Exam 4 - Integrated Metabolism (STUDY SLIDES) Flashcards
Each organ has unique metabolic needs/functions which must maintain a constant supply of energy and preserving some for future needs.
Noted
Body uses __ and ___ to differentially control biochemical pathways within various organs in response to supply and demand.
nervous system and hormones
Main hormones include ___, ___, ___, ____, and growth hormone (in children).
insulin, glucagon, catecholamines, glucocorticoids
3 major tissues for metabolism include:
liver, adipose & skeletal muscle
The liver actively provides the ___ your body needs.
quick fuel (glucose)
Adipose tissue provides
long-term energy storage.
Skeletal muscle and the rest of your body constantly demand this energy. Brain consumes approximately ___ of glucose/day; 20% of the average diet.
90 g
The supply and demand of energy must be continuously provided via dietary intake or breakdown of stores to balance with the energy requirements of respiration, transport, motility, and synthesis of cells and tissues.
Average adult uses approximately (# of kCal/kg) of energy to insure proper health and to maintain proper weight.
24 kcal/kg
Several key biomolecules link the biochemical pathways for carbohydrates, lipids, and amino acids/proteins and the pathways they funnel into are tightly regulated and tissue specific.
What three are mentioned?
glucose-6-phosphate (G6-P), pyruvate, and acetyl coenzyme A or acetyl-CoA
They link the anabolic and catabolic pathways of carbohydrate metabolism to maintain a constant supply of energy to maintain homeostasis under constantly changing conditions.
Metabolic regulation at G6-P is critical, especially in the liver.
After ingestion of carbs, glucose taken up by liver is converted to G6-P by ___ using 1 ATP molecule, trapping glucose within hepatocytes
glucokinase
G6-P is metabolized in one of three pathways: _____ for energy storage, ____ for ATP production, or the pentose phosphate pathway for _____.
glycogenesis
glycolysis
NADPH and/or ribose’s production.
Pathway depends upon activation of ___ and ___ (enzymes?), substrate availability (G6-P, ATP, and NADP+) & allosteric effectors (ATP, AMP, fructose 2,6-bisphosphate [F2,6BP], hydrogen ions [H+], and [citrate]).
glycogen synthase and phosphofructokinase-1
What substrates are involved in the regulation of the G6P pathway?
G6-P, ATP, and NADP+
What allosteric inhibitors are involved in the G6P pathway?
ATP, AMP, fructose 2,6-bisphosphate [F2,6BP], hydrogen ions [H+], and [citrate]
The key enzymes in glycogenesis and glycolysis are predominantly regulated by (1) ___ and (2) ____ (phosphorylation); whereas the allosteric effectors fine-tune these pathways
hormone-stimulated
covalent modification
Regarding glycolysis and glycogeneiss, covalent modification is more or less synonymous with?
phosphorylation
Pentose phosphate pathway is primarily regulated by the availability of?
G6-P and NADP+
In the well-fed state, increased ATP and citrate, inhibit ____, the committing step of glycolysis (slowing the production of fructose 1,6-bisphosphate), leading to increased G6P
phosphofructokinase-1
stimulates glycogen synthase, leading to the formation of glycogen?
increased G6P
Increased G6P indirectly inhibits _____ thereby inhibiting glycogenolysis (glycogen degradation).
glycogen phosphorylase
Slide 15 for diagram on Glycolysis..
WHat are the key regulatory steps (enzymes)?
Hexokinase/glucokinase
Phosphofructo-kinase
Pyruvate kinase
With increase NADP+ and decreased NADPH, G6-P can be shuttled into the _____ to generate NADPH (reductive energy) used to synthesize a variety of biomolecules such as, fatty acids, cholesterol, nucleotides and other cofactors as needed.
pentose phosphate pathway
What are some biomolecules produced from pentose phosphate pathway?
fatty acids, cholesterol, nucleotides
and other cofactors as needed
With decreased NADP+ and increased NADPH, the pentose pathway (will/will not) operate regardless of the concentration of G6-P.
will not
Don’t confuse Fructose-2,6-Bisphosphate with?
Not the same as fructose-1,6-bisphosphate which represents the committing step to glycolysis
accelerates the synthesis of F-2,6-BP and inhibits its hydrolysis?
