2.4 Enzymes (spec) Flashcards
What is an enzyme?
Biological catalysts that speed up metabolic reactions in living organisms
How does structure of an enzyme determine its function?
- Needs cofactors to help catalyse some reactions
- Instructions for making enzymes is encoded in its genes (if there is a mutation then the tertiary structure might be different and it won’t be complementary)
- If enzyme is deficient a metabolic disorder may occur
What are intracellular enzymes?
Metabolic reactions inside the cell
What does catabolic mean?
Breaks down
What does anabolic mean?
Builds up
What are examples of intracellular reactions?
Respiration and photosynthesis
Describe action of catalase
Protects cell from reactive oxygen by breaking down hydrogen peroxide
What is the turnover rate of catalase?
6 million per second (highest)
What are extracellular enzymes?
- Secreted by cells and made to act outside (many in digestive system - digest food molecules)
Describe the action of amylase
- Produced in salivary glands and pancreas
- Digest starch and makes maltose
Describe the action of trypsin
- Produced in the pancreas
- Acts in lumen to digest proteins into peptide by hydrolysing peptide bonds
Describe the lock and key hypothesis
- Active site is complementary to substrate
- Have kinetic energy meaning randomly collide
- When collide create enzyme-substrate complex
- Leaves as a product
Describe the induced fit hypothesis
- Enzyme is not a rigid/fixed structure
- Presence of a substrate causes shape change
- Moulding creates more effective binding
What is the effect of temperature of enzyme action?
- Extra energy causes to move faster
- Increases rate of collision/reaction
- When too hot vibrates breaking bonds and tertiary structure
What is the optimum temperature?
Temperature where the rate of reaction is at its maximum
What is the temperature coefficient?
rate of reaction at T
What does the temperature coefficient show?
There is an increase in rate when temperature is increased by 10 degrees
What are the effects of pH?
- Negative ions are attracted to positive ions
- Causes bonds to make and break losing tertiary structure of enzyme and meaning that the active site is complimentary
What is a buffer?
Chemicals that resist changes in pH
What is the effect of substrate concentration?
- No substrate = no reaction
- If all substrate is used up it becomes the limiting factor
What are prosthetic groups?
Cofactors that permanently bind by covalently
What is an example of prosthetic groups?
CO2 + H2O ——-> H2CO3 + H2 + HCO3-
Carbonic anhydrase catalyses and has zinc permanently bound
What are coenzymes?
- Small, organic protein molecules
- Temporarily bind to active site
- Just before/when substrate binds
- Chemically changes reaction
- Recycled to original state
What are examples of coenzymes?
Vitamins are a source of coenzymes
B12 contains Cobalamin Coenzymes
What are cofactors?
- Ions that are not permanently bound
- Ease formation of enzyme - substrate complex
What are co-substrates?
- Make substrate complementary to the active site
- Change charge distribution on the surface of the molecule
What is an example of a coenzyme?
Amylase digests starch to maltose
Chloride ions have to be present
What is competitive inhibition?
- Fits into the active-site so substrate cannot enter
What does relative concentration depend on?
Amount of inhibition
What is non-competitive inhibition?
- Binds to allosteric site
- Disrupts enzymes tertiary structure and is no longer complementary
- Maximum rate of reaction is reduced
What are two examples of metabolic poisons?
Cyanide
Snake venom
What is the action of cyanide?
Inhibits aerobic respiration
KCN hydrolysed to produce hydrogen cyanide (posion)
What is the action of snake venom?
Inhibits muscular synapses
Causes paralysis
What are two examples of medicinal drugs?
Aspirin
ATPase
What is the action of aspirin?
Prevents formation of prostaglandins
Stops inflammation
What is the action of ATPase?
Inhibits sodium potassium pump and allows more calcium ions to enter cells
Increases muscular contraction and strengthens heartbeat
What is product inhibition?
Products stay tightly bound to enzyme and aren’t released
What is a metabolic pathway?
Product of one reaction becomes the substrate of another
