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nutr 3210 > carbohydrates > Flashcards

carbohydrates Flashcards

1
Q

what are polysaccharides?

A

branches of monosaccharides attached by glycosidic bonds

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2
Q

what are homo and polysaccharides?

A
  • homo: one type of monosaccharide
  • poly: different monosaccharides
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3
Q

what is starch?

A
  • homopolysaccharide
  • rich in plants
  • amylose, amylopectin
  • polymer of D-glucose
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4
Q

what is glycogen?

A

polysaccharide rich in animal tissue

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5
Q

what is the advantage of branching in polysaccharides?

A

a larger number of ends from which to cleave glucose when energy is needed (why glycogen has a lot more branching)

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6
Q

what is dietary fibre?

A
  • non digestible complex CHO
  • structural part of plants
  • water holding ability
  • adsorptive ability: binds enzymes and nutrients
  • insoluble or soluble
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7
Q

what is insoluble fibre?

A
  • intact in GIT (doesn’t dissolve)
  • reduces transit time so things move quickly in gut
  • increases fecal bulk
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8
Q

what is soluble fibre?

A
  • goes into solution (dissolves)
  • forms a gel
  • delays gastric emptying, increases transit time
  • slows down rate of nutrient absorption
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9
Q

what are the health benefits of insoluble and soluble fibres?

A
  • insoluble: decreases constipation, stimulates muscle contraction to break down waste, decreases risk of bacterial infection
  • soluble: increases satiety
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10
Q

what is the effect of soluble fibre on cardiovascular disease?

A

decreases cardiovascular disease when it forms a gel bc it binds to cholesterol in the small intestine and carries it out of the body and it may also lower the risk of type ii diabetes by binding some glucose in the digestive tract

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11
Q

where are CHOs digested?

A
  • mouth
  • stomach
  • small intestine
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12
Q

what is alpha amylase?

A
  • operates in the mouth, stomach, and small intestine
  • inactivated in stomach by pH drop
  • breaks down alpha 1,4 glycosidic bonds
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13
Q

what are brush border enzymes?

A
  • enzymes in brush border between intestinal lumen and epithelial cells
  • break down disaccharides so the monomers can be transported across membrane by specific transporters
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14
Q

what does isomaltase/alpha-dextrinase produce?

A

breaks alpha 1,6 glycosidic bonds to make 2 glucose from isomaltose

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15
Q

what does maltase produce?

A

2 glucose from maltose

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16
Q

what does invertase/sucrase produce?

A

1 glucose and 1 fructose from sucrose

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17
Q

what does lactase produce?

A

1 glucose and 1 galactose from lactose

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18
Q

how does lactose intolerance?

A

lost functionality of enzyme lactase in small intestine causes bacterial fermentation of lactose in large intestine which produces gases that cause irritation

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19
Q

what is monosaccharide absorption?

A

very efficient absorption where almost all monosaccharides are taken up by enterocytes back into the body

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20
Q

how is glucose absorbed into the blood?

A
  • taken up into enterocyte by SGLT1 on apical side along with 2 Na molecules via conc. gradient
  • conc. gradient produced by basolateral Na-K ATPase activity which pumps sodium out of the cell and requires ATP
  • enters blood from enterocyte via basolateral GLUT2 transporter
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21
Q

how is fructose absorbed into the blood?

A
  • taken up into cell by GLUT5 on apical surface via facilitated transport
  • enters blood via basolateral GLUT2
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22
Q

what is the primary source of energy for cells?

A
  • glucose
  • needed especially for RBCs as they have no mitochondria to make energy
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23
Q

what “spares” protein and how?

A
  • CHOs
  • prevent breakdown of protein for energy
  • protein used for building, repairing, and maintaining tissues instead
24
Q

what are simple and complex CHOs?

A
  • simple: mono and disaccharides
  • complex: oligo and polysaccharides
25
Q

what are oligosaccharides?

A

short chain monosaccharides

26
Q

what are polysaccharides?

A
  • like oligo but bigger, can be homo or hetero
  • glycogen in animals and starch and cellulose in plants
27
Q

what is the H to O ratio in CHOs?

A

2:1

28
Q

what are trioses?

