Chapter 3

The ionized or dissociated carboxyl group may be written as __________.

-COO-

Which of these functional groups is found in all amino acids?

-NH2

All proteins can be made from varying combinations of ___________amino acids.

20

Lactase deficiency is more common in Asian, Native American, Mediterranean and some African populations than it is among people with northern or western European ancestry. How would you explain why this is so?

Although most mammals, including humans, are not able to digest the milk sugar, lactose, after infancy, the ancestors of northern and western Europeans relied on dairy products as an important part of their food supply. When other food sources were in low supply, mutations that allowed the expression of the enzyme lactase to persist past childhood conveyed an advantage to adults who were able to include dairy products in their diet.

Some athletes use anabolic steroids to build their body mass. Why is this considered a problematic practice, especially in adolescents?

Anabolic steroids can prevent bone growth.

What do phospholipids and cholesterol have in common?

Both are important components of cell membranes.

Select the hydrocarbon from the following choices. C3H8 C6H12O6 CO2 H2CO3

C3H8

Which of the following molecules is a carbohydrate? C51 H98 O6 C22 H49 O10 N5 C60 H100 O50 C45 H84 O8 P4

C60 H100 O50

Which element is closely associated with the field of organic chemistry?

Carbon

Which of the following statements about carbon skeletons is true? -Carbon skeletons may be arranged in rings. -Carbon skeletons are always linear and never branched. -Carbon skeletons only contain double bonds. -The length of carbon skeletons is always the same; it is the attachments that differentiate molecules.

Carbon skeletons may be arranged in rings.

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture _____.

DNA

Information dictating the primary sequence of a polypeptide is permanently maintained within a cell in which of the following forms?

DNA

Of the following sugar molecules, which is not a disaccharide? lactose fructose maltose sucrose

Fructose

Compounds with same formula but different structure are ___________.

Isomers

What does the term amino acid signify about the structure of the molecule?

It consists of an amino group and a carboxyl group.

Which of the following statements regarding lactose tolerance is true? -Relatively few people on this planet are lactose intolerant. -The ability to hydrolyze lactose would be equally beneficial to all human populations. -Lactose tolerance has evolved independently in multiple different human populations. -Lactose intolerance refers to a person's inability to produce the sugar lactose.

Lactose tolerance has evolved independently in multiple different human populations.

Generally, animals cannot digest the linkages between the glucose molecules in cellulose. How then do cows get enough nutrients from eating grass?

Microorganisms in their digestive tracts hydrolyze the cellulose to glucose.

How does DNA differ from RNA?

RNA contains ribose, DNA does not.

Which statement correctly describes bonds of the secondary structure of proteins?

Secondary structure involves hydrogen bonding between atoms of the polypeptide backbone.

Two proteins have the same number and type of amino acids. How is it that they can have different shapes and therefore different functions?

The order in which the amino acids are arranged differs between the two proteins.

When calorie intake is low, proteins are the last resource the body uses for fuel. Which statement below gives the best reason for this?

When the body uses proteins as fuel, it is breaking down substances vital to its structure and essential functions.

A glucose molecule is to starch as __________.

a nucleotide is to a nucleic acid

Proteins are an important class of molecules because of the functions they perform. Proteins can _____.

act as signal receptors to receive signals in cell communication

Manufacturers make vegetable oils solid or semisolid by _____.

adding hydrogens

Choose the pair of terms that completes this sentence: Hydroxyl is to _____ as _____ is to amine.

alcohol ... amino

Although the structures of the functional groups important to life (hydroxyl, carbonyl, carboxyl, amino, and phosphate) vary in chemical structure, they share one thing in common: They _____.

all are hydrophilic and increase the organic compound's water solubility

Ethanol, propanol, and methanol are three simple alcohols. They can be grouped together because they _____.

all share the same functional group, a hydroxyl

Lipids differ from other large biological molecules in that they _____.

are not truly polymers

Carbohydrates are mainly used in our bodies _____.

as fuel

An amino acid is so named because its central carbon is linked to both an amino group and a __________.

carboxyl group

The reaction that joins two monomers to form a polymer is known as a _____ reaction. The molecule of water formed is due to the interaction between _____ and a hydrogen ion.

dehydration ... a hydroxyl group

A peptide bond is formed through a __________.

dehydration reaction between the amino group of one amino acid and the carboxyl group of a second amino acid

A DNA nucleotide is composed of a __________.

deoxyribose sugar, which is bonded to a phosphate group and a nitrogenous base

Which condition is irrelevant, to some extent, to the maintenance of protein structure in your body?

environmental temperature

The oil and vinegar in your salad dressing remain separate from one another due to the _____ properties of the oil.

hydrophobic

Which is the correct term for compounds that do not mix with water?

hydrophobic

Dehydration reactions __________. They do so by __________.

link monomers to form a polymer; removing a water molecule

Cholesterol belongs to which class of molecules?

lipids

Double bonds are present in the majority of the fats of which of the following foods? lard margarine peanuts eggs

peanuts

Anabolic steroids are appropriately prescribed to __________.

people who suffer from muscle-debilitating diseases

The lipids that form the main structural component of cell membranes are _____.

phospholipids

Cellulose is a _____ made of many _____.

polymer ... glucose molecules

DNA carries the instructions for building _____, and these instructions are found in informational units called _____.

polypeptides ... genes

Which of the following sugars CAN be accurately represented by the formula C6H12O6?

possibly glucose or fructose

When you eat a plant, you derive energy from the stored __________, but not from the __________ component.

starch ... cellulose

Which of the following would be affected when a protein is denatured?

tertiary structure

A fatty acid containing at least one double bond is called _____

unsaturated

When an RNA strand forms using DNA as a template, _____.

uracil pairs with adenine and cytosine pairs with guanine

When two monosaccharides link to form a disaccharide, the by-product is __________.

water