IGCSE Biology Paper-1: Specimen Questions with Answers 149 - 150 of 208

The word “Prokaryote” means a cell

Answer

b.

Explanation

Features of Prokaryotic Cell

• Prokaryotic cells are morphologically most primitive cells.
• A single membrane surrounds the cell. It is without membrane bound nucleus.
• Prokaryotic cells are devoid of membrane bound organelles like plastids, mitochondria and advanced (9 + 2) flagella.
• They reproduce asexually by transverse binary fission or budding.
• Prokaryotic cells are represented by bacteria, cyanobacteria (blue green algae) , Mycoplasma and PPLO (pleuro-pneumonia like organisms) .
• Bacteria are unicellular organisms with prokaryotic cellular organization. They were first discovered by Anton van Leeuwenhoek (1676) in pond water and tartar of teeth. The bacteria are the simplest living organisms reproduce by fission and are mostly pathogenic on human beings.
• Bacteria are found in all places like hot springs, beneath the icebergs, in the intestine of man, deep in the soil, in sea water etc.

Which graph shows the effect of temperature on the activity of an enzyme?

Answer

d.

Explanation

Temperature: Enzyme functions optimally at certain temperature. As the temperature increases the kinetic energy also increases, molecules move faster, and it increases the chance of substrate colliding the enzyme’s active site and binding followed by reaction. But if the temperature is too high, the enzyme protein denatures (cools), thereby destroying the shape of active binding site (cannot bind to the substrate anymore) and decreasing the enzyme reaction rate.