AQA A Level Biology Topic 1: Biological Molecules

Vocabulary flashcards covering the key monomers, polymers, biological molecules (carbohydrates, lipids, proteins, nucleic acids), enzymes, ATP, water, and inorganic ions based on the AQA A Level Biology Topic 1 notes.

Monomers

Smaller, repeating molecules / units from which larger molecules / polymers are made

Polymers

Molecules made from many (a large number of) identical / similar monomer molecules

Condensation reaction

A reaction where 2 molecules join together, forming a chemical bond and releasing a water molecule

Hydrolysis reaction

A reaction where 2 molecules are separated by breaking a chemical bond using a water molecule

Monosaccharides

Monomers from which larger carbohydrates are made, such as glucose, fructose, and galactose

Isomers

Molecules with the same molecular formula but differently arranged atoms, such as $\alpha$-glucose and $\beta$-glucose

$\alpha$-glucose structure

An isomer of glucose where the OH group is located below carbon 1

$\beta$-glucose structure

An isomer of glucose where the OH group is located above carbon 1

Disaccharide

Two monosaccharides joined together by a glycosidic bond formed via a condensation reaction

Maltose

A disaccharide formed by the condensation of glucose + glucose

Sucrose

A disaccharide formed by the condensation of glucose + fructose

Lactose

A disaccharide formed by the condensation of glucose + galactose

Polysaccharides

Many monosaccharides joined together with glycosidic bonds formed by many condensation reactions

Starch

The energy store in plant cells, consisting of a polysaccharide of $\alpha$-glucose made of amyose and amylopectin

Amylose

An unbranched form of starch with 1,4-glycosidic bonds that forms a helical, compact structure

Amylopectin

A branched form of starch with both 1,4- and 1,6-glycosidic bonds

Glycogen

The energy store in animal cells, a highly branched polysaccharide made of $\alpha$-glucose with 1,4- and 1,6-glycosidic bonds

Cellulose

A polysaccharide of $\beta$-glucose that forms long, straight, unbranched chains linked by hydrogen bonds to form microfibrils

Microfibrils

Strong fibres formed from parallel strands of cellulose cross-linked by many hydrogen bonds

Benedict’s test

A test for reducing sugars that involves adding Benedict's solution and heating in a boiling water bath; a positive result is a green, yellow, orange, or red precipitate

Iodine test

A biochemical test for starch using iodine dissolved in potassium iodide; a positive result is a blue-black color

Fatty acid ($RCOOH$)

A molecule consisting of a carboxyl group ($-COOH$) and a variable hydrocarbon R-group

Saturated fatty acid

A fatty acid with no $C=C$ double bonds in the hydrocarbon chain, meaning all carbons are fully saturated with hydrogen

Unsaturated fatty acid

A fatty acid with one or more $C=C$ double bonds in the hydrocarbon chain, creating a bend or kink

Triglycerides

Lipids formed by 1 glycerol molecule and 3 fatty acids joined by 3 ester bonds via condensation reactions

Phospholipids

Lipids where one fatty acid of a triglyceride is substituted by a phosphate-containing group

Hydrophilic

Water-attracted; for example, the phosphate heads of phospholipids that point toward the aqueous environment

Hydrophobic

Water-repelled; for example, the fatty acid tails of phospholipids that point away from water

Emulsion test

A test for lipids involving adding ethanol, shaking to dissolve, and then adding water; a positive result is a milky white emulsion

Amino acid

The monomer of proteins, containing a carboxyl group ($-COOH$), an amine group ($H_2N$), and a variable side chain ($R$)

Peptide bond

A chemical bond formed between the carboxyl group of one amino acid and the amine group of another through a condensation reaction

Primary structure

The specific sequence of amino acids in a polypeptide chain

Secondary structure

The folding of a polypeptide chain into repeating patterns like alpha helices or beta pleated sheets due to hydrogen bonding

Tertiary structure

The overall 3D folding of a polypeptide chain due to interactions between R groups, including hydrogen bonds, ionic bonds, and disulfide bridges

Quaternary structure

The structure formed by the interaction of more than one polypeptide chain

Biuret reagent

A solution of sodium hydroxide and copper (II) sulphate used to test for proteins; a positive result is a purple or lilac color

Induced-fit model

Model of enzyme action where the binding of a substrate causes the active site to change shape slightly to become complementary

Competitive inhibitors

Molecules with a similar shape to the substrate that compete for and block the enzyme's active site

Non-competitive inhibitors

Inhibitors that bind to an allosteric site (other than the active site), changing the enzyme's tertiary structure and active site shape

DNA (Deoxyribonucleic acid)

A molecule that holds genetic information and is a polymer of nucleotides formed from deoxyribose, a phosphate group, and a nitrogen-containing base

RNA (Ribonucleic acid)

A molecule that transfers genetic information from DNA to ribosomes, consisting of ribose, a phosphate group, and nitrogen-containing bases (A, U, C, G)

Phosphodiester bond

A bond joining adjacent nucleotides in polynucleotides, formed between the phosphate group of one and the sugar of another

DNA helicase

An enzyme that breaks hydrogen bonds between complementary bases to unwind the DNA double helix during replication

DNA polymerase

An enzyme that joins adjacent nucleotides on a new DNA strand by forming phosphodiester bonds during semi-conservative replication

ATP (Adenosine triphosphate)

A nucleotide derivative composed of ribose, adenine, and 3 phosphate groups used as an immediate energy source

ATP hydrolase

An enzyme that catalyses the hydrolysis of ATP into ADP and an inorganic phosphate ($P_i$)

ATP synthase

An enzyme that catalyses the resynthesis of ATP from ADP and $P_i$ during condensation reactions

Specific heat capacity

The property of water that allows it to gain or lose a lot of heat without a large change in temperature, buffering temperature changes

Latent heat of vaporisation

The property of water requiring significant energy to evaporate, allowing for effective cooling via sweat

Cohesion

Strong attraction between water molecules due to hydrogen bonding, which supports columns of water in xylem

Iron ions ($Fe^{2+}$)

A component of the haem group in haemoglobin that allows oxygen to bind for transport

Sodium ions ($Na^+$)

Inorganic ions involved in the co-transport of glucose/amino acids, action potentials in neurons, and affecting water potential

Phosphate ions ($PO_4^{3-}$)

Inorganic ions that are components of nucleotides (forming phosphodiester bonds), ATP, and the hydrophilic part of phospholipids