2: Lipids

Question 1

What are lipids?

Answer 1

carbon compounds made by living organisms that are mostly or entirely hydrophobic

Question 2

Name the 3 main types of lipid.

Answer 2

• triglycerides
• phospholipids
• steroids

Question 3

Describe ‘triglycerides’. Give 2 general examples.

Answer 3

• made from 3 fatty acids and 1 glycerol by condensation reactions so they have 3 hydrocarbon tales
• fats and oils

Question 4

Describe ‘phospholipids’.

Answer 4

• 2 fatty acid tails linked to glycerol, with a phosphate group instead of the third fatty acid
• phospholipids are partly hydrophobic and form the basis of membranes

Question 5

Describe ‘steroids’. Give 4 examples of steroids.

Answer 5

• all types of steroids have similar structure
• 4 fused rings in their molecule
• cholesterol, progesterone, estrogen, testosterone

Question 6

How can molecules be identified as lipids?

Answer 6

• if they have 2 or 3 hydrocarbon chains

- if they have the quadruple ring structure (steroids)

Question 7

Draw a molecular structure of a glycerol molecule. (p22)

Answer 7

-

Question 8

How are hydrocarbon chains often shown in molecular diagrams?

Answer 8

as a zigzag line (see p22)

Question 9

How are rings of carbon atoms often shown in molecular diagrams?

Answer 9

hexagons or pentagons (see p22)

Question 10

Draw the molecular structure of a triglyceride. (p22)

Answer 10

-

Question 11

Draw the molecular structure of a phospholipid. (p22)

Answer 11

-

Question 12

Draw the molecular structure of a testosterone (p22).

Answer 12

-

Question 13

How many parts to a fatty acid are there? What are they?

Answer 13

• two parts

- carboxyl group (acid) and an unbranched hydrocarbon chain (fatty)

Question 14

Draw a molecular diagram of a carboxyl group. Draw a molecular diagram of a hydrocarbon chain. (p22)

Answer 14

-

Question 15

What is the fast way of showing the molecular structure of a hydrocarbon chain?

Answer 15

• CH2 - (CH2)n - CH3

Question 16

What two factors vary in a chain of hydrocarbons?

Answer 16

• the number of carbon atoms in the hydrocarbon chain

- the bonding of the carbon atoms to each other and to hydrogens

Question 17

What does ‘saturated’ mean when talking about fatty acids?

Answer 17

all carbon atoms in the chain are connected by single covalent bonds = the number of hydrogen atoms bonded to the carbons cannot be increased

Question 18

What does ‘unsaturated’ mean when talking about fatty acids?

Answer 18

contain one or more double bonds between carbon atoms in the hydrocarbon chain = more hydrogen could be bonded to the carbons if a double bond was replaced by a single bond

Question 19

Draw an unsaturated fatty acid. (p22)

Answer 19

-

Question 20

What does ‘monounsaturated’ mean when talking about fatty acids?

Answer 20

only one double bond (between carbon atoms in hydrocarbon chain)

Question 21

What does ‘polyunsaturated’ mean when talking about fatty acids?

Answer 21

two or more double bonds (between carbon atoms in hydrocarbon chain)

Question 22

What does the position of the nearest double bond to the the CH3 terminal determine?

Answer 22

• third bond from terminal = omega-3 fatty acid

- sixth bond from terminal = omega-6 fatty acid

Question 23

What does ‘cis unsaturated’ mean when talking about fatty acids?

Answer 23

hydrogen atoms are bonded to carbon atoms on the same side of a double bond

Question 24

What does ‘trans unsaturated’ mean when talking about fatty acids?

Answer 24

hydrogen atoms are bonded to carbon atoms on opposite sides of a double bond