IGCSE Biology Paper-4: Specimen Questions with Answers 204 - 205 of 279

Question 204

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Table shows different specialized cells and the average number of mitochondria each cell contains.

Different Specialized Cells and the Average Number of Mitochondria Each Cell Contains
specialized cell typeaverage number of mitochondria
liver cell1000 - 2000
red blood cell0
sperm cell25 - 75
heart muscle cell1500

Explain the differences between the average numbers of mitochondria in the cells shown in Table.


Mitochondria are cell organelles concerned with the process of aerobic respiration. Of all the cells in human body, it՚s the heart muscle cells with about 1,500 mitochondria per cell that contain far more mitochondria than any other organ in human body. The number of mitochondria reflects the energy requirement of a cell. Heart muscle cells have extra-special demand for ATP to keep the heart pumping. The number of the mitochondria varies with the cell type and functional stage.


A gene is involved in the production of the enzyme alcohol dehydrogenase.

Question 205 (1 of 2 Based on Passage)


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Describe the role of ribosomes in the synthesis of proteins such as enzymes.


Ribosomes provide framework on which protein synthesis takes place. The mRNA binds to the subunit of ribosome to form initiation complex. The main role of ribosome is its ability to catalyze the formation of peptide bonds between amino acids, so that the amino acids are incorporated into proteins. Ribosomes are dense granules without covering membranes.

Growing Polypeptide Chain

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