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Carbohydrates Flashcards

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1
Q

What are carbohydrates made of?

A

carbon
hydrogen
oxygen

means hydrated carbon

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2
Q

what functional group do carbohydrates have?

A

carbonyl group (C=O)
- ketone or aldehyde

multiple hydroxyl groups (OH)

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3
Q

How are carbohydrates classified?

A

based on the number of monomer units/sugar residues

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4
Q

what are considered sugars?

A

monosaccharides and disaccharides

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5
Q

physical property of monosaccharides?

A

colourless, crystalline solids

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6
Q

are monosaccharides soluble in water?

A

yes!
soluble in water, insoluble in non-polar solvents

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7
Q

general formula of sugar?

A

(CH2O)n

where n=3-7

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8
Q

formula of glucose?

A

C6H12O6

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9
Q

use of monosaccharides?

A
  1. important as ENERGY STORES (respiratory substrate) to produce ATP during aerobic respiration
  2. building blocks for tue synthesis of disaccharides and polysaccharides
  3. raw material for synthesis of other organic molecules (nucleotides, amino acids, fatty acids)
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10
Q

aldo vs keto sugars?

A

aldo: carbonyl group is on carbon atom 1

keto: carbonyl group on any of the carbon atoms other than carbon atom 1

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11
Q

a special property of aldo-monosaccharides?

A

STRONG REDUCING AGENTS

aldehyde groups are easily oxidised to carboxylic acids

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12
Q

structure of monosaccharides?

A

linear (open chain) or ring structure

RING STRUCTURE PREFERRED, energetically more stable

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13
Q

what is an anomeric carbon?

A

the carbon that is bonded to TWO oxygen atoms

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14
Q

alpha vs beta glucose?

A

depends on configuration of hydroxyl group that is bonded to the anomeric carbon

ALPHA: OH group lying BELOW the plane of the ring

BETA: OH group lying ABOVE the plane of the ring

ABBA!!!

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15
Q

how to form a disaccharide?

A

formation of glycosidic bond: condensation reaction (loss of one water molecule) between two monosaccharides to form a disaccharide

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16
Q

define glycosidic bond

A

covalent

the bone formed beyween the anomeric carbon of one sugar unit and another carbon atom on the other sugar unit

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17
Q

how to break down disaccharide into its constituent monosaccharides?

A

HYDROLYSIS

incubation with dilute acid at 100°C (acid hydrolysis)
OR
incubation with an enzyme

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18
Q

what is sucrose made of?

A

glucose
fructose

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19
Q

what is lactose made of?

A

galactose and glucose

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20
Q

what is maltose made of?

A

glucose and glucose

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21
Q

what is an a(1,4) glycosidic bond?

Study These Flashcards
A

a glycosidic bond between carbon atom 1 or one glucose and carbon atom 4 of the other in the a configuration

22
Q

why does the Benedict’s test not work on non-reducing sugars?

Study These Flashcards
A

non-reducing sugars like sucrose have no free carbonyl group, thus cannot participate in the redox reactions characteristic of reducing sugars

23
Q

what are polysaccharides?

Study These Flashcards
A

macromolecules of a few hundred to a few hundred thousand monosaccharides joined by glycosidic bonds

24
Q

general function of polysaccharides?

Study These Flashcards
A

storage materials (starch, glycogen)

structural materials (cellulose)

