Enzymes Flashcards
What do enzymes do?
They speed up chemical reactions by acting as biological catalysts.
What is an important feature of a catalyst?
It speeds up a chemical reaction without being used in the reaction itself.
Name a toxic by-product of several cellular activities and the enzyme that catalyses the breakdown of it.
Hydrogen peroxide (H2O2) / Catalase
Name an extracellular enzyme and where it is found.
Amylase. Produced by the salivary glands and pancreas, Found in saliva and pancreatic juices in the small intestine.
What extracellular enzyme is found outside the body and where?
Amylase in saliva, secreted by cells in the salivary glands.
What type of protein in trypsin?
Where is it produced?
What does it do?
1) Protease
2) Cells in the pancreas and secreted into the small intestine.
3) Catalyses the hydrolysis of peptide bonds.
A substrate bound to an enzyme becomes…
Enzyme-substrate complex
A substrate bound to an enzyme becomes an …
Enzyme-substrate complex
What is the term given to the amount of energy that is required by chemcials for a reaction to start?
Activation energy
Give two examples of how forming an enzyme-substrate complex lowers activation energy.
1) If two substrate molecules need to be joined, attaching them to the enzyme holds them close together. Thus reducing the repulsion between the molecules.
2) If the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on the bonds in the substrate.
Give two examples of how forming an enzyme-substrate complex lowers activation energy.
1) If two substrate molecules need to be joined, attaching them to the enzyme holds them close together. Thus reducing the repulsion between the molecules. 2) If the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on the bonds in the substrate.
Name the two models of enzyme action.
Lock and Key / Induced Fit
How is the induced fit hypothesis different from the lock and key hypothesis?
The lock and key hypothesis state that the substrate fits perfectly into the enzyme, like a lock and a key would. This is in contrast with the induced fit hypothesis, which states that both the substrate and the enzyme will deform a little to take on a shape that allows the enzyme to bind the substrate.
What type of proteins are enzymes?
Globular
Why do enzymes have a tertiary structure?
It allows them to create a specific 3D shape which is required for them to create an active site specific to the substrate.
What 4 factors affect enzyme activity?
1) PH 2) Temperature 3) Enzyme Concentration 4) Substrate Concentration
What effect does temperature have on enzyme activity?
More heat = more kinetic energy = more likely for substrate chemicals to collide with ezymes.
The ideal temperature is called?
Optimum temperature.
What happens if the temperature is too great?
The enzyme molecules vibrate too much and some of the bonds that hold the enzyme in shape are broken. The enzyme becomes denatured.
When an enzyme breaks down it becomes…?
Denatured
pH can affect the tertiary structure of an enzyme. Why?
The H+ and OH- ions can break the hydrogen and ionic bonds causing the enzymes active site to change shape.
Name the two types of cofactors.
Inorganic / Organic (coenzymes)
What do inorganic cofactors do and do not do?
They help bind the substrate and enzyme together. They do not participate in the reaction.
What role to organic cofactors play?
They participate in the reaction and are continually recycled.
If a cofactor is tightly bound to an enzyme it is called a?
Prosthetic group.
Competitive and non-competitive inhibitors
Competitive inhibitors bind to the active site. Non-competitive inhibitors bind away from the active site (allosteric site) which causes the active area to change shape.
How can you reverse the effects of a competitive inhibitor?
Increase the concentration of the substrate.
What determins if a inhibitor is reversible or not?
The strength of the bonds between the enzyme and inhibitor.
What type of bond attributes to a irriversible inhibitation.
Strong covalent bond.
What type of bond attributes to a reversible inhibitation.
Weak hydrogen or ionic bonds.
What type of drug is used to target HIV?
Enzyme inhibitor which inhibits the enzyme reverse transcriptase from catalysing the replication of viral DNA.
How does penicillin work?
It inhibits the enzyme transpeptidase which catalyses the formation of proteins (peptidoglycan) in the cell wall. The cell wall becomes weak and prevents the bacterium from regulating its osmotic pressure causing it to burst.
Human cells do not make or need peptidoglycan.
Describe the breakdown of starch.
1) Starch polymers partially are broken down into maltose by amylase.
2) Maltose is broken down into glucose by maltase.
3) Glucose absorbed by cells in the digestive system and then absorbed into the blood.
All of the below can only happen as a result of enzymes.
Describe:
1) Metabolisim
2) Annabolism
3) Catabolism
1) The sum of all the different reactions in a cell or organism.
2) Building of molecules.
3) Breaking down of molecules.
