Biochemistry of Cells

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Secondary protein structures occur when protein chains coil or fold

When protein chains called polypeptides join together, the tertiary structure forms because R groups interact with each other

In the watery environment of a cell, proteins become globular in their quaternary structure

Slide 60

Protein Structures or CONFORMATIONS

Hydrogen bond

Pleated sheet

Amino acid

(a) Primary structure

Hydrogen bond

Alpha helix

(b) Secondary structure

Polypeptide

(single subunit)

(c) Tertiary structure

(d) Quaternary structure

Slide 61

Denaturating Proteins

Changes in temperature & pH can denature (unfold) a protein so it no longer works

Cooking denatures protein in eggs

Milk protein separates into curds & whey when it denatures

Slide 62

Changing Amino Acid Sequence

Substitution of one amino acid for another in hemoglobin causes sickle-cell disease

(a) Normal red blood cell

Normal hemoglobin

1

2

3

4

5

6

7. . . 146

(b) Sickled red blood cell

Sickle-cell hemoglobin

2

3

1

4

5

6

7. . . 146

Slide 63

Other Important Proteins

Blood sugar level is controlled by a protein called insulin

Insulin causes the liver to uptake and store excess sugar as Glycogen

The cell membrane also contains proteins

Receptor proteins help cells recognize other cells

Slide 64

INSULIN

Cell membrane with proteins & phospholipids

Slide 65

Nucleic Acids

Store hereditary information

Contain information for making all the body’s proteins

Two types exist --- DNA & RNA

Slide 66

Slide 67

Nucleic Acids

Nitrogenous base

(A,G,C, or T)

Phosphate

group

Thymine (T)

Sugar

(deoxyribose)

Phosphate

Base

Sugar

Nucleic acids are polymers of nucleotides

Nucleotide

Slide 68

Nucleotide – Nucleic acid monomer

Slide 69

Nucleic Acids

Slide 70

Bases