Water

• most organisms are made of 80% water
• cytoplasm + space between cells is mainly composed of water too
• metabolic rxn can only take place if chemicals reacting are dissolved in water
• if cells dry out, they die
• plasma contains water
• water dissolves enzymes and nutrients in alimentary canal
• water helps us remove waste: urea dissolved in water

SUGARS

• simplest kinds of carbohydrates are simple sugars/monosaccharides
• glucose is a simple sugar
• monosaccharides: soluble, taste sweet
• two simple sugar molecules joined: complex sugar/disaccharide
• eg:sucrose, maltose
• many simple sugars joining = polysaccharide
• eg: cellulose, glycogen
• polysaccharide: insoluble, dont taste sweet

glucose molecule

fats/lipids

( molecules contain 3 types of atom - carbon, hydrogen, oxygen)

functions of fats

• carbs/fats/oils used to release energy
• 1g fat = 39kj 
• fats used after carbohydrates
• useful for storing energy, especially in mammals
• cells beneath skin filled with drops of fats or oils called adipose tissue
• helps keep heat within the body eg walruses
• many plants store energy in oils eg coconut, peanut, castor oil. 
• right: examples of fats/oils

functions of proteins

• some proteins soluble in water: eg haemoglobin. some aren't: eg keratin
• proteins used to make new cells. 
• cytoplasm+membranes contain a lot of protein
• also used to make antibodies to keep body protected from infection
• chains can curl in different shapes, and this is determined by the order of amino acids
• form fits function
• right: protein types

testing for protein

• Biuret test
• mix food in water, add dilute copper sulfate solution
• add dilute potassium hydroxide, slowly
• protein=purple
• no protein=remains blue
• Biuret test shown below.

bibliography

Pallister, John. Environmental Management A Core Text for O Level and Igcse. N.p.: Oxford Univ Pr, 2014. Print.