1. Amino Acids Proteins, and Enzymes
Types of Proteins
Amino Acids
The Peptide Bond
Amino Acids Proteins, and Enzymes

2. Types of Proteins Type Examples
Structural tendons, cartilage, hair, nails
Contractile muscles
Transport hemoglobin
Storage milk
Hormonal insulin, growth hormone
Enzyme catalyzes reactions in cells
Protection immune response

3. Amino Acids Building blocks of proteins Carboxylic acid group
Amino group
Side group R gives unique characteristics
R side chain I
H2H—C —COOH H

4. Examples of Amino AcidsH I
H2N—C —COOH
H glycine
CH3
H alanine

5. Types of Amino Acids Nonpolar R = H, CH3, alkyl groups, aromatic O
Polar ll
R = –CH2OH, –CH2SH, –CH2C–NH2,
(polar groups with –O-, -SH, - N-)
Polar/Acidic
R = –CH2COOH, or -COOH
Polar/ Basic
R = –CH2CH2NH2

6. Learning Check AA1 A. NH2–CH2–COOH (Glycine) CH3 | CH–OH
Identify each as (1) polar or (2) nonpolar
A. NH2–CH2–COOH (Glycine)
CH3 |
CH–OH
B. NH2–CH–COOH (Serine)

7. Solution AA1 A.(2) NH2–CH2–COOH (Glycine) CH3 | CH–OH
Identify each as (1) polar or (2) nonpolar
A.(2) NH2–CH2–COOH (Glycine)
CH3 |
CH–OH
B. (1) NH2–CH–COOH (Serine)

8. Essential Amino Acids 10 amino acids not synthesized by the body
arg, his, ile, leu, lys, met, phe, thr, trp, val
Must obtain from the diet
All in dairy products
1 or more missing in grains
and vegetables

9. Amino Acids as Acids and Bases
Ionization of the –NH2 and the –COOH group
Zwitterion has both a + and – charge
Zwitterion is neutral overall +
NH2–CH2–COOH H3N–CH2–COO–
glycine Zwitterion of glycine

10. pH and ionization H+ OH– + + Positive ion zwitterion Negative ion
H3N–CH2–COOH H3N–CH2–COO– H2N–CH2–COO–
Positive ion zwitterion Negative ion
Low pH neutral pH High pH

11. The Peptide Bond
Amide bond formed by the –COOH of an amino acid and the –NH2 of the next amino acid
O CH3
| | |
NH3–CH2–COH H3N–CH–COO–
O CH3
| | |
NH3–CH2–C – N–CH–COO–
| peptide bond H

12. Peptides Amino acids linked by amide (peptide) bonds
Gly Lys Phe Arg Ser
H2N-end COOH-end
Peptide bonds

13. Learning Check AA3
What are the possible tripeptides formed from one each of leucine, glycine, and alanine?

14. Solution AA3
Tripeptides possible from one each of leucine, glycine, and alanine
Leu-Gly-Ala
Leu-Ala-Gly
Ala-Leu-Gly
Ala-Gly-Leu
Gly-Ala-Leu
Gly-Leu-Ala

15. Amino Acids, Proteins, and Enzymes
Primary and Secondary Structure
Tertiary and Quaternary Structure
Protein Hydrolysis and Denaturation

16. Primary Structure of Proteins
The particular sequence of amino acids that is the backbone of a peptide chain or protein
Ala-Leu-Cys-Met

17. Secondary Structure – Alpha Helix
Three-dimensional arrangement of amino acids with the polypeptide chain in a corkscrew shape
Held by H bonds between the H of –N- H group and the –O of C=O of the fourth amino acid along the chain
Looks like a coiled “telephone cord”

18. Secondary Structure – Beta Pleated Sheet
Polypeptide chains are arranged side by side
Hydrogen bonds form between chains
R groups of extend above and below the sheet
Typical of fibrous proteins such as silk

19. Secondary Structure – Triple Helix
Three polypeptide chains woven together
Glycine, proline, hydroxy proline and hydroxylysine
H bonding between –OH groups gives a strong structure
Typical of collagen, connective tissue, skin, tendons, and cartilage