A

3 carbon sugar, metabolites of glucose

29
Q

what are pentoses?

A

5 carbon sugar, components of DNA and RNA

30
Q

what are hexoses?

A

6 carbon sugar, most important nutritionally (glucose)

31
Q

what is stereoisomerism?

A

two molecules have the same formula but differ spatially due to chiral carbon atoms

32
Q

what are enantiomers?

A

mirror images

33
Q

what is an anomeric carbon?

A
  • the carbon in the carbonyl group
  • where counting carbons begins
34
Q

what is the D vs L form?

A
  • D: the OH on the highest chiral carbon is on the right, nutritionally more important sinze enzymes process it
  • L: the OH on the highest chiral carbon is on the left
35
Q

how do you calculate the number of stereoisomers for a molecule?

A

2^n where n = # of chiral carbons

36
Q

what is a hemiacetal vs hemiketal?

A
  • hemiacetal: made from an aldose (aldehyde group, carbonyl is on the outside)
  • hemiketal: made from a ketose (ketone group, carbonyl is in the middle)
37
Q

what is a disaccharide?

A
  • most common oligosaccharide
  • 2 monosaccharides attached by a glycosidic bond
38
Q

how do you determine where the disaccharide is alpha or beta?

A

configuration of the OH group on the anomeric carbon

39
Q

what are common disaccharides?

A

sucrose, lactose, maltose

40
Q

what is glycogenesis?

A
  • making glucose stores through glycogen
  • insulin induced
  • occurs in muscles through hexokinase and liver through glucokinase
41
Q

which enzyme is inhibited by G6P?

A

hexokinase in muscle

42
Q

how is glycogen produced?

A

G6P turns into G1P which loses a phosphate to become glycogen

43
Q

why doesn’t G6P inhibit glucokinase?

A

allows excess glucose to enter the liver cell to phosphorylate it quickly and encourage glucose to enter the liver quickly when glucose levels are high

44
Q

what is glycogenin?

A

an enzyme that serves as a scaffold on which to attach glucose molecules to build glycogen

45
Q

what is glycogenolysis?

A
  • glucagon induced when glucose is low
  • glycogen phosphorylase breaks alpha 1,4 glycosidic bond in glycogen
  • glucose 6 phosphatase removes phosphate from G6P which is released into the blood by the liver only as only the liver can express glucose 6 phosphatase
46
Q

what phosphorylates fructose and what is the outcome?

A
  • phosphofructokinase
  • produces fructose 1,6 biphosphate
47
Q

what is the net energy yield from 1 glucose in glycolysis?

A
  • 2 NADH and 2 ATP
  • which is equal to 8 ATP since 1 NADH = 3 ATP
48
Q

how do RBCs generate ATP?

A

need to use glycolysis since they have no mitochondria

49
Q

what are the products of anaerobic metabolism?

A

lactid acid and ethanol

50
Q

what is significance of the cori cycle?

A

it isn’t sustainable since it uses more ATP than it makes

51
Q

what is the hexose monophosphate shunt?

A

uses G6P to produce NADPH

52
Q

what is pyruvate dehydrogenase?

A
  • irreversible
  • occurs in the mitochondrial matrix
  • pyruvate is converted into acetyl coa
  • vitamins are required for it to function
  • produces 2 NADH = 6 ATP
53
Q

how much energy is yielded from 1 acetyl coa in the krebs cycle?

A
  • 3 NADH, 1 FADH2, 1 GTP
  • equal to 12 ATP
  • since 2 acetyl coa are produced the cycle produces 24 ATP
54
Q

what are the ATP equivalents of common energy molecules?

A
  • 1 NADH = 3 ATP
  • 1 FADH2 = 2 ATP
  • 1 GTP = 1 ATP
55
Q

where does the krebs cycle take place?

A

mitochondrial matrix

56
Q

how much ATP is yielded from the complete oxidation of 1 molecule of glucose?

A

38 ATP

57
Q

what is gluconeogenesis?

A
  • synthesizing from non CHO stores to make glucose
  • active in liver, happens in kidney during starvation
  • muscle and adipose tissue lack enzymes for gluconeogenesis

nutr 3210 (5 decks)

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