Glycolysis Flashcards
Catabolic pathways
Breakdown pathways
Free energy released during conversion of larger fuel molecules to smaller molecules that are converted to Acetyl CoA and enter Kreb’s
. ATP is ultimate product
Anabolic pathway
. Free energy consumed when smaller molecules make larger molecules
. CONSUME ATP
Where does regulation most often occur in pathways?
Irreversible steps
Where does regulation by covalent modification occur?
. Key steps in pathway
. “committed” step
. Regulated in response to endocrine hormones
How are pathways regulated by availability of substrate
. Limitations by metabolism
. Limitations by transport
Epinephrine
. Released from adrenal glands
. Acts on many tissues
. Induced cAMP cascade activity PKA phosphorylating enzymes in metabolism
Glucogon
. Released from alpha cells of pancreas in response to LOW blood glucose
. Binds to liver receptors mostly and some adipose
. Induces cAMP cascade
Insulin
. Released from beta cells of pancreas in response to HIGH blood glucose
. Acts on all cells
. Opposes epinephrine and glucagon
Glycolysis
. glucose (6C) Converts to 2 molecules of pyruvate (3C) w/ generation of ATP
. Operates aerobically or anaerobically
Catabolic and anabolic purposes of pathway
C: atp production
A: provides basic building blocks for cellular biosynthesis
Glycolysis net rxn
Glucose + 2Pi + 2ADP+ 2NAD -> 2 pyruvate + 2ATP + 2NADH + 2H + 2H2O
Glycolysis w/ oxygen
Pyruvate converts to acetylene CoA then to Kreb’s
Glycolysis if not enough oxygen
. Pyruvate converts to lactic acid via lactate dehydrogenase
. Regenerates NAD from NADH to pathway can continue
Fate of NADH in aerobic conditions
. NADH converted to NAD to cross membrane into mitochondria
NADH shuttle system
. Enable reducing equivalents from NADH to be transported into mitochondria to be used in ETC
Difference btw glycerol 3 phosphate shuttle and malate aspartame shuttle
. Glycerol 3 phosphate uses FAD instead of NAD and yields less energy overall
Total ATP from aerobic oxidation of 1 glucose
30-32 ATP
Total ATP from anaerobic oxidation from 1 glucose molecule
2 ATP
What happens to lactic acid that accumulates in muscle tissue after anaerobic metabolism?
. Travels to liver in blood
. Converted back to pyruvate for gluconeogenesis (making glucose from other molecules in body)
. Resulting glucose sent back to muscle to be used
Accumulation of lactic acid can result in ____
Serum acidosis
Irreversible steps in glycolysis
. Hexokinase/glucokinase
. Phosphofructokinase
. Pyruvate kinase
What does adding phosphate to glucose do?
Traps glucose in the cell
Hexokinase location, Vmax, and Km for glucose
. Whole human body cytosol, NOT induced by inc. glucose
. Vmax low
. Km: 0.1 mM
Glucokinase location, Vmax and Km for glucose
. Liver, pancreas beta cell cytosol, IS INDUCED by inc. glucose
. Vmax high
. Km: 10 mM
When is hexokinase and glucokinase used?
. Hexokinase full time
. Glucokinase part time after meals when glucose levels are high
Committed step in glycolysis
Fructose-6P -> fructose 1,6=bispohosphate via PFK-1
Positive and negative effectors of PFK-1
. Pos: AMP
. Neg: ATP, citrate, low pH
Allosteric regulation of liver pyruvate kinase
. Activated by fructose 1,6-bisphosphate
. Feed forward regulation
When F-2,6-BP is present, glycolysis is turned ____
On, when absent it is off
Components of protein that emulates F-2,6-BP
. Phosphofructokinase-2 (PFK-2) is dephosphrylated
. Fructose bisphosphatase 2 domain (FBPase-2) is phosphorylated
. When one side is active the their side is degraded through phosphorylation/dephosphorylation
What happens to glycolysis when insulin binds to receptor on liver cell?
. RTK results in glycolysis pathway proteins being depohsphorylated
. PFK-2 turns on and F-2,6-BP is made and activated PFK-1 to turn on glycolysis
. Pyruvate kinase is dephosphorylated and turned on to continue glycolytic pathway
Anabolism is promoted by what hormone?
Insulin
What happens to glycolysis when epinephrine binds to receptor to liver cell?
. PKA phosphorylated pyruvate kinase turning it off and phosphorylated FBP-ase-2 turning it on
. F-2,6-BP is degraded and glycolysis shuts down
. Pyruvate kinase also turned off
Liver cell glycolysis is ___ by epinephrine but muscle glycolysis ____ w/ epinephrine
. Dec
. Inc.
T/F Liver is NOT homogenous and some cells will be running glycolysis while other aren’t
T
Periportal hepatocytes
. Closest to blood supply
. Receive highest [O2] and other nutrients
. Oxidative metabolism favored
. Perivenous hepatocytes
. Cells farther away from blood supply
. Receive much less O2 and other nutrients
. Depend more on anaerobic glycolysis for ATP synthesis
Liver role
. Primary biochemical role to supply rest of body w/ blood-born source of fuel
. Releases glucose from gluconeogenesis or other molecules (fat, ketones)
Regulation of glycolysis in liver guided by____
. Substrate availability
. Receptors for insulin, epinephrine, and glucogon
Muscle role
. Role of muscle is to move
. Primarily consumer
Regulation of muscle guided by ____
. Substrate availability
. Allosteric regulation
. If muscle is moving or at rest
. Receptors for insulin and epinephrine (NO GLUCAGON)
