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Biochemistry I/II > Lecture 13: Absorption and Storage of Carbohydrates > Flashcards

Lecture 13: Absorption and Storage of Carbohydrates Flashcards

1
Q

Carbohydrates can allow for formation of ___, which is present in connective tissues and joints

A

proteoglycans

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2
Q

True or False: Carbohydrates are important for cell to cell recognition

A

True

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3
Q

Glucose is stored as ___

A

glycogen

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4
Q

Glucose, Fructose, and Galactose are _____ (single units)

A

monosaccharides

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5
Q

Lactose is a disaccharide made up of ___ and ___

Sucrose is a disaccharide made up of ___ and ___

A

galactose + glucose

glucose + fructose

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6
Q

____ are short chains of monosaccharides that are particularly important for cell recognition and attachment

A

Oligosaccharides

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7
Q

Polysaccharides can be stored as ___

A

glycogen

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8
Q

True or False: polysaccharides make up make components of DNA/RNA

A

True

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9
Q

___ is a fuel source of glucose and polysaccharide

A

Glycogen

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10
Q

Saliva contains ____, which begins the breakdown of large carbohydrates

A

alpha amylase

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11
Q

True or False: A small portion of glucose can be absorbed indirectly across mucus membrane of the mouth

A

False - A small portion of glucose can be absorbed DIRECTLY across mucus membrane of the mouth

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12
Q

After leaving the mouth, carbohydrates enter stomach and begin mixing in stomach acid. What enzyme is inactived by stomach acid?

A

A-amylase

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13
Q

Secretin is release from _____ cells in response to the ____ ____ entering the small intestine

A

intestinal cells; stomach acid

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14
Q

Secretin sends a signal to ___ that food is entering the stomach. In response, the above mentioned organ releases ____

A

pancreas; bicarbonate

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15
Q

Secretin stimulates pancreas to release ___into the small intestine to ___ and _____

A

neutralize and raise pH

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16
Q

As HCO3 is being released, the pancreas also secretes ___into the small intestine

A

pancreatic amylase
(continues to digest large carbohydrates)

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17
Q

Pancreatic amylase digests carbohydrates while they are in the _____

A

small intestine

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18
Q

If bicarbonate were not secreted by pancreas, ___ could not be produced

A

pancreatic amylase

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19
Q

What are examples of two types of disaccharidases found on the surface of intestinal cells?

A

Sucrase + Lactase

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20
Q

Sucrase breaks sucrose into ___ and ___

A

glucose + fructose

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21
Q

What is the benefit of having disaccharidases on surface of intestinal cells?

A

Once disaccharides are broken down into single units, they can be absorbed

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22
Q

Once digested and absorbed, ____ and ___ are metabolized in the liver

A

fructose + galactose

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23
Q

Lactose intolerance is an example of disaccharide deficiency

A

True

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24
Q

When one lacks lactase, unabsorbed disaccharides attracts____ to the intestine, leading to diarrhea

A

water

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25
Q

True or False: In lactose intolerance, disaccharides are not digested and, as such, move through intestines without being absorbed

A

True

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26
Q

In lactose intolerance, unabsorbed disaccharides that reach the large intestine are acted on by what organism?

What is generated as a result of interaction?

A

Intestinal bacteria

Gas and Bloating

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27
Q

Deficiency in liver enzyme involved in ____ metabolism will cause ill feeling after consuming milk/dairy (this is rare!)

As a result of this deficiency, there is a build up of _____

A

galactose

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28
Q

Deficiency in liver enzyme involved in ___ metabolism will lead to feeling ill after ingesting what three food items?

In this disorder, there is a build up of ___

A

sucrose

honey, fruit, and sugar

fructose

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29
Q

True or False: Bacteria in the large intestine will digest some substance that cannot be digested by humans

A

True

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30
Q

Where does nutrient, water, and electrolyte absorption occur?

A

Large Intestine

31
Q

____, such as: cellulse, is an undigestable carbohydrate in humans and is excreted

A

Dietary fiber

32
Q

____: Classifications of foods based on ability to raise glucose after consumption

A

Glycemic Index

33
Q

True or False: The Glycemic Index is based on how a food is digested or absorbed

A

True

34
Q

What two factors LOWER the GI of a food?

A

Fat and Fiber

35
Q

An orange has a ___ GI while orange juice has a ___ GI

A

low; high

36
Q

A plain piece of toast has a ____ GI while one with butter has a ____GI

A

high; low

37
Q

True or False: Glycogen consists of a polymerized glucose, which forms a circular structure

A

True

38
Q

Although a majority of glycogen is made up of linear chains, ~10% of glycogen molecules contain ____ ____

A

branch points

39
Q

Cellular location of glycogen?

A

Cytosol (forms granules)

40
Q

What kind of glycogen is the fuel source for the entire body?

