Polysaccharides

What are the elements of Carbohydrates?

Carbon, Hydrogen and Oxygen

What is the general formula of monosaccharides ?:

1. (CH2O)n’

2. (CHO2)n’

3. (C2HO)n’

1. (CH2O)n’

Monosaccharides

Simple sugars containing three to seven carbon atoms

What are 3 examples of Monosaccharides

• Glucose

• Galactose

• Fructose

Where is galactose, fructose and sucrose found?

• Galactose is found in milk.

• Fructose is found in fruit.

• Sucrose is found is common table sugars.

What kind of sugar is glucose and what is the chemical formula?

It is a hexose sugar with a chemical formula of C6H1206.

Why is glucose important?

During cellular respiration, the energy released from glucose helps to make Adenosine triphosphate (ATP) which is an important source of energy for all cellular functions in humans.

What are beta- and alpha-glucose called?

Isomers

Isomers

Same molecular formula but different arrangement of atoms in space.

How do the arrangements of the alpha- and beta-glucose differ ?

The -OH groups are in a different orientation around C1-

How are the alpha- and beta-glucose molecular formula similar?

They are both six-carbon sugars and have six carbon atoms numbered from 1-6.

What disaccharide is produced from two glucose monomers in a condensation reaction?

Maltose

What disaccharide is produced from glucose and fructose in a condensation reaction?

Sucrose

What disaccharide is produced from glucose and galactose in a condensation reaction?

Lactose

What is the name of a common problem called in which the body is unable to digest lactose?

Lactose intolerance

What bond joins monosaccharides together by condensation reaction?

Glycosidic bond

How many glycosidic bonds does maltose, sucrose and lactose have?

• Maltose= 1 to 4

• Sucrose= 1 to 2

• Lactose= 1 to 4

What are 3 examples of polysaccharides?

Starch, glycogen, cellulose and chitin

What solution test for reducing and non-reducing sugars ?

Benedicts Reagent

Reducing sugars

Reduces benedicts solution by donate electrons, which changes the benedicts solution colour and gives a precipitate depending on how much is reduced.

What are examples of reducing sugars?

• Glucose

• Fructose

• Maltose

Non reducing sugars

Cannot donate electrons, so it does not react with Benedict's reagent unless it is broken down into monosaccharides in a second test.

If a Non-reducing sugar is broken into monosaccharides and benedicts solution still remains blue what does that mean?

No sugars are present

What are the 3 steps for reducing sugars?

1. Dissolve sample and pour into a boiling tube

2. Add equal amounts of benedicts reagent into the boiling tube

3. Heat the boiling tube in a water bath

What are the 3 steps for a non-reducing sugar?

1. Add dilute HCL ( hydrolysis ) to dissolved sample and boil

2. Add sodium hydrogen carbonate (neutralise)

3. Repeat the Benedict's test

What is an example of a non-reducing sugar?

Sucrose

What are polysaccharides?

Very large insoluble molecules which consists of long chained monosaccharides during condensation reaction

What are examples of Polysaccharides?

Starch, glycogen, cellulose, chatting.

What is starch?

Starch is a large insoluble polysaccharide made of amylopectin and amylose which is used for storing energy such as glucose in plants and a food source for humans and animals.

Where is starch stored and how is it used for energy?

It is stored in seeds of plants where is it broken down into glucose by plants when in need of energy.

How does starch affect water potential?

Starch does not change water potential in a cell because its insoluble in water which means water is not drawn into the cells by osmosis.

Why is starch a good storage molecule?

• It is compact so a lot can be stored

• To large so it can’t be diffused out of cells

• It can be easily broken down into glucose for energy during respiration

• Insoluble in water which avoids the need for the cell to maintain osmotic balance to prevent cell lysis

Branched amylopectin

Long alpha-glucose chain which has many ends, each of which can be acted on by emsymes simultaneously for rapid break down into glucose.

What type of glucose is Starch made of?

Alpha - glucose monosaccharides

Unbranched amylose

Long alpha-glucose chain wound in tightly compacted coils due to the angle of the glycosidic bonds which is ideal for storage as there is more space.

Iodine test

Test for the presence of starch in a sampme

What is the iodine solution made of ?

A solution of dissolved iodine in potassium iodide

How to test for the presence of star h in a solution?

• Step 1: place small sample in the spotting tile dimple or boiling tube

• Step 2: add few drops of iodine solution and observe colour change

If starch is present the solution changes from a browny-orange to blue-black.

Cellulose

Straight long unbranched beta-glucose chains linked by hydrogen bonds to form strong microfibrils to provide structural support for cells

What is a similar polysaccharide that stores glucose for animals and human cells?

Glycogen

Glycogen

Very compacted long branched alpha-glucose chain, (more branches than amylopectin) allowing stored glucose to be released at a quick rate for energy during the process of glycogenolysis

What part of a plant cell cell is mostly made of cellulose?

The cell walls

Why is glycogen a good storage molecule?

• Unbranched allows for a rapid process of glycogenolysis to provide energy

• Very compact which allows for large amounts to be compacted