Chemistry of Life Flashcards Flashcards

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Water

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A polar inorganic molecule $H_2O$ that serves as the universal solvent in living organisms. It acts as a medium for most cellular chemical reactions, a reagent in hydrolysis reactions, and a transport and temperature-regulation fluid.

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Solvent

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A substance that dissolves other materials; in biology this role is primarily filled by water. Gases like $O_2$ and $CO_2$, mineral salts, and metabolic wastes dissolve in water to move into and out of cells.

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Hydrolysis

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A chemical reaction in which water ($H_2O$) is used to break polymers into monomers. It is essential in digestion and other catabolic processes to convert large molecules into usable units.

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Turgor Pressure

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The pressure of water inside a plant cell's vacuole that pushes the plasma membrane against the cell wall. This hydrostatic pressure maintains plant rigidity and helps support non-woody tissues.

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Micro-elements

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Inorganic elements required in trace amounts for normal biological function. Examples include iron and iodine, which are essential for haemoglobin formation and thyroid hormone respectively.

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Iron

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A micro-element component of haemoglobin ($Hb$) that enables oxygen transport in blood and is needed in plants for chlorophyll formation. Deficiency in humans causes anaemia and in plants causes chlorosis (leaf yellowing).

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Iodine

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A trace element required for the synthesis of the thyroid hormone thyroxine. Iodine deficiency can lead to goitre, an enlargement of the thyroid gland.

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Phosphorus

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A macro-element found in nucleotides, ATP ($ATP$), phospholipids of membranes, and bones and teeth in humans. It is usually absorbed by plants as phosphate $PO_4$, and deficiency can stunt plant growth.

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Calcium

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A macro-element important for healthy root growth in plants and for bones, muscle function, blood clotting, and nerve transmission in animals. Deficiency can lead to stunted growth in plants and bone disorders like rickets in humans.

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Sodium

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An inorganic macro-element involved in enzyme activity and water balance in plants and vital for nerve and muscle function in animals. Low sodium can cause muscle cramps and impaired nerve signalling.

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Potassium

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A macro-element that activates enzymes in plants and supports muscle and nerve function in animals. Plant deficiency often shows as yellow or brown leaf edges, while in animals it impairs nerve and muscle activity.

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Carbohydrates

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Organic macromolecules composed of carbon, hydrogen, and oxygen with general formula $CH_2O$; many are polymers of sugar monomers. They function primarily as energy sources, storage molecules (starch, glycogen), and structural components (cellulose).

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Monosaccharide

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The simplest carbohydrate monomer such as glucose with formula $C_6H_{12}O_6$. Monosaccharides are sweet, water-soluble, and serve as immediate energy sources for cells.

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Disaccharide

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A carbohydrate formed by two monosaccharides joined by a glycosidic bond in a condensation reaction that releases $H_2O$. Common examples include sucrose, lactose, and maltose, which are broken down by digestion into monosaccharides.

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Polysaccharide

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A large carbohydrate polymer made of many glucose units; examples include starch, cellulose, and glycogen. Polysaccharides are generally not sweet and are less soluble than simple sugars, serving storage or structural roles.

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Starch

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A plant polysaccharide that serves as the primary storage form of glucose in plants. When energy is needed, starch is hydrolysed into glucose molecules for respiration and metabolism.

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Lipids

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A diverse group of hydrophobic organic molecules (fats and oils) composed mainly of carbon, hydrogen, and oxygen with an H:O ratio generally greater than 2:1. They function in long-term energy storage, insulation, shock absorption, membrane structure, waterproofing, and absorption of fat-soluble vitamins.

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Saturated vs Unsaturated

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Saturated lipids (fats) are typically solid at room temperature and mainly from animal sources, while unsaturated lipids (oils) are liquid and usually plant-derived. Excessive intake of saturated fats can raise blood cholesterol and increase cardiovascular disease risk.

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Proteins

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Polymers of amino acids that contain carbon, hydrogen, oxygen, and nitrogen and are linked by peptide bonds. Proteins have structural, transport, enzymatic, hormonal, immune, and buffering roles in organisms.

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Enzymes

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Biological catalysts that are usually spherical proteins which lower activation energy and speed up specific biochemical reactions. They are reusable and highly efficient but sensitive to temperature and pH, with human enzymes having optimum temperatures around 35°C–40°C.

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DNA

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Deoxyribonucleic acid ($DNA$) is a nucleic acid made of carbon, hydrogen, oxygen, nitrogen and phosphorus that stores hereditary information in the nucleus. It controls protein synthesis and determines the amino acid sequence of proteins.