5. Lipids, cell membranes & transport across cell membranes

Question 1

Are triglycerides hydrophobic or hydrophilic?

Answer 1

Hydrophobic

Question 2

Are triglycerides soluble or insoluble in alcohol?

Answer 2

soluble

Question 3

Which molecules have a structural formula containing C=O bonds? 2

Answer 3

Fatty acids and glucose

Question 4

Describe the oxygen:carbon ratio in triglycerides compared to carbs

Answer 4

Triglycerides have a lower ratio of oxygen to carbon

Question 5

Name 4 features of triglycerides

Answer 5

Non-polar,
less dense than water,
higher energy value than carbs,
higher proportion of hydrogen than carbs

Question 6

When hydrolysed, which molecules have products containing a carboxyl group? 2

Answer 6

phospholipids and proteins

Question 7

What is used to test for the presence of sugars?

Answer 7

Benedict’s reagent

Question 8

What is the sign of a positive test for sugars

Answer 8

Benedict’s reagent goes from blue to brick red

Question 9

What is used to test for starch?

Answer 9

iodine solution

Question 10

What is a sign of a positive test for starch

Answer 10

solution goes from orange/brown to blue/black

Question 11

What is used to test for proteins

Answer 11

biuret solution

Question 12

What are the signs of a positive test for proteins?

Answer 12

Goes from light blue to purple/lilac

Question 13

What is used to test for lipids?

Answer 13

ethanol

Question 14

What is the sign of a positive test for lipids?

Answer 14

Solution turns cloudy

Question 15

q6 which molecule is a protein?

Answer 15

Z

Question 16

q6 which molecule is a lipid?

Answer 16

W

Question 17

q6 which molecule is a non- reducing sugar molecule?

Answer 17

Y

Question 18

The enzyme lactase is formed by a single polypeptide that folds to give 3 regions: an active site with the free amino group outside the cell, a short section inside the membrane, a short section inside the cell. Which sections are hydrophobic or hydrophilic?

Answer 18

Outside cell: hydrophilic

Inside membrane: hydrophobic

Inside cell: hydrophilic

Question 19

q8 what is 1

Answer 19

phospholipids

Question 20

q8 name 2

Answer 20

protein

Question 21

q8 name 3

Answer 21

glycoprotein

Question 22

q8 name 4

Answer 22

Channel protein

Question 23

q8 name 5

Answer 23

cholesterol

Question 24

q8 which molecules have hydrophobic and hydrophilic regions?

Answer 24

phospholipids, proteins, channel proteins and cholesterol

Question 25

Increasing which type of bond helps increase the fluidity of the cell surface membrane?

Answer 25

C=C (carbon-carbon)

Question 26

q10 which would enable a hormone to recognise its target cell?

Answer 26

B, transmembrane protein

Question 27

Which two components contribute to the fluidity of the cell membrane?

Answer 27

Cholesterol & phospholipid fatty acid chains

Question 28

How does cholesterol affect cell fluidity?

Answer 28

It provides stability and reduces fluidity by fitting between phospholipids

Question 29

How do phospholipid tails affect fluidity?

Answer 29

Longer fatty acid tails mean less fluidity and more unsaturated fatty acids means less impacted by temperature

Question 30

What is the width of the cell surface membrane?

Answer 30

5-10nm