AP Biology Unit 1 Topic 1.3: Macromolecules, Monomers, Polymers, Dehydration Synthesis and Hydrolysis

Question 1

What are the four major classes of biological macromolecules?

Accepted Answer

The four major classes are carbohydrates, lipids, proteins, and nucleic acids. Each class has distinct monomer building blocks, characteristic structures, and biological functions. Three of these classes — carbohydrates, proteins, and nucleic acids — are built from monomers joined into polymers, while lipids are not true polymers.

Question 2

What is the difference between a monomer and a polymer?

Accepted Answer

A monomer is a single small molecule that serves as a building block, while a polymer is a long chain of many monomers linked together. For example, glucose is a monomer of starch, amino acids are monomers of proteins, and nucleotides are monomers of DNA.

Question 3

What is dehydration synthesis?

Accepted Answer

Dehydration synthesis is the chemical reaction that joins two monomers together by removing a water molecule. One monomer loses a hydroxyl group while the other loses a hydrogen, and these atoms combine to release water. This is how cells build polymers like proteins, polysaccharides, and nucleic acids.

Question 4

What is hydrolysis?

Accepted Answer

Hydrolysis is the reverse of dehydration synthesis: it breaks a polymer into smaller units by adding a water molecule. The water splits and donates a hydroxyl group to one fragment and a hydrogen to the other. Digestion in animals relies entirely on hydrolysis to break down food macromolecules.

Question 5

What enzymes are involved in dehydration synthesis and hydrolysis?

Accepted Answer

Specific enzymes catalyze each reaction. For example, DNA polymerase catalyzes dehydration synthesis to build DNA from nucleotides, while amylase catalyzes the hydrolysis of starch into glucose. Each macromolecule type has its own family of enzymes for synthesis and breakdown.

Question 6

Why does building macromolecules require energy?

Accepted Answer

Building macromolecules through dehydration synthesis requires energy because the process forms new covalent bonds, which is thermodynamically unfavorable on its own. Cells supply this energy through ATP and other energy carriers. Hydrolysis, by contrast, releases energy because it breaks bonds.

Question 7

What does the principle of structure determines function mean?

Accepted Answer

Structure determines function is one of the central themes of biology. The shape of a molecule determines what it can bind to and what reactions it can catalyze or participate in. A protein with the wrong shape cannot do its job, which is why mutations that alter protein structure can cause disease.

Question 8

How are macromolecules involved in storing energy and information?

Accepted Answer

Carbohydrates and lipids store chemical energy in their bonds. Nucleic acids store and transmit genetic information through the sequence of their nucleotide bases. Proteins do not primarily store energy or information but execute most cellular work, from catalysis to structure to signaling.

Question 9

Why are macromolecules considered polymers of life?

Accepted Answer

Macromolecules are called polymers of life because they are the largest and most functionally important molecules in living organisms. Their ability to form from a small set of monomers in nearly endless combinations is what allows life to be so diverse and complex while using relatively few building blocks.

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