Biological Molecules
- Created by: hazelnut_xix
- Created on: 23-09-18 18:25
Polymers
4 main types of Biological Macromolecules:
- Polysaccharides (carbohydrate) - polymer
- Protein - polymer
- Nucleic Acids (DNA/RNA) - polymer
- Lipids (fats/oils) - not a polymer
Polymer = a long-chained molecule that consists of many smaller & similar subunits known as monomers
Condensation Reaction = a creation of a bond which makes a water molecule
Hydrolysis = a breaking down of a bond using a water molecule
- Monomers are usually joined together and broken down through hydrolysis and condensation reactions
-During condensation and hydrolysis, there is always 1 less water molecule than monomer in the reaction.
Carbohydrates
3 main types of carbohydrates:
- Monosaccharides ('mono' = 1)
- Disaccharides ('di' = 2)
- Polysaccharides ('poly' = many)
Monosaccharides are the simplest carbohydrate:
- they usually have the molecular formula CH20
- Can be shown using skeletal diagrams (carbon atom is where 2/more lines meet)
Isomer = Different molecules with the same molecular formula (i.e C6H1206 = glucose, fructose, galactose)
- α-glucose and β-glucose are both isomers of each other. The difference is the H and OH bonds on C-1 is switched
Disaccharides
Glycosidic Bond = then bond between 2 monosaccharides to form a disaccharide through a condensation reaction
Making disaccharides:
- α-glucose + α-glucose = Maltose + water
- α-glucose + galactose = Lactose + water
- α-glucose + fructose = sucrose + water
- When writing the molecular formula of these disaccharides, you must consider that water is lost - i.e Maltose = C12H22O11 due to the loss of water in the condensation reaction
Polysaccharides
Polysaccharide = a polymer of many monosaccharides which are linked together
Glucose can be bonded togther to make a polysaccharide. It allows energy to be transported to cells around the body. Its properties are:
- Water soluble = travels easily around the body in the blood
- Small = enters + exits cells easily
- Chemically reactive = broken down to provide energy when needed
- It can be made into a polymer if needed - stored as glycogen or starch
Starch = energy storage
Glycogen = energy storage
Cellulose = structure
Starch
Structure of Starch:
- Helical chains of α-glucose monomers - compact so more energy can be stored in the cell
- It is a large molecule - it cant leave the cell through the membrane
- Stored in the cloroplasts as insoluble starch granules - doesn't affect water potential
- Can be hydrolysed into α-glucose for respiration
Starch can come in 2 forms:
- Amylose = unbranced + helical
- Amylopectin = branched + helical
-Branches mean more ends for the enzymes to hydrolise the glucose from. The more branches, the faster the rate of hydrolysis is.
Glycogen
Structure of glycogen:
- Consists entirely of α-glucose monomers
- Helical & insoluble
- More branches but shorter chains = hydrolysed faster into α-glucose
The quicker rate of hydrolysis benefits animals as they move so they need more energy, compared to plants. The animals muscles and nervous system need more energy at a faster rate of respiration.
Cellulose
Structure of Cellulose:
- Polymers of β-glucose
- Long, straight and unbranched chains - lots line up in parallel to form microfibres
- Strong - lots of hydrogen bonding between the microfibres. Each hydrogen bond is weak on its own but m,any together give the polymers strength.
In β-glucose, the OH in C-1 is flipped; therefore for glycosidic bonds to form every 2nd OH moleclue has to flip upside-down. This creates an alternating up-down pattern.
Lipids
Important Lipids:
- Triglycerides (fats & oils)
- Phoshoplipids
- Chloesterol
-Lipids are a major part od macromolecules however they aren't a polymer. The are hydrophobic.
Hydrophobic = don't mix with water
Hydrophillic = mix well with water
Triglycerides
Functions of Triglycerides:
- Energy storage - densest energy storage molecule
- Insulation - reduce loss of body heat as they're poor conductors
- Protection - fat stored around delicate organs
Structure of Triglycerides:
- Made up of 3 fatty acids and 1 glycerol, with ester bonds between the fatty acid and glycerol
- Insoluble as they're hydrophobic - no affect on water potential/osmosis
- Fatty acid tails are energy rich - each C-C and C-H bonds contain energy
alcohol + carboxyl group -> ester group + water
-Animal fats = saturated and solid at room temperature. Saturated fatty acids are packed closely together as they dont have kinks, compared to unsaturated fatty acids.
-Plant/fish fats = usually unsaturated and liquid at room temperature
Phospholipids
Amino Acids
Each amino acids include:
- an amine group - NH2
- a carboxyl group - COOH
- one of 20 side chains - R-Group
- all attatched to a central Carbon atom along with a Hydrogen atom.
-Amino acids differ only by their R-Group and are all joined together through condensation reactions.
Peptide Bond = the bonds between 2 amino acids
Dipeptide = the molecule formed between 2 amino acids joining together
Polypeptide = when many amino acids are bonded together through peptide bonds
Proteins
Structure of Proteins:
- Polymers - made of many monomers called amino acids.
- 20 different amino acids which would be included in the polymer - creates a huge variety of combinations (20^n)
Levels of stucture in proteins:
- Primary - unique sequence of amino acids forming a polypeptide - held together through Hydrogen bonds. Different proteins have different primary structures
- Secondary - folding of the polypeptide chain into 2 structures (alpha helix & beta pleated sheet) - held together through hydrogen bonds
- Tertiary - folding of the polypeptide into its overall 3D shape - held together by hydrogen bonds, ionic bonds and disulfide bridges
- Quaternary - coming together of 2 more more polypeptide chains - if the protein isn't made up of more than 1, then this process doesn't occur
Disulfide Bridge = 2 sulfur containing R-groups bond together
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