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HUEC 3115 Test One > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

What is the major source of fuel for most people?

A

Carbs

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2
Q

What does it mean if you maintain your weight?

A

You burn the same amount of energy you consume either right after a meal or in between meals–> energy equilibrium

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3
Q

If you consume an Atkins diet, what would most likely be the major source of fuel?

A

fat

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4
Q

Almost 1/2 of CHO is from _______while the other is supplied as _____ ______.

A

polysaccharides; simple sugars

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5
Q

What are 1 sugar unit simple CHOs?

A

Monosaccharides

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6
Q

What are the 3 monosaccharides?

A

glucose, fructose, and galactose

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7
Q

What are 2 sugar unit simple CHOs?

A

Disaccharides

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8
Q

What are the 3 disaccharides?

A

Lactose, sucrose, and maltose

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9
Q

What are 3-10 sugar unit complex CHOs?

A

Oligosaccharides

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10
Q

What are the 3 oligosaccharides?

A

raffinose, stachyose, and verbacose

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11
Q

What are >10 sugar unit complex CHOs?

A

Polysaccharides

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12
Q

What are the 3 types of Polysaccharides?

A

starch, glycogen, and cellulose

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13
Q

What is High-fructose corn syrup?

A

It has undergone enzymatic processing to convert glucose into fructose and has been mixed with pure corn syrup (100% glucose) to produce desired sweetness

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14
Q

What does the US use as a sugar substitute?

A

HFCS

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15
Q

What are the two most common HFCS?

A

HFCS 55 (55% fructose and 45% glucose) and HFCS 42 (42% fructose and 53% glucose)

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16
Q

What did HFCS partially replace and WHY?

A

SUCROSE (table sugar) due to governmental subsidies of US corn and an import tariff on foreign sugar, rising the price of sucrose. It is also cost-efficient

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17
Q

Does HFCS or sucrose contribute more to obesity?

A

Neither

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18
Q

What is sucrose?

A

A disaccharide composed of glucose and fructose linked together with a relatively weak glycosidic bond.

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19
Q

What makes us fatter carbs or fat? Explain.

A

People began consuming more energy from CHO without cutting back on energy from fat. % energy from fat declined
*Energy increased, people eat more.. Certain carbs did go up (mostly refined grains), the total amount of fat also went up (not as much as carbs).

What made us fatter? We ate more energy! %Fat dropped because it was masked by an increase in % carbs increase however, the total grams of fat still increased.

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20
Q

1) Monosaccharides exist as what type of carbons?
2) What type of functional group do they consist of?
3) Where do they occur?
4) What are they composed of?

A

1) 3-7 carbons
2) carbonyl group
3) In nature or as digestion products
4) Either as an aldehyde or a ketone

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21
Q

If it is an aldehyde, it is an _______.

If it is a ketone, it is a ______.

A

aldose; ketose

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22
Q

What is a ketopentose?

A

5 carbon sugar with a ketone group

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23
Q

What are examples of hexoses?

A

glucose, fructose, and galactose

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24
Q

What are examples of aldoses and ketoses?

A

Aldose: glucose and galactose
Fructose: ketone

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25
Q

What is a chiral carbon?

A

4 different atoms or groups attached to them

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26
Q

What are different examples of Steroisomerism? Explain each.

A

1) Optical isomerism–> Enantiomers (+) and (-), Diastereomers (R & S) or (D and L)
2) Geometrical isomerism (trans and cis)

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27
Q

What are Diastereomers?

A

2 or more carbon atoms with same 4 groups attached but are not mirror images of each other (CHIRAL)

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28
Q

Aldose sugars are based on D and L ________.

A

glyceraldehyde

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29
Q

Glyceraldehyde has ____ chiral carbon. D sugar has an -OH group where in the Fisher Projection formula?

A

1; RIGHT

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30
Q

Ketoses are built up from _______, however this compound doesnt have a chiral carbon. What is ketose spatial orientation labeling based on?

A

dihydroxyacetone; D or L erythulose

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31
Q

Fructose is made up of what?

A

Ketose and Hexose

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32
Q

If glucose has 4 chiral carbons, how many stereoisomers will it have?

A

2^4 stereoisomers

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33
Q

Are D or L configurations more important? Why?

A

D; these are metabolized

*Enzymes in CHO digestion are stereospecific for D isomers

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34
Q

Majority of monos exist in______ structure. The anomeric carbon is either the ______ or _______. There is an equilibrium between which two structures. The intermediate between the 2 ring structures is what?

A

ring structures; aldehyde or ketone; alpha and beta; open-chain aldehyde or ketone

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35
Q

What is Mutarotation?

A

The conversion back and forth between alpha and beta.

36
Q

Despite the very low concentration of the open chain _____, typical chemical reactions of these take place _____.

A

aldehydes; rapidly

37
Q

Pyran means?

A

6- membered ring

38
Q

Furan means?

A

5- membered ring

39
Q

For D sugars, the -OH group is down for ____ and up for ____.

A

down–> alpha
Up–> beta
(opposite for L sugars)

40
Q

A reaction of many sugars is to reduce either _____ or ______ solutions.

A

Fehling’s or Benedict’s

41
Q

What is a reducing sugar?

A

the sugar must have an anomeric carbon and can exhibit mutarotation through acyclic molecule

42
Q

Which sugar appears able to mutarotate but is not a reducing sugar?

A

fructose

43
Q

Disaccharides are glycosides because why? Explain.

