lipid

Question 1

Describe the difference between the structure of a triglyceride molecule and the structure of a phospholipid molecule

Answer 1

In phospholipid, one fatty acid replaced by a phosphate;

I

Question 2

This fat substitute cannot be digested in the gut by lipase.

Suggest why.

instead of glycerol it has 3 propylene glycerol’s

Answer 2

(Fat substitute) is a different/wrong shape/not complementary;

OR

Bond between glycerol/fatty acid and propylene glycol different
(to that between glycerol and fatty acid)/no ester bond;

2. Unable to fit/bind to (active site of) lipase/no ES complex formed;

Question 3

This fat substitute is a lipid. Despite being a lipid, it cannot cross the cell-surface membranes of cells lining the gut.

Suggest why it cannot cross cell-surface membranes.

Answer 3

It is hydrophilic/is polar/is too large/is too big;

Question 4

Use the information in the figure to explain two ways in which fatty acids are important in the formation of new cells.

Answer 4

Fatty acids used to make phospholipids;
Phospholipids in membranes;
More phospholipids more membranes made;

2 max

Fatty acids respired to release energy;
More triglycerides more energy released;
Energy used for cell production / production of named cell component

Question 5

Describe how a saturated fatty acid differs in molecular structure from an unsaturated fatty acid.

Answer 5

absence of a double bond;

in the (hydrocarbon) chain;

unable to accept more hydrogen / saturated with hydrogen;

Question 6

There is a difference between the concentration of omega-3 fatty acids in the wild trout and trout farmed in cages. Suggest two causes of this difference

Answer 6

The different diet of the fish;
Omega-3 fatty acids used in respiration / as a source of energy;
Wild trout are more active / use more energy;

Question 7

Draw a diagram to show the structure of a triglyceride molecule.

Answer 7

LEARN THIS

Question 8

Explain why triglycerides are not considered to be polymers.

Answer 8

Not made by repeating units

Question 9

Using evidence from Figure 2 to support your answer, suggest how the function of brown fat cells differs from that of white fat cells.

LOOk on lipids 7

Answer 9

many) mitochondria present in brown fat cells;
mitochondria release heat / energy; (ignore ATP)
white fat cells for fat storage / reduced fat storage in brown fat cells;

Question 10

do q 9 5 times

Question 11

PHOSPHOLIPIDS STILL CONTAIN GLYCEROL

Question 12

The scientists expressed their results as Percentage of lipid in plasma membrane by mass. Explain how they would find these values.

Answer 12

Divide mass of each lipid by total mass of all lipids (in that type of cell);

2. Multiply answer by 100.

Question 13

Cholesterol increases the stability of plasma membranes. Cholesterol does this by making membranes less flexible.

(f) Suggest one advantage of the different percentage of cholesterol in red blood cells(23) compared with cells lining the ileum.(17)

Answer 13

Red blood cells free in blood / not supported by other cells so cholesterol helps to maintain shape;

Allow converse for cell from ileum – cell supported by others in endothelium so cholesterol has less effect on maintaining shape.

Question 14

Describe how an ester bond is formed in a phospholipid molecule.

Answer 14

Condensation (reaction)

OR

Loss of water;

2. Between of glycerol and fatty acid;

Question 15

Describe how an ester bond is formed in a phospholipid molecule

Answer 15

Condensation (reaction)

OR

Loss of water;

2. Between of glycerol and fatty acid;