Lecture 13: Absorption and Storage of Carbohydrates

Question 1

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

Answer 1

proteoglycans

Question 2

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

Answer 2

True

Question 3

Glucose is stored as ___

Answer 3

glycogen

Question 4

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

Answer 4

monosaccharides

Question 5

Lactose is a disaccharide made up of ___ and ___

Sucrose is a disaccharide made up of ___ and ___

Answer 5

galactose + glucose

glucose + fructose

Question 6

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

Answer 6

Oligosaccharides

Question 7

Polysaccharides can be stored as ___

Answer 7

glycogen

Question 8

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

Answer 8

True

Question 9

___ is a fuel source of glucose and polysaccharide

Answer 9

Glycogen

Question 10

Saliva contains ____, which begins the breakdown of large carbohydrates

Answer 10

alpha amylase

Question 11

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

Answer 11

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

Question 12

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

Answer 12

A-amylase

Question 13

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

Answer 13

intestinal cells; stomach acid

Question 14

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

Answer 14

pancreas; bicarbonate

Question 15

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

Answer 15

neutralize and raise pH

Question 16

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

Answer 16

pancreatic amylase
(continues to digest large carbohydrates)

Question 17

Pancreatic amylase digests carbohydrates while they are in the _____

Answer 17

small intestine

Question 18

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

Answer 18

pancreatic amylase

Question 19

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

Answer 19

Sucrase + Lactase

Question 20

Sucrase breaks sucrose into ___ and ___

Answer 20

glucose + fructose

Question 21

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

Answer 21

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

Question 22

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

Answer 22

fructose + galactose

Question 23

Lactose intolerance is an example of disaccharide deficiency

Answer 23

True

Question 24

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

Answer 24

water

Question 25

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

Answer 25

True

Question 26

In lactose intolerance, unabsorbed disaccharides that reach the large intestine are acted on by what organism? What is generated as a result of interaction?

Answer 26

Intestinal bacteria Gas and Bloating

Question 27

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 _____

Answer 27

galactose

Question 28

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 ___

Answer 28

sucrose honey, fruit, and sugar fructose

Question 29

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

Answer 29

True

Question 30

Where does nutrient, water, and electrolyte absorption occur?

Answer 30

Large Intestine

Question 31

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

Answer 31

Dietary fiber

Question 32

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

Answer 32

Glycemic Index

Question 33

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

Answer 33

True

Question 34

What two factors LOWER the GI of a food?

Answer 34

Fat and Fiber

Question 35

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

Answer 35

low; high

Question 36

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

Answer 36

high; low

Question 37

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

Answer 37

True

Question 38

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

Answer 38

branch points

Question 39

Cellular location of glycogen?

Answer 39

Cytosol (forms granules)

Question 40

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

Answer 40

Liver glycogen

Question 41

Glycogen in skeletal muscle is only for ____

Answer 41

skeletal muscle

Question 42

What are the two primary sites of glycogen?

Answer 42

Liver and skeletal muscle

Question 43

___ can help to maintain glucose levels

Answer 43

Glycogen

Question 44

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

Answer 44

True

Question 45

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

Answer 45

True

Question 46

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

Answer 46

Glycogenin

Question 47

How does glycogenin start glycogen synthesis?

Answer 47

Adds glucose molecule to itself

Question 48

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

Answer 48

Glycogen Synthase

Question 49

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.

Answer 49

True

Question 50

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

Answer 50

UDP-glucose

Question 51

Steps of Glycogen Synthesis?

Answer 51

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

Question 52

Glucose can only be added to a ___ end

Answer 52

growing

Question 53

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

Answer 53

Glycogen phosphorylase (uses phosphate to work)

Question 54

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

Answer 54

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

Question 55

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

Answer 55

outer three

Question 56

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

Answer 56

branch point

Question 57

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

Answer 57

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

Question 58

Cooperation between what two enzymes allows for glycogen breakdown?

Answer 58

Glycogen phosphorylase Transferase/De-branching enzyme

Question 59

Importance of having numerous glycogen branch points and growing ends?

Answer 59

Allows glycogen to be synthesized or broken down FAST!

Question 60

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

Answer 60

Glucose 6 phosphatase

Question 61

True or False: Skeletal muscle expresses G6P

Answer 61

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

Question 62

Three general regulatory mechanisms for glycogen metabolism?

Answer 62

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

Question 63

In a well-fed state, insulin stimulates ____ synthesis in the liver If blood glucose is low, glucagon will stimulates ___ degradation

Answer 63

glycogen glucagon

Question 64

How will epinephrine affect glycogen?

Answer 64

Epinephrine will stimulates glycogen degradation

Question 65

Insulin will stimulate ___ in muscle Epinephrine will stimulate ___ degradation in muscle

Answer 65

Insulin will stimulate glycogen synthesis in muscle Epinephrine will stimulate glycogen degradation in muscle

Question 66

Why is skeletal muscle not sensitive to glucagon?

Answer 66

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

Question 67

Is glycogen synthesized at rest? In motion?

Answer 67

At rest: glycogen synthesis In motion: glycogen degradation

Question 68

What two hormones stimulate PKA?

Answer 68

Epinephrine and Glucagon

Question 69

Upon activation, PKA phosphorylates which two enzymes?

Answer 69

Glycogen Synthase Glycogen Phosphorylase

Question 70

Phosphorylation of glycogen synthase turns it ___ Phosphorylation of glycogen phosphorylase turns it ___ Net effect?

Answer 70

OFF ON Glycogen degradation

Question 71

Epinephrine will stimulate glycogen breakdown in ___ and ___ Glucagon will only cause glycogen breakdown in ___

Answer 71

liver and skeletal muscle liver

Question 72

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

Answer 72

phosphatases glycogen synthase = ON glycogen phosphorylase = OFF

Question 73

What is glycated hemoglobin?

Answer 73

Hemoglobin with glucose attached -Marker of glycemic control over 3 to 4 months (long-term) -HbA1C test