introduction to lipids Flashcards
how is energy stored long term?
as large, stable, efficient energy precursors
how is energy stored when the lipid of stored ATP is reached?
stored intracell as creatin phosphate
how are carbohydrates used as energy?
- starch is digested into glucose in gut
- glucose is absorbed from gut into blood stream
- glucose absorbed by liver and stored as glycogen via hepatic portal vein
- glucose stored throughout the body as glycogen
- later when more energy is needed glycogen is broken down into glucose
what energy resource does the brain need?
glucose or ketone bodies from plasma constantly
what does fatty acid synthesis do?
leads to fatty acids with even number of carbons and consumes ATP
what does beta oxidation lead do?
fat mobilisation - shortens fatty acid by 2 carbons at a time and produces ATP and acetyl-coA
how many carbons long are most fatty acids in humans?
16-20 carbons long
what is a fatty acid called if it has one double bond?
monounsaturated
what is a fatty acid called if it had 2 or more double bonds?
polyunsaturated
what is cholesterol?
a precursor of bile acids, steroid hormones & vitamin D
what makes cholesterol very rigid?
it’s ring structure
where do we get cholesterol from?
diet or it is made in the liver
what percentage or cholesterol is esterified?
75%
what is cholesterol broken down by and what is it broken into?
broken down by lipases into free cholesterol and fatty acids
why is cholesterol amphipathic?
the free alcohol is hydrophobic when esterified
name 4 steroids
- cholesterol
- vitamin D
- cortisol
- testosterone
what is acetyl-coenzyme A?
main energy production precursor
what are ketone bodies?
3 soluble chemicals made from acetyl-CoA during fasting
what is a waste product of ketone bodies?
acetone is always a waste product
why do unsaturated chains have a lower melting point?
as they are more liquid at body temperature so increase the fluidity of the cell membrane
what are the most naturally occurring unsaturated fatty acids?
Cis
which types of unsaturated fats are bad?
trans
what can cis unsaturated fats be?
- monounsaturated
- polyunsaturated
why do cis unsaturated fats have a lower melting point?
due to the kink
what are the 4 ways of lipid transport?
- from gut to liver and periphery
- from liver to periphery
- from periphery to liver
- from liver into digestive tract
what is the exogenous pathway?
- from gut to liver
- exogenous = lipid from diet
- lipids from diet packaged by small intestine into “chylomicrons”
- chylomicrons taken up by liver
what is the endogenous pathway?
- from liver to periphery
- endogenous = made by body
- lipid from liver packaged into VLDL
what is reverse cholesterol transport?
- from periphery to liver
- occurs when lipid supplies in liver are being exhausted
- HDL in blood indicated reverse path activity
how does lipoprotein work?
- metabolises TG –> fatty acids + glycerol
- cause TG cannot go through cell membrane
- cell surface-linked enzyme in capillary walls
- in order to remove triglycerides from VLDL and to move the TG across the capillary membrane, TG must be metabolised via lipoprotein lipase
what are lipoprotein particles?
- lipids are not soluble in plasma so they must be packaged to be transported
- lipoprotein particles in plasma are soluble and can carry lipids
- apolipoproteins are proteins in LP particles that can hold lipids
why are lipoproteins lower in density?
they usually carry lots of lipids
what is the list dangerous lipoprotein?
low density lipoproteins
how do low density lipoproteins work?
- LDL get incorporated into atheromas
- LDL in blood may be storage for cholesterol that cannot be stored elsewhere
- excess LDL accumulates in atheromas
- LDL is eventually left over after periphery absorbs endogenous TG from VLDL from liver
what is the good lipoprotein?
high density lipoprotein
how does the high density lipoprotein work?
- increased HDL lowers CV risk
- HDL: lipid transport from fat cells to liver called reverse cholesterol transport and appears when cholesterol is being used up
how to very low density lipoproteins work?
- signifies a risk of atheroma
- used to transport endogenous cholesterol and TG from liver to adipose and muscle
- after TG is removed by periphery from VLDL leaves over IDL
what is IDL?
- intermediate density lipoprotein
- results from VLDL losing TG to periphery
- IDL will become LDL
- is a sign of CV risk
what is chylomicron?
it carries lipids from gut to periphery for exogenous lipids and they aren’t usually associated with CV risk
what cells release insulin?
beta cells
what cells release glucagon?
alpha cells
what are the signalling errors of diabetes?
- type 1 diabetes: no insulin made
- type 2 diabetes: absent or decreased response to insulin by target cells
what is type 2 diabetes mellitus?
- also called adult onset diabetes
- high blood glucose: poor plasma glucose control
- insulin resistance
- relative insulin deficiency
- cause: obesity and genetic predisposition
what is hypercholesterolsemia?
- high fasting levels of plasma cholesterol
- increased risk of atherosclerosis
- due to combination of environmental and genetic factors
what are statins?
drugs used to treat hypercholesterolaemia
how do statins work?
block endogenous cholesterol synthesis by blocking HMG-CoA reductase: the entry step into cholesterol synthesis
what is an example of a statin?
simvastatin prescribed for CAD prophylaxis
what is metabolic syndrome?
a group of risk factors that occur together leading to increased risk for CAD, stoke and type 2 diabetes
what are the main causes of metabolic syndrome?
insulin resistance, central obesity (waist circumference)
