Test 1 adklfjasd;lfj Flashcards
1
Q
Process by which noncarbohydrate precursor molecules are converted into glucose?
A
Gluconeogenesis
2
Q
Another name for glycolysis
A
Embden Meyerhof pathway
3
Q
These organisms cannot survive in the presence of oxygen
A
Obligate anaerobes
4
Q
This substance must be regenerated for glycolysis to proceed
A
NAD+
5
Q
This intermediate is necessary for the conversion of galactose to glucose
A
UDP glucose
6
Q
This molecule is an allosteric inhibitor of phosphofructokinase
A
ATP
7
Q
Transporter that is responsible for fructose uptake in the intestine
A
GLUT5
8
Q
this essential nutrient is required for the carboxylation of pyruvate in humans
A
biotin
9
Q
An allosteric activator of glycolysis
A
AMP
10
Q
Glycolysis produced a net of ___ moles of Amp per one mole of glucose
A
2 ATP
11
Q
Pancreatic ____ is the digestive enzyme primary responsible for the hydrolysis of dietary plant starch
A
a-amylase
12
Q
the key enzyme that regulates the pace of glycolysis is
A
phosphofructokinase
13
Q
The catalytic mechanism of the isomerization of a ketoses into an aldose proceed through an ___ intermediate
A
enediol
14
Q
the common structural domain of NAD+ binding dehydrogenase is often called a ___
A
Rossman fold
15
Q
In alcoholic fermentation, the decarboxylation of pyruvate requires a coenzyme that contains the vitamin___
A
Thiamine or B1
16
Q
A potent allosteric activator of liver phosphofructokinase is ____
-what is it produced from
A
Fructose-2,6-bisphosohate which is produced from fructose 6-Phosphate by PFK2
17
Q
What is the cori cycle
A
the metabolic reactions by which glucose is converted into lactate in skeletal muscle, and then lactate converted back into glucose in the liver
18
Q
What is the first step of gluconeogenesis?
A
carboxylation of pyruvate to form oxaloacetate
19
Q
What is the purpose of phosphorylating glucose in the cytosol?
- trap the glucose in the cell
- to destabilize glucose and facilitate the next series of metabolic steps
- to convert it to more soluble form
A
Trap the glucose in the cell, because there aren’t any transporters for phosphorylated glucose
-actgivates/destabilizes glucose and facilitates the next series
20
Q
Which of the following are reasons that glucose is a common metabolic fuel by living organisms?
- it has a stable ring structure and is unlikely to glycosylate proteins
- it has been found as one of the monosaccharides formed under prebiotic conditions
- it is the only sugar used by the brain
A
- it has a stable ring structure and is unlike to glycosylate proteins
- it has been found as one of the monosaccharides formed under prebiotic conditions
21
Q
What 2 3-carbon molecules are generated by the cleavage of fructose 1,6-bisphosphate?
A
Glyceraldehyde 3-phosphate
Dihydroxyacetone phosphate
22
Q
what is a common mechanistic feature of kinases?
A
Binding of substrate induces cleft closing
23
Q
What reaction is catalyzed by aldolase?
A
reversible cleavage of F-1,6-BP to DHAP and GAP
24
Q
What is the function of glyceraldehyde 3-Phosphate dehydrogenase?
A
Oxidation by NAD+ and formation of acyl-phosphate
25
What is the function of a thioester intermediate such as the one formed from GAP?
The thioester allows the two step reaction to be coupled so the second reaction, the energetically unfavorable phosphorylation can proceed
26
What is substrate level phosphorylation
ATP synthesis when the phosphate donor is a substrate with high phosphorylase transfer potential
27
What is the additional metabolite that is required for the conversion of 3-phosphoglycerate to 2-phosphoglycerate
2,3-Bisphosphoglycerate
28
What are the primary metabolic fates of pyruvate?
