New Senior Secondary Mastering BiologyChapter 5

Suggested answers to Exercise and Reading to learnp.1/5

Suggested answers to Exercise and Reading to learn

(Note: The overseas examination boards bear no responsibility for the suggested answers contained in this publication. Answers for HKCEE and HKALE questions are not available due to copyright restrictions.)

Ch 5Food and humans

Exercise

Multiple-choice questions (p. 5-31)

1D / 2D / 3A / 4B
5D / 6D / 7D

Short questions (p.5-32)

8HKCEE Human Biology 2001 I Q4b

9HKCEE Biology 2005 I Q6

10

Constituent of the diet / Description of one effect of deficiency
vitamin A / reduced ability to synthesize retinal pigments
vitamin C (ascorbic acid) / scurvy / bleeding from small blood vessels or gums / poor wound healing
calcium / rickets / weak bones or teeth / bleeding / decreased muscular activity
iron / reduced ability of the blood to carry oxygen

1m x 4

11aBananas: 75.70.5m

Grapes: 84.70.5m

bFat1m

cApple contains more carbohydrate / pears contain less carbohydrate.1m

Apple contains less water / pears contain more water.1m

dUse several samples of each fruit / Repeat experiment0.5m

Calculate average result0.5m

12aiB, because it is rich in vitamin A.1m

iiA, because it contains the largestamount of fats. (Though E also containsthe same amount of carbohydrates,fats give more energy thancarbohydrates for the same amount.) 1m

iiiC, because it contains the largestamount of proteins which areimportant for growth. 1m

ivE, because it contains carbohydrates only and sugar is a kind of carbohydrates.

1m

vA, because it is rich invitamin D.1m

viB, because it is rich invitamin C.1m

bThis is because high temperature willdestroy vitamin C in food.1m

Structured questions (p.5-33)

13a

Nutrient / One rich source / One function of nutrient
carbohydrate / potato / energy source / energy storage / component of DNA
fat / lipid / butter / insulation around nerve cells
protein / meat / growth and repair / source of amino acids / formation of enzymes, hormones and antibodiesOR protein-containing tissue / energy source
vitamin A / carrot / (good) night vision / allows rods to function / prevents night blindness
vitamin D / oily fish / absorption of calcium OR phosphate / deposition of calcium OR phosphate in bones OR teeth / helps harden bones OR teeth / prevents rickets

1m x 5

bBar for pregnancy higher than normal1m

Bar for breast feeding higher than pregnancy (and normal)1m

cAny two from:1m x 2

Protein needed to allow foetus / baby to grow / develop1m

Growth of mother’s cells / tissues 1m

Used for growth of named tissue (maternal or foetal), e.g. placenta, umbilical cord, bone, muscle 1m

For production of milk 1m

After birth baby growing more quickly1m

Repair mother’s tissues damaged during birth1m

14aDifferent people have different needs.1m

RNI changes with age / gender / sex / pregnancy / lactation.1m

biAny two from:1m x 2

Inflammation (of eyes)1m

Scarring / drying of cornea 1m

Loss of sight / blindness1m

Night blindness / poor vision in dim light / rod cells do not function1m

iiMinimum mass of carrot needed =  100 4 g

(2m for correct answer and working, 1m for incorrect answer but correct working,1m for answer = 4.16)

ciMade in skin under sunlight1m

From cholesterol1m

iiAny two from:1m x 2

Absorption of calcium in gut1m

Deposition of calcium in bones and teeth1m

Makes bones hard / stops bones from going soft1m

Prevent rickets1m

15aiMix equal volume of Benedict’ssolutions and liquid food sample ina test tube. 1m

Boil the test tube ofmixture in a water bath for a few minutes.Observe for any changes. 0.5m

A brick-red precipitate indicates thepresence of reducing sugars.0.5m

iiTransfer a drop of liquid food sampleto the well of a spot plate.0.5m

Dip a piece of Albustix paperinto the sample and observe any colourchange.

0.5m

If protein is present, the paper will change fromyellow to green.1m

bC and D0.5m x 2

C shows positive results with iodine test, testusing Albustix paper and DCPIP test.

0.5m

D shows positive results with Benedict’stest and iodine test.0.5m

cC: starch, proteins and vitamin C2m

D: reducing sugars and starch2m

dThe carbohydrate may be a non-reducingsugar with a sweet taste. It does not givea positive result with Benedict’s testbecause it is non-reducing. 1m

It may be sucrose.1m

eTest for glucose using Clinistix paper.1m

If glucose is present, the paper willchange from pink to purple.1m

16HKCEE Human Biology 1993 I Q4c

17HKCEE Biology 2000 I Q2a

Essay (p.5-35)

18Carbohydrates contain the elements: carbon, hydrogen and oxygen.1m

Monosaccharides (e.g. glucose and fructose) are the simplest sugars of whichother carbohydrates are composed. 2m

Glucose is a source of energy. It is the substrate in aerobic and anaerobic respiration.1m

Two glucose molecules can combineto form a disaccharide, maltose, by condensation.

1m

A glucose and a fructose molecule can combine to form another disaccharide, sucrose, by condensation. 1m

Disaccharides can be hydrolyzed into monosaccharides.1m

Polysaccharides are long chains of monosaccharides joined together by condensation. Starch, glycogen and cellulose are examples of polysaccharides. 2m

Starch provides large number of glucose molecules forrespiration.1m

Glycogen is the storage form of glucose in the body.1m

Cellulose is the major component of plant cell walls.1m

Reading to learn (p. 5-36)

1The amount of carbohydrates in a high protein diet is very small.1m

When fewer carbohydrates are eaten, the body will break down the stored fat (instead of carbohydrates) to release energy. 1m

2Fruits and grains are rich in dietary fibre.1m

If fruits and grains are not consumed for a long period of time, constipation may result.

1m

3A high protein diet usually contains a lot of lipids including saturated fatty acids and cholesterol, 0.5m

which increase the level of cholesterol in the blood. 0.5m

Excessive cholesterol may deposit on the inner walls of the blood vessels and lead to a blockage. Heart disease may result. 1m

4No, a high protein diet is not a balanced diet. 0.5m

A balanced diet should contain all the food substances in the right amounts and proportions. 1m

The high protein diet contains large amounts of proteins and lipids, 0.5m

but little or no carbohydrates and dietary fibre.1m

OxfordUniversity Press 2009