Biochem test 2 lesson 2 Flashcards

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absorption - OUTLINE

  • electrochemical gradients
  • enterocytes
    • anatomy
    • glucose transporters
    • aminoacid transporters
    • sugar, amino acid export
    • lipid transporters
    • chylomicron export
  • glucose uptake
    • insulin insensititve
    • insulin sensitive
  • lipid uptake
    • lipoproteins
    • chylomicrons
    • VLDL
    • LDL
    • HDL
    • atherosclerosis


No Q: electrochemical gradients

Extracellular - high [Na+][Cl-]

low [K+]

intracellular - high [K+]

low [Na+][Cl-]


transport pathways


  1. simple
    • net movement hi->lo concentration
    • direct - molecules diffuse thru lipid bilayer
    • channel proteins - proteins allow movement water + solutes


  1. primary - carrier proteins use energy (ATP, hydrolysis, etc.) move molecules across membrane against gradient (pump)
    • Na+-K+ ATPase pump - ATP hydrolysis coupled to transport 3 Na+ out of cell and 2K+ in cell
      • critical for cell volume + for nerves/muscles electric potential + 2ndary transport
    • Ca2+ pump - nerve impulse, muscle contraction
    • H+ pump - pareital cells of gastric glands, kidney
  2. secondary - carrier protein couple favorable reentry of extracellular Na+ to move another molecule across membrane in unfavorable direction (against gradient)
    • sodium co-transport-symporter - Na+ + 2ndary molecule both enter cell (glucose, amino acids)
    • sodium counter-transport - antiporter
      • 2ndary molecule exits the cell (Ca2+, H+)


enterocytes - glucose transporters

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enterocytes - amino acid transporters

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Q: know enterocytes sugar + amino acid export

enterocytes - sugar, amino acid transfer

amino acids + sugars (glucose, fructose, galactose) go into enterocyte + transported out back end + taken up by capillaries + feed into hepatic portal vein

  • small enough to fit thru transporters
  • everything goes to liver
  • ***liver take what glucose it wants -> rest flow past it (galactose + fructose do not pass liver, they should not leave liver, other cells cant deal w galactose and CAN process fructose)
  • glucose/amino acids circulate around body + tissues take up what need
  • capillaries -> hepatic portal vein -> liver -> heart -> lung -> heart -> rest of body


enterocytes - lipid transfer

all things lipid basically from this lesson


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  • all lipids (whether TAG, cholesterol, fat soluble vitamins etc.) taken apart -> put back in cell + reassembled into what they were
  • -> assembled into chylomicron (dont go thru transporter or capillary bc too big)
    • is an oil ball w/ water and soluble proteins holding together (inside had cholesterol + TAG)
  • -> exocytosed -> intersititial fluid around tissue -> lymph vessel -> heart -> body
  • chylomicrons bypass liver by going to lymph + thoracic duct -> heart -> body
  • go down main arteries in body looking for fat/muscle tissue -> stick to it
    • lipoprotein lipase enzyme will unload fatty acids off TAG -> free fatty acids pump into cell + reassemble to make TAG in fat cell
    • chylomicron remnant (glycerol) left over -> go back to liver
  • chylomicron remnant get back to liver -> make VLDL -> blood -> the TAG taken up again by muscle / fat = LDL
  • KNOW LDL is reservoir of cholesterol - steady amount always in blood = majority of cholesterol in blood (high LDL is bad bc susceptible to oxidation)
  • HDL - lipoprotein cleans tissue


Q: Know amino/sugars path vs lipids

  • sugars + amino acids go thru hepatic portal vein -> liver -> rest of body/circulation
  • lipids in chylomicron go thru thoracic duct -> heart -> body (BYPASS LIVER)


glucose uptake - insulin insensitive

all tissues in body by default have insulin independent facilitative transport (means if glucose in blood, go into tissue as needed, no power needed)

  • galactose + fructose -> liver hold all of it (stay there)
  • liver take any glucose need + then flows thru
  • 2 types transport
    • facilitative - glucose transporter. if hi [glucose] outside -> go in
      • brain, liver, blood cells, eye lens + cornea
      • glucose in blood cont. feed these cells . constant glucose never stops bc keep within threshold
    • active transporter - Na+ dependent
      • intestine - enterocyte
      • kidney - renal tubes (reabsorb glucose into blood from urine + pump back in blood)
        • need active transporter bc if not would urinate glucose in blood if not.
  • glucose in blood go into blood as needed = facilitative transport needed
  • intestine + kidney -> sodium dependent glucose transporters (SGLTs)
    • in intestine bc wanna absorb all can
    • in kidney bc it filters out + reabsorbs what wants to keep\

eat -> glucose in blood (reducing sugar) -> react w blood vessels -> wreck things -> blood vessels deteriorate -> loose blood supply there

= why need certain level glucose so can get in all tissues and stay within threshold


