Water Carbohydrates And Lipids

Oxygen and hydrogen share electrons unequally; oxygen attracts electrons more strongly and becomes slightly negative (δ⁻); hydrogens become slightly positive (δ⁺), creating a permanent dipole

Ionic substances dissociate into positive and negative ions in water; δ⁻ oxygens are attracted to positive ions, while δ⁺ hydrogens are attracted to negative ions; water molecules surround the ions and pull them apart, dissolving them

Any two from: glucose; amino acids; mineral ions; hormones; urea; carbon dioxide

Monosaccharide is a single sugar unit (e.g. glucose); disaccharide is two sugar units joined by a glycosidic bond (e.g. maltose). Polysaccharide is many sugar units joined into a long chain or branched structure (e.g. starch / glycogen)

Glycogen is insoluble, so does not affect water potential of cells / no osmotic effect; compact, allowing much glucose to be stored in a small space. Highly branched, giving many ends for enzymes to act on. Allows rapid hydrolysis to release glucose for respiration when needed

Both are polymers of α-glucose / both contain α-1,4 and α-1,6 glycosidic bonds / both are branched. Glycogen is more branched than amylopectin. Glycogen is found in animals (liver, muscle) whereas amylopectin is found in plants

Prepare standard solutions of glucose at known concentrations; add equal volumes of Benedict’s reagent to each tube. Heat all tubes in an 80°C water bath for the same time. Record colours produced as a set of colour standards. Test the unknown under identical conditions and compare its colour to the standards

Orange-brown to blue-black

Visual comparison is subjective and varies between observers; a colorimeter gives a quantitative absorbance reading at a set wavelength; this allows a calibration curve to be used for an objective, reproducible estimate

The solution remains blue / no colour change; sucrose is a non-reducing sugar; it cannot reduce Cu²⁺ to Cu⁺ / does not donate electrons

Two glucose monomers come together. An –OH from each reacts and a molecule of water is released (condensation). A glycosidic bond (e.g. α-1,4) forms between the two glucose molecules

A reaction in which a covalent bond is broken; by the addition of a water molecule

The enzyme amylase catalyses hydrolysis of starch; water is added across glycosidic bonds, breaking them; producing maltose; maltase further hydrolyses maltose into glucose

One glycerol combines with three fatty acids; three condensation reactions occur (one per fatty acid); three water molecules are released; three ester bonds form between –COOH of fatty acid and –OH of glycerol

Saturated has only single C–C bonds, unsaturated has at least one C=C double bond; saturated chains are straight whereas unsaturated chains are kinked at the double bond

Triglycerides are highly reduced with many C–H bonds; this releases approximately twice the energy per gram of carbohydrate when respired. They are insoluble, so do not affect cell water potential. They store compactly in adipose tissue, providing insulation and cushioning. Polysaccharides such as glycogen, amylose, and amylopectin are also insoluble; this prevents osmotic effects on cells. Their compact, often coiled or branched structure packs much glucose into a small space. Branching in amylopectin and glycogen provides many ends for enzymes; allowing rapid hydrolysis to release glucose for respiration. Both are insoluble and compact, ideal for safe long-term storage; triglycerides offer denser energy storage, while polysaccharides allow faster glucose release on demand