CHEMICALS OF LIFE
BY GEORGIA JARMOLKIEWICZ
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
carbohydrates
(contain starches and sugars, molecules contain 3 types of atom - carbon, hydrogen, oxygen)
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
function of carbohydrates
- needed for energy
- 1g of carbohydrate=17kj
- energy released by respiration
- glucose transported around animals and dissolved in plasma
- plants use carbs as starch-easy transformation between the two
- some plants store starch in seeds or tubers which we eat
- animals store carbs as polysaccharide glycogen instead of starch
- polysaccharide cellulose used to make fibres for plant walls
- cellulose fibres - very strong, help to maintain plant shape
- right: carb molecule structure
TESTING FOR CARBOHYDRATES
- Test for presence of sugars by adding Benedict's solution to a food and heating it
- If food contains reducing sugar (eg maltose, glucose), a red color will be produced
- mix will go blue, to green, to yellow, to orange and finally to red.
- It'll stay blue if there is no reducing sugar
- Starch test: add iodine. starch present will give a blue black color.
- no starch will give the original orange brown color
- below: results of a test with benedict's solution
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
testing for fats/oils
ethanol emulsion test
1) chop food and shake in ethanol
2)pour ethanol into water (it absorbs fat)
if fat was present, the ethanol splits into tiny blobs in the water; because of its oil content, it wont mix.
This is called emulsion and is a milky white color.
If no fat is present, the ethanol and water are clear.
proteins
(contain starches and sugars, molecules contain 5 types of atom - carbon, hydrogen, oxygen, nitrogen and sulfur)
PROTEINS CONTINUED
- protein molecules made of long chains of smaller molecules joined end to end - called amino acids
- 20 types of amino acid and these can be joined in any order to make a protein molecule
- any difference makes an entirely different protein
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.
deoxyribonucleic acid (dna)
- makes up genes+chromosomes
- made up of acids forming bond cross links
- made of T,A,C,G bases
- T and A bond
- C and G bond
- bases always pick up this way
- this bonding is replicated in every cell
- determined things such as hair color, eye color, blood type
< structure of DNA
bibliography
Pallister, John. Environmental Management A Core Text for O Level and Igcse. N.p.: Oxford Univ Pr, 2014. Print.