IGCSE Biology Paper-4: Specimen Questions with Answers 151 - 153 of 279

Passage

An image of a germinating seed showing the growing root

Cell Membrane

Question 151 (3 of 4 Based on Passage)

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Describe and explain how the structures seen at J are adapted for their function.

Explanation

Root Hairs

They are enlargements of special epiblema cells called trichoblasts and occurs in a particular zone of young root called root hair zone. A root hair cell has vacuolated protoplast with nucleus present towards the apical part of hair. They are specialized to absorb water from soil crevices. They also hold soil particles.

Function of Root Hairs

The function of root hairs is to collect water and mineral nutrients that are present in the soil and take this solution up through the roots to the rest of the plant. As root hair cells do not carry out photosynthesis, they do not contain chloroplasts.

Cell Membrane and Cell Wall

Question 152 (4 of 4 Based on Passage)

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Name the chemical that controls this response.

Explanation

Auxins are the main hormones responsible for cell elongation in phototropism and gravitropism. They also control the differentiation of meristem into vascular tissue and promote leaf development and arrangement.

Passage

Alcohol can be made by the microorganism yeast.

Question 153 (1 of 2 Based on Passage)

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Name the organ that breaks down alcohol in the human body.

Explanation

Most of the ethanol in the body is broken down in the liver by an enzyme called alcohol dehydrogenase (ADH) , which transforms ethanol into a toxic compound called acetaldehyde (CH3CHO) , a known carcinogen.