Carbohydrate digestion Flashcards

1
Q

What are the principal dietary constituents (x6)

A
Carbohydrate
Fat
Protein 
Vitamins
Minerals
Water
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2
Q

How does the body take in water

A

Orally

Through the skin

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3
Q

What are the monosaccharides

A

Glucose, Galactose, Fructose

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4
Q

How many Carbons are in in the monosaccharides

A

Glucose and Galactose = 6

Fructose = 5

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5
Q

What type of sugar is glucose

A

A reducing sugar (it gets oxidised)

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6
Q

What type of sugar is fructose

A

A oxidising sugar (it gets reduced)

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7
Q

Are monosaccharides soluble in water

A

Yes

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8
Q

Where are monosaccharides absorbed

A

The Small Intestine

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9
Q

What are the Disaccharides

A

lactose, Sucrose, Maltose

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10
Q

What monosaccharides make up lactose

A

Glucose and Galactose

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11
Q

What monosaccharides make up sucrose

A

Fructose and glucose

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12
Q

What monosaccharides make up maltose

A

glucose and glucose

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13
Q

What links the monomers of a disaccharide

A

Glycosidic bonds

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14
Q

What is a glycosidic bond?

A

Covalent bond between hydroxyl and anomeric carbon 1 of glucose

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15
Q

Where is maltose found

A

It is the breakdown product of starch

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16
Q

Where is lactose found

A

Main sugar in milk

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17
Q

What is common of maltose and lactose

A

They both have the anomeric carbon available for oxidation and so are REDUCING SUGARS

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18
Q

Where is sucrose found

A

Table sugar

19
Q

What portion of diet is sucrose

A

25%

20
Q

Is sucrose a reducing sugar?

A

No

It does not have an anomeric carbon free so there is no oxidation site

21
Q

What are the 3 polysaccharides

A

Starch
Cellulose
Glycogen

22
Q

What does starch consist of

A

Many glucose monomers linked together

23
Q

What are the two types of starch structures

A

Amylose

Amylopectin

24
Q

What are features of amylose

A

the glucose are in a straight line with a1-4 bonding

Can have 1000s of glucose residues

25
Q

What portion of diet is amylose

A

20-25%

26
Q

What are the features of amylopectin

A

It is branched (every 24-30 residues is attached a1-6)

27
Q

What portion of our diet is amylopetin

A

75-80%

28
Q

Where is cellulose found

A

Plant cell walls

29
Q

What links the monomers in Cellulose

A

B-1,4 glycosidic bonds

30
Q

How is cellulose digested

A

By bacteria in the gut

31
Q

Where is glycogen found

A

Animals (animal storage of glucose)

32
Q

What are the features of glycogen

A

A1-4 linkage with branches every 6-12 residues

33
Q

Where is glycogen found in the body

A

90% liver and muscle

34
Q

How do the proportions of muscle in the liver and muscle vary

A

There is more glycogen in muscle by volume

There is more glycogen in liver by concentration

35
Q

What can pack for glucose: glycogen or starch

A

Glycogen

36
Q

Why store glucose in polymers

A

prevents cells lysing

37
Q

What enzyme initially starts to break down polymers and where

A

Amylase breaks down the A1-4 bonds

In the saliva

38
Q

What isomer of glucose will glucose transporters recognise

A

D-glucose

39
Q

Does amylase operate in the stomach?

A

No - its too acidic

40
Q

What transporter carries glucose and galactose across the enterocytes

A

The SGLUT-1 transports

Sodium dependant hexose transporter

41
Q

How does the sodium exit with cell

A

Via the sodium/potassium pump

42
Q

What transporter carries glucose and galactose out of the enterocytes

A

Glut-2

This is facilitated transport and not active

43
Q

How does fructose enter the enterocyte

A

Through Glut-5 receptor

44
Q

How does fructose leave the enterocyte

A

Through Glut-2