Fuels and Biofuels: Cellular Biosystems; Enzyme Kinetics

Question 1

What is a significant difference between manmade combustion processes and biochemical reactions?

Answer 1

Biochemical reactions are slow, energetically efficient and highly controlled

Question 2

What is the unit for rate of reaction? What is the formula for this?

Answer 2

mol/(L*sec)

Rate = amount of product formed (mol/L) / time for the reaction to occur (sec)

Question 3

How does the reaction rate change with temperature? Approximately by how much every 10˚C?

Answer 3

• Reaction rates almost always increases proportionally to temperature
• Doubling every 10˚C

Question 4

Why is the temperature important?

Answer 4

For a chemical reaction to occur, the molecules need to collide and for the collisions to result in a reaction they need to have sufficient energy to break the bonds in the reactants

Question 5

What is the energy barrier for a reaction called?

Answer 5

Activation energy (Ea)

Question 6

What happens if a collision has energy that is less than the activation energy?

Answer 6

It won’t react

Question 7

How does increasing the temperature of a substance result in increased reactions?

Answer 7

The higher the temperature the greater the proportion of reactants that are greater than the activation energy

Question 8

What is the problem with constantly increasing the temperature in a biochemical reaction? What is the optimum temperature?

Answer 8

• By constantly increasing the temperature it results in damaging/denaturing proteins which can kill the cell
• 37˚C

Question 9

What is the biochemical solution to limiting the temperature while increasing the reaction rate?

Answer 9

Using enzymes as biological catalysts

Question 10

How do enzymes increase the reaction rate?

Answer 10

They lower the activation energy of the system which increases the proportion of particles that can react in the system

Question 11

By what magnitude do enzymes increase the rate of reaction by?

Answer 11

By up to a million times faster

Question 12

What kind of structure are most enzymes?

Answer 12

Proteins

Question 13

What is the region on the enzyme where the reactants bond to called?

Answer 13

The active site

Question 14

What is the model used to describe how an enzymes and substrate react?

Answer 14

Lock and key model (but more correctly the induced fit model FYI)

Question 15

What are the factors that affect enzyme activity? How is this a limiting factor?

Answer 15

• Temperature: too high=denaturing, too low=not enough Ea
• pH: anything outside optimum changes shape of active site, potentially denaturing
• Substrate concentration: enzymes become saturated an no longer catalyse for increasing concentrations
• Inhibitors (competitive and non-competitive): Block/change the active site preventing substrate bonding