Carbohydrates Metabolism III: The Pentose Phosphate Pathway

pentose phosphate pathway (PPP)

functions of the __________:

1) source of NADPH for biosynthesis of fatty acids, cholesterol, hormones, neurotransmitters, and nucleotides; and detoxification by reduction of oxidized glutathione and cytochrome P450

2) source of pentose sugars for DNA and RNA synthesis and metabolism of dietary pentose sugars

NADPH

the pentose phosphate pathway is a source of ___________ for biosynthesis of fatty acids, cholesterol, hormones, neurotransmitters, and nucleotides, as well as detoxification by reduction of oxidized glutathione and cytochrome P450

NADPH, NADH

___________ is a coenzyme geared towards more lipid biosynthesis, whereas ____________ is a coenzyme geared more towards glycolysis, citric acid cycle, and oxidative phosphorylation

glutathione

tripeptide that can be oxidized and reduced because it has a cysteine that can form disulfide bridges; can act as an oxidizing agent

cytochrome P450

metabolizes drugs by oxidizing them

pentose

the PPP is a source of ___________ sugars necessary for DNA and RNA synthesis

PPP location

liver, adipose tissue, thyroid, testis, lactating mammary glands, adrenal cortex, and RBCs

hormone

the thyroid, testis, and mammary glands need NADPH for _____________ production

adrenal cortex

the _______________ needs NADPH for cortisol and cholesterol synthesis

RBCs

glutathione protects _____________ from oxidation

muscle

the PPP does not occur in ___________ because it benefits from catabolic pathways (gets products of PPP)

oxidative

phase 1 of the PPP is the ______________ phase: generate NADPH from NADP+ when converting glucose-6-phosphate to ribulose-5-phosphate (ketose)

non-oxidative

phase 2 of the PPP is the ______________ phase: generates sugars needed for nucleic acid synthesis; chops off one or two carbons and moves them to another sugars - can end up with many types of monosaccharide sugars ranging from 3-7 carbons

HMP (hexose monophosphate) shunt

another name for the pentose phosphate pathway, along with the phosphogluconate pathway

glucose 6-phosphate dehydrogenase

main regulatory enzyme of the oxidative phase of the PPP; converts the hemiacetal to a cyclic ester

increase

high NADP+ levels, high insulin, and a need for intermediates (DNA/RNA) _______________ activity of glucose 6-phosphate dehydrogenase in the PPP

decrease

the fasting state will ____________ activity of glucose 6-phosphate dehydrogenase in the PPP

lactonase

enzyme that opens the ring on 6-phosphoglucono delta-lactone and converts it into 6 phosphogluconate

6-phosphogluconate dehydrogenase

converts 6-phosphogluconate into ribulose 5-phosphate, releasing CO2 and consuming NADP+

phosphopentose isomerase

enzyme that converts ribulose 5-phosphate into ribose 5-phosphate or Xylulose 5-phosphate, beginning the non-oxidative phase of the PPP

transketolase

Enzyme that adds a carbon to a ketose sugar

transaldolase

enzyme that adds carbon to an aldose sugar

glyceraldehyde

_______________3-phosphate is the 3 carbon sugar in the non-oxidative phase of the PPP

erythrose

_______________4-phosphate is the 4 carbon sugar in the non-oxidative phase of the PPP

xylulose

_______________5-phosphate is the 5 carbon sugar in the non-oxidative phase of the PPP

fructose

______________6-phosphate is the 6 carbon sugar in the non-oxidative phase of the PPP

sedoheptulose

_____________ 7-phosphate is the 7 carbon sugar in the non-oxidative phase of the PPP

3, 2, 1

the net reaction of the PPP is ____ pentose 5-phosphate produce ____ fructose 6-phosphate and ____ glyceraldehyde 3-phosphate

ribose 5-phosphate

need ____________________ more than energy

resources are channeled into the PPP

ribose 5-phosphate and NADPH

equal need for _________________ and _____________

glucose 6-phosphate is taken from glycolysis and moved to the PPP

NADPH

more ______________ is needed, probably for fatty acid synthesis

recycle intermediates

NADPH and ATP

more ____________ and ____________ are needed

balance where glyceraldehyde 3-phosphate goes

favism

condition in which individuals with a glucose 6-phosphate deficiency develop hemolytic anemia when they consume fava beans, which contain gwo glycosides that are digested in the GIT to highly oxidizing aglycones: divicine and isouramil.

glucose 6-phosphate dehydrogenase

individuals with a ________________________ deficiency may develop hemolytic anemia after consuming fava beans because NADPH cannot be produced in sufficient amounts, and therefore glutathione cannot be reduced to serve as an antioxidant for erythrocytes