20. Learning Check P1 Indicate the type of structure as
primary (2) alpha helix
beta pleated sheet (4) triple helix
Polypeptide chain held side by side by H bonds
Sequence of amino acids in a polypeptide chain
Corkscrew shape with H bonds between amino acids
Three peptide chains woven like a rope

21. Solution P1 Indicate the type of structure as primary (2) alpha helix
beta pleated sheet (4) triple helix
3 Polypeptide chain held side by side by H bonds
1 Sequence of amino acids in a polypeptide chain
2 Corkscrew shape with H bonds between amino acids
4 Three peptide chains woven like a rope

22. Tertiary Structure Specific overall shape of a protein
Cross links between R groups of amino acids in chain
disulfide –S–S–
ionic –COO– H3N–
H bonds C=O HO–
hydrophobic –CH3 H3C–

23. Globular and Fibrous Proteins
Globular proteins Fibrous proteins
“spherical” shape long, thin fibers
Insulin Hair
Hemoglobin Wool
Enzymes Skin
Antibodies Nails

24. Quaternary Structure Proteins with two or more chains
Example is hemoglobin
Carries oxygen in blood
Four polypeptide chains
Each chain has a haem group to
bind oxygen

25. Learning Check P3 Identify the level of protein structure
1. Primary 2. Secondary
Tertiary 4. Quaternary
Beta pleated sheet
Order of amino acids in a protein
A protein with two or more peptide chains
The shape of a globular protein
Disulfide bonds between R groups

26. Solution P3 Identify the level of protein structure
1. Primary 2. Secondary
3. Tertiary 4. Quaternary
2 Beta pleated sheet
1 Order of amino acids in a protein
4 A protein with two or more peptide
chains
D. 3 The shape of a globular protein
E Disulfide bonds between R groups

27. Protein Hydrolysis Break down of peptide bonds
Requires acid or base and heat
Gives smaller peptides and amino acids
Similar to digestion of proteins using enzymes
Occurs in cells to provide amino acids to synthesize other proteins and tissues

28. Hydrolysis of a Dipeptide

29. Denaturation
Disruption of secondary, tertiary and quaternary protein structure by
heat/organics
Break apart H bonds and disrupt hydrophobic attractions
acids/ bases
Break H bonds between polar R groups and
ionic bonds
heavy metal ions
React with S-S bonds to form solids
agitation
Stretches chains until bonds break

30. Applications of Denaturation
Hard boiling an egg
Wiping the skin with alcohol swab for injection
Cooking food to destroy E. coli.
Heat used to cauterize blood vessels
Autoclave sterilizes instruments
Milk is heated to make yoghurt

31. Learning Check P4
What are the products of the complete hydrolysis of Ala-Ser-Val?

32. Solution P4 The products of the complete hydrolysis of Ala-Ser-Val are
alanine
serine
valine

33. Learning Check P5
Tannic acid is used to form a scab on a burn. An egg becomes hard boiled when placed in hot water. What is similar about these two events?

34. Solution P5
Acid and heat cause a denaturation of protein. They both break bonds in the secondary and tertiary structure of protein.

35. DNA

36. DNA RNA

37. DNA RNA

38. DNA RNA

39. DNA Backbone Structure
Alternate phosphate and sugar (deoxyribose), phosphate ester bonds

40. DNA Backbone Structure
Alternate phosphate and sugar (deoxyribose), phosphate ester bonds

41. DNA RNA

42. DNA Primary Structure Summary

43. DNA RNA

44. Base pairing by unique hydrogen bonds
DNA Double Helix
Base pairing by unique hydrogen bonds
C - G and A - T pairs

45. Base pairing by unique hydrogen bonds
DNA Double Helix
Base pairing by unique hydrogen bonds
C - G and A - T pairs

46. DNA

47. Complementary base pairs form new strands.
DNA Replication
Complementary base pairs form new strands.

48. Types of RNA
mRNA contains codons which code for amino acids.

49. DNA

50. rRNA - Ribosome - contains enzymes and keeps everything together
Types of RNA
rRNA - Ribosome - contains enzymes and keeps everything together

51. Types of RNA
tRNA - Transfer RNA carries amino acid and read codons on m-RNA through its own anticodons.

52. Types of RNA
tRNA - Transfer RNA carries amino acid and read codons on m-RNA through its own anticodons.