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
What are enzyme inhibito
chemicals that selectively inhibit the action of specific enzymes
What are non competitive enzyme inhibitors
inhibitors bind to allosteric site & cause a change in the shape of the active site, preventing substrates from binding
Which type of inhibition can be overcome by increasing amount of substrate
competetive inhibition
What is the allosteric site
receptor site on enzyme, separate from active site
- when effectors (inhibitors of activators) bind, shape of enzyme changes, resulting in active or inactive enzyme
Optimal pH for pepsin and trypsin
2 and 8
Properties of Acids
- produce H+ when dissolved in water
- pH < 7
- Sour
- Can conduct electricity and cause skin burns
Properties of bases
produce OH- when dissolved in water
- Accepts or reacts with H+ ions
- pH > 7
- bitter
- soapy or slippery
- can conduct electricity and cause skin burns
How to calculate acidity
subtract pH level then multiple by 10^n
What do acids do in water
ionize and produce H+ ions
- donate protons (H+)
Strong acids ionize completely
Weak acids ionize partially
What do bases do in water
OH- dissociate to produce OH- ions, which accepts protons
- Strong bases dissociate completely
- Weak bases dissociate partially
What type of reaction occurs during neutralization
double displacement
What are the products of neutralization
H2O and ionic compound (salt)
acid + base -> salt + water
What are buffers
solutions that minimizes the change in pH when a base or acid is added to the solution
What are buffers made of
weak acid and a weak base
What will weak acids do in the presence of a strong base
Release H+ ions
What will weak bases do in the presence of a strong acid
Accept H+ ions
How do buffers work in the presence of strong acid
- strong acid will ionize completely and release many H+ ions
- pH of solution will decrease
- Weak base in buffer will act
- Weak base accepts H+ to form weak acid
- pH change will be minimized
How do buffers work in the presence of a strong base
- strong base will dissociate completly to release many OH- ions
- pH of solution will increase
- Weak acid in buffer will act
- H+ ions will be released to react with OH- to form water. upon release of H_, weak base will form
- pH change will be minimized
What is the main buffer system in blood
carbonic acid - bicarbonate buffer
Which organs help control blood pH
lungs, kidneys, heart
- remove CO2 helps increase pH
- remove HCO3- helps decrease pH
What are redox reactions
chem reactions that involve the transfer of 1 or more electrons from one reactant to another
- Loss of electrons = oxidation
- Gain of electrons = Reduction
Electrons move from where they are weakly held to where they are more strongly held
What is the substance that undergoes oxidation and loses and electron
Reducing agent
What is the substance that causes another substance to be oxidized
oxidizing agent
