Chapter 3 Review: Synthesis of Biological Macromolecules (OpenStax Biology 2e)

A comprehensive set of practice questions covering Chapter 3.1–3.5: macromolecule synthesis, carbohydrates, lipids, proteins, and nucleic acids. Includes definitions, processes, structures, and key distinctions.

What are biological macromolecules?

Large, complex molecules built from smaller subunits (monomers) and essential to life; include carbohydrates, lipids, proteins, and nucleic acids.

What are the four classes of macromolecules?

Carbohydrates, lipids, proteins, and nucleic acids.

What happens during dehydration synthesis?

A water molecule is removed to join monomers, forming a covalent bond (condensation reaction).

What happens during hydrolysis?

A water molecule is added to break covalent bonds, splitting polymers into monomers.

What can speed up dehydration synthesis and hydrolysis reactions?

Enzymes (biological catalysts) speed up both processes.

What is the ratio of carbon to hydrogen in carbohydrates (empirical formula)?

Approximately CH2O (1:2:1 ratio, repeated units).

What is the most common monosaccharide?

Glucose.

Most monosaccharide names end in which suffix?

-ose.

Glucose is used during which process: cellular respiration or photosynthesis?

Cellular respiration.

Excess glucose is stored as what in plants?

Starch.

Why are glucose and fructose considered isomers?

They have the same molecular formula but different structural arrangements.

How are disaccharides formed?

Two monosaccharides linked by dehydration synthesis (glycosidic bond) with release of water.

Name two common disaccharides.

Sucrose and lactose.

What is a polysaccharide?

A polymer made of many monosaccharide units.

Why is starch found in seeds?

Starch serves as an energy reserve to fuel germination.

What is amylase?

An enzyme that digests starch into sugars.

How do animals store glucose?

As glycogen in liver and muscle tissues.

What is a plant’s cell wall made from?

Cellulose.

How do grazing animals break down cellulose?

Microbes in the gut (e.g., rumen) produce cellulase to digest cellulose.

Carbohydrates from what structural component of insects and crustaceans?

Chitin.

Which of the following are benefits of carbohydrates in the diet? (check all that apply)

Reduces cholesterol in the blood; Promotes regular bowel movements; Reduces the amount of sugar circulating in blood.

Lipids tend to be which in water: polar/nonpolar and soluble/insoluble?

Nonpolar and insoluble.

What are the two main components of a fat molecule?

Glycerol and fatty acids.

If a fatty acid contains only single bonds, what is it called? If it contains a double bond, what is it called?

Single bonds: saturated; double bonds: unsaturated.

Unsaturated fats are solid or liquid at room temperature?

Liquid.

What type of cells store fat in animals?

Adipocytes (fat cells).

What are examples of unsaturated fats?

Olive oil, canola oil, and most fish oils.

Why are trans fats banned in some places?

They raise the risk of heart disease by affecting cholesterol levels (increasing LDL and decreasing HDL).

What is a common dietary source of Omega-3 fatty acids?

Fatty fish (e.g., salmon) and certain plant oils (e.g., flaxseed).

Why do aquatic birds and leaves have a waxy covering?

To provide waterproofing and reduce water loss.

Where are phospholipids found?

In cell membranes (phospholipid bilayer).

Why are phospholipids described as amphipathic?

They have hydrophilic (water-loving) heads and hydrophobic (water-fearing) tails.

How many carbon rings are found in a steroid?

Four fused rings.

What is a catabolic enzyme?

An enzyme that catalyzes the breakdown of molecules (digestion).

Match the protein with its function: Amylase

Digestive enzyme that breaks down starch.

Match the protein with its function: Hemoglobin

Transport, carries substances in the blood.

Match the protein with its function: Keratin

Structural component.

Match the protein with its function: Immunoglobulins

Protect from foreign pathogens (immune defense).

What happens when a protein is denatured?

Its structure and function are lost due to disruption (e.g., heat, pH changes).

Proteins are made from what monomers?

Amino acids.

The nature of the amino acid (polarity, acidity) is determined by what part?

The R group (side chain) of the amino acid.

Why are some amino acids considered essential?

Humans cannot synthesize them; they must be obtained from the diet.

What type of bond joins amino acids together?

Peptide bonds.

The N terminus of a polypeptide contains which group? The C terminus contains which group?

N terminus: amino group; C terminus: carboxyl group.

Where is Cytochrome c found? How many amino acids are in human cytochrome c?

Found in mitochondria; about 104 amino acids.

Differences in the cytochrome c sequence can provide clues about which?

Evolutionary relationships, protein function, and a common ancestor.

Enzymes bind to a specific what?

Substrate.

The sequence of amino acids in a polypeptide chain is its what structure?

Primary structure.

Sickle cell anemia is caused by a single change in what protein chain?

Beta chain of hemoglobin.

This change causes hemoglobin molecules to form what, distorting the blood cell?

Long fibers/polymers that distort the red blood cell.

What are the two secondary structures of proteins?

Alpha helix and beta-pleated sheet.

The three-dimensional structure of a protein is called its what structure?

Tertiary structure.

The nature of the R groups causes the protein to do what: fold or dismantle?

Fold.

Quaternary structures are formed from several what?

Polypeptide chains (subunits).

What can cause a protein to denature?

Heat, pH changes, salt concentration, or other harsh conditions.

Why are nucleic acids important for the continuity of life?

They store and transmit genetic information (DNA) and participate in protein synthesis (RNA).

Where is DNA found in eukaryotic cells?

In the nucleus (also in mitochondria and chloroplasts in some cells).

The cell’s entire genetic content is its what?

Genome.

In eukaryotes, DNA and histone proteins form what?

Chromatin.

RNA is mostly involved in which cellular process?

Protein synthesis (translation; transcription is also essential).

DNA and RNA are composed of what monomers?

Nucleotides.

What are the three components of a nucleotide?

A sugar, a phosphate group, and a nitrogenous base.

What are the four bases found in DNA?

Adenine, thymine, cytosine, guanine.

Purines have how many rings?

Two rings.

Pyrimidines have how many rings?

One ring.

Adenine and guanine are classified as what?

Purines.

Cytosine and thymine are classified as what?

Pyrimidines.

What sugar is found in DNA? What sugar is found in RNA?

DNA: deoxyribose; RNA: ribose.

What is the difference between these sugars?

DNA lacks the 2' hydroxyl group; RNA has a 2' hydroxyl group.

What is the shape of a DNA molecule?

Double helix.

If DNA has the sequence A A T T G C, what is the complementary RNA sequence?

U U A A C G.

A set of three bases is called a what?

Codon.

What is the smallest of the four types of RNA?

tRNA.

DNA dictates the structure of RNA through which process?

Transcription.

RNA dictates the structure of protein through which process?

Translation.

On the diagram, identify: Phosphate, Deoxyribose, Guanine, Cytosine.

Phosphate: phosphate group; Deoxyribose: sugar; Guanine: purine base; Cytosine: pyrimidine base.