Acetyl CoA (aerobic-matrix of mitochondria via pyruvate oxidation)
Anaerobic-Fermentation-cytoplasm
Lactate (higher eukaryotes)
Ethanol (microorganisms)
29
Fructose can enter glycolysis at 2 distinct points, depending on the tissue. How is fructose metabolized in adipose tissue?
Fructose is converted to fructose 6-Phosphate
- via hexokinase
- ATP-> ADP
30
Lactose intolerance is caused by the deficiency of?
Lactase
31
How are the glycolytic enzymes regulated?
- Transcriptional control
- reversible phosphorylation
- allosteric control
ALL of them
- transcriptional control
- reversible phosphorylation
- allosteric control
32
The primary raw material for gluconeogensis are?
Lactate and alanine
33
How many high-energy phosphate bonds are expended in gluconeogenesis?
6
34
Both hexokinase and glucokinase phosphorylate glucose. The function of glucokinase is to phosphorylate glucose in liver cells as a means to regulate blood glucose levels. Would you expect its Km to be higher or lower than hexokinase?
Glucokinase must be responsive to elevated blood glucose concentrations
- Higher Km=lower affinity for glucose
- lower binding affinity allows this enzyme to become more active at high glucose concentrations, which saturate hexokinase
35
What two isomerization reactions occur in glycolysis? why are these steps necessary?
Glucose 6-Phosphate-> Fructose 6-Phosphate
-converting an aldose to a ketose allows phosphorylation at the number 1 carbon
Dihydroxyacetone PHosphate-> Glyceraldehyde 3-Phosphate
-utilize both molecules from the cleave from fructose 1,6-Bisphosphate
36
At equilibrium, there is far more DHAP than GAP. Yet the conversion of DHAP by triose phosphate isomerase proceeds readily.. Why?
The GAP formed is immediately removed by subsequent reactions, resulting in conversion of DHAP into GAP by the enzyme
37
How is the conversion of phosphoenolpyruvate to pyruvate accompanied by ATP formation?
the enol phosphate posses very high potential for phosphoryl transfer, which is due to the driving force of the tautomerizatoin of the enology to the more stable ketone
38
Give the reactions by which glycerol (from fats) can be metabolized into pyruvate or synthesized into glucose
1) glycerol-> glycerol 3-phosphate
- glycerol kinase
- ATP-ADP
2) Glycerol 3-Phosphate-> DHAP
- glycerol phosphate dehydrogenase
- NAD+ to NADH
After Glycerol is converted into DHAP, it is isomerize into GAP which can then either proceed down glycolysis or gluconeogenesis
39
How is glycolysis maintained under anaerobic conditions?
Pyruvate can be reduced to either lactate or ethanol, and this reaction is accompanied by the oxidation of NADH to regenerate NAD+
40
How does citrate influence glycolysis
Phosphofructokinase is inhibited by citrate, which is an intermediate in the citric acid cycle
- If citrate levels are high, enzyme is inhibited and fewer glucose molecules are metabolized
- high levels in the cytoplasm indicate that biosynthetic precursors are abundant so no need to degrade additional glucose
Citrate serves as a cell indicator
41
Why is it more sensible for phosphofructokinase to be an important control step rather than hexokinase?
PFK catalyzes the first commited step in glycolysis pathway.
While Hexokinase
-the production of G6P is the first step in may different pathways
42
What two functions are attributed to substrate cycles?
The substrate cycles regulate glycolytic path flux by amplifying metabolic signals and they generate body heat produced by the hydrolysis of ATP
43
Where does the citric acid cycle take place?
matrix of the mitochondria
44
These proteins are tightly associated with FAD or FMN?
Flavoproteins
45
What is the intermediate between citrate and isocitrate
cis-aconitate
46
What is the location of succinate dehydrogenase
inner membarne of mitochondria
47
This TCA intermediate is both at the beginning and at the end of the citric acid cycle?
Oxaloacetate
48
This is one of the products of the citric acid cycle?
