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Section 1A: Biological molecules (1.5 - Lipids (Structural features…
Section 1A: Biological molecules
1.1 - Biological molecules
Monomers: Glucose alpha glucose beta galactose fructose
Glucose+glucose=maltose
Glucose+galactose=lactose
Glucose+fructose=sucrose
When monosaccharides bond to form disaccharides they form a glycosidic bond. The type of glycosidic bond will depend on the carbons bonded for example maltose forms a 1,4 glycosidic bond.
1.2 - Carbohydrates and monosaccharides
Glucose
Glucose alpha and glucose beta. In carbon 1 H and OH swap. H is on top in glucose beta.
Can be stored in starch
Small molecule and so easily diffuses across membranes
C6H12O6
1.3 - Carbohydrates, disaccharides and polysaccharides
Formed through a condensation reaction which produces a H2O molecule. To break this a hydrolysis reaction has to occur which requires a H2O molecule to occur.
Test for reducing sugars/disaccharides: benedict's test - add benedict's reagent to solution place in warm bath and wait for colour change - should change from blue to orange yellow or red precipitate depending on how strong the solution is.
Test for non-reducing sugars: Add hydrochloric acid, place in warm bath, then neutralize and conduct benedict's test - if blue could be starch or water if not it is a reducing sugar - colour change of blue to red is what your looking for. - add acid first to break it down into its disaccharides or reducing sugars and then test they are there to see if it was originally a non-reducing sugar.
Polysaccharides
Starch:
Energy store in plants found in plastids
Produced from glucose during photosynthesis and is broken down during respiration to provide energy
Made up of highly branched alpha glucose molecules. Forming 1,4 and 1,6 glycosidic bonds.
Amylose:
Formed of unbranched alpha glucose molecules which compact to form a helical structure. Form 1,4 glycosidic bonds.
Found in plants
Amylopectin:
Highly branched
Found in plants
Formed of alpha glucose molecules. Forms 1,4 and 1,6 glycosidic bonds
Cellulose:
Formed of beta glucose molecules. Form 1,4 glycosidic bonds
Unbranched structure, where every other molecule is rotated 180 degrees
Part of cell walls - prevents cell walls from bursting during water intake - alongside structural support for cells .
Long chains of cellulose layer to form a network.
Hydrogen bonds between chains provide great tensile strength.
Glycogen:
Highly branched structure
Made up of alpha glucose molecules. Forms 1,6 and 1,4 glycosidic bonds.
Less dense and soluble than starch - is broken down faster also due to metabolic rate in animals being higher in animals than in plants.
1.4 - Starch, Glycogen and cellulose
1.5 - Lipids
Features:
Contributes to flexibility of membrane
Waterproofs cells
Insulates cells
Source of energy
Structural features (triglyceride):
High ratio of energy storing carbon hydrogen bonds to carbon atoms. This makes it a good energy source,
Good for storing energy due to low mass to energy ratio.
Waterproof due to being non-polar molecules. This means their storage will not affect the water or osmotic potential of the cell.
Produces water atom when oxidised due to high hydrogen to oxygen ratio.
Forms three ester bonds.
Structural formation (Lipid):
Formed of three glycerides (C3H8O3)
Each Glycerol contains 3 OH groups when forming a lipid these are removed during the condensation reaction alongside one H from each fatty acid to form 3H2O molecules.
A lipid is formed of one glycerol atom and three fatty acids.
Test for lipids - Emulsion test:
Method: Add ethanol until solution has dissolved then add pure water if a white emulsion appears lipids are present.
Safety: Ethanol is extremely irritant and highly flammable. There is also the danger of smashing glass.
How this works: Lipids do not dissolve in water due to their polar properties. So they are dissolved in ethanol first when water is added the lipids will rise above the water forming a white emulsion.
Fatty acid features and structure:
Fatty acids have a general formula of CH3(CH2)nCOOH. It holds an R group of hydrocarbon chains, and comes in unsaturated forms.
Fatty acids are unsaturated and so bend due to the large amounts of bonds, making it harder to break them down so they stay solid at room temperature.
Phospholipids.
Structure
Phosphate head - hydrophilic - polar
Fatty acid tail - hydrophobic - non polar
Features
1.6 - Proteins
Features:
Large molecules
Involved in nearly every biological process
Varying shape determines specific function.
Structure of a protein:
Primary structure: This is the sequence of amino acids bonded together through peptide bonds to form a poly peptide chain. This is determined by the DNA sequence.
Secondary structure: This is the bonds within the protein. This is important as it determines the tertiary structure.
Tertiary structure: This is based off the types of bonds that has occured (primary structure) which will determine whether the polypeptide chain forms a alpha pleated or beta helix structure.
Quaternary structure: This is the amount of polypeptide chains within a protein that may also be attached to a prosthetic group.
Test:
Make solution an alkali
Then add dilute copper sulfate solution
If proteins are present colour will go from blue to purple
Structure of an amino acid
Consists of: an amino group (NH2), R group, a carboxyl group (COOH) and a H atom.
The R group is a variable which makes each amino acid different
Bonds through a condensation reaction where the carboxyl and amino group form a dipeptide bond.
Bonds that occur within polypeptide chains are: ionic, disulphide, and hydrogen.
Features of amino acids:
Form dipetide bonds
Form polypeptide chains
20 naturally occurring
1.7 - Enzyme action
Induced fit model: This is where the enzymes shape changes when met by the substrate at the active site. Demonstrating how the lock and key model is wrong as it states the enzymes shapes is specific to the substrate.
Lock and key model: This suggests that the enzyme is specific to the shape of its substrate.
Key words
Enzyme-substrate complex
Active site
Enzyme substrate particle collision
Activation energy
1.8 - Factors affecting enzyme action
Temperature
pH
Substrate concentration: The higher the substrate concentration the higher
1.9 - Enzyme inhibition
2.1 - Structure of RNA and DNA
2.2 - DNA replication
2.3 - Energy and ATP
2.4 - Water and it's functions