IGCSE Biology Paper-4: Specimen Questions with Answers 199 - 200 of 279

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Question 199

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Short Answer▾

Shows a computer model of the enzyme alcohol dehydrogenase, which is the enzyme responsible for breaking down alcohol.

Enzyme Alcohol Dehydrogenase

Enzymes have a specific three-dimensional shape.

Explain why the shape of an enzyme is important.

Explanation

Proteins consist of combinations of amino acids. Body proteins include structural proteins, enzymes, hormones, and antibodies. The shape of an enzyme allows it to speed up a biological reaction. Enzymes act on substrates by attaching to them. The part of an enzyme that one or more substrates molecules can attach to is called the active site. Enzymes can also catalyze the synthesis (joining) of two substrates to form one product. Each different type of enzyme will usually catalyze one biological reaction. Enzymes are specific because different enzymes have different shaped active sites.

The shape of an enzyme՚s active site is complementary to the shape of its specific substrate or substrates. This means they can fit together.

Enzyme Type 1,2 and 3

Passage

Soon after starting physical activity the concentration of carbon dioxide in the blood increases.

Question 200 (1 of 3 Based on Passage)

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Short Answer▾

State the effect on breathing of an increase in carbon dioxide concentration in the blood.

Explanation

When concentration in blood increases, breathing becomes faster and deeper. The effect of rising concentration is due to decrease in affinity of for ​. Thus, the released in the tissues accelerates the delivery of (called Bohr effect) , due to-which breathing becomes faster and deeper.

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