Bio - Biological Molecules

Carbohydrates, lipids, proteins, nucleic acids, ATP, water and inorganic ions

What are the key molecules that are required to build structures that enable organisms to function?

• Carbohydrates

• Proteins

• Lipids

• Nucleic acids

• Water

What is a monomer?

Smaller units from which larger molecules are made

What is a polymer?

Molecules made from large numbers of monomers joined together in a chain during a process called polymerisation

What are two important reactions that occur to form covalent bonds in molecules?

• Condensation reactions

• Hydrolysis reactions

What is a condensation reaction?

A reaction that occurs when monomers combine by covalent bonds to form polymers or macromolecules, and water is removed

What does hydrolysis mean?

“lyse” = to break

“hydro” = with water

What happens in a hydrolysis reaction?

In the hydrolysis of polymers, covalent bonds are broken when water is added.

What is a monosacharride?

A single reducing sugar monomer

What elements do all carbohydrates contain?

• Carbon

• Hydrogen

• Oxygen

What are some examples of monosacharrides?

• Glucose

• Fructose

• Deoxyribose

What do monosacharrides join together to form?

• Disacharrides 

• Polysacharrides

How can sugars be classified and why?

• Reducing

• Non-reducing

Classification into these groups is dependent on the sugars ability to donate electrons

Can reducing sugars donate electrons?

yes

Can non-reducing sugars donate electrons?

No

How do you test for reducing sugars?

Add benedict’s solution and heat

blue > green > yellow > orange > brick red

What are some examples of reducing sugars?

• Glucose

• Fructose

• Galactose

Fructose and galactose have the same molecular formula as glucose however, they have a different structural formula

How do you test for non-reducing sugars?

1) Test using benedict’s solution - if negative…

2) Boil with concentrated acid to hydrolyse the glycosidic bond

3) Neutralise the acid with a base

4) Test again with benedict’s solution and heat - if positive, non-reducing sugars are present… if negative again, there is no sugar at all.

What is an xample of a non-reducing sugar?

Sucrose

What are the two forms of glucose?

• Alpha

• Beta

Where is the hydroxyl (OH) groups on carbon 1 located in alpha glucose?

Below the ring

Where is the hydroxyl (OH) groups on carbon 1 located in beta glucose?

Above the ring

What is a disacharride?

Two monosaccharides joined together with a glycosidic bond with a biproduct of water

What is a polysaccharide?

Many monosaccharides joined together with a glycosidic bond with a biproduct of water

What are 3 examples of polysaccharides?

• Starch

• Glycogen

• Cellulose

What type of glucose is starch made from?

Alpha glucose

What type of glucose is glycogen made from?

Alpha glucose

What type of glucose is cellulose made from?

Beta glucose

How are disaccharides and pilysaccharides formed?

When two hydroxyl (-OH) groups (on different saccharides) interact to create a strong covalent bond called the glycosidic bond

What is maltose made up of?

2 alpha glucose molecules

What is sucrose made up of?

An alpha glucose molecule and a fructose molecule

What is lactose made up of?

An alpha glucose molecule and a galactose molecule

How is a glycosidic bond broken?

When water is added in a hydrolysis reaction

What are some examples of disaccharides?

• Maltose

• Sucrose

• Lactose

What is starch?

The storage polysaccharide of plants

How is starch stored?

As granules in plastids (e.g. chloroplasts)

Why does starch take longer than glucose to be digested?

Because there are many monomers in it

What 2 polysaccharides is starch constructed from?

• Amylose

• Amylopectin

What is glycogen?

The storage polysaccharide in animals and fungi

What is the structure of glycogen?

Highly branched structure

What does glycogen’s highly branched structure do?

• Makes glycogen more compacts, which helps animals to store ore of it

• Branching enables more free ends where glucose molecules can be added or removed allowing for condensation and hydrolysis reactions to occur more rapidly.

Where is cellulose found?

In plant cells

What gives cellulose its strength?

The inversion of beta-glucose molecules means that many hydrogen bonds form between the parallel chains of microfibrils

What is the main function of cellulose?

It is the main structural component of cell walls

What is a microfibril?

A very fine fibril, or fibre-like strand, consisting of glycoproteins and cellulose

What is good about the strangth of cellulose?

The high tensile strength of cellulose allows it to be stretched without breaking, which makes it possible for cell walls to withstand turgor pressure

Are cellulose fibres permeable?

Yes, Cellulose fibres are freely permeable, which allows water and solutes to leave or reach the cell surface membrane

How do you test for starch?

1) Add a few drops of iodine solution

2) If starch is present iodine with go from orange/brown to blue/black