Biochem Exam 2
The 'lock and key hypothesis' attempts to explain the mechanism of
enzyme specificity
Which of the following activates glycolysis
fuctose-2,6-bisphosphate
Enzymes are a special type of
protein
The molecule to which an enzyme joins is called its
substrate
What is the function of the glycolytic pathway
to break glucose down to pyruvate and other intermediates that can be used in the body
Glycolysis ends in the production of
two molecules of pyruvic acid
What is the difference between ~P and -P
~P is a high energy bond that can make ATP -P can't make ATP yet
Explain the importance of the primary structure of collagen
-Gly-X-Y structure, X usually Pro and Y usually Hyp. -Hydroxylated amino acids Hyp and Hyl are found exclusively in collagen
What cofactors are required by Kinase enzymes
-Mg2+ -ATP
There are six classes of enzymes in the classification scheme. Which of these classes are represented by glycolytic enzymes
-Oxido reductase -Transferase -Hydrolysis -Ligase -Isomerase -Lyase
What are three classes of reversible inhibitors (toxins) of enzyme activity
-competitive inhibitors -noncompetitive inhibitors -uncompetitive inhibitors
Identify three differences that an enzyme has as compared to an inorganic catalyst like Pt
-enzymes have an extremely high specificity towards their substrate and usually only catalyze one reaction -enzymes undergo conformational changes -enzyme activity is easily controlled
What are five mechanisms of enzyme reuglation employed by biological symptoms
-induction -allosteric regulation -partial proteolysis -covalent modification -control proteins
What molecules can serve as substrates from which glucose can be made
-lactic acid, pyruvate -Asp, Ala -Glycerol -Propinyl CoA
During the process of glycolysis, how many substrate level phosphorylation events occur for each molecule of glucose metabolized, and at what point in the glycolytic process do these occur?
1. glucoase to glucose-6-phosphate 3. fructose-6-phosphate to fructoase-1,6-bisphosphate 6. 1,3-bisphosphoglycerate to 3-phosphoglycerate 9. phosphoenolpyruvate to pyruvate
What is the glycolytic substrate for the enzyme enolase
2-PGA (2-phosphoglycerate)
Glycolysis requires an initial 'investment' of
2ATP
What is a pyranose
Carbohydrates with 5C and 1O
Where would i go about finding a molecule of G-6-Pase in the human body
Endoplasmic reticulum of liver and kidney
The fluoride ion has beneficial effects on bone and tooth development but in the glycolytic process it can be detrimental. Why?
F is a toxin to enolase (2-PGA to PEP) if enolase doesn't work, glycolysis wills top at 2PGA and it wont go further
What is responsible for the contraction in muscle fibers
Myosin heads grab and release the actin filament, pulling towards the M line. THis has to do with mysoin binding to ATP, and ATP hydrolysis and release. Ca2+ controlls troponin, which causes tropomyosin to either block or unblock the actin binding site
Which of these molecules are produced by glycolysis
NADH
What cofactors are required by the dehydrogenase enzyme of glycolysis and gluconeogenesis?
NADH and Pi
Metabolism of glucose via the glycolytic pathway results in the fomraiton of a net of two ATP molecules. If we had a died that supplied fructose instead of glucose how much ATP would we get?
Net would still be 2 ATP
What cofactors are required by carboxylase enzymes?
PC requiers Mg2+, ATP, and biotin
Which enzyme is the priary site of regulation in the glycolytic pathway and specifically how is this regulation achieved?
PFK is the primary site of regulation, achieved by allosteric regulation. ATP: inhibition AMP: activation Citrate: inhibition F-2,6-BP: activation H+ ions: inhibition G-6-P: inhibition
How is the activity of the enzyme Phosphoglycerate Mutase controlled
The reaction that PGM catalyzes is bidirectional, so this enzyme is controlled by equilibrium
How could you identify which class one of these inhibitors falls into
You can look at the [s]/V grapths -competative has two different starting points and cross on the Y axis -noncompetitive has the same starting point but two ending points -uncompetitive are two parallel lines
If NADH were not reoxidized to NAD, what affect would this have on glycolysis?
You would run out of NAD, and GAP wouldn't be converted to 1,3-BGP anymore after a certain point
What is the definition of a cofactor
a cofactor is an activator metal or coenzyme that needs to be present for a enzyme to work
Explain how chromatography can be used to separate two different proteins from a single solution
can be separated based on their molecular weight or size -will react with the liquid and will move a certain distance based on its affinity and size
Under some circumstances (futile cycle) fructose-1,6-bisphosphate may be hydrolyzed to form fructose-6-phosphate and phosphoric acid nearly as rapidly as it is formed. When this is happening, the major effect noticed would be
increased temperature in the tissue and organism.
At 25 C, the optimum reaction rate of a certain enzyme occurs at a pH of 7. A greater reaction rate could probably be attained by
increasing the temperature to 35C and keeping the pH 7
The source of blood glucose during the early stages of starvation is primarily
liver glycogen
Of the five mechanisms, which occurs most rapidly and which occurs most slowly
most rapid: allosteric slowest: induction
Coenzymes are best defined as
organic molecules which help in enzyme-catalyzed reactions by bonding with electrons
List three factors which influence the rate of enzyme activity and specificity explain their influence on this activity
pH: depends on the enzyme but away from optimum denatures temperature: higher temp increases rate until it causes the enzyme to denature substrate concentration: higher the [s], the greater the enzyme activation
We consume some fructose in our diet. The fructose can provide energy by
phosphorylation by fructokinase or hexokinase to form fructose-1-phosphate or fructose-6-phosphate and further oxidation through glycolysis