Amino acids

1. What are the monomers of proteins?

Amino acids.

2. What are the four groups attached to the central alpha carbon of an amino acid?

Hydrogen, amino group (NH₂), carboxyl group (COOH), R group.

3. What makes amino acids different from each other?

The R group (side chain).

4. How many amino acids are used by ribosomes?

20

5. Which organisms can synthesize all 20 amino acids?

plants

6. Why must animals obtain some amino acids from their diet?

They cannot synthesize all of them.

7. What are essential amino acids?

Amino acids the body cannot synthesize sufficiently.

8. What are non‑essential amino acids?

Amino acids the body can synthesize.

9. What reaction links amino acids together?

Condensation.

10. What bond forms between amino acids?

Peptide bond.

11. What does condensation release?

Water.

12. What reaction breaks peptide bonds?

Hydrolysis.

13. Does the R group participate in peptide bond formation?

No — allowing huge diversity.

The R group does not participate in peptide bond formation, allowing for significant diversity among amino acids.

14. How many amino acids does beta‑endorphin have?

31

15. How many amino acids does insulin have?

51

16. What is the function of alpha‑amylase?

Starch digestion.

17. What is the largest known polypeptide?

Titin (~34,400 amino acids).

18. What is denaturation?

Loss of protein structure due to bond disruption.

19. What causes denaturation?

High temperature, extreme pH.

20. Why does denaturation affect protein function?

Shape determines function.

21. What are the two broad categories of amino acids?

Hydrophobic and hydrophilic.

22. What subtypes exist within hydrophilic amino acids?

Basic, acidic, charged, uncharged.

23. How does amino acid diversity affect proteins?

Determines folding and function.

24. What is primary structure?

Linear sequence of amino acids.

25. What determines all higher levels of structure?

Primary structure.

26. What is secondary structure?

Local folding into alpha helices or beta sheets.

27. What bonds stabilize secondary structure?

Hydrogen bonds between backbone C=O and N–H.

28. What is tertiary structure?

Overall 3D shape of a polypeptide.

29. What interactions stabilize tertiary structure?

Ionic bonds, hydrogen bonds, disulfide bridges, hydrophobic interactions.

30. What is quaternary structure?

Assembly of multiple polypeptide chains.

31. What stabilizes alpha helices?

Hydrogen bonds between adjacent turns.

32. What stabilizes beta sheets?

Hydrogen bonds between parallel strands.

33. What are ionic bonds in proteins?

Attractions between oppositely charged R groups.

34. Why are ionic bonds pH‑dependent?

Protonation states change with pH.

35. What are disulfide bonds?

Strong covalent bonds between cysteine residues.

36. What drives hydrophobic interactions?

Non‑polar R groups cluster away from water.

37. What shape do most globular proteins form?

Compact, ball‑like structure.

38. Where do hydrophobic amino acids cluster in cytoplasmic proteins?

Inside the protein.

39. Where do hydrophobic amino acids cluster in membrane proteins?

On the outside, facing the membrane.

40. What is collagen’s quaternary structure?

Three polypeptides twisted together.

41. What is hemoglobin’s quaternary structure?

Four polypeptides + heme groups (conjugated protein).

42. What is a conjugated protein?

Protein with a non‑polypeptide prosthetic group.

43. What are fibrous proteins?

Elongated, structural proteins (e.g., collagen).

44. Are fibrous proteins soluble?

No — insoluble.

45. What are globular proteins?

Rounded, functional proteins (e.g., enzymes).

46. Are globular proteins soluble?

Yes — soluble in cytoplasm.