AQA A-level Biology - Molecules Flashcards

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Flashcards covering key concepts from the AQA A-level Biology Year 1 textbook, focusing on molecules, carbohydrates, lipids, and proteins.

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24 Terms

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What is hydrolysis?

The process in which water molecules are added to break down a polymer into monomers.

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What is condensation?

A chemical reaction in which two monomers join together, and a molecule of water is formed.

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Name three monosaccharides important in our food.

Glucose, fructose, and galactose.

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Name three common disaccharides.

Sucrose, maltose, and lactose.

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Describe the structure of amylose.

A long chain of α-glucose molecules linked by 1,4-glycosidic bonds, coiled into a spiral, and held in place by hydrogen bonds.

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What is the difference between amylopectin and glycogen?

Both contain α-glucose chains with 1,4- and 1,6-glycosidic bonds, but glycogen has more frequent 1,6 bonds, making it more branched and compact.

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Describe the structure of cellulose.

Every other β-glucose molecule is ‘upside-down’, resulting in very straight and long chains, which line up parallel with each other and are linked by hydrogen bonds.

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What are fats and what type of fatty acids do they contain?

They are solid at about 20°C and primarily consist of saturated fatty acids, which have only single bonds between carbon atoms.

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Describe the structure of a triglyceride

Glycerol bonded to 3 fatty acids via ester bonds

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How do you perform the emulsion test for lipids?

Add ethanol, then pour the solution into water. A white emulsion indicates lipids.

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How does a phospholipid differ from a triglyceride?

It has a phosphate group instead of one of the fatty acids, giving it a hydrophilic head and hydrophobic tails.

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Describe a protein.

Consists of one or more polypeptide chains folded into a complex three-dimensional shape determined by the order of amino acids.

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Describe the general structure of an amino acid.

A central carbon atom (α-carbon) attached to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and a variable R-group.

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What is a peptide bond?

The bond between two amino acids, formed by a condensation reaction between the amino group of one and the carboxyl group of the other, with the release of a water molecule.

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What is the primary structure of a protein?

The sequence of amino acids in the polypeptide chain.

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What is secondary protein structure?

The way parts of the polypeptide chain fold in a regular way, forming structures such as α-helices or β-pleated sheets.

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What is the tertiary structure of a protein?

The complex folding of the entire polypeptide molecule, giving the protein its overall globular shape, maintained by various bonds between amino acids.

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What is quaternary protein structure?

Describes proteins made up of two or more polypeptide chains, which are held together by the same types of chemical bonds that maintain the tertiary structure.

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How do you perform a biuret test for protein?

Add sodium hydroxide solution, then a few drops of dilute copper sulfate solution. A mauve color indicates the presence of protein.

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How do you perform Benedict's test for reducing sugars?

Heat the test sample with Benedict’s reagent. An orange-red precipitate indicates reducing sugars.

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How do you perform an iodine test for starch?

Add iodine solution. A blue-black color indicates starch.

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