Biology Paper 1 AQA

• To test a piece of food for the presence of a lipid, mix ethanol and water with the sample of lipid.
• Trna has an anti-codon at one end and an amino acid binding site at the other.
• If a lipid is present, a white, cloudy emulsion will appear.
• The hydroxyl group in the cellulose structure is inverted in comparison to the starch structure.
• Starch is made from alpha glucose and cellulose is made from beta glucose.
• Starch molecules are insoluble so it doesn’t affect water potential.
• Starch molecules are compact and so stored easily.
• Cellulose molecules form fibrils which form hydrogen bonds between the fibres, this is formed from macrofibres that are parallel to one another.
• This helps to keep cellulose molecules strong and rigid to withstand the water pressure inside the plant cells.
• Cellulose molecules are also made from beta glucose from condensation reactions, this allows them to keep straight and rigid which allows them to withstand the water pressure.
• There is a polymer of amino acids joined together by peptide bonds.
• The primary structure is the order of amino acids.
• The secondary structure is formed by the folding of a polypeptide chain due to hydrogen bonds.
• Tertiary structure is 3-D folding due to hydrogen/disulfide and ionic bonds.
• Quaternary structure is two or more polypeptide chains.
• Proteins are digested in the gut through hydrolysis of peptide bonds.
• Endopeptidases break polypeptides into smaller peptide chains.
• Exopeptidases remove terminal amino acids.
• Dipeptidases hydrolyse dipeptides into amino acids.
• Inhibitors reduce binding of the enzyme to the substrate.
• Competitive inhibition occurs when an inhibitor similar to the substrate binds to the active site of the enzyme, inhibiting the enzyme from binding to the substrate.
• Non-competitive inhibition occurs when an inhibitor binds to a site other than the active site, preventing the formation of the active site.
• ATP is a single-step reaction making it efficient and energy is released in small amounts.
• The chemical test for starch involves adding drops of iodine, if starch is present it will turn from brown to blue/black.
• The chemical test for reducing sugars involves adding benedicts reagent to the food sample and heating it in a water bath for 5 minutes, if the solution turns red (orange-brown) then a reducing sugar is present.
• A phospholipid is a molecule where one of the fatty acids of a triglyceride is substituted by a phosphate.
• Antibodies in an ELISA test bind to antigen, a second antibody with enzyme attached is added, the second antibody attaches to antigen, and then a substrate is added and colour changes.
• Pathogens can cause disease by releasing toxins and killing cells/tissues.
• The rough endoplasmic reticulum is involved in the production of enzymes because it has ribosomes to make proteins by protein synthesis.
• A monoclonal antibody prevents a regulator protein from working because it has a specific tertiary structure, forms a complex, and so the regulator protein is not complimentary.
• Phospholipids are arranged in a bilayer with hydrophobic tails that don’t like water molecules and hydrophilic heads that are attracted to water molecules.
• Phosphate heads are hydrophilic and phosphate tails are hydrophobic, forming micelles.
• Phagocytosis of a virus leads to presentation of its antigens when a phagosome fuses with a lysosome, the virus is destroyed by lysosomes, and the antigen from the virus is displayed on the cell of the membrane.
• A phagocyte destroys a pathogen present in the blood by engulfing, forming a vesicle, digesting enzymes, and then releasing the vesicle.
• Monoclonal antibodies are antibodies with the same tertiary structure.
• B lymphocytes of a frog would respond to a vaccination against Ranavirus by binding to viral complementary antigen, cloning, producing monoclonal antibodies, and producing memory cells.
• HIV is replicated by attachment proteins attaching to receptors on T cells, RNA entering the cell, reverse transcriptase converting RNA to DNA, viral protein produced, virus assembled and released from the cell, and HIV mRNA translated into new HIV.
• Lysosomes fuse with vesicles, release hydrolytic enzymes, and then fuse with the cell-surface membrane.
• Pre-mRNA is spliced to remove introns.
• Antibodies stimulate phagocytosis by binding to antigens and attracting phagocytes.