AQA A-Level Biology 3.1.2: Carbohydrates, Tests and Polysaccharides

What is a polymer?

Many monomers joined together

What reaction joins two monomers together?

Condensation

Which reaction breaks down polymers?

Hydrolysis

What type of chemical bond is formed between monomers?

Covalent

What type of bond is formed between monosaccharides?

Glycosidic

What are monosaccharides?

Individual sugar molecules (monomers) that make up disaccharides and polysaccharides

What is the general formula for carbohydrates?

CH2O

What are the three main groups of carbohydrates?

Monosaccharides, Disaccharides, Polysaccharides

What is a disaccharide?

A carbohydrate formed from two monosaccharides

Give an example of a disaccharide and how it forms.

α glucose + α glucose → maltose

What is the bond that forms between two monosaccharides?

Glycosidic bond

What is the process called when a glycosidic bond is broken?

Hydrolysis

What are the two common isomers of glucose?

α glucose and β glucose

What is starch?

A polysaccharide formed from α glucose monomers

What is glycogen?

A polysaccharide that serves as an energy store in animals

What is cellulose?

A polysaccharide formed from β glucose monomers that provides structural support in plants

What type of reaction forms a glycosidic bond?

Condensation reaction

What is the significance of glycosidic bonds in polysaccharides?

They determine the structure and properties of the polysaccharide

What is the role of glucose in carbohydrates?

It can be a source of energy and an energy store

What is the structure of α glucose?

A six-carbon sugar with a specific ring configuration

What is the significance of the carbon numbers 1-4 and 1-6 in polysaccharides?

They refer to the carbon numbers of the two molecules that form the glycosidic bond

What is the process of polymerization in carbohydrates?

The joining of many monosaccharides through condensation reactions

What is the storage carbohydrate found in plant cells?

Starch

What are the two types of polymers that make up starch?

Amylose and amylopectin

What type of glucose is amylose made from?

α-glucose

What is the structure of amylopectin?

Long branched chain due to 1-6 glycosidic bonds.

What is the coiled structure of amylose held together by?

Hydrogen bonds.

How do glycosidic bonds affect the shape of starch?

They produce twisted chains that give a compact shape.

What is the function of starch in plants?

To store excess glucose.

How is starch hydrolyzed?

To release glucose for respiration.

Where is glycogen stored in animals?

In muscles and the liver.

What is the structure of glycogen compared to amylopectin?

More branched than amylopectin.

What type of glucose is glycogen made from?

α-glucose.

What type of glucose is cellulose made from?

β-glucose.

How are cellulose chains linked together?

By hydrogen bonds between glucose molecules.

What type of reaction joins monosaccharides together?

Condensation.

What type of reaction breaks down maltose?

Hydrolysis.

What disaccharide is formed by joining glucose and glucose?

Maltose.

What two monosaccharides make up sucrose?

Fructose and glucose.

What disaccharide is formed by joining glucose and galactose?

Lactose.

What are the three types of polysaccharides that α-glucose can form?

Amylose, amylopectin, glycogen.

What type of reaction breaks polysaccharides apart?

Hydrolysis.

Describe the structure of glycogen.

Polymer of alpha glucose - highly branched.

What are the two structures that make up starch?

Amylose and amylopectin.

What are the differences between starch and glycogen?

Glycogen is always branched; starch is not.

Why are different enzymes needed to digest starch and cellulose?

Different shapes of molecules require different enzymes.

How do cellulose molecules provide strength and support to plant cells?

They form hydrogen bonds to make microfibrils.

What type of glycosidic bonds are found in amylopectin?

1-4 and 1-6 glycosidic bonds.

What is the role of branches in amylopectin?

Increase surface area for enzymes to hydrolyze glycosidic bonds.

What are the two types of glycosidic bonds in carbohydrates?

α glycosidic bonds and β glycosidic bonds

What is the primary storage polysaccharide in plants?

Starch

What is the primary storage polysaccharide in animals?

