Enzymes pt. 3 (Quiz 1) Flashcards
- In the Enzyme and substrate concentrations, the rate of reaction ________ as
substrate concentration _________ (at constant enzyme concentration).
note: same answer
- _______ activity occurs when the
enzyme is saturated.
- increases
- Maximum
The relationship between reaction rate and substrate concentration is _________, and ___________ (levels off) when the enzyme is saturated
exponential
asymptotes
The Effect of [E] on velocity:
The _______of an enzyme-catalyzed reaction is always proportionate to the concentration of enzyme
This property of enzyme is made use in determining the ________ for the diagnosis of diseases.
initial rate
serum enzyme
In the Enzyme Concentration and Reaction Rate:
- The rate of reaction ______as enzyme concentration _______(at constant substrate concentration)
- At ____________, more enzymes are available to catalyze the reaction (more reactions at once)
- There is a _________ relationship between reaction rate and enzyme concentration (at constant substrate concentration)
- increases
- higher enzyme concentrations
- linear
The effect of temperature on velocity:
- Enzymes are most active at an __________ (usually 37°C in humans)
- Show little activity at _______ temperatures.
- Lose activity at ________ temperatures as __________ occurs.
- Optimum Temperature
- low
- high, denaturation
Effects of Temperature:
__________ of reaction increases until an Optimum temperature is reached
Speed
Effects of Temperature::
- ____________ is the temperature at which the enzyme works best
- After this point the rate of reaction decreases until there is _________
- At this point enzyme is said to be _________ - active site destroyed
- Optimum temperature
- no reaction
- DENATURED
A reaction rate will generally increase with increasing Temperature due to ____________ in the system until a maximal velocity is reached.
Above this maximum, the kinetic energy of the system exceeds the energy barrier for breaking weak
H-bonds and hydrophobic interactions, thus leading to _____________ of the enzyme and a decrease in reaction rate.
increased kinetic energy
unfolding and denaturation
Increasing the temperature denature (destroys) the shape of the __________.
protein
Effect on rates of enzyme activity
o At __________ greatest number of collisions between enzyme & substrate
o ________________
❖ 35°-40°C (body temp = 37°C)
o Raise temperature (boiling)
❖ denature protein = ?______________
o Lower temperature T
❖ molecules move ________
❖ fewer _________ between enzyme & substrate
Optimum temperature
human enzymes
denature protein = unfold = lose shape
slower
collision
In the effect of temperature: (See image from notes)
Q10 (the temperature coefficient) = the increase in reaction rate with a 10°C rise in temperature.
- For chemical reactions the Q10 = 2 to 3 (the rate of the reaction ________ with every 10°C rise in temperature
- ___________ reactions follow this rule as they are chemical reactions
- The optimum temperature for an enzyme controlled reaction will be a balance between the ___________.
- doubles or triples
- Enzyme-controlled
- Q10 and denaturation
- For most enzymes (outside the human body) the optimum temperature is about _______ . Many are a lot lower, cold water fish will die at this temperature because their enzymes denature
- A few bacteria have enzymes that can withstand very high temperatures up to ________
- Most enzymes however are fully denatured at _____
- 30°C
- 100°C
- 70°C
Effect of pH value on velocity:
- Each enzyme has an optimal pH or pH range (where the enzyme has __________ activity).
- Requirements for the catalytic groups in the active site in appropriate _______ is a common reason for this phenomenon.
- maximal
- ionization state
The pH optimum for different enzymes. Most enzyme’s is in neutral pH ranging ________
6-8
Variations in pH can affect a particular enzyme in many ways, especially if __________ side chains are involved in binding of the substrate and/or catalysis.
ionizable amino acid
________ can also lead to denaturation of an enzyme if the ionization state of amino acid(s) critical to correct folding are altered.
Extremes of pH
Extreme pH levels will produce ________
The structure of the enzyme is ______
The _______ is distorted and the substrate molecules will no longer fit in it
denaturation
changed
active site
At pH values slightly different-from the enzyme’s optimum value, small changes in the charges of the enzyme and it’s ___________will occur
This change in ionization will affect the ________ of the substrate with the active site
substrate molecules
binding
Effect on rates of enzyme activity
- changes in pH changes protein _______
- most human enzymes = ______(pH level)
o depends on where in body
o pepsin (________) = pH ___
o trypsin (________) = pH ___
shape
pH 6-8
stomach, pH 3
small intestines, pH 8
In pH and Enzyme Activity:
- Enzymes are most active at __________
- Amino acids with acidic or basic side-chains have the proper charges when the _______
Note: first two ques. have the same answer.
- Activity is lost at ______or______ as tertiary structure is disrupted
optimum pH
pH is optimum
low or high pH
Most enzymes of the body have an optimum pH of about ____. However, in certain organs, enzymes operate at lower and higher optimum pH values
7.4
___________ are molecules that bind to enzymes and increase their activity.
Enzyme activators
Enzyme activators:
i. Inorganic ions
o __________, such as Na+, K+, Mg2+, Ca2+, Cu2+, Zn2+, Fe2+ et al
o ________: such as Cl-, Br-, I-, CN- et al
ii. Organic
o _______, such as Cys, GSH
iii. Proteins
Metal ions
Anions
Reducing agents
Any molecule which acts directly on an enzyme to lower its catalytic rate (not denaturation)
Inhibitor
Some _________ are normal body metabolites.
Other may be foreign substances, such as ________
enzyme inhibitors
drugs or toxins
Other means to affect or Regulate ENZYME ACTIVITY (5)
- Allosteric binding sites
- By Covalent Modification
- Induction and repression of enzyme synthesis
- Zymogen Cleavage
- Location within the cell
_________ enzymes are regulated by molecules called _______ (modifiers) that binds nonconvalently at a site other than the active site.
Allosteric
effectors
Many enzymes are regulated by ____________ , most frequently by the addition or removal of ‘phosphate’ group to serine, threonine or tyrosine residue of the enzyme by _______. (enzyme)
covalent modification
kinases (a.k.a phosphorylation)
In________, cells can also regulate the amount of enzymes present by altering the rate of enzyme synthesis
Induction and repression of enzyme synthesis
Some enzyme are synthesized as Inactive precursor, called __________, that are activated by proteolysis (e.g., digestive enzyme, pepsinogen is inactive and cleaved to pepsin which is active chymotrypsin)
zymogens
Many enzymes are ________ in specific organelles within the cell. This, ________ helps in the regulation of the metabolic pathway.
localized
compartmentation
