Lipids and glycogen COPY

Question 1

What does a triglyceride consist of and draw the diagram? (also briefly describe the bonding)

Answer 1

a molecule of glycerol with three fatty acids attached to it. each fatty acid forms an ester bond with glycerol in a condensation reaction

Question 2

As the glycerol molecule in all triglycerides are the same, where does the differences in the properties of different fats and oils come from?

Answer 2

the variations in the fatty acids

Question 3

What is a fatty acid molecule?

Answer 3

a long chain of carbon atoms with an acid group (-COOH) at one end. Hydrogen atoms are attached to the carbons.

Question 4

What does it mean if a fatty acid is saturated?

Answer 4

It means that every carbon atom in the chain is joined by a single bond

Question 5

What does it mean if a fatty acid is unsaturated?

Answer 5

It means if on or more of the bonds that every carbon atom is joined by is a double bond

Question 6

What does it mean if a fatty acid is polyunsaturated?

Answer 6

It means it has many double bonds

Question 7

Why are unsaturated and polyunsaturated lipids liquid (oils) at room temperature?

Answer 7

Because the double bonds cause the molecules to bend, hence they cannot be packed together closely

Question 8

Describe more in detail about the structure of triglycerides and how this is related to its property

Answer 8

high ratio of energy-storing carbon-hydrogen bonds to carbon atoms = excellent source of energy

low mass to energy ratio = making them good storage molecules, as much energy can be stored in a small volume. Benefits animals as it reduces mass they have to carry

large, non-polar molecules = insoluble in water = their storage does not affect osmosis in cells or the water potential of them

high ratio of hydrogen to oxygen atoms -= release water when oxidized = provide an important source of water = useful to organisms living in dry deserts.

Question 9

What are phospholipids, describe the components and draw the diagram?

Answer 9

a class of lipids that has two fatty acid chains and a phosphate group. hydrophilic head (phosphate), which interacts with water but not fat.

Hydrophobic fatty acid tails

Question 10

How do phospholipids position themselves when they are placed in water?

Answer 10

hydrophillic heads are as close to the water as possible

hydrophobic tails are as far away from the water as possible

Question 11

What are cell membranes made out of?

Answer 11

a double layer of phospholipids

Question 12

How do phospholipids affect the properties of the cell membrane?

Answer 12

contribute to the flexibility of membranes

transfer of lipid-soluble substances across them

Question 13

What are the roles of lipids and how does it carry out its role? (4)

Answer 13

Source of energy = when oxidised, provide morethan twice the enrgy as the same mass of carbohydrate and release valuable water

waterproofing = insoluble in water. In plants & insects: waxy cuticle to conserve water. In mammals: produce oil secretion from sebaceous glands in skin

Insulation = Fats are slow conductors of het and when stored beneath the body surface, they help retain body heat. Also acts as electrical insulators in the myelin sheath around the nerve cells

protection = stored around delicate organs such as the kidneys

Question 14

How is the structure of phospholipids related to their properties

Answer 14

polar molecules due to the hydrophobic and hydrophilic components = in an aqueous environment phospholipid molecules form a bilayer within the cell-surface membrane = hydrophobic barrier is formed between the inside and outside of a cell

hydrophilic phosphate heads of phospholipid molecules help to hold at the surface of the cell-surface membrane

phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane. glycolipids important in cell recognition

Question 15

Draw a triglyceride (chemical formula version)

Answer 15

Question 16

Draw a glycerol (chemical formula version)

Answer 16

Question 17

How do you carry out an emulsion test?

Answer 17

Take a completely dry and grease-free test tube

to 2cm^3 of the sample being tested, add 5cm3 of ethanol

30 shake the tube thoroughly to dissolve any lipid in the sample

Add 5m3 of water and shake gently

a cloudy-white colour indicates the presence of a lipid

as a control, repeat the procedures using water instead of the sample; the final solution should remain clear

Question 18

Why is there a cloudy colour if there is lipids in the sample?

Answer 18

because any lipid in the sample is being finely dispersed in the water to form an emulsion. Light passing through this emulsion is refracted as it passes from oil droplets to water droplets, making it appear cloudy

Question 19

Describe the colorimeter practical

(include the science behind the benedict solution)

Answer 19

benedict solution contain cu2+ ions. reducing sugars donate an electron = cu+ ion, which forms a red precipitate. The red precipitate + the blue solution leads to the colour change that we see

1. leave the test tube with the benedict soluton and reducing sugar solution, so that the red precipitate settles at the bottom. This will allow us to see only the benedict solution (which will be less blue due to some of the Cu 2+ reacting= no longer in the solution)

the less blue the solution = higher glucose conc. because more Cu2+ have reacted

2. filter the red precipitate, leaving just the benedict solution
3. When using a colorimeter, use a red filter in front of the light source, so only red light is produced. this is because the benedict solution absorbs red light the most since blue is on the opposite spectrum to red light
4. we can find the glucose concentration of an unknown solution, by comparing the colorimeter results of known solutions and using a calibration curve to estimate.

Question 20

Draw a triglyceride

Answer 20