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?