BIOLOGY PAPER 3 Marking Scheme - 2019 KCSE Prediction Answers Set 1

FOOD COMPOUND

PROCEDURE

OBSERVATION

CONCLUSION

Starch

To 2cm³ of solution L add drops of iodine 1mk

Colour turns brown /yellow ½ mk

Starch absent ½ mk

Reducing sugar

To 2cm³ of solution L ,add benedicts solution and boil 1 mark

Colour changes from blue to green to yellow/orange ½ mk

Reducing sugars present ½ mk

proteins

To 2cm³ of solution L add 3 drops of NaOH followed by drops of CuSO₄ and shake 1mk

solution remains blue ½ mk

Protein absent ½ mk

Ascorbic acid

(vitamin c)

To 2cm3 of solution DCPIP add solution L dropwise shaking till in excess 1mk

DCPIP decolourised ½ mk

Vitamin C /Ascorbic acid present ½ mk

Specimen

steps

identity

A

1b,3a;

Arachnida

B

1a,2a,4a;

Pisces

C

1b,2b,5b,6b;

Chilopoda

D

1a,2a,4b,7b,8a

Reptilia

E

1a,2a,4b,7a;

Aves

F

1b,3b,5a;

Insecta