biochem2 Flashcards
(117 cards)
1
Q
what is bioenergetics?
A
Thermodynamics of a biological system
2
Q
Three students are reviewing a chart in their biochemistry text showing that many of the individual steps of glycolysis have a positive G’ value. Which student has the correct explanations for why glycolysis still occurs readily in living systems: Student A) Enzymes are the solution! Enzymes drastically lower the free energy change to be more negative. Student B) Food energy is the solution! Many biochemical reactions are unfavorable and that is why we must eat—to provide external energy to drive these reactions and maintain disequilibrium. Student C) Reaction coupling is the solution! While some reactions are unfavorable, they are coupled to reactions that are favorable.
A
Student C
Several steps in glycolysis have positive ΔG’s, but the pathway still occurs spontaneously in cells.
Student C is correct, reaction coupling will drive the entire pathway forward. Some steps in glycolysis have positive ΔG’s, but other steps have very negative ΔG’s. Those steps require the products of previous steps. Because the reactions are linked by the product of one reaction providing the substrates of the following reactions, the very negative ΔG’s will pull the pathway forward, even though the positive ΔG’s are earlier in the pathway than the very negative ΔG’s.
3
Q
a living system require __ and ___ delta S due to all macromolecules and systems being highly ordered compared to their precursors.
A
large negative
4
Q
What is dynamic steady state / homeostasis?
A
describes the ability of living things to maintain a constant steady internal environment that is NOT in equilibrium with its surrounding.
5
Q
What is the difference between equilibrium and steady state?
A
Equilibrium is a dynamic state existing at the LOWEST possible entropy and energy for that system.
Steady state involves a constant INVESTMENT (HIGHER ENERGY) of energy for living systems to maintain a steady that is far from equilibrium.
6
Q
is the human body an open or close system?
A
open as a whole but closed system on a cellular and molecular level.
7
Q
What is delta G?
A
free energy change at some present, non standard set of conditions.
8
Q
what is delta g knot ? DeltaG*
A
free energy change at standard contains of 25C, 1atm, and [1M] of all species.
9
Q
what is delta G knot prime? deltaG*’
A
Free energy change at standard physiological conditions, pH= 7
10
Q
If delta G is positive, does the equation go to the right or to the left?
A
to the left
11
Q
If delta G is negative, does the equation go to the right or to the left?
A
to the right
12
Q
In the equation: deltaG=deltaG’+RTlnQ
what is delta G?
what is deltaG’
A
R= universal gas law constant t = temperature q= reaction quotient deltaG'= fixed unchangeable deltaG= is variable and can be measured anywhere at any time during a reaction.
13
Q
Students frequently hold misconceptions about G and G’. Check yourself with the following: T/F?
a) For Reaction X, G = -30.78 kJ. For Reaction Y, G = 22.5 kJ. It can be concluded that Reaction Y is closer to its equilibrium than is Reaction X,
b) At equilibrium, G’ = 0,
c) At equilibrium G = 0
d) For a given reaction at a given temperature, there are an infinite number of different G’ values associated with different ratios of products to reactants,
e) For a given reaction at a given temperature, there are an infinite number of different G values associated with different ratios of products to reactants,
f) G*’ represents the free energy change for a complete conversion of all reactants to products.
A
a) true 25 is closer to 0 than 30.
b) false
At equilibrium, because deltaG’ = -RTlnKeq and at equilibrium, ΔG = 0
c) true
d) false
e) true
f) false
14
Q
what are parameters of an endergonic reaction?
A
delta G is positive = non spontaneous
15
Q
what are parameter of an exergonic reaction?
A
deltaG is negative= spontaneous
16
Q
T/F?
a) If Keq =1,G*=0
b) If Keq =1,G=0
c) If Keq =Q,G=0
d) If Keq =Q, G=0
e) If Q=1,G=0
f) If Keq =1,G=G
g) If Q=1,G=G
h) If Keq >1, G must be negative,
i) If Keq > 1, G must be negative.
A
looking at delta G=deltaG’+RTlnQ and deltaG’ = -RTlnKeq
a) true
b) false
c) true - If Keq = Q, the reaction is at equilibrium, and ΔG = 0.
d) false
e) false
f) false
g) true- ΔG = ΔG° + RTln(Q). Since Q = 1 and Ln(1) = 0, ΔG = ΔG°.
h) true- ΔG° = -RTlnKeq
i) false
17
Q
1) The post-translational folding of the enzyme ribonuclease-A is associated with a large, negative S for the unfolded-to-folded transition. Ribonuclease-A folds spontaneously because the:
A) sum of the heats of formation of all folding interactions in the native conformation is large and negative.
