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Physiology 2 > 2. GI Part 6 > Flashcards

2. GI Part 6 Flashcards

1
Q

where does 85% of water absorption take place

A

small intestine
55% in jejunum, 30% in ileum

14% in large intestine

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2
Q

requisites for an efficient absorption (4)

A
  1. increasing resorption surface
  2. mucosa uptake mechanisms
  3. high blood perfusion
  4. permeability
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3
Q

why is Na transport efficient

A

it represents the driving force for most transport processes

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4
Q

how is Cl absorbed

A

by carriers as well as passive through paracellular pathway

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5
Q

how is K absorbed

A

in small intestine through paracellular pathway

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6
Q

what does calcitriol stimulate (3)

A
  1. opening of apical membrane Ca channels
  2. synthesis of calbindin
  3. increase in Ca ATPase
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7
Q

how is Mg absorbed

A

through Mg channels and paracellularly

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8
Q

how is P absorbed

A

through Na/phosphate symporter

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9
Q

what is calbindin and what does it do

A

it is a calcium binding proteins that takes Ca to the basolateral membrane

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10
Q

describe the absorption of vitamin B12 (5 steps)

A
  1. vitamin B12 binds to HC
  2. Trypsin removes vitamin B12 from HC
  3. vitamin B12 binds to IF
  4. receptor separates vitamin B12 and IF
  5. IF gets recycles and vitamin B12 goes into blood
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11
Q

what is HC and what does it do

A

HC – haptocorrin, aka transcobalamin I

protects vitamin B12 from stomach acid

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12
Q

what is IF and why is it important

A

IF - intrinsic factor

the component in the stomach that is needed for vitamin B12 absorption

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13
Q

describe absorption of iron in the small intestine (2)

A
  1. Fe3+ cannot be absorbed –> ferrireductase changes it to Fe2+
  2. ferroportin sends Fe2+ to blood, but it needs to be oxidized to Fe3+ in order for it to be bound to apotransferrin to then change apotransferrin to transferrin
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14
Q

describe absorption of vitamins in the small intestine (3)

A
  1. carrier protein that takes up Vitamin Bs (B1, B2, B6)
  2. sodium co-transporter (secondary active transport) –> vitamin C, biotin
  3. cotransport with proteins –> folic acid
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15
Q

define catabolic pathways

A

energy capture (ATP) as a result of degradation of energy rich molecules

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16
Q

define anabolic pathways

what does it require

A

combine small molecules (amino acids) to form more complex molecules (proteins)

requires energy (ATP –> ADP) and often chemical reductions (NADH)

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17
Q

what are different energy sources in living organisms (5)

A
  1. glucose
  2. fatty acids
  3. amino acids
  4. ketone bodies
  5. volatile fatty acids
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18
Q

what are the 3 phases of energy metabolism

A
  1. absorptive phase
  2. post-absorptive phase
  3. prolonged energy deficiency
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19
Q

when does the absorptive phase of energy metabolism take place

A

during active digestion and absorption of nutrients from the gut

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20
Q

what happens during the absorptive phase of energy metabolism (4)

A
  1. insulin is released
  2. glucose is taken up by the liver and converted to glycogen and fatty acids
  3. fatty acids are sent out of the liver in VLDL to adipose tissue or muscle
  4. amino acids are used for protein synthesis or are deaminated for gluconeogenesis
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21
Q

when does the post absorptive phase of energy metabolism take place

where do nutrients go

A

between meals

nutrients are being mobilized from storage pools to tissues

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22
Q

what happens during the post absorptive phase of energy metabolism (3)

A
  1. glucagon is released
  2. glycogenolysis and gluconeogenesis are stimulated to increase glucose
  3. amino acids are mobilized from muscle
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23
Q

when does the prolonged energy deficiency phase take place in energy metabolism

A

food deprivation

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24
Q

what happens during prolonged energy deficiency phase of energy metabolism (3)

