IGCSE Biology Paper-4: Specimen Questions with Answers 272 - 274 of 279

Passage

Type 1 diabetes is caused by the immune system destroying body cells.

Question 272 (2 of 2 Based on Passage)

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Suggest which organ in the body is attacked by the immune system to cause Type 1 diabetes.

Explanation

Type 1 diabetes is a condition that occurs when the immune system mistakenly attacks and destroys healthy body tissue. With type 1 diabetes, an infection causes the immune system to mistakenly attack the beta cells in the pancreas that make insulin.

Question 273

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Table shows some information about the functions of the components of blood.

Complete Table.

Some Information About the Functions of the Components of Blood
functiontype of cell
production of antibodies
phagocyte
promotes blood clotting
transports oxygen

Explanation

Some Information About the Functions of the Components of Blood
functiontype of cell
production of antibodiesB lymphocytes
Macrophagephagocyte
promotes blood clottingPlatelets
transports oxygenRBCs
Elements of the Blood

Question 274

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State the word equation for anerobic respiration.

Explanation

Process of anaerobic respiration: In this process pyruvate which is formed by glycolysis is metabolized into ethyl alcohol or lactic acid and in the absence of oxygen. Glycolysis is occurring in cytoplasm so the site of anaerobic respiration is cytoplasm.

Formation of ethyl alcohol: When oxygen is not available, yeast and some other microbes convert pyruvic acid into ethyl alcohol. This is two-step process as explained below:

In the first step pyruvic acid is decarboxylated to yield acetaldehyde and . In the presence of Mg ++ and TPP (Thiamine pyrophosphate) pyruvate carboxylase.

In the second step acetaldehyde is reduced to ethyl alcohol by formed in the glycolysis.

Production of lactic acid: In this process hydrogen atoms removed from the glucose molecule during glycolysis are added to pyruvic acid molecule and thus lactic acid is formed.

Lactic acid is produced in the muscle cells of human beings and other animals. During strenuous physical activity such as running, the amount of oxygen delivered to the muscle cells may be insufficient to keep pace with that of cellular respiration. Under such circumstances lactic acid is formed which accumulates in the muscle cells and causes muscle fatigue.