Chapter 2.2 and 2.4: Properties of Water and Lipids

Question 1

Identify 4 characteristics of all Lipids

Answer 1

• Composed of carbon, hydrogen, and oxygen
• Rich in hydrogen-oxygen bonds; low ratio of carbon-hydrogen-oxygen bonds compared to carbohydrates
• Insoluble in water
• Soluble in organic solvents like alcohol

Question 2

State 3 functions of lipids

Answer 2

• Long-term energy storage
• Insulation
• Main component to fabricate cell membranes

Question 3

Identify the 2 kinds of lipids

Answer 3

1. Phospholipids

2. Triglycerides

Question 4

Give the structure of Triglyceride and state its function.

Answer 4

• STRUCTURE: Composed of 3 fatty acids + Glycerol

- FUNCTION: Main energy storage of plants and animals

Question 5

Triglycerides are hydro_____ while phospholipids are hydro______.

Answer 5

1. hydrophobic

2. hydrophilic

Question 6

Give 4 characteristics of triglycerides and relate it to its function

Answer 6

1. High ratio of carbon-hydrogen atoms - excellent source of energy storage (compared to carbohydrates)
2. Low mass to volume ratio - ideal for storage as more mass can be stored in small volume
3. Insoluble - do not affect water potential of cells
4. High ratio of hydrogen-water atoms - release water when they are oxidized, and are an important source of water, especially beneficial to desert organisms

Question 7

Give the structure of Phospholipids and state its function.

Answer 7

• STRUCTURE: Composed of glycerol, 2 fatty acid tails and a phosphate head
• FUNCTION: Primary component of cell membranes that control what enters and exits the cell

Question 8

Phospholipids have a hydrophilic head and hydrophobic tail, therefore it is a _____ molecule while triglycerides is a _______ molecule

Answer 8

• Polar

- Non-polar

Question 9

Bond present between lipids

Answer 9

Ester bond

Question 10

Test for lipids is _____. State the results of the test for if lipids are present or not.

Answer 10

Emulsion Test (uses ethanol; polar solvent)

PRESENT: Cloudy-white
NOT PRESENT: 2 distinct layers // clear

Question 11

Differentiate between saturated and unsaturated fats.

Answer 11

• Saturated has no double bonds while unsaturated does
• Saturated: Animal Fats versus Unsaturated: Plant oils
• Saturated: Liquid versus Unsaturated: Solid
• Saturated: Straight chain versus Unsaturated: Chain has kinks

Question 12

Define Hydrogen Bonding

Answer 12

The attractive force between an electronegative atom of one molecule and the hydrogen atom of another molecule.

Question 13

State the 4 properties of water and explain each.

Answer 13

1. Cohesive & Adhesive behaviour: water is attracted to other water molecules at the same time it can be attracted to different molecules//surfaces (transpiration).
2. Ability to moderate temperature: water has a high specific heat capacity and latent heat of vaporisation (sweating).
3. Versatility as a Solvent: water can dissolve most compounds and ions “Like dissolves like” (circulatory system)
4. Expansion upon freezing: Ice is less dense than water because of the hydrogen bonding present in water