F212 Water (Biological Molecules)

The propities of wate and everything you need to know!

  • Created by: harry
  • Created on: 23-10-11 14:37

F212- Biological Molecules (Water)


Is a smal molecule: 2 hydrogen atoms and one oxygen atom, These are COVALENTLY bonded 

O2 is larger than the H2 and so the oxygen pulls the electrons closer towards it, and so becomes (slightly negative) and so hydrogen is (slightly postive)

These slight charges attract one another, and so form a WEAK bond hydrogen bonds! (these can be formed and broken contnually!)

H bonds are found in many things **** as: Water, carbohydrates and protiens.

Propities of water!:

High boilng point: the breaking and forming of h2 bonds, makes water a liquid not a gas, therefore difficult for water molecules to escape so boiling point is higher.

1 of 12

Water continued :)

Low density of ice: As water is cooled, molecules slow down, and so h2 bonds form holding the water molecules, and creating a cyrstal like structure, which makes it less dense, and so ice floats, which insulates orangisms beneath.

Thermostable: As the h2 bonds prevent the water olecues from moving, ths means that water is thermostable, and so large ammount of energy is needed to increase the temperature, and so has a specifc heat capacity

Vaporisation: Evaporation requires a lot of energy and so when water evapourates from a surface it "removes" the heat and has a coolig effect. (sweating)

Cohesion: The h2 bonds causes water molecules to "stick together" and so causes surface tension and so some organsims can "walk on water"

Solvent: Any polar molecule can dissovle in water, as they are also charged.Some parts will become negative and others positive. This allows metabolic reactions such as respiration and photosynthesis.

2 of 12

F212 Biological Molecules (Carbohydrates)

Condensation Reaction:

Larger molecules are formed, new COVALENT BOND is FORMED, Water molecule REMOVED!

Hydrolysis Reaction:

SMALLER molecules formed, COVALENT BOND is BROKEN Water molecules is ADDED!

Monomers: (one) meaning single and small. Monomers joined together for Polymers!

Carbohydrates: Monomer: Monosachrids Polymer: Polysachrides

Proteins:Monomer: Amino Acids, Polymer:Polypeptides/Protiens

Nucleic Acids:Monomers: Nucleotides, Polymers: DNA RNA

3 of 12

F212 Biological Molecules: Carbohydrates

CarbOHydrates consist of: Carbon, Hydrogen and Oxygen


Energy Source (glucose in respiration), Energy Store(starch), Structure: Cellulose

Monosaccharides: (glucos, fructose, ribose)

These can form together to make disaccharides (double sugars) and polysaccharidest (polymers) Functions: Soluble in h2o, sweet tasting, forms crystals

Pentose sugars: 5 carbons (Ribose) Hexose sugars: 6 carbons (glucose and fructose) (C6 H12 O6) and are ISOMERS (different structires to each other)

Beta and Alpha Glucose:)

4 of 12

F212 Biological Molecules Carbohydrates continued

Two monosaccharides form a Dissaccharids! This is forme by a CONDENSATION REACTION!!! Covalent bond is GLYCOSIDIC BOND and water is formed.

When a disacchride or polysacchrides are broken down inot monomers it is known as a HYDROLYSIS REACTION. Covalent ond GLYCOSIDIC BOND is BROKEN, Water is ADDED!

Polymers (Polysaccharides)

2 A glucose bond together via condensation reaction, form a dissacharide (double sugar) known as maltose, the bond is between the 1 and 4 carbon adjacent ring. so bond is 1,4 GLYCOSIDIC BOND Maltose continuses to join to other A glucoses untill there are thousands, forming a long polymer called amylose.

Startch(energy store in plants) made from two polymers;

Amylose: Polymer of A glucose, joined by 1,4 carbon glycosidic links, to form a coiled chain.

5 of 12

F212 Biological Molecules Carbohydrates Energy sto

Amylopectin: is ranched and coiled, joined by glycosidic links by 1 and 6. Using A glucose. (This has quicker energy source, more released at the same time)

Glycogen: Energy store in Animals.

Glyogen is also a polymer, by A glucose, joined by 1,4 glycosidc bonds, and is coiled.

Many side chains are attached to the coiled chains, by 1,6 glycosidic links Therefore glycogen is HIGHLY MORE COMPACT THAN STARCH. Glycogen is stored in the liver and muscels cells as glycogen granules.

The properties of Startch and Glycogen: INSOLUBLE: therefore they dont reduce the water potenil and effect water movement (osmosis)

LONG CHAINS OF GLUCOSES: They are held together, so they can be readily broken when required during respiration.

6 of 12

F212 Biological Molecules Carbohydrates Structual

Structural Carbohydrates: CELLULOSE (PLANTS)

Cellulose is an insolube polysacchrides, made from long straight chains of B glucose. joined by 1,4 glycosidic bonds. Parallel chains of B glucoses link together through H2 bonds, between the -OH groups to form bundles, like microfibrils, which are very strong and support the cell wall from bursting so becomes turgid. Cellulose cant e digested by animals because they dont have the appropiate enzymes.


Large molecules: Made up of C,H,O,N&S

Functions: Structual function: myosin in the muscles. Enzymes: Are made from proteins. Some Hormones are are protiens (Insulin) Antibodies in the immune response, are made form protiens.