A
  1. glucose and amino acids are conserved
  2. fatty acids are mobilized in the form of non esterified fatty acids (NEFA)
  3. formation of ketone bodies in liver mitochondria
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25
Q

define glycolysis

A

the breakdown of glucose by enzymes, releasing energy and pyruvic acid

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26
Q

what happens to glucose once it gets into the portal blood

A

once in the portal blood, glucose will reach the liver

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27
Q

what mediates glucose transport into cells

A

glucose transport into cells in mediated by GLUT

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28
Q

hat is the net gain of glycolysis

A

2 pyruvate
2 NADH
2 ATP

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29
Q

what happens to pyruvate and NADH produced from glycolysis

A

pyruvate used in mitochondria

NADH goes through electron transport chain and comes out as NAD+

30
Q

describe anaerobic glycolysis

A

2 ATP generated for each molecule of glucose converted to 2 molecules of lactate

no net production of NADH

31
Q

describe aerobic glycolysis

A

direct consumption and formation of ATP is the same as in anaerobic glycolysis

pyruvate imported to mitochondria to produce acetyl CoA which then enters the Krebs cycle

NADH can be oxidized during electron transport chain (regeneration of NAD+)

during electron transport chain, 3 ATP produced for each NADH molecule oxidized

32
Q

describe the TCA cycle

A

final pathway where carbs, amino acids, and fatty acids converge

energy provided by TCA is essential for most animals and humans

occurs close to electron transport chain

process is aerobic – oxygen used as electron acceptor

delivers reduced NADH and FADH2

33
Q

define gluconeogenesis

A

production of glucose from non sugar molecules such as amino acids, lactate, glycerol

34
Q

why do we need gluconeogenesis

A

during a prolonged fast, hepatic glycogen stores are depleted, glucose is then formed from precursors other than carbs

35
Q

is gluconeogenesis a reverse glycolysis

where are enzymes it uses located

A

no

it is a special pathway that requires enzymes localized in the mitochondria and the cytosol

36
Q

what are important tissues for gluconeogenesis

A

liver

kidney

37
Q

important substrates for gluconeogenesis (3)

A
  1. glycerol –> glycerol phosphate
  2. lactate –> pyruvate
  3. amino acids –> TCA cycle –> oxaloacetate
38
Q

define glycogenesis

A

mechanism to store glucose as glycogen in order to mobilize glucose in absence of a dietary source

39
Q

main glycogen stores in the body

A

skeletal muscle

liver

40
Q

define glycogenolysis

A

process by which glucose is mobilized from glycogen granules in order to be sent into the blood and to other tissues

41
Q

where does the pentose phosphate cycle occur

A

cytosol

42
Q

is ATP consumed or generated in the pentose phosphate pathway

A

no ATP is consumed or generated

43
Q

what does the pentose phosphate pathway produce

A

it produces a major portion of the NADPH used in the body as well as pentose ribose 5-phospahte

44
Q

functions of NADPH in physiological processes (5)

A
  1. important source of electrons (reductases in the body)
  2. carrying electrons to electron transport chain complexes
  3. reducing enzyme cytochrome P450
  4. respiratory burst in phagocytic cells (NADPH oxidase produces ROS to kill bacteria)
  5. synthesis of NO
45
Q

what is cytochrome P450 involved in (3)

A
  1. steroid hormone synthesis
  2. bile acid synthesis
  3. detoxification
46
Q

fate of short an medium chain fatty acids in the body

A

get into portal circulation (bound to albumin) and reach the liver

47
Q

fate of chylomicrons in the body

A

TAGs will be converted into free fatty acids and glycerol by lipoprotein lipase

48
Q

where is lipoprotein lipase expressed

A

capillaries of skeletal muscle, adipose tissue, heart, lung, kidney, liver

49
Q

what happens to FFA (3)

A

can be stored as TAG (adipocytes)

can be used to produce energy (in other cell)

can remain in the blood (bound to plasma proteins)

50
Q

what are chylomicron remnants

what happens to them

A

cholesteryl esters, phospholipids, lipoproteins, fat soluble vitamins

will be endocytosed by liver cells (receptor mediated)

51
Q

what can lipids be used for

A

energy
structural components
hormone precursors
energy reserves

52
Q

relevance of fatty acids – energy

A

during a fast period fatty acids are bound to albumin in plasma (FFA) on the way to tissues (coming form adipose tissue) –> oxidation (energy production in most tissues)

