B1.2 ProteinsIB Biology HL: Flashcards

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Word equation for making a dipeptide?

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Word equation for making a dipeptide?: Amino acid + amino acid → dipeptide + water.
What is an essential amino acid?: One that cannot be synthesized and must be obtained from food.
Number of possible sequences for a chain of n amino acids?: 20ⁿ.
What is denaturation?: A change in a protein's three-dimensional shape, caused by heat or pH, that causes loss of function.
HL: How are hydrophilic R-groups classified?: Polar or charged; charged ones are acidic (–COO⁻) or basic (–NH₃⁺).
HL: What determines the conformation of a protein?: Its primary structure: the sequence and position of each amino acid.
HL: What stabilizes alpha helices and beta-pleated sheets?: Hydrogen bonds in regular positions between C=O and N–H groups of the backbone.
HL: Name four types of bond or interaction in tertiary structure.: Hydrogen bonds, ionic bonds, disulfide bonds, hydrophobic interactions.
HL: Which amino acids form disulfide bonds?: Pairs of cysteines.
HL: How can R-groups take part in ionic bonds?: Amine and carboxyl groups gain or lose H⁺ to become charged (–NH₃⁺, –COO⁻).
HL: Where are hydrophobic amino acids in a soluble globular protein?: Clustered in the core, away from water.
HL: Why do integral proteins stay in membranes?: They have regions of hydrophobic amino acids that embed in the hydrophobic core.
HL: Conjugated vs non-conjugated protein, with examples?: Conjugated has a non-polypeptide part (haemoglobin, haem); non-conjugated does not (insulin, collagen).
HL: How does collagen's form suit its function?: Three chains in a triple helix form strong, insoluble fibres with high tensile strength.
HL: How has cryo-EM helped protein biology?: It images single protein molecules and their interactions, impossible with the unaided senses.