B) sum of the heats of formation of all folding interactions in the unfolded conformation is large and negative.
C) change in entropy for the unfolded-to-folded transition is large and positive.
D) change in entropy for the unfolded-to-folded transition is small and positive.
A
a
18
Q
what is ATP?
A
primary energy currency in human body
19
Q
Delta G*’ for ATP HYDROLYSIS has to be less or more than 0?
A
a lot less than 0
20
Q
when you lose phosphate group and go from ATP –> ADP –> AMP, is the transition end or exergonic? which is the highest energy molecule?
A
exergonic
cAMP is higher energy molecule than ATP.
21
Q
What is the AMP-> cAMP transition; endo or exergonic?
A
endergonic which is why cAMP is a higher energy molecule than ATP.
22
Q
What is substrate level phosphorylation?
A
process by which ATP is formed from ADP. Process must be bound to an exergonic reaction.
23
Q
where does substrate level phosphorylation occur?
A
primarily in cytosol as part of glycolysis but also in matrix of mitochondria where GTP is formed during Citric acid cycle
24
Q
what is oxidative phosphorylation?
A
formation of ATP out of ADP and free organic phosphate (Pi) by harnessing energy of proton gradient across inner mitochondrial membrane.
Proton gradient causes by oxidation of NADH and FADH2.
ex: ATP formed by the ATP synthase complex in the mitochondria
25
where does oxidative phosphorylation occur?
exclusively in mitochondrial matrix.
26
What is equation for hydrolysis of ATP?
ATP + H2O --> ADP + Pi + energy
then couple to another equation
27
What is equation for Phosphoryl group transfer?
ATP ADP + energy, but the phosphate is transferred onto another molecule, rather than being releases as Pi.
28
What is phosphorylation using ATP? what is its importance in the body?
phosphoryl group transfer
Major human body regulation mechanism where enzymes, proteins and signaling molecules are turned on/ off by phosphorylation.
ATP acts as donor of phosphate group.
29
In the reaction
GADP + NAD+ + Pi --> 1,3 BPG + NADH
which molecules are reduced? which are oxidized?
In the reaction, GADP is the reduced form, NAD+ is the oxidized form 1,3 BPG is the oxidized form, and NADH is the reduced form. Thus NAD+ is being reduced (it is an oxidizing agent) and GAPD is being oxidized (it is a reducing agent).
30
When you see NADH/NAD+, NADPH/NADP+ FADH2/FAD, FMNH2/FMN, semiquinone (an FMNH radical), ubiquinone, or cytochrome; think about what type of reactions?
REDOX
31
What is aerobic versus anaerobic respiration?
Respiration is a process in which an in organic compound serves as the ultimate electron acceptor in order to generate ATP.
Aerobic respiration uses oxygen as the final electron acceptor, while anaerobic respiration uses a molecule other than oxygen. For question purposes, aerobic respiration involves all the reactions involved in the citric acid cycle and electron transport.
Anaerobic respiration will typically refer to fermentation, using glycolysis in the absence of oxygen, or the lactic acid cycle in muscles. Humans use aerobic respiration to generate the vast majority of our ATP. However, we use anaerobic respiration in our muscles during exercise that results in a buildup of lactic acid. Many bacteria and yeast use anaerobic respiration, including during fermentation.
32
What is the difference between an obligate aerobe and a facultative aerobe? Between an obligate and a facultative anaerobe? Which one are you?
The term “obligate” implies that there is no other option, so obligate aerobes must use aerobic respiration and cannot survive without oxygen, while obligate anaerobes must use anaerobic respiration and cannot survive in the presence of oxygen. “Facultative” implies that the organism will use whichever respiration is available. So if oxygen is present, the organism will use aerobic respiration, and if oxygen is absent, the organism will use anaerobic respiration. Facultative anaerobes prefer anaerobic conditions while facultative aerobes prefer aerobic.
12.
33
What does glycogen phosphorylase do?
removes glucose residues from reducing ends of glycogen polymers --> glucose-1P
34
what does phosphoglucomutase do?
converts Glucose 1P --> Glucose 6P
35
in which metabolism are glycogen phosphorylase and phosphoglucomutase found?
