Exam 3 Review Flashcards
What type of reaction is an oxidoreductase reaction?
Oxidation-Reduction
What are the different types of cofactors?
Metals
Coenzymes
What type of reaction is an transferase reaction?
Group transfer
What type of reaction is a hydrolase reaction?
Hydrolysis reaction (transfer of functional groups to water)
What type of reaction is a lysase reaction?
Addition or removal of groups to form double bonds
What type of reaction is an isomerase reaction?
Isomerization (intramolecular group transfer)
What type of reaction is a ligase reaction?
Ligation of two substrates at the expense of ATP hydrolysis
What are the 6 types of enzyme reactions?
1) Oxidoreductase
2) Hydrolysis
3) Lyase
4) Isomerase
5) Transferase
6) Ligase
What is the Km?
The [substrate] that produces 1/2 Vmax
What is the Vmax?
Maximum velocity an enzyme is saturated with substrate
When [S] = Km…
Vo = Vmax/2
What is Vmax dependent on?
The amount of enzyme used
How do you determine the Km from a lineweaver-Burk Plot?
X-intercept = -1/Km
How do you determine the Vmax from a lineweaver-Burk Plot?
Y-intercept = 1/Vmax
What are Sequential Bisubstrate reactions?
All substrates bind to the enzyme before any product is released
What are Double-displacement (ping-pong) Bisubstrate reactions?
One of the products is released before a second substrate binds
What is allosteric inhibition?
Binding of an allosteric inhibitor, stabilizing the enzyme in its low-affinity form resulting in little or no activity
What is allosteric activation?
Binding of an allosteric activator, stabilizing the enzyme in its high-affinity form resulting in enzyme activity
What is the major role of Phosphatases?
Turn off signaling cascades activated by kinases
Describe serine proteases
Catalytic triad
Active site for protein cleavage
Serine 195 of chymotrypsin
What does a zymogen become an active protease/enzyme?
After cleavage
What zymogen/enzyme is found in the stomach?
Pepsinogen/Pepsin
What zymogen/enzymes are found in the pancreas?
Chymotrypsinogen/Chymotrypsin
Trypsinogen/Trypsin
Procarboxypeptidase/Carboxypeptidase
Proelastase/Elastase
What is the fuel source for the brain under non-starvation conditions?
Glucose
What is the only fuel source of RBC’s?
Glucose
Stage 1 of glycolysis consists of which enzyme reactions?
1) Phosphorylation
2) Isomerization
3) Phosphorylation
Stage 2 of glycolysis consists of which enzyme reactions?
Isomerization/Cleavage
How is phosphofructokinase regulated in the liver?
Activated by F-2,6-BP
Inhibited by citrate
How is glucokinase regulated in the liver?
Not inhibited by G-6-P
Is hexokinase in the liver?
No, glucokinase instead
How is pyruvate kinase regulated?
By allosteric effectors and covalent modification
What are the whole body needs and daily brain needs of glucose?
Whole body-160g
Brain-120g
Is gluconeogenesis a reversal of glycolysis?
NO
What are the 3 enzymes of irreversible reactions in glycolysis in the liver & skeletal muscle?
Glucokinase/Hexokinase
Phosphofructokinase
Pyruvate kinase
What are the “by-pass” steps used during gluconeogenesis to go around the irreversible glycolysis steps?
Pyruvate carboxylase/Phosphoenolpyruvate carboxykinase
Fructose-1,6-Bisphosphatase
Glucose-6-Phosphatase
What is pyruvate converted to in the first step of gluconeogenesis?
Oxaloacetate via Pyruvate carboxylase
What must be done for glucose to leave the liver?
Phosphate from glucose-6-phosphate must be cleaved off
What determines which pathway (glycolysis/gluconeogenesis) will be most active?
ATP/ADP ratio (energy charge)
What process traps glucose-1-phosphate in the cell?
Phosphorolysis
UTP binds with glucose-1-phosphate to form _______ in glycogen synthesis.
UDP-glucose
During the glycogen synthase step of glycogen synthesis, what type of glycosidic bonds are formed?
alpha 1,4
What does branching cause?
Increased solubility
Increased rate of synthesis and degradation
Which two hormones can’t cross the membrane?
Glucagon
Epinephrine
Where does the CAC take place?
Mitochondria
What is the E1 enzyme and what is its prosthetic group?
Pyruvate dehydrogenase component
TPP
What is the E2 enzyme and what is its prosthetic group?
Dihydrolipoyl transacetylase
Lipoamide
What is the E3 enzyme and what is its prosthetic group?
Dihydrolipoyl dehydrogenase
FAD
What is the only step of the CAC that directly yields a high energy compound?
Succinyl CoA —>Succinate
*Succinyl CoA synthetase
What other function can excess alpha-ketoglutarate lead to?
Synthesis of amino acids and purine bases
