IGCSE Biology Paper-1: Specimen Questions with Answers 127 - 128 of 208

Question 127

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Question

MCQ▾

Living cells cannot be observed in an electron microscope because

Choices

Choice (4)
a.They are transparent and therefore remains invisible
b.They are killed by fast beam of electron
c.The heat generated by electrons injurious to cell and its organelles
d.They lose water vapor and disturb the vacuum of the microscope

Answer

b.

Explanation

Cell observed by electron microscope are dead that’s because the particle beam of electrons used to illuminate a specimen also destroys the samples, meaning that electron microscopes can’t be used to image living cells.

Question 128

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Question

MCQ▾

Given below is a common process.

Cell Membrane

Cell Membrane

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The process shown in the above diagram is

Choices

Choice (4)
a.Facilitated diffusion
b.Simple diffusion
c.Catalysis
d.Active transport

Answer

b.

Explanation

Diffusion: The movement of the molecules of gases, liquids, and solutes from the region of higher concentration to the region of lower concentration is known as diffusion.

Or

Diffusion is the net movement of molecules or ions of a given substance from a region of higher concentration to lower one by virtue of their kinetic energy.

Or

It is the movement of molecules from high diffusion pressure to low diffusion pressure.

  • Phenomenon of diffusion can be observed every day.
  • It may occur between gas and gas (e. g. , diffusion of ammonia into air), liquid and liquid (e. g. , diffusion of alcohol into water), or solid and liquid (e. g. , diffusion of sugar into water). The diffusion of one matter is dependent on other. That is why many gases and solutes diffuse simultaneously and independently at different rates in different direction at the same place and time, without interfering each other. From soil, water, and ions of simple inorganic salts pass into plants through the root cells by a process which is diffusion, though greatly modified by other factors. The water and solutes pass through the dead and living vessels and from cell to cell by diffusion. When a crystal of copper sulphate is placed in a beaker containing water, a dense blue colour is seen around the crystal.