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Chapter 3
Proteins
PROTEINS
• A polymer made of the
monomers called amino
acids
• 20 types of amino acids
Purpose
• Mostly for structure:
skin, muscle,
fingernails, hair
Proteins
• -CONTAIN C, H, O, N (always)
Contain:
-COOH
-NH2 group (amino group)
-R group
What 3 groups make up an
amino acid?
What is the “R” group?
• Variable part
of the amino
acid
• Amino Acid
Chart
(handout)
Amino Acid Chart
Amino Acid Examples
How do they differ?
• alanine
• glycine
Peptide Bond
• Formation of a peptide bond
between two amino acids by
dehydration synthesis
Peptide Bonds: form
between amino acids
H
Protein Bonds
• peptide bond = the bond that holds
amino acids together in protein
molecules
• dipeptide = two connected
amino acids
• polypeptide = 3 or more
connected amino acids
• So polypeptide =
protein =
amino acid chain
Peptide Bonds: join amino acids
Forming/Breaking
Peptide Bonds
• youtube peptide bond formation
(polypeptide)
Peptide Bond is a covalent bond
• The four-atom functional group -C(=O)NHis called a peptide link.
• Between which two functional groups join? (youtube)
POLYPEPTIDE (many) Bonds
Between amino acids
Types of Proteins
SSSCDETR
• 1. structural- support (collagen,
keratin, elastin)-spider silk, hair,
skin, fingernails
• Spider Silk Protein Youtube
• CHEMISTRY OF HAIR: What level of
protein folding do you see here?
Type of Proteins
• 2. Contractilemovement=muscles, flagella
• Sliding Myofibril Youtube (2:59)
• Youtube flagella and cilia (3:12)
• Sperm flagella youtube (34 secs)
• Cilia Youtube (11 secs)
Types of Proteins
• 3. Storage proteins-such as
ovalbumin (in eggs), seeds, nuts
Type of Proteins
• 4. Defensive- antibodies
• Antibodies Youtube (2:40)
• Specific Immunity Youtube (1 min)
• Newly Developed Antibody Youtube (54
seconds)
Types of Proteins
• 5. Transport - include
hemoglobin that carries iron
(attract oxygen in red blood
cells)
• Hemoglobin oxygen Transport Youtube
(3:09)
• Hemoglobin Youtube (56 seconds)
Iron in red
Oxygen binds
to the iron
Types of Proteins
6. Signal - Hormone -
chemical messengers
(EX: insulin
thyroxin)
Insulin-Glucose Signaling
(4:10)
0
Type of Proteins
• 7. Enzymes-
speed up
chemical
reactions
• Lactase, Sucrase
-
• Enzyme Youtube (46 secs)
• The Role of Enzymes Youtube (3:35)
Type of Proteins
• 8. Receptor Proteins
• Intercellular communication
• Bind to specific proteins
(like hormones)
-Receptor Protein animation
-McGraw-Hill receptor channel
sodium channel youtube
-Secondary Receptor Protein (48 secs)
LEVELS OF FOLDING OF
PROTEINS
• The function of the protein is determined by its
amino acid sequence (R-groups) and its shape
DO PROTEIN FOLDNG ACTIVITY
• 1. Get an amino acid sheet (colors)
• 2. Add carboxyl (L hand) and amino
(R. hand) functional groups.
R group attaches to your leg.
NH2
H
H
C
C
COOH
R
group
NH2
COOH
R
group
• 4. Line up the amino acids in order
met
Lys
His
Gly
Val
Ser
Leu
Asp
Cys
Glu
Cys
Gln
Asn
Thr
Ser
Pro
Trp
Phe
Val
Tyr
Levels of Protein Structure
Primary structure
• is its unique sequence
of amino acids
• determined by
inherited genetic
info (DNA)
Protein Folding
Youtube
DO PROTEIN FOLDNG ACTIVITY
• 4. Join the amino group and carboxyl groups
to form a peptide bond.
