3A biological molecules

Question 1

function of water in human body

Answer 1

-medium where chemical reactions occur
-transportation of digested products from ileum to other parts of the body, excretory products from from cells to kidney, hormones from glands to body
-key component of protoplasm, lubricants in joins, digestive juices, blood, tissue fluids
-in animals for respiration, digestion hydrolysis regulates body temperature
-plants for

Question 2

what is a polymer

Answer 2

-long molecule consisting of many similar or identical monomers linked together by covalent bonds

Question 3

what is condensation reaction

Answer 3

-chemical reaction that occurs when two simple molecules are joined together to form a larger molecule with the removal of one molecule of water

Question 4

what is a disaccharide and how is it formed

Answer 4

-disaccharides are sugars linked by an O-glycosidic bond
-when dehydration reaction joins two monosaccharides

Question 5

what is hydrolysis or hydrolytic reaction

Answer 5

-chemical reaction in which a water molecule is needed to break up complex molecule into smaller simpler molecules

Question 6

types of polysaccharides

Answer 6

-starch is long straight chains of glucose molecules that are energy storage in plant cells
-glycogen is highly branched polymer of glucose molecules, storage of carbs in animals in liver and muscles
-cellulose is straight chain of glucose molecules, structural carbohydrate in plant wall cells
-chitin is polymer of glucose with amino acids attached, primary constituent of exoskeleton

Question 7

enzyme hydrolysis of starch

Answer 7

-first broken down by amylase, breaking bonds to release maltose
-maltose molecules broken down by maltase, further bond breaking by maltase enzyme releases glucose

Question 8

what is glycerol and fatty acids and their components

Answer 8

-glycerol is three-carbon alcohol with a hydroxyl group (OH) attached to each carbon
-fatty acids consist of carboxyl group (COOH) attached to a long carbon skeleton

Question 9

what is an ester linkage

Answer 9

chemical bond formed between a carboxyl group of a fatty acid and a hydroxyl group of an alcohol

Question 10

why are fats insoluble in water

Answer 10

-water molecules from fats form hydrogen bonds with each other, excluding the fats

Question 11

function of fats

Answer 11

-source and stored form of energy
-insulation to prevent heat loss
-absorption and transport
-part of cell membrane
-reduces water loss from skin surfaces
-cushion organs
-forms hormones
-flavour to food

Question 12

what are proteins

Answer 12

-polymers of amino acids held together by peptide bonds, with the amine end of one amino acid linked to the carboxyl end of the next
-order of sequence of AA determine function of protein

Question 13

protein formation

Answer 13

-AA link up to form polypeptides, bond between two amino acids is strong peptide bonds which are formed in condensation reaction
-polypeptides may in turn be linked up to form longer chains of amino acids, coils held in place by weak bonds
-protein molecule is made up of one or more long chains of amino acids folded together, coiled or folded to give a three dimensional shape

Question 14

describe the primary, secondary, tertiary and quaternary structure of proteins

Answer 14

primary - linear sequence of amino acids composing of polypeptide chain
secondary - alpha helixes or beta pleated sheets stabilised by hydrogen bonds
tertiary - superimposed folding of secondary structure to form a globular or ball like molecule
quaternary - polypeptides chains liked together in a specific manner

Question 15

how is protein denatured

Answer 15

-weak bonds broken easily by heat and chemicals such as acids and alkalis, losing protein’s three dimensional shape and hence denatured, involving a loss of function of protein

Question 16

what is protein denaturation

Answer 16

-protein denatured when it unfolds and loses its 3 dimensional shape, conformation, may be irreversible depending on severity

Question 17

function of protein and what does protein deficiency lead to

Answer 17

-synthesis of new protoplasm, for growth and repair of worn out body cells
-form hormones, antibodies, enzymes
-pH and fluid balance
-protein deficiency disease in children which is kwashiorkor, swollen stomach, cracked and scaly skin

Question 18

why and how are proteins digested in the body

Answer 18

-animal cannot directly absorb protein as protein molecules are too large to pass through living cell surface membrane and hence must be broken down by enzyme during digestion
-undergo series of hydrolytic reactions and are first hydrolysed into polypeptides which are hydrolysed into amino acids
-amino acids simpler and smaller molecules than proteins that are soluble in water, small enough to diffuse through living cell surface membrane via carrier proteins or active transport, hence easily absorb into animal’s body
-after entering body cells, linked up again to form protein needed by animal

Question 19

why are lipids more suitable as a long term storage of energy than carbohydrates and proteins

Answer 19

Lipids release significantly more energy per gram upon metabolism than carbohydrates and proteins, making them a more efficient option for long-term energy storage.

Question 20

recite food test for starch

Answer 20

-add 2cm3 of starch solution into test tube
-record initial colour
-add 2-3 drops of iodine solution in test tube and record colour change
-blue-black colouration observed when yellow brown iodine mixes with starch solution so starch present

Question 21

recite food test for reducing sugar

Answer 21

-add 2cm3 of glucose solution and Benedicts solution into test tube and record initial colour for light blue solution
-place test tube containing mixture into boiling water bath for 2-3 minutes and observe and record colour change
-colour changes to green then yellow before brick red precipitate observed so reducing sugar observed

Question 22

recite food test for fats

Answer 22

-place one drop of oil into test tube and add 2cm3 of ethanol and shake contents thoroughly and record observation
-clear solution observed as oil dissolve in ethanol
-add 2cm3 of water into test tube of oil-ethanol mixture and shake vigorously and record observation
-2 layers initially and now its cloudy white emulsion observed after mixing

Question 23

how to ensure fair test for food test

Answer 23

-equal volumes of reagents and sample
-equal duration of boiling water for Benedicts test
-avoid contamination by ensuring droppers are not in contact with test tubes

Question 24

recite food test for proteins

Answer 24

-place 2cm3 of protein suspension into test tube and add 1cm3 of sodium hydroxide solution into test tube and shake thoroughly
-add 1% copper 2 sulphate solution drop wise, shaking after each drop and record observation
-violent solution observed