L6 Sugars and Lipids

Question 1

What is a carbohydrate?

Answer 1

• A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H), and oxygen (O) atoms, usually with a hydrogen-oxygen ratio of 2:1
• The typical structure of a carbohydrate is a multiple of CH2O, e.g. C3H6O3

Question 2

What is sugar?

Answer 2

Sugar is a type of carbohydrate

Question 3

What are the 3 functions of sugar?

Answer 3

What are the 3 functions of sugar?

Question 4

What are the 3 categories for carbohydrates?

Answer 4

• monosaccharides
• disaccharides
• polysaccharides

Question 5

What are monosaccharides?

Answer 5

Monosaccharides are simple sugar molecules containing 3 to 7 carbon atoms

Question 6

What is an example of a monosaccharide?

Answer 6

Glucose

Question 7

What are disaccharides?

Answer 7

Disaccharides are 2 monosaccharides linked together

Question 8

What is an example of a disaccharide?

Answer 8

Table sugar
→ it is made of fructose and glucose

Question 9

What are polysacchirides?

Answer 9

Polysaccharides are 3 or more monosaccharides linked together (more like 100-1000 monosaccharides)

Question 10

What are some examples of polysaccharides? (3)

Answer 10

• cellulose
• chitin
• starch

Question 11

Which two functional groups are always found in sugar?

Answer 11

• one carbonyl
• several hydroxyl groups

Question 12

Give 2 examples of carbonyl groups

Answer 12

• an aldose
• a ketose

Question 13

What is the relationship between an aldose and a ketose

Answer 13

They are isomers

Question 14

What are isomers?

Answer 14

Isomers are molecules with an identical molecular - that is the same number of atoms of each element - but distinct arrangements of atoms in space

Question 15

What are optical isomers? (stereoisomers)

Answer 15

• Stereoisomers are molecules that have the same molecular formula and sequence of bonded atoms, but differ in the 3 dimensional orientation of their atoms in space
• Optical isomers are mirror images of each other

Question 16

What is an example of sugars that are optical isomers?

Answer 16

Glucose and galactose
- glucose is the sugar in fruit
- galactose is the sugar in milk

Question 17

What happens to straight-chain glucose in solution?

Answer 17

It forms another covalent bond to become the ring form of glucose.

Question 18

What are the two types of glucose rings?

Answer 18

Alpha-glucose and beta-glucose

Question 19

What is the relationship between alpha-glucose and beta-glucose

Answer 19

They are 2 isomers of glucose

Question 20

How are sugar polymers (polysaccharides) formed?

Answer 20

They are formed by covalent bonds called glycosidic linkages, between the C-1 of one sugar with any OH-group of the second sugar

Question 21

What does the alpha1,4 glycosidic linkage give rise to?

Answer 21

It gives rise to maltose, and eventually starch

Question 22

What does the beta1,4 glycosidic linkage give rise to?

Answer 22

It gives rise to cellobiose and eventually cellulose

Question 23

In starch, are the CH2OH bulky groups on the same side or on opposite sides?

Answer 23

They are on the same side
→ this bends the polymer resulting in the shape of a spiral

Question 24

In cellobiose, are the CH2OH bulky groups on the same side or on opposite sides?

Answer 24

They are on opposite sides.
→ this makes a very symmetrical straight molecule

Question 25

What are lipids?

Answer 25

Lipids can be all kinds of structures: the only thing that they have in common is that they are insoluble in water

Question 26

What are the roles of lipids? (7)

Answer 26

- energy storage (fats and oils) - cell membranes (phospholipids) - capture of light energy (carotenoids) - hormones and vitamins (steroids and modified fatty acids) - thermal insulation - electrical insulation of nerves - water repellency (waxes and oils)

Question 27

What are the most important lipids? (2)

Answer 27

Fats (solid) and oils (liquid)

Question 28

What are fats and oils composed of?

Answer 28

3 fatty acids and 1 glycerol connected by covalent bonds

Question 29

What are fatty acids composed of?

Answer 29

Fatty acids have one carboxyl group and a long hydrocarbon chain

Question 30

What property do fatty acids have?

Answer 30

They are amphiphilic

Question 31

What are unsaturated fatty acids?

Answer 31

Unsaturated fatty acids are fatty acids that contain double bonds

Question 32

What does it entail that unsaturated fatty acids have double bonds?

Answer 32

- The double bonds cause kinks in the fatty acid tails - Because of this, unsaturated fatty acids cannot be packed as closely together as straight saturated fatty acids - And this is the reason that butter is solid at room temperature (saturated) and oils are fluid at the same temperature (unsaturated)

Question 33

What are phospholipids composed of?

Answer 33

Phospholipids have a hydrophilic head and two hydrophobic fatty acid tails that are attached to glycerol

Question 34

What property do phospholipids have?

Answer 34

They are amphiphilic

Question 35

What unique capability to phospholipids have?

Answer 35

They can self assemble into lipid bilayers, with the hydrophobic fatty acid tails pointing inward away from water, and the hydrophilic head pointing outwards

Question 36

Lipid bilayers assemble into what shape?

Answer 36

Into a globular compartment (sphere)

Question 37

Why is it energetically favorable for lipid bilayers to assemble into a globular compartment?

Answer 37

Because no more hydrophobic parts are exposed to water

Question 38

Do lipid bilayers move?

Answer 38

Yes, lipid bilayers are very fluid, with phospholipids constantly in lateral motion

Question 39

What is the effect of unsaturated fatty acids in lipid bilayers on the fluidity and permeability of the membrane?

Answer 39

Unsaturated fatty acids in lipid bilayers increase the fluidity and permeability of the membrane

Question 40

How do fish and plants use double bonds in phospholipids to keep membrane fluidity stable over a wide variety of temperatures?

Answer 40

They adjust the amount of double bonds that they have to do so. (Increase the number of double bonds to become more permeable and more fluid).