IGCSE Biology Paper-4: Specimen Questions with Answers 230 - 231 of 279

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Shows part of the nitrogen cycle.

Protein Synthesis

Question 230 (3 of 6 Based on Passage)


Write in Short

Short Answer▾

State the name of the structure in a cell where protein synthesis occurs.


Ribosomes are smallest known electron microscopic without membrane, ribonucleo – protein particles attached either on RER or floating freely in the cytoplasm and are the sites of protein synthesis.


  • Ribosomes are also called protein factory of the cell or work branch of proteins.
  • Free ribosomes synthesize structural proteins and bounded ribosomes synthesize proteins for transport.
  • Ribosomes are essential for protein synthesis.
  • Help in the process of photosynthesis.
  • They are found numerously in actively synthesizing cells like liver cells, pancreas, endocrine, yeast cells and meristematic cells.
  • Ribosomes also store the proteins temporarily.
  • These also store rRNAs, which helps in protein synthesis.
  • Enzyme peptidyl transferase occurs in large subunit of ribosome which helps in protein synthesis.
  • Newly formed polypeptide is protected from degradation by cytoplasmic enzymes in large sub-unit of ribosomes before releasing it into RER lumen.

Question 231 (4 of 6 Based on Passage)


Write in Brief

One Liner▾

State the name of compound X in Fig.


Ammonia or Ammonium Ions

The conversion of in soil into nitrates and nitrites is called nitrification.

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