Chemical elements

Question 1

How many elements are found in the human body?

Answer 1

26

Question 2

Name the four major elements in order of prevalence

These constitute approx. 96% of the body’s mass

Answer 2

1. Oxygen
2. Carbon
3. Hydrogen
4. Nitrogen

Question 3

Name the eight lesser elements in order of prevalence

These consitute approx. 3.6% of the body’s mass

Answer 3

1. Calcium
2. Phosphorus
3. Potassium
4. Sulfur
5. Sodium
6. Chlorine
7. Magnesium
8. Iron

Question 4

How many trace elements are there?

These constitute 0.4% of the body’s mass

Answer 4

14

Question 5

What is the significance of the major element oxygen? (2)

Answer 5

1. Part of water and many carbon-containing molecules
2. Used to generate ATP

Question 6

What is the significance of the major element carbon? (1)

Answer 6

Forms backbone chains and rings of all organic molecules (carbs, lipids, proteins, nucleic acids)

Question 7

What is the significance of the major element hydrogen? (2)

Answer 7

1. Part of water and most organic molecules
2. Ionised form (H⁺) makes body fluids more acidic

Question 8

What is the significance of the major element nitrogen? (1)

Answer 8

Component of all proteins and nucleic acids

Question 9

What is the significance of the lesser element calcium? (2)

Answer 9

1. Contributes to hardness of bones and teeth
2. Ionised calcium (Ca²⁺) plays a role in blood clotting, release of some hormones, contraction of muscle and more

Question 10

What is the significance of the lesser element phosphorus? (2)

Answer 10

1. Component of nucleic acids and ATP
2. Required for normal bone and tooth structure

Question 11

What is the significance of the lesser element potassium? (2)

Answer 11

1. Ionised form (K⁺) is most plentiful cation in intracellular fluid
2. Needed to generate action potentials

Question 12

What is the significance of the lesser element sulfur? (1)

Answer 12

Component of many proteins and some vitamins

Question 13

What is the significance of the lesser element sodium? (3)

Answer 13

1. Ionised form (Na⁺) is most plentiful cation in extracellular fluids
2. Needed to generate action potentials
3. Essential for maintaining water balance

Question 14

What is the significance of the lesser element chlorine? (2)

Answer 14

1. Ionised form (Cl⁻) is the most plentiful anion in extracellular fluid
2. Essential for maintaining water balance

Question 15

What is the significance of the lesser element magnesium? (1)

Answer 15

Ionised form (Mg²⁺) is needed for action of many enzymes

Question 16

What is the significance of the lesser element iron? (1)

Answer 16

Ionised forms (Fe²⁺ and Fe³⁺) are part of haemoglobin and some enzymes