OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

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What is the significance of enzymes in mitochondria?

Digestive functions
Energy production
Speeding up chemical reactions
Structural support

The correct answer is: Speeding up chemical reactions

Enzymes in mitochondria play a crucial role in speeding up chemical reactions, particularly those involved in cellular respiration. Mitochondria are often referred to as the powerhouse of the cell because they are responsible for producing ATP (adenosine triphosphate), which is the primary energy currency of the cell. The enzymatic reactions that occur within the mitochondria, particularly in the citric acid cycle and the electron transport chain, facilitate the conversion of nutrients into usable energy efficiently. Each enzyme in these pathways lowers the activation energy required for the reactions, allowing them to proceed at a much faster rate than they would without the enzymes. Thus, the efficient functioning of these enzymes is essential for maintaining the energy balance and metabolic processes of the cell.