3.2 Carbohydrates, lipids and proteins

Distinguish between organic and inorganic compounds
Organic compounds are compounds that contain carbon found in living organisms.

There are exceptions, which include carbon dioxide, hydrogen carbonates (product of carbon dioxide and water) and calcium carbonate.

Amino acids structure (bubblews.com)

Glucose structure (openstudy.com)

Ribose structure (Rosalind.info)

Fatty Acids structure (courses.washington.edu)

Three examples each of monosaccharides, disaccharides and polysaccharides
Monosaccharides: glucose, galactose, fructose.

Disaccharides: maltose, lactose, sucrose.

Polysaccharides: starch, glycogen, cellulose.

One function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants

Glucose: carried by blood to transport energy to cells throughout the body.

Lactose: sugar in milk, provides energy to young animals until they are weaned.

Glycogen: short term energy storage in liver and in muscles.

Fructose: used to make fruits sweet tasting, attracting animals to disperse seed in fruit.

Sucrose: carried by phloem to transport energy to cells throughout plant.

Cellulose: used to make strong fibres that are used to construct the plant cell wall.

Role of condensation and hydrolysis in relationships

Condensation reactions - molecules joined and water is byproduct.

Hydrolysis reactions - requires water to break covalent bond between 2 subunits.

Polypeptides + water = dipeptide or amino acids.

Polysaccharides + water = disaccharides or monosaccharides.

Glycerides (or triglycerides) + water = fatty acids + glycerol.

Three functions of lipids
Lipid functions: energy storage, thermal insulation, buoyancy.

Compare the use of carbohydrates and lipids in energy storage

Lipids: more energy per gram than carbohydrates - stores of lipids are lighter than those of carbohydrates.

Lipids: insoluble in water, do not cause problems with osmosis in cells.

Carbohydrates: more easily digested than lipids so energy stored in them can be released easily.

Carbohydrates: soluble in water so are easier to transport to and from store.