IB BIO TOPIC 3.1 : CHEMICAL ELEMENTS & WATER

Question 1

4 Most frequently occurring chemical elements in living things

Answer 1

CHON

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

Question 2

5 Other elements needed by living things

Answer 2

(SPI Na C )

1. Sulfur
2. Calcium
3. Phosphorous
4. iron
5. Sodium

Question 3

State the role of Sulfur

Answer 3

Essential element in variable group of some amino acids (therefore proteins).

Question 4

State the role of Calcium

Answer 4

Essential element in bones, teeth, shells, nerve function

Question 5

State the role of Phosphorous

Answer 5

Essential element in nucleotides, including ATP

Question 6

State the role of Iron

Answer 6

Essential in heme group of hemoglobin, oxygen transport molecule.

Question 7

State the role of Sodium

Answer 7

Essential ion in neutron membrane potential, required for nerve impulse transmission.

Question 8

Outline the 5 thermal properties of water

Answer 8

1. Hydrogen bonds between polar water molecules cause water to resist change.
2. High specific heat (energy to change water temperature).
3. High heat of vaporization (energy to boil water).
4. High heat of fusion (Loss of energy to freeze water).
5. Water produces stable environment for aquatic organisms.

Question 9

Outline the 4 cohesive properties of Water

Answer 9

1. Hydrogen bonds between polar water molecules cause them to cohere.
2. Allowing for transpiration in plants moving water against gravity.
3. Surface tension between cohering water molecules.
4. Allowing for animals such as water striders to walk over the surface of ponds even though they are denser than water.

Question 10

Outline the 2 solvent properties of Water

Answer 10

1. The polarity of water attracts or dissolves, any other polar or charged particles by forming hydrogen bonds with them.
2. Proteins, glucose or ions such as sodium or calcium are all soluble.

Question 11

Relationship between 3 coolant properties and its use in living organisms.

Answer 11

1. Hydrogen bonds between polar water molecules cause water to resist change.
2. High heat of vaporization (energy to change liquid to vapor) because hydrogen bonds must be broken.
3. Evaporation from plant leaves (transpiration) or from human skin (sweat) removes heat and acts as a coolant.

Question 12

Relationship between 2 Medium for metabolic properties and its use in living organisms.

Answer 12

1. Cytoplasm is primarily water, providing a polar medium in which other polar or charged molecules dissolve.
2. Many enzymes are globular proteins that are water soluble so they dissolve in Cytoplasm where they control metabolic reactions.

Question 13

Relationship between 3 Transport Medium properties and its use in living organisms.

Answer 13

1. Hydrogen bonds between polar water molecules cause them to cohere.
2. As water is lost by transpiration/ evaporation from plant leaves, hydrogen bonds between adjacent water molecules pull water up columns of xylem.
3. Plants move water against gravity by much as 100 meters,