Starch Structure and Formation

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Questions and Answers

What is the percentage of amylose in a starch granule?

80-85%

90-95%

5-10%

15-20% (correct)

What type of bonds link glucose units together in amylose?

β 1-4 glycosidic bonds

α 1-4 glycosidic bonds (correct)

α 1-6 glycosidic bonds

β 1-6 glycosidic bonds

What is the structure of amylose?

Rings

Branched chains

Non-branching helical structure (correct)

Linear structure

What is the percentage of amylopectin in a starch granule?

80-85% (A) Signup and view all the answers

What is the structure of amylopectin?

Branched chains (C) Signup and view all the answers

What is the inner layer of a starch granule called?

Amylose (D) Signup and view all the answers

What is the outer layer of a starch granule called?

Amylopectin (A) Signup and view all the answers

What is another name for starch?

Glucosan (D) Signup and view all the answers

What is the structural formula of sucrose?

[α -D-Glucose (a-1 → 2) β -D-Fructose] (D) Signup and view all the answers

What is a characteristic of sucrose?

It is a non-reducing sugar. (D) Signup and view all the answers

What is the classification of glycogen?

Homopolysaccharide (D) Signup and view all the answers

What is the source of sucrose?

Cane and beet sugar (C) Signup and view all the answers

What is the characteristic of hyaluronic acid?

It yields different sugar units. (A) Signup and view all the answers

What is the type of polysaccharide that yields different sugar units on hydrolysis?

Heteropolysaccharide (C) Signup and view all the answers

What is the function of cellulose?

Structural support (C) Signup and view all the answers

What is the type of polysaccharide that yields the same type of monosaccharide units on hydrolysis?

Homopolysaccharide (D) Signup and view all the answers

What is the type of bond that links glucose units in starch?

α 1-4 glucosidic bonds (C) Signup and view all the answers

What is the storage form of carbohydrates in humans and animals?

Glycogen (A) Signup and view all the answers

What is the type of bond that links glucose units in cellulose?

β 1-4 glucosidic bonds (C) Signup and view all the answers

What is the reaction that breaks down starch into smaller molecules?

Partial hydrolysis (B) Signup and view all the answers

What is the characteristic of glycogen that distinguishes it from starch?

It is a highly branched chain of homopolysaccharides (A) Signup and view all the answers

What is the color produced when iodine reacts with starch?

Blue (A) Signup and view all the answers

What is the characteristic of cellulose that distinguishes it from starch?

It is a long, straight non-branching chain (D) Signup and view all the answers

What is the color produced when iodine reacts with glycogen?

Red (B) Signup and view all the answers

How many glucose units are linked together in each chain of amylopectin?

24-30 glucose units (D) Signup and view all the answers

What type of glycosidic bonds are found at the branching point in amylopectin?

α 1-4 and α 1-6 glycosidic bonds (C) Signup and view all the answers

What is the significance of amylopectin in the human body?

It is the most important food source of carbohydrates (D) Signup and view all the answers

What is the general structure of amylopectin?

A branched chain of glucose units (A) Signup and view all the answers

What is the role of α 1-4 glycosidic bonds in amylopectin?

They link the glucose units together in a linear chain (A) Signup and view all the answers

What is the function of the branching points in amylopectin?

They allow for the formation of a more complex structure (A) Signup and view all the answers

What is the relationship between the glucose units in amylopectin?

They are linked together in a 1-4 and 1-6 ratio (D) Signup and view all the answers

What is the characteristic of the glycosidic bonds in amylopectin?

They are only α type (D) Signup and view all the answers

What is the main component of the framework of plants?

Cellulose (D) Signup and view all the answers

What is the reason cellulose is not digested by many mammals, including humans?

Due to the absence of hydrolase enzymes that can attack β-linkage (D) Signup and view all the answers

What is the effect of cellulose on stool?

It increases the bulk of the stool (A) Signup and view all the answers

What is the result of cellulose on intestinal movement?

It stimulates the intestinal movement (B) Signup and view all the answers

What is the effect of cellulose on constipation?

It prevents constipation (D) Signup and view all the answers

What is the property of cellulose in relation to iodine?

It gives no color with iodine (D) Signup and view all the answers

What is the solubility of cellulose in water?

It is insoluble in water (D) Signup and view all the answers

What is the type of bond that strengthens the chains of cellulose?

Hydrogen bond (C) Signup and view all the answers

Study Notes

Sucrose

Structure: α-D-Glucose (α-1 → 2) β-D-Fructose
Source: Cane and beet sugar
Properties:
Not a reducing sugar
Cannot exist in α and β forms
Does not show mutarotation
Cannot form osazone crystals

Polysaccharides

Definition: Carbohydrates formed of more than 10 sugar units
Classification:
Homopolysaccharides: contain repeated same sugar units (e.g. glycogen)
Heteropolysaccharides: contain repeated different sugar units (e.g. hyaluronic acid)

Homopolysaccharides

Examples:
Starch
Glycogen
Cellulose
Inulin
Chitin

Starch

Structure:
Inner layer (amylose): non-branching helical structure of glucose units linked by α 1-4 glycosidic bonds
Outer layer (amylopectin): branched chains of glucose units linked by α 1-4 and α 1-6 glycosidic bonds
Source: Most important food source of carbohydrates (found in cereals, potatoes, legumes, and other vegetables)
Properties:
Gives blue color with iodine
Amylopectin gives red color with iodine
Partial hydrolysis by amylase gives various forms of dextrins

Glycogen

Structure: Highly branched chain of homopolysaccharides
Source: Storage form of carbohydrates in humans and animals (synthesized and stored in liver, muscles, and tissues)
Properties:
Gives red color with iodine

Cellulose

Structure: Long, straight non-branching chain of glucose units (β-D-glucopyranose) linked by β 1-4 glucosidic bonds
Source: Chief constituent of the framework of plants, leaves, vegetables, fruits, wood, cotton, etc.
Properties:
Does not give color with iodine
Insoluble in water
Cannot be digested by many mammals, including humans, due to absence of hydrolase enzymes that can attack β-linkage
Importance in diet: increases bulk of stool, stimulates intestinal movement, and prevents constipation

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Description

This quiz covers the structure and formation of starch, including the inner and outer layers, amylose, and glucose units linked by glycosidic bonds.