PROTEINS

ProteinsA protein is made of monomers called amino acids

ProteinProtein structure is determined by the number and order of amino acids

Protein StructureThe structure of proteins are important because

1. Proteins make up what our cells look like

2. Proteins carry out important functions in the cell

Special Proteins

Proteins that catalyze reactions (which means speed up reactions) are called enzymes

Examples of enzymes picture

Tyrosinase Hydrolase Lactase

Four Levels of Protein Structure

Primary Structure (1o structure)

The order and number of amino acids strung together aka a polypeptide chain.

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

Four Levels of Protein Structure

Tertiary Structure (3o structure)

The three dimensional (3-D) structure of amino acids

Four Levels of Protein Structure

Quaternary Structure (4o structure)

2 or more polypeptides that are folded in a 3D shape and combined together

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

Protein Function• Made by all living things to perform these

functions:o Structural: Hair and muscleso Immunity: Antibodieso Signaling and communication:

Neurotransmitters and hormones.o Transport: Ion channelso Enzymes: Catalyze (speed up) biochemical

reactions

Enzymes in our daily lives:

PROTEASE

HYDROLASE LACTASE

Enzymes are the ConstructionWorkers of the Cell…

Enzymes help BUILD UP or BREAK DOWN

molecular structures

Catalysts• Catalysts speed up chemical reactions by lowering the

activation energy and are not used up in the reaction.

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).

Enzymes are usually named with the suffix –ase added to the name of the substrate or reaction

Inhibitorsslow downenzymes!

Paperclipase Toothpickase

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

2. 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

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.ucsd.edu/newsrel/health/nihgrants06.asp

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.

ENZYME LAB

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.

The Enzyme Tyrosinase

Tyrosinase is an enzyme that causes pigmentation in apples, skin, hair, etc.

The Enzyme Tyrosinase

The Enzyme Tyrosinase

Albinism

Heat-Sensitive Tyrosinase

The Reaction

General Enzyme-Substrate Reaction

Enzyme + Substrate = Product + Enzyme

General Tyrosinase ReactionTyrosinase + L-DOPA = Dopachrome + Tyrosinase

+=

The Lab

3 Main Parts of the Tyrosinase Enzyme Lab1. Enzyme Extraction

2. Control Reaction

3. Experimental Reaction

The Lab – Enzyme Extraction

1a. Break open the cell to free Tyrosinase

The Lab – Enzyme Extraction

1b. Filter out the solid chunks of mushroom

The Lab – Control Reaction

4 roles (demo):

- Mixer - Reader

- Timer - Recorder

Tyrosinase + L-DOPA = Dopachrome + Tyrosinase

+=

0.1 mlENZ CTL CTL

Tyrosinase + L-DOPA = Dopachrome (pigment)

Measure Product

Enzyme Substrate Product+ =

The Lab – Experimental Trials3 Different Experimental Trials

- pH

- Inhibitor

- Temperature

The Lab – Experimental Trial

pH

Tyrosinase + L-DOPA = Dopachrome + Tyrosinase

+=

0.1 ml

- Test the pH of L-DOPA- Test the pH of L-DOPA after you add HCl- Start the reaction

HCl

?ENZ EXP EXP

Tyrosinase + L-DOPA + HCl = Dopachrome (pigment)

Measure Product

Enzyme Substrate Product+ =

The Lab – Experimental Trial

Inhibitor

- Add Inhibitor

- Start the reaction

Tyrosinase + L-DOPA = Dopachrome + Tyrosinase

+=

0.1 ml

Inhibitor

?EXP EXPENZ

Tyrosinase + L-DOPA + INH = Dopachrome (pigment)

Measure Product

Enzyme Substrate Product+ =

The Lab – Experimental TrialTemperature

-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

L-DOPA

=

?

EXP EXP

EXP

Tyrosinase + L-DOPA + Heat = Dopachrome (pigment)

Measure Product

Enzyme Substrate Product+ =

Graphing!X = time in seconds

Y = mM of Dopachrome

10 30 50 80 120

160

240

360

0

0.5

1

1.5

2

2.5

Sample Control Enzyme Reaction

Control Enzyme Reaction