bio molecules

Question 1

property of water 1

Answer 1

-property of water - water is an excellent solvent able to dissolve many kinds of substances (polar and ionic compounds)
-plants - mineral salts and manufactured food (eg. sucrose and amino acids) dissolve in water to be transported in the xylem and phloem respectively
-humans - blood plasma consists of 90% water which serves to transport dissolved substances in the circulatory system

Question 2

property of water 2

Answer 2

-property of water - cohesion between water molecules, adhesion between water molecules and other molecules
-plants - transpiration pull is the force that transports water and dissolved mineral salts in the xylem

Question 3

property of water 3

Answer 3

-property of water - high latent heat of vaporisation
-plants - evaporative cooling in plants due to transpiration prevents plants from overheating
-humans - sweat secreted on skin surface, water evaporates and removes heat from body

Question 4

property of water 4

Answer 4

-property of water - reactant for various chemical reactions
-plants - raw material for photosynthesis
-humans - hydrolysis of food molecules in digestion

Question 5

property of water 5

Answer 5

-property of water - forms the large part of the mass of most organisms
-plants - cytoplasm, cell sap of plant cells contains large amounts of water
-humans - cytoplasm, blood, digestive juices, tissue fluid, fluid in joints and contained within organs

Question 6

property of water 6

Answer 6

-property of water - incompressible
-plants - provides physical support in turgor pressure
-humans - allows blood to be pumped efficiently around the body; amniotic fluid is a shock absorber which protects the foetus

Question 7

reducing sugars

Answer 7

-glucose, fructose, galactose, lactose, maltose

Question 8

non-reducing sugar

Answer 8

-sucrose

Question 9

carbohydrates

Answer 9

-made up of C, H and O
-chemical formula C6H12O6

Question 10

monosaccharides

Answer 10

-basic unit of carbohydrates
-eg. glucose (subunit of cellulose, starch and glycogen), fructose and galactose
-chemical formula C6H12O6
-glucose functions as the raw material to undergo oxidation during respiration to release energy in living cells

Question 11

disaccharides

Answer 11

-two molecules of monosaccharides covalently bonded by condensation reaction
-glycosidic linkage is formed
-eg. maltose, sucrose and lactose
-chemical formula C12H22O11

hydrolysed into monosaccharides
-maltose —> glucose + glucose
-sucrose —> glucose + fructose
-lactose —> glucose + galactose

Question 12

polysaccharides

Answer 12

-many glucose subunits with glycosidic linkages

starch
-glucose molecules linear arrangement
-storage carbohydrate in plants, found in plant organs

cellulose
-glucose molecules linear arrangement
-provides mechanical protection to prevent plant cell from bursting or damage, main component of cell wall in plant cells

glycogen
-glucose molecules branched arrangement
-storage carbohydrates in mammals, stored in the liver and muscle cells

Question 13

starch and glycogen are storage carbohydrates

Answer 13

-easily hydrolysed into glucose, to be used as a raw material in respiration
-insoluble in water and do not change water potential of the solution in cells
-large molecules cannot diffuse across cell membranes, cannot be lost from the cell
-compact shape of molecules to store large number of glucose with a fixed volume

Question 14

cellulose is a structural carbohydrate

Answer 14

-few organisms possess enzymes that can hydrolyse cellulose thus is generally not used as a nutrient
-insoluble fibre found in plant foods

Question 15

lipids

Answer 15

-lipids (fats and oils) made up of C, H and O
-eg. triglycerides, phospholipids, steroids
-1 glycerol and 3 fatty acid molecules undergo a condensation reaction to form a triglyceride molecule
-hydrolysed into its subunits catalysed by lipase

functions of triglyceride
-storage molecules that can release large amount of energy upon oxidation during respiration
-used as an insulating material to prevent the lost of body heat
-used to make steroids and certain hormones, eg. sex hormones
-protect internal organs from mechanical shock

Question 16

proteins

Answer 16

-amino acids are the subunit
-made up of C, H, O, N and S

structure of an amino acid
-C atom in the centre of the amino acid
-amino group NH2, H atom and random group/ side chain R that is different for each type of amino acid

-amino acids undergo a condensation reaction to form a polypeptide
-peptide bonds between amino acids
-protein hydrolysed into amino acids catalysed by protease

-proteins can lose its 3-dimensional conformation/ denaturation
-when heated to higher than optimum temperature or placed in non-optimal pH

Question 17

test for starch

Answer 17

-add a few drops of iodine solution to test sample
-iodine solution changed from brown to blue-black/ remains brown

Question 18

test for reducing sugar

Answer 18

-place 2cm3 of food sample in a test tube. add 2cm3 of benedict’s solution to the food sample and mix. heat in a boiling water bath for 2-3 minutes.
-mixture turned from blue to (final colour) with precipitate/ remains blue

green has trace amounts
yellow has low amounts
orange has moderate amounts
brick-red has high amounts

Question 19

test for protein

Answer 19

-add 2cm3 of sodium hydroxide to 2cm3 of food sample and shake thoroughly. add 1% copper(II) sulfate solution, drop wise, shaking after every drop.
-mixture changed from blue to violet/ remains blue

Question 20

test for fats

Answer 20

-add 2cm3 of ethanol to a test tube with food sample and mix thoroughly. add 2cm3 of water to the mixture and shake the mixture.
-white emulsion formed when water is added/ mixture remained clear