Lipids

Question 1

What are lipids?

Answer 1

A group pf substances that are soluble in alcohol rather than water. They include triglycerides, phospholipids, glycolipids and cholesterol

Question 2

What are phospholipids?

Answer 2

Molecule consisting of glycerol, 2 fatty acids, and 1 phosphate group

Question 3

what is a property of lipids?

Answer 3

They are insoluble in water because they are non-polar and therefore they are not attracted to the water

Question 4

What are the three most important lipids?

Answer 4

Triglycerides
Phospholipids
Steriods

None of them are polymers. they are different compounds bonded together. They are example of Macromolecules

Question 5

Describe the structure of triglyceride

Answer 5

Glycerol and fatty acids.
Glycerol: 3 carbon atoms. It’s an alcohol, therefore, contains free -OH groups. There are 3 -OH groups in triglycerides
Fatty acid: many types. Those we cannot make and most be ingested are called “essential fatty acids”

Question 6

Describe the fatty acids in triglycerides

Answer 6

Carboxyl group (-cooh) on one end, attached to a hydrocarbon tail, made of only carbon and hydrogen atoms
2-20 carbons long
Carboxyl group ionises into H+ and a -COO- group. Therefore it is an acid because it produces free H+ ions

Question 7

Give inofrmation about saturated and unsaturated fatty acids

Answer 7

If saturated there are no double-double carbon bonds (C=C)
If unsaturated there is a double-double carbon bond, which means that fewer H-atoms can ee bonded to the molecule
Single C=C bond — monounsaturated fatty acid
More than 1 C=C bond — polyunsaturated fatty acid
unsaturated fatty acid have a different shape because where the C+C bond is the chain kinks changing the hydrocarbon chain
Kink pushes molecules apart = more fluid
More unsaturated fatty acid = lower melting point
Animal lipids = solid at room temperature (20o) - saturated

Question 8

What bond forms in lipids?

Answer 8

The covalent bond is called ester bonds

Question 9

Talk about the formation of ester bonds

Answer 9

Condensation reaction happens between the -COOH group pf the fatty acid and the -OH group of the glycerol
Covalent bond formed= ester bond

Question 10

What are the functions of triglycerides?

Answer 10

Energy source: they can be broken down in respiration to release energy and generate ATP.
Energy store: Because they are insoluble in water they can be stored without affecting the water potential in the cells.
Insulation: Adipose tissue is a storage location for lipids in whales, acting as a heat insulator. Lipids in nerve cells act as an electrical insulator. Animals preparing for hibernation store extra fat.
Buoyancy: Because fat is less dense than water, it is used by aquatic mammals to help them stay afloat
Protection: Humans have fat around delicate organs, such as their kidneys, to act as a shock absorber. The peptidoglycan cell wall of bacteria is covered in a lipid-rich outer coat.

Question 11

What is the first step to break down triglycerides in respiration to release energy and generate ATP.

Answer 11

The first step is to hydrolyse the ester bond, and then both glycerol and the fatty acids can be broken down completely to carbon dioxide and water. Respiration of a lipid produces more water than respiration of a sugar.

Question 12

What is the structure of phospholipids?

Answer 12

1 glycerol molecule
2 fatty acid groups
1 phosphate group

Question 13

What occurs in a condensation reaction between two phospholipids?

Answer 13

A condensation reaction between an -OH group on a phosphoric acid molecule(H3PO4) and one of the 3 -OH group of the glycerol forms an ester bond. Water is removed, leaving a linkage of an oxygen atom

Question 14

what is the behaviour of phospholipids in water?

Answer 14

When surrounded by water, phosphate group = negative therefore it is polar (attracted to water)
Fatty acid tail = non-polar therefore repels water
Phosphate group - hydrophobic (head)
Fatty acid - hydrophobic (tail phospholipids molecules are amphipathic

Question 15

What does the phosphate group look like?

Answer 15

Has oxygen, phosphorus (P) and hydrogen

Question 16

What does the fatty acid look like in phospholipids?

Answer 16

Chain with a double oxygen bond to a carbon with 2 hydrogen bonds.
Often even numbers of carbon atoms
Often 1 chain is saturated and the other is non-saturated

Question 17

Give information about phospholipids which are amphipathic:

Answer 17

Form a layer on the surface of the water - heads in water, tails sticking out
May also form micelles - tiny balls with tails tucked inside and the heads out

Question 18

What is the phospholipid bilayer?

Answer 18

2 rows of phospholipid: tail inwards. head outwards
Individual phospholipids are free to move around in their layer, but will not move into a position where the hydrophobic tail is touching the water. This gives the membrane some stability.
The membrane is selectively permeable - only small and non-polar molecules can move through the tail in the bilayer (e.g. Oxygen, CO2)
Controls what goes in and out of the cell and keeps it functioning properly

Question 19

Give information about cholesterol

Answer 19

Its a steroid alcohol - a type of lipid not made up of glycerol or fatty acid
Has 4 carbon-bond rings
Small and hydrophobic molecules - it can sit in the middle of the hydrophobic part of the bilayer
Regulates fluidity of the membrane - not to fluid or stiff

Many are made in the liver of animals
Plants also have a cholesterol derivative in their membrane called stigmasterol - different because it has a double bond between C-22 and C-23

Question 20

Give examples of steroid hormones

Answer 20

Testosterone
Oestrogen
Vitamin D

All made of cholesterol