enzymes

Question 1

4 enzyme properties

Answer 1

• a catalyst that changes rate of reaction without partaking in reaction (decreases Ea)
• a type of catalytic protein
• highly specific (to reaction & substrate)
• great catalytic power (>10^6)

Question 2

enzyme functions in eye (5)

Answer 2

• visual transduction
• intraocular pressure
• deturgescence
• bacteria removal
• lens fibre cell development

Question 3

what is Michaelis constant (Km)

Answer 3

Km is substrate concentration yielding a velocity of Vmax/2

Question 4

what are intercepts and slope of Lineweaver-burke plot

Answer 4

x int: -1/Km
y int: 1/Vmax
slope: Km/Vmax

Question 5

allosteric enzyme properties

Answer 5

• doesn’t obey Michaelis-Mentin kinetics
• 4 subunits
• regulatory molecules (inhibitors or activators) can alter enzyme activity

Question 6

types of enzyme inhibition (5)

Answer 6

• reversible
• irreversible
• competitive
• non-competitive
• pharmaceutical drugs

Question 7

3 occular enzymes

Answer 7

1. Lysozyme
   - found in precorneal tear film
   - kills gram-positive bacteria (breaks glycosidic bond between repeating NAM & NAG units)
2. Aldose Reductase
   - oxidative protection and osmotic regulation
   - associated with cataract formation

• AR usually inactive until high glucose levels (diabetes) -> produces polulols -> creates osmotic imbalance in lens fibre cells -> swells and burst -> cataracts

3. Matrix metalloproteinases
   - protein hydrolases (breaks down proteins - collagen)
   - tissue maintenance and reformation

• remodels shape of ocular globe by partially digesting scleral proteins so that new proteins can be formed with new sceleral length -> can cause myopia
• removes damaged corneal proteins -> results in corneal ulcers or even removal of eye