Absorptive & Postabsorptive Nutrient Utilization I Flashcards
are digestion and absorption continuous?
NOPE
what are the three phases of fuel metabolism?
absorptive phase
postabsorptive phase
prolonged energy deficiency
list the major fuel of the brain for each phase of fuel metabolism
phase I (absorptive) - glc
phase II (postabsorptive) - glc
phase III - ketones
what fluctuates more dramatically, AA and FA levels or glc levels?
AA and FA
why do glc levels have to be kept within a strict concentration?
basic metabolic fuel
brain uses glc almost exclusively
which 3 metabolic fuels are channeled to depot sites during absorptive phase?
glc
aa
TG/FA
what’s protein mainly used for?
body protein
metabolism if needed
what’s glc mainly used for?
metabolism ASAP
what’s FA mainly used for?
adipose +/- metabolism
what’s the pathway where all fuels are used?
krebs cycle
glc is stored as ___ in liver and muscle during absorptive phase
glycogen
what’s the first step in glc processing?
glycolysis
excess glc can be converted to ____ in liver
FA
nitrogen is transferred to ___ -> alanine
pyruvate
aka transport AA
what’s the major source of blood urea?
liver
do AA get removed from circulation on first of second liver passge?
first
what does the liver selectively remove AA for?
ones that can be used for hepatic protein and plasma protein synthesis or for liver metabolism
most AA can be converted to ___ and ___ synthesis
glc and FA
what’s the storage form of AA?
muscle protein
when does a “net increase” in muscle protein occur?
when synthesis»_space;> breakdown
after liver deamination, keto-analogues are… (3 possibilities)
- metabolized
- enter gluconeogenesis/glycogenesis
- enter FA synthesis
what’s the storage form of FA?
triglycerides
what do pools of FA consist of?
NEFA and glycerol
where are NEFA and TG repackaged?
liver
during postabsorptive phase, what do fat cells release?
glycerol and NEFA
can FA be converted to glc? why?
nope
since decarboxylation of pyruvate to acetyl CoA is irreversible
what’s derived from FA to act as alternative fuel source?
ketone bodies
where can ketone bodies be used during prolonged energy deficiency?
brain and heart
what two things regulate transfer of metabolic fuels into pools during absorptive phase?
insulin
glucagon
in order to reduce circulating glc concentrations, insulin sitm…
glc uptake in liver
glycogen synthesis in liver/muscle
FA synthesis in liver and adipose
protein synthesis in liver/muscle
how is insulin secretion stim?
increased levels of glc in circulation
insulin is secreted by pancreatic __-cells
beta
glucagon is secreted by pancreatic ___-cells
alpha
how is glucagon secretion stim?
low levels of glc and/or high levels of aa
insulin promotes glc uptake by increasing surface exposure of ___ transporters
GLUT 4
insulin stim glycogen synthesis in liver by ____ of glycogensynthase (activated) and by ____ of glycogenphosphatase (inactive)
dephosphorylation for both
describe what happens when glc»_space; aa
describe what happens when glc </= aa
high aa levels stim both ___ and ___ secretion
insulin and glucagon
high glc levels stim mostly ___ secretion
insulin
glucagon is stim by high ___ and low ___ levels
high aa
low glc
what does glucagon stim from aa in order to prevent hypoglycemia?
gluconeogenesis
during the ____ phase, metabolic fuels are channeled to depot sites, and glc is used to maintain metabolism
absorptive
during the ___ phase, metabolic fuels are mobilized from depots
post-absorptive
both a ___-rich diet and the ___ phase are characterized by low glc levels
protein rich
post-absorptive phase