Glycogen metabolism
36
what is metabolized in the muscle and kidney in fructose metabolism?
Hexokinase converts Fructose --. Fructose 6P.
37
what is the point of galactose metabolism ?
Galactose convertes to Glucose 1P through multiple steps that involve UDP as the coenzyme.
38
What is the role of phosphoglucomutase in galactose metabolism?
Convert Glucose 1P to Glucose 6P (which then goes to 2nd step of Glycolysis)
39
Fructose metabolism in the liver, what three things are converted to what by what?
1) Fructokinase converts Fructose to Fructose 1P
2) Fructose 1= phosphate aldolase converts Fructose 1P to Glyceraldehyde 3P and DHA-P
3) Triose phosphate isomerase converts DHA-P to Glyceraldehyde 3P (GA-3P is funneled to 5th step of glycolysis).
40
When is fermentation used by animals?
when there's oxygen debt (like prolonged exercise) and in erythrocytes.
41
What is ethanol fermentation? what's unique about it?
primarily used in yeast and in a few bacteria. Ethanol is produced and is the final electron acceptor.
IMPORTANT: carbon skeleton changes from pyruvate 3C to ethanol 2C and CO2
42
what is lactic acid fermentation?
lactate is produced and is the final electron acceptor.
43
what is the importance of fermentation?
regenerates NAD+ so that glycolysis can continue
44
what is gluconeogenesis/
reversal of glycolysis to produce glucose from pyruvate.
45
when are you likely to see gluconeognesis?
In Liver = fasting= need to increase blood sugar.
46
what are the four enzymes in glycolysis that are being replaced in gluconeogensis and by what?
Hexokinase/glucokinase --> glucose-6-phosphatase,
phosphofructokinase --> fructose-1,6-bisphosphatase,
pyruvate kinase enzymes --> PEP carboxykinase/pyruvate carboxylase.
those enzymes are all irreversible reactions and replaced phosphorylation reaction.
47
What are the two important products of the Pentose phosphate pathway?
1) NADPH synthesis
20 Ribose 5 phosphate R5-P
48
what is the importance of NADPH?
important reducing agent used in synthesis of fatty acids and steroids + necessary for production of glutathione (most important antioxidant)
49
What is the importance of R5-P?
used to synthesize nucleotides. Oxygen bearing ring of all nucleotides, inducing deoxyribonucleic acid.
5 =5' carbon.
50
What happens during the oxidative phase of PPP?
* Glucose 6P --> 6phosphogluconate --> Ribulose 5P
* NADP+ to NADPH NADPH is used to: 1) reduce glutathione disulfide (GSSH) to glutathione (2GSH) and 2) act as a cofactor for reductive biosynthesis.
51
What happens during the non oxidative phase of PPP? what are two important things to know about the conversion happening?
Ribulose 5 phosphate --> R5P (funneled to nucleotide synthesis) Sugar pool Glucose 6 phosphate
IMPORTANT: Conversion into the SUGAR POOL from Ribulose-5-Phosphate, interconversions between sugars within the pool, and conversion to Glucose-6-P are all catalyzed by either Transketolase or Transaldolase. 2) All of the reactions into, out of, and inside of the pool are reversible.
52
How many NADPH are produced per glucose-6-P molecule by the PPP? How many glutathione molecules are produced per glucose-6-P?
For each glucose 6-phosphate, two NADPH molecules are generated.
The pentose phosphate pathway does not directly generate glutathione molecules. However, the NADPH generated in the PPP can be used to reduce the oxidized form of glutathione to protect the cell from reactive oxygen species. To regenerate glutathione, the reaction is 1 glutathione disulfide + NADPH → 2 glutathione + NADP+. This means that for each glucose 6-phosphate, four glutathiones are generated, because two NADPHs are generated.
53
What is the PDH complex?
complex of three enzymes that converts pyruvate into acetyl-CoA by a process called pyruvate decarboxylation.
54
Where does pyruvatee go from glycolysis?
PDH complex --> acetyl CoA ( to TCA cycle)
Lactate dehydrogenase --> Lactate
Pyruvate carboxylase --> oxaloacetate (to TCA cycle)
55
2) Glycolysis can be replicated in vitro. If fructose-6-phosphate, ATP, and the enzyme phosphofructokinase are added to a saline solution in a beaker, the addition of a small amount of which molecule will NOT increase the rate of change in the concentration of fructose-1,6-bisphosphate in the beaker? (Assume fructose-6-phosphate is not in excess.)
