Enzymes Flashcards
What is the structure of all enzymes?
3D globular proteins in the tertiary structure
Why do enzymes hold their shape?
They hold their shape due to hydrogen, ionic and disulphide bonds
What effects the activity of enzymes?
Temperature and pH
What is the function of enzymes?
To work as a biological catalyst - speed up chemical reactions without being used up
Are enzymes specific or not specific?
Specific
What is an example of the use of enzymes in the body?
Used in digestion to hydrolyse polymers into monomers
What is the definition for activation energy?
The excess energy needed to enable a reaction to occur
What do enzymes do to the activation energy?
Lowers the activation energy
What is the pocket cleft on an enzyme?
A specific shape on the enzyme called an active site
What is complementary to the active site of an enzyme?
The complementary substrate
Can any enzyme break down any substrate?
No, only specific enzymes can break down specific substrates
What is an example of the lock and key model enzyme used in the body?
Lactase breaking down lactose into glucose and galactose
Can the lock and key model of enzymes catalyse both ways of a reaction?
Yes
What holds the substrate to the enzyme in the lock and key model?
Oppositely charged groups on the amino acids in the active site
What are the 6 steps to the induced fit model for enzymes?
- The substrate collides with the active site.
- The active site moulds around the substrate molecule and it is held in position by oppositely charged groups on the amino acids in the active site.
- An enzyme-substrate complex is formed.
- An enzyme-product complex now forms.
- The product no longer fits into the active site.
- The product is released.
What is the function of binding during the induced fit model in enzymes?
Binding the substrate to the active site results in a change of shape in the enzyme so that it fits around the substrate more closely.
Is the active site the same shape as the substrate?
The active site is NOT the same shape as the substrate but it is complementary.
Do substrates have active sites?
No
Define a Catabolic reaction
The break down of larger molecules into smaller ones
What is an example of a catabolic reaction?
Polypeptide into an amino acid
Define a Anabolic reaction?
Large molecules made from smaller units
What is an example of anabolic reaction?
Alpha glucose into startch
What is a intracellular enzyme?
A type of enzyme found inside the cell
What is a extracellular enzyme?
A type of enzyme released outside cell
What is glucose isomerase?
A type of enzyme
What is pepsin?
A type of enzyme
Define turnover number
The number of converted molecules of substrate per unit of time
ENZYME + SUBSTRATE =
Product - if a successful collision leading to a enzyme-substrate complex
What are the three main ways enzyme reactions can be measured?
- Time taken for reaction to occur
- Number or concentration of products produced
- Rate of reaction
Why is rate of reaction slower at lower temperatures?
There are fewer successful collisions so fewer enzyme-substrate collisions taking place and therefore less product made.
How does an increase in temperature effect the rate of reaction?
Increased temperature results in increased kinetic energy of molecules which increased the rate of collision and the enzyme-substrate complexes.
When is the shorted amount of time taken in a reaction?
When the optimum temperature reacted
What happens to the rate of reaction when applying heat above the optimum temperature?
Applying heat above the optimum temperature will cause the enzyme to vibrate more causing the hydrogen and ionic bods that hold it together to break.
What is meant by ‘denaturing an enzyme’?
When the globular shape of an enzyme is altered which will alter the shape of the active site.
What is pH?
A measure of the hydrogen ion concentration
Does increasing the concentration of H+ ions make the pH higher or lower?
Lower
What is used when testing for the optimum pH?
A pH buffer solution of different pH’s can be used
What is the function of enzyme inhibitors?
To reduce the rate of reaction
What are the two types of enzyme inhibitors?
Competitive Inhibitor
Non-competitive inhibitor
How do competitive enzymes work?
They bind with the active site forming an enzyme- inhibitor complex and prevent the normal substrate from being broken down by blocking the active site.
What is the effect of a competitive enzyme?
It reduces the number of E-S complexes and thus the rate of reaction drops.
What is the shape of a competitive enzyme similar to?
The molecule substrate
How long does the inhibition caused by competitive enzymes last?
Temporarily
How do non-competitive enzymes work?
They do NOT compete for the active site, instead they attach to the ALLOSTERIC SITE, changing this tertiary structure of the protein and thus a change in the active site. This change in shape means he substrate no longer fits in the active site, so rate of reaction decreases.
What is a case study of a non-reversible inhibitor and what does it cause?
Potassium Cyanide, inhibits respiration
Where are enzymes produced? How does this process work?
By culturing microbes in fermentation, the enzymes are produced as part of the microbes normal metabolic activity.
Enzymes are then extracted, purified and used
What enzyme is extracted from Fungus Streptomycin? What is it used in?
Glucose isomerase - Coca-Cola
What enzyme is extracted from Bacillus Bacterium? What is it used in?
Protease- used in Persil detergent
What enzyme is extracted from Nucor Fungus? What is it used in?
Rennin - Vegetarian Cheese
What enzyme is extracted from Aspergillums Fungus? What is it used in?
Pectinase- Alcohol and Juice Concentrate
What 3 reasons are enzymes used in large scale industry?
- Lower activation energy of reactions
- Speed up rate of reaction
- Less waste products produced
What are the three steps to enzyme immobilisation?
- Substance are trickled through top vessel
- Enzymes immobilised in breads
- Products are collected from the bottom
What are five advantages of enzyme immobilisation?
- Ennzymes are easily recovered, so can be reused
- Products is not contaminated by the enzyme
- Enzyme has a microenvironment so its more stable in extreme temperatures and pH
- Used in continuous reactions/ processes
- Several enzymes can be used together
What are five disadvantages of enzyme immobilisation?
- In absorption the enzyme may become detached and contaminate the product
- The time it takes for the enzyme to diffuse into the immobilising substrate (Free enzymes work faster)
- The presence of alginate gel (the immobilising substrate) alters the shape of the active shite reducing activity
- Chemically bonding an enzyme is complicated and expensive
- Any contamination is expensive
What are the four methods of immobilising enzymes?
- Chemically bonded cross links using Glyoraldhyde
- Absorption of enzyme onto glass beads, clay particles or collagen
- Entrapment
- Encapsulation in alginate beads
What is a biosensor?
An instrument that can detect a specific molecules in a mixture of molecules
What does a biosensor do?
Couples a biochemical reaction to an electronic meter
Why do biosensors work?
Because enzymes are specific
When are biosensors used in industry?
In medical and environmental monitors
How do biosensors work?
Uses an enzyme and a transducer. When the substrate is converted into the product this change is detected and the electrical signal is read on a monitor
What does a bioreceptor (immobilised enzyme) do in a biosensor?
Binds to the specific molecule being detected by the biosensor?
What does a transducer do in a biosensor?
Coverts the products into an electrical signal
What does a amplifier do in a biosensor?
Magnifies the strength of the electrical signal so it can be measured by a meter
How is Mg^2+ used in humans and plants?
In humans Mg2+ is used to catalyse the synthesis of ATP.
In plants it is used for the synthesis of chlorophyll and photosynthesis.
How is Fe^2+ used in humans ?
In red blood cells to help make up part of the haemoglobin which bonds the oxygen to the cell. Iron also helps the production of red blood cells and the conversion of blood sugar
How is Ca^2+ used in humans?
Calcium ions are stored in the bone. They help to be a messenger for neurotransmitters released from neurons, muscle contractions and fertilisation.
How is PO4^3- used in humans and plants?
Used for making nucleotides with calcium. Makes calcium phosphate that gives bones their strength.
