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Biochemical and Physiological Basis of Nutrition I: Macronutrients > Carb Metabolism 1 > Flashcards

Carb Metabolism 1 Flashcards

1
Q

sources of dietary carbs for pre-agricultural humans

A
  • roots, tubers, and rhizomes
  • seeds above ground
  • certain fruits and nuts
  • inner bark of some trees

low in starch, high in fiber

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2
Q

sources of dietary carbs for industrialized humans

A

starch and fibers: pasta, apples, potatoes, bread, rice
simple sugars: sucrose, glucose, fructose: juices, honey, candy, soda

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3
Q

glucose use: postprandial

A

mainly liver, gut, and skeletal muscle

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4
Q

glucose use: post-absorptive (in between meals)

A

brain!

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5
Q

can brain live without glucose?

A

NO!
it can survive without oxygen for a few minutes, but not at all without glucose

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6
Q

most abundant form of starch

A

pectin

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7
Q

benefits of branching starches

A

it is better to keep energy in a more restricted space (human adaptation)

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8
Q

main dietary carbohydrates: disaccharides

A
  • maltose
  • lactose sucrose
  • trehalose (a1 –> 1 D-glucose)
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9
Q

lactose is made of

A

galactose + glucose joined by beta 1,4

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10
Q

sucrose is made of

A

glucose + fructose joined by alpha 1,2

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11
Q

salivary and pancreatic alpha-amylase break down what into what

A

starch into maltose, trisaccharides (smaller molecules, but still not absorbable)

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12
Q

2 main enzyme categories of carbohydrate digestion

A
  1. endoglucosidases
  2. small intestine disaccharidases
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13
Q

endoglucosidases mechanism

A

hydrolyze alpha 1,4 bonds (NOT alpha 1,6) between glucosyl residues

shortened polysaccharide chains that are formed are called alpha-dextrins

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14
Q

endoglucosidases examples

A

alpha-dextrins
salivary alpha-amylase
pancreatic alpha-amylase

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15
Q

small intestine disaccharidases mechanism

A

hydrolyze alpha 1,4, alpha 1,6, beta 1,2 (sucrose), and beta 1,4 (lactose) bonds in limit dextrins, oligo-, and disaccharides

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16
Q

small intestine disaccharides examples

A

sucrase-isomaltase
maltase-glucoamylase
lactase

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17
Q

sucrase isomaltase

A

(alpha-dextrinase) glycosidase activity: alpha-1,4, alpha-1,6, beta-1,2

18
Q

what happens if someone has a sucrase mutation?

A

we can’t degrade sucrose so we create a malabsorption for fructose, promotes diarrhea (water is trapped, fructose is never degraded)

19
Q

no lactase =

A

lactose remains in intestinal lumen, draws in water, leads to diarrhea

bacteria is waiting for lactose

20
Q

lactase deficiency produces

A

flatulence and diarrhea when dairy sugars are consumed

21
Q

3 types of lactase deficiency

A
  1. primary hypolactasia
  2. primary congenital hypolactasia (alactasia)
  3. secondary hypolactasis
22
Q

primary hypolactasia

A

autosomal recessive; lactase activity declines over many years, usually beginning in late childhood

23
Q

primary congenital hypolactasia (alactasia)

A

very rare genetic conditionl complete absence of lactase

24
Q

primary congenital hypolactasia (alactasia)

A

very rare genetic conditionl complete absence of lactase

25
Q

secondary hypolactasis

A

due to damage of bursh border of intestinal enterocytes due to intestinal disease

26
Q

lactase cuts…

A

lactose into galatose and glucose

27
Q

when does lacrase activity begin

A

in utero

28
Q

when is lactase activity highest

A

during the last trimester
remains that high for amonth after birth

29
Q

reduction of lactase activity

A

reduces considerably after 1 month after birth
by 8 years old it is very reduced

30
Q

why did human adults start drinking milk?

A

it is nutrient dense
it has water –> cleanest source of water at the time!

31
Q

Sweden: why are they so special

A

90%+ of population is lactose tolerant
bc they did not domesticate cattle

32
Q

what type of groups are lactose intolerant

A

groups not dependent on cattle
EX: Southeast Asia, West Afrida, Native Americans in southwest of US

33
Q

what type of groups are lactose tolerant

A

cattle herders
EX: Europe, the Middle East, and Africa

34
Q

SGLT limitations

A

limited capacity as a transporter
only capable of sensing limited amounts of glucose in cytoplasm

35
Q

GLUT5

A

specialized in fructose absorption

36
Q

main function of insulin

A

put away glucose, so energy can be used at a later time

37
Q

GLUT1 + GLUT3

A

incorporate glucose into important tissues

38
Q

GLUT3 tissue of interest

A

brain

39
Q

which transporter is stimulated by insulin?

A

GLUT4

40
Q

Which transporter is an exclusive transporter of fructose?

A

GLUT5

41
Q

regulation of insulin secretion by glucose steps

A
  1. GLUT2 brings glucose into cell
  2. ATP blocks potassium channel
  3. Massive release of insulin

More glucose in circulation = more glucose absorbed in first step = more release of insulin

Biochemical and Physiological Basis of Nutrition I: Macronutrients (12 decks)

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