Chapter 14.1-14.4
Proteins
Heather Bobber, Zoë Berkheimer, and Tyler Sterling
14.1: Functions of Proteins
 Most important biological compound
 Greek “proteios” – “of first importance”
 Functions
 Structure
 Skin, bones, hair, and nails
 Ex. Collagen and Keratin
 Catalysis
 Enzymes that speed up reactions in living organisms
 Movement
 Muscles are made of myosin and actin
Functions (continued)
 Transport
 Transport nutrients in cells
 Ex. Hemoglobin carries oxygen in blood from the lungs to the cells
 Hormones
 Some proteins are hormones
 Ex. Insulin, erythropoietin, and human growth hormones
 Protection
 Antibodies and fibrinogen which is involved in blood clotting
 Storage
 Proteins store materials
 Ex. Ferritin stores iron in the liver
Functions (continued)
 Regulation
 Controls the expression of genes and manufacturing of proteins
in cells
 One cell has 9000 different proteins while the human body
has 100,000.
 There are 2 types of proteins
 Fibrous proteins: insoluble in water and are used for structural
purposes.
 Globular proteins: soluble in water and are used for
nonstructural purposes.
14.2: Amino Acids
 Proteins are chains of
amino acids
 Amino Acid- An organic
compound containing an
amino group and a
carboxyl group
 In nature there are 20
common amino acids called
alpha amino acids
Amino Acids (continued)
 There are 4 groups of chains based on their polarity
 Non-polar, polar but neutral, acidic, and basic
 Non-polar is hydrophobic
 The other three are hydrophilic
 Most amino acids are L-isomers and D-amino acids are rare
in nature.
14.3: Zwitterions
 Zwitterions: compounds with a positive charge on one atom
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and a negative charge on another atom
Zwitter – German “hybrid”
Amino acids are zwitterions
Ionic compounds
Solids, high melting points
Fairly soluble in water
Zwitterions Continued
 Amino acids are negative ions at high pH and positive at low
pH
 Isoelectric point – pH at which the sample of amino acid or
protein has an equal number of positive and negative charges
14.4: Characteristics of Amino Acids
 The side chain gives unique properties to amino acids
 Example: Cysteine can be easily dimerized to cystine
 Some amino acids have acidic or basic properties
 Glutamic acid and Aspartic acid have carboxylic acid groups on side chain
 Histidine, lysine, and arginine have basic side chains
 Phenylalanine, tryptophan, and tyrosine have aromatic rings in
their side chains, making them key precursors to
neurotransmitter
 Tryptophan is converted to serotonin
 Tyrosine is converted to adrenaline