midtem 1 quizzes Flashcards
Life is a result of chemical interactions of various elements in the environment. Reactions in the living system occur due to
Interaction of electrons in the outer orbit of the atom.
The most complex creation of nature, a human body is
a molecular assembly of mostly a few elements found in and on earth’s atmosphere.
b. If there is an increase in entropy during this reaction, in what form it is occurring?
A. Increase due to the loss of mass
reaction by measuring….?
concentration of product and substrate, voltage/reduction potential
The original source of energy on this planet is
Nuclear energy
universe or increases the entropy. Plants synthesize different compounds and create beautiful orders from disorder like flowers (e.g. Glucose from CO2, leaves, flowers, and fruits).
Disorder of energy is created in solar plasma
nourishment. Which of the following is true?
Disorder is created in the surroundings (via breathing out CO2)
Suppose you are running on the road for exercise. Write down the energy conversions from the source to the last form of energy in this process.
Chemical energy to kinetic energy to heat energy and sound energy
Which of the above are nucleophiles?
C -> carbonyl carbon -> carbon is electron
how and why?
Yes. Burning of wood is a reaction between O2 and a hydrocarbon. Because of O electronegativity and reactivity, it will be very desperate to react with the hydrocarbon. Spontaneous reactions are exergonic, meaning they produce/release lots of energy (in the form of heat).
Absolute temp T = 298 K
G0 = -RTln([C][D]/[A][B])
reaction with the concentration of different ingredients at equilibrium are A= 10 mM, B= 10 mM, D and C are 1M
G0 = -RTln([C][D]/[A][B])
R-CHO + NAD+ + PO4– = R-COO-PO4 + NADH + H+
Oxidizing agent = NAD+ -> grabs the electron from the NADH+
Calories (8360 KJoules). How much ATP (in grams) is hydrolyzed in one day by Dr. Pandey? Presume that free energy change in human physiological system is -50kJ/mole and molecular wt of ATP is approximately 500 dalton.
1M ATP = 500 g
If the reaction product in any reaction is resonance stabilized i.e. if it has different electronic configurations for the same compound, the reaction proceeds spontaneously in forward direction. Give a thermodynamic explanation for this phenomenon.
Resonance stabilization means more configurations. The more confirgurations means increase in entropy therefore spontaneous.
at equilibrium?
Zero because the reaction isn’t going backwards or forwards. Therefore concentration is not changing.
Explain entropy change in this reaction.
When water cools it releases heat into the air. Upon becoming heated, the air molecules will begin to move very fast. This is an overall increase of entropy. The air increased in entropy at the cost of a decrease in entropy in the water.
ATP in this condition?
G = G0 + RTln([prod][react])
converted to CO2.
In both scenarios we have a polymer of glucose. The difference is the type of energy released. In wood burning it is released as heat and light. In respiration heat is held in the chemical bonds of ATP. Another difference is that the body maintains costant temperature and pressure. Another difference is that O2 and the wood interact directly while in respiration the breakdown is stepwise.
Is the reaction in combustion engine favorable? If so, Why?
Yes. First, O is very electronegative so it is very desperate to react with the hydrocarbon, therefore the reaction will be spontaneous. Also in this type of combustion you go from liquid to gas, which is a more organized state to a less organized state.
Fe+++ is involved in many redox reactions, it has different standard reduction potential ranging from very positive to very negative. Explain why?
Iron is never free, it is always surrouned by a protein. Different amino acids surrounding the element means that different ions/electrons can interact with it therefore different reduction potentials.
standard temp and pressure) without measuring concentrations?
Yes by using standard reaction potential (voltage). This is for oxidation because of the movement of electrons.
Which one is favorable reaction?
Catabolism = breaking down. Anabolism = creating molecules. Catabolism has an increase in energy because as you break down a compound you release energy and increase disorder. Therefore catabolism is more favourable.
Special Question: Hunters who chased the rabbits for extended time and killed them for food, complained that the meet was sour. Why?
Under emergency conditions, the rabbits muscles will be undergoing lactic acid fermentation to significantly increase ATP production. Lactic acid fermentation product is Lactate which will build up in the muscles, lower the pH (make it more acidic) and create a sour taste.
Which reaction of glycolysis requires inorganic phosphate?
Inorganic phosphate is a substrate in the GAPDH rection, the most critical reaction in glycolysis. If you don’t add it then this reaction cannot go through.
g) CO2 during all the three pathways
A. 2
c. How many grams of net ATP and CO2 will be produced?
a. 342 g = 1 mol sucrose = 2 glucose = 4 alcohol. 4x 46=184 g alcohol. Alcohol relative density is 0.8. 184/0.8 = 230 mL -> 0.23 L 0.23/10 = 0.023 x 100 = 2.3 %
Name all the kinases involved in glycolysis
Hexokinase, phosphofructokinase-1, pyruvate kinase, phosphoglycerate kinase (4)
Name the substrates in forward direction of each kinase reaction.