Glycogen

What is cellulose made from?

Beta-glucose

What type of bond is formed between sugar molecules in disaccharides?

Glycosidic bond

What is the chemical formula for glucose?

C6H12O6

What type of sugar is made up of two sugar units?

Disaccharide

What type of sugar is made up of many sugar units?

Polysaccharide

What is the role of carbohydrates in respiration?

Substrate for respiration - glucose

What type of sugar cannot serve as a reducing agent?

Non-reducing sugar

What is a reducing sugar?

A sugar that serves as a reducing agent, including all monosaccharides and some disaccharides.

What is the structure of starch?

A mixture of two polysaccharides: amylose and amylopectin.

What is the structure of glycogen?

A highly branched polysaccharide made up of alpha-glucose.

What is the structure of cellulose?

Long unbranched straight chains of beta-glucose linked by β-1,4-glycosidic bonds.

What is the function of cellulose in plants?

Provides structural support in cell walls.

What is the difference between α-glucose and β-glucose?

α-glucose forms starch and glycogen; β-glucose forms cellulose.

What reaction breaks down polysaccharides?

Hydrolysis.

What disaccharide is formed from glucose and glucose?

Maltose.

What disaccharide is formed from glucose and galactose?

Lactose.

What disaccharide is formed from glucose and fructose?

Sucrose.

How do the structures of starch and glycogen differ?

Starch is less branched than glycogen.

What is the role of hydrogen bonds in cellulose?

They link cellulose chains together to form strong microfibrils.

What is the significance of the branching in glycogen?

Increases surface area for enzyme action, allowing quick glucose release.

What is the significance of starch being insoluble?

It does not affect water potential in cells.

What type of sugar is a hexose?

A sugar made up of 6 carbon atoms.

What type of sugar is a pentose?

A sugar made up of 5 carbon atoms.

What is the main structural component in arthropod exoskeletons?

Chitin.

What is the role of carbohydrates in cell recognition?

They can be attached to proteins or lipids on the cell surface membrane.

What type of glucose is found in starch?

Alpha glucose.

What type of glucose is found in cellulose?

Beta glucose.

What type of bond is present in starch and glycogen?

Glycosidic bonds.

What type of reaction breaks down carbohydrates into their monomers?

Hydrolysis.

What is one feature of starch that enables it to act as a storage substance?

Starch is insoluble, preventing it from affecting osmotic balance in cells.

What is the main difference in structure between starch and cellulose?

Starch is branched while cellulose is straight and forms fibers.

How are starch molecules adapted for their function in plant cells?

Starch is compact and insoluble, making it an efficient energy storage molecule.

How are cellulose molecules adapted for their function in plant cells?

Cellulose forms strong fibers that provide structural support to plant cell walls.

What are the monomers that form a cellulose molecule?

Beta-glucose.

What type of reaction converts cellulose to its monomers?

Hydrolysis.

What gives cotton its strength?

The strong hydrogen bonds between cellulose fibers.

Name one polysaccharide other than starch found in plant cells.

Cellulose.

What is the primary role of glycogen in animals?

Energy storage.

What is the primary role of cellulose in plants?

Structural support.

What type of glucose is found in glycogen?

Alpha glucose.

What is the difference between alpha and beta glucose?

Alpha glucose has the hydroxyl group on the first carbon below the plane, while beta glucose has it above.

What is the significance of glycosidic bonds in carbohydrates?

They link monosaccharides to form disaccharides and polysaccharides.

What is the solubility of starch in water?

Starch is generally insoluble in water.

What is the solubility of cellulose in water?

Cellulose is insoluble in water.

How does the branching of starch affect its function?

Branching allows for rapid release of glucose when energy is needed.

What is the primary structural difference between amylose and amylopectin?

Amylose is unbranched, while amylopectin is branched.

What is a polysaccharide found in cells other than starch?

Glycogen or cellulose

What is one advantage of storing starch rather than glucose in potato cells?

Starch is insoluble, preventing changes in water potential.