IGCSE Biology Paper-1: Specimen Questions with Answers 136 - 137 of 208

Question 136

Question

MCQ▾

What are the levels of organization of

  • the wall of a villus,
  • the small intestine?

Choices

Choice (4)

a.

wall of a villus-tissue, small intestine-organ system

b.

wall of a villus-cell, small intestine-organ

c.

wall of a villus-cell, small intestine-organ system

d.

wall of a villus-tissue, small intestine-organ

Answer

d.

Explanation

Small Intestine

Endodermal, longest part of alimentary canal present in the abdominal cavity, supported by a peritoneal membrane called mesentery. Wall of jejunum and ileum has circular or spiral internal fold called fold of kerckring or valvulae connivances. Also, numerous fingers like projection called villi project from the wall of lumen, increasing internal surface area about ten time. The distal end of ileum leads into the large intestine by ileo-caecal valve in man.

Parts of Small Intestine
Structure of an Intestine

Question 137

Question

MCQ▾

The table shows features that may be found in living cells.

Which features are found in a hepatocyte?

Choices

Choice (4)

a.

Cell wall-No, Central Vacuole-No, Chloroplast-Yes

b.

Cell wall-Yes, Central Vacuole-No, Chloroplast-No

c.

Cell wall-No, Central Vacuole-No, Chloroplast-No

d.

Cell wall-Yes, Central Vacuole-Yes, Chloroplast-Yes

Answer

c.

Explanation

Hepatocytes

  • Hepatocytes are large polyhedral cells (20 – 30 Å in diameter) that possess abundant RER and smooth endoplasmic reticulum (SER) ; numerous mitochondria, lysosomes, and peroxisomes; several Golgi complexes; and many lipid droplets and glycogen deposits.
  • They usually contain one round central nucleus; about 25 % of the cells are binucleated.
    • Occasionally, nuclei are polyploid.
  • Hepatocyte surfaces
    • Hepatocyte surfaces facing the space of Disse possess microvilli, which by increasing the surface area facilitates the transfer of materials (e. g. , endocrine secretions) between the hepatocytes and the blood.
    • Abutting surfaces of adjacent hepatocytes
  • frequently delineate bile canaliculi, small, tunnel-like expansions of the intercellular space. The bile canaliculi are sealed off from the remaining intercellular space by occluding junctions located on each side of each canaliculus.
  • possess microvilli that extend into the bile canaliculus
  • also have gap junctions
The Bile Canaliculi