glycolysis and Gluconeogenesis Flashcards
The equation for glycolysis
glucose—-> two molecules of pyruvate + 2ATP
is glycolysis anaerobic or aerobic
anaerobic
Where does glycolysis occur
The cytoplasm
In mammals what is the only fuel that the brain uses under nonstarvation conditions
glucose
In mammals what is the ONLY fuel that red blood cells can use
Glucose
Pyruvate and lactate can be salvaged by being resynthesizes to glucose in the metabolic process of
gluconeogenesis
Sources of glucose in the diet
Starch, Glycogen, Disaccharides (especially sucrose and lactose)
GLUT 1 has a _____ affinity for glucose and is mostly found where
high, RBCs
GLUT2 is the main transporter of glucose in the
Liver
GLUT2 has a _____ affinity with ____ regulation
low affinity, No regulation
GLUT3 is the main glucose transporter in
Neurons
GLUT4 is mostly found in
skeletal muscle, heart, adipose
GLUT4 are dependent on
Insulin
Glycolysis occurs in the
Cytosol
What is the purpose of Stage 1 of glycolysis
Trapping and preparation phase
How many ATP are produced in stage 1 of glycolysis
none. 2 ATP are actually consumed
What is the final product of stage 1 of glycolysis
Fructose 1,6 Biphosphate
Stage 1 of glycolysis consists of how many steps
3: A phosphorylation, an isomerization, and a second phosphorylation reaction
What is the principle strategy of stage 1 of glycolysis
to trap the glucose in the cell and form a compound that can be readily cleaved into 2 phosphorylated 3 carbon units
What are the two irreversible enzymes used in stage 1 of glycolysis
step one- Hexokinase/Glucokinase (in the liver)
step 3: Phosphofructose kinase (PFK) (committed step)
what are some differences between hexokinase and glucokinase
Glucokinase is in the liver and pancreas B cells while hexokinase is in all other tissues
Hexokinase is readily inhibited by Glucose 6-Phosphate; Glucokinase is not
Glucokinase is has positive feeback from glucose, fructose 1-phosphate, and insulin)
Glucokinase has negative feeback from Glucagon and fructose 6-phosphate
What is PFK inhibited by
ATP and Citrate
What is AMP induced by
AMP, Fructose 2,6 Biphosphate
Hexokinase like all other kinases requires what for activity
Magnesium or another divalent metal ion
The isomerization of glucose 6-phosphate to fructose 6-phosphate is a conversion of an ____ into a _____
aldose into a ketose
What is the allosteric enzyme that sets the pace of glycolysis
PFK
aldolase converts F-1,6 BP into
DHAP and GAP
what is the only glycolytic enzymopathy that is lethal
Triose phosphate isomerase deficiency
When there is high ATP, high NAD+, and low NADH
DHAP is favored over GAP and converted to
Glycerol 3-phosphate—–> triacylglycerols—> fat
Stage 3 of glycolysis is started by oxidative phosphorylation fo GAP to form _____ (and the reduction of ___ to ____)
1,3 BPG ( and the reduction fo NAD+ to NADH)
In stage 3 of glycolysis ADP is phosphorylated to ATP by enzyme ______ and 3-PG is formed via _____
Phosphoglycerate kinase, via substrate transfer
What does phosphoglycerate mutase do in glycolysis
it moves the phosphate on 3-phosphoglycerate to the 2 carbon thus forming (2-phosphoglycerate)
What does Enolase do in glycolysis
Dehydration of 2-PG forms PEP (phosphoenolpyruvate), an enol with high phosphoryl-transfer potential (unstable)
What does pyruvate kinase do in glycolysis
transfers phosphoryl group form PEP to ADP to form ATP
PEP is converted from unstable enol to pyruvate, a stable ketone
What are the three enzymes in glycolysis that are irreversible
Hexokinase/glucokinase
PFK (phosphofructokinase)
pyruvate kinase
In aerobic environment pyruvate goes to the
TCA cycle
In an anaerobic environment pyruvate is converted to ____ by _____ and ____
lactate, lactate dehyrogenase and NADH
Pyruvate kinase is induced by
insulin
fructose 1,6 BP
Pyruvate kinase is inhibited by
Alanine
ATP
Glucagon
Pyruvate can be converted into what three things
Ethanol, lactate, and Acetyl CoA
Alcoholic fermentation and lactate production have no net oxidation-reduction why
The NADH formed in the oxidation of glyceraldehyde 3-phosphate is consumed in the reduction of pyruvate
Fructose from the liver can enter the glycolysis pathway as
DHAP and GAP
Fructose can enter as _____ from most most tissue other than the liver
Fructose-6P (F-6P)
Galactose enters the glycolysis pathway as
Glucose-6P (G-6P)
In the liver F-2,6-BP has what regulatory effect
Activates PFK
What effect does citrate have on PFK
it inhibits it in the liver
Pyruvate kinase is regulated by
allosteric effectors and covalent modification
High levels of glucagon and low levels of insulin leads to what
increase in cAMP pathway and thus increase in protein kinase A this leads to an increase in Fructose 6-Phosphate. Also leads to an inhibition of pyruvate kinase. This means an increase in gluconeogenisis and an inhibition of glycolysis
The brain depends on what as its primary fuel source
glucose
what is RBCs only fuel source
Glucose
The daily glucose requirement of the brain is about
120g
