Exam - Metabolic Integration Flashcards
what must metabolic integration maintain
blood glucose between 60-100mg/dL
what happens if blood glucose is < 60 mg/dL
development of a coma and can be fatal
why is blood glucose required by red blood cells
as an energy substrate because they have no mitochondria
what is blood glucose required by
red blood cells
central nervous system
to maintain an active krebs cycle
in the fed state, what is the predominant source of blood glucose
dietary CHO
dietary protein
in the post-absorptive state, what is the predominant source of blood glucose
glycogen from liver (glycogenolysis)
in the fasting state, what is the predominant source of blood glucose
gluconeogenesis from protein catabolism
in the starvation state, what is the predominant source of blood glucose
gluconeogenesis from glycerol produced by TAG breakdown
some protein catabolism
4 main hormones for metabolism regulation
insulin
glucagon
corticosteroids (cortisol)
catecholamines (epinephrine)
what is the nature of insulin
anabolic
what is the nature of glucogon
catabolic
what is the nature of corticosteroids
catabolic
what is the nature of catecholamines
catabolic
what is insulin produced by
B-cells in pancreas
what is glucagon produced by
a-cells in pancreas
what is corticosteroids produced by
adrenal cortex
what are catecholamines produced by
adrenal medulla
what are the main effects of insulin
increases glucose and AA uptake in muscle and liver
increases glycogen and protein synthesis in muscle and liver
increases TAG synthesis and storage in adipose
what are the main effects of glucagon
increased breakdown of glycogen, protein and fat
increased gluconeogenesis from AAs and glycerol
what are the main effects of corticosteroids
increases protein catabolism
increases gluconeogenesis from AAs
what are the main effects of catecholamines
increases glycogenolysis and lipolysis
what are T3 (T4) hormones
tyrosine-based hormones produced by thyroid that affect metabolic rate
what does the brain have a high requirement for
oxidative metabolism to suppor continuous electrical activity
what does the brain depend on
glucose
how many g of glucose is required by the brain per day
100-120
why does the brain depend on glucose as opposed to other energy sources
fatty acids cannot cross the blood-brain barrier enough to provide sufficient energy
how much glucose does the liver produce during an overnight fast
2mg/min/kg body weight
how much of the glucose produced by liver in overnight fast is consumed by the brain
half
what is the main purpose of the liver
regulating
what does the liver regulate
blood glucose levels
what is the liver a major site for
fatty acid B-oxidation
what is the only tissue to produce ketone bodies
liver
what kind of energy requirements does adipose tissue have
low - not a lot of oxidative fuel consumption
when is glucose used in adipose tissue
for de novo lipogenesis
TAG synthesis
provide energy for fatty acid uptake
what does adipose tissue release into circulation
non-esterified fatty acids from lipolysis
can non-esterified fatty acids be metabolic fuel
yes - depending on circumstances
what are non-esterified fatty acids the same as
free fatty acids
what percentage of body weight does skeletal muscle represent
40%
what are the main regulators for muscle fuel consumption
nutritional status and exercise
2 fibres in skeletal muscle
slow twitch
fast twitch
when are slow twitch muscle fibres used
long duration activities - slow contraction
what is the predominant source of energy for slow twitch skeletal muscle fibres
fatty acids
when are fast twitch muscle fibres used
short duration activities - fast contraction
what provides energy for fast twitch muscle fibres
local glycogen stores
what type of glucose is used quickly
precious
how long are glycogen stores sufficient for
24 hours
when does protein breakdown occur
initially - releases glycogenic amino acids which slows down to preserve protein function
why does fatty acid breakdown occur
to spare protein - eventually used to make ketone bodies
how long does the fed state last
0-2 hours after eating
what is the only hormone in the body that lowers blood sugar
insulin
what are the percentages of urea and NH4+ during the fed state
90% urea
10% NH4+
what is promoted in liver and muscle during fed state
glucose uptake and glycogen formation
what is the primary hormone in the fed state
insulin
what occurs in adipose tissue in the fed state
TAG synthesis - long term energy storage
what occurs in the liver during the fed state
clears blood glucose (for glycogen or TAG production)
urea cycle active
what occurs in muscle during the fed state
protein synthesis (BCAA) replenish glycogen reserve
what is the primary hormone in the post-absorptive state
glucagon
what occurs in the adipose tissue in the post-absorptive state
nothing
what occurs in the liver in the post-absorptive state
glycogen breakdown
urea cycle active
what occurs in the muscle in the post-absorptive state
glycogen breakdown
protein catabolism
when is the post absorptive state
3-18 hour after eating
urea vs NH4+ during post absorptive state
still mainly urea
what is the primary hormones in the fasted state
corticosteroids and glucagon
what occurs in the adipose tissue during the fasted state
TAG start to become lipolysed (releasing free fatty acids and glycerol)
what occurs in the liver during the fasted state
produces and secretes glucose via gluconeogenesis; urea cycle activity reduced
what occurs in the muscle during the fasted state
protein catabolism
urea vs NH4+ in fasted state
decrease of urea and increase of NH4+
when does the fasted state occur
18-48 hours with no food intake
what are the primary hormones during starvation
catecholamines and glucagon
what occurs in the adipose tissue during starvation
TAG lipolysis
what occurs in the liver during starvation
ketone production
glycerol backbone of TAG used to make glucose
urea cycle is minimally active
what occurs in the muscle during starvation
muscle protects its protein
still some protein catabolism happening to support blood glucose but not a lot
how long does it take for it to be considered starvation
about 2 weeks
urea vs NH4+ during starvation
10% urea
90% NH4+
