biological materials

Question 1

define and describe how disaccharides are formed

Answer 1

-sugars linked by o-glycosidic bond
-when dehydration reaction joins two monosaccharides forming a glycosidic bond

Question 2

describe condensation reaction and hydrolysis

Answer 2

-condensation reaction is a chemical reaction in which two simple molecules are joined together to form a larger molecule with the removal of one molecule of water
-hydrolysis is the reaction in which a water molecule is required to break up a complex molecule into smaller molecules

Question 3

function of carbohydrates, fats, proteins

Answer 3

-immediate source of energy
-long term storage of energy and insulation, flavourings, cushion organs
-proteins for growth and repair of cells by synthesising new protoplasm, forms enzymes, hormones and antibodies, fluid and pH balance

Question 4

describe protein and its denaturation

Answer 4

-polymers of amino acid held together by peptide bonds with amine end of one amino acid linked to the carboxyl group of the next
-order of sequence of amino acid determines protein
-bonds holding polypeptide chains together are broken, causing it to unfold and lose 3D shape,

Question 5

why must proteins be broken down in the body

Answer 5

-protein molecules are too large to pass through pores of cell membrane
-first hydrolysed into short polypeptide chains and further hydrolysed into amino acids, which are soluble, simpler and smaller to diffuse through membrane via carrier proteins or active transport
-after entering body cells, linked up again to form protein needed by animal

Question 6

food test for starch, reducing sugar

Answer 6

-2cm3 of starch solution into test tube, record initial colour, add 2-3 drops of iodine solution, if blue black colouration is observed, starch solution and iodine mix, starch is present
-add equal volume of glucose solution and Benedict solution into test tube, record initial colour, shld be light blue, place test tube into boiling water bath for 2-3 mins, observe and record colour change, green to yellow/orange to brick red precipitate, copper oxide is formed, reducing sugar is present
-one drop of oil into test tube, 2 cm3 of ethanol and shake content thoroughly, record observation, clear solution observed, oil dissolves in ethanol, add 2cm3 of water and shake vigorously, initially 2 layers, cloudy white emulsion formed after mixing so fats are present
-2cm3 of protein suspension, one drop of sodium hydroxide and shake thoroughly, add copper 2 sulphate one percent drop by drop, shaking after every drop, violet solution means protein present

Question 7

characteristics of enzyme

Answer 7

-lowers activation energy needed to start energy speeding it up
-remains unchanged, can be used again, hence required in small amounts
-high specific
-affected by temperature and pH
-some catalyse reversible reaction
-some require coenzymes to be bound to them before they can catalyse
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Question 8

uses for protease, pectinate and lactase

Answer 8

-bio-active detergents to remove protein stains
-speed up the extraction of fruit juice from fruits by breaking down pectin
-helps to break down lactose to glucose and fructose to make lactose free products
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Question 9

describe lock and key

Answer 9

-substrate imagined to be key, whose shape is complementary to active site of enzyme
-once formed, products no longer fit into active site of enzyme and escape into surrounding medium, leaving AS free to receive further substrate molecules
-active site is flexible, binding to substrate induce small conformational change to fit substrate more snugly allowing for more efficient catalytic function

Question 10

effects of temperature on enzyme

Answer 10

-as temperature increase, KE of substrate molecules and enzyme increase, hence more successful collisions between them to form enzyme substrate complex, rate doubles every 10 degrees until optimum temperature, where enzyme is functioning the most effective
-beyond optimum, any increase will decrease rate of enzymatic reaction as enzymes become denatured
-excessive heat disrupts the intramolecular bonds which stabilise secondary and tertiary structures of enzyme, causes it to unfold and lose its shape, with the active site, irreversible
-if cooled, enzymes are inactivated, activity is low, but regain it when heated

Question 11

effects of pH on enzyme

Answer 11

-at optimum pH, intramolecular bonds are maintain tertiary structure are intact, conformation of active site is more ideal for substrate binding, FoSC
-different pH, H ions concentration change, alters the ionic charge on the basic and acidic groups on the side chains of amino acids of the enzyme molecule, ionic bonding the maintain conformation is disrupted.
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Question 12

describe competitive and non competitive inhibitor

Answer 12

-inhibitors with close resemblance to substrate molecular, competes with it for active site, may remain bound to enzyme excluding substrate. Can be reduced increasing substrate concentration of probability of ESC increase
-no structural resemblance, binds to region of enzyme not active site, puts a proportion of enzyme out of action as it results in change of shape of enzyme and hence more likely active site, maximum rate is never reached