25
examples of storage polysaccharides and where they are found?
starch: plant cells glycogen: animal cells and bacteria
26
what are a(1,4) glycosidic bonds and where are they found?
linear, unbranched chains unbranched amylose amylopectin glycogen
27
what are a(1,6) glycosidic bonds and where are they found?
branched chains amylopectin glycogen
28
what is starch made of?
only a-glucose unbranched amylose (10-30%) branched amylopectin (70-90%)
29
where is starch stored?
in plant cells as starch grains - within the chloroplasts - within the amyloplasts (specialised plastids for starch storage)
30
structure of amylose?
unbranched chain consists of hundreds to thousands of a-glucose residues joined by a(1,4) glycosidic bonds helical structure (compact) 6 glucose units per turn in the helix
31
why is amylose good for storage?
bulky, poorly soluble in water, does not exert osmotic influence in the cell
32
what is amylopectin made of?
a(1,4) glycosidic bonds a(1,6) glycosidic bonds (branched)
33
how often do branch points occur? average branch length?
branch points: every 12-30 residues average branch length: 24-30 residues
34
advantages of branching in amylopectin?
1. allow a larger number of enzymes to act on it at any one time so it can be easily hydrolysed 2. highly compact (amylopectin has twice as many glucose residues as amylose)
35
how does starch being a large molecule (hundreds and thousands of glucose monomers) make it advantageous in storage?
insoluble, does not affect the water potential within cells and living organisms
36
how many monomers is starch composed of and how does that help in storage?
composed or several hundreds to thousands of glucose monomers, a large store of carbon (respiratory substrate)
37
advantages of amylopectin being highly branched
compact, a large number of free ends available for hydrolysis at any one time
38
advantage of anomeric carbon being involved in glycosidic bond formation in starch storage
starch is unreactive and chemically stable compound
39
where is glycogen found?
LIVER, as much as 10% of our liver mass, used as a source of glucose to maintain blood sugar levels SKELETAL MUSCLE, 1-2% of muscle mass, fuel source to generate ATP for muscle contraction
40
what is glycogen made of?
a glycose - similar to amylopectin but more extensively branched - a(1,6) glycosidic bonds occur every 8-12 glucose units - more compact than amylopectin
41
what happens when I2 in KI is added to glycogen in water?
gives a red-violet colour
42
how is glycogen good for storage? (five things to consider)
large, insoluble, does not affect the water potential within cells and living organisms composed of several hundreds to thousands of glucose monomers, act as a large store if carbon (respiratory substrate) a(1,4) glycosidic bonds make it easily hydrolysed by enzymes glycogen phosphorylase highly branched due to a(1,6) glycosidic bonds, highly compact, larger number of free ends available for hydrolysis by amylase at any one time anomeric carbon involved in glycosidic bone formation, unreactive and chemically stable
43
what is cellulose made of?
b(1,4) glycosidic bonds
44
how does cellulose form a long, unbranched, straight chain?
alternate monomers are inverted
45
how are cellulose chains stabilised?
chains run parallel to each other (up to 10,000 b-glucose molecules) and their hydroxyl groups (OH) project outwards from each chain
46
What forms microfibrils?
Cross linked cellulose chains! Made of 60-70 Diameter of up to 25nm
47
What forms macrofibrils?
Microfibrils that associate with other, non-cellulose polysaccharides and arrange in larger bundles Make up the cell wall!
48
Properties of cellulose? How do these properties come about?
1. High tensile strength , stable, valuable structural material as cellulose fibers are laid down in DIFFERENT ORIENTATIONS in DIFFERENT LAYERS of the plant cell wall, permits the cell wall to withstand forces exerted in all directions 2. Full permeability: to water nd solutes, important for proper functioning of plant cells
49
What digests cellulose?
CELLULASE (an enzyme that catalyses the digestion of cellulose to glucose)
50
How does the structure of cellulose support its function?
1. Large molecule! Insoluble, makes a good structural material 2. B-glucose units linked by B(1,4) glycosidic bonds (different molecular shape from a(1,4) glycosidic bonds in amylose and amylopectin: few organisms produce cellulase, amylase can on,y hydrolyse a(1,4) glycosidic bonds found in starch, so cellulose is stable 3. Alternate inverted B-glucose units linked by B(1,4) glycosidic bonds allow cellulose to form Ling, unbranched, straight chains, extensive hydrogen bonds form between parallel chains, straight parallel chains can be grouped into microfibrils, eventually cluster into macrofibrils, provides high tensile strength for structural support

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