Proteins
Regents Biology
Proteins:
Multipurpose molecules
Regents Biology
2006-2007
Proteins
 Building block = amino acids
amino amino amino amino amino
acid – acid – acid – acid – acid

20 different amino acids used in the body
H O
H
| ||
—N—
—C—C—OH
|
H variable
Regents Biology
group
There’s
20 of us…
like 20 different
letters in an
alphabet!
Can make lots of
different
words
Proteins
 Function:

many, many functions
 hormones
 signals from one body system to another
 insulin
 movement
 muscle
 immune system
 protect against germs
 enzymes
Regents Biology  catalysts in chemical reactions
Proteins
Examples

Muscle
insulin
 Repair and rebuild cells

Skin, hair, fingernails, claws
pepsin
 collagen, keratin

Pepsin
 digestive enzyme
in stomach

Insulin
 hormone that controls blood
sugar levels
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collagen (skin)
Amino acid chains
 Proteins

amino acids chained into a polymer called a
polypeptide
amino acid
amino acid
amino acid
amino acid
amino acid
 Each amino acid is different

some “like” water & dissolve in it

some “hate” water & separate from it
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Water-hating amino acids
 Hydrophobic
“water hating” amino acids
 try to get away from water in cell

 the protein folds
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Water-loving amino acids
 Hydrophillic
“water loving” amino acids
 try to stay in water in cell

 the protein folds
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Sickle cell anemia
I’m
hydrophilic!
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Just 1
out of 146
amino acids!
But I’m
hydrophobic!
Protein Formation:
1. Amino acids link up to form long
chains called polypeptides
2. Polypeptide chains twist or spiral
3. The spiraled chain then folds into
subunits
4. The protein forms its final shape by
linking together multiple subunits
Regents Biology
A. Primary Structure (1°)
 Amino acids bonded together by
peptide bonds.
Amino Acids (aa)
aa1
aa2
aa3
Peptide Bonds
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aa4
aa5
aa6
B. Secondary Structure (2°)
 3-dimensional folding arrangement of a
primary structure into coils and pleats held
together by hydrogen bonds.
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B. Secondary Structure (2°)
Two examples:
Alpha Helix
Beta Pleated Sheet
Hydrogen Bonds
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Alpha Helix
Beta Pleated
Sheets
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C. Tertiary Structure (3°)
 Secondary structures bend and fold into a
more complex 3-D arrangement.
 Called a “subunit”.
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C. Tertiary Structure (3°)
Alpha Helix
Beta Pleated Sheet
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D. Quaternary Structure (4°)
 Composed of 2 or more “subunits”.
 Example: enzymes (hemoglobin)
3° subunits
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Subunits
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For proteins: SHAPE matters!
 Proteins fold & twist into 3-D shape

that’s what happens in the cell!
 Different shapes = different jobs
growth
hormone
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hemoglobin
pepsin
collagen
It’s SHAPE that matters!
 Proteins do their jobs, because
of their shape
 Unfolding a protein destroys its shape
wrong shape = can’t do its job
 unfolding of proteins = “denature”

 temperature
unfolded
“denatured”
 pH (acidity)
 salinity
With protein,
it’s not the size,
but the SHAPE
that matters!
Regents Biology
folded
Quick review: With a partner
1. What is denaturing? What causes it?
2. What is the role of hydrophobic and
hydrophilic amino acids in protein
formation?
3. List at least 4 protein functions.
Regents Biology