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glycolysis Flashcards

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1
Q

glycolysis involves a sequence of reactions that metabolizes:

A

1 molecule of glucose to 2 molecules of pyruvate and generates 2 molecules of ATP

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2
Q

under aerobic conditions, pyruvate is

A

completely oxidized generating much more ATP

aerobic system is more efficient than anaerobic

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3
Q

complete oxidation is more energy efficient than

A

anaerobic glycolysis

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4
Q

sources of glucose in diet:

A

disaccharides (especially sucrose and lactose)

starch

glycogen

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5
Q

in mammals:

glucose is the only fuel that brain uses under

glucose is the only fuel that ______ cells can use

A

conditions of non-starvation

red blood

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6
Q

pyruvate and lactate can be salvaged and resynthesized to glucose via

A

gluconeogenesis

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7
Q

glucose uptake occurs via protein transporters called

A

glucose transporters (GLUTs)

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8
Q

GLUT 1

A

ubiquitous but expressed highly in brain, RBCs, cornea, placenta, and cancer cells

high affinity

unregulated

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9
Q

GLUT 2

A

main transporter in liver (also pancreas)

low affinity

unregulated

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10
Q

GLUT 3

A

main transporter in neurons

high affinity

unregulated

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11
Q

GLUT 4

A

present in skeletal muscle, heart, and adipose tissue

insulin dependent

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12
Q

largest GLUT transporter

A

GLUT 2

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13
Q

smallest GLUT transporter

A

GLUT 1/3

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14
Q

location of glycolysis

A

occurs in cytoplasm of eukaryotic cells

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15
Q

two stages of glycolysis

1.

2.

A
  1. trapping of glucose and its cleavage into 2 interconvertible 3-carbon molecules
  2. generation of ATP
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16
Q

first stage of glycolysis begins with:

ends with

A

the phosphorylation of glucose

the isomerization of dihydroxyacetone phosphate to glyceraldehyde 3-phosphate (GAP)

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17
Q

trapping of glucose (through GLUTs) and preparation phase:

ATPs consumed:

ATPs generated:

A

2 ATPs consumed

no ATPs generated

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18
Q

strategy of stage 1 is to:

and form a compound that can be readily cleaved into:

A

trap the glucose in the cell

2 phosphorylated 3-carbon units

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19
Q

stage 1 step 1

ATP:

enzyme:

A

glucose phosphorylated to glucose-6-phosphate (G6P)

ATP is consumed

enzyme: hexokinase (in all tissues) and glucokinase (in liver)

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20
Q

stage 1 step 2

ATP:

enzyme:

A

G6P isomerized to fructose-6-phosphate (F6P)

no ATP

enzyme: phosphoglucoisomerase

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21
Q

stage 1 step 3

ATP:

enzyme:

A

F6P phosphorylated to fructose-1,6-bisphosphate (F1,6BP)

ATP is consumed

enzyme: phosphofructokinase (rate limiting enzyme of glycolysis)

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22
Q

stage 1 step 4

ATP:

enzyme:

A

F1,6BP broken down to glyceraldehyde-3-phosphate (G3P/GAP) and dihydroxyacetone phosphate (DHAP)

no ATP

enzyme: aldolase

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23
Q

stage 1 step 5

ATP

enzyme:

A

DHAP isomerized to G3P (GAP)

no ATP

enzyme: triose phosphate isomerase

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24
Q

second stage of glycolysis:

energy harnessed in _____ used to form _____

A

GAP

ATP

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25
stage 2 step 1 NAD+ enzyme:
oxidative phosphorylation of GAP to form 1,3-bisphosphoglycerate (1,3-BPG) NAD+ reduced to NADH enzyme: glyceraldehyde 3-phosphate dehydrogenase (GAPDH)
26
NADH contains
a pair of "high energy" electrons | sent to ETC, plays role in oxidative phosphorylation
27
stage 2 step 2 ATP: enzyme:
1,3 BPG is converted to 3-phosphoglycerate (3-PG) ADP is phosphorylated to form ATP enzyme: phosphoglycerate kinase
28
stage 2 step 3 ATP enzyme:
3-PG is converted to 2-phosphoglycerate (2-PG) no ATP enzyme: phosphoglycerate mutase
29
stage 2 step 4 water: enzyme:
2-PG is dehydrated to form phosphoenolpyruvate (PEP) water is formed enzyme: enolase
30
stage 2 step 5 ATP: enzyme:
PEP is converted from unstable enol to pyruvate, a stable ketone ATP is formed enzyme: pyruvate kinase this step is irreversible
31
pyruvate can be reduced to
lactate, with the generation of NAD+
32
pyruvate can be oxidized aerobically via the
citric acid cycle after first undergoing an oxidative decarboxylation to form acetyl CoA and producing CO2
33
yeast and some other microorganisms can convert pyruvate to
ethanol | fermentation
34
pyruvate --> lactate produces NAD+ that can be used in what step of glycolysis?
GAP --> 1,3 BPG
35
sucrose is a disaccharide of
glucose and fructose
36
lactose is a disaccharide of
glucose and galactose
37
fructose and galactose can be converted into
glycolytic intermediates
38
fructose quickly turned into ______ in times of high energy
fat
39
what is important about fructose metabolism?
it bypasses the rate limiting step of glycolysis
40
fructose metabolism:
1. fructose --> fructose 1-phosphate via enzyme fructoskinase (ATP --> ADP) 2. fructose 1-phosphate --> glyceraldehyde + DHAP via enzyme fructose 1-phosphate aldolase 3. glyceraldehyde --> G3P/GAP via enzyme triose kinase
41
galactose metabolism
1. galactose --> galactose 1-phosphate via galactokinase 2. galactose 1-phosphate + UDP-glucose --> glucose 1-phosphate via enzyme: galactose 1-phosphate uridyl transferase 3. glucose 1-phosphate --> glucose 6-phosphate via phosphoglucomutase
42
major regulatory enzymes of glycolysis and reactions they catalyze
hexokinase: glucose --> glucose 6-phosphate (ATP --> ADP) phosphofructokinase (rate-limiting step): fructose 6-phosphate --> fructose 1,6 bisphosphate (ATP --> ADP) pyruvate kinase: phosphoenolpyruvate --> pyruvate (ADP --> ATP)
43
glycolysis in at rest muscles (major regulatory enzymes)
glycolysis is inhibited glucose 6-phosphate inhibits action of hexokinase high ATP : AMP ratio inhibits PFK and PK
44
glycolysis in muscles during exercise (major regulatory enzymes)
glycolysis is stimulated glucose 6-phosphate is continuing on in pathway (does not inhibit hexokinase) low ATP : AMP ratio activates PFK and PK
45
goal of glycolysis in muscle
to generate ATP during activity (ATP levels regulate glycolysis)
46
goals of glycolysis in liver
to maintain blood glucose levels to provide building blocks for other pathways
47
glycolysis in liver (major regulatory enzymes)
glucokinase is not inhibited by glucose 6-phosphate (glucose is permanently trapped) (very little hexokinase in live) PFK is activated by F-2,6-BP (inhibited by citrate) PK is regulated by allosteric effectors and covalent modifications (F-1,6-BP activates and ATP inhibits)
48
hexokinase has a ______ affinity for glucose
high
49
glucokinase has a ______ affinity for glucose
low
50
excessive fructose has been linked to
fatty liver, insulin insensitivity, obesity, type II diabetes
51
actions of fructokinase and triose kinase bypass
hte most important regulatory step in glycolysis (PFK rate limiting step)
52
fructose-derived G3P and DHAP are processed by
glycolysis to pyruvate and acetyl CoA in an unregulated fashion
53
excess acetyl CoA (from excess fructose) is converted to
fatty acids which can be transported to adipose tissue to form triacylglycerols, resulting in obesity ; and liver also begins to accumulate fatty acids resulting in fatty liver
54
activity of fructokinase and triose kinase (from fructose consumption) can deplete the liver of
ATP and inorganic phosphate, compromising liver function
55
lactose intolerance
inability to metabolize lactose drinking milk causes disturbances in GI function
56
lactose intolerance is caused by
deficiency in enzyme lactase (which breaks down lactose to glucose and galactose)
57
galactosemia
disruption of galactose metabolism
58
classic galactosemia (most common form)
is an inherited deficiency in galactose 1-phosphate uridyl transferase activity
59
defects in galactose metabolism results in:
failure to thrive vomiting/diarrhea after consuming milk enlargement of liver and jaundice cataracts lethargy and retarded mental development significant elevation of blood-galactose levels and presence of galactose in urine
60
how do you diagnose defect in galactose metabolism
absence of galactose 1-phosphate uridyl transferase in RBCs
61
how to you treat defect in galactose metabolism
remove galatose (and lactose) from diet
62
although elimination of galactose from diet (in patients with defect in galactose metabolism) prevents liver disease and cataract development, many patients still suffer from
CNS malfunction, most commonly a delayed acquisition of language skills
63
cataracts results from
galactose being unable to enter glycolysis and instead being turned into galactitol
64
warburg effect (aerobic glycolysis)
rapidly growing tumor cells metabolize glucose to lactate even in the presence of oxygen
65
visualization of tumor and effectiveness of treatment: a non-metabolizable glucose analog, 2-F-2-D-deoxyglucose detected by a combination of
positron emission tomography (PET) and computer-aided tomography (CAT)

Biochemistry (32 decks)

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