Protiens: are used in structual components and are used as growth and repair, really IMPORTANT as Enzymes that control metabolic reactions (respiration)

7 of 12


Amino acids:

Are monomers, and join together to make a protien, They contain C,H,O&N

There are 20 types of amino acids, each amino acid has a similar structure, yet it is the R GROUP on the central carbon EG: Glycine has a R GROUP of H2. Some of the R GROUPS are charged (polar) and so are HYDROPHILIC, However some are non polar and therefore HYDROPHOBIC!

All amino acids have:

An Amine group -NH2, A carboxylic acid group COOH and a central carbon with a  variable R group attached.

Formation of Dipeptides and polypeptides:Amino acids are all joined in the same way. When a CONDENSATION REACTION occurs between the CARBOXYLIC ACID GROUP of one amino acid nd the amino acid group: form a bond (peptide) Molecules: Dipeptide and H20 molecules.

8 of 12

Proteins structure

4 levels to the proteins structure:

PRIMARY STRUCTURE: sequence of amino acids held together by peptide bonds!

SECONDARY STRUCTURE: Folding of the primary structure, polypeptide chain coils to for a ALPHA HELIX or folds to form a BETA PLEATED SHEET. Both have H2 bonds!

TERTIARY STRUCTURE: Further folding of the polypeptide chain. H bonds between polar groups, Disulphide bonds:covalent bond formed between the sulphurs and R groups, of the mino aid cysteine. Ionic bonds: Between positve and negative charged R groups, of the amino acids. Hydrophobic interactions: Between the non-polar R groups, which cluster together towards teh centre of the molecule.

QUATERNARY STRUCTURE: Proteins made up from more than one polypeptide chain. (Haemogolbin) which consists of 4 polypeptide chains, 2 ALPHA chinas, and 2 BETA chains. Each chain has a heam group which contains a FE+ ion. Heam group gives blood its colour.

9 of 12


Haemoglobin function si to carry O2 from the lungs to the respiring tissues.

Haemoglobin (H6)+ Oxygen(4O2) ------->OXYHAEMOGLOBIN(H6O8)

Globular and Fibroous proteins:Fibrous: Form long fibres, they have regular repetiitve sequences of amino acids and are INSOLUBE in water. They often have STRUCTURAL ROLES. in living organisms eg: Myosin in muscles, Keratin in the hair and nails, Collagen in the skin!

Collagen: (Found in the skin, bones and ligaments)

*3 Identical left handed helix polypeptide chians, wound around each other: forms a triple helix. Held together by h2 bonds

*In the polypeptide every third aimino acid is glycine, whihc is small and allows 3 polypetides to pack closely together.

*Collagen molecules cross-link through covalent binds(forms fibres)=strenght!

10 of 12

Gobular protiens:

Gobular protiens:

Fold up into a compact ball shape, HYDROPHOBIC R GROUPS on the maino acids (turned inwards towards the centre and so HYDROPHILIC R GROUPS are on the outside. Therefore MORE water soluble than fibrous protiens. Gobular protiens have a METABOLIC ROLE in living organisms. Enzymes, plasma proteins and antibodies have gobular structures! These have a wide range of amino acids.

LIPIDS:ARE NOT POLYMERS!!! Lipids contain: C,H,O. The O is very small coompared with carbohydrates. therefore INSLOUBLE in water.

When condensation reactions occurs they form ester bonds which release water when they form between the glycerol and fatty acids ( this is what a fat is broken down to in digestion this forms 3 molecules of water as three bonds are made per triglyceride. 

Cholestrol and steriod hormones: Are found in all biological membranes, sit between the phospolipids hydrocarbon tails, which regulate the fluidity of the membrane, and strength. Cholestrol is a4 carbon basedsring structure.

11 of 12

Lipids continued

Functions: Source of energy- can be respiresed to release energy (ATP), Energy storage- lipids stored in a dipose cells in the fat cells. Biological memebranes- made form lipids, Insulation-blubber in whales is lipids reduces heat loss, protection- surface cuticle, Hormones- steriod hormones are lipids.

Structure: a fatty cahin, is a (-COOH) group, which is Caboxylicacid. And a long hydrocarbon chain, with 12-20 carbons on it. Unsaturated fatty acids: Have a c=c bond (double bonds between carbons). If a fattyacid have more than one double bond then it is a polyunsaturated.  Fats containing more unsaturated bonds, tends to be in plants (more fluid)  Saturated fattyacuids: have no C=C bonds, meaning all the carbons are fully bonded hydrogen. Animal fats are saturated, and are solid at room temperature. (lard:)

Triglycerides: energy source- This has one glycerol, and 3 fatty acids molecules. These are joined by condensation reactions, between the hyroxyl group on the glycerol molecules. A colvalent bond is a ESTERBOND! Andwater is formed. 3 condensation reactions occur so each hydroxyl groyup on the gycerol molecule joins with the carboxyl group on fattyacid.

Phospholipids: arefound in the cell membranes. Similar structure to tris, however only have 1 gylycerol, and 2 FATTY ACIDS. the third fatty acid is replaced by a phosphate group.

12 of 12




thank you so much for this! really helped :)

Bethany Cunningham


Good resource!

Similar Biology resources:

See all Biology resources »See all Biological molecules, organic chemistry and biochemistry resources »