Unit 13

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  • Created on: 19-09-18 19:31

Unit 13




It is a nucleic acid or polynucleotide that contains a deoxyribose sugar unit

Carrier of genetic information that builds organisms

It is made by two polynucleotide chains that lie along side each other

The two strands twist around each other to form a double helix 

The two strands are joined together by hydrogen bonds making DNA stable

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RNA is used in translation and transcription 

It is a single stranded molecule

The pentose sugar in the nucleotides is ribose 

Cells access the information stored in DNA by creating RNA to direct the synthesis of proteins through the process of translation

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nucleotides are monomers that bond together to form the nucliec acid polymer

They join together by a condensation reaction

This reaction takes place between the -OH functional group from the phosphate group of one nucleotide and the hydrogen from the -OH group on carbon 3 of the sugar of another nucleotide 

They also have functions related to cell signalling, metabolism and enzyme reactions

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Are a form of lipids found in cell membranes

They are made when one molecule of gylcerol bonds with two fatty acids and one phosphate group through a condensation reaction

Phospholipids have a negatively charged phosphate group which is soluble in water

They have an uncharged hydrocarbon chain which is soluble in water

this dual solubility allows phospholipids to form cell membranes 

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This is a type of lipid used for energy storage, insulation and protection

They are found in fatty tissue under the skin and surrounding the organs

Tryglycerides are soluble in water 

A tryglyceride molecule is made when one molecule of gylcerol joins together with three fatty aicd molecules. The three -OH functional groups of the gylcerol molecule form bonds with the acid functional groups of three fatty aicds.

These three new bonds are called ESTER BONDS

The reaction is a condensation reaction as water is made

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A polypeptide is a string of amino acids linked together

Amino acids are the basic building blocks of protein

Due to each amino acid having a unique R group, a particular amino acid sequence creates a polypeptide whose function is dependent upto its chemcial structure

Most commonly they are used for:

  • proteins 
  • transporters 
  • enymes
  • hormones
  • structure 
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Alpha Glucose

Starch is formed from alpha glucose

Alpha-glucose is a form of glucose that is in a ring shape

The ring shaped glucose structures occur when the hydroxyl OH group on the carbon 6 atom reacts with the aldehyde group on the carbon 1 atom. A water molecule is removed meaning it is a condensation reaction 

Alpha   H



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Beta glucose 

Cellulose is made of beta glucose 

Beta    OH



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It is a natural polymer

Cellulose is the main substance found in place cell walls and helps the plant to remain strong

humans cant digest cellulose 

The molecule consists of carbon, hydrogen and oxygen atoms

Composed of a long chain of glucose molecules 

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This is a multibranched polysaccharide of glucose 

It serves as a form of energy storage in humans, animals, fungi and bacteria

it is mainly stored in the liver and muscles to provide the body with a readily available source of energy if blood glucose levels decrease

The polysaccaride structure represents the main storage of glucose in the body

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Starch is energy store compound in plants

It is made of alpha glucose 

There are two types of starch straight and branching 

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Amino Acids

Amino Acids are made of the 5 elements carbon, hydrogen, oxygen, nitrogen and sulfur

There is a central carbon atom called the alpha carbon with four chemical groups attached to it

  • a hydrogen atom
  • an amino group
  • a carboxylic group
  • a variable R group

There are 20 different R groups meaning there are 20 different amino acids

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Fatty acids

Saturated fatty acids

  • form straight chains meanig they can line up against each other easily forming attractions between all the molecules
  • The attractions require lots of energy to overcome them, as a result of this they have a high melting point and are solids at room temp
  • Saturated fatty acids have a carboxylic group at the end


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Fatty acids

Unsaturated fatty acids

  • they form bent chains unlike saturated fatty acids and have a double bond
  • their shape means they push away from each other so attractions are not strong
  • they have low melting points and are liquids and room temp
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