A) AMP
B) ATP
C) phosphofructokinase D) fructose-6-phosphate
B-
Adding AMP is a signal to glycolysis that energy reserves are low and therefore AMP acts as an allosteric activator for the key glycolytic enzymes. Answer C is false because this is the enzyme catalyzing the reaction; adding more of it will speed up the reaction. Answer D is false because this is the substrate in this enzyme-catalyzed reaction and therefore adding more of it will increase reaction rate. Answer B is correct. ATP is an allosteric inhibitor of this step of glycolysis, but one does not need to know that specifically. High-energy molecules provide negative feedback to metabolic processes that create ATP, such as glycolysis.
56
What are the steps in glycolysis?
1) glucose --> glucose 6 Phosphate with hexokinase (favorable)
2) glucose6phosphate --> fructose 6 phosphate wth phosphoglucose isomerase (unfavorable)
3) fructose6phosphate --> fructose 1,6 biphosphate with phosphofructokinase (unfavorable)
4) fructose 1,6 biphosphate --> glyceraldehyde 3 phosphate and DAP, using fructose biphosphate aldolase (unfavorable)
5) isomerase interconversion between glyceraldehyde 3 phosphate and DAP
6) Glyceraldehyde 3 phospahte --> 1,3 biphosphoglycerate using glyceraldehyde phosphate dehydrogenase + 2 NADH out (unfavorable)
7) 1,3 biphosphoglycerate --> 3 phosphoglycerate using phosphoglycerate + 2 ATP (favorable)
8) 3 phosphoglycerate --> 2 phosphoglycerate using phopshoglycerate (unfavorable)
9) 2 phosphoglycerate --> phosphoenol- pyruvate using enolase (unfavorable)
10) phosphoenol- pyruvate --> pyruvate using pyruvate kinase + 2 ATP (favorable)
57
what are the steps in TCA/ Krebs/ citric acid cycle?
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1) Acetyl-CoA --> citrate using claisen condensation / citrate synthase
2) Citrate --> cis Aconite --> Isocitrate through dehydration/ rehydration with aconitase
3) Isocitrate --> alpha-Ketoglutarate using isocitrate dehydorgenase/ oxidative decarboxylation + NADH
4) alpha-Ketoglutarate --> Succinyl CoA using Alpha ketoglutarate dehydrogenase complex./ oxidative decarboxylation + NADH
5) Succinyl CoA --> Succinate using succinyl CoA synthetase/ substrate level phosphorylation + GTP
6) Succinate --> Fumarate using succinate dehydrogenase + FADH2
7) Fumarate --> Malate using fumarase
8) Malate --> Oxaloacetate using malate dehydrogenase + malate dehydrogenase
9) Oxaloacetate --> Acetyl CoA using citrate synthase.
58
In the ETC, what is the approximate number of protons pumped by each complex? What is the approximate number of protons pumped by each NADH molecule? By each FADH2 molecule? How many protons are associated with the generation of one ATP at the ATP Synthase molecule?
Complex I pumps 4 protons. Complex II pumps 0 protons (because it does not traverse the membrane, it can’t pump protons). Complex III pumps 4 protons. Complex IV pumps 2 protons. Utilizing electrons from an NADH molecule will result in 10 protons pumped because the electrons go through Complex I, III, and IV (So 4 + 4 + 2). Utilizing electrons from FADH2 will result in 6 protons pumped because the electrons go through Complex II, III, and IV (so 0 + 4 + 2). To generate one ATP molecule, 3 protons are needed. This means that every NADH generated will result in 3 ATPs, and every FADH2 will generate 2 ATPs.
59
what is the overall net reaction of glycolysis?
glucose+2NAD+ +2Pi +2ADP2pyruvate+2ATP+2NADH+2H+
60
what is the reaction of TCA?
pyruvate + 4 NAD+ + FAD + GDP + Pi + 2 H20 3 CO2 + 4NADH + 4H+ + GTP + FADH2
61
what is the reaction of TCA?
pyruvate + 4 NAD+ + FAD + GDP + Pi + 2 H20 3 CO2 + 4NADH + 4H+ + GTP + FADH2
62
what are biochemical shuttles used for?
transport molecules across impermeable membranes.
63
What is the malate aspartate shuttle a solution to?
Problem: NADH produced form glycoslyis cannot pass through the inner mitochondrial membrane and enter the ETC.
