Wednesday, September 07, 2005
BIOLOGY - Enzymes
ENZYMES
- It is a protein in nature and it speeds up rate of reaction (catalyse chemical reactions) [because it lowers activation energy]
- Required in small amounts – Not changed at the end of the reaction
- Specific in action (e.g. Lock and Key hypothesis, Induced Fit hypothesis)
- Sensitive to temperature
- Sensitive to pH
- Some need co-enzymes (come from Vitamin B)
Enzymes are important because:
1. Chemical reactions vital to life will not take place quickly enough without enzymes
2. Enzymes can control where and when the various chemical reactions take place
Types of enzymes:
1 Hydrolases
2 Oxidation-reduction (dehydrogenase)
HYDROLASES
-Carbohydrases act on carbohydrates
-Lipases act on fats
-Proteases act on proteins
-Catalase breaks down H2O2(hydrogen peroxide, poisonous) to H2O and O2
Carbohydrases:
a) Amylase (e.g. pytalin in saliva) breaks down starch into maltose
b) Maltase (in small intestine) breaks down maltose into glucose
Lipases:
They break down fats/lipids into fatty acids and glycerol.
Proteases:
a) Pepsin breaks down proteins into polypeptides
b) Peptidase breaks down polypeptides into amino acids
How do enzymes work?
Lock and Key hypothesis (1890)
- Specificity
- Destruction by heat
- Inactivation by poisons
Induced Fit hypothesis (1959)
Substrate: A substance on which enzymes act on
Coenzyme: A compound required by an enzyme before they can catalyse a reaction
Optimum Temperature/pH: The temperature or pH at which the enzyme works best
Limiting factor: Any factor that directly affects a process if its quantity is changed
Effects of temperature:
à There is an optimum temperature for every enzyme
à An enzyme is generally inactive at low temperatures
à Every 10˚C brings about twice the activity
à When the temperature is too high:
- Enzyme structure affected
- Protein denatured
- Enzyme denatured
Types of enzyme inhibitors:
Reversible inhibitors: bind less tightly to enzymes
Irreversible inhibitors: bind tightly to enzymes
Competitive inhibitors: bind to active site
Non-competitive inhibitors: bind to other site (not active site), change the shape of/block access to active site (e.g. cyanide poison)
OXIDATION-REDUCTION enzymes
- For respiration
-- HH! ((: I DON'T UNDERSTAND HAHAHAHA.
- It is a protein in nature and it speeds up rate of reaction (catalyse chemical reactions) [because it lowers activation energy]
- Required in small amounts – Not changed at the end of the reaction
- Specific in action (e.g. Lock and Key hypothesis, Induced Fit hypothesis)
- Sensitive to temperature
- Sensitive to pH
- Some need co-enzymes (come from Vitamin B)
Enzymes are important because:
1. Chemical reactions vital to life will not take place quickly enough without enzymes
2. Enzymes can control where and when the various chemical reactions take place
Types of enzymes:
1 Hydrolases
2 Oxidation-reduction (dehydrogenase)
HYDROLASES
-Carbohydrases act on carbohydrates
-Lipases act on fats
-Proteases act on proteins
-Catalase breaks down H2O2(hydrogen peroxide, poisonous) to H2O and O2
Carbohydrases:
a) Amylase (e.g. pytalin in saliva) breaks down starch into maltose
b) Maltase (in small intestine) breaks down maltose into glucose
Lipases:
They break down fats/lipids into fatty acids and glycerol.
Proteases:
a) Pepsin breaks down proteins into polypeptides
b) Peptidase breaks down polypeptides into amino acids
How do enzymes work?
Lock and Key hypothesis (1890)
- Specificity
- Destruction by heat
- Inactivation by poisons
Induced Fit hypothesis (1959)
Substrate: A substance on which enzymes act on
Coenzyme: A compound required by an enzyme before they can catalyse a reaction
Optimum Temperature/pH: The temperature or pH at which the enzyme works best
Limiting factor: Any factor that directly affects a process if its quantity is changed
Effects of temperature:
à There is an optimum temperature for every enzyme
à An enzyme is generally inactive at low temperatures
à Every 10˚C brings about twice the activity
à When the temperature is too high:
- Enzyme structure affected
- Protein denatured
- Enzyme denatured
Types of enzyme inhibitors:
Reversible inhibitors: bind less tightly to enzymes
Irreversible inhibitors: bind tightly to enzymes
Competitive inhibitors: bind to active site
Non-competitive inhibitors: bind to other site (not active site), change the shape of/block access to active site (e.g. cyanide poison)
OXIDATION-REDUCTION enzymes
- For respiration
-- HH! ((: I DON'T UNDERSTAND HAHAHAHA.
# we mugged! @ 1:26 AM 
