Lecture 4-Role of Fat Flashcards
what dominated a adipocyte
lipid droplet
where are triglycerides stored within adipocytes
triglycerides are stored in lipid droplets within the cytoplasm of adipocytes
what are the other functions of adipocytes
maintains many other cellular functions
produce hormones
how is fat normally stored
triacylglycerol (3 fatty acids and a glycerol)
what can not cross the cell membrane, but fatty acids can
triacylglycerol can not cross cell membranes where as fatty acids can
what breaks down TAG (triacylglycerol)
lipoprotein lipase (LPL) enzyme
what is TAG (triacylglycerol) broken down into
free fatty acids, glycerol is disconnected
how are fatty acids carried in the blood
bound to albumin
what are tissues that lipoprotein lipase is found in
liver
adipocytes
muscle
lactating mammary glands
what are the two forms of lipoprotein lipase
hormone sensitive and hormone insensitive lipoprotein lipase
how are hormones that affect LPL are mediated through what
mediated through signalling pathways typically involving second messengers
what does hormone insenstive lipoprotein lipase provide and what does this mean in adipocytes
a base level of activity in the absence of hormones
adipocytes will continue to release a small amount of fatty acids in the absence of hormones
what will glucagon do to hormone sensitive lipase and what will this do
glucagon will stimulate hormone sensitive lipase
this will start breaking down TAG and release free fatty acids into the circulation
if insulin is present what will be inhibited in terms of fatty acids
inhibit the conversion of triacylglycerol to fatty acids
how is growth hormone different and what will it stimulate
growth hormone is a longer acting hormone (days to months)
it will stimulate the release fatty acids, providing fuels for metabolic activity
how is noradrenaline and adrenaline different to growth hormone and what does it do
much shorter acting, fight or flight
these will override the other settings, adipocytes will release fuel
Diacyl and monoacyl-glycerol have different what
different properties
TAG is broken down in several steps involving …
different enzymes
what are the two things that triacylglycerol is converted to before glycerol
diacylglycerol and monoacylglycerol
during fasting how many days does the body take to produce ketone bodies
1-2 days
what are the two major forms of ketone bodies
acetoacetate
hydroxybutyrate
during fasting what does the brain use to replace some glucose as a fuel
ketone bodies
during long term fasting, ketone bodies will provide the body with how much of the energy that would normally come from glucose
about half
what gives rise to the acetone smell on breath when someone is producing ketone bodies
acetone produced from acetoacetate
what are the precursors of fatty acid synthesis
glucose through glycolysis
amino acids to Oxoacids and Acetyl-CoA
fats are already fats
where is Acetyl CoA produced (fatty acid synthesis)
produced in the mitochondria
where does fatty acid synthesis occur
in the cytosol
what mechanism moves Acetyl CoA into the cytosol for fatty acid synthesis
the citrate shuttle
enzymes associated with synthesising fat are found where
in the cytosol
enzymes associated with breaking down fat are found where
in the mitochondria
what kind of process is fatty acid synthesis
cyclic process
what happens during fatty acid synthesis
2 C are added to the growing chai (starting with Acetyl CoA)
in fatty acid synthesis what is Acetyl CoA converted to
malonyl-CoA (addition of CO2)
what reducing equivalent is involved in fatty acid synthesis
NADHP
what are surplus fatty acids mostly used in
primarily involved in TAG sinthesis
what are surplus fatty acids also used for
other fatty acyl-CoA
phospholipids (important for cell membranes)
specialised lipids
modifications to proteins
what fuel is short term fasting primarily associated with differences
primarily associated with carbohydrate differences, although most tissues use fatty acids for fuel
what parts of the body really need glucose
red blood cells and the brain
when does long term fasting come into play
when fasting extends out over a number of days
during long term fasting, what occurs to liver glycogen and what are the implications of this
liver does not have any glycogen left, so will break down amino acids from proteins
when liver glycogen is depleted, the body will break down proteins, where and in what form will these be transported (then what will happen to them)
broken down proteins most likely in the form of alanine or aspartate will be transported to the liver, and will be used to make glucose which will be used by the brain
in long term fasting what will happen to some fatty acids and what does this mean for fuel use
some fatty acids will be converted to ketone bodies, these can be used by the brain
what are the effects of insulin in muscle
increased glucose uptake
increased glycogen synthesis
what are the effects of insulin in adipose tissue
increased glucose uptake
increased lipogenesis
decreased lipolysis
what are the effects of insulin in the liver
increased glycogen synthesis
increased lipogenesis
decreased gluconeogenesis
what are the effects of glucagon in adipose tissue
increased lipolysis
what are the effects of glucagon in liver
decreased glycogen synthesis
increased glycogenolysis
what are the effects of epinephrine in the liver
decreased glycogen synthesis
increased glycogenolysis
increased gluconeogenesis
