What is the densest part of an atom that has the greatest amount of the mass of the atom?

1. electron cloud.
2. electron shell.
3. atomic nucleus.
4. orbit.

3. atomic nucleus.

What makes up the atomic number of an element?

1. electrons + protons.
2. protons.
3. neutrons.
4. neutrons + protons.

2. protons

What makes up the atomic weight of an element?

1. electrons + neutrons.
2. protons.
3. electrons.
4. neutrons + protons.

4. neutrons + protons.

How many electrons are in a neutral atom?

1. The same number as the neutrons in the atom.
2. The same number as the protons in the atom.
3. The same number as the neutrons plus the protons.
4. You can't tell, it varies from one atom to the next.

2. The same number as the protons in the atom.

What is the difference between ions and atoms of an element?

1. number of electrons they possess.
2. placement of their neutrons.
3. number of neutrons they possess.
4. number of protons in the atomic nucleus.

1. number of electrons they possess.

What do you get when an atom gains an electron?

1. An isotope.
2. A cation.
3. An anion.
4. An ionic bond.

3. An anion.

Carbon enters into an enormous number and variety of chemical combinations partly because

1. it has four electrons in its outer shell.
2. it has no protons in its nucleus.
3. it is part of a protein molecule.
4. it forms isotopes.

1. it has four electrons in its outer shell.

What is an inert element?

1. An element where the proton number and neutron number are equal.
2. An element where the atomic number is higher than its atomic weight.
3. An element that forms ions occurs readily.
4. An element where the outer shell will not hold additional electrons.

4. An element where the outer shell will not hold additional electrons.

The formation of a chemical bond that combines atoms in molecules depends in large measure on the

1. number of neutrons.
2. placement of electrons in the shells.
3. presence of organic matter in the environment.
4. proton configuration of the nucleus.

2. placement of electrons in the shells.

What happens in the formation of an ionic bond?

1. the addition of neutrons.
2. a loss of protons.
3. a transfer of electrons.
4. All of the above are correct.

3. a transfer of electrons.

What happens when two oppositely-charged atoms are attracted and are held together?

1. They form a covalent bond.
2. They form a hydrogen bond.
3. They form an ionic bond.
4. They form a strong bond.

3. They form an ionic bond.

What happens when a chemical bond is formed between the electropositive sodium ion and the electronegative chloride ion?

1. A covalent bond forms.
2. A hydrogen bond forms.
3. A biological bond forms.
4. An ionic bond forms.

4. An ionic bond forms.

What is the result of two or more atoms joining together?

1. An isomer.
2. An isotope.
3. An ionic bond.
4. A molecule.

4. A molecule.

What kind of bond is found in water, H₂O?

1. It has a hydrogen bond.
2. It has a polar covalent bond.
3. It has a nonpolar covalent bond.
4. It has an ionic bond.

2. It has a polar covalent bond.

Which one of the following statements does not apply to hydrogen bonds?

1. They form between water molecules.
2. They involve H and O atoms.
3. They are very strong bonds.
4. They are important in the formation of proteins and nucleic acids.

3. They are very strong bonds.

All the following characterize hydrogen bonding except

1. a strong and stable chemical force.
2. an attraction between nitrogen and hydrogen atoms.
3. the force between water molecules.
4. the shaping of proteins and nucleic acids.

1. a strong and stable chemical force.

In the chemical reaction A + B => AB, which are the reactants?

1. A
2. B
3. AB
4. A and B

4. A and B

What happens in a dehydration or synthesis reaction?

1. water is removed in the formation of a covalent bond.
2. monosaccharides are produced from polysaccharides.
3. water is incorporated into a molecule.
4. water is removed from a bacterial cell.

1. water is removed in the formation of a covalent bond.

An acid is a chemical substance that

1. releases protons in solution.
2. has a sour taste.
3. has a lower pH value.
4. All the above are correct.

4. All the above are correct.

A substance whose pH is 8 contains

1. more hydroxyl ions than water.
2. less protein than water.
3. no hydrogen ions.
4. more hydrogen ions than water.

