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Protein
Macromolecules: Proteins
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Proteins taken in as food (meat, dairy, eggs, beans,
nuts) are different than our proteins.
They must be broken down into amino acids by adding
water. Recall Carbohydrates and Lipids
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The process is…
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Hydrolysis.
To build proteins water must be removed in the
process of….
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Dehydration Synthesis.
Proteins: CHON(S)
Proteins are large complex polypeptides.
 Needed for structure: muscles, skin,
cell membranes, and enzymes
 Made of amino acids
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Amino acids are joined by peptide bonds
A string of peptides is also called a
polypeptide
Proteins: Structure
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Amino acids have three parts:
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The 20+ amino acids differ only in their Rgroup
Generalized Formula for Amino Acid
H
R
C
Acid group
COOH
NH2
Rest of the molecule
Amino group
Amino Acid Groups
H
NH2
=
N
H
O
COOH =
C O H
Macromolecules: Proteins
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Peptide bonds join amino acids when dehydration
synthesis occurs.
An OH from the acid group of one amino acid
joins to an H from the amino group of the other
amino acid.
A water molecule is formed, and a C-N bond is
formed between the two amino acids.
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The C-N bond is called a peptide bind.
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Dipeptide: 2 amino acids joined
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Polypeptide: 3 or more amino acids joined.
Dehydration Synthesis
Prentice Hall, Biology
Proteins: Structure
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The protein you end up with depends
on:
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which amino acids were chosen,
their order (sequence), and
how many of each
Who decides?
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The DNA
Proteins: Structure
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Compare 3 amino acids:
Proteins: Enzymes
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Enzymes are proteins that act as a catalyst.
(Catalysts are substances that increase the
rate of a chemical reaction.)
Enzymes are not used up or changed by a
reaction.
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Enzymes are specific in their actions.
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Enzymes work best under specific conditions.
Category 1
Category 2
Let’s Review
What is the name of
this unit?
Category 3
Category 4