liver metabolism

Question 1

what types of metabolism are liver cells involved in

carbs and fats

Answer 1

• 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

Question 2

what types of metabolism are liver cells involved in

protiens

vitamins/mainerals

biotransformation

Answer 2

• 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

Question 3

what is cholesterol

Answer 3

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

Question 4

what are the 4 types of lipoproteins

Answer 4

chylomicron (mostly triglycerides) -> largest

VLDL (50% triglucerides)

LDL (half is cholesterol)

HDL (mostly protein ~50%) -> smallest

Question 5

what is role of VLDLs

Answer 5

• 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)

Question 6

function of HLDL

Answer 6

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

Question 7

how do HDL particles work

Answer 7

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

Question 8

impact of HDL and LDL on heart

Answer 8

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

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Question 9

what is apolipoprotein (a)

Answer 9

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

Question 10

summary of lipoproteins

Answer 10

• 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

Question 11

plasma cholesterol level considerations

Answer 11

• 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

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Question 12

why are omega 3 FAs good

Answer 12

powerful antiarrhythmic effect on the heart and make blood platelets less sticky preventing spontaneous clotting

Question 13

how to ARC neurons regulate food intake

Answer 13

• 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

Question 14

what is BMI

Answer 14

formula used to determine obesity based on a person’s weight relative to height

• BMI = wt (lb) × 705/height in (inches)²

Question 15

when is somebody considered overweight

Answer 15

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

Question 16

what is body temp?

what controls heat production and heat loss

Answer 16

• 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

Question 17

core vs shell temp

Answer 17

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

Question 18

what are the 4 mechanisms of heat exchange

Answer 18

• 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

Question 19

role of hypothalamus in temp

Answer 19

* 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

Question 20

heat promoting centers of hypothalamus

(how makes you warmer)

Answer 20

• 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

Question 21

heat loss centers of hypothalamus

(how makes you cooler)

Answer 21

• 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

Question 22

Heat-induced exhaustion:

Answer 22

• 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

Question 23

heat stroke

Answer 23

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