Solution: NADH donates two electrons to oxaloacetate, which converts it to malate. Malate passes the matrix via the malt alpha ketoglutarate anti porter.
Once inside the matrix, malate is converted back into OAA, which regenerates NADH. OAA is then pumped back out in the form of aspartate through the glutamate aspartate shuttle.
64
What is the glycerol 3 phosphate shuttle a solution to?
Problem: NADH produced form glycoslyis cannot pass through the inner mitochondrial membrane and enter the ETC.
Solution: NADH donates two electrons to dihydroxyacetone phosphate (DHAP) to form Glycerold 3 phosphate (G3P).
G3P is converted back into DHAP by mitochondrial G3P dehydrogenase, an enzyme bound to the cytosolic surface of the inner mitochondrial membrane. The enzyme passes the electron to FAD to form FADH2.
65
What is the carnitite shuttle a solution to?
Problem: Fatty acids cannot pass through th winner mitochondrial membrane, where they need to be in order to go through B- oxidation.
66
What is the carnitite shuttle a solution to?
Problem: Fatty acids cannot pass through the inner mitochondrial membrane, where they need to be in order to go through B- oxidation.
Solution: The enzyme carnotite acyltransferase attaches the fatty acyl group from an acyl CoA to the hydroxyl group of carnitine. A translocate enzyme on th einne mitochondrial membrane moves one acyl carnitine into the matrix and one carnitine back out.
67
What is the citrate- Acetyl CoA shuttle (tricarboxylate transport system) a solution for?
Problem: During periods of energy abundance, acetyl-CoA groups in the mitochondria are redirected from the citric acid cycle to fatty acid synthesis, which occurs in the cytosol and Acetyl- CoA cannot pass through the inner mitochondrial membrane.
Solution: Acetyl- CoA is combined with OAA to form citrate. Citrate is bale to pass through the membrane and is then converted back to OAA and Acetyl- CoA in the cytosol.
68
Where does oxidative phosphorylation occur?
ATP synthase in ETC.
| phosphorylation of ADP using energy form the gradient and oxygen as the final electron acceptor.
69
what is chemiosmotic coupling?
direct coupling of the energy inherent in the electrochemical gradient across the inner mitochondrial membrane to the phosphorylation of ADP (to form ATP).
70
What does it mean when a drug "uncouples" the ETC from oxidative phosphorylation?
This means the gradient is no longer directly driving ATP production at the ATP synthase. For example, this could be because a drug inserted proton channels into the inner mitochondrial membrane. The ETC would continue to pump protons, but because protons have an alternate route back into the matrix, the two processes would no longer be directly or fully “coupled.”
71
What is the proton motive force?
driving force of the electrochemical gradient established by the electron transport chain that is harvested by ATP synthase to produce ATP. The energy released as protons move down their concentration gradient AND down their electrical gradient, toward the mitochondrial matrix is used by ATP synthase to add a free organic phosphate to ADP, creating ATP.
72
what are 3 allosteric control?
1) metabolic regulation with downstream product inhibiting an upstream enzyme.
ex: first few product molecules synthesized are very unlikely to immediately interact with the enzyme—meaning it won’t be shut off too early. However, as that product builds up, the upstream enzyme will begin to interact with that product frequently, and the enzyme will be inhibited.
2) the eventual target molecule or logical goal of the process, is often a major inhibitor that down regulates upstream production.
ex: ATP acts as an allosteric inhibitor of Phosphofructokinase-1 (PFK-1), the enzyme for the rate-limiting step of glycolysis.
3) most likely step to be regulated in a metabolic pathway is the first committed step/ first non reversible step.
ex: the first non-reversible step in glycolysis is hexokinase.
73
what is an allosteric enzyme?
Enzymes that change conformation and/or affinity for their substrate upon binding of an allosteric regulator molecule.
74
what is an allosteric regulation?
The general term used to refer to the process of allosteric regulators binding to enzymes to either upregulate or downregulate their activity. Allosteric effects almost always result from conformational changes. Allosteric regulator molecules always binds AWAY FROM THE ACTIVE SITE.
75
What are (6) the metabolism hormones?
insulin, glucagon, glucocorticoids, catecholamines, T3 and T4.
76
what is the effect of glucocorticoids?
example of cortisol
| produce din anterior pituitary, glucagon like effect on metabolism and reduce inflammation.