N
COOH
NH2
C=O
I
H
R
group
R
group
Levels of Protein
Structure
• Secondary Structure
• most protein have
segments repeatedly
coiled or pleated in patterns
• result of H-bonds
• Secondary Structure Youtube
Note the H-bonds (between -O of carbonyl
and -H of amino):
coiling and pleating
Protein Structure
• Tertiary Structure
• a. folding on itself
• b. hydrophobic
• a type of weak bond
(disulfide, H-bonds, and ionic bonds)
• Cross-links between R-groups
Tertiary Folding:
disulfide bridges
• Disulfide
bridges formed
between
cysteine amino
acids
• (Look at
cysteine’s
structure)
• Four Levels of
Protein Folding
Tertiary Level:
Determined by R groups
Tertiary Structure Youtube
Disulfide Bridges
• Formed when cysteine’s sulfur join
• You Tube Videos Disulfide Bonds
Use the Amino Acid
Reference Sheet
• Select the type of tertiary interaction as
•
(1) disulfide
(2) ionic
•
(3) H bonds
(4) hydrophobic
•
•
•
•
A. Leucine and valine
B. Two cysteines
C. Aspartic acid and lysine
D. Serine and threonine
ANSWERS
• Select the type of tertiary interaction as
•
(1) disulfide
(2) ionic
•
(3) H bonds
(4) hydrophobic
•
•
•
•
A. 4
B. 1
C. 2
D. 3
Leucine and valine
Two cysteines
Aspartic acid and lysine
Serine and threonine
Protein Structure
• Quaternary Structure
• two or more subunits joined into
one functional macromolecule
•
Quarternary Structure youtube (42 secs)
Two Basic Shapes of
Quaternary Proteins
• Fibrous
• Strands
• Like hair,
nails,skin,muscle
fibers (meat)insoluble in water
• Globular
• Blobs like
hemoglobin,
insulin,
hormones,
antibodies
• Soluble in water
Quaternary: combination of
other shapes
• Protein Folding
Youtube (2:28)
collagen
• Cool Protein Folding
(34 secs)
• Identify the level of protein structure
• 1. Primary
2. Secondary
• 3. Tertiary
4. Quaternary
• A. Beta pleated sheet
• B. Order of amino acids in a protein
• C. A protein with two or more peptide
chains
• D. The shape of a globular protein
• E. Disulfide bonds between R groups
•
•
•
•
•
•
•
•
•
•
Identify the level of protein structure
1. Primary
2. Secondary
3. Tertiary 4. Quaternary
ANSWERS
2 Beta pleated sheet
1 Order of amino acids in a protein
4 A protein with two or more peptide
chains
3 The shape of a globular protein
3 Disulfide bonds between R groups
Denaturation
• Disruption of secondary, tertiary and
quaternary protein structure by:
• heat/organics (Break apart H bonds and
disrupt hydrophobic attractions)
• acids/ bases (Break H bonds between
polar R groups and ionic bonds)
• heavy metal ions (React with S-S bonds to
form solids)
• agitation (Stretches chains until
bonds break)
NOTE:
• Denaturation does not break
the primary structure (it just
unravels the tertiary structure)
• Denaturation of an egg with a
strong acid video
Protein Extra Credit OPP
• Can bring in up to 3 labels (no
repeats) for 1 point each with
one of each of these protein
terms circled:
– protein
– peptide
– amino
• 3. Draw out your R group
on your colored sheet.
• Group the R groups
according to:
•Nonpolar
•Polar
•Acidic
•Basic
FOLDING
• 5. Strongest interaction of side groups:
between cysteine molecules
(disulfide bond -S-S-)
(students move to accommodate this
bond formation)
Near the n-terminus
(NH2 or amino end)
6. Slightly weaker ionic interactions:
Between acidic and basic side groups
N
Terminus
C
terminus
• 7. Hydrophobic interactions (weaker)
Students clump their methyl group ends
together to “Get Away” from the
hydrophilic ends
8. AFTER WE HAVE BUILT OUR PROTEIN
WE WILL DENATURE IT. (Do not break the
peptide bonds.)