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Human Biochemistry
Amino Acids and Proteins
• there are about 20 amino acids that occur naturally
• they are the basic “building blocks” of life/proteins
• condensation reactions will link amino acids together to form polypeptides and eventually proteins
• water is formed and they link together with a peptide bond
• peptide bonds YouTube (1:14)
Primary Structure • determined by the number, kind, and
order of a.a. in the polypeptide • held together by simple peptide bonds
Proteins have a complex structure which can be explained by defining four levels of structure
What is a protein video 3:38
Secondary Structure • the polypeptide then spontaneously folds into
regular, repeating structure because of hydrogen bonding
Tertiary Structure
• highly specific looping and folding of the polypeptide because of the following interactions between their R-groups:– covalent bonding– hydrogen bonding– ionic bonding– London dispersion forces
• this tertiary level is the final level of organization for proteins containing only a single polypeptide chain
Quaternary Structure
• linkage of two or more polypeptides to form a single protein in precise ratios and with a precise 3-D configuration.
• Protein folding
Quaternary Structure example
Carbohydrates• most abundant class of biological molecules• range from simple sugars (glucose) to
complex carbohydrates (starch)
Monosaccharides• simplest sugars (single sugars)• two common isomers of monosaccharides
(C6H12O6)• glucose• fructose
Disaccharides• two monosacharides bonded together by a
condensation reaction that creates a glycosidic linkage
• three common disaccharides1. sucrose - common table sugar 2. lactose - major sugar in milk3. maltose -
Polysaccharides• condensation of many glucose molecules
• serve principally as food storage and structural molecules in plants
• three types of polysaccharides 1. Starches (plants)– serve as storage depots of glucose
2. Cellulose (plants)– plant cell walls
3. Glycogen– serve as a form of energy storage in animals and
fungi
3 Main Types of Lipids
1. Triglycerides (fats and oils)• found in fatty tissue• a condensation reaction called ester linkage
Saturated vs. Unsaturated fatty acids (2:51)
2. Phospholipids• major structural components of cell
membranes• polar “heads” love water (hydrophilic)• uncharged “tails” avoid water (hydrophobic)
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3. Steroids• cholesterol is the most abundant and important steroid