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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
What is a chiral carbon?
4 different atoms or groups attached to them
26
What are different examples of Steroisomerism? Explain each.
1) Optical isomerism--> Enantiomers (+) and (-), Diastereomers (R & S) or (D and L) 2) Geometrical isomerism (trans and cis)
27
What are Diastereomers?
2 or more carbon atoms with same 4 groups attached but are not mirror images of each other (CHIRAL)
28
Aldose sugars are based on D and L ________.
glyceraldehyde
29
Glyceraldehyde has ____ chiral carbon. D sugar has an -OH group where in the Fisher Projection formula?
1; RIGHT
30
Ketoses are built up from _______, however this compound doesnt have a chiral carbon. What is ketose spatial orientation labeling based on?
dihydroxyacetone; D or L erythulose
31
Fructose is made up of what?
Ketose and Hexose
32
If glucose has 4 chiral carbons, how many stereoisomers will it have?
2^4 stereoisomers
33
Are D or L configurations more important? Why?
D; these are metabolized | *Enzymes in CHO digestion are stereospecific for D isomers
34
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?
ring structures; aldehyde or ketone; alpha and beta; open-chain aldehyde or ketone
35
What is Mutarotation?
The conversion back and forth between alpha and beta.
36
Despite the very low concentration of the open chain _____, typical chemical reactions of these take place _____.
aldehydes; rapidly
37
Pyran means?
6- membered ring
38
Furan means?
5- membered ring
39
For D sugars, the -OH group is down for ____ and up for ____.
down--> alpha Up--> beta (opposite for L sugars)
40
A reaction of many sugars is to reduce either _____ or ______ solutions.
Fehling's or Benedict's
41
What is a reducing sugar?
the sugar must have an anomeric carbon and can exhibit mutarotation through acyclic molecule
42
Which sugar appears able to mutarotate but is not a reducing sugar?
fructose
43
Disaccharides are glycosides because why? Explain.
They all contain a glycosidic bond, which is an acetal link Maltose: glucose-glucose Lactose: glucose-galactose Sucrose: glucose-fructose
44
What is an example of a non-reducing sugar? Explain why?
Sucrose | It shows no mutarotation. This is because both possible anomeric carbons are linked in the glycosidic bond
45
Are Oligosacchardies digestible?
NO
46
Cellulose
A fiber because of the stereospecificity of alpha-amylose that digests starch. BETA BONDS; NOT DIGESTIBLE (linear beta 1-4)
47
Amylose (starch)
a linear chain of glucose bonded by alpha 1-4 bonds (DIGESTIBLE; LINEAR)
48
Amylopectin (starch)
glucose molecules bonded together by a highly branched arrangement (DIGESTIBLE) (alpha-1,4 and alpha 1,6--> branch point)
49
Glycogen
``` highly branched (alpha-1,4 and alpha-1,6) quick release of glucose ```
50
Are there more branch points in glycogen or amylopectin?
glycogen
51
What are disaccharidases?
Active microvilli of enterocytes in digestion that breaks down the disaccharides in monos
52
Most starches are 80% what?
amylopectin
53
What is easier to digest: amylopetin or amylose?
amylopectin | Amylose has only 2 end sites that are often inaccessible because of folding
54
Absorptive capacity of glucose is ______ g/day and for fructose _______ g/day.
5,400; 4,800
55
Digestion and absorption are so highly efficient that most digestible CHO are digested and absorbed by when?
the end of the jejunum
56
What is the problem with fructose and absorption?
At typical dietary intakes of fructose, fructose doesn't get past the liver into the systemic blood.
57
What isO-β-D-fructofuranosyl-(2 -->1)-α-D-glucopyranoside?
SUCROSE
58
How are water-soluble nutrients absorbed?
They enter the portal vein through the intestinal cells to the liver and into the blood stream
59
Monosaccharides enter the liver by ______ _____.
facilitated diffusion
60
Which organ plays the biggest role in blood glucose regulation?
LIVER
61
Usually all or most of fructose and galactose are converted to ___ in the _____.
glucose; liver
62
What is fructokinase? Where is it located?
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
What is glucokinase? Where is it located?
Located in the liver. It catalyzes the phosphorylation of glucose to glucose-6 phosphate **This enzyme is affected by fasting and insulin
64
How can fructose be metabolized?
By adipose tissue and muscle. | *However, glucose inhibits phosphorylation of fructose because its a better substrate for hexokinase
65
Does fructose or glucose undergo more rapid glycolysis in the liver? Why?
Fructose because it bypasses the regulatory steps. | *Fatty acids from pyruvate to acetyl-CoA and glycerol from triosoes
66
What are trioses of glycolysis?
precursors of glycerol 3-phosphate for triglyceride synthesis in tissues other than the liver
67
Glucose transporter isoforms include what characteristics?
1) Integral proteins 2) Specific binding site 3) Conformational change 4) Can reverse this change when not bound to molecule
68
GLUT 1
Basic supply of glucose to cells
69
GLUT 2
Low affinity transporter
70
GLUT 3
High affinity transporter for brain
71
GLUT 4
INSULIN SENSITIVE | In muscle and adipose tissues
72
GLUT 5
For fructose
73
Insulin is produced by _____ _____. What role does it play? What does it bind to and stimulate?
pancreatic B-cells Role in cellular glucose absorption Binds to membrane receptor Stimulate GLUT 4 to move to membrane
74
Glucose insulin
SLIDE 51
75
Insulin is opposed by which hormones. Explain each.
Glucagon--> In between meals Cortisol and epinephrine--> stress Growth hormone--> promotes amino acid uptake as blood glucose drops and insulin drops
76
Glycemic Index
The rate at which glucose is absorbed (%)
77
Glycemic Load
considers the actual amount of CHO in the food (decimal * g CHO in standard serving)
78
Carrots and GI and GL
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
What is Gluconeogenesis?
The production of 5-carbon monosaccharides and NADPH
80
What is the 3-carbon rule?
You must have 2 pyruvate (3 carbons) to go into glycolysis
81
What is the 2-carbon rule?
Anything that has 2 carbons can NOT make glucose--> anything that breaks down into Acetyl COA
82
Which step is IRREVERSIBLE?
pyruvate to acetyl CoA Acetyl CoA does NOT make provide carbons for glucose synthesis
83
What are the 5 stages of glucose homeostasis?
1) Absorptive 2) Post-Absorptive 3) Early Fast 4) Intermediate Starvation 5) Long- term Starvation
84
Which stage is the fed stage?
Absorptive
85
Which stage is the in between meal stage?
Post-Absorptive
86
Most of us dont even get into what stage?
TWO unless we skip breakfast

HUEC 3115 Test One (5 decks)

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