A

Liver glycogen

41
Q

Glycogen in skeletal muscle is only for ____

A

skeletal muscle

42
Q

What are the two primary sites of glycogen?

A

Liver and skeletal muscle

43
Q

___ can help to maintain glucose levels

A

Glycogen

44
Q

True or False: There are separate pathways for glycogen synthesis and degradation

A

True

45
Q

True or False: Genetic conditions involving defects in glycogen storage or release can cause numerous pathologies

A

True

46
Q

____ is the protein at the center of the glycogen molecule that uses UDP-glucose (activated form of glucose)

A

Glycogenin

47
Q

How does glycogenin start glycogen synthesis?

A

Adds glucose molecule to itself

48
Q

Once glycogenin acts, ____ will add additional glucose units to growing end

A

Glycogen Synthase

49
Q

True or False: Glycogen Synthase can only add to an EXISTING chain of glucose. In other words, needs glycogenin to add additional units before it can work.

A

True

50
Q

_____: activated form of glucose that is used in the cell to build glycogen

A

UDP-glucose

51
Q

Steps of Glycogen Synthesis?

A

1) Activation of UDP-glucose

2) Glycogenin adds glucose molecules to itself using UDP-glucose

3) Glycogen synthase catalyzes addition of more glucose units

4) Branching Enzyme will periodically move a block of 5-8 glucose molecules from growing end and reattach it to another point => BRANCH POINT (increases the growing number of growing ends for glycogen molecule) => two growing ends

52
Q

Glucose can only be added to a ___ end

A

growing

53
Q

What enzyme will remove glucose units with a phosphate attached when active (has a role in glycogenolysis)?

A

Glycogen phosphorylase
(uses phosphate to work)

54
Q

Glycogen phosphorylase will remove glucose units one by one until only __ units on branch remain

A

4

(at this point: it can no longer break down glucose)

55
Q

Using its transferase activity, the transferase/debranching enzyme will remove ____ glucose molecules, adding them to a different chain

A

outer three

56
Q

Using its debranching enzymes, the transferase/debranching enzyme uses water to remove remaining ______ glucose

A

branch point

57
Q

How does the amount of glycogen breakdown affect glucose units that will become available for use?

A

The more glycogen that is broken down, the more individual glucose units will be available for use

58
Q

Cooperation between what two enzymes allows for glycogen breakdown?

A

Glycogen phosphorylase
Transferase/De-branching enzyme

59
Q

Importance of having numerous glycogen branch points and growing ends?

A

Allows glycogen to be synthesized or broken down FAST!

60
Q

What enzyme is expressed in liver cells and allows for GLUCOSE to be exported to the blood and be made available to the body?

A

Glucose 6 phosphatase

61
Q

True or False: Skeletal muscle expresses G6P

A

False - it does NOT. As a result, glucose made in skeletal muscle is only made available to the muscle itself

62
Q

Three general regulatory mechanisms for glycogen metabolism?

A

1) Hormones - insulin, epinephrine, glucagon
2) Allosteric regulation
3) Substrate availability (glucose)

63
Q

In a well-fed state, insulin stimulates ____ synthesis in the liver

If blood glucose is low, glucagon will stimulates ___ degradation

A

glycogen
glucagon

64
Q

How will epinephrine affect glycogen?

A

Epinephrine will stimulates glycogen degradation

65
Q

Insulin will stimulate ___ in muscle

Epinephrine will stimulate ___ degradation in muscle

A

Insulin will stimulate glycogen synthesis in muscle

Epinephrine will stimulate glycogen degradation in muscle

66
Q

Why is skeletal muscle not sensitive to glucagon?

A

Muscle cannot help with low glucose levels because it cannot release glucose due to LACK of G6P

67
Q

Is glycogen synthesized at rest? In motion?

A

At rest: glycogen synthesis
In motion: glycogen degradation

68
Q

What two hormones stimulate PKA?

A

Epinephrine and Glucagon

69
Q

Upon activation, PKA phosphorylates which two enzymes?

A

Glycogen Synthase
Glycogen Phosphorylase

70
Q

Phosphorylation of glycogen synthase turns it ___

Phosphorylation of glycogen phosphorylase turns it ___

Net effect?

A

OFF
ON

Glycogen degradation

71
Q

Epinephrine will stimulate glycogen breakdown in ___ and ___

Glucagon will only cause glycogen breakdown in ___

A

liver and skeletal muscle

liver

72
Q

Insulin activates ____, which remove phosphate groups from ___ and ___

A

phosphatases

glycogen synthase = ON
glycogen phosphorylase = OFF

73
Q

What is glycated hemoglobin?

A

Hemoglobin with glucose attached

-Marker of glycemic control over 3 to 4 months (long-term)

-HbA1C test

Biochemistry I/II (23 decks)

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