1.what makes an enzyme specific to one type of reaction (in other words, what determines the...
TRANSCRIPT
1. What makes an enzyme specific to one type of reaction (in other words, what determines the function of a protein)?
– SHAPE determines the function of a protein and makes enzymes specific to one reaction
2. How does heating (boiling) affect the ability of an enzyme to perform its function?
– Heating/boiling denatures enzymes (unfolds them) and makes them lose their function
What will we learn today?
HOW is the shape of a protein determined?WHY does heating/boiling denature
enzymes and make them lose their function?
Also:• What makes hair straight or curly and how do
perms work?• Why is it important to eat different types of food
to supply our protein needs?
Proteins are made ofchains of amino acids
What are amino acids?
Link to amino acid 3-D models
H2NAminogroup C
Side chain
R
H
C
O
OH
Carboxylgroup
Non-ionized form
There are 20 different amino acids. All have the same general form.
CCO
O–
H
H3N+
H
Glycine (G)Gly
C CO
O–
H
H3N+
CH3
Alanine (A)Ala
C CO
O–
H
H3N+
CHH3C CH3
Valine (V)Val
C CO
O–
H
H3N+
CH2
H3C CH3
Leucine (L)Leu
CH
CCO
O–
H
H3N+
CH
Isoleucine (I)Ile
CH3
CH2
H3C
These side chains contain only carbon and/or hydrogen
CO
O–C
CH2
CH2
H2C
H2N+
H
Proline (P)Pro
Each amino acid has a different side chain.
CH3N+
CH2
H
C
O
O–
Phenylalanine (F)Phe
CH3N+
CH2
H
C
O
O–
Tyrosine (Y)Tyr
OH
CH3N+
CH2
H
C
O
O–
NH
Tryptophan (W)Trp
Side chains contain ring structures
Each amino acid has a different side chain.
CH3
CH2
CH2
S
C CH3N+
HO
O–
Methionine (M)Met
SH
CH2
C CH3N+
HO
O–
Cysteine (C)Cys
Side chains contain sulfur
Each amino acid has a different side chain.
OH
CH2
C CH3N+
HO
O–
Serine (S)Ser
Threonine (T)Thr
CH
C CH3N+
HO
O–
CH3HO
Side chains contain hydroxyl [OH] functional groups
Each amino acid has a different side chain.
C
CH2
C CH3N+
HO
O–
H2N O
Asparagine (N)Asn
CH2
C CH3N+
HO
O–
CH2
C
OH2N
Glutamine (Q)Gln
Side chains contain amino [NH2] functional groups
Each amino acid has a different side chain.
CH2
C CH3N+
HO
O–
NH
+NH
Histidine (H)His
CH2
C CH3N+
HO
O–
CH2
CH2
+NH3
CH2
Lysine (K)Lys
Basic side chains
CH2
C CH3N+
HO
O–
CH2
CH2
NH
C +NH2
NH2
Arginine (R)Arg
Each amino acid has a different side chain.
CH2
C CH3N+
HO
O–
C
O– O
Aspartate (D)Asp
Acidic side chains
CH2
C CH3N+
HO
O–
CH2
C
O– O
Glutamate (E)Glu
Each amino acid has a different side chain.
H
H H H H H HO O O H H O H H O
N C C N NC C C C
H CH3 CH2
OH
N-terminus
N C C
CH2
C
O
OH
CH2
N C C
CH
CH3H3C
CH2
OH
H H O
N C C
H H O
N C C
H H O
N C C
CH2
SH
OH
C-terminus
H2N
H
H
C CO
OHCarboxylgroup
H2N
H
CH3
C CO
OHAminogroup
H2N
H
H
C
O
C N CC
HH
CH3
OH
O
Peptidebond
+ H2O
H2N Gly Ala Ser Asp
N-terminus
21 3 54 6 7 8
Phe Val Tyr Cys
C-terminus
COOH
+
Proteins are chains of amino acids
Amino Acid sequence determines the 3-D protein shape
• Interactions between amino acids cause folding and bending of the chain
Examples: – positive (+) and negative (-) parts of amino
acids are attracted to each other.– hydrophobic regions are attracted to each other
• Foldinghttp://www.stolaf.edu/people/giannini/flashanimat/proteins/hydrophobic%20force.swf• Structure levelshttp://www.stolaf.edu/people/giannini/flashanimat/proteins/protein structure.swf
CH2 OH CH2C
O
N
H
HHydrogen bond between
two side chains
CH2 OH O C
OC H N
CH2CH
CH3
CH3
Hydrogen bond betweenside chain and peptide group
Hydrogen bond between peptide
groupsH3C
H3C
CHCH2
Hydrophobicinteraction
CH2 CH2S S
Disulfide bond
Ionic bond
(CH2)4 NH3+ –O
O
CCCH2
Figure 3.11a
Interactions that determine the structure of proteins
A tertiary structurecomposed mostly of
-helices
A tertiary structurecomposed mostly of-pleated sheets
A tertiary structurerich in disulfide bonds
Figure 3.11b
Tertiary structures are diverse.
Paper polypeptides activity
Peptides are chains of amino acids and sometimes used as another word for protein.
Follow the instructions of your teacher to build peptides using the paper amino acid models.
Straight, curly, and “permed” hair
Explain the connection between the order of the amino acids and the shape of the protein.
Why did the boiled lactase not work any more? (base your answer on the paper model)
ESSENTIAL AMINO ACIDS
Essential amino acids and nutrition
• Consider why protein is needed and what amino acids and proteins are used for in the body. Describe the symptoms you would expect a person with protein deficiency to have.
• Look at Table 1. Which amino acids does corn lack (not have)? Which amino acids do beans and legumes lack (not have)?
• Vegans are vegetarians that do not eat any food from animals, including milk and eggs. Why must vegans combine foods from a variety of plant sources to avoid protein deficiency (for example rice and beans instead of only beans)?
• A new protein supplement for athletes and weightlifters advertises that it is the best because it is made of “100% natural organic corn protein”. Why would this not be a good product for athletes and weightlifters?