Q: know where glucose need to completely be moved 1 place -> another

  • intestine
    • so take up all glucose can, no wasting
  • kidney
    • bc filters from blood + reabsorbs what wants to keep (reabsorb glucose into blood from urine)

= sodium dependent glucose transporters (SGLTs)

everywhere else = facilitative transport (GLUT, glucose transporter)



  • secreted by pancreas + tells fat/muscle to take up glucose (protect circulatory system)
  • lot of glucose in blood (glucose is reducing sugar, react with things)
  • sugar in blood in arteries/capillaries
  • high glucose level over time -> damage circulatory system -> loose blood supply to tissue = tissue dies

ex: ppl w/ diabetes have high glucose in circulatory system -> damage system -> lose blood supply to tissue -> dies


Q: insulin dependent glucose transporters are in what tissue?

cardiac (muscle)

skeletal (muscle)

adipose tissue (fat)

all these

if see all 3 = all of above


glucose uptake - insulin sensititve

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  • insulin tell muscle/fat to take up glucose (to protect circulatory system)
  • muscle and fat (regulated by insulin)
    • facilitative transport
  • eat -> blood glucose inc -> bind to muscle + fat
  • insulin receptor on cell membrane = stimulate muscle + fat to put glucose transporters on surface (mediated by insulin)
  • -> take up glucose until come to level
    • stop when insulin lvls decrease -> transporters move from membrane
  • muscle store glucose as glycogen, fat store it as fat


Q: insulin regulated glucose receptors: where are they?

cardiac+skeletal muscle (not smooth) and fat (adipose tissue)


lipid - chylomicron

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  • lipid bypass liver -> heart -> body (blood vessels)
  • chylomicron (big) - deck on fat + muscle -> suck TAG from chylomicron -> reduce chylomicron using lipoprotein lipase
  • reduced/remnant sucked dry
    • has cholesterol
    • circulate back to liver -> recycled
  • liver take excess glucose / fructose -> make fatty acids
    • also build up fat -> make VLDLs (very low density lipoproteins) = full of TAGs from xs sugars in liver
  • VLDL -> circulation -> fat/muscle cell -> unload TAGs -> now LDL (low density lipoprotein)
  • LDL carry most cholesterol in body
    • circulates body
    • if anything need cholesterol -> LDL receptors surface -> bind LDL -> internalize -> obtain cholesterol


lipid - VLDL

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  • liver take excess glucose / fructose -> make fatty acids
    • also build up fat -> make VLDLs (very low density lipoproteins) = full of TAGs from xs sugars in liver


lipid - LDL

  • VLDL -> circulation -> fat/muscle cell -> unload TAGs -> now LDL (low density lipoprotein)
  • LDL carry most cholesterol in body
    • circulates body
    • if anything need cholesterol -> LDL receptors surface -> bind LDL -> internalize -> obtain cholesterol


Q: when chylomicron dock on muscle / fat surface -> lipoprotein lipase...

  • lipoprotein lipase go in chylomicron -> take TAGs + hydrolyze off free fatty acids
  • -> pumped in cell
  • -> conjugated to COA + fatty acids reassemble to make TAG in fat cell
  • glycerol stays in blood -> go back to liver
    • liver keeps glycerol


Q: doctor ask you to fast for your labs (dont eat so can measure fasting glucose, etc.) what is the majority of cholesterol found in blood?

majority of cholesterol is LDL and HDL



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  • high density lipoprotein - roll around tissue + clean up excess cholesterol from tissue membrane
  • gets cholesterol to liver -> use as bile in digestion, etc.
  • total cholesterol mainly HDL and LDL
  • 1:3 to 1:5 ratio HDL:LDL is safe
  • if higher LDL = dangerous


lipid uptake - atherosclerosis

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  • LDL swimming in body are more susceptible to oxidative damage
  • ROS in heart bc its pumping = burns ATP so needs Oxygen to drive ATP synthesis
    • oxygen reduced -> water drive ATP synth -> become superoxide, H2O2, hydroxylradical -> intermediates leak ROS
    • LDL circulate heart susceptible
      • damage, open up, spill
      • -> contents get on capillary walls feeding blood supply
      • -> immune cells (WBC) think damage occured -> macrophages eat oxidized lypoprotein content
      • -> become foam cells
      • -> accumulate + release growth factors/cytokines stimulate smooth muscle cell migration + proliferate + take up lipid and become foam cells as well
      • foam cells dry out on artery walls
      • -> artherosclerosis (hardening arteries)


more artherosclerosis

  • heart attack
    • blood clots in artery
    • -> loose blood supply to heart
    • = cant make ATP
    • = stops beating
    • = heart attack
  • stroke
    • blood clot in brain
  • pulmonary embolism
    • blood clot in lung
  • thrombosis
    • blood clot in leg

all these = cardiovascular disease

= why watch cholesterol produced by body (LDL)


Q: know

fasting blood -> majority cholesterol is in LDL

high LDL causes artherosclerosis (cardiovascular disease) bc its susceptible to oxidative damage

  • and once damaged -> the whole process starts



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