Proteins are made of amino acids and their structure and function are determined by their sequence and folding. There are four levels of protein structure: primary, secondary, tertiary, and quaternary. Enzymes are proteins that catalyze biochemical reactions and examples include hydrolases and lactase. The structure and function of enzymes can be affected by factors like temperature, pH, and inhibitors. An enzyme lab was described that extracts the enzyme tyrosinase from mushrooms to test its reaction rate under normal and altered conditions.
4. Protein Structure
The structure of proteins are important because
1. Proteins make up what our cells look like
2. Proteins carry out important functions in the cell
5. Special Proteins
Proteins that catalyze reactions (which means speed up
reactions) are called enzymes
Examples of enzymes picture
Tyrosinase Hydrolase Lactase
6. Four Levels of Protein Structure
Primary Structure (1o structure)
The order and number of amino acids strung together aka
a polypeptide chain.
7. Four Levels of Protein Structure
Secondary Structure (2o structure)
Common shapes found in all proteins made from hydrogen
bonds such as alpha helices and beta pleated sheets
8. Four Levels of Protein Structure
Tertiary Structure (3o structure)
The three dimensional (3-D) structure of amino acids
9. Four Levels of Protein Structure
Quaternary Structure (4o structure)
2 or more polypeptides that are folded in a 3D shape and
combined together
10.
11. Warm-up
* Check bacteria paintings in incubator
What are special proteins that speed up reactions called?
Study Guide Questions
#2 What is the general equation for photosynthesis
#7 What are the 3 differences between mRNA and DNA
#10 What is mRNA and tRNA? What is their structure and
function in the cell?
Announcements:
Participation Pts announcement
Honors HW due Tomorrow
9 Days until Exam
Lab Notebooks
12. Protein Function
• Made by all living things to perform these
functions:
o Structural: Hair and muscles
o Immunity: Antibodies
o Signaling and communication:
Neurotransmitters and hormones.
o Transport: Ion channels
o Enzymes: Catalyze (speed up) biochemical
reactions
14. Enzymes are the Construction
Workers of the Cell…
Enzymes help
BUILD UP or BREAK DOWN
molecular structures
15. Catalysts
• Catalysts speed up chemical reactions by lowering the
activation energy and are not used up in the reaction.
16. How do catalytic enzymes work?
• Substrate binds a region of the enzyme called the active
site (a pocket formed by the folding of the protein
enzyme that is highly specific for the substrate).
17. Enzymes are usually named with the suffix –ase
added to the name of the substrate or reaction
Inhibitors
slow down
enzymes!
Paperclipase Toothpickase
18. Changing how enzymes work
We can change the enzymes ability to catalyze (speed up)
a reaction in two ways:
1. Denaturation – protein unfolding into the 1o structure
1. Inhibition – preventing an enzyme from functioning
1. Competitive inhibitors – block the active site so that the substrate
can not bind
2. Non-competitive inhibitors - bind to the enzyme and make them
unable to bind the substrate
19. Why care about enzymes?
• Enzyme that helps muscle cells communicate with the
nervous system.
• Nerve Gas inhibits acetylcholinesterase
o Enzyme is used to break down the neurotransmitter acetylcholine.
o When it is inhibited, paralysis and death follow.
http://ucsdnews.ucs
d.edu/newsrel/healt
h/nihgrants06.asp
20. Why care about enzymes?
Myasthenia Gravis is an autoimmune disease that causes an individual
to suffer from severe muscle weakness. This weakness is caused by a
decreased amount of nicotinic acetylcholine receptors in the
neuromuscular junction. These receptors normally are activated by the
neurotransmitter acetylcholine, which is also deactivated by an enzyme
called acetylcholinesterase. By inhibiting acetylcholinesterase, more
acetylcholine is available to the receptors and a normal ratio of
receptors to neurotransmitters is established and the muscles can
function normally. In this video a myasthenic dog, who normally has
trouble walking, is treated with an acetylcholinesterase inhibitor and
can walk and even run normally until the inhibition wears off.
22. Objective
To extract the enzyme Tyrosinase from a Portobello
mushroom in order to test the reaction rate of the enzyme
in normal conditions and compare it to conditions where
the enzyme is exposed to inhibitors, increased
temperature, or changes in pH.
33. The Lab – Experimental Trials
3 Different Experimental Trials
- pH
- Inhibitor
- Temperature
34. The Lab – Experimental Trial
pH
- Test the pH of L-DOPA
- Test the pH of L-DOPA after you add HCl
- Start the reaction
Tyrosinase + L-DOPA = Dopachrome + Tyrosinase
0.1
ENZ ml EXP EXP
+
= ?
HCl
38. The Lab – Experimental Trial
Temperature
-Heat 0.1 ml of L-DOPA in EXP tube for 1
min. in water
- Add L-DOPA and start the experiment
0.1 ml Tyrosinase ?
EXP EXP
=
EXP
L-DOPA
40. Graphing!
X = time in seconds
Y = mM of Dopachrome
Sample
2.5
Control Enzyme Reaction
2
1.5
1 Control Enzyme
Reaction
0.5
0
100
120
140
160
180
240
300
360
10
20
30
40
50
60
80
Notes de l'éditeur
Pictures from Sara Dozier
Albinism: The lack of tyrosinase
Go over roles and demo what each person needs to do in each role. Go over chart reading etc.
