2.2.2 Monomers & Polymers Flashcards
Monomers & Polymers
There is a massive variety of life within and between organisms, however the biochemical basis of life is similar for all living things
They key molecules that are required to build structures that enable organisms to function are:
- carbohydrates
- proteins
- lipids
- nuclei acids
- water
Monomers are the smaller units from which larger molecules are made
Polymers are molecules made from a large of monomers joined together in a chain
Carbon compounds can form small single subunit (monomers) that bond with many repeating subunits to form large molecules (polymers) by a process called polymerisation
Macromolecules are very large molecules
- they contain 1000 or more atoms and so have high molecular mass
- polymers can be macromolecule, however not all macromolecules are polymers as the subunits of polymers have to be the same repeating units
Covalent Bonding
A covalent bond is the sharing of two or more electrons
- the electrons can be shared equally forming a non polar covalent bond or unequally (where an atom can be more electronegative - delta -) to form a covalent bond
Generally, each atom will form a certain number of covalent bonds due to the number of free electrons in the outer orbital
- e.g. H=1 bond, C=4 bonds
Covalent bonds are very stable as high energies are required to break bonds
Multiple pairs of electrons can be shared forming double bonds (e.g. unsaturated fats C=C) or triple bonds
When two monomers are close enough that their outer orbital overlap this results in their electrons being shared and a covalent bond forming
If more monomers are added then polymerisation occurs (and/or a macromolecule forms)
Condensation
Also known as dehydration synthesis (‘to put together while losing water’)
A condensation reaction occurs when monomers combine together by covalent bonds to form polymers (polymerisation) or macromolecules (lipids) and water is removed
Hydrolysis
Hydrolysis means:
- ‘lyse’ - to break
- ‘hydro’ - with water
In hydrolysis of polymers , covalent bonds are broken and water is added
Chemical Elements in Biological Molecules
Carbohydrates, lipids, proteins and nucleic acids contain the chemical elements carbon (C) and hydrogen (H), making them organic compounds
Carbon atoms are key to organic compounds because:
- each carbon atom form 4 covalent bonds - this makes the compounds very stable (as covalent bond are so strong that they require a large input of energy to break them)
- carbon atoms can from covalent bonds with oxygen, nitrogen and soulful
- carbon atoms can from straight chains, branches chains or rings
Carbohydrates
All carbohydrates contain the chemical elements C, H and O
As H and O atoms are always present in the ratio 2:1 (e.g. water H2O, which is where ‘hydrate’ in ‘carbohydrate’ comes from) they can be represented by the formula Cx(H2O)y
The 3 types of carbohydrates are monosaccharides,disaccharides and polysaccharides
Carbohydrates have many different functions:
- source of energy - e.g. glucose is used for energy-release during cellular respiration
- store of energy - e.g. glycogen is stored in the muscles and liver of animals
- structurally important - e.g. cellulose in the cell walls of plants
Types of Carbohydrates - Monosaccharide
Definition:- single sugar monomer, all are reducing sugars
Examples include:
- glyceraldehyde (3C)
- ribose (5C)
- glucose (6C)
Function: - source of energy in respiration
- building blocks for polymers
Types of Carbohydrates - Disaccharide
Definition: - a sugar formed from 2 monosaccharides joined together by a glycosidic bond in a condensation reaction
Examples include:
- maltose (alpha glucose + alpha glucose)
- sucrose (alpha glucose + fructose)
- lactose ( alpha glucose + beta glucose)
Function: - sugar found in germinating seeds (maltose)
- mammal milk sugar (lactose)
- sugar stored in sugar cane (sucrose)
Types of Carbohydrates - Polysaccharides
Definition: - a polymer formed by many monosaccharides joined by glycosidic bonds in a condensation reaction
Examples include:
- cellulose (beta glucose)
- starch (alpha glucose in the form of amylose and amylopectin)
- glycogen (alpha glucose)
Function: - energy storage ( starch in plants and glycogen in animals)
- structural (cell wall)
Lipids
All lipids contain the chemical elements C, H and O
- however, the proportion of O in lipids is low compared to carbohydrates
There are many types of lipids, including:
- triglycerides (fats and oils)
- phospholipids
- waxes
- steroids (such as cholesterol)
Lipids have many different functions:
- source of energy that can be respired (lipids have a high energy yield)
- store of energy e.g. lipids are stored in animals as fats in adipose tissue and in plants as lipid droplets
- insulating layer e.g. thermal insulation under the skin of mammals and electrical insulation around nerve cells
- an essential component of biological membranes
Proteins
Like carbohydrates and lipids, all proteins contain the chemical elements C, H and O
- however, all proteins also contain N (nitrogen) and some proteins contain S (sulphur)
Proteins have many different functions:
- required for cell growth, cell repair and the replacement of biological materials
- structurally important, e.g. in muscles, collagen and elastin in the skin, collagen in bone and keratin in hair
- proteins can also act as carrier molecules in cell membranes, antibodies, enzymes or hormones
Nucleic Acids
Like carbohydrates, lipids and proteins, all nucleic acids contain the chemical elements C, H and O
- however, all nucleic acids also contain N (nitrogen) in their bases and P (phosphorus) in the form of phosphate groups
Nucleic acids (DNA and RNA) have one function:
- carrying the genetic code in all living organisms
- nucleic acids are essential in the control of all cellular processes, including protein synthesis