77
what is the effect of catecholamines?
example of dopamine, epinephrine, norepinephrine.
dopamine is CNS neurotransmitter while epinephrine/ adrenaline and norepinephrine are metabolic hormones.
they cause a "glucagon like" effect that is rapid mobilization of energy stores necessary for the fight or flight response.
78
What are T3 and T4?
these thyroid hormones increase basal metabolic rate; both are secretes by the thyroid in response to TSH from the anterior pituitary.
79
Where does beta oxidation of fatty acids occur?
mitochondrial matrix, with the exception of extra long faaty acids which first enter the peroxisome to be catabolized into smaller pieces
80
how do fatty acids cross the inner mitochondrial membrane to reach the matrix?
carnitine shuttle
81
what does glycolysis require ?
2 ATP, 2NAD+and 4 ADP to produce 4 ATP for net production of 2ATP.
82
what does beta oxidation require per 2carbon cycle?
1 FAD, 1 H2O, 1 NAD+ and 1 CoA-SH
(Note: An activated fatty acid will already have an –S-CoA group on the carbonyl end of the chain. The CoA-SH required here is added to the 2-carbon acetyl group that is the product of the oxidation, creating an Acetyl-CoA rather than acetic acid)
83
What is the net result of Beta oxidation per 2 carbon cycle?
1 FADH2 (2 ATP), 1 NADH (3 ATP) and 1 Acetyl-CoA (12 ATP).
84
How many cycles of β-oxidation will be required to completely oxidize a 14-carbon fatty acid? How many cycles will be required to oxidize a 17-carbon fatty acid?
6 cycles- for even number divide by 2 and subtract 1.
7 cycles- for odd numbers, subtract 1 first then divide by 2 then subtract 1 again.
85
what happens to odd # of carbons?
Fatty acids with an odd number of carbons will result in a 3-carbon residue, propionyl-CoA. This reacts via multiple steps to form succinyl-CoA, which is then fed back into the Krebs Cycle. basically there's leftover carbon thats put back in krebs cycle..
86
What type of double bonds is seen in beta oxidation?
double bond in the 2-3 position.
87
What double bond prevent beta oxidation from occurring ? what enzyme fixes it and how?
If a double bond is in another position (e.g., 3-4) -oxidation cannot proceed. However, the enzyme, Enoyl-CoA isomerase catalyzes the movement of double bonds to the 2-3 position. Oxidation can again proceed.
Same thing can happen for conjugated double bond.
88
what are three examples of ketone bodies?
Acetone (no energyvalue),
| Acetoacetate (energy), and 3-Hydroxybutyrate (energy)
89
when are those ketone bodies formed/ seen?
formed by liver dragon fasting periods as byproduct of increase fatty acids metabolism and used as energy by heart and brain.
90
what happens when you fast for too long?
too much ketone bodies = ketoacidosis = excess acidity of the blood.
91
What disease can cause ketoacidosis?
diabetes can cause ketoacidosis because lack of insulin = can't break down carbs and nutrients so liver switches over to fatty acid metabolism producing ketone bodies.
92
Where are lipids metabolized/ synthesized/ and modified?
ipids are metabolized for energy in the mitochondria, synthesized in the cytosol (mostly hepatocytes), and modified at the smooth ER (SER).
93
what happens to most amino acids?
can be broken down into either pyruvate or acetyl-CoA and fed into the Citric Acid Cycle. The remaining amino acids can be transformed into various other Citric Acid Cycle intermediates (often alpha-ketoglutarate, Step and enter into the cycle at the appropriate point. Notice that we have now seen that the pyruvate/acetyl-CoA fed into the Krebs cycle can be derived from carbohydrates, fats, or proteins.
94
What is transamination?
a key step in protein metabolism for energy- the exchange of an amine group on on molecule for a carboxyl group on another. For example:
transamination of Glu forms alpha-ketoglutarate, an intermediate in the Citric Acid Cycle.
95
what is a ketogenic amino acid? what happens to it and what are two examples?
A ketogenic amino acid is degraded into acetyl CoA or acetoacetyl CoA (ketone bodies) through ketogenesis. The carbons of ketogenic amino acids are ultimately converted to CO2 in the citric acid cycle (because acetyl CoA carbons are converted to CO2). Leucine and lysine are both ketogenic.
96
What is a glycogenic amino acid? what happens to it and what are two examples?
