Unit 2 - Lipids

Question 1

What are the 3 types of lipids?

Answer 1

• Triglycerides
• Phospholipids
• Sterols

Question 2

What are the 5 functions of triglycerides?

Answer 2

• Major source of energy
• Source of metabolic water
• Makes up adipose tissue
• provides thermal insulation under skin of animals
• Provides protection around internal organs

Question 3

How do triglycerides compare to carbohydrates in terms of energy?

Answer 3

-Per g triglycerides release more energy

Question 4

Being a source of metabolic water makes them useful for organisms in what kind of environment?

Answer 4

Desert

Question 5

Give an example of an animal that uses triglycerides as thermal insulation

Answer 5

Killer whale in the form of blubber

Question 6

When are triglycerides stored as adipose tissue?

Answer 6

When energy input is greater than energy output

Question 7

Why is cholesterol transported as a lipoprotein?

Answer 7

They allow lipids and cholesterol to dissolve in the blood

Question 8

What are the functions of sterols (2 functions)?

Answer 8

-Cholesterol used in cell membranes to give stability and regulate fluidity -Used to make steroid hormones

Question 9

Give 2 examples of steroid hormones

Answer 9

Testosterone and oestrogen

Question 10

Where is cholesterol manufactured?

Answer 10

The liver and intestines

Question 11

What is the function of HDL?

Answer 11

-used to make cell membranes and organelle membranes -decreases membrane fluidity

Question 12

Which is ‘good’ cholesterol; HDL or LDL?

Answer 12

HDL

Question 13

What does too much LDL lead to?

Answer 13

-atherosclerosis (deposits in artery walls) -gall stones

Question 14

How are triglycerides formed?

Answer 14

A condensation reaction between a glycerol molecule and 3 fatty acids

Question 15

What kind of bonds are formed when a triglyceride is formed?

Answer 15

Ester bonds

Question 16

Which part of a glycerol molecule takes part in the condensation reaction to form a triglyceride?

Answer 16

The hydroxyl groups

Question 17

What is the structure of a glycerol molecule?

Answer 17

Question 18

How many molecules of water are formed from the condensation reaction to form a triglyceride?

Answer 18

3

Question 19

What does a hydrolysis reaction of a triglyceride produce?

Answer 19

A glycerol molecule and 3 fatty acids

Question 20

i) How are phospholipids formed? ii) What kind of bonds are formed?

Answer 20

i) A condensation reaction between a glycerol molecule, 2 fatty acids, and a phosphate group ii) Ester bonds

Question 21

What property does the head of a phospholipid have?

Answer 21

It is hydrophillic and polar

Question 22

What property does the tail for a phosphlipid have?

Answer 22

It is hydrophobic and non-polar

Question 23

Explain the differences between phospholipids and triglycerides

Answer 23

-Triglycerides contain 3 fatty acids but phospholipids only contain two and a phosphate group - Triglycerides contain 3 ester bonds but phospholipids only contain 2 - Phospholipids have a hydrophilic head

Question 24

Draw a simplified version of a phospholipid

Answer 24

Question 25

Draw a phospholipid bilayer

Answer 25

Question 26

Explain why membranes exist as bilayers

Answer 26

-Both the inside and outside of cells are aqueous -therefore a single layer would repel on one side -Bilayers mean that hydrophilic heads can face into the tissue fluid and cytoplasm -with the hydrophobic tails facing away from the aqueous environments

Question 27

How does cholesterol sit in phospholipid bilayers?

Answer 27

With the hydroxyl group in contact with the Phosphate head

Question 28

What are sterols made up of?

Answer 28

Large alcohol molecules

Question 29

As cholesterol increases membrane fluidity ____

Answer 29

Decreases

Question 30

A decrease in cholesterol ____ fluidity

Answer 30

Increases

Question 31

How can you test for the presence of lipids?

Answer 31

Add ethanol first and then the resulting mixture add to water and shake

Question 32

State two roles of cholesterol in living organisms

Answer 32

1) Increases stability of phospholipds in cell membrane 2) Waterproofing to skin

Question 33

Name two molecules that combine with cholesterol to form LDLs

Answer 33

1) Saturated fatty acids 2) Triglycerides/lipids