Week 7 Flashcards
(82 cards)
1
Q
the segments of the pentose phosphate pathways
A
- irreversible oxidative
- reversible non-oxidative
2
Q
deficiencies in the oxidative segment of the pentose phosphate pathways results in
A
hemolytic anemia
3
Q
irreversible oxidative portion of the pentose phosphate pathways converts
A
glucose 6-phosphate to ribulose 5-phosphate producing NADPH
4
Q
enzymes required for irreversible oxidative portion of the pentose phosphate pathways
A
- glucose 6-phosphate dehydrogenase
- 6-phosphogluconate dehydrogenase
5
Q
which enzyme regulates the irreversible segment of the PPP
A
glucose 6-phosphate dehydrogenase
6
Q
what inhibits the activity of glucose 6-phosphate dehydrogenase
A
NADPH
7
Q
NADPH is used as
A
- reducing agent
- reducing agent for glutathione in RBC
- fatty acid synthesis
8
Q
Is NADPH oxidized through the ETC?
A
no
9
Q
reversible non-oxidative phase converts
A
ribulose5-phosphate back to glyceraldehyde 3-phosphate and fructose-6-phosphate (intermediates of glycolysis)
10
Q
enzymes of the reversible non-oxidative phose
A
transketolase
transaldolase
11
Q
transketolase
A
moves 2-carbon units
requires thiamin diphosphate cofactor
12
Q
transaldolase
A
move 3-carbon units depending on cellular needs
13
Q
where is PPP the only source of NADPH?
A
RBCs
14
Q
why is NADPH important for RBCs
A
it is required for the reduction of oxidized glutathione which is needed to oxidize hydrogen peroxide
15
Q
glucose 6 phosphate dehydrogenase deficiency
A
can lead to hemolysis and jaundice due to reduced NADPH production
16
Q
fructokinase
A
phosphorylates fructose to fructose 1-phosphate
17
Q
deficiency in fructokinase
A
fructosuria
benign deficiency since fructose is not trapped in the cell
18
Q
aldolase b
A
cleaves fructose 1-phosphate into dihydroxyacetone phosphate and glyceraldehyde which can enter glycolysis
19
Q
why is oxidation of fructose rapid
A
bypasses PFK-1
20
Q
deficiency in aldolase b
A
hereditary fructose intolerance
fructose 1-phosphate is trapped in the liver leading to hepatomegaly and fructose in urine
causes fasting hypoglycermia and vomiting
21
Q
elevated fructose consumption can contribute to
A
increased VLDL synth and therefore hypertriglyceridemia
- gout due to increased purine synth
22
Q
galactokinase
A
phosphorylates galactose taken up into galactose 1-phosphate
23
Q
galactose 1-phosphate uridyl transerase
A
requires UDP intermediate
generates glucose 1-phosphate which may enter glycolysis
24
Q
galactose 1phosphate uridyl transferase deficiency
A
can result in liver failure due to accumulation of galactose 1-phosphate
25
cytosolic pathways that interfaces with glycolysis
pentose phosphate pathway
26
how much atp is directly produced from the oxidation of glucose 6-phosphate in the PPP
none
27
PPP is important for the production of
NADPH
ribose 5-phosphate
glycolytic intermediate - fructose 6-phosphate, glyceraldehyde 3phosphate
28
All rxn in the non-oxidate PPP are ___ and use ___
reversible
| the enzymes transketolase and transaldolase
29
In the PPP, transketolase and transaldolase...
move 2 or 3 carbon units onto other sugardoidies to generate sugar intermediates until glyceraldhyde 3-phosphate or fructose 6-phosphate result
30
key regulatory enzyme for non-oxidative PPP
glucose 6-phosphate dehydrogenase
31
glucose 6-phosphate dehydrogenase will
oxidize glucose 6-phosphate to 6-phosphogluconolactone which will be exoidized and decarboxylated to ribulose 5-phosphate
32
glucose 6-phosphate dehydrogenase regulation
negative by NADPH
33
galactose is ingested mainly as
lactose
34
galactosekinase
phosphorylates dietary galactose once taken up by the cell
35
GALT
activates galactose 1-phosphate to UDP glucose
36
UDP glucose from galactose can be used for
- glycogen synthesis
| - conversion to glucose 6-phosphate for glycolysis
37
glactosemia results from deficiencie in
galactose 1-phosphate urodele transpherase
38
galactosemia results in
elevation of galactose 1-phosphate in the liver which will inhibit hepatic glycogen metabolism and other pathways that require UDP sugars
39
treat infant galactosemia with
lactose free diet
40
fructose is taken up by cells through
facilitated diffusion using glut 5 transporter
41
fructose is principally metabolized where
in the liver
42
aldolase B
cleave fructose into dihydroxyacetone phosphate and glyceraldehyde which can enter the glycolytic pathway
43
rate limiting step for fructose metabolism
aldolase B
44
Aldolast b has lower affinity for ___ than ___. What does this mean
fructose 1-phosphate than fructose 1,6 bisphosphate
it is not a rate limiting step for glucose metabolism like it is for fructose metabolism
45
essential fructosuria
deficiency in fructokinase
benign
fructose in urine
46
hereditary fructose intolerance
deficiency in aldolase B
| accumulation of fructose 1-phosphate that can cause hepatomegaly and fasting hypoglycermia
47
We have a two-week old infant brought to the emergency room due to lack of energy, diarrhea, vomiting, jaundice and an enlarged liver. The physician prescribes a switch from breastmilk to a formula containing sucrose. This switch results in a resolution of the baby's symptoms. What is the most likely diagnosis.
