BIOSC 0150 Week 3: Nucleic Acids, Lipids, and Carbs

the sequence of amino acids

primary structure

α‑helices and β‑sheets formed by hydrogen bonds

secondary structure

the 3D folding of one polypeptide (R‑group interactions)

terietiary structure

multiple polypeptide chains coming together

quaternary structure

Primary: peptide bonds

Secondary: hydrogen bonds

Tertiary:

hydrogen bonds

Ionic bonds

Hydrophobic interactions

Vand der Waals

What are the bonds/ interactions that stabilize each level of protein structure?

What happens when you change the environment (increase temperature, add acid, add urea, etc) of a folded protein? Be as specific as possible; remember to account for every level of protein structure.

• A → T

• T → A

• C → G

• G → C

Predict the sequence of bases in a complementary DNA strand if given the sequence of one strand of DNA

• A

• T

• C

• G

• DNA:

  • Has deoxyribose sugar

  • Has T (thymine)

  • Usually double‑stranded

• RNA:

  • Has ribose sugar

  • Has U (uracil)

  • Usually single‑stranded

Recognize and analyze structures of a nucleic acid (monomer or polymer)the

• Is it DNA or RNA?

• What bases do you see?

What kinds of [bonds/ interactions/ functional groups] do you see?

a. Phosphodiester bonds (covalent bond between sugar–phosphate backbone)

b. Hydrogen bonds (A–T = 2 H‑bonds, A–U = 2 H‑bonds, C–G = 3 H‑bonds)

what bonds/ interactions/ forces stabilize (a) adjacent nucleotides in a polymer? (b) base pairing

You join nucleotides by forming a phosphodiester bond between:

• the 3’ OH of one nucleotide

• the 5’ phosphate of the next nucleotide

This is a condensation reaction (water is released).

how do you build a polymer of nucleic acid? (Sketch the condensation reaction that leads to phosphodiester bond formation—pay attention to directionality (5’ vs 3’ end))

Carbohydrate monomers: glucose, fructose, galactose
Disaccharides: sucrose, lactose, maltose
Polysaccharides: starch, glycogen, cellulose

Monomer = single ring
Disaccharide = two rings
Polymer = long chain of rings

recognize the structure and names of the monomers/ polymers of carbohydrates that we discussed.

covalent bond

what’s the name of the bond that occurs between monomers?

Carbs have many OH groups → many bonding options → branching
Amino acids have only 2 ends → one linear chain → no branching

how come polymers of carbs be branched but peptides can’t?

Strongest = covalent

which of these bonds/ interactions is strongest?

Lipids aren’t polymers because they have no repeating monomers. They’re defined by being hydrophobic + nonpolar, not by structure.

explain why lipids aren’t polymers—what are they defined by, if not structure?

Glycerol + 3 fatty acids → ester bonds + 3 H₂O → triglyceride

diagram the condensation reaction that occurs to produce a triglyceride.

Fatty acid + glycerol → ester bond + H₂O

what is the name of resulting bond between fatty acid and glycerol?

Backbone: glycerol OH + fatty acid COOH → ester bond (C–O–C)
R‑groups: fatty acid hydrocarbon tails (C–H), not involved in bonding

what atoms are involved (backbone vs R groups)