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Biochemistry MBS > Absorption > Flashcards

Absorption Flashcards

1
Q

examples of things that increase caloric demand

A

From least to greatest:

  • digestion, min act
  • increased activity
  • trauma/surgery
  • major op
  • major burn
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2
Q

Cals/g of

  • carbs
  • protein
  • fat
A

carbs= 4Cal/g
protein=4Cal/g
fat=9Cal/g

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3
Q

basal caloric requirement

A

1400Cal/day

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4
Q

digestion/min act cal requirement

A

1560Cal/day

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5
Q

moderate activity caloric requirement

A

2300Cal/day

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6
Q

the glycemic index estimates a food’s effect on…

-what can change this

A

blood glucose and therefor insulin secretion

-how the food is prepared can affect this as well as what else you eat with it

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7
Q

major dietary monosaccharides

A
  • glucose

- fructose

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8
Q

major dietary disaccharides

A
  • maltose
  • lactose
  • sucrose
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9
Q

major dietary polysaccharide

A
  • starch

- amylose and amyloectin

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10
Q

intestinal carbohydrate enzymes (5)

-one in the saliva

A
  • alpha amylase (also secreted in the oral cavity)
  • sucrase
  • lactase
  • isomaltase
  • maltase
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11
Q

alpha amylase

A

attacks alpha glycosidic linkages of glucose polymers yielding maltoses and limit dextrin

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12
Q

sucrase

A

hydrolyzes the conversion of sucrose to fructose and glucose

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13
Q

lactase

A

-hydrolyzes lactose into galactose and glucose

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14
Q

isomaltase

A
  • capable of cleaving alpha 1,6 linkages of amylopectin

- attacks limit dextrins

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15
Q

maltase

A

catalyzes the hydrolysis of maltose to glucose

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16
Q

why is cellulose, a polyglucose, not a good energy source?

A

-it has beta linkages and out enzymes are designed to only target alpha linkages

17
Q

how does bacterial metabolism in the colon lead to clinical symptoms?

A

-this creates an osmotic effect where water rushes into the lumen of the intestine as well as H2 gas causing watery diarrhea and gas

18
Q

carbs in the intestine are absorbed via…

A

simple diffusion, facilitated diffusion, and active transport

19
Q

diffusion

A

-simply passing from one side of the membrane to the other without the use of energy or a chaperon

20
Q

facilitated diffusion

-example

A
  • this is getting across the membrane via a protein but without directly using ATP, typically a concentration gradient is utilized
  • an example of this would be the Na-glucose co-transporter. Na goes down a concentration gradient, taking glucose with it
21
Q

Glut 4

A
  • involved in facilitated transport
  • responsive to insulin in the blood
  • increases the glucose intake of muscle, fat, and white blood cells
22
Q

SGLT

-where

A
  • sodium linked glucose transporter

- located in the intestinal mucosa and kidney brush border

23
Q

how does insulin stimulate receptor function in muscle, fat, and white blood cells?

A

-when present, it increases the number of glucose receptors on the cell membrane

24
Q

how is glucose transported into most cells

-however in two places it is different

A

facilitated diffusion

  • except for in the intestine and kidney, it is active transport
  • This is via the SGLT receptor
25
Q

carbohydrate and other substances enter portal circulation by

A

-heading to the liver as their original destination

26
Q

type 1 diabetic response to increased blood glucose

A
  • higher initial response to the same food

- stays higher for a longer amount of time

27
Q

complex vs simple carb effect on blood glucose

A

-simple carbs lead to a greater glucose spike in the blood

28
Q

effect of the hexokinase reaction

A
  • once inside the cell, hexokinase adds a phosphate to glucose using ATP
  • it does this in order to keep the glucose concentration gradient down in the cell
29
Q

glucokinase vs hexokinase

A
  • hexokinase can P other hexoses, glucokinase is specific to glucose
  • glucokinase is restricted to liver and pancreatic beta-cells; hexokinases are ubiquitous
  • hexokinases, but not glucokinases, are inhibited by G6P (this way glucose uptake is limited in most cells when it needs it)
30
Q

Activity of glucokinase

A

-has a high Km so that its activity becomes important when blood glucose concentrations get high - when this happens, the liver is still capable of removing glucose from the blood

31
Q

glucose uptake in pancreatic beta cells

A

-glucokinase leads to increased production of ATP that acts on the potassium channel leading to insulin release

32
Q

Mature onset diabetes of the young

A
  • genetic deficiency in glucokinase (or transcription factor)
  • leads to a defect in insulin secretion in response to elevated blood glucose
  • in patients defective in this enzyme, the amount of ATP produced in response to elevated blood sugar is reduced, leading to a smaller effect on the ATP sensitive potassium chanel, less depolarization and less insulin secretion

Biochemistry MBS (36 decks)

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