Chapter 5 - An introduction to Carbohydrates

Question 1

what four types of macromolecules were crucial to the evolution of the cell?

Answer 1

proteins
carbohydrates
nucleic acids
lipids

Question 2

of the five fundamental characteristics of life, which can proteins and nucleic acids carry out?

Answer 2

information
replication
evolution

Question 3

which fundamental characteristic of life can carbohydrates carry out?

Answer 3

energy

Question 4

what are the monomers of sugars/carbs?

Answer 4

monosaccharides (“one sugar”)

Question 5

what do monosaccharides polymerize to form?

Answer 5

polymers - polysaccharides (“many sugars”)

Question 6

what are small polymers of sugar called?

Answer 6

oligosaccharides (“few sugars”)

Question 7

what is the molecular formula for most sugars/carbohydrates?

Answer 7

(CH2O)n (subscript n refers to the number of carbon hydrate groups)

Question 8

what are some of the functions of carbohydrates?

Answer 8

• raw material for synthesizing other molecules
• providing structural support
• indicating cell identity
• storing chemical energy

Question 9

what are the two possible configuration of the carbonyl group in a sugar molecule? (two possible positions)

Answer 9

aldose - carbonyl group at the end of the carbon chain
forms an aldehyde

ketose - carbonyl group in the middle of the carbon chain
forms a ketone

Question 10

triose

Answer 10

three carbon atoms present

Question 11

pentose

Answer 11

five carbon atoms present (ribose)

Question 12

hexose

Answer 12

six carbon atoms present (glucose and galactose)

Question 13

what characteristics do the carbonyl group and the multiple hydroxyl groups bring to the sugar molecule?

Answer 13

-provides sugars with an array of reactive and hydrophilic functional groups

Question 14

what are the 3 main ways that simple sugars differ from each other?

Answer 14

• location of carbonyl group
• number of carbon atoms present
• spacial arrangement of their atoms (especially positions of hydroxyl (-OH) groups

Question 15

what structures do sugars tend to form in aqueous solutions?

Answer 15

ring structures

Question 16

what is a complex carbohydrate?

Answer 16

polysaccharide (polymer of monosaccharide monomers)

Question 17

disacharides

Answer 17

simplest polysaccharides

-consist of two monosaccharide monomers

Question 18

glycosidic linkage

Answer 18

a covalent bond which links two hydroxyl groups through a condensation reaction
-bonds simple sugars and allows polymerization

Question 19

why can the location and shape of glycosidic bonds vary greatly?

Answer 19

because these linkages can form between any two hydroxyl groups

Question 20

how do plants store sugar?

Answer 20

starch

Question 21

what is starch comprised of?

Answer 21

-mix of branched amylopectin/unbranched amylose

Question 22

how do animals store sugar?

Answer 22

glycogen

Question 23

what is glycogen comprised of?

Answer 23

highly branched glucose polymer

Question 24

what is cellulose?

Answer 24

structural polymer of plants cell walls

Question 25

what is cellulose comprised of?

Answer 25

polymer of glucose monomers

Question 26

chitin

Answer 26

structural polymer of fungi cell walls, some algae, and animal cytoskeletons

Question 27

what is chitin comprised of?

Answer 27

N-acetylglucosamine (NAc) monomers

Question 28

peptidoglycan

Answer 28

provides support for bacterial cell walls

Question 29

what is peptidoglycan comprised of?

Answer 29

alternating monosaccharides

Question 30

which 3 carbohydrates provide structure?

Answer 30

- cellulose - chitin - peptidoglycan

Question 31

did polysaccharides play any role in the origin of life?

Answer 31

probably not. - monosaccharide polymerization requires specialized enzymes - polysaccharides to not catalyze and known reactions - polysaccharide monomers cannot copt themselves because they don't store that information

Question 32

what are glycoproteins made of?

Answer 32

- proteins joined to carbohydrates by covalent bonds that contain sugar groups - they display info outside of the cell

Question 33

what is glycoprotein function? what do they do?

Answer 33

- display information on the outer surface of the cell - key in cell to cell recognition and signaling - each cell has glycoproteins on its surface that identify the type/species of cell

Question 34

why is it possible for there to be so many different types of glycoproteins?

Answer 34

- variety in monosaccharides and how they can be linked - makes it possible for a huge number of oligosaccharides to exist = many combinations of glycoprotein identities for each cell species

Question 35

in chemical evolution, how was energy harnessed and stored?

Answer 35

kinetic energy of sunlight/heat were converted into chemical energy and stored in the bonds of H2CO and HCN

Question 36

today, how is most energy (sugars) produced and stored?

Answer 36

photosynthesis! | -transforms energy of sunlight into chemical energy of C-N bonds in carbohydrates

Question 37

photosynthesis (know reactants/products)

Answer 37

CO2 + H2O + sunlight = (CH2O)n + O2 -plants harvest the kinetic energy of the sun and store it in the bonds of carbohydrates

Question 38

why do carbohydrates hold more free energy than CO2?

Answer 38

Carbohydrates: electrons in C-H and C-C bonds are shared more equally and less tightly. C-H bonds have high free energy CO2: electrons in C-O bonds are held tightly

Question 39

phosphorylase (what is it/what does it do?)

Answer 39

enzyme that catalyzes hydrolysis of glycosidic linkages in glycogen

Question 40

why do most animal cells contain phosphorylase?

Answer 40

so they can readily break down glycogen and provide glucose

Question 41

amylase (what is it/what does it do?)

Answer 41

enzyme that catalyzes hydrolysis of starch | -plays a key role in carbohydrate digestion

Question 42

ATP (what is it/what does it do?)

Answer 42

adenosine triphosphate - produced by carbohydrate reactions - drive endergonic reactions/do work for the cell

Question 43

why are fatty acids even more energized than carbs?

Answer 43

carbs: C-H bonds hold high free energy | fatty acids: they have even more C-H bonds, so more energy!

Question 44

a-linkages vs. b-linkages (characteristics)

Answer 44

``` a linkages are readily hydrolyzed (store energy) b linkages (structural) resist enzymatic degradation ```