Glucose, F6P, 2 phosphoglycerate, 1,3 bisphosphoglycerate
Name the reaction involving oxidation-reduction reaction in glycolysis.
glyceraldehyde 3 phosphate dehydrogenase
Which compound is reduced in the reaction in reaction
NAD+ is reduced into NADH
How many reactions of glycolysis involve phosphoryl group transfer? Provide the names of enzymes.
Six. 2 require ATP (hexokinase and phosphofructokinase). 4 have ATP involved (hexokinase, pfk, pyruvate kinase, phosphoglycerate kinase). GAPDH adds phosphate with no ATP, phosphoglycerate mutase also doesnt require ATP involved.
Which reaction in glycolysis is responsible for the net gain of ATP during this pathway?
glyceraldehyde 3 phosphate dehydrogenase (coupled with phosphoglycerate kinase)
Name the reactions in glycolysis involving phosphate group transfer without any involvement of ATP or ADP.
glyceraldehyde 3 phosphate dehydrogenase, phosphoglycerate mutase
Lactic acid, which lowers the pH causing fatigue. There is no ATP production during this step of the reaction. Why should this reaction be there?
To regenerate NAD+ in emergency situations so that we can allow the last 4 steps of glycolysis to persist at a fast pace and produce ATP.
reaction?
Nucleophilic attack on carbonyl carbon by the sulfur from sulfhydryl group on cysteine from active site of enzyme
Despite the low amount of ATP generated during glycolysis. Why this is the preferred pathway in muscle during fast movement?
Because it is substrate level phosphorylation and we can produce lots of ATP by catabolising glucose. Aerobic conditions cannot be accelerated at this rate. It is accelerated 100x
c. This reaction does not require ATP hydrolysis.
a) Phosphatase chops of phosphate and the enzyme becomes inactive
Why is glucose phosphorylated in the first step of glycolysis?
We do not want glucose to leave the cell. Glucose is phosphorylated by ATP to become gluose-6-phosphate, which now is charged. This charge does not allow it
positive. How does this reaction proceed in forward direction?
It is coupled to reaction 7 which is very exergonic, the product is immediately taken up by reaction 7
glycolysis?
phosphofructokinase
The substrate cycle is also called futile cycle, Why?
Occurs when two metabolic pathways run simultaneously in opposite directions
Is futile cycle really a futile exercise? If not what is the importance of this cycle.
It is used to control the flux of glycolysis.
iii. In both the lactate DH and alcohol dehydrogenase reaction during homolactic and alcoholic fermentation.
ii. NADH is being oxidized to NAD+
Yeast carry out alcoholic fermentation pathway to
Regenerate NAD+ for glycolysis reactions producing ATP under anaerobic
Why is glucose stored in the form of glycogen in muscle andliver as emergency stock?
Glycogen can be catabolized very fast into glucose and can be metabolized to make lots of ATP
What is the difference between glycogen and starch and what is the significance of this structure?
They are both polymers of glucose, they both have chains of 1-4 linkage and 1-6 linkage
What is the name of the cofactor in Glycogen phosphorylase reaction
Pyridoxal phosphate that is covalently linked to the enzyme
What kind of nucleophilic substitution takes place in glycogenphosphorylase reaction? Provide evidence for your answer
It is an SN1 reaction, meaning one step at a time. The leaving nucleophile is substituted with the attacking nucleophile. We know this because of the presence of a carbocation semi chair intermediate. Also there is no confirmation change between substrate and product. When gluconolactone, a similar product was added, then the reaction was inhibited.
Phosphorylated Glycogen phosphorylase (“a”, the active form)is independent of allosteric effectors. Explain need for such regulation
It is activated via phosphorylation of its two dimer parts. It is phosphorylated by phosphorylase kinase. This happens under emergency conditions where we need to produce lots of glucose 6 phosphate and ATP. These emergency conditions are triggered by epinephrine and glucagon. Even in the presence of ATP and glucose 6 phosphate it will still stay active. It will also ignore AMP.
Hormonal control of glycogen breakdown is necessary in muscle tissue to quickly generate energy in stress. What is the role of similar control in liver tissue?
The liver does not need to generate ATP to do anything. The liver makes sure there is sufficient glucose in the blood. The liver will break down glucose and secrete it into the blood. The emergency that the liver can work on but muscles can’t is the situation in which a person has not eaten for a long time and blood glucose levels are dropping. This is called a dietary emergency.
What is the mechanism of Phosphoglucose mutase reaction?
Enzyme is phosphorylated. It lends its phosphate to the 6th carbon, then replenishes the phosphate with the one on the 1st carbon
Why is Glucose 6 Phosphatase dephosphorelated (removal of phosphate) in liver?
Glucose 6 phosphate is charged and cannot be secreted into the blood. Therefore we dephosphorylate it to neutral glucose so that it can be secreted into the blood to maintain blood glucose levels.
What are the two enzymatic activities og debranching enzyme?
First one is glycosidic transferase. Second is a 1,6 - glycosidase.