Glucogenic amino acids can be converted to glucose through gluconeogenesis. They are converted first to alpha keto acids and then to glucose in the liver.
all amino acids are glycogenic except for: leucine, lysine and those that can be both keto and glycogenic (isoleucine, phenylalanine, tryptophan, tyrosine, and threonine).
97
what are the 5 amid acids that can be both kept and glycogenic.
isoleucine, phenylalanine, tryptophan, tyrosine, and threonine
98
Differentiate between ketogenesis and ketolysis. Where does each occur? How are they linked?
Ketogenesis is the process by which ketone bodies are produced through the breakdown of fatty acids. This occurs during periods of starvation when blood glucose levels drop and no further source of carbohydrate fuel is available. Ketogenesis is able to provide energy by generating acetyl CoA to be fed into the citric acid cycle. This occurs in the liver.
Ketolysis is the utilization of ketone bodies by converting them to acetyl CoA for energy. This occurs in organs other than the liver (mainly the heart and brain). The liver is lacking an essential enzyme for the utilization of ketone bodies for energy.
99
What is the importance of ketolysis to CNS function during prolonged periods of fasting?
When blood glucose is low, β-oxidation and ketogenesis occur in the liver. Ketone bodies are transported out of the liver to key tissues, where they can be used for energy through ketolysis. The brain (and CNS) in particular relies on ketone bodies when glucose is not abundant. Most other tissues and organs can use fatty acids for energy when glucose is low, but the CNS relies on glucose primarily, and ketone bodies during periods of starvation, for fuel.
100
Suppose each of the following biomolecules or structures were radioactively labeled and then identified in vivo during normal physiological functioning. In which cellular compartment would each of the following be found in greatest abundance?
a) pyruvate,
b) oxaloacetate,
c) phosphofructokinase-1 (glycolysis enzyme),
d) PDH complex,
e) phosphoenolpyruvate,
f) glycogen synthase,
g) pyruvate carboxylase,
h) transketolase/transaldolase, i) -ketoglutarate
j) succinate dehydrogenase, k) ATP synthase,
l) carnitine-acylcarnitine translocase,
m) fatty acids undergoing -oxidation,
n) citrate,
o) ketolysis,
p) argininosuccinate (the urea cycle),
q) carbamoyl phosphate (the urea cycle),
r) citrulline (the urea cycle),
s) ornithine (the urea cycle),
t) malate.
a) glycolysis – pyruvate – cytosol
b) krebs cycle- mitochondrial matrix
c) phosphofructokinase-1 – glycolysis- cytosol
d) PDH complex – intermediate between glycoslysis and krebs cycle – mitochondrial matrix
e) Phosphoenolpyruvate- glycoslysis- cytosol.
f) Glycogen synthase- make glycogen- glycogenesis – cytosol primarily of liver cells, and in kidney cortex cells to a lesser degree
g) Pyruvate carboxylase - mitochondrial matrix of liver cells/some kidney cells (NOTE: First, pyruvate carboxylase converts oxaloacetate to pyruvate in the matrix, gluconeogenesiss then continues in the cytosol)
h) Transketolase/ transaldolase - cytosol—primarily of liver cells
i) Alpha ketoglutarate- krebs cycle- mitochondrial matrix
j) Succinate dehydrogenase- krebs cycle- mitochondrial matrix
k) ATP synthase- ETC cycle- inner mitochondrial membrane
l) Carnitine- acylcarnitine translocase- carnitine shuttle- inner mitochondrial membrane
m) Fatty acids undergoing beta-oxidation - mitochondrial matrix (fatty acids are activated in the cytosol, and very long chain fatty acids are oxidized first in peroxisomes, so you might find traces of radioactivity there, but the question asks for where it will be in abundance, which would be in the matrix)
n) Citrate- krebs cycle- mitochondrial matrix
o) Ketolysis- mitochondrial matrix of cells throughout the body during fasting or starvation, but NEVER In the liver—it lacks the necessary enzymes (on the other hand ketogenesis occurs only in the matrix of liver cells, because the enzymes needed are only found in the matrix)
p) Argininosuccinate (urea cycle)- cytosol primarily of liver cells
q) Carbamoyl phosphate (urea cycle)- mitochondrial matrix (from carbamoyl phosphate synthetase 1, one of the two mitochondrial urea cycle enzymes),
r) Citrulline (urea cycle)- mitochondrial matrix and cytosol
s) Ornithine (urea cycle)- mitochondrial matrix
t) Malate- BOTH the cytosol and the matrix (malate is part of the TCA cycle in the matrix and participates in the Citrate shuttle in the cytosol).