a. deficiency in enzyme in the metabolism of pentose surgars
b. deficiency in enzyme in the pathway that metabolizes glucose
c. intolerance of dietary galactose
d. intolerance to dietary fructose
intolerance of dietary galactose
48
sucrose is
glucose
| fructose
49
Within the red blood cell, NADPH is used for
re-reduce glutathione
50
In the non-oxidative portion of the pentose phosphate pathway, 2-carbon fragments of keto-sugars can be transferred to other sugars to generate a larger sugar molecule. This reaction is catalyzed by
transketolase
51
Cleavage of fructose 1-phosphate into dihydroxyacetone-phosphate and glyceraldehyde is facilitated by which enzyme?
aldolase
52
A patient presents to the emergency department with lactic acidosis. A deficiency in thiamine (TPP) is suspected and this will be consistent with a decrease in the activity of
transketolase
53
Aldolase B facilities a reaction that cleaves fructose 1-phosphate into two 3-carbon molecules that will enter glycolysis as
glyceraldehyde 3-phosphate
54
Galactose 1-phosphate is initially converted to glucose 1-phosphate and requires
UDP-glucose
55
The major regulatory step of the pentose phosphate pathway is catalyzed by which enzyme?
glucose-6-phosphate dehydrogenase
56
This consists of entirely near-equilibrium reactions
non-oxidative phase of PPP
57
Which pathway directly provides oxidizable substrate to red blood cells during the fasted state?
hepatic glycogenolysis
58
steroid hormones bind what types of receptors?
intracellular
59
Shortly after a meal, there will be increased activity in which of the following pathways as a result of increased insulin?
glycolysis
60
Following insulin binding its receptor and autophosphorylation of the β- chain, what is the initial step in this cascade of events?
recruitment of the insulin receptor substrate
61
What is responsible for the degradation of cAMP?
phosphodiesterase
62
A patient is found to have a rare disease in which the secretory function of the α-cells of the pancreas is impaired. As a consequence, glucagon cannot be secreted. Direct stimulation of which of the following pathways in liver will be impaired?
gluconeogenesi
63
PI 4, 5, bisphosphate (PIP2) can be cleaved by phospholipase C to initially generate which of the following second messengers?
Diacylglycerol (DAG) and Inositol 1,4,5 phosphate (IP3)
64
What pathways are not stimulated by high levels of insulin
any catabolic
65
Glutamine can be transaminated to
alpha ketoglutarate
66
An example of a rxn commonly used to replenish intermediates of the TCA cycle
glutamate to alpha ketoglutarate
67
What TCA intermediate is required in the cytosol for FA synth?
citrate
68
Pyruvate dehydrogenase kinase catalyzes a reaction that results in
The phosphorylation and inactivation of E1 subunit of PDC (pyruvate dehydrogenase complex)
69
α-ketoglutarate dehydrogenase is the enzyme responsible for one of the irreversible reactions in the TCA cycle. The enzyme catalyzes
α-ketoglutarate to succinyl-CoA
70
A 2-day-old newborn male is diagnosed with congenital lactic acidosis because of a defective electron transport protein. This deficiency leads to a decrease in the rate at which NADH and FADH2 can be oxidized to produce ATP using oxidative phosphorylation and results in an increase in cytosolic AMP. Under these conditions which glycolytic enzyme would be stimulated?
ohosphofructoskinase-1
71
A patient presents with a deficiency of thiamine. If this patient’s liver cells are compared with normal cells, which of the following products would be decreased in the thiamine-deficient cell (when compared to the normal cells) if the cells are only given glucose as a fuel?
CO@
72
High levels of activity of the non-oxidative portion of the pentose phosphate pathway will directly produce intermediates of which of the following pathways?
glycolysis
73
A family presents for genetic counseling. The couple has two female children who are alive and well; however, their infant son recently died in the nursery with severe hemolysis (lysis of red blood cells) and jaundice. The wife recalls she lost a brother in infancy with severe hemolysis, induced after a viral infection. The physician suspects a glucose-6-phosphate dehydrogenase deficiency, this would result in a deficiency in which of the following compounds in red blood cells?
ribose and NADPH
74
A deficiency in glucose 6-phosphate dehydrogenase reduces the levels of NADPH in the red blood cell. This leads to an increase in which of the following compounds with the cell?
oxidized glutathione
75
Red blood cells lack mitochondria; therefore glucose is primarily oxidized to ribose and which of the following compounds?
lactate
76
In the non-oxidative portion of the pentose phosphate pathway, 2-carbon fragments of keto-sugars can be transferred to other sugars to generate a larger sugar molecule. This reaction is catalyzed by which of the following enzymes?
transketolase
77
Which of the following events occurs during the formation of phosphoenolpyruvate from pyruvate during gluconeogenesis?
CO2 is required
78
Phosphoenolpyruvate carboxykinase is used by ___ pathway but not___
gluconeogenic
| not glycolytic
79
When insulin levels are high, which of the following is true?
Glycogen synthase is dephosphorylated and active
80
What is required to fuly activate pyruvate carboxylase
biotin and acetyl-coA
81
A 7-year-old boy arrives at the emergency department asleep in his father’s arms. The boy’s mother explains that the boy spent the night throwing up and experiencing severe diarrhea. History indicates the boy became ill at dinnertime yesterday after spending time playing in the basement. The mother reports that an exterminator had recently take care of a rat problem in the basement and had used a poison (Rotenone) that blocks complex I in the respiratory chain of oxidative phosphorylation. This will increase levels of NADH and would likely impair function of
pyruvate dehydrogenase complex
82
What sequence of enzymes allows for the synthesis of glycogen from glucose-6-phosphate?
phosphoglucomutase, UDP-glucose pyrophosphorylase, glycogen synthase, amylo-(1,4α1,6)-transglycosylase
