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Carbohydrates/Polysaccharides:
-Carbohydrates are polymers, made up of repeating units. The repeating unit to a carbohydrate is a simple sugar e.g glucose/fructose/galactose.
-This repeating unit, or monomer, is also known as a monosaccharide (one sugar). Monomers are joined by glycosidic bonds, formed through condensation reactions.
-Two sugars joined together is known as a disaccharide, because there are two monomers.
Amylose: Straight chains of glucose linked together by the aforementioned glycosidic bonds.
Glycogen: Highly branched form of starch found in muscle cells as granules. A store of glucose readily available by hydrolysis of the glycogen.
Amylopectin: Branched form of amylose (therefore enzymes can act faster- SA/vol ratio!) Starch is a combination of amylose and amylopectin.
Cellulose: Polysaccharide found in plants. A slightly different form of glucose is used in these monomers. It is known as beta-glucose.
Lipids, triglycerides and pH:
-Lipids are combinations of fatty acids and glycerol known as triglycerides.
-Lipids act as energy stores as fat, and can be used as respiratory substrates.
-When lipids are broken down, they release fatty acids. Expect these to lower the pH!
-Phospholipids make up membranes (bilayers/vesicles etc) and glycolipids help make up some forms of receptor and antigen.
Testing for lipids:
-Mix with ethanol in a test tube and shake well. A white emulsion/precipitate at the top of the liquid will indicate a positive test result
Proteins, Polymers and Polypeptides:
-Proteins structurally speaking are polymers (made up of many repeating units).
-The repeating unit to a protein (or the monomer of the polymer) is an amino acid, also known as a peptide.
-Therefore many amino acids joined end to end are known as a polypeptide (multiple peptide monomers).
Testing for proteins:
-The Biuret test is used for identifying proteins. It changes to a purple colour upon interaction with a polypeptide, showing a positive result.
-Biuret reagent is made with NaOH (sodium hydroxide) and CuSO4 (copper sulphate).
-If protein is not present, the cupric ions will cause the solution to remain blue, showing a negative result.
Nucleic acids: DNA/RNA:
DNA: A double-stranded, double-helix written in antiparallel manner. It is a polymer made up of nucleotides which themselves contain a sugar, a phosphate group and one of four nitrogenous bases (A:T/C:G). It can be replicated or unwound for protein synthesis. It carries a base genetic code that codes for different proteins using sequences of DNA known as genes.
RNA: A single-stranded copy of DNA. It is used in transporting the code from DNA in the nucleus to the ribosome, where the code is read in order to synthesise a protein. RNA variants involve tRNA (a clover-leaf shaped RNA molecule used in translation (protein synthesis) and mRNA (the messenger RNA molecule made as a copy from DNA during transcription in the nucleus). rRNA is a special type of RNA that combines with small proteins to form ribosomes.
Enzyme
Carbohydrase
Amylase
Lipase
Protease
Substrate
Carbohydrate
Starch
Fats/Lipids
Protein
Product
Simple sugars and glucose
Simple sugars and glucose
Fatty acids and glycerol
Amino acids
Lipids further:
-An example of a simple lipid is a triglyceride. These are composed of three fatty acids bound to a glycerol scaffold.
-Triglycerides are great stores of energy, with a high ratio of C-H bonds. Since these also have a low mass compared to their energy store, they act as very suitable, compact storage molecules for energy.
-Lipids can be saturated or unsaturated. This term outlines whether the fatty acid tails contain double bonds or not.
Saturated lipids: Found in the fat of animal tissue, do not contain double bonds.
Unsaturated: Found in plants, these fatty acids contain double bonds in their tales.
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