53
Q

relevance of fatty acids – structural components

A

phospholipids and glycolipids in the plasma membrane

54
Q

relevance of fatty acids – hormone production

A

prostaglandins

55
Q

relevance of fatty acids – energy reserves

A

TAG in adipose tissues

56
Q

what do you get from beta oxidation of fatty acids

A

net energy gain

from 1 palmitoyl CoA that has been oxidized to CO2 and H2O –> 8 ACoA, 7 NADH, 7 FADH2

from these molecules 131 ATP can be generated

subtract 2 ATP needed for process = 129 ATP

57
Q

how are ketone bodies formed

A

the mitochondria in liver can convert ACoA from fatty acid oxidation into ketone bodies which are important sources of energy during fasting periods

58
Q

examples of ketone bodies

A

acetoacetate
3-hydroxybutyrate (B-)
acetone

59
Q

what happens during a prolonged fast to promote ketone body formation

A

fatty acids mobilized from adipose tissue come to the liver yielding much more ACoA than necessary

fatty acid oxidation also produces high amounts of NADH, which shift OAA to malate

result is the utilization of excess ACoA for ketone bodies formation

60
Q

what happens to ketone bodies in peripheral tissues

A

they are converted to ACoA which enters TCA cycle

61
Q

fate of absorbed amino acids in the liver

A

57% – urea
14% – liver proteins
6% – plasma proteins
23% – systemic circulation

62
Q

important molecules in physiology that are derived from amino acids (4) and kinda what they do?

A
  1. hydroxylation of tryptophan yields serotonin (neurotransmitter and paracrine hormone)
  2. acetylation and methylation of serotonin –> melatonin (hormone which influences reproductive activity)
  3. hydroxylation of tyrosine yields dopa, which is subsequently decarboxylated to form neurotransmitter dopamine (in some neurons dopamine is hydroxylated to form norepinephrine)
  4. decarboxylation of histidine yields histamine (mediator of allergic reactions)
63
Q

peptides of physiological importance (4)

A
  1. oxytocin – produced in hypothalamus (uterine contraction and milk secretion)
  2. ADH – produced in hypothalamus, essential for maintenance of water balance
  3. bradykinin – vasoactive substance
  4. angiotensin II – potent vasoconstrictor
64
Q

polypeptides of physiological relevance (4)

A
  1. gastrin – stomach hormone, stimulates secretion of gastric glands
  2. CCK – stimulates pancreas and liver secretion
  3. glucagon – produces by alpha cells of pancreas
  4. atrial natriuretic peptide (ANP) – produced in heart (atria), essential for regulation of blood volume and pressure
65
Q

describe glucogenic amino acids

A

those that produce TCA intermediates and can thereby enter the TCA cycle, yielding oxaloacetate (a glucose precursor)

66
Q

list glucogenic amino acids (14)

A
  1. alanine
  2. arginine
  3. asparagine
  4. aspartate
  5. cysteine
  6. glutamate
  7. glutamine
  8. glycine
  9. proline
  10. serine
  11. histidine
  12. methionine
  13. threonine
  14. valine
67
Q

describe branch chain amino acids

A

serve as sources of energy in msucle cells

68
Q

list BCCA (3)

A
  1. valine
  2. leucine
  3. isoleucine
69
Q

what happens to BCCA

A

after deamination, BCAA are converted to a-ketoacids which enter TCA

at same time pyruvate serves as an acceptor of BCAA’s amino group yielding to the formation of alanine which leaves the msucle and is used by the liver for gluconeogenesis

70
Q

the comings and goings of BCAAs (9)

A
  1. BCAA come from blood
  2. enter muscle cell
  3. deaminate into a-ketoacids
  4. produce energy
  5. make pyruvate
  6. changes into alanine
  7. goes into blood
  8. goes to liver
  9. produce glucose
71
Q

what is a way to get alanine

A

BCAA metabolism

72
Q

why is alanine important

A

alanine from BCAA metabolism represents an important way to eliminate ammonia (NH3) from the body through urea formation in the liver (only occurs in liver)

urea then goes to kidney to be released as urine

Physiology 2 (11 decks)

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