Carbohydrates Flashcards by Amarachi Umezurike

What do all polysaccharides have in common?

They contain many (more than 10) monosaccharides linked by glycosidic bonds.

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Most carbohydrates found in nature occur as?

polysaccharides, polymers of medium to high molecular weight (Mr >20,000).

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Polysaccharides, also called ……….?

Glycans

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How do polysaccharides differ from each other in the identity of their recurring monosaccharide units?

The lengths of their chains,
Types of bonds linking the monosaccharide units,
The degree of branching.

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Polysaccharides are classified into?

Homopolysaccharides and Heteropolysaccharides

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Differentiate between the classes of polysaccharides

Homopolysaccharides are formed by the same kind of monosaccharides; eg’s starch, glycogen and cellulose. Each of them are formed by hundreds of molecules of glucose linked by glycosidic bonds.
On the other hand, the polysaccharide molecules of heteropolysaccharides are formed by different kinds of monosaccharides.

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Examples of heteropolysaccharides

Hyaluronic acid
Chondroitin sulfate
Heparin
Keratan sulfate
Dermatan sulfate.

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What is hyaluronic acid formed from?

It is formed by thousands of alternating units of N-acetyl glucosamine and glucuronic acid.

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What are inulins?

Inulins are polymers composed mainly of fructose units, and typically have a terminal glucose.

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Why is inulin not digested by enzymes in the human GIT?

Because of the β(2,1) linkages

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List features of inulin

Inulins are polymers composed mainly of fructose units, and typically have a terminal glucose.

They are linked by β(2,1) glycosidic bonds.

Standard inulin is slightly sweet

It is soluble in water.

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What is the application of inulin in Renals?

Used to determine glomerular filtration rate (kidney fxn)

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Classify polysaccharides on the basis of structure/linkages of the monosaccharides

i) Branched polysaccharides

ii) Unbranched/Linear polysaccharides

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Amylose and cellulose and cellulose are examples of ………?

Unbranched/Linear polysaccharides

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Examples of branched polysaccharides are?

Starch and glycogen

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Non digestible polysaccharides include:

Fibres; Soluble fibre and Insoluble fiber

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Digestible polysaccharides include

Starch (Amylose, Amylopectin)
Glycogen

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Characteristics of starch

3000 monosaccharides
Contain alpha bonds
High Glycemic Index

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Differentiate between amylose and amylopectin

Amylose
- Consistsof long unbranched polysaccharide chains (straight chain)
- More resistant to digestion

Amylopectin
- Consists of branched polysaccharide chains.
- Easier to digest

Plants store glucose in chains of ……..

Starch

Possible benefits of amylose include;

May improve health of digestive tract
May improve glucose tolerance
May stimulate growth of beneficial intestinal bacteria

List 7 features of amylose

It is a linear homopolysaccharide
It is made up of D-glucose units linked by α 1,4- glycosidic bonds
Insoluble in water
Gives blue colour with iodine
Forms the outer layer of the starch granule
Composes about 30% of the granule
Hydrolysis by α-amylase

List 8 features of Amylopectin

It is a branched homopolysaccharide (see structure)
It is made up of D-glucose units linked by α- 1,4- glycosidic bonds at the linear chains and α- 1,6-glycosidic bonds at the branches
Insoluble in water.
Gives red-violet colour with iodine
Forms the inner layer of the starch granule
Composes about 70% of the granule
Linear chains hydrolysed as in amylose but α-1,6-bonds are hydrolyzed by by α-1,6-glucosidase
Amylopectin shows a branch at each 24-30 units of glucose.

What are fibres?

Non-digestible polysaccharides that provide no energy

What’s the difference between soluble and insoluble fibres?

Soluble fibres are easily fermented by intestinal bacteria, while Insoluble fibres are not easily fermented.

Examples of insoluble polysaccharides include;

Cellulose, lignin, some hemicelluloses

Examples of soluble polysaccharides include;

Pectins, beta-glucan, some gums, mucilage

What are the health benefits of soluble fibres?

- Slow gastric emptying and may delay absorption of some nutrients - Helps reduce serum cholesterol - Improve appetite control - Normalize blood glucose levels - May help protect against colon cancer

What is the health benefit of insoluble fibres?

Relieves constipation

Why is cellulose am insoluble fibre?

Because we lack the cellulase enzyme to hydrolyze the β(1→4) glycosidic bond.

Cellulose can be hydrolyzed by ………..

the intestinal bacteria in cattle and other ruminants which have the enzyme cellulase (β-glucosidase).

7 features of cellulose include:

This glycosidic bond configuration changes the three-dimensional shape of cellulose compared with that of amylose. The chain of glucose units is straight. This allows chains to align next to each other to form a strong rigid structure. Cellulose is a linear homopolysaccharide of D-glucose units found in the cell wall of plants (structural fxn) It constitutes the strength and framework of plants Glucose units are linked by β-1,4- glycosidic bonds Bonds are resistant to acid hydrolysis and glucosidases in the GIT (not digestible) in humans and other higher animals. Can be hydrolyzed by the intestinal bacteria in cattle and other ruminants which have the enzyme cellulase (β-glucosidase).

What is a good source of cellulose?

Whole grains.

Why is cellulose important in our diet?

Cellulose is important in our diet because it assists with digestive movement in the small and large intestine.

Partial hydrolysis of cellulose with strong mineral acids yields ……..?

Cellobiose.

………… is an important source of “bulk” in the diet

Cellulose

Chitin is made up of a modified β-D-glucose called ………..

N-acetylglucosamine with β(1→4) glycosidic bonds.

What is the function of chitin in wound healing?

As a surgical thread that biodegrades as a wound heals.

How is chitin utilised in cosmetics?

When ground, chitin becomes a powder that holds in moisture, and it can be added to cosmetics and lotions.

What is the function of chitin in insects’ exoskeletons?

serves to protect them from water. Because of this property, chitin can be used to waterproof paper.

Describe glycogen in 3 sentences

It is a storage glucose in animal tissues (mainly found in the liver (400 kcal) and muscles (1400 kcal) Glycogen is a branched homopolysaccharide composed of D-glucose units linked by α- 1,4- glycosidic bonds at the linear chains and α- 1,6- glycosidic bonds at branches. Its structure is similar to amylopectin but with more complex branching Hydrolyzed by α- amylase and α-1,6-glucosidase to yield maltose and glucose. Glycogen shows a branch at each 8-10 units of glucose

Glycogen shows a branch at each ……. units of glucose?

8 -10

Glycogen is hydrolysed by ………….. to yield ……………

Glycogen is hydrolysed by α- amylase and α-1,6-glucosidase to yield maltose and glucose.

What organs is glycogen stored in?

liver and muscle

……… is a storage form of glucose in animals?

Glycogen

How does liver glycogen response to blood glucose (BG) levels

Low BG leads to glycogen breakdown, which in turn increases blood glucose.