1. PROTEINS

2. Proteins Proteins do the nitty-gritty jobs of every living cell.
Proteins are made of long strings of individual building blocks known as amino acids.

3. Amino acids contain an amino group, a carboxyl group, a carbon and a unique R group

4. Identify amino acids ... from diagrams showing their structure.
3.2.2
Identify amino acids ... from diagrams showing their structure.

5. Polar R groups make the amino acid hydrophilic
Non-polar R groups make the amino acid hydrophobic

6. Ionic R groups make the amino acid hydrophilic

7. Explain the significance of polar and non-polar amino acids.
7.5.3
Explain the significance of polar and non-polar amino acids.

8. There are 20 commonly occurring amino acids that are found in proteins
leucine - leu - L
lysine - lys - K
methionine - met - M
phenylalanine - phe - F
proline - pro - P
serine - ser - S
threonine - thr - T
tryptophan - trp - W
tyrosine - tyr - Y
valine - val - V
alanine - ala - A
arginine - arg - R ***
asparagine - asn - N
aspartic acid - asp - D
cysteine - cys - C
glutamine - gln - Q
glutamic acid - glu - E
glycine - gly - G
histidine - his - H ***
isoleucine - ile - I
“Essential Amino Acids”
are those that must be ingested in the diet
(our body can’t make them)

9. Peptide Bonds join amino acids
It’s a condensation reaction
(meaning that H20 is released
when the bond is formed).
Two amino acids form a
DI-PEPTIDE
POLYPEPTIDES
are formed from more
than two amino acids
bonded together

10. FIGURE 3-20 Protein synthesis
In protein synthesis, a dehydration reaction joins the carbon of the carboxylic acid group of one amino acid to the nitrogen of the amino group of a second amino acid, releasing water. The resulting covalent bond between amino acids is called a peptide bond.

11. 3.2.5 Outline the role of condensation and hydrolysis in the relationships between … amino acids and polypeptides.
Draw and label a diagram showing the structure of a peptide bond between two amino acids.

12. Proteins have four levels of organization

13. Primary structure is the amino acid sequence

14. The amino acid sequence is coded for by DNA and is unique for each kind of protein

15. The amino acid sequence determines how the polypeptide will fold into its 3D shape

16. mis-formed hemoglobin causes sickle cell disease
Even a slight change in the amino acid sequence can cause the protein to malfunction
For example,
mis-formed hemoglobin causes sickle cell disease

18. Proteins have four levels of organization

19. Secondary structure results from hydrogen bonding between the oxygen of one amino acid and the hydrogen of another

20. FIGURE 3-22 The pleated sheet is an example of protein secondary structure
In a pleated sheet, a single polypeptide chain is folded back upon itself repeatedly (connecting portions not shown). Adjacent segments of the folded polypeptide are linked by hydrogen bonds (dotted lines), creating a sheetlike configuration. The R groups (green) project alternately above and below the sheet. Despite its accordion-pleated appearance, produced by bonding patterns between adjacent amino acids, each peptide chain is in a fully extended state and cannot easily be stretched farther. For this reason, pleated sheet proteins such as silk are not elastic.

21. The alpha helix is a coiled secondary structure due to a hydrogen bond every fourth amino acid

24. The beta pleated sheet is formed by hydrogen bonds between parallel parts of the protein

26. A single polypeptide may have portions with both types of secondary structure
Link to video

28. Proteins have four levels of organization

30. Tertiary structure depends on the interactions among the R group side chains

32. Types of interactions
Hydrophobic interactions: amino acids with nonpolar side chains cluster in the core of the protein, out of contact with water
= charged
= hydrophobic

34. Types of interactions
Hydrogen bonds between polar side chains

36. Types of interactions
Ionic bonds between positively and negatively charged side chains

38. Types of interactions
Disulfide bridge (strong covalent bonds) between sulfur atoms in the amino acid cysteine
Link to video

39. FIGURE 3-23 Keratin structure

41. Proteins have four levels of organization

42. Quaternary structure results from interactions among separate polypeptide chains.

43. For example, hemoglobin is composed of
4 polypeptide chains
Link to video

45. Proteins have four levels of organization

46. The folding of proteins is aided by other proteins, called chaperones
Act as temporary braces as proteins fold into their final conformation
Research into chaperones is a area of research in biology

47. FIGURE 3-21 The four levels of protein structure
Levels of protein structure are represented here by hemoglobin, the oxygen-carrying protein in red blood cells (red discs represent the iron-containing heme group that binds oxygen). Levels of protein structure are generally determined by the amino acid sequence of the protein, interactions among the R groups of the amino acids, and interactions between the R groups and their surroundings.

48. 7.5.1
Explain the four levels of protein structure, indicating the significance of each level.

49. Denaturation results in disruption of the secondary, tertiary, or quaternary structure of the protein

50. Denaturation may be due to changes in pH, temperature or various chemicals

51. Protein function is lost during denaturation, which is often irreversible

52. 3.6.4
Define denaturation.

53. Folded proteins are placed into two general categories

54. Fibrous proteins have polypeptide chains organized in long fibers or sheets
Water insoluble
Very tough physically, may be stretchy

55. Functions of fibrous proteins
Structural proteins function in support
Insects and spiders use silk fibers to make cocoons and webs
Collagen and elastin are used in animal tendons and ligaments
Keratin is the protein in hairs, horns and feathers

58. Functions of fibrous proteins
Contractile proteins function in movement
Actin and myosin contract to create the cleavage furrow and to move muscles
Contractile proteins move cilia and flagella

59. Globular proteins have their chains folded into compact, rounded shapes
Easily water soluble

60. Functions of globular proteins
Storage proteins function in the storage of amino acids
Ovalbumin is the protein in egg whites
Casein is the protein in milk, source of amino acids for baby mammals

62. Functions of globular proteins
Transport proteins function in the movement of other substances
Hemoglobin, the iron containing protein in blood, transport oxygen from lungs to other parts of the body (C3032H4816O872N780S9Fe4)
Membrane transport proteins such as channels for potassium and water

64. Functions of globular proteins
Hormone proteins function as cellular messenger molecules that help maintain homeostasis
Insulin: sends message “allow sugar into cells” (when blood glucose levels are high, cells will transport glucose into the cells for use or storage)
Glucagon: sends message “we need more sugar in the blood” (when blood glucose is too low, cells will release glucose)

66. Functions of globular proteins
Receptor proteins allow cells to respond to chemical stimuli
Growth factor receptors initiate the signal transduction pathway when a growth hormone attaches

67. Functions of globular proteins
Cholesterol receptors on the cell membrane allow LDL to be endocytosed into the cell

68. Functions of globular proteins
Protective proteins function as protection against disease
Antibodies combat bacteria and viruses

69. Functions of globular proteins
Enzymes speed up chemical reactions
Amylase and other digestive enzymes hydrolyze polymers in food
Catalase converts hydrogen peroxide H2O2 into water and oxygen gas during cellular respiration

70. Table 3-3 Functions of Proteins

71. Table 3-3 Functions of Proteins

72. Table 3-3 Functions of Proteins

73. Table 3-3 Functions of Proteins

74. Table 3-3 Functions of Proteins

75. Table 3-3 Functions of Proteins

76. 7.5.2
Outline the difference between fibrous and globular proteins, with reference to two examples of each protein type.
7.5.4
State four functions of proteins, giving a named example of each.