Quiz on Water in Biochemistry

Why does water have a higher melting and boiling point than other common solvents?

• It has a low molecular weight

• It lacks hydrogen bonding

• Hydrogen bonding between molecules increases cohesion

• Water molecules repel each other

What type of bond is responsible for the high cohesion in water molecules?

• Covalent bond

• Ionic bond

• Hydrogen bond

• Van der Waals force

How many hydrogen bonds can a water molecule form?

• 2

• 3

• 4

• 5

Why does ice float on liquid water?

• Ice is denser than liquid water

• Ice has a crystalline structure with maximum hydrogen bonds, making it less dense

• Water molecules in ice are more tightly packed

• The surface tension of water repels ice

What is the main role of hydrogen bonds in proteins?

• Stabilizing alpha helices and beta sheets

• Breaking down peptide bonds

• Reducing protein solubility

• Preventing protein folding

Which of the following is NOT stabilized by hydrogen bonds?

• DNA double helix

• Phospholipid bilayer

• Ionic bonds in NaCl

• Enzyme-substrate binding

Molecules that do not interact well with water and repel it are called:

• Hydrophilic

• Amphipathic

• Hydrophobic

• Polar

How does water dissolve NaCl?

• By breaking covalent bonds in NaCl

• By forming hydrogen bonds with Na+ and Cl- ions

• By increasing its boiling point

• By decreasing its surface tension

Which of the following gases is least soluble in water?

• Oxygen

• Carbon dioxide

• Nitrogen

• Ammonia

What is an amphipathic compound?

• A molecule with only hydrophilic regions

• A molecule with both hydrophilic and hydrophobic regions

• A completely nonpolar molecule

• A molecule that ionizes completely in water