Chapters 1.1-1.3 Biological Molecules

Question 1

Monomers

Answer 1

smaller units from which larger molecules are made.

Question 2

polymers

Answer 2

molecules made from a large number of monomers joined together

Question 3

Polymerisation

Answer 3

the process by which polymers are formed

Condensation reaction occurs whenever polymerisation takes place

Question 4

Condensation reaction

Answer 4

a reaction involving the removal of a water molecule to create a chemical bond between two molecules

Question 5

Hydrolosis

Answer 5

a reaction involving the addition of a water molecule to break a chemical bond between two molecules

Question 6

Large molecules often contain carbon. Explain why this is.

Answer 6

carbon atoms readily link to one another to form a chain

Question 7

1.glucose+_glucose____——> _________+water

2.glucose+_galactose____——> _________+water

3.glucose+_fructose____——> _________+water

the reactants side = monosaccharides
products side = disaccharides

Answer 7

1. maltose+ water
2. Lactose +water
3. Sucrose +water

These are all DISACCHARIDES (2monosac. joined to form them)

Question 8

properties of monosaccharides and formula?

Answer 8

1. sweet tasting
2. soluble
3. ALL are reducing sugars
3. General formula (CH2O)n

n= any no. 3—>7

Question 9

what reaction do monosaccharides undergo to form disaccharides

Answer 9

condensation

Making LARGER molceules= COND.

BREAKING LARGER molecules into SMALLER molecules= HYDROLYSIS

Question 10

Monomers= MyAuntieNever(Acts Good)

state 4 monomers and the polymers they form

Answer 10

1. Monosacc= carbohydrates
2. Amino A= proteins
3. Nucleotides= DNA and RNA
4. Alpha Glucose= starch, cellulose, glycogen

beta glucose = makes cellulose

Question 11

reducing sugar

Answer 11

a sugar that can donate e- to another chemical, in this case benedict’s reagent

Question 12

reduction

Answer 12

a chem reaction involving the gain of e- or hydrogen

in this case, benedict’s reganet is gaining e- from a reducing sugar

Question 13

explain how to carry out the benedict’s test

Answer 13

1. Add 2cm3 of food sample in tt. If the food sam. is not alr liquid, grind it with water
2. Add equal volume of ebnedcit’s reanget to the same test tube
3. Heat gently in water bath (boiling) for 5 minutes. If a reducing sugar is present then the solution will turn brown-orange

Question 14

explain why benedict’s reagernt turns red when heated with a reducing sugar

Answer 14

sugar donates e- that reduce BLUE copper (II) sulfate to ORANGE copper (I) oxide

Question 15

suggest a way, other than comapring colour changes, in which different concentrations of red. sugars can be estimated

Answer 15

1. dry the percipitate in each sample
2. weight it
3. the heavier it is- the more red sugar is present

Question 16

explain why its not possible to distinguish between very concentrated samples, even when the concentrations are different

Answer 16

once all the copper (II) sulfate has been reduced to copper (i) oxide, further amounts of red. sugar cannot make a difference

Question 17

how polysacc formed via the condensation of many gluc units?

Answer 17

2 monosac. undergo a condensation reaction, where a water molecule is removed to form a GLYCOSIDIC BOND (alpha 1,4 glyco bond) between the molecules (forming a disacc). This reaction is repeated until a polysacc is formed.

Question 18

how to carry out a test for non reducing sugars

Answer 18

1. Carry out benedict’s test first = if there is no colour change there are no reducing sugars present
2. 2cm3 of food sample in a new tt and add 2cm3 of dilute HCL and heat in gently boiling water bath for 5 mins (this will hydrolyse any disaccharide presentinto its constitunent monosacc.)
3. slowly add sodium hydrogencarbonate to tt as this will neutralise the HCL (bc benedict’s r. cannot work in acidic conditions). Use pH paper to test that the sol is alkaline.
4. Re-test the resulting sol by heating it with 2cm3 of benedict’s reagent in a gently boiling water bath.
5. If the sol turns orange-brown then a non-red sugar was present in the og sample; this is bc the reducing sugars are now produced after hydrolysing the non-red sugars

Question 19

non red sugars

Answer 19

e.g sucrose = they dont change the colour of benedict’s reagent when they’re heated with it

Question 20

Starch= Iodine

how do u carry out a test for starch

Answer 20

1. Add 2cm3 of sample being tested to tt
2. Add 2 drops of iodine solution and stir or shake
3. Yellow——> blue-black in the presence of starch

Question 21

why does the temp have to be lower (40”c) if hydrolysis is being carried out via an enzyme

Answer 21

enzymes denature at high temp
therefore preventing them from functioning