across an article that discusses a new drug that interferes with hydrogen bonding during protein formation. Based on your understanding of the levels of protein organization, which of the following is a probable consequence following exposure to this new drug?

B) Protein folding will arrest during the formation of secondary structure. The drug would prevent the polypeptide from forming an alpha helix or a beta sheet.

Which of the following structures is classified as a nucleic acid?

B) RNA

Which of the following are characteristic of carbohydrates? Select all that apply.

B) The monomer subunits are constructed primarily from carbon, hydrogen, and oxygen. C) Carbohydrates provide an immediate source of energy for cells. E) Chitin is a carbohydrate found in the exoskeletons of crabs and other similar animals.

You come across an image of a molecule in research article about fatty acids. You notice the molecule has several double bonds in its structure. Based on your knowledge of fatty acids, you conclude that this molecule is most likely

B) an unsaturated fatty acid.

Which carbohydrate is found in the exoskeleton of insects and crabs?

B) chitin

If an animal needed to store energy for long-term use which of the following would be the best choice?

B) fat molecules

How many molecules of water are used during hydrolysis to break the following polypeptide into its constituent amino acids: alanine-leucine-tryptophan-glycine-valine-alanine?

B) five

What term is used for molecules that have identical molecular formulas but the atoms in each molecule are arranged differently?

B) isomer

In lab, your biology instructor has asked you to identify an unknown solution. During one of the tests you perform your sample turns light purple indicating the presence of peptide bonds. Based on this information, you determine your solution contains

B) protein.

The alpha helix and beta sheet are found at which level of protein organization?

B) secondary structure

The reactivity of an organic molecule is primarily dependent upon ________ of the molecule.

B) the attached functional groups

What is the molecular formula for five glucose (C6H12O6) molecules bonded together by dehydration synthesis?

C) C30H52O26

Identify this molecule:

C) carbohydrate

If 15% of the bases in a DNA molecule are adenine, what percentage is cytosine?

D) 35%

Which statement below correctly describes why ATP is a high energy structure?

D) ATP has three phosphate bonds, two of which are unstable and easily broken.

A saturated fat

D) All of the choices are correct.

Saturated fatty acids and unsaturated fatty acids differ in

D) All of the choices are differences between saturated and unsaturated fatty acids.

Which of these statements is NOT true about DNA?

D) It contains the sugar ribose.

A polypeptide has an amino acid sequence of: alanine-leucine-tryptophan-glycine-valine-alanine. This chain of amino acids is further organized into a helix that folds in and around itself to form a globular structure. The primary structure of this polypeptide is

D) alanine-leucine-tryptophan-glycine-valine-alanine.

Which of the following are structural carbohydrate molecules?

D) cellulose and chitin

Which carbohydrate is used to store energy in the liver?

D) glycogen

A peptide bond is found in which type of biological molecule?

D) protein

Identify the following molecule:

E) cholesterol

A triglyceride is a polymer made up of which kind of subunits?

E) fatty acids and glycerol

If a DNA molecule contains 20% guanine, how much cytosine will the DNA molecule contain?

Guanine complementary base pairs with cytosine. Therefore, if the DNA molecules consists of 20% guanine, it will also have 20% cytosine.

ATP is a nucleotide that functions in providing energy for cellular work.

TRUE

What is the molecular formula of these molecules? How do these molecules differ? Are these the same molecule?

These are different molecules, glyceraldehyde on the left and dihydroxyacetone on the right. They are structural isomers, having the same molecular formulas but different structures.

The feet of penguins and reindeer contain large amounts of unsaturated fatty acids. Why would these animals have these fats in their feet rather than saturated fats?

Triglycerides containing unsaturated fatty acids will freeze at a lower temperature than those containing only saturated fatty acids. An abundance of polyunsaturated fats helps to protect the organism from freezing in colder climates

Chitin and cellulose are both carbon-based molecules that do not spontaneously decompose. What would happen if all of the chitin and cellulose decomposers were destroyed?

When chitin and cellulose are decomposed, the carbon may be recycled as carbon dioxide if oxygen is present or methane if there is no oxygen available. Inorganic elements are returned to the soil. If there are no decomposers, the carbon would remain within the undigested chitin and cellulose. This would alter the carbon cycle and would leave undigested plant, fungi and animals everywhere. In addition, the carbon available for the building of new life would decrease.