Transcript Enzymes what are they - Laurel County Schools

What are they?
Enzymes
Why do we need them?
Name some examples ?
Enzymes
Globular proteins that catalyse chemical
reactions in living organisms
Enzymes
Globular proteins that catalyse chemical
reactions in living organisms
Properties
Specific
Increase rate of the reaction
Unchanged at the end of the reaction
Enzymes
Need them because...
Reactions too slow to maintain life
Can’t increase temperatures/pressure
in cells (fatal)
Enzymes Are Proteins
The enzyme binds to the substrates
by its active site
The active site is a pocket formed by the
folding of the protein
where the substrates bind.
Enzymes Are Proteins
The enzyme binds to the substrates by its active site
The active site is a pocket formed by the folding of the
protein
where the substrates bind.
Active site
The active site involves a small number of key residues that
actually bind thesubstrates
The rest of the protein structure is needed to maintain these
residues in position
Lock and Key
Enzyme reactions
enzyme + substrate
enzyme-substrate complex
Enzyme reactions
enzyme + substrate
E +S
enzyme-substrate complex
ES
Enzyme reactions
enzyme + substrate
enzyme-substrate complex
E +S
ES
enzyme-substrate complex
ES
enzyme + product
E +P
How do enzymes work?
An Example
An Example
Sucrose + H2O
Glucose + Fructose
An Example
Substrates
Sucrose + H2O
Glucose + Fructose
Products
For a reaction to occur the sucrose
and water would have to collide with
enough energy to break and form bonds
This is the activation energy
Sucrose + H2O
+
Substrates
Glucose + Fructose
+
Products
Energy
Progress of reaction
Energy
Substrates
Progress of reaction
Energy
Substrates
Progress of reaction
Products
High energy
intermediate
Energy
Substrates
Progress of reaction
Products
High energy
intermediate
Activation energy
Energy
Substrates
Progress of reaction
Products
The minimum amount of energy
needed to start the reaction,
leading to the formation of a high
energy intermediate
= The Activation energy
High energy
intermediate
Activation energy
Enzymes reduce the
height of the energy
barrier
Energy
Substrates
Progress of reaction
Products
Enzyme activity
How fast an enzyme is working
Rate of Reaction
Rate of Reaction = Amount of substrate
changed (or amount product formed)
in a given period of time.
Enzyme activity
Temperature
pH
Four Variables
Enzyme Concentration
Substrate Concentration
Temperature
5- 40oC
Increase in Activity
Rate of Reaction
40oC - denatures
0
<5oC - inactive
10
20
30
40
50
60
Effect of heat on enzyme activty
If you heat the protein above its optimal temperature
bonds break
meaning the protein loses it secondary and tertiary structure
Effect of heat on enzyme activty
Denaturing the protein
ACTIVE SITE CHANGES SHAPE
SO SUBSTRATE NO LONGER FITS
Even if temperature lowered – enzyme
can’t regain its correct shape
pH
Rate of Reaction
Narrow pH optima
Disrupt Ionic bonds - Structure
Effect charged residues at active
site
1
2
3
4
5
6
7
8
9
Rate of Reaction
Enzyme Concentration
Enzyme Concentration
Substrate Concentration
Rate of Reaction
Active sites full- maximum turnover
Substrate Concentration
What is digestion?
Breaking down large, insoluble
molecules into smaller, soluble
molecules that can be absorbed through
the wall of the small intestine
What breaks down the large molecules?
Digestive enzymes made by
specialised cells inside glands
Some enzymes are...
Amylase
Carbohydrates
Protease
Lipase
Proteins
Lipids
The enzymes break down...
Carbohydrates
Proteins
Lipids (fats)
Digestion animation
Simple sugars
Amino acids
Fatty acids + glycerol
What does bile do?
• Bile is produced in the liver and stored in
the gall bladder.
• The enzymes in the small intestine need
an alkaline pH to work best, so bile passes
into the small intestine and neutralizes
acid from the stomach.
• Bile also emulsifies fat droplets to increase
their surface area
Why do you think there is acid in
the stomach?
• Kills bacteria in food – protects us
• Denatures proteins – makes digestion easier
• Activates stomach enzymes – these only
work in acidic conditions
• Ever wondered why PEPSIN (stomach
enzyme) doesn’t digest our own stomach?
• Pepsin is inactive when first made and is only
activated by HCL to start digesting proteins.
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