IGCSE Biology Paper-4: Specimen Questions with Answers 215 - 218 of 279

Passage

Pepsin is a protease enzyme found in the alimentary canal.

Question 215 (1 of 2 Based on Passage)

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State the organ in the alimentary canal where pepsin is secreted.

Explanation

Pepsin is a stomach enzyme that serves to digest proteins found in ingested food. Gastric chief cells secrete pepsin as an inactive zymogen called pepsinogen. Parietal cells within the stomach lining secrete hydrochloric acid that lowers the pH of the stomach which activates pepsin.

Question 216 (2 of 2 Based on Passage)

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Name the product formed from the digestion of proteins by protease enzymes.

Explanation

Digestion of Protein:

Protein Food

Passage

A researcher used a light microscope to observe epithelial cells from a human cheek.

Fig. is a photograph that the researcher made of these cells.

Human Cheek

Question 217 (1 of 3 Based on Passage)

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State how the shape of the cells shown in Fig. differs from the shape of a palisade mesophyll cell in a leaf.

Explanation

Human cheek cell represents animal cell while palisade mesophyll cell represents plant cell.

Animal and Plant Cell

Question 218 (2 of 3 Based on Passage)

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The cells in Fig. each have a cell membrane.

State one of the functions of a cell membrane.

Explanation

Functions of Cell Membrane

  • They control the flow of material through them and provides passage for different substances.
  • It is differentially permeable, solute particles (1 - 15 Å) can pass through it.
  • It is not only providing mechanical strength but also acts as a protective layer.
  • Plasma membrane is responsible for the transportation of materials, molecules, ions etc.
  • It helps in osmoregulation.
  • Diffusion of gases take place through plasma membrane by simple and facilitated diffusion.
  • Transport of ions, small polar molecules through active (energy used) and passive transport (energy not used) .
  • Gases like and diffuse rapidly in solutions through membranes.
  • Ions and small polar molecules diffuse slowly through the membranes.
  • Some solute molecules or ions first bind with certain specific carrier or transport proteins called permeases.
  • Water as well as some solute molecules and ion pass through membranes pores; pores are always bordered by channel proteins.
  • When diffusion takes place through channel, called simple diffusion and through carrier proteins, called facilitated diffusion.

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