Fructose 6-phosphate
Fructose 6-phosphate is catalyzed to F-2,6-BP by?
phosphofructokinase-2
Abundance of fructose-6-phosphate leads to a higher concentration of F-2,6-BP, which in turn stimulates?
phosphofructokinase-1
This is called feed forward stimulation.
Eating breakfast stimulates _____/inhibits glycogen break-down in preparation for the next period of fasting
glycogen synthesis
↑ glucose stimulates beta cells in pancreas to release insulin, increasing absorption of glucose from blood, which dephosphorylates ____ (glycogenesis) and phosphorylates ____ (no glycogenolysis).
glycogen synthase
glycogen phosphorylase
slide 18
What hormone levels lead to ↑ glycogen synthase activity and ↓ glycogen phosphorylase activity?
↑ insulin, ↓ glucagon
After glycogen is replaced, then lipids will be synthesized using excess
carbohydrates.
If cholesterol biosynthesis is active, ____ from fatty acid metabolism can be synthesized into cholesterol.
excess acetyl-CoA
Once lipid biosynthesis commences, utilization of NADPH increases the NADP+/NADPH ratio favoring use of
pentose phosphate pathway.
Glycolysis is also stimulated by increase ___ which activates phosphofructokinase-2.
↑ [F2,6BP]
↓ blood glucose stimulates pancreas to release glucagon, which acts on ___ and stimulates cAMP.
liver G-protein
The cAMP (from the liver G-protein) phosphorylates _____ (no glycogen synthesis) and dephosphorylates glycogen phosphorylase (glycogenolysis)
glycogen synthase
2nd major branch point in metabolism is at ?
pyruvate
Pyruvate can be converted into lactate, ___, oxaloacetate, and/or acetyl-CoA, depending on energy needs.
alanine
What four chemicals can pyruvate be converted to, depending on energy needs?
Lactate
Alanine
Oxaloacetate
Acetyl-CoA
Pyruvate can undergo oxidative decarboxylation to enter __ and ultimately generate ATP when energy levels are low.
CAC
In liver, ___ and ___ can funnel into CAC or gluconeogenesis via pyruvate
Alanine & lactate
During starvation, ____can produce up to 160 g of glucose in a day (half from AA); half of the glucogenic glucose will be used by the brain.
gluconeogenesis
Of the 160 g of glucose maximally produced from gluconeogenesis, how much is from amino acids?
Half
As blood glucose levels stabilize and gluconeogenesis is not required, ____ can re-enter the glycolytic pathway at phosphoenolpyruvate or go back into mitochondria as malate, to enter the Citric Acid Cycle (CAC).
cytosolic oxaloacetate
↓energy inhibits pyruvate dehydrogenase kinase (PDK) (keeping ____ active) meaning that pyruvate is oxidatively decarboxylated to acetyl-CoA.
pyruvate dehydrogenase
If ↑energy, then ↑ [NADH] and [acetyl-CoA] activate ___ (turning off pyruvate dehydrogenase and CAC).
PDK (pyruvate dehydrogenase kinase)
___ and ___ stimulate pyruvate carboxylase, the first step of gluconeogenesis as alternative pathway.
↑ [ATP]
↑ [acetyl-CoA]
If ↓ O2 and anaerobic respiration becomes important, pyruvate can be converted to lactate by lactate dehydrogenase with oxidation of ONE ___ to ___, the latter being essential for sustaining glycolysis.
NADH
NAD+
Recall glycolysis: glucose gives 2 pyruvate + 2 ATP + 2 NADH + 2 H2O + 2 H+
In ___ conditions, ATP is derived solely from glycolysis.
anaerobic
↑ [NADH] stimulates ____ under anaerobic conditions.
lactate dehydrogenase
Also known as the Lactic Acid Cycle.
Cori Cycle
In the liver, ___ can be converted back to glucose for energy production via the Cori cycle.
lactate
When ↑ [lactate] get too high, inhibition blocks further conversion of pyruvate to ___
lactate
___ create the sensation of “burning” in muscles, which serves as a signal to the body to limit further use of these muscles.
↑ [lactate]
In muscle, pyruvate can convert toalanine via
alanine transaminase