Question 1

Which function has the least priority for protein?

Accepted Answer

Energy storage is a primary function of carbohydrates and fats.Although protein can produce and store energy,this is not a primary role and takes away from other vital roles.The remaining selections are priority functions of protein.Note that catalyzing a reaction involves breaking down of components,such as when more complex molecules are catabolized into smaller molecules.

Question 2

The biological function that plants use to make the carbohydrate animals can use for energy and oxygen is called:

Accepted Answer

Photosynthesis is the biological function that plants use to make the carbohydrate C₆H₁₂O₆ (glucose),a carbohydrate that animals can use for energy and storage.Oxidation-reduction,condensation,and hydrolysis are chemical reactions that can convert functional groups into other functional groups.

Question 3

Enzymes perform all the chemical reactions of metabolism involving degradation and biosynthesis of biomolecules required for life.Proteases,amylases,and lipases are coenzymes.

Accepted Answer

The first statement is true; the second is false.Proteases,amylases,and lipases are enzymes,not coenzymes,that begin the process of digesting dietary proteins,carbohydrates,and lipids,respectively.

Question 4

Coenzymes are protein organic substances that assist enzymes in converting the substrate into a carbohydrate.Many vitamins are converted into biologically active coenzymes.

Accepted Answer

The first statement is false; the second is true.Coenzymes are nonprotein organic substances that assist enzymes in converting the substrate into a product.The product may be a carbohydrate,but not necessarily.Coenzymes are regenerated at the end of the reactions.

Question 5

Fatty acids are structural components that are present in more complex lipids,such as triglycerides (TGs).Also referred to as triacylglycerols,TGs synthesize fatty acids.

Accepted Answer

The first statement is true; the second is false.Triglycerides,also referred to as triacylglycerols,do not synthesize fatty acids.TGs are the storage forms of fatty acids (FAs)and are considered the metabolic fuel for cells stored in adipose (fat)tissue.

Question 6

Each is a component of an amino acid,except one.Which is the exception?

Accepted Answer

Carbon dioxide is not a component of an amino acid.It is a product from the oxidation of glucose.The amino group,the carboxyl group,and the R group form the general structure of an amino acid.Proteins can consist of as few as 50 to as many as millions of amino acid monomers.

Question 7

During the Krebs cycle,complete aerobic oxidation of glucose (C₆H₁₂O₆)produces each of the following,except one.Which is the exception?

Accepted Answer

During the Krebs cycle,also known as the TCA cycle,complete aerobic oxidation of glucose produces carbon dioxide (CO₂),water (H₂O),and adenosine triphosphate (ATP).Glucose is a carbohydrate,whereas amino acids are broken down from proteins.Although amino acids are involved in the Krebs cycle,the production of CO₂,water,and ATP from glucose differs from the production of amino acids from protein.Note that lipids are also catabolized during the Krebs cycle.Ultimately,the end products of catabolism of all nutrients are CO₂,H₂O,and ammonia (NH₃).

Question 8

Antioxidants like vitamins C and E are added to unsaturated fats because antioxidants prevent rancidity associated with the oxidation during preparation of vegetable oils and margarines.

Accepted Answer

Both the statement and the reason are correct and related.A common but unwanted reaction involving C=C bonds is oxidation.Oxidation of unsaturated fats leads to rancidity; therefore,antioxidants,such as vitamins C and E,are added to vegetable oils as a preventive measure.

Question 9

Which is NOT a classification of carbohydrate?

Accepted Answer

Triglycerides,also referred to as triacylglycerols,are the storage forms of fatty acids,not carbohydrates,and are considered the metabolic fuel for cells stored in adipose (fat)tissue.

Question 10

In metabolism,energy is extracted from glucose (C₆H₁₂O₆)and converted to carbon dioxide (CO₂)by which chemical reaction?

Accepted Answer

During metabolism,the chemical reaction called oxidation extracts energy from glucose and converts it to carbon dioxide.This is termed a complete oxidation.Note that oxidation is the loss of electrons,increase in charge,gain of O atoms or loss of H atoms.

