Carbohydrates
Lipids
Nucleic Acids
Proteins
100

Complex carbohydrates are described as “sugar polymers.” Name one example, say what monomer it’s built from, and say what its job is in the organism.

  • Starch (plants) or glycogen (animals) are storage polymers of α-glucose. Cellulose and chitin are structural polysaccharides.
  • A full answer names the polysaccharide, its monomer, and its role (storage or structure).
100

Name the components of a phospholipid, and where you would find them.

Hydrophilic head, and hydrophobic tails. Found as a phospholipid bilayer making up cell membranes.
100

Name the three parts of a nucleotide.

A phosphate group, a sugar (ribose or deoxyribose), and a nitrogenous base.

100

Which two functional groups join to form a peptide bond, and what does a carboxyl group in an R group do to the amino acid?

The amino group of one amino acid and the carboxyl group of another. A carboxyl in the R group makes the amino acid acidic and negatively charged.

200

Name the two functional groups found in every sugar and say whether sugars are polar or nonpolar.

Hydroxyl and carbonyl. Both are polar, so sugars are polar.

200

Lipids are “not true polymers” and “not true macromolecules,” yet we group them together. Explain what they have in common and why that trait matters in water.

  • They are all very hydrophobic, with large hydrocarbon parts.
  • They do not mix with water.
  • Fats, phospholipids, and steroids are the main types.
200

Compare purines and pyrimidines. Give the bases in each group and describe how the ring structures differ.

  • Pyrimidines are cytosine, thymine, and uracil, each with one six-membered ring.
  • Purines are adenine and guanine, which are larger, with a six-membered ring fused to a five-membered ring.
  • Thymine is found in DNA and uracil in RNA.
200

Every amino acid shares a common structure but behaves differently. Describe what is shared, what varies, and why the variable part matters.

  • All have an α carbon bonded to an amino group, a carboxyl group, and an R group.
  • The R group varies among amino acids.
  • The R group determines whether the amino acid is polar or nonpolar, acidic, or basic.
300

Describe how two glucose molecules become maltose. Include the name of the reaction, what is released, and the name of the bond that forms.

  • A dehydration reaction removes an OH from one glucose and an H from the other, releasing H₂O.
  • The two sugars are joined by a glycosidic bond, a 1–4 linkage in maltose.
  • Sucrose forms the same way from glucose and fructose, but with a 1–2 linkage.
300

Describe how a fat (triacylglycerol) is assembled. Name its two components, the reaction that joins them, and the linkage that results.

  • It is built from one glycerol and three fatty acids.
  • Dehydration reactions join them, releasing H₂O.
  • Each connection is an ester linkage.
300

Compare DNA and RNA nucleotides. Describe both the sugar difference and the base difference, and explain why “deoxy” is in the name.

  • DNA has deoxyribose, which lacks an oxygen at the 2′ carbon (an H instead of an OH).
  • RNA has ribose.
  • DNA uses thymine and RNA uses uracil.
300

The 20 amino acids are sorted into hydrophobic and hydrophilic groups. Describe how you would classify an amino acid by looking only at its R group.

  • First, is the R group polar or nonpolar? Nonpolar side chains are hydrophobic (9 amino acids).
  • Polar side chains are hydrophilic (6).
  • Charged side chains are also hydrophilic (5): acidic and negatively charged (2) or basic and positively charged (3).
400

α-glucose and β-glucose differ by only one thing. Explain what that difference is and how it leads to starch being coiled but cellulose being straight.

  • They differ in the location of the hydroxyl group above or below the ring.
  • In starch, every α-glucose is oriented the same way, so the chain curves into a helix or coil that is compact and good for storage.
  • In cellulose, each β-glucose is flipped 180° from its neighbor, so the chain stays straight and flat.
400

Compare saturated and unsaturated fats. Cover the bonds, how the tails pack, whether they’re solid or liquid, and an example of each.

  • Saturated fats have no double bonds, pack tightly, and are solid. An example is animal fat, which is stored in fat cells.
  • Unsaturated fats have some double bonds, pack less tightly, and are liquid. Examples are fish and plant oils, and plants store oil in seeds.
  • The cis double bond causes a bend in the tail, which prevents tight packing.
400

Describe how nucleotides are assembled and then joined into a polymer. Include which carbons are involved, the reaction type, and the name of the linkage.

  • The base joins at the 1′ carbon and the phosphate joins at the 5′ carbon of the sugar, by dehydration reactions.
  • In a polymer, the 5′ phosphate of one nucleotide bonds to the 3′ OH of the other.
  • This is a phosphodiester linkage.
400

Distinguish primary, secondary, tertiary, and quaternary structure. For each, state what is interacting or being described.

  • Primary: The order of amino acids in the polypeptide.
  • Secondary: Hydrogen bonds in the backbone form α helices, β pleated sheets.
  • Tertiary: Interactions between R groups (hydrogen bonds, ionic bonds, disulfide bridges, hydrophobic and van der Waals interactions).
  • Quaternary: Bonding among multiple polypeptides.
500

Explain why cellulose is “very tough” while starch is used for energy storage. Connect the shape of each polymer to what happens between chains.

  • Straight cellulose chains lie side by side and hydrogen-bond to each other. They bundle into rigid microfibrils that make up the plant cell wall.
  • Coiled starch is compact and suited to storage for plants.
500

A phospholipid has a head and tails. Explain what each part is made of and how these parts cause phospholipids to form a bilayer in water.

  • The head contains choline, phosphate, and glycerol (Hydrophilic)
  • The tails are fatty acids (Hydrophobic).
  • In water, heads face the water on both sides and tails tuck inward, away from water.
500

Given the strand 5′-ACGGTCTTCCAG-3′, write the complementary strand. Explain the base-pairing rules and what “antiparallel” means.

  • A pairs with T (or U in RNA) and G pairs with C, held together by hydrogen bonds.
  • The complement is 3′-TGCCAGAAGGTC-5′.
  • Written 5′ to 3′, it is 5′-CTGGAAGACCGT-3′.
  • Antiparallel means the two strands run in opposite directions.
500

Asparagine and glutamine have an NH₂ group, yet they are not basic or positively charged. Explain why.

  • The C=O double bond sits next to the nitrogen.
  • It pulls on the NH₂ electrons, so they are tied up.
  • The NH₂ can’t pick up a proton, so it stays uncharged.
  • The amino acid is polar but not basic.
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