Lipids

Question 1

What is the molecular structure of glycerol

Answer 1

DRAW IT

Question 2

What is the molecular structure of a saturated fatty acid with 5 carbons

Answer 2

DRAW IT

Question 3

What is a feature of saturated fatty acids

Answer 3

They have only have single covalent bonds between carbons

Question 4

What is the structure of a mono-unsaturated fatty acid with 5 carbons in its chain

Answer 4

DRAW IT

Question 5

What is a feature of a mono-unsaturated fatty acid

Answer 5

It only has one double covalent bond in its chain

Question 6

What is the structure of a poly unsaturated fatty acid with two double covalent bonds and 5 carbons in its chain

Answer 6

DRAW IT

Question 7

What is a feature of a poly unsaturated fatty acid

Answer 7

It has more than one double covalent bond between carbon atoms

Question 8

What do the double covalent bonds in poly unsaturated fatty acids mean

Answer 8

The double covalent bonds are rigid and cause the molecule to bend ( a kink in the chain).

Question 9

As a result of these double covalent bonds in poly unsaturated fatty acids what does this mean

Answer 9

They can;t pack together as closely making poly unsaturated fatty acids liquid at room temperature.

Question 10

What are lipids

Answer 10

Molecules containing carbon, hydrogen and oxygen and they are macromolecules that aren’t build from monomers.

Question 11

What is a property of lipids

Answer 11

They are non-polar molecules as the electrons in the outer shell are evenly distributed creating no partially positive or negative zones.

Question 12

What are triglycerides

Answer 12

Contain a molecule of glycerol bonded to 3 fatty acid molecules

Question 13

How does the bonding in a triglyceride occur

Answer 13

A glycerol molecule has 3 hydroxyl groups that can react with the hydroxyl group in the carboxylic part of a fatty acid forming an ester bond. This process is called esterification. A molecule of water is also made, so it’s a condensation reaction. Two more fatty acids then react with two more fatty acids producing a triglyceride.

Question 14

What happens during digestion of triglycerides

Answer 14

Lipase enzymes break down triglycerides releasing the glycerol and fatty acid molecules. this reaction requires 3 water molecules and is a hydrolysis reaction.

Question 15

What are features of triglycerides

Answer 15

They are non polar molecules so are hydrophobic and don’t dissolve in water. Because triglycerides contain lots of carbon and hydrogen lots of energy can be released from them.

Question 16

What are phospholipids

Answer 16

They are comprised of glycerol, two fatty acids and a molecule with a phosphate group

Question 17

What are the bonds between glycerol and the fatty acids as well as the phosphate group

Answer 17

They are all ester bonds

Question 18

In a phospholipid what is the hydrophilic and hydrophobic part

Answer 18

The tail (fatty acids) are hydrophobic repelling water.
The head (phosphate group) is hydrophilic and attracts water as it’s charged.

Question 19

What happens when phospholipids are put in water

Answer 19

the molecules position themselves so that the hydrophilic head groups interact with water molecules while the hydrophobic tails cluster away from the water molecules. So a phospholipid layer is formed.

Question 20

What do the properties of phospholipids allow

Answer 20

It allows for phospholipids to form membranes

Question 21

What are sterols

Answer 21

They are steroid alcohols
They are complex with a 4 ring structure and an OH at one end
The OH is polar (hydrophilic), the rest is non polar (hydrophobic)

Question 22

What is cholesterol

Answer 22

Cholesterol is a sterol so has a hydrophilic OH group and the rest of the molecule is hydrophobic.

Question 23

What do the hydrophilic and phobic properties allow cholesterol to do

Answer 23

It allows cholesterol to insert themselves into cell membranes as the OH group interacts with the head of phospholipids and the rest with the tails

Question 24

Where is cholesterol most commonly made

Answer 24

It’s most commonly made in the liver and also intestines

Question 25

What is the purpose of cholesterol (1)

Answer 25

It’s a common part of membranes, regulating fluidity and is positioned between phospholipids - keeps membranes fluid at low temperatures, and stops them for becoming too fluid at high temperatures

Question 26

What is the purpose of cholesterol (2)

Answer 26

It makes up vitamin D, which is produced by the skin in response to U.V light and strengthens bones

Question 27

What is the purpose of cholesterol (3)

Answer 27

It makes up steroid hormones (e.g oestrogen and testosterone)

Question 28

What is the purpose of cholesterol (4)

Answer 28

It makes up bile which increases the rate of digestion of lipids by lipase.

Question 29

What are the roles of lipids (1)

Answer 29

Membrane formation and creation of hydrophobic barriers
Hormone production
Electrical insulation necessary for impulse transmission
Water proofing for example bird feathers

Question 30

What are the roles of lipids (2)

Answer 30

Thermal insulation to reduce heat loss
Cushioning to protect vital organs such as the heart and kidneys
Buoyancy for aquatic animals such as whales
They also have an important role in long term energy storage.

Question 31

What is the test for lipids

Answer 31

The emulsion test

Question 32

What are the steps for the emulsion test

Answer 32

First the sample is mixed with ethanol, the resulting solution is then mixed with water and shaken. if a white emulsion forms a layer on top then a lipid is present.