Biology Revision – Chemical and Cellular Basis of Life (1)

Elemental Composition of Living Organisms

Multiple Choice Questions

1. In the term trace element, the adjective trace means that
the element is required in very small amounts.
Correct. Do you remember the definition of trace elements. It has several components; 1. Present in more than 0.01% of weight of the organisms, 2. Essential elements in small amounts.
the element can be used as a label to trace atoms through an organism’s metabolism.
Incorrect. Try again.
the element is very rare on Earth.
Incorrect. Try again.
the element enhances health but is not essential for the organism’s long-term survival.
Incorrect. Try again.
the element passes rapidly through the organism.
Incorrect. Try again.

2. Which of the following is true?
Cl is an excessive element in human body.
Correct. Na, Fe and Cl are elements that sometimes present as excessive elements in some organisms and sometimes as trace elements in some organisms. In human body they are excessive elements, which means that they present in more than 0.01% of body weight.
About 30% of natural elements present in living organisms.
Incorrect. Try again.
90% of human body weight is carbon.
Incorrect. Try again.
Ca is a trace element in plants.
Incorrect. Try again.
Trace elements are not essential for the survival of living beings.
Incorrect. Try again.

3. Choose the correct response.
Excessive elements are more than 99.9 % of the body weight.
Correct. You should know this.
94% of weight in organisms consists of C, H, O, N, P and S.
Incorrect. Try again.
Zn is not essentially needed for the organisms for their survival.
Incorrect. Try again.
N makes up the backbone of DNA molecule.
Incorrect. Try again.
Ca is a component of diatom shell.
Incorrect. Try again.

4. Which of the following is a correct element-function relationship?
Phosphorus – makes up the backbone of RNA molecule
Correct.
Sulphur – muscle contraction
Incorrect. Try again. (calcium)
Magnesium – nerve impulse transmission
Incorrect. Try again. (Sodium, Potassium)
Chromium – component of thyroxine
Incorrect. Try again. (Iodine)
Calcium – component of chlorophyll molecule
Incorrect. Try again. (Magnesium)

5. Which one of the following element is needed for the synthesis of chlorophyll, but is not itself a component of chlorophyll?
Iron (Fe)
Correct.
Carbon (C)
Incorrect. Try again.
Oxygen (O)
Incorrect. Try again.
Magnesium (Mg)
Incorrect. Try again.
Nitrogen (N)
Incorrect. Try again.

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