IGCSE Biology Paper-2: Specimen Questions with Answers 184 - 185 of 203

Question 184

Question

MCQ▾

What makes alveoli suitable as a gas exchange surface?

Choices

Choice (4)

a.

Large surface area- √ , Well-developed blood capillary- × , Cell wall- ×

b.

Large surface area- √ , Well-developed blood capillary- √ , Cell wall- ×

c.

Large surface area- √ , Well-developed blood capillary- √ , Cell wall- √

d.

Large surface area- √ , Well-developed blood capillary- × , Cell wall- √

Answer

b.

Explanation

  • The movement of gases in a contained space (in this case, the lungs) is random, but overall diffusion results in movement from areas of high concentration to those of low concentration. The rate of diffusion of a gas is primarily affected by
    • Concentration gradient: The greater the gradient, the faster the rate.
    • Surface area for diffusion: The greater the surface area, the faster the rate.
    • Length of the diffusion pathway: The greater the length of the pathway, the slower the rate.
The Movement of Gases in a Contained Space

Question 185

Question

MCQ▾

The diagram shows part of the alimentary canal and associated organs.

The Diagram Shows Part of the Alimentary Canal and Associate …

Which structures secrete enzymes that digest fats?

Choices

Choice (4)

a.

Only Q

b.

Only S

c.

Only R

d.

All of the above

Answer

c.

Explanation

Functions of Liver

Liver, the largest gland of vertebrate body, is an essential organ, which performs many functions –

  • Secretion: It secretes bile, which is a complex watery fluid containing bile salts (Na taurocholate and glycocholate) , bile pigments (biliverdin and bilirubin) , cholesterol, mucin, lecithin, and fats etc. The bile aids in intestinal digestion as it breaks and emulsifies the fat, prevents putrefaction of food by checking the growth of bacteria, makes the Chyme better suited for pancreatic digestion by neutralizing the acid in it, and helps in the absorption of fat from the intestine.
  • Excretion: In the liver, haemoglobin of the worn out erythrocytes breaks down to bile pigments bilirubin and biliverdin. The liver excretes these pigments as a major constituent of bile, a part of which carried to the kidney through general circulation for excretion through urine. The bile pigments are also converted in the bowel into Stercobilin which colours the faeces but, apart from this, are waste products having no other function

Functions of Bile

  • Emulsification of fats.
  • Helps in absorption of fat-soluble vitamins.
  • Increases alkalinity to make the medium suitable for enzymatic action.
  • Elimination of heavy metals such as Cu, Hg, Zn etc.
  • Elimination of excess of bile pigments.
  • Stercobilin and urobilin is formed by bilirubin and biliverdin is responsible for colouration of faeces.

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