What is the whole bodies daily glucose need
160g
How much glucose is present in body fluids
about 20grams
how much glucose is readily available from glycogen
190grams
How long are direct glucose reserves sufficient to meet glucose needs
for about a day
Neurotransmitters in the brain (Glutamate, Glutamine, GABA) are formed form intermediates of
The TCA cycle in the brain (more specifically alpha-ketoglutarate)
What are the major precursors of gluconeogenesis
Lactate, amino acids, and glycerol (but not fatty acids)
What is the purpose of gluconeogenesis
converts pyruvate into glucose
What are the four enzymes that are present in the gluconeogensis pathway but not in glycolysis
pyruvate carboxylase—- converts pyruvate (with ATP, and HCO3) to oxaloacetate ( ADP and Phosphate released)
phosphoenolpyruvate carboxykinase- converted with GTP converts oxaloacetate to phosphoenolpyruvate (GDP and CO2 released)
Fructose 1,6-bisphosphatase- converts fructose 1,6 diphosphate with H2O (Phosphate released)
Glucose 6-phosphatase- with H2O converts glucose 6-phosphate to glucose (phosphate released)
what is the mitochondrial enzyme in gluconeogensis
Pyruvate carboxylase
What happens to oxaloacetate before further gluconeogensis
it is transported to the cytoplasm via the malate shuttle
Where is glucose 6-phosphatase located
in the lumen of the ER
Glycolysis _____ ATP, Gluconeogenesis _____ ATP
generates, consumes
F-2,6 BP and AMP activates
glycolysis, more specifically PFK and the converion of fructose 6-phosphate to fructose 1,6 diphosphate
fructose 2,6-BP and AMP inhibit
Gluconeogenesis, more specifically inhibit fructose 1,6 biphosphatase and the conversion of Fructose 1,6-BP to fructose 6-phosphate
ATP inhibits
PFK and Pyruvate kinase
Alanine inhibits
Pyruvate kinase
Fructose 1,6 BP activates
glycolysis and more specifically pyruvate kinase
AMP regulatory effects
inhibits gluconeogensis and more specifically fructose 1,6 bisphosphatase
What regulatory effect does H+ have
inhibits PFK and thus inhibits glycolysis
What regulatory effect does ADP have
inhibits phosphoenol pyruvate carboxykinase and thus gluconeogensis
What regulatory effect does alanine have
inhibits pyruvate kinase and thus glycolysis
what regulatory effect does acetyl CoA have
activates pyruvate carboxylase thus activates gluconeogenesis
what is the regulatory effect of ADP
inhibits pyruvate carboxylase thus inhibits gluconeogensis
tissue location of gluconeogenesis
liver (mostly), kidneys, small intestines
Favoring conditions for gluconeogensis
when blood (glucose) levels are low and glycogen stores are depleted
Favoring conditions for glycolysis
Favored when blood (insulin) is high
Tissue location for glycolysis
RBCs, exercising tissues, brain, etc.
Subcellular location of glycolysis
in the cytosol
Subcellualr location of gluconeogensis
cytosol and mitochondria
Postive regulators of glycolysis
Glucose, insulin, AMP, Fructose 2,6-BP, fructose 1,6-BP
Postive regulators of gluconeogenesis
glucagon, citrate, cortisol, thyroxine, acetyl CoA
negative regulators of glycolysis
Glucagon, ATP, Citrate, Glucose-6 phosphate, fructose 6-phosphate, alanine
negative regulators of gluconeogenesis
ADP, AMP, Fructose 2,6-BP
energy use and yield of glycolysis
uses: 2 ATP
Yield: 4 ATP
Net yield: 2 ATP/glucose oxidized (also produces 2 NADH)
energy use and yield of gluconeogensis
Uses: 4 ATP, 2 GTP
Yield: 0
Net use: 6 ATP equivalents/ glucose synthesized
Sucrose is a disaccharide of
glucose and fructose
Lactose is a disaccharide of
glucose and galactose
Fructose and galactose are converted into glycolytic
intermediates
Fructose is quickly turned to fat in times of
high energy
Fructose from the liver enters the glycolytic pathway where
DHAP/GAP
Fructose form adipose tissue enters the glycolytic pathway where
Fructose -6P
Galactose enters the glycolytic pathway where
Glucose-6P
Glycogen enters the glycolytic pathway where
Glucose-6P
In the liver what is the main activator (s) for glucokinase
Glucose, Fructose 1-P, insulin
In the liver what is the main inhibitor (s) for glucokinase
glucagon, fructose 6-P
In the liver what is the main inhibitor of PFK
Citrate
What is the main activator for PFK in the liver
Fructose 2,6-BP
In the liver pyruvate kinase is largely regulated by
allosteric effectors and covalent modification
Meaning ATP and alanine inhibit and Fructose 1,6-BP induce
Pyruvate can be oxidized aerobically via the citric acid cycle after first undergoing
an oxidative decarboxylation to form acetyl CoA
Glucose 6-phosphatase is only found in
liver, kidneys, pancreatic Beta cells
Cortisol increases the activity of what two enzymes
Fructose 1,6 bisphosphatase, glucose 6-Phosphatase thus leading to increase in gluconeogenesis
Pyruvate carboxylase is a _____ enzyme
mitochondrial
What is the purpose of the conversion of pyruvate to oxaloacetate
so it can be transported from the mitochondria to the cytoplasm via the malate shuttle
Where is glucose 6-phospatase located
in the lumen of the ER of liver, kidneys, and pancreatic Beta Cells