CO2
49
This is a name suggested for associated multi enzyme complexes in metabolism
metabolon
50
This substance is toxic because it reacts with neighboring sulhydryl groups of dihydrolipoyl groups and it blocks deoxidation to lipoamide
arsenite
51
This type of enzyme regulation process inhibits the pyruvate dehydrogenase complex
phosphorylation
52
This is the name applied to metabolic reactions that replenish citric acid cycle intermediates that are depleted because they were used for biosynthesis
anaplerotic
53
Carbons from carbohydrate enter the citric acid cycle in the form of
Acetyl CoA
54
In the citric acid cycle the ___ is produce by substrate level phosphorylation
GTP
55
E1 of the pyruvate dehydrogenase complex requires the coenzyme ___ for proper activity
TPP
| Thiamine Pyrophosphate
56
E2 of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached to a ___ residue of the enzyme
Lysine
57
___ is a citric acid cycle enzyme that is also an example of an iron-sulfur protein
Aconitase or Succinate dehydrogenase
58
The ___ cycle is a process by which plants and some bacteria can convert two-carbon acetyl units into four carbon units(succinate) for glucose synthesis, energy production, and biosynthesis
Glyoxylate
59
During the oxidation of isocitrate, the intermediate that is decarboxylated to form alpha-ketoglutarate is
oxalosuccinate
60
In general the citric acid cycle is inhibited under __ energy charges?
High
61
___ is the first citric acid cycle intermediate to be oxidized
isocitrate
62
Beriberi is caused by the deficiency of___
Thiamine
| TPP
63
What molecule initiates the citric acid cycle by reacting with oxaloacetate?
acetyl CoA
64
What enzyme is(are) responsible for the reaction:
| Pyruvate + CoA + NAD+ -> Acetyl CoA +NADH+ H+ + CO1
Pyruvate dehydrogenase complex
65
what are the steps involved (in order) in the conversion of pyruvate to acetyl CoA
decarboxylation, oxidation, transfer to CoA
66
What vitamins are precursors to coenzymes that are necessary for formation of Acetyl CoA from pyruvate?
```
Thiamine
Riboflavin
Niacin
Lipoid acid
Pantothenic acid
```
67
What functions as a "flexible swing arm" when it transfers the reaction intermediate from one active site to the next?
Lipoamide
68
Formation of citrate from acetyl CoA and Oxaloacetate is a __ reaction
condensation
69
What is/are the chemical changes involved in the conversion of citrate into isocitrate?
dehydration followed by hydration
70
In which reaction is GTP (or ATP) directly formed in the citric acid cycle?
conversion of Succinyl CoA to Succinate
71
In which step of the citric acid cycle is FADH2 formed?
Succinate to fumurate
72
What conditions will activate pyruvate dehydrogenase kinase which catalyzes the phosphorylation and inactivation of E1 in the pyruvate dehydrogenase complex?
elevated concentrations of NADH and ATP
73
Approximately how many ATP or GTP equivalents are produced during one turn of the citric acid cycle?
10
74
In addition to pyruvate dehydrogenase, what other enzymes are key regulatory sites in the citric acid cycle?
isocitrate dehydrogenase
a-ketogluterate dehydrogenase
citrate synthase (in bacteria)
75
They glyoxylate cycle enables plants to survive using only?
acetate
76
List the 5 coenzymes that are required for the oxidative decarboxylation of pyruvate and a-ketoglutarate and give the essential nutrient (vitamin) that is required for each
```
Thiamine pyrophosphate (TPP)-thiamine, B1
Lipoamide- lipoic acid
NAD+, niacin
FAD- riboflavin, B2
Coenzyme A-pantothenic acid
```
77
Explain why GTP is energetically equivalent to an ATP in metabolism
nucleoside diphosphokinase reversibly transfers a P group from GTP to ATP
78
Why is the observed electron transfer from FADH2 to NAD+ unusual?
it is unusual because the electrons are passed to the NAD+ from FADH2
-transfer usually in other direction
79
How is succinate dehydrogenase unique when compared to other enzymes in the citric acid cycle?
only enzyme embedded in the mitochondrial inner membarne
| -directly associated with electron transport chain
80
where does oxidative phosphorylation occur in eukaryotes?
