Chemistry of life - Lesson 1

Question 1

State the definition of ionic bonding

Answer 1

When 2 or more atoms donate electrons to each other, forming strong ionic bonds, which are forces of attraction that hold the oppositely charged ions together

Question 2

State the definition of covalent bonding

Answer 2

When 2 or more atoms share electrons, forming strong covalent bonds.

Question 3

how does covalent bonding form polar molecules

Answer 3

when the electrons in the covalent bonds are not evenly shared, forming a dipole.

Question 4

what happens to ionic substances when they are in water

Answer 4

they dissolve, as the ions attract the dipoles in the water molecules, forming hydrogen bonds

Question 5

what is the function of nitrate ions (NO3-)

Answer 5

needed in plants for the formation of amino acids and DNA

Question 6

what is the function of phosphate ions (PO4-3)

Answer 6

needed in plants and animals for the formation of ATP, ADP, DNA and RNA

Question 7

what is the function of chloride ions (Cl-)

Answer 7

needed in nerve impulses and many secretory systels

Question 8

what is the function of hydrogen carbonate ions (HCO3-)

Answer 8

needed for buffering the blood to prevent it from becoming too acidic

Question 9

what is the function of sodium ions (Na+)

Answer 9

needed in nerve impulses and many secretory systems

Question 10

what is the function of calcium ions (Ca+2)

Answer 10

needed for the formation of calcium pectate for the middle lamella, for for bone formation and muscle contraction in animals

Question 11

what is the function of hydrogen ions (H+)

Answer 11

needed in cellular respiration and photosynthesis, and to balance the pH

Question 12

what is the function of magnesium ions (Mg+2)

Answer 12

needed for production of chlorophyll in plants

Question 13

why does water have a high melting point

Answer 13

because it takes a lot of energy to overcome the attractive forces of all the hydrogen bonds

Question 14

what are hydrogen bonds

Answer 14

weak electrostatic intermolecular bonds formed between polar molecules and hydrogen atoms

Question 15

what are 8 characteristics of water

Answer 15

• a polar solvent
• a transport medium
• maximum density at 4°C
• high specific heat capacity
• cannot be compressed
• cohesive
• adhesive
• high surface tension

Question 16

why is it important that water is a polar solvent

Answer 16

because many ionic substances and polar molecules dissolve in water. So, many chemical reactions in cells occur in water

Question 17

why is water an excellent transport medium

Answer 17

because many substances dissolve in water, water can transport molecules easily

Question 18

why is it important that water has a maximum density at 4°C

Answer 18

as a result, ice is less dense than water and floats, forming an insulated layer and helps to prevent water underneath it from freezing. This means organisms can live under the ice

Question 19

why is it important that water has a high specific heat capacity

Answer 19

because it takes a lot of energy to break the hydrogen bonds, the temperature doesn’t change that much, making large bodies of water good habitats

Question 20

why is it important that water cannot be compressed

Answer 20

makes it important for hydraulic mechanisms in organisms

Question 21

why is it important that water is cohesive

Answer 21

the forces cause water molecules to stick together. This is important for water movement from roots to leaves in plants

Question 22

why is it important that water is adhesive

Answer 22

they are attracted to other molecules, which is important in plant transport and in surface tension

Question 23

why is it important that water has a high surface tension

Answer 23

because the attraction between the water molecules (hydrogen bonds) is greater than the attraction between water molecules and air, water molecules form a thin skin of surface tension. This is important for plant transport systems