Section 1 - Biological Molecules
2 Nucleic acids
1 Biological molecules
Carbohydrates
Lipids
Proteins
Nucleic acids
ATP
Water and inorganic ions
Monomers and Polymers
Polymers
Reactions
Monomers
Examples of monomers = monosaccharides, amino acids, and nucleotides
Polymers = long chains of monomers
Examples of polymers = starch, proteins, DNA
A condensation reaction adds two molecules together (e.g. two amino acids) and a water (H2O) molecule is formed.
A hydrolysis reaction breaks down polymers. A water molecule (H2O) is added and the chemical bond is broken, resulting in two monomers
Examples of hydrolysis - starch broken down into maltose/glucose, proteins broken down into amino acids
Tests
Monosaccharides
Disaccharides
Polysaccharides
Disaccharides are two monosaccharides joined by a glycosidic bond
Condensation reactions
Glucose + glucose = maltose
Glucose + fructose = sucrose
Glucose + galactose = lactose
Monosaccharides are carbohydrate monomers
Common monosaccharides = glucose, fructose, galactose
a-glucose and B-glucose isomers
Starch
Insoluble
Glycogen
Starch
Reducing sugars e.g. monosaccharides
Non-reducing sugars e.g. sucrose
Hydrochloric acid and sodium hydrogencarbonate solution, then Benedict’s test
Need to hydrolyse non-reducing sugar (acid) then neutralise pH
Benedict’s test
Orange-brown = positive
Iodine solution
Blue/black = positive
Cellulose
Glycogen and starch - polysaccharides of a-glucose.
Cellulose - polysaccharide of B-glucose
Straight chains
Plant cell wall
Cross-links
Good storage molecule
Branched
Animals and bacteria
Energy
Plants
Branched = amylopectin
Unbranched = amylose
Polymers (large chains
Tests
Monomers
Phospholipids
Triglycerides
Emulsion test - add ethanol and water, shake
Cloudy-white colour = positive result
Insoluble in water, soluble in organic solvents (e.g. alcohol)
Fatty acids and glycerol are the monomers of lipids
Fatty acids have the formula RCOOH
Fatty acids can be unsaturated (contain a C=C bond) or saturated (all C-Cbonds)
Hydrolysis
Polymerisation
Basis of test - lipids emulsify in the water and form tiny droplets
Component of cell membrane - phospholipid bilayer
Hydrophilic ‘head’, hydrophobic ‘tail’
Made from 1 glycerol molecule, 2 fatty acid chains, and 1 phosphate molecule
Condensation reaction
Ester bonds
Polar
‘Heads’ face towards aqueous environments e.g. cytoplasm
Insoluble in water
Good source of energy
Made from 1 glycerol molecule and 3 fatty acid chains
Condensation reaction
Ester bond
Lots of energy in a small volume
Many C-H bonds = lots of energy
No effect on osmosis in cells
Enzymes
Biological catalysts
Low activation energy of the reaction
Factors affecting enzyme reactions
Temperature
Enzyme-substrate complexes
Induced-ft model
Active site
Structure determines function
Substrate shape is complementary to active site
Specific structure of active site
Enzyme concentration
Substrate concentration
pH
Competitive and non-competitive inhibitors
Structure and folding
Monomers
Test
Biuret reagent
Purple = positive result
Blue = negative result
Amino acid
NH2 group
COOH group
R side chain
H bond
20 amino acids occur in living organisms, differ only in the R side chain
Dipeptide = 2 amino acids
Polypeptide = many amino acids
Peptide bonds
Condensation reaction
Protein can contain multiple polypeptides
Structure determines function
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
Polypeptide chain
Contains peptide bonds
Sequence of amino acids in primary tructure determines where bonds form, and hence 3D structure of protein.
a-helix or B-pleated sheet
Hydrogen bonds between NH and CO groups
Primary structure folds into secondary structure
Specific 3D shape or protein
Contains ionic bonds, disulfide bridges, and hydrogen bonds
Multiple polypeptide chains linked together
Monomers
Nucleotides are the monomers of polynucleotides (nucleic acids) like DNA and RNA
Nucleotides are joined by condensation reactions
Nucleotides contain a pentose sugar, a nitrogenous base, and a phosphate group
RNA
Ribonucleic acid
A short polynucleotide chain
Transfers genetic information from DNA (in nucleus) to ribosomes (cytoplasm)
Protein synthesis
Ribosomes are made up of RNA and proteins
Nucleotides in RNA contain ribose, a phosphate, and one of four bases - adenine, cytosine, guanine, or uracil
A pairs with U
C pairs with G
Phosphodiester bonds
DNA
Deoxyribonucleic acid
DNA carries genetic information
DNA is a double helix
Nucleotides in DNA contain deoxyribose, a phosphate, and one of four bases - adenine, cytosine, guanine, or thymine
Two polynucleotide chains, H-bonds between complementary bases
A pairs with T
C pairs with G
Very stable molecule
DNA replication
Semi-conservative
Double helix is separated, H-bonds are broken
DNA helicase
Each strand acts as a template, free nucleotides pair with complementary bases
Nucleotides joined together to form new strand
DNA polymerase
Phosphodiester bonds
Formation
Condensation reaction
During respiration and photosynthesis
ADP (adenosine diphosphate) and inorganic phosphate group (Pi)
ATP synthase enzymes
Structure
Adenosine trisphosphate
Ribose sugar, adenine molecule and three phosphate groups
Derivative of a nucleotide
Roles
Active transport
Movement
Metabolic processes
Hydrolysis
Releases energy
Hydrolysis into ADP and Pi
ATP hydrolase enzyme
Pi can phosphorylate other molecules
Water
Inorganic ions
Found in solutions e.g. cytoplasm and body fluids
Sodium ions
Co-transport
Phosphate ions
ATP and DNA
Iron ions
Hydrogen ions
pH
Hemoglobin
Aqueous environments
Metabolic reactions
Condensation and hydrolysis
A solvent
Evaporation
Has a cooling effect when evaporating off the skin
Temperature buffer
High heat capacity
Cohesion and surface tension
Cohesive forces allows water to be transported in a tube
Surface tension - water molecules stick together when in contact with air
Small units which combine to make large chains (polymers)