Main topic 1: Biological molecules (lipids)

Question 1

What are the two groups of lipids?

Answer 1

triglycerides, and phospholipids.

Question 2

how is a triglyceride formed?

Answer 2

by the condensation of one molecule of glycerol, and three molecules of fatty acids.

Question 3

what is an ester bond?

Answer 3

A condensation reaction between one molecule of glycerol and three fatty acids (RCOOH) forms an ester bond.

Question 4

why can we call fatty acids RCOOH?

Answer 4

well, the R stands for the hydrocarbon chain, and the COOH, stands for the carboxyl group.

Question 5

What are the two types of hydrocarbons?

Answer 5

Saturated and unsaturated.

Question 6

what is an saturated fatty acid?

Answer 6

A hydrocarbon that contains NO double carbon bonds, and each carbon contains the maximum ammounts of hydrogen possible.

Question 7

What is an unsaturated fatty acid?

Answer 7

It is a hydrocarbon that contains one or more double carbon bonds. Each carbon involved in a double bond, has one less hydrogen.

Question 8

what is the difference between a monounsaturated fatty acid, and a polyunsaturated fatty acid?

Answer 8

Mononsaturated: Only contains one double carbon bond.
Polyunsaturated : Contains more that one double carbon bonds.

Question 9

What happens at a double carbon bond in an unsaturated fatty acid?

Answer 9

It bends.

Question 10

what is the structure of a phospholipid?

Answer 10

It has one phosphate group, one molecule of glycerol, and two fatty acids.

Question 11

which is the head, and which are the tails in a phospholipid?

Answer 11

The phosphate group is the head, and the fatty acids are the tails.

Question 12

Describe the head and tail of the phospholipid.

Answer 12

The head is polar, and therefore does mix with water, we say it is HYDROPHILIC. The tails however ( fatty acids), are non-polar, and do not mix with water, therefore, we say they are HYDROPHOBIC.

Question 13

what common structures do phospholipids form?

Answer 13

Micelle, Bilayer, and monolayer.

Question 14

what are cell membarnes formed out of?

Answer 14

Bilayers of phospholipids

Question 15

Why is it an advantage for cells to have a cell membrane out of phospholipids?

Answer 15

Unsaturated fatty acids cannot be tightly packed together, since there are many bends, so they form gaps in the celll surface membrane. As a result, the cell membrane is bendy, and has a flexible surface.It also allows small, non polar molecules to pass through, such as O2 and CO2. This is good, because now those small substances can pass through simple diffusion, and not through faciliated diffusion.

Question 16

what is another advantage for cells to have a cell membrane made out of phospholipids?

Answer 16

They can enable cell recognition. Phospholipids can combine with carbohydrates to mark a cell. We call the structure formed a glycoprotein. This is important, because if the cell has no marker, our immune system could attack it, thinking its a foreign body, and kill it.

Question 17

what are fats made out of? And relate this to its structure.

Answer 17

Fats are made out of saturated fatty acids. Saturated fatty acids, have straight, parallel hydrocarbon chains. As a result, triglycerides with saturated fatty acids, dont take up as much space, since thy can be packed tightly together, forming a solid block(fat)at room temperature.

Question 18

What are oils made out of? And relate this to its structure

Answer 18

Oils are made out of unsaturated fatty acids. this means they have alot of bends in their hydrocarbon chains. As a result, triglycerides with unsaturated fatty acids, do take up alot of space, since they cannot be tightly packed together. Therefore, they form a liquid (oil) at room temperature.

Question 19

what are the properties of fatty acids?

Answer 19

1. High ratio of hydrogen and carbon to oxygen.
2. large, because hydrocarbon is long.
3. Non - polar.

Question 20

What are the properties of triglyceriedes?

Answer 20

1.Large, because of long hydrocarbon chains.
2. Non-polar, because non polar region is so much larger than polar region.
3. Insoluble in water, because they are mostly non-polar. Because they are non-polar, they dont mix with water, so we can say that they are hydrophobic.

Question 21

Why are triglycerides a good energy source?

Answer 21

Because of the high carbon and hydrogen to oxygen ratio, and because it is large. There is simply more of what to react to form ATP during respiration.

Question 22

why are triglycerides a good water source?

Answer 22

This is because of the high carbon and hydrogen to oxygen ratio, There is simply more of what to react to form water during respiration.

Question 23

Why are triglycerides good storage molecules?

Answer 23

1.Because they have a low mass : Energy ratio, meaning that we can store alot of energy in a small ammount of mass.
2.. Because they are large, and cannot escape cell membrane while being stored.
3.they are insoluble, therefore they dont dissolve in the cytoplasm of the cell, and affect the water potential, which could lead to unwanted water gain by osmosis.

Question 24

How would you carry out a test for lipids?

Answer 24

We would use the emulsion test.
steps:
1. Add 2cm3 of food sample, to test tube.
2. Add 5cm3 of alcohol to the same test tube, and shake test tube.( Lipids are soluble in alcohol, this will cause them to free from the other parts of the food sample)
3. Add to 5cm3 of water, and shake gently.
4. If positive, will turn milky white colour from colourless.

Question 25

How do we convert between millimetres, micrometres, and nanometres?