101
3) Tonodenafil is an experimental diet drug designed to prevent the storage of excess food calories as fat by interfering with fatty acid synthesis during the well-fed state. What is an appropriate carrier molecule, and a likely cellular target, respectively, for the administration of Tonodenafil?
A) Hydrophilic carrier; nucleus
B) Lipophilic carrier; mitochondrial matrix
C) Hydrophilic carrier; mitochondrial matrix
D) Lipophilic carrier; cytosol
Answer D, even if one did not understand the issues of polarity and passage through the cell membrane. All other choices are false because fatty acid synthesis occurs in the cytosol.
102
What does it mean, metabolically to be in a well fed state?
- first few hours after eating a meal
- high insulin levels, low glucagon levels
- high relative anabolism
- high rate of glycogen and fatty acid synthesis.
103
what does it mean to be in the fasting state?
- high glucagon levels low insulin levels
- high relative rate of catabolism
- increase in glycogenolysis
- delayed (increased) in gluconeogenesis
104
what does ti mean to be in a state of starvation?
- very high glucagon and epinephrine levels
- very high rate of gluconeogenesis
- high rate of fatty acid oxidation- result in ketone bodies and acidosis.
105
what tissue specific metabolism occurs in liver tissue?
Glucose in well-fed state;
| Fatty acids during fasting, but NO ketones (lacks enzyme)
106
what tissue specific metabolism occurs in skeletal tissue?
Glucose during well fed state' fatty acids and ketones if fasting.
107
what tissue specific metabolism occurs in the brain?
glucose during well fed state and fasting; ketones if prolonged starvation.
108
what tissue specific metabolism occurs in adipose tissue?
glucose in well fed state; fatty aids during fasting
109
what tissue specific metabolism occurs in red blood cells?
glucose in all states; always via anaerobic glycolysis.
110
What hormones regulate appetite?
leptin- hormone made by adipose cells that helps to regulate energy balance by inhibiting hunger.
ghrelin- hunger hormone- increase appetite
orexin aka hypocretin, is a neuropeptide that regulates arousal, wakefulness, and appetite. The most common form of narcolepsy, in which the sufferer briefly loses muscle tone (cataplexy), is caused by a lack of orexin in the brain due to destruction of the cells that produce it.
111
How many calories are in one gram of a)fat,b)protein,c)carbohydrate?
a) 9 kcal/g, b) 4 kcal/g, c) 4 kcal/g.
112
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4) In the synthetic scheme shown in Figure 1, carbon 2 of the acetyl-CoA molecule becomes carbon:
A) 1 of HS-ACP
B) 3 of butanoyl -CoA
C) 4 of butanoyl-CoA
D) 3 of -hydroxy-butanoyl-CoA
```
To answer this question, one must carefully examine the structural changes occurring in step (c). The acetyl group attaches to the other reactant, with the loss of CO2, to form -ketobutyrate. The identity of the carbon can be deduced by considering the necessary rearrangement that will result in the formation of CO2 and HS-ACP. Alternatively, if one is familiar with fatty acid biosynthesis it is known that acetyl groups are added to the end of the growing fatty acid chain, meaning the last carbon on the activated acetyl (carbon 2) will become the last carbon on the product fatty acid. Answer C is therefore correct.
113
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Steps (e) and (f) in Figure 1 represent which kind of reaction, respectively?
A) Dehydration and reduction
B) Dehydration and oxidation
C) Oxidation and reduction
D) Reduction and oxidation
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e) dehydrogenation
f) oxidation of NADH and reduction of molecule
A
114
where does fatty acid synthesis primarily occur?
cytosol of liver cells
115
what is fatty acid synthesis making?
primariily/ alwasy construction of 16 carbon palmitic acid; he only fatty acid the human body can synthesize from scratch.
116
Fatty acid synthesis requires acetyl CoA, which is primarily found in the mitochondrial matrix due to krebs. so how is acetyl CoA brought over to cytosol?
citrate shuttle
117
how does citrate shuttle works starting with oxaloacetate in mitochondria to cytoplasm and back?
oxaloacetate --> citrate --> citrate through tricarboxylate translocate from mitochondria to cytoplasm --> oxaloacetate --> part to fatty acid synthesis --> malate --> pyruvate in cytoplasm to pyruvate in mitochondria --> oxaloacetate in mitochondria.
