Carbohydrates and lipids

Question 1

What are carbs?

Answer 1

sugars, starches and fibres found in grains, fruits, vegitables and dairy products

Question 2

What are the most abundant biochemical molecules in nature?

Answer 2

carbohydrates - very structurally diverse

Question 3

What do biological molecules contain?

Answer 3

Carbon, hydrogen and oxygen

Question 4

What are carbohydrates aka?

Answer 4

saccharides

Question 5

What is the role of carbohydrates?

Answer 5

Provide a rapid and readily available supply of energy

Question 6

What is the sugar in DNA?

Answer 6

2-deoxyribose

Question 7

What structure do carbs form in DNA double helix?

Answer 7

Sugar-phospahte backbone

Question 8

Where do carbs form markers and what do they do?

Answer 8

Forms markers on cell surface
These aid cell recognition

Eg. Blood group markers

Question 9

What is the carbohydrate classification?

Answer 9

Monosaccharide - general formula (CH20)n
Disaccharide - dimer - 2 mononsaccharides
Oligosaccharide - polymer of 3-20 monosacharides
Polysaccharides - polymer of monosaccharide units linked together

Question 10

Give 4 examples of monosaccharides

Answer 10

Glucose
Galactose
Fructose
Ribose

Question 11

What is the suffix of a monosaccharide?

Answer 11

-ose

Question 12

What is the range of number of carbon atoms in a monosaccharide?

Answer 12

3-10

Question 13

What functional groups do monosaccharides contain?

Answer 13

An aldehyde or ketone

And hydroxyl groups

Question 14

What is glucose referred as and why?

Answer 14

An aldohexose

It contains an aldehyde functional group?

Question 15

What is fructose referred to as, and why?

Answer 15

Ketohexose

Contains a ketone functional group

Question 16

What are the structural isomers of trioses?

Answer 16

1. Glyceraldehyde (aldehyde)
2. Dehydroxyacetone (ketone)

Both are C3H603

See slide 14 for structure

Question 17

What are the 2 hydroxyl group position isomers of glucose?

Answer 17

Galactose and mannose

The hydroxyl and hydrogens swap

See slide 15

Question 18

How do monosaccharides form deoxy?

Answer 18

Hydroxyl group is replaced with Hydrogen

Question 19

What is a sterioisomer?

Answer 19

Isomer with same chemical formula, same order and types of bonds BUT are non-overlapping mirrorimages of one another

Question 20

What are the two differences in sterioisomers?

Answer 20

• Different spatial arrangements
• Different biological functions

Question 21

What are the 2 types of steroeisomers?

Answer 21

D-isomers and L-isomers

Question 22

What do stereoisomers require?

Answer 22

At least 1 Chiral centre (have 4 different groups attached to it)

Question 23

How do we know if a sugar is a D or L stereoisomer?

Answer 23

D - the OH on the bottom chiral centre points right
L - the OH on the bottom chiral centre points left

(on fisher projections where most oxidised carbon (aldehyde) is at top)

Question 24

What 2 forms can monosaccharides exist as?

Answer 24

Open-chain or ring (cyclic) structure joined by a covalent bond

Question 25

What is the name of the process where sugars form ring structure?

Answer 25

Cyclization

Question 26

What percentage of monnosaccarides exist as linear and cyclic?

Answer 26

Equal Cyclic form is preferred and predominates in nature

Question 27

How does a straight chain undego cyclization?

Answer 27

OH group on second to last carbon reacts with carbonyl group

Question 28

What is the name for the cyclic form of a Aldose?

Answer 28

Hemiacetal

Question 29

What is the name of the cyclic form of a ketose?

Answer 29

Hemiketal

Question 30

What is the name given to the new isomeric centre formed by cyclization and its isomers?

Answer 30

Anomeric Carbon Isomers - anomers

Question 31

What are the 2 types of anomers?

Answer 31

alpha (α-anomers) or beta (β-anomers) depends on orientation of the hydroxyl (OH) group attached to the anomeric carbon

Question 32

What is the cyclic form of D-glucose called?

Answer 32

D-glucopyranose

Question 33

How does D-glucopyranose form form D-glucose?

Answer 33

OH group can attack planar C=O group from either side Thus 2 possible hemiacetal products = alpha and beta anomers of D-glucopyranose

Question 34

How many energy rich C-H bonds do glucose and fructose have?

Answer 34

7

Question 35

Where is fructose found?

Answer 35

fruits, honey, berries and melons

Question 36

What structure does fructose form?

Answer 36

A furan-based ring structure (furanose = 5 membered cyclization product) despite being a hexose (=6C)

Question 37

Are monosaccharides or disaccharides for common in nature?

