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ENZYMES. http://www.kscience.co.uk/animations/model.swf. http://www.kscience.co.uk/animations/ectopeptidase.swf. http://www.kscience.co.uk/animations/enzyme.swf http://www.youtube.com/watch?v=XTUm-75-PL4.

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Enzymes

ENZYMES

http://www.kscience.co.uk/animations/model.swf

http://www.kscience.co.uk/animations/ectopeptidase.swf

http://www.kscience.co.uk/animations/enzyme.swf

http://www.youtube.com/watch?v=XTUm-75-PL4


Enzymes

In all metabolic activities of our body and cells, lots of small molecules called ENZYMES work.

If we destroy enzymes in the body, all reactions will slow down and stop.

Because enzymes reduce activation energy of the reactions.

The minimum amount of energy that is needed to start the reaction is called ‘ ACTIVATION ENERGY ’


Enzymes

Substance which is used to decrease the activation energy of a reaction is called ‘ CATALYSTS ’ . Enzyme is a catalyst which is found in living organisms ; It REDUCES the activation energy and makes reaction FAST and EASY


Enzymes

Heat can also decrease activation energy, but in cells heat can harm/denature molecules, so instead of heat enzymes speed up reactions.

Usually they are named as:

Enzyme that breaks down sucrose : SUCRASE

Enzyme that breaks down lipid : LIPASE

Sometimes they have special names .

For example : The enzyme that breaks down starch is called amylase.

-ase


Enzymes

STRUCTURE OF ENZYMES

  • Enzymes are PROTEINS. Enzyme synthesis is controlled by DNA (genes)

  • But in most enzymes protein part joins with other molecules. (SIMPLE AND COMPLEX ENZYMES)


Enzymes

COFACTOR( mineral )

Activated enzymeAPOENZYME + or

( HOLOENZYME ) COENZYME( vitamin )

1. Enzymes acts on their SUBSTRATES. A SUBSTRATE is the molecule that is affected by enzymes.

Enzyme+Substrate→ Enzyme-Substrate Complex → Enzyme + Products


Enzymes

substrate

c.

Active site

b.

Apoenzyme

a.

Enzyme-subtrate complex

d.

Products

f.

Enzyme-subtrate complex

e.


Enzymes

Properties of enzymes:

1. Each enzyme has a specific substrate .

2. The site that binds to substrate is called as ACTIVE SITE . The relation between an enzyme and its substrate is called LOCK AND KEY MODEL

3. The enzyme isn’t SPENT during reaction(only used), So it can be used MANY TIMES. (never changed)


Enzymes

4. Reactions of Enzymes are Reversible.(not digestive ones)

Starch+ amylase enzymeglucose+ enzyme

5. Enzymes can’t work unless being water less than %15

6. Enzymes can work as a team. (ex.in digestion)

7. Enzymes are produced inside the cell but they can work inside OR outside of the cell.

8.Enzymes start their action from the outer surface of the substrate.


1 temperature

1.TEMPERATURE :

At lower temperature ;the reactions slows down or stops but as the temperature increases the rate of the reaction increases until optimum. But denatures after 60 C.

The factors that affect enzyme activity


Enzymes

2.pH :

Each enzyme works best at a certain pH ,that is called optimum pH.

( Ex: Optimum pH=2 in the stomach for digestion )

Enzymes are (denatured) broken down above or below the optimal pH.

1 2 3


3 water

3. WATER

Enzymes can’t work unless being water less than %15.

Ex : Dry plant seeds can’t germinate


4 concentration of enzyme

4.CONCENTRATION OF ENZYME

Increasing the enzyme concentration increases the rate of reaction.

But after all substrate molecules are used and no change will be in the rate of reaction


5 concentration of substrate

5.CONCENTRATION OF SUBSTRATE

If we increase the concentration of substrate, the rate of the reaction increases. But after all enzyme molecules are full, they can not change the rate of reaction.


6 surface area of the substrate

6. SURFACE AREA OF THE SUBSTRATE

increasing the surface area of substrate,increases the activity of enzymes

Substrate surface


Enzymes

For example ; if we cut meat into pieces to make the surface bigger. Minced meat is digested easier than a piece of meat.

Enzyme activity


6 inhibitors

6.INHIBITORS

Some chemicals like Mercury (Hg) slows or completely stops the activity of enzymes . These molecules are inhibitors .

Reaction rate

Enzyme

Enzyme+

inhibitor


7 activators

7.ACTIVATORS

Some chemicals increase the activity of enzyme and they are called activators

Rate of the reaction

With Activator

Without activator


Enzymes

I

K + M N + O + M

II

By looking at the reaction above, answer the questions.

a. What kind of a reaction is I and II ?

b. Which of them is the enzyme?WHY?

c. Which of them is the product and substrate?


Enzymes

Fresh liver Liver grounded Liver boiled

pieces in mortar in water

2 ml of H202 solution is placed in each tube. Fresh , grounded and boiled liver are placed in the tubes as shown in the figure.

a. Write the reaction of equation?

b. Write the correct order of reaction rates from the fastest to the slowest ?

Explain the reasons

H202

H202

H202


Enzymes

  • Enzyme 1 Enzyme 2 Enzyme 3

  • X Y Z M

  • As you see in the above reaction, some chemical reactions can ocur in chains. They follow each other. What is the advantage of this working together?

  • Reactions can be reversible(occur in BOTH ways)

  • Activation energy is lowered

  • Reaction speeds up

  • Types of products increases

  • Amount of substrate used is reduced. (decreases)


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