Download Document

CHAPTERS 2.14-2.18
PROTEINS
Ms. Doshi
What do Proteins do?
Enzyme
-a special protein
-starts and help in every chemical reaction in the
body.
Protein Structure
proteins
-are made of amino acids. There are 20 amino
acids.
-4 atoms: C, N, O, H
2.15 Protein in Food I
We should eat essential amino acids every day.
Complete proteins have all essential amino
acids.
Incomplete proteins do not have all essential
amino acids.
Proteins in Food II
Complete Proteins
milk
eggs
fish
chicken
beef
Incomplete Proteins
vegetables
fruit
grains
Complete vs. Incomplete Proteins
2.16 Protein Terms
peptide bond
-the bond between one amino acid and another
dipeptide
-2 amino acids bond together
polypeptide
-many amino acids bond together
Structure of Proteins
primary structure
-amino acid polypeptide chain
secondary structure
-zigzag or corkscrew-like structure
-formed by H bonds
tertiary structure
-3D shape
-formed by H bonds or covalent S-S bonds
quaternary structure
-two or more polypeptide chains together
-Example: Hemoglobin
4 polypeptide chains: 2 alpha and 2 beta chains
Structure of Proteins
Proteins + Other macromolecules
Lipoproteins
-lipid + proteins
-carry fat in blood
Glycoproteins
-carbohydrates + proteins
-help the immune system distinguish between
your own cells and foreign cells.
Protein Structure and Function
Proteins need 3D shape to function.
If lose 3D shape, proteins cannot function.
denaturation:
When a protein unfolds.
Examples:
fry an egg (H bonds break)
Raw egg (clear part) becomes white when add
baking soda or rubbing alcohol.
Perm (Hair)
How do you do this?
Break H bonds and covalent bonds in your hair
chemically.
Wrap hair in curlers to hold polypeptide chains
in a different position.
Chemicals are put in the hair to create new
covalent bonds between parts of polypeptide
chains.
Hair is locked in a new position.
Questions
With a partner do these questions. You have 20 minutes.
1. What do proteins do?
2. What is an enzyme? What does an enzyme do?
3. Proteins are made of ___________.
4. The three parts of a protein are: _____________.
5. What are the atoms in a protein?
6. What is the difference between complete proteins and
incomplete proteins?
7. Milk and eggs have ______ proteins.
8. Fruits and vegetables have _____ proteins.
9. Define: peptide bond, dipeptide, polypeptide, the different
structures of proteins, lipoprotein, and glycoprotein.
10. What happens to a protein when it is denatured?
2.7 Enzyme Terms
enzymes
-‘special’ proteins
-start and help with chemical reactions in our bodies
-they do not change in the chemical reaction
active site
-the place in an enzyme where the substrate sits
substrate
-reactants of a chemical reaction
activation energy
-minimum energy needed to start a chemical reaction
Enzyme-Substrate (Lock & Key)
2.18 Enzyme Activity
Enzymes, act as catalysts. They lower the
activation energy so that a reaction can occur
quickly.
What affects enzyme rate?
Enzyme and Substrate Concentration
(amount of enzyme or substrate in the chemical
reaction)
Temperature
pH
Inhibitors (turns off enzymes)
Activators (turns on enzymes)
Competitive Inhibitor
vs. Noncompetitive Inhibitor
Competitive Inhibitor
-binds to the active site and blocks substrate from
the site.
Non-competitive inhibitor
-binds to a part of the enzyme that is not the active
site. Changes the shape of the active site. Substrate
cannot bind to the active site.
Pictures on next slide…
Competitive Inhibitor vs.
Noncompetitive Inhibitor
Non-functioning Enzymes
-leads to disease and
physiological problems
Example:
PKU (phenylketonuria)
-body cannot breakdown
phenylketonuria
Lactose Intolerance
The enzyme, lactase, is needed to breakdown lactose.
In some adults, lactase is no longer made, which leads
to stomach problems.
To help feel better,
These adults do not eat or drink: milk, yogurt, ice
cream and other dairy products.
Some adults can take the enzyme, lactase, as a pill.
Questions
1. Define: active site, substrate, activation
energy
2. What affects the rate of enzyme activity?
3. What is the difference between a
competitive inhibitor and non competitive
inhibitor?
4. What do activators do?
5. What does a non-functioning enzyme do?