Molecular Biology

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SAT Subject Test in Biology › Molecular Biology

Questions 1 - 10
1

In RNA, three nucleotide bases together determine the amino acid that is added to the growing polypeptide chain during translation. This three base grouping is known as a(n) __________.

codon

gene

operator

promoter

polypeptide

Explanation

The three base grouping in RNA that determines the amino acid created in translation is known as a codon. Gene refers to the region on DNA that codes for a given trait. Operators and promoters are also located on DNA, and act as regulatory elements.

2

Disulfide bonds can add stability to the structure of a protein. The formation of disulfide bonds occurs in the formation of what level of protein structure?

Tertiary

Primary

Secondary

Quaternary

During translation

Explanation

The correct answer is "tertiary." Translation is a process performed by ribosomes to link amino acids together in a chain, and the order of the amino acids is based on a code from mRNA. The order of the amino acids in the chain is the primary structure. The secondary structure is the folding in that chain, mainly based on hydrogen bonds between parts of the chain and the surrounding water molecules. The tertiary structure is the actual three-dimensional structure of the protein. Disulfide bonds are covalent bonds between cysteine residues and are stronger than hydrogen bonds and give a stable, three-dimensional structure to what was originally just a chain of amino acids.

3

Carbohydrates represent important macromolecules in the biochemical pathways of many organisms.

Which of the following is/are monosaccharide(s)?

I. Glucose
II. Fructose
III. Maltose

I and II

I only

I and III

II and III

I, II, and III

Explanation

Glucose and fructose are monomeric saccharides, or monosaccharides. The carbon to hydrogen to oxygen ratio exists in a 1:2:1 pattern indicative of a monomeric saccharide. The molecular formula of glucose and fructose is . Maltose is a disaccharide composed of two molecules of glucose.

4

Polysaccharides are considered sugar moieties that include 3 or more monomeric saccharides together.

Which of the following is/are polysaccharide(s)?

I. Glycogen
II. Starch
III. Cellulose

I, II, and III

I only

I and II

I and III

II and III

Explanation

Glycogen, starch, and cellulose are all polysaccharides composed of many glucose monomers linked together.

5

The lac operon is an inducible operon. Which of the following best describes this type of operon?

The operon is usually off and has an active repressor

The operon is usually off and has an inactive repressor

The operon is usually on and has an active repressor

The operon is usually on and has an inactive repressor

None of these

Explanation

With an inducible system, the operon is off, meaning its repressor is active, or actively repressing the system from turning on. Inducible operons are opposite to a repressible operon, which is always on until it is repressed.

6

Carbohydrates represent important macromolecules in the biochemical pathways of many organisms.

Which of the following is/are monosaccharide(s)?

I. Glucose
II. Fructose
III. Maltose

I and II

I only

I and III

II and III

I, II, and III

Explanation

Glucose and fructose are monomeric saccharides, or monosaccharides. The carbon to hydrogen to oxygen ratio exists in a 1:2:1 pattern indicative of a monomeric saccharide. The molecular formula of glucose and fructose is . Maltose is a disaccharide composed of two molecules of glucose.

7

In RNA, three nucleotide bases together determine the amino acid that is added to the growing polypeptide chain during translation. This three base grouping is known as a(n) __________.

codon

gene

operator

promoter

polypeptide

Explanation

The three base grouping in RNA that determines the amino acid created in translation is known as a codon. Gene refers to the region on DNA that codes for a given trait. Operators and promoters are also located on DNA, and act as regulatory elements.

8

In which of the following molecular forms do animals store energy?

Lipids and glycogen

Lipids only

Glycogen only

Glycogen and peptidoglycan

Peptidoglycan only

Explanation

Both lipids (fat) and glycogen (made up of glucose molecules) store energy in animals. Lipids are used for long-term energy storage while glycogen, found in the liver and muscles, is used for short-term energy storage. Peptidoglycan is the molecule that makes up the bacterial cell walls.

9

Polysaccharides are considered sugar moieties that include 3 or more monomeric saccharides together.

Which of the following is/are polysaccharide(s)?

I. Glycogen
II. Starch
III. Cellulose

I, II, and III

I only

I and II

I and III

II and III

Explanation

Glycogen, starch, and cellulose are all polysaccharides composed of many glucose monomers linked together.

10

Disulfide bonds can add stability to the structure of a protein. The formation of disulfide bonds occurs in the formation of what level of protein structure?

Tertiary

Primary

Secondary

Quaternary

During translation

Explanation

The correct answer is "tertiary." Translation is a process performed by ribosomes to link amino acids together in a chain, and the order of the amino acids is based on a code from mRNA. The order of the amino acids in the chain is the primary structure. The secondary structure is the folding in that chain, mainly based on hydrogen bonds between parts of the chain and the surrounding water molecules. The tertiary structure is the actual three-dimensional structure of the protein. Disulfide bonds are covalent bonds between cysteine residues and are stronger than hydrogen bonds and give a stable, three-dimensional structure to what was originally just a chain of amino acids.

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