1. more hydroxyl ions than water.

Why is a buffer important?

1. It maintains a neutral pH inside the cells.
2. It maintains a neutral pH outside the cells.
3. It maintains a stable pH in living things.
4. It isn't really very important, most cells don't have it.

3. It maintains a stable pH in living things.

Which one of the following is not an organic molecule?

1. Table salt
2. Nucleic acids
3. Glucose
4. Deoxyribose

1. Table salt

The carboxyl group is important biologically. What is its chemical formula?

1. —OH.
2. —COOH.
3. —CHO.
4. —NH₂.

2. —COOH.

What is a functional group symbolized by –NH₂ known as?

1. hydroxyl group.
2. phosphate group.
3. amino group.
4. carboxyl group.

3. amino group.

What is an important difference between monosaccharides and polysaccharides?

1. the number of nitrogen atoms in the molecule.
2. the presence of glycerol in monosaccharides.
3. the number of carbohydrate monomers in the molecule.
4. the specific amino acids present.

3. the number of carbohydrate monomers in the molecule.

Carbohydrates are so named because

1. they contain carbon and hydrogen.
2. the numbers of carbon and hydrogen atoms are the same.
3. they react readily with water.
4. they can be hydrolyzed by the enzymes contained in water.

1. they contain carbon and hydrogen.

Glucose units may be linked in chains of hundreds or thousands in

1. proteins.
2. nucleic acids such as DNA.
3. polysaccharides.
4. disaccharides.

3. polysaccharides.

Fatty acids that contain many double bonds and lack hydrogen atoms are commonly said to be

1. saturated.
2. glycerol.
3. denatured.
4. polyunsaturated.

4. polyunsaturated.

Guanine and cytosine are important constituents of

1. most acid solutions.
2. the chromosome of a cell.
3. most protein molecules.
4. the cellular membrane.

2. the chromosome of a cell.

. All the following are components of a RNA molecule except

1. cytosine.
2. ribose.
3. thymine.
4. uracil

1. thymine.

Nucleic acids are composed of all the following except

1. phosphate.
2. carbohydrate.
3. amino acids.
4. nitrogenous bases.

3. amino acids.

What nucleotide is a universal form of energy for cells?

1. ATP
2. glucose
3. ribose
4. deoxyribose

1. ATP

The peptide bond is a type of covalent bond that forms

1. in DNA.
2. only if ions are present.
3. between amino acids.
4. within water molecules.

3. between amino acids.

In the formation of proteins, ______react with one another to form a linkage called a(n) ______.

1. fatty acids, peptide bond
2. glycerol molecules, ionic bond
3. amino acids, ionic bond
4. amino acids, peptide bond

4. amino acids, peptide bond

Which one of the following is not associated with proteins?

1. Nitrogen-containing amino acids
2. Peptide bonds
3. Primary and secondary structures
4. Saturated fatty acids

4. Saturated fatty acids

There are ________ amino acids that build proteins.

1. four
2. twelve
3. twenty
4. sixty four

3. twenty

The sequence of amino acids in a protein is referred to as its

1. primary structure.
2. secondary structure.
3. tertiary structure.
4. quaternary structure.

1. primary structure.

Which one of the following is not found in the secondary structure of proteins?

1. Random coil
2. Pleated sheet
3. Disulfide bridge
4. Alpha helix

3. Disulfide bridge

The tertiary structure of a protein is determined by the folding back on itself and forming of ionic and hydrogen bonds between the

1. amino groups
2. R groups
3. phosphate groups
4. carboxyl groups

2. R groups

A denatured protein is one that

1. has lost its three dimensional structure.
2. has reverted to a carbohydrate.
3. lacks amino acids.
4. lacks covalent bonds.

1. has lost its three dimensional structure.

Which of the following organic elements is the most abundant in microorganisms?

1. carbohydrates
2. lipids
3. protein
4. nucleic acids

3. protein