liver metabolism Flashcards
what types of metabolism are liver cells involved in
carbs and fats
- carboyhydrate metabolism
- conc galactose % fructose -> glucose
- gluconeogenesis
- conv gluose -> fats for storage
- Fat metabolism
- primary site of beta oxication
- produces ketone bodies
- stores fats
- forms lipoporteins
- synthesizes cholesterol
what types of metabolism are liver cells involved in
protiens
vitamins/mainerals
biotransformation
- protein metabolism
- demainates amino acids
- forms urea
- forms most plasma proteins
- transamination
- Vitamin/mineral storage
- stores vit A, D, B12 and iron
- Bio transformation
- metabolism of drugs and alc
- processes billirubin
what is cholesterol
0 structural bases of bile salts, steorid hormones and vitamind B
- also major part of plasma membranes
- 15% of blood cholesterol from diet, rest is made from acetyl CoA
- Cholesterol is lost from the body when secreted as bile salts
- insoluble in water and must eb transported bound to lipid-protein complexes called lipoproteins
what are the 4 types of lipoproteins
chylomicron (mostly triglycerides) -> largest
VLDL (50% triglucerides)
LDL (half is cholesterol)
HDL (mostly protein ~50%) -> smallest
what is role of VLDLs
- liver is the primary source of VLDLs, transprot TF from liver -> peripheral tissue
- once TG are unloaded, VLDL converted to LDLs which are cholesterol-rich
*The role of the LDLs is to transport cholesterol to peripheral tissues
- get reduction in HMG-coa reductase, dec in LDL receptors in inc in ACAT (req for cholesterol storage)
function of HLDL
HDLs is to scoop up and transport excess cholesterol from peripheral tissues to liver
- High HLDL god bc transported cholesterol is destined to degredation
*high LDL bad
*Cholesterol >200 mg/100 ml linked to risk of atherosclerosis, clogged arteries, strokes and heart attacks
how do HDL particles work
Liver makes the protein envelopes of the HDL particles -> ejects them into blood in collapsed form
- HDL fills with cholesterol picked up from tissue cels and pulls from artery walls
- bring cholesterol to steroid progucing oragans that can selectively remove cholesterol from the HDL particles without engulfing them
impact of HDL and LDL on heart
HDL levels > 60 mg/100 ml protect against heart disease
LDL levels > 130mg/100ml can lead to potentially lethal cholesterol deposits in the artery walls
* HDL levels can’t be too high and LDL levels can’t be too low
-
what is apolipoprotein (a)
bas type of LDL
- promotes plaque formation, thickens and stiffens blood vessel walls
- high elvels double the risk of heart attach before age of 55
- 1/5 males has elevated apolipoprotein
summary of lipoproteins
- chylomicrons
- imp for tranport of lipids, triglycerides and cholesterol
- tranport free FA to tissues, when empty it then taken up by liver for removal vrom blood stream
- liver produces VLDL -> release of FFA to muscle and adipose
- HDLs released from liver in percuror format
plasma cholesterol level considerations
- high cholesterol intake inhibits its synthesis by liver but not in a one-to-one relationship
- saturated and unsaturated FA in diet have an important effect on cholesterol levels
- > saturated FAs stimulate liver syn of cholesterol and inhibit excretion
- > unsaturated (mono and poly unsat) FAs in olive oil and veg oils enhance excretion fo cholesterol and conv to bile salts
=> hydrogenation of good oils conv to trans Fas, inc LDLs and dec HDLs
- Unsaturated omega 3 FAs in cold water fish, lower proportions of both saturated fats and cholesterol
-
why are omega 3 FAs good
powerful antiarrhythmic effect on the heart and make blood platelets less sticky preventing spontaneous clotting
how to ARC neurons regulate food intake
- NPY/AgR neurons
- release neuropeptide Y (NPY) and agouti-related peptide (AgRP)
- enhance appetite while reducing metabolism
- POMC/CART neurons
- release pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART)
- iappetite supressing
what is BMI
formula used to determine obesity based on a person’s weight relative to height
- BMI = wt (lb) × 705/height in (inches)2
when is somebody considered overweight
overweight if BMI is 25 to 30 and obese if BMI is greater than 30
- Obese people have higher incidence of atherosclerosis, type 2 diabetes mellitus, hypertension, heart disease, and osteoarthritis
what is body temp?
what controls heat production and heat loss
- At rest, liver, heart, brain, and endocrine organs account for most of the heat production
- During exercise, heat production from skeletal muscles can increase 30-40 times
- 37±0.5°C (98.6°F) which is optimal for enzyme activity
Heat production by: basal emtabolism, muscular activity (shivering), thyroxine and epi,
heat loss: radation, evapraton, conduction.convection
core vs shell temp
core: skull, thoracic, and abdominal cavities have the highest temperature
Shell: essentially the skin, has the lowest tempearture
* Blood serves as the major agent of heat transfer between the core and shell
*core temp remains relatively constant, shell fluctues substantially
what are the 4 mechanisms of heat exchange
- Radiation: ehat loss in form of infrared waves (theraml energy)
- conduction: transfer of heat by direct contact
- convection: warm air expands and rises, cool air falls bc denser
- warmed air envolved body is continually being replaced by cooler air mol
- Evaporation
- inseible heat loss: evap of water from lungs, moung and skin (10% heat loss)
- sensible heat loss: sweating inc evaporation heat loss
role of hypothalamus in temp
* in Preoptic area and posterior hypothalamus
- hypothalamus gets input from peripheral thermoreceptors (in shell aka skin), and central thermoreceptos (in body core
- sends impulses to do heat promoting or loss activities
- central thermoreceptors play more critical role but inputs from shell alert hypothalamus of need to do temp changes
heat promoting centers of hypothalamus
(how makes you warmer)
- Vasoconstriction
- ctivation of the sympathetic vasoconstrictor fibers of the blood vessels of the skin causes strong vasoconstriction
- Non shivering thermogenesis
- cold stim release of epinephrine and NE elevating metabolic rate
- shivering
- involuntary shuddering contractions
- Thyroid hormone
- if temp decreases gradually TH increases metabolic rate
heat loss centers of hypothalamus
(how makes you cooler)
- Dilation of cutaneous blood vessels
- vessels of skin dilate
- sweating
- >33C activates sweat glands and evap of sweat
- efficient method for heat loss if air is dry
- voluntary measures
- reducing activity, go to cooler env
- ear light colours and loos fitting clothing
Heat-induced exhaustion:
- type of hyperthermia
- heat-associated collapse during or following vigorous physical activity accompanied by extreme sweating
- Mental confusion and/or fainting is due todehydration and low blood pressure
- Can rapidly progress to heat stroke if the body is not cooled and rehydrated
heat stroke
type of hyperthermia
- Normal heat-loss processes becoming ineffective
- core temp inc to 40.6 C, heat cotnrol mechs are suspended
- increases in body temperatures increase the metabolic rate
- skin beocmes hot and dry
- As the temperature spirals upward, multiple organ damage and death can occur
