Answers to Hands on Pg 71-72

Section A

1. a) i) Daily protein need = 20/7.5 = 2.67 gkg^-1 body mass

ii) Daily protein need = 70/55 = 1.27 gkg^-1 body mass

b) A child needs more protein to build new cells and tissues for growth. A teenage boy at the age of 17 has almost reached puberty. Hence, less protein is needed because his growth rate is slower.

c) Meat and soya beans contain all the essential amino acids needed by our body. However, vegetables do not contain all the essential amino acids.

d) Vitamin D is needed for the absorption of calcium and phosphorus. A growing child needs more calcium and phosphorus for the formation of strong bones and teeth. Hence, a child needs more vitamin D. As for the teenage girl, she needs less vit D because her bones and teeth are almost completely formed.

e) A teenager needs more iron for the production of haemoglobin to transport oxygen because he/she is more active and bigger in size as compared to a child. A teenage girl will need more iron than a teenage boy because she loses blood through menstruation.

2. a) i) To study the need of light for photosynthesis

ii) To study the need of carbon dioxide for photosynthesis.

b)i) To prevent the covered part of the leaf from receiving sunlight.

ii) Solution X is potassium hydroxide solution and is used to absorb carbon dioxide from the air around the leaf.

c) i) Dark blue on the part of the leaf which is not covered with black paper.

ii) The whole leaf gives a yellowish brown colour.

d) No photosynthesis takes place on the covered part of leaf P as it does not receive any light. Leaf Q shows the absence of starch because there is no carbon dioxide for photosynthesis to take place.

e) The plant needs to be put in a dark room for 24 hours to ensure the leaves of the plant do not contain starch at the start of the experiment.