1.3 Biochemical Reactions Flashcards
What is activation energy
energy needed to break existing bonds of reactants and to get reaction started so that new bonds can form
Exothermic reaction
Releases energy
Endothermic reaction
absorbs energy
How do chem reactions take place
reactant molecules must collide with enough force and in the correct geometric orientation so that bonds of reactant molecules break
- stable reactants require activation energy to reach the reactive state transition state in which old bonds begin to break and new bonds begin to form
If activation energy for a reaction is large, reaction will occur…
Slowly
The activation energy barrier prevents…
energy-rich molecules such as carbs, proteins, lipids, etc from undergoing SPONTANEOUS reactions and decompose to form less energy-rich simpler molecules
What are four ways to speed up chem reactions
heat, catalyst, increase concentration, increase SA by grinding
Which way do celle use to speed up chem reactions
catalysts (enzymes)
What are enzymes
biological catalysts that facilitate most chem reactions in cells
- protein molecules
- speed up chem reaction w/o being consumes
What are enzymes specific to:
- substrate (reactants upon which enzymes will act)
- type of reaction
What do enzymes do
lowers the activation energy barrier so that the transition state can be reached at moderate temperatures
How do enzymes speed up rate of reaction
- bring substrates together in correct orientation
- stretch and bend chem bonds of reactants that must be broken
- destabalize the substrate by adding or removing H+ ions or electrons to or from the substrate
- Provide the proper microenvironment (eg. correct pH)
Active Site
- Made up of a segment of aa w/in polypeptide chain folded into 3D structure to form a small groove or pocket on protein surface
- Very specific to the shape, size and charge of the substrate
- Temp and pH sensitive
- Where chem reactions take place!
Induced Fit Model
- Substrate enters active site
- Creates ENZYME-SUBSTRATE COMPLEX: weak bonds form between the enzyme and the substrate
- Enzyme changes shape to better accommodate substrate (induced fit)
- Reaction occurs
- Formation of products cause enzyme to alter back to original shape
- Products released
- Enzyme active site ready to receive next substrate
When enzyme-substrate complex has reached a maximum…
further increases in the concentration have no effect - all of the molecules are bound already
What is the optimal temp for typical human enzymes
37 deg celcius (body heat is 37)
What is the optimal temp for enzyme of thermophilic (heat-tolerant) bacteria
75 deg
What happens to enzymes if temp is raised
denaturation
- particles move faster, bump into each other, bonds are disrupted
What happens to enzymes if temp is lowered
reaction time is slower as particles move slower -> less chance of particles bumping into each other
What is optimal pH for pepsin
2
What is the optimal pH for tyrpsin (small intestine)
8
What happens if enzymes are not at optimal pH
denaturation b/c of lose/gain ions
What component is needed by some enzymes for catalytic activity
non protein components
what are competitive enzyme inhibitors
binds to active site, preventing substrates from binding
