Lecture 6: Carbohydrates and Lipids

Question 1

Three categories of carbohydrates

Answer 1

1. Monosaccharides: single sugar molecules
2. Disaccharides: two sugar molecules linked covalently
3. Polysaccharides: Multiple sugar molecules linked together covalently

Question 2

How are carbons, oxygens and hydrogens related in carbohydrates?

Answer 2

There are always the same number of carbons as oxygens and always double the amount of hydrogens

Question 3

Difference between sugars and alcohols?

Answer 3

Sugars either have an aldehyde at the end of the molecule or a ketone in the middle of the molecule.

Question 4

What is an isomer?

Answer 4

Molecule with the same molecular formula but different structure

Question 5

Do isomers have the same chemical properties?

Answer 5

Yes

Question 6

What is an optical isomer?

Answer 6

When four different atoms are attached to a central carbon atom in two different ways, these are called optical isomers

Question 7

What is a glycosidic linkage?

Answer 7

Bond between a carbohydrate and another molecule(can be another carbohydrate)

Question 8

Why are alpha-glucose and beta-glucose the only two disaccharides that matter?

Answer 8

Those are the only two that enzymes evolved to catalyze

Question 9

What is starch?

Answer 9

Starch is a polysaccharide made from alpha(1-4 linkages) between alpha glucose molecules

Question 10

What is starch in plants?

Answer 10

Amylose

Question 11

Is starch branched or unbranched?

Answer 11

Unbranched(just a long chain)

Question 12

What is amylopectin?

Answer 12

Moderately branched starch found in plants

Question 13

What is glycogen?

Answer 13

Moderately branched starch found in animals

Question 14

Is starch hard to breakdown?

Answer 14

NO

Question 15

How is cellobiose made?

Answer 15

Two beta-glucose molecules from a beta 1-4 link to create cellobiose

Question 16

Cellobiose vs Cellulose

Answer 16

Cellobiose: disaccharide
Cellulose: polysaccharide

Question 17

Is cellulose branched or unbranched?

Answer 17

UNBRANCHED

Question 18

Characteristics of cellulose?

Answer 18

-Very linear
-Very symmetrical
-Branched
-Hard to breakdown

Question 19

What happens when you line up multiple cellulose strands next to each other?

Answer 19

Hydrogen bonds form between the strands, resulting in a very stable structure that can be hard to breakdown

Question 20

What is the role of oligosaccharides?

Answer 20

They determine blood groups in our body
-They attach to proteins

Question 21

Roles of lipids(7)

Answer 21

1. Energy storage
2. Cell membranes
3. Capture of light and energy(carotenoids)
4. Hormones and vitamins
5. Thermal Insulation
6. Electrical Insulation of nerves
7. Water repellency(waxes and oils)

Question 22

Characteristics of lipid?

Answer 22

-insoluble in water
- not polymers

Question 23

Why are lipids in soluble in water?

Answer 23

-Lipids are made up of C-H bonds which are non-polar and hydrophobic. Since “like” dissolves “like” and water is polar, lipids are not soluble in water

Question 24

Structure of fatty acids

Answer 24

• Carboxyl group (COOH) at one end of the chain
  -At the other end straight carbon-hydrogen(hydrocarbon) chain

Question 25

What is amphiphilic?

Answer 25

Something that is both hydrophilic and hydrophobic

Question 26

Characteristics of fatty acids(2)?

Answer 26

-Derived from fats and oils -Amphiphilic(hydrophilic carboxyl group, hydrophobic hydrocarbon chain)

Question 27

Saturated vs Unsaturated fatty acids?

Answer 27

Saturated: Carbon chains completely surrounded by hydrogens, no double bonds Unsaturated: Carbon chains missing some hydrogens, results in a double bond and kink in the hydrocarbon chain.

Question 28

How are fats formed?

Answer 28

Fats are formed from three fatty acid chains covalently linked together via ester linkages to a glycerol molecule

Question 29

What is glycerol?

Answer 29

Three carbon compound with each carbon being attached to one hydroxyl group

Question 30

How do ester linkages occur in fatty acids?

Answer 30

OH of carboxyl group of fatty acid reacts with OH group of glycerol and forms an ester linkage releasing one water molecule (oxygen is now bound to carbon)

Question 31

What is the structure of a phospholipid?

Answer 31

-Two hydrocarbon chains(non-polar) - Hydrophilic head group(polar)

Question 32

What is found in the hydrophilic head group of the phospholipid?

Answer 32

-Phosphate groups -Charged Molecules

Question 33

Characteristics of the lipid bilayer?

Answer 33

-Fluid -Things inserted into it can move laterally -Temperature affects it fluidity/ridgidity

Question 34

What happened when the lipid bilayer is subject to cold temperatures?

Answer 34

1. there is an increase in phospholipids with unsaturated hydrocarbon tails(the kinks allow for more freedom of movement) 2. Phospholipids decrease their tails lengths

Question 35

What happened when the lipid bilayer is subject to hot temperatures?

Answer 35

1. Less unsaturated fatty acid tails 2. Tail length increases(increases drag)

Question 36

Functions of sugar?

Answer 36

- Energy storage -Building block for nucleic acids -Structural component

Question 37

What two functional groups can be found in sugars?

Answer 37

1. Hydroxyl 2. Carbonyl(aldehyde/ketone)

Question 38

What molecule does alpha 1-4 linkage give rise to?

Answer 38

Maltose and eventually starch

Question 39

What molecule doe beta 1-4 linkage give rise to?

Answer 39

Cellobiose and eventually cellulose

Question 40

What shape is starch?

Answer 40

Spiral

Question 41

What provides more energy starch or fats?

Answer 41

Fats but take longer(better for long term storage)

Question 42

Why do phospholipids assemble into a circular sphere shape?

Answer 42

It is most energetically favourable because no more hydrophobic edges are exposed to the water