A

They all contain a glycosidic bond, which is an acetal link
Maltose: glucose-glucose
Lactose: glucose-galactose
Sucrose: glucose-fructose

44
Q

What is an example of a non-reducing sugar? Explain why?

A

Sucrose

It shows no mutarotation. This is because both possible anomeric carbons are linked in the glycosidic bond

45
Q

Are Oligosacchardies digestible?

A

NO

46
Q

Cellulose

A

A fiber because of the stereospecificity of alpha-amylose that digests starch.
BETA BONDS; NOT DIGESTIBLE
(linear beta 1-4)

47
Q

Amylose (starch)

A

a linear chain of glucose bonded by alpha 1-4 bonds (DIGESTIBLE; LINEAR)

48
Q

Amylopectin (starch)

A

glucose molecules bonded together by a highly branched arrangement (DIGESTIBLE)
(alpha-1,4 and alpha 1,6–> branch point)

49
Q

Glycogen

A 
highly branched (alpha-1,4 and alpha-1,6)
quick release of glucose
50
Q

Are there more branch points in glycogen or amylopectin?

A

glycogen

51
Q

What are disaccharidases?

A

Active microvilli of enterocytes in digestion that breaks down the disaccharides in monos

52
Q

Most starches are 80% what?

A

amylopectin

53
Q

What is easier to digest: amylopetin or amylose?

A

amylopectin

Amylose has only 2 end sites that are often inaccessible because of folding

54
Q

Absorptive capacity of glucose is ______ g/day and for fructose _______ g/day.

A

5,400; 4,800

55
Q

Digestion and absorption are so highly efficient that most digestible CHO are digested and absorbed by when?

A

the end of the jejunum

56
Q

What is the problem with fructose and absorption?

A

At typical dietary intakes of fructose, fructose doesn’t get past the liver into the systemic blood.

57
Q

What isO-β-D-fructofuranosyl-(2 –>1)-α-D-glucopyranoside?

A

SUCROSE

58
Q

How are water-soluble nutrients absorbed?

A

They enter the portal vein through the intestinal cells to the liver and into the blood stream

59
Q

Monosaccharides enter the liver by ______ _____.

A

facilitated diffusion

60
Q

Which organ plays the biggest role in blood glucose regulation?

A

LIVER

61
Q

Usually all or most of fructose and galactose are converted to ___ in the _____.

A

glucose; liver

62
Q

What is fructokinase? Where is it located?

A

Located in the liver. It catalyzes the phosphorylation of fructose to fructose 1-phosphate
*This enzyme does not act on glucose and its activity isn’t affected by fasting and insulin

63
Q

What is glucokinase? Where is it located?

A

Located in the liver. It catalyzes the phosphorylation of glucose to glucose-6 phosphate
**This enzyme is affected by fasting and insulin

64
Q

How can fructose be metabolized?

A

By adipose tissue and muscle.

*However, glucose inhibits phosphorylation of fructose because its a better substrate for hexokinase

65
Q

Does fructose or glucose undergo more rapid glycolysis in the liver? Why?

A

Fructose because it bypasses the regulatory steps.

*Fatty acids from pyruvate to acetyl-CoA and glycerol from triosoes

66
Q

What are trioses of glycolysis?

A

precursors of glycerol 3-phosphate for triglyceride synthesis in tissues other than the liver

67
Q

Glucose transporter isoforms include what characteristics?

A

1) Integral proteins
2) Specific binding site
3) Conformational change
4) Can reverse this change when not bound to molecule

68
Q

GLUT 1

A

Basic supply of glucose to cells

69
Q

GLUT 2

A

Low affinity transporter

70
Q

GLUT 3

A

High affinity transporter for brain

71
Q

GLUT 4

A

INSULIN SENSITIVE

In muscle and adipose tissues

72
Q

GLUT 5

A

For fructose

73
Q

Insulin is produced by _____ _____. What role does it play? What does it bind to and stimulate?

A

pancreatic B-cells
Role in cellular glucose absorption
Binds to membrane receptor
Stimulate GLUT 4 to move to membrane

74
Q

Glucose insulin

A

SLIDE 51

75
Q

Insulin is opposed by which hormones. Explain each.

A

Glucagon–> In between meals
Cortisol and epinephrine–> stress
Growth hormone–> promotes amino acid uptake as blood glucose drops and insulin drops

76
Q

Glycemic Index

A

The rate at which glucose is absorbed (%)

77
Q

Glycemic Load

A

considers the actual amount of CHO in the food (decimal * g CHO in standard serving)

78
Q

Carrots and GI and GL

A

Carrots have a high GI but a low GL so you would have to eat a LOT of carrots to absorb a lot of glucose

79
Q

What is Gluconeogenesis?

A

The production of 5-carbon monosaccharides and NADPH

80
Q

What is the 3-carbon rule?

A

You must have 2 pyruvate (3 carbons) to go into glycolysis

81
Q

What is the 2-carbon rule?

A

Anything that has 2 carbons can NOT make glucose–> anything that breaks down into Acetyl COA

82
Q

Which step is IRREVERSIBLE?

A

pyruvate to acetyl CoA

Acetyl CoA does NOT make provide carbons for glucose synthesis

83
Q

What are the 5 stages of glucose homeostasis?

A

1) Absorptive
2) Post-Absorptive
3) Early Fast
4) Intermediate Starvation
5) Long- term Starvation

84
Q

Which stage is the fed stage?

A

Absorptive

85
Q

Which stage is the in between meal stage?

A

Post-Absorptive

86
Q

Most of us dont even get into what stage?

A

TWO unless we skip breakfast

HUEC 3115 Test One (5 decks)

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