Mitochondria
81
An ATP-generating process in which an inorganic substance such as oxygen serves as the ultimate electron acceptor?
Respiration
82
The permeability of the outer mitochondrial membrane is primarily due to the presence of these substances
Porins
83
This electron carrier is a derivative of quinone and has an isoprenoid tail
coenzyme Q
84
This enzyme catalyzes the reduction of O2
cytochrome c oxidase (C)
85
This prosthetic group is present in complex I, II, III of electron transport
iron-sulfur clusters
86
This citric acid enzyme is also apart of an electron-transport complex?
succinate dehydrogenase
87
This is the name given to the hypothesis proposed by Peter Mitchell Explain how ATP synthesis is coupled to electron transport
Chemiosmotic theory
88
Atractyloside inhibits this mitochondrial protein
ATP-ADP translocase
89
This is a process by which cytoplasmic NADH can be re-oxidized by O2 using the electron-transport system
malate aspartate shuttle
90
A strong oxidizing agent has a strong tendency to ___ electrons
acept
91
In the initial step of Complex I, two high-potential electrons are transferred from NADH to the __ prosthetic group of the complex
FMN
92
cytochrome ___ is the only water-soluble cytochrome of the electron transport chain
c
93
Complex III contains two Heme A groups and 3___ions
copeer
94
___ carries electrons from complex III to complex IV
cytochrome C
95
The transfer of a single electron to O2 forms the reactive __ ion
superoxide
96
__ is a molecular assembly in the inner mitochondrial membrane that carries out synthesis of ATP
ATP synthase
97
In the glycerol phosphate shuttle, cytoplasmic glycerol phosphate dehydrogenase uses cytoplasmic NADH to reduce ___ to glycerol 3-Phosphate
DHAP
98
Acceptor control of oxidative phosphorylation means that the rate of respiration depends upon the level of ___
ADP
99
___ is a poison because it blocks the flow of electrons from cytochrome c to oxygen
```
CO
or Cyanide (CN-)
or Azide (N3-)
```
100
What type of gradient is critical to ATP formation by oxidative phosphorylation
Proton Gradient
101
When glucose is totally oxidized to CO2 and H2O, how many ATP molecules are made by oxidative phosphorylation relative to the maximum yield?
26 out of 30
102
What is the chemical effect of oligomycin on aerobic metabolism?
Blocks the proton transfer through F0 of ATPsynthase and therefore blocks the phosphorylation of ADP to form ATP
103
What is the correct path taken by a pair of electrons as it travels down the electron transport chain?
FADH2-> Complex II-> CoQ->Complex III->Cytoplasms C->complex IV-> O2
NADH->Complex I
104
In prokaryotes the site of ATP-synthesizing machinery is
cytoplasmic membrane
105
electron flow down the electron transport chain leads to
transport of protons across the inner mitochondrial membrane from inside the matrix to the inter membrane space
106
Coenzyme Q is also called?
Ubiquinone
107
What complex in ETC doesn't pump protons?
Complex II
108
In proteins these amino acid residues usually complex to the iron sulfur clusters
Cys
109
What is a cytochrome
protein that transfers electrons, and also contains a heme prosthetic group
110
In the rieske center, the iron sulfur center is coordinate to the Amino acid(s)?
His
111
What is the net ATP obtained rom one cytoplasmic NADH when it is reoxidizes by the electron transport chain using the glycerol 3-phosphate shuttle?
2
112
In the malate aspartate shuttle, electrons from NADH are transferred to ___, forming malate
oxaloacetate
113
Explain why less ATP is made from the reoxidation of FADH2 as compared to NADH
complex II doesn't pump protons thus fewer ATP molecules are ultimately made (Complex I does pump protons)
114
How is oxidative phosphorylation regulated?
Acceptor Control
- electrons do not flow unless ADP is available to be simlutaneously phosphorylated to ATP
- therefore synthesis of ATP does not occur unless ADP levels are high
