Unit 7: Human Digestive System - Biological Molecules

Comprehensive vocabulary flashcards covering biological molecules, food tests, metabolism, and enzyme kinetics based on Year 2 Science lecture notes.

Biological molecules

Molecules present in organisms that are essential to biological processes such as cell division and development, including carbohydrates, lipids, proteins, and nucleic acids.

Nutrients

Chemical substances in food that provide energy and materials needed by the body, classified into organic and inorganic molecules.

Carbohydrates

Organic molecules made up of carbon, hydrogen, and oxygen with the general formula $C_{n}H_{2m}O_{m}$ and a 2:1 ratio of hydrogen atoms to oxygen atoms.

Single sugars (Monosaccharides)

Small molecules such as glucose, fructose, and galactose with the chemical formula $C_{6}H_{12}O_{6}$ that cannot be further digested.

Double sugars (Disaccharides)

Sugars with the chemical formula $C_{12}H_{22}O_{11}$ produced when two single sugars join by condensation, including maltose, lactose, and sucrose.

Condensation

A chemical reaction in which two molecules join to form a larger molecule with the loss of a water molecule.

Hydrolysis

A chemical reaction where a double sugar or complex molecule is split into simpler molecules with the addition of a water molecule.

Benedict's Test

A test for reducing sugars where a food filtrate is heated with Benedict's reagent; results range from green (trace) to brick-red precipitate (large amount).

Glycogen

A branched, compact macromolecule serving as the storage form of carbohydrates in animals, stored in the liver and muscles.

Starch

The storage form of carbohydrates in plants, found in storage organs like potato tubers, made of glucose molecules in long helical chains.

Cellulose

An unbranched macromolecule of glucose arranged in long straight chains that provides mechanical strength and support to plant cell walls.

Iodine Test

A procedure using iodine solution to detect starch; a change from orange-brown to blue-black indicates starch is present.

Fats

Hydrophobic organic molecules made of one glycerol and three fatty acids used as energy stores, insulation, and to protect vital organs.

Saturated Fats

Fats with straight fatty acid chains that are typically solid at room temperature, such as butter.

Unsaturated Fats

Fats with fatty acid chains that have a kink or bend, typically liquid at room temperature, such as olive oil.

Ethanol Emulsion Test

A test used to detect fats where a cloudy white emulsion forms if fats are present after shaking the sample with ethanol and water.

Proteins

Organic molecules made of amino acids containing carbon, hydrogen, oxygen, and nitrogen (sometimes sulfur).

Peptide bond

A bond formed by a condensation reaction between the acid group of one amino acid and the amine group of another.

Primary Level of Protein Organisation

The specific sequence of amino acids in a polypeptide chain.

Biuret Test

A test for proteins that detects peptide bonds; adding sodium hydroxide and copper(II) sulfate results in a violet color if proteins are present.

Metabolism

The sum of all chemical reactions in a living organism, consisting of anabolic and catabolic reactions.

Anabolic reactions

Chemical reactions that build complex substances from simpler ones with the absorption of energy, such as protein synthesis.

Catabolic reactions

Chemical reactions that break down complex substances into simpler ones with the release of energy, such as cellular respiration.

Activation Energy ($E_{a}$)

The minimum amount of energy required for a chemical reaction to occur.

Catalyst

A substance that speeds up a chemical reaction by providing a pathway of lower activation energy while remaining chemically unchanged.

Enzymes

Biological catalysts, usually proteins, that speed up chemical reactions by lowering activation energy without being consumed.

Active Site

A pocket or depression on an enzyme's surface with a specific 3-D shape complementary to its substrate.

Lock-and-key hypothesis

A model describing enzyme action where a substrate (key) fits into the enzyme's active site (lock) to form an enzyme-substrate complex.

Denaturation

The loss or change in the 3-D shape of an enzyme or its active site due to heat or extreme pH, rendering it non-functional.

Optimum Temperature

The temperature at which an enzyme-catalysed reaction reaches its highest rate due to the maximum frequency of effective collisions.

Optimum pH

The pH level at which an enzyme's active site is most ideal for substrate binding, resulting in the maximum rate of reaction.