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Chapter 20 and GHW#10
Questions
Proteins
Proteins
Naturally occurring bioorganic polyamide polymers
containing a sequence of various combinations of 20
amino acids.
Amino acids contain the elements carbon, hydrogen,
oxygen, and nitrogen and few also contain sulfur
Amino acids: Polyfunctional bioorganic compunds
Zwitterion form
R = 20 different alkyl, alcohols, amines , acids and heterocyclic amines
Handedness/Chirality of Amino Acids
Groups of Amino Acids baed on R group
• Hydrophobic (non-polar, neutral)
• Polar, neutral
• Polar Acidic
• Polar Basic
1) Hydrophobic (non-polar, neutral) (5 amino acids)
1) Hydrophobic (non-polar, neutral) continued..
( 4 amino acids)
2) Hydrophilic (polar, neutral) continued..( 6 amino acids).
3) & 4) Polar amino acids (5 amino acids)
Abbreviations
glycine
alanine
valine
leucine
isoleucine
methionine
phenylalanine
tryptophan
Proline
Gly
Ala
Val
Leu
Ile
Met
Phe
Trp
Pro
G
A
V
L
I
M
F
W
P
1) Give name, abbreviation and types (neutral, polar, nonpolar, basic and acidic).
1) Give name, abbreviation and types (neutral, polar, nonpolar, basic and acidic).
Protein Function
• Enzymes - catalyze biological reactions (alcohol
dehydrogenase, glucokinase)
• Hormones - signals between cells (insulin, growth
hormone)
• Storage Proteins- store nutrients (ferritin storing iron in the
liver)
• Transport Proteins - transport nutrients through the body
(hemoglobin transport of oxygen)
• Structural Proteins- form structure of cells ( keratin, elastin,
collagen)
• Protective Proteins- have specific protective function
(antibodies bind to foreign proteins)
2) Draw the optical and L isomers for: cys.
3) Use the following amino acids to answer the
questions below:
Which amino acid is most polar?
b. Which amino acid is most non-polar?
c. Which amino acid gives an acidic solution?
d. Which amino acid gives a basic solution?
Primary protein structure
Proteins are polymers made up of amino acids.
Peptide bond - how the amino acids are
linked together to make
a protein.
H
|
H2NCCOOH +
|
R
H
|
H2NCCOOH
|
R’
H O
H
| ||
|
H2N - C - C - N - C - COOH
|
| |
+ H2O
R
H R’
4) Draw the following:
a) Dipeptide bond between ala and asp, and identify Cand N-terminal.
b) Tripeptide, ile-cys-thr, and identify N- ( left) and Cterminal(right).
4) Continued….
c) How many possible isomers are in the tripeptide formed with ile,
cys and thr? Come up with a formula for linear chain with “ n” amino
acids.
d) Give the IUPAC name of the tripeptide with the sequence, ile-cysthr
.
5) Use the structure to answer the questions below:
Use the structure to answer the questions below
a) Which letter arrow points the end of the peptide that is the "amine“
end-N-terminal?
b) Which letter arrow points the end of the peptide that is the
"carboxyl" end, C-terminal?
c) Which letter arrow points to an amide or peptide bond?
Four levels of protein structure
1) Primary structure
The sequence of amino acids in a protein.
2) Secondary structure
Way that chains of amino acids are coiled or
folded - (-helix, -sheet, random coil).
3) Tertiary structure
Way -helix, -sheet, random coils fold and coil.
4) Quaternary structure
Way that two or more peptide chains pack
together.
Three levels of structure: telephone cord
Summary of protein structure
primary
H O
H O
| ||
| ||
H2N - C - C - NH - C - C |
|
R
R’
tertiary
secondary
H
|
N - C - COOH
| |
H R’’
quaternary
6) Explain the differences between primary, secondary,
tertiary, and quaternary protein structures by giving brief
definitions of each. What types of bonding are used in
each?
Primary
Secondary
Tertiary
Quaternary
7) Use the above structures to answer the questions below:
•
a. Which two amino acids may link in a salt bridge in tertiary protein structure?
•
b. Which two amino acids may link in hydrophobic interactions in tertiary protein
structure?
•
c. Which two amino acids may link in hydrogen bonding interactions in tertiary protein
structure?
Alpha Helix
Alpha Helix
Beta Pleated Sheets
Beta Pleated Sheets
8) Explain the difference between the alpha helix and the
beta pleated sheet protein structures. What are the
differences in the hydrogen bonding?
Fibrous Proteins
a) - Keratin b) Collagen etc..