Question 11

The biomolecules necessary for life are based on carbon because carbon has the ability to form glycosidic bonds to itself and many other atoms.

Accepted Answer

The statement is correct,but the reason is not correct.Biomolecules are based on carbon because carbon has the ability to form stable covalent bonds with itself and with many other atoms.A covalent bond forms when electrons are shared equally between two nonmetals.A glycosidic bond forms when a disaccharide is formed from two monosaccharides reacting together.

Question 12

In general,a condensation reaction creates a new molecule by:

Accepted Answer

In general,a condensation reaction creates a new molecule by forming a bond between two smaller molecules.Regarding the incorrect selections,a hydrolysis reaction breaks a larger molecule into two smaller molecules.Ionic bonds are formed between a metal and a nonmetal ion.A covalent bond forms when two electrons are equally shared between two nonmetals.

Question 13

Each is true of proteins,except one.Which is the exception?

Accepted Answer

The classification of the 20 common amino acids is based on the structure of their side chain.The side chain is one component of the general structure of an amino acid and is also called the R group.The other two components are the amino group and the carboxyl group.

Question 14

Each is a major area of biochemistry,except one.Which is the exception?

Accepted Answer

Function is not a major area of biochemistry.The three major areas of biochemistry,the study of life at the molecular level,are structure,metabolism,and bioinformation.

Question 15

Biochemists organize the variety in chemical structure by classifying molecules into functional groups.A functional group is a group of atoms that gives a family of molecules its characteristic chemical and physical properties.

Accepted Answer

Both statements are true.Molecules that have similar functional groups have similar properties.In addition to carbon,the combination of different atoms like hydrogen (H),oxygen (O),nitrogen (N),sulfur (S),and phosphorus (P)form biomolecules that provide great variety in chemical structure,properties,and reactivity in biological systems.

Question 16

Cholesterol is the most abundant lipoprotein and is important to biological membranes.Cholesterol is also the precursor of steroid hormones,bile acids,and the lipid-soluble vitamin D.

Accepted Answer

The first statement is false; the second is true.Cholesterol is not a lipoprotein; it belongs to a class of lipids known as steroids.Cholesterol is the most abundant steroid and is an important stabilizing component of biological membranes.The second statement describes other important functions of cholesterol.

Question 17

Which is NOT a characteristic or function of lipids?

Accepted Answer

Lipids are hydrophobic,water-fearing,compounds that do not combine readily with water.In contrast,carbohydrates and proteins are hydrophilic,or water loving.

Question 18

A biomolecule is a substance required by the body that must be supplied by an outside source.During metabolism,energy can be extracted from dietary carbohydrates,proteins,and lipids and can be used to create biomolecules required for life.

Accepted Answer

The first statement is false; the second is true.The first statement is incorrect because it defines a nutrient instead of a biomolecule.Note that with a nutrient,the substance must be supplied from an outside source,typically food.A biomolecule is any molecule that is produced by a living cell or organism,which would include carbohydrates,proteins,nucleic acids,and lipids.

Question 19

Saturated fatty acids are alkenes that contain one or more C=C (double)bond.Unsaturated fatty acids,contain only one C=C bond.

Accepted Answer

Both statements are false.Fatty acids can be classified according to the presence or absence of C=C (double)bonds.Saturated fatty acids contain only C-C (single)bonds while unsaturated fatty acids contain one or more C=C bonds.Saturated fatty acids are called alkenes.Monounsaturated fatty acids such as oleic acid contain just one C=C bond,whereas polyunsaturated fatty acids such as linoleic acid contain more than one C=C bond.

Question 20

Each exemplifies glycosidic bonding reactions,except one.Which is the exception?

Accepted Answer

The monosaccharides glucose and fructose react together to form the disaccharide sucrose.Sucrose is table sugar and is one of the sweetest of the carbohydrates.

Quiz 2: Concepts in Biochemistry