IGCSE Biology Paper-4: Specimen Questions with Answers 177 - 178 of 279

Passage

Maltose is changed into glucose.

Question 177 (1 of 5 Based on Passage)

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Which process, happening in all living cells, needs a constant supply of glucose?

Explanation

Our body uses cellular respiration to convert glucose to ATP and carbon dioxide using oxygen. Glucose moves through three stages in cellular respiration, glycolysis where glucose is converted to pyruvate, and two ATP and NADH are made. Either it is aerobic respiration or anaerobic respiration respiratory substrate is glucose.

Question 178 (2 of 5 Based on Passage)

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Name a hormone that causes glucose to be released from storage.

Explanation

Glucagon is a hormone that is involved in controlling blood sugar (glucose) levels. It is produced by the alpha cells, found in the islets of Langerhans, in the pancreas, from where it is released into the bloodstream. Glucagon՚s role in the body is to prevent blood glucose levels dropping too low. To do this, it acts on the liver in several ways:

  • It stimulates the conversion of stored glycogen (stored in the liver) to glucose, which can be released into the bloodstream. This process is called glycogenolysis.
  • It promotes the production of glucose from amino acid molecules. This process is called gluconeogenesis.
  • It reduces glucose consumption by the liver so that as much glucose as possible can be secreted into the bloodstream to maintain blood glucose levels.

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