biology practice exam

The acceptance of scientific discoveries, hypotheses, or theories is based on

evidence

The present system of biological classification contains three Domains of life. Which of the following does not belong to any of the three Domains?

coronavirus

What do the four elements most abundant in life-carbon, oxygen, hydrogen, and nitrogen-have in common?

they all have unpaired electrons in their valence shells

A Sodium ion (Na+) has 10 electrons, 11 protons, and 12 neutrons. Its atomic mass and atomic number, respectively, are

23 and 11

How many electrons does oxygen have in its valence shell, and how many electrons does sulfur have in its valence shell?

6.6

Which of the following determines the identity of element 6 (Carbon, C)?

the 6 protons in the nucleus of carbon

Water is able to form hydrogen bonds because

the bonds that hold together the atoms in a water molecule are polar covalent bonds

What types of bonds are identified in the illustration below of a water molecule interacting with an ammonia molecule?

bonds 1 and 3 are polar covalent bonds and bond 2 is a hydrogen bond

Acid rain has lowered the pH of a particular lake to 4.0. What is the hydrogen ion concentration of the lake?

10^-4 M

Which bonds must be broken for water to boil?

hydrogen bonds

A 1 liter solution contains 10-8 moles of [H+] ions. Which of the following best describes the chemical properties and the pH of this solution?

basic, pH 8

Select all that apply: From its atomic number of 15, one can conclude that the phosphorus atom has

15 protons and 15 electrons

Which property of the carbon atom C gives it compatibility with a greater number of different elements than O, H, or N?

carbon has a valence of 4

Fluorine has an atomic number of 9 and a mass number (p + n) of 19. How many electrons are needed to complete the valence shell of a fluorine atom?

1

Which of the following solutions would require the greatest amount of base to be added to bring the solution to neutral pH?

stomach acid (pH 2)

What describes the relationship between these two sugar molecules?

structural isomers

Polysaccharides, lipids, and proteins are similar in that they

are synthesized from monomers by dehydration reactions

Select all that apply: When 2 glucose molecules are linked together:

a glycosidic bind is formed, a condensation reaction occurred to join them, and the enzyme maltase could hydrolyze this disaccharide back to 2 glucose molecules

The molecule shown in at right is a

saturated fatty acids

(Think carefully!) Upon chemical analysis, a particular protein was found to contain 100 amino acids. How many peptide bonds are present in this protein?

99

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

the double bonds form a kink in the fatty acid tail, forcing adjacent lipids to be further apart

Select all that apply: If cells are grown in a medium containing radioactive15N, which of these molecules will be labeled?

nucleic acids and proteins

(Think carefully!) The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?

C18 H32O16

Normal hemoglobin is a tetramer, consisting of two molecules of β-hemoglobin and two molecules of α-hemoglobin. In sickle-cell disease, a single nucleotide change at the DNA level results in a single amino acid change. This results in hemoglobin tetramers that associate with each other and assemble into large fibers rather than tetramers. Based on this information alone, we can conclude that sicklecell hemoglobin exhibits:

altered 1 ° and altered 4° structure: 2° and 3° may or may not be altered

A ß-pleated sheet is formed when parallel strands of a protein chain are joined by hydrogen bonds. This is an example of:

secondary structure

The process illustrated in the figure below is called

hydrolysis

Select all that apply: The following nucleotide (at right):

could be used to make RNA and has a purine base

The chart below shows the R groups of 6 different amino acids. Which of these amino acid R groups would be soluble in water?

2 and 4, since they are charged and 1 and 5 since they have polar functional groups