Carbohydrate Metabolism Flashcards
what hormones lead the anabolic state
insulin
what hormones lead the catabolic state
epinephrine and glucagon
what happens during the catabolic state
glucagon and epinephrine signal for the breakdown of glycogen leading to ATP production or release of glucose from the liver
what is glycolysis
this is the conversion of glucose to pyruvate used to generate ATP.
it is a catabolic pathway
what is stage 1 of glycolysis
2 ATP are used to prepare glucose for its breakdown of glucose and conversion into two GAPs (glyceraldehyde phosphate- 3 carbon molecule)
what is stage 2 of glycolysis
production of 2 pyruvates, 2 NADH and a net of 2 ATP molecules
After the production of pyruvate in glycolysis what can it be further used for?
it can be oxidized in the mitochondria to generate more NADH
is the glycolytic pathway ender or exergonic
exergonic because it releases energy
in the glycolytic pathway what is fructose converted into
GAP and DHAP
what is galactose converted into
glucose 6 phosphate
what does a negative delta G symbolize
an irreversible reaction
what are the three regulatory steps of glycolysis?
what is about these specific steps make them highly regulated?
steps 1, 3 and 10 are highly regulated steps in glycolysis and this is because they have very negative delta Gs indicating irreversibility
describe the three regulatory steps in glycolysis
step 1: glucose to glucose 6 phosphate by hexokinase. hexokinase can be inhibited by a build up of glucose 6 phosphate
Step 3: fructose 6 phosphate to fructose 16 bisphosphate by phosphofructokinase 1 (PFK-1) can be inhibited by high ATP and citrate present or activated by AMP/ADP or fructose 2-6 bisphosphate
Step 10: pyruvate kinase generating pyruvate can be inhibited by phosphorylation (PTM) and allosteric regulators
what is glucose 6 phosphate used for in the cell
generate energy
stored as glycogen for later
used to make new molecules
what inhibits phosphofructokinase 1 (PFK 1)? What activates it
inhibited allosterically by ATP or citrate
activated by AMP/ADP and fructose 26 bisphosphate
describe the structure of phosphofructokinase and how does this contribute to its allosteric regulation
PFK1 has 2 binding sites, an active site and an allosteric site
ATP binds to its allosteric site inhibiting PFK1 and AMP/ADP binding stimulates PFK1
when pyruvate kinase is phosphorylated, is it more or less activated?
less active.
what amino acid can we derive pyruvate from?
alanine
what enzyme converts alanine to pyruvate
alanine aminotransferase
Fill in the blank.
Allosteric Regulation is dependent on _____
structural changes
what happens to the excess glucose when glycolysis is inhibited?
it can be stored as glycogen in the liver and muscle cells
what converts glucose to glycogen in glycogen synthesis (glycogenesis)
glycogen synthase
in the anabolic pathway, when glucose is high what exactly happens to it as it gets converted to glycogen
glucose is still phosphorylated however it is quickly isomerized by phosphoglucomutase to form glucose 1 phosphate
glucose 1 phosphate is transformed into UDP glucose by UDP glucose phosphorylase
glucose synthase requires the active form of glucose (UDP glucose) to frm new alpha 1,4 glycosidic bonds on the non reducing end of the glycogen
how does insulin activate glycogen synthase
via dephosphorylation
in glycogenolysis (glycogen breakdown) how does epinephrine and glucagon lead to in the inactivation of glycogen synthase
via phosphorylation of glycogen phosphorylase and inactivation of glycogen synthase
what is happening in the liver cells as glucose levels drop and glucagon rises
it will release glucose to help stabilize the glucose levels
Fill in the blank.
Glycogenolysis is a __________ reaction
phosphorolysis using P to release glucose 1 phosphate from non reducing end
what inhibits glycogen phosphorylase? what activates it?
inhibited by ATP and glucose 6 phosphate
activated by AMP
why can’t glucose leave muscle cells like they do in liver cells
because they are missing the phosphatase enzyme