Answer 37

Disaccharides Monosaccharides are rare in nature

Question 38

How does a Disaccharide form?

Answer 38

Condensation (dehydration synthesis) reaction between two monosaccharides. O-glycosidic bond is formed and water is eliminated

Question 39

What is sucrose made from?

Answer 39

alpha-glucose and beta-fructose water formed

Question 40

Give 3 examples of disaccharides?

Answer 40

Sucrose Maltose Lactose

Question 41

What is Maltose made from?

Answer 41

Two glucose molecules joined at carbons 1 and 4 via an alpha -1,4 glycosidic link

Question 42

Where is Maltose found?

Answer 42

In germinating seeds and grain

Question 43

What does the metabolism of maltose yield?

Answer 43

Ethanol and CO2

Question 44

What is lactose made from?

Answer 44

Glucose and galactose molecules joined at carbons 1 and 4 via a beta-1,4 glycosidic link

Question 45

What produces lactose?

Answer 45

lactating mammals - as an energy source for their young

Question 46

Where is sucrose abundantly found?

Answer 46

In plants/sap especially sugar cane and sugar beet Sugar used in food

Question 47

What reaction breaks down disaccharides?

Answer 47

Hydrolysis - addition of water Uses specific enzymes found in gut

Question 48

What do organisms convert soluble sugars into their insoluble form for? (3)

Answer 48

– For storage in the cell (e.g. starch, glycogen) – For building structures (e.g. cellulose in plant cell walls) – For taking part in cellular processes (e.g. generation of glucose for energy)

Question 49

What vital role do long polysaccarides play?

Answer 49

- Energy storage - Structural integrity of an organism

Question 50

What determines the 3D shape and function of a polysaccharide?

Answer 50

Glycosidic linkages determine 3D shape 3D shape determines function

Question 51

What are the 2 polysaccharide components of starch?

Answer 51

Amylose Amylopectin

Question 52

What is Amylose?

Answer 52

long linear chains of alpha 1,4-linked-D-glucose residues that have a coiled structure

Question 53

What is amylopectin?

Answer 53

linear chains of alpha-1,4-linked D-glucose residues joined through alpha-1,6-linked branch points Has a brush-like structure

Question 54

What are the uses of starch in humans and plants?

Answer 54

* Main dietary source of carbohydrate * Main storage polymer in plants

Question 55

Where is starch found in a plant?

Answer 55

In amyloplasts and chloroplasts of plant cells from roots, tubers, seeds and fruits

Question 56

What are amyloplasts?

Answer 56

non-pigmented plant cell organelles. Responsible for synthesis and storage of starch granules through polymerization of glucose

Question 57

What is starch digested by?

Answer 57

- Amylase in saliva and gut - Maltase and isomaltase in gut only

Question 58

What is starch digested into?

Answer 58

Dextrins (=oligosaccharides), maltotriose, maltose, isomaltose and ultimately glucose

Question 59

What is glycogen?

Answer 59

Complex branched polysaccharide of linear chains of alpha - 1,4- linked D-glucose residues joined through alpha -1,6-linked branch points

Question 60

How does structure of glycogen and amylopectin differ?

Answer 60

Branch points occur more frequently (every 8-12 residues) in glycogen vs 4-30 in amylopectin

Question 61

As well as in animals, which other organisms is glycogen found in?

Answer 61

fungi and bacteria

Question 62

Where is glycogen found?

Answer 62

In liver and muscle cells

Question 63

How much glycogen does blood typically have at a given time?

Answer 63

5-6mM

Question 64

What is cellulose?

Answer 64

The major structural polysaccharide of plants Unbranched homopolymer composed of β-1,4 linked glucose monomers.

Question 65

What is the structure of cellulose?

Answer 65

Long, straight chains - form rigid fibres, with high tensile strength (due to hydrogen bonding between fibres)

Question 66

What are glycoproteins?

Answer 66

Proteins that contain oligosaccharide chains attached covalently to the protein structure

Question 67

What do glycosylated membrane proteins play an important role in?

Answer 67

Immune recognition

Question 68

What do secreted glycoproteins make up?

Answer 68

mucins and the glycocalyx

Question 69

What are glycolipids ?

Answer 69

Lipids that contain oligosaccharide chains attached covalently to their lipid structure

Question 70

What are glycoproteins often associated with

Answer 70

phospholipids on outer surface of the cell membrane

Question 71

What do glycolipds function as?

Answer 71

- Recognition sites - Attachment factors - Membrane stabilisers

Question 72

What are sphingolipids?

Answer 72

A subtype of lipid which include: - Ceramide (signalling molecule) - Sphingomyelin (membranes)