MCAT · Biology 1 · Chapter 1 · Section 1.2

Chapter 1: Biological Molecules and Enzymes

Section 1.2: Water

STUDY

Question 1:
Name 3 roles of water in chemical reactions of living cells.
→ Solvent, reactant, product

Question 2:
What property of water makes it a perfect solvent for chemical reactions in the body?
→ Polarity

Question 3:
Due to polarity and H-bonding, water is allow to:
→ Pull apart polar molecules or ions and form ordered networks around them
     Force non-polar molecules to congregate (= aggregate = agglutinate) together

Question 4:
What percent of cell's mass does water take up?
→ 70 to 80 percent

Question 5:
What differentiates water from most other compounds that are just as light as water, in regards to their states at typical cell temperatures (= in cellular environment)?
→ Water remains in liquid state, while others exist as gas.

Question 6:
How does water remain in liquid state in cellular environment?
→ H-bonding between water molecules, which elevates boiling point

Question 7:
How does water "squeeze" hydrophobic molecules away and cause these molecules to aggregate?
→ Strong cohesive forces between water molecules, which are provided by H-bonding

Question 8:
What allows water to support the raft spider (a species that can walk on water without sinking)?

(Source: https://c1.staticflickr.com/1/82/237875014_4d579d57c5_z.jpg?zz=1)

→ Cohesive forces created by H-bonding between water molecules 

Question 9:
How do hydrophilic molecules or ionic compounds dissolve easily in water?
→ Molecules' or compounds' (-) charged ends are attracted to partial positive charge (δ+) of
     water's Hydrogens, while (+) charged ends are attracted to partial negative charge (δ-) of
     water's Oxygen.

Question 10:
Water surrounds a hydrophilic molecule or ion. Which one is solvent and which one is solvate?
→ Solvent: water
     Solvate: hydrophilic molecule or ion

Question 11:
In living cells, what reaction and what process break macromolecules apart? Briefly explain the reaction.
→ Reaction: hydrolysis, breaking macromolecule into 2 smaller molecules by adding H and OH of
     water to either end
     Process: digestion

Question 12:
Hydrolysis of which molecule provides the body's major source of energy?
→ ATP

Question 13:
In living cells, mostly what reaction forms macromolecules? Briefly explain the reaction. What's the byproduct?
→ Reaction: dehydration, when 2 molecules are combined to form a larger molecule
     Byproduct: water

Question 14:
Dehydration is the reverse reaction of what reaction?
→ Hydrolysis

Question 15:
Between hydrolysis and dehydration: Which forms bonds and which breaks bonds? Which gains water and which loses water?
→ Hydrolysis breaks and gains. Dehydration forms and losses.

Question 16:
Dehydration allows formation of _____ bonds that make up proteins and _____ bonds that make up triglycerides.
→ Proteins: peptide bonds
     Triglycerides: ester bonds

PRACTICE

Question 1:
Name 3 roles of water in chemical reactions of living cells.

Question 2:
What property of water makes it a perfect solvent for chemical reactions in the body?

Question 3:
Due to polarity and H-bonding, water is allow to:

Question 4:
What percent of cell's mass does water take up?

Question 5:
What differentiates water from most other compounds that are just as light as water, in regards to their states at typical cell temperatures (= in cellular environment)?

Question 6:
How does water remain in liquid state in cellular environment?

Question 7:
How does water "squeeze" hydrophobic molecules away and cause these molecules to aggregate?

Question 8:
What allows water to support the raft spider (a species that can walk on water without sinking)?

(Source: https://c1.staticflickr.com/1/82/237875014_4d579d57c5_z.jpg?zz=1)

Question 9:
How do hydrophilic molecules or ionic compounds dissolve easily in water?

Question 10:
Water surrounds a hydrophilic molecule or ion. Which one is solvent and which one is solvate?

Question 11:
In living cells, what reaction and what process break macromolecules apart? Briefly explain the reaction.

Question 12:
Hydrolysis of which molecule provides the body's major source of energy?

Question 13:
In living cells, mostly what reaction forms macromolecules? Briefly explain the reaction. What's the byproduct?

Question 14:
Dehydration is the reverse reaction of what reaction?

Question 15:
Between hydrolysis and dehydration: Which forms bonds and which breaks bonds? Which gains water and which loses water?

Question 16:
Dehydration allows formation of _____ bonds that make up proteins and _____ bonds that make up triglycerides.

ANSWER KEY

Question 1:
→ Solvent, reactant, product

Question 2:
→ Polarity

Question 3:
→ Pull apart polar molecules or ions and form ordered networks around them
     Force non-polar molecules to congregate (= aggregate = agglutinate) together

Question 4:
→ 70 to 80 percent

Question 5:
→ Water remains in liquid state, while others exist as gas.

Question 6:
→ H-bonding between water molecules, which elevates boiling point

Question 7:
→ Strong cohesive forces between water molecules, which are provided by H-bonding

Question 8:
→ Cohesive forces created by H-bonding between water molecules

Question 9:
→ Molecules' or compounds' (-) charged ends are attracted to partial positive charge (δ+) of
     water's Hydrogens, while (+) charged ends are attracted to partial negative charge (δ-) of
     water's Oxygen.

Question 10:
→ Solvent: water
     Solvate: hydrophilic molecule or ion

Question 11:
→ Reaction: hydrolysis, breaking macromolecule into 2 smaller molecules by adding H and OH of
     water to either end
     Process: digestion

Question 12:
→ ATP

Question 13:
→ Reaction: dehydration, when 2 molecules are combined to form a larger molecule
     Byproduct: water

Question 14:
→ Hydrolysis

Question 15:
→ Hydrolysis breaks and gains. Dehydration forms and losses.

Question 16:
→ Proteins: peptide bonds
     Triglycerides: ester bonds