BIO 2024/2214 Tutorial 1

Which of the following statements about RNA in the "RNA World" hypothesis is true?

• RNA can only store genetic information but cannot catalyze chemical reactions.

• RNA is primarily involved in protein synthesis and does not play any other roles in cells.

• In primitive cells, RNA could replicate itself and perform biochemical functions without the need for proteins.

• DNA was the first genetic material, and RNA evolved later to assist in DNA replication.

Which condition was essential for the abiotic synthesis of biomolecules on early Earth, according to the Double-Origin theory?

• The presence of a thick ozone layer to protect organic molecules from UV radiation.

• High oxygen levels in the Earth's atmosphere.

• The reaction of simple compounds in the Earth's oceans or on clay surfaces.

• The exclusive use of DNA as the first genetic material.

In the Gibbs free energy equation, a reaction is considered spontaneous when

• Both enthalpy (ΔH) and entropy (ΔS) increase.

• Entropy (ΔS) decreases and enthalpy (ΔH) remains unchanged.

• Enthalpy (ΔH) decreases and entropy (ΔS) increases.

• Temperature (T) decreases while both enthalpy (ΔH) and entropy (ΔS) increase.

The formation of cell membranes was crucial in the origin of life because

• Membranes allowed cells to exchange genetic material freely with their environment.

• Membranes enabled cells to store energy in the form of ATP.

• Membranes separated cells from their environment, allowing internal biochemical reactions to be regulated.

• Membranes facilitated the synthesis of complex biomolecules from simple inorganic molecules.

What is the primary reason water molecules form hydrogen bonds with each other?

• Water is a nonpolar molecule

• Water contains ions that attract each other

• Water molecules have polar covalent bonds leading to partial charges

• Water molecules are amphipathic

Which of the following bonding/interactions is the weakest ?

• Hydrogen Bond

• Ion-dipole interaction

• Dipole-dipole interaction

• Dipole-induced dipole interaction

According to the Henderson-Hasselbalch equation, when the concentration of a weak acid equals the concentration of its conjugate base, what is the relationship between pH and pKa?

• pH is greater than pKa

• pH is less than pKa

• pH equals pKa

• pKa becomes zero

Which of the following best describes why CO2, despite having polar bonds, is considered a nonpolar molecule?

• The geometry of the molecule cancels out dipole moments

• The electronegativity difference between carbon and oxygen is minimal

• CO2 does not participate in hydrogen bonding

• CO2 forms ionic bonds in solution

Which of the following acids would have the lowest pH in a solution at the same concentration?

• • Hydrochloric acid (HCl) with Ka = 1.3 × 10^6

• Acetic acid (CH3COOH) with Ka = 1.8 × 10^-5

• Carbonic acid (H2CO3) with Ka = 4.3 × 10^-7

• Phosphoric acid (H3PO4) with Ka = 7.5 × 10^-3

What happens to a buffer solution if a small amount of strong base (OH⁻) is added?

• The pH changes drastically

• The weak acid reacts with the OH⁻, minimizing the pH change

• The conjugate base forms more acid, sharply lowering the pH

• The buffer completely neutralizes the base, with no change in pH