BIO EXAM 1

What is the difference between an element and a compound?

Answer: An element contains only one type of atom; a compound contains two or more different elements chemically bonded together.

2. Which subatomic particle determines an element's identity?

Protons

3. Why do electrons farther from the nucleus have more potential energy?

Answer: They experience less attraction from the positively charged nucleus.

4. What are valence electrons?

Answer: The electrons in the outermost shell that participate in chemical bonding.

5. How does a nonpolar covalent bond differ from a polar covalent bond?

Answer: Nonpolar bonds share electrons equally, while polar bonds share electrons unequally.

6. How is an ionic bond formed?

Answer: One atom transfers electrons to another, creating oppositely charged ions that attract each other.

7. Why are hydrogen bonds important in biology?

Answer: They stabilize structures such as DNA and proteins while allowing flexibility.

8. Why do organisms need both strong and weak bonds?

Answer: Strong bonds provide stability, while weak bonds allow reversible biological interactions.

9. What is chemical equilibrium?

Answer: A condition in which forward and reverse reactions occur at the same rate.

10. Does chemical equilibrium mean reactions stop?

Answer: No. Reactions continue, but the rates of the forward and reverse reactions are equal.

1. Why is water considered a polar molecule?

Answer: Oxygen attracts electrons more strongly than hydrogen, creating partial positive and negative regions.

2. How many hydrogen bonds can one water molecule form?

Answer: Four.

3. What four emergent properties result from hydrogen bonding?

Answer: Cohesion, temperature moderation, expansion upon freezing, and solvent versatility.

4. What is the difference between cohesion and adhesion?

Answer: Cohesion is attraction between water molecules; adhesion is attraction between water and other substances.

5. Why does water move upward through plants?

Answer: Cohesion holds water molecules together, while adhesion helps water stick to xylem walls.

6. How is heat different from temperature?

Answer: Heat is total thermal energy; temperature is average molecular kinetic energy.

7. Why does ice float?

Answer: Ice is less dense than liquid water because hydrogen bonds keep water molecules farther apart.

8. What are the products of water dissociation?

Answer: H⁺ and OH⁻.

9. What is the pH of pure water?

Answer: 7.

10. How does the bicarbonate buffer system stabilize blood pH?

Answer: It absorbs excess H⁺ when blood becomes acidic and releases H⁺ when blood becomes basic.

1. Why can carbon form large complex molecules?

Answer: Carbon has four valence electrons and can form four covalent bonds with many different atoms, including other carbon atoms.

2. What factors can vary in a carbon skeleton?

Answer: Length, branching pattern, location of double bonds, and ring structures.

3. Why are hydrocarbons hydrophobic?

Answer: Their C-H bonds are nonpolar and cannot form hydrogen bonds with water.

4. What is a structural isomer?

Answer: Molecules with the same molecular formula but different arrangements of atoms.

5. Which functional group acts as an acid?

Answer: Carboxyl group (–COOH).

6. Which functional group acts as a base?

Answer: Amino group (–NH₂).

7. Which functional group is responsible for ATP's energy-transfer function?

Answer: Phosphate group.

8. What are the three components of ATP?

Answer: Adenine, ribose, and three phosphate groups.

9. What reaction releases energy from ATP?

Answer:

ATP + H₂O → ADP + Pi + Energy

10. Why is ATP called the energy currency of the cell?

Answer: It transfers usable energy from energy-releasing reactions to energy-requiring cellular processes.

1. What are the four major classes of macromolecules?

Answer: Carbohydrates, lipids, proteins, and nucleic acids.

2. What is the difference between a monomer and a polymer?

Answer: A monomer is a single molecular building block; a polymer consists of many monomers linked together.

3. What bond joins monosaccharides?

Answer: A glycosidic linkage.

4. What are the building blocks of fats?

Answer: Glycerol and three fatty acids.

5. What is the principal storage carbohydrate in animals?

Answer: Glycogen.

6. What determines a protein's primary structure?

Answer: The amino acid sequence encoded by DNA.

7. What maintains secondary protein structure?

Answer: Hydrogen bonds.

8. Name four causes of protein denaturation.

Answer: Heat, extreme pH, high salt concentration, and chemicals.

9. What are the three components of a nucleotide?

Answer: Phosphate group, sugar, and nitrogenous base.

10. What is the shape of DNA?

Answer: A double helix.