Carbohydrates L13 L14 L15 Flashcards
(117 cards)
1
Q
what forms carbohydrates
A
carbon hydrogen oxygen most abundant organic molecules on earth major energy source for most living things
2
Q
why are they called carbohydrates
A
hydrated carbons
3
Q
what is the role and function of carbohydrates
A
structure role and supplying energy in plants
4
Q
how is glyceraldehyde formed
A
Gycerol remove a hydrogen becomes a monosaccharide
5
Q
what are the types of glyceraldehyde
A
two different forms of glyceraldehyde (depending on the highlighted OH which side is on)
D form – dextro
Or L form – laevo
6
Q
what do monosaccharides contain
A
number of hydroxyl groups
carbon covalently bonded to oxygen
7
Q
what makes a monosaccharide an aldehyde
A
if bonded at end
8
Q
what makes a monosaccharide a ketone (ketose sugar)
A
if in carbon chain
9
Q
what is a chiral carbon
A
four different molecules bound to it
10
Q
what are D and L glyceraldehydes
A
Different compounds
Mirror images of each other
Enantiomers (also stereoisomers)
11
Q
how do D and L glyceraldehydes differ
A
Rotate polarized light differently: either (+) or (-)
D will rotate it to the right
L will rotate it to the left
Handled differently by enzymes
12
Q
what are stereoisomers
A
same chemical formula but OH differs where it is in the chain
13
Q
what is glyceraldehyde
A
triose sugar (3 carbons) aldose sugar (aldehyde group)
14
Q
what is ribose
A
pentose sugar (5 carbons) aldose sugar (aldehyde group)
15
Q
what is glucose
A
hexose sugar (6 carbons) aldose sugar (aldehyde group)
16
Q
what are the main examples of D-versions of hexose sugar
A
D-glucose
D-mannose
D-galactose
17
Q
how many hexose sugar versions are there
A
8 L
8 D
18
Q
what is an epimer
A
differ in position of one of their hydroxyl groups
19
Q
what are examples of epimers
A
glucose and mannose
glucose and galactose
20
Q
monosaccharide examples
A
glucose
mannose
galactose
fructose
21
Q
what do monosaccharide aldehyde groups react with
A
tend to react with their own hydroxyl groups
22
Q
what are most monosaccharides structure
A
most of the time the monosaccharides exist in a cyclic form
23
Q
in a cyclic form what forms alpha glucose
A
if the hydroxyl group points down on the first carbon
24
Q
in a cyclic form what forms beta glucose
A
if the hydroxyl group points up on the first carbon
25
can glucose molecules convert between alpha and beta
In solution can convert between the two alpha/beta
26
what structure can glucose adopt
different ‘chair’ and ‘boat’ conformations
| Glucose more often found in chain configuration as large groupings are less hindered
27
what is the structure of simple 'sugars'
based on linear carbon chains with multiple hydroxyl groups (-OH)
28
what are the most common sugars
D form
29
where is the aldehyde group in aldoses
carbon 1
30
what is the preferred structure of hexose
chains prefer to cyclise and form a 6- membered ring
31
what do hexoses form
hexoses such as glucose, mannose and galactose form 6- membered pyranose rings
32
what does a pentose ribose form
5-membered furanose ring
33
what are ketoses
have a carbonyl oxygen on carbon 2 (keto-group)
34
what are the three most common aldoses
Glucose, Mannose and Galactose
35
how are glucose, mannose and galactose related
cyclise in the same way
36
what are modified monosaccharides important in
glycoproteins and cell walls
37
what can monosaccharides carry
phosphates
38
what is inositol
analogue of a monosaccharide
39
what are inositol phosphates important for
cell signalling mechanisms
| e.g. muscle contractions
40
what can monosaccharides join together to form
```
condensation reaction removes water
through glycosidic bonds
disaccharides - two monomers
oligosaccharides - several monomers
polysaccharides - many monomers
```
41
what prevents monosaccharides alternating between alpha and beta
when glycosidic bond in ring is no longer free to open
| cannot change between the two due to anomeric carbon bound by glycosidic bond
42
what is the lactose percentage in milk
~7%
43
what breaks down lactose
beta galactosidase - lactase
44
where is beta galactosidase in high amounts
in infants digestive system, not in adults
45
what type of enzyme is beta galactosidase
hydrolytic enzyme
| catalyses reaction of lactose with water
46
what is beta galactosidase famous for
genetic studies in E.coli
47
what is an inducible enzyme
gene can be 'turned on' by lactose in medium
| - beta galactosidase
48
what forms a blue colour when beta galactosidase enzyme expressed
galactose derivative X-gal releases a blue colour when the beta-galactosidase gene is expressed (‘turned on’)
49
what happens when a foreign gene is inserted into beta galactosidase
cant hydrolyse
With foreign gene of interest will be white in colour as blue enzyme wont work
Can be used to identify proteins
50
what is beta galactosidase used for in transgenic animals
transgenic animals, the galactosidase sequence can be attached to a ‘transgene’ of interest
The galactosidase enzyme activity is used to show where transgene is being expressed
51
what is sucrose
probably the most abundant disaccharide in nature – a heterodimer of glucose and fructose
The glycosidic linkage is 1-2
52
what is sucrose hydrolysed by
enzyme ‘Sucrase’ or ‘Invertase
53
where does sucrose hydrolysis occur naturally
fruits and honey - a mixture of glucose and fructose is sweeter than sucrose
54
what is dietary glucose used in
energy metabolism by the brain
55
where is fructose used
tends to become directly incorporated into fat
56
what do foods and confectionaries use high-fructose syrups for
sweetener may be more ‘fattening’ than those with ‘sugar’
57
what is maltose
homodimer of glucose
58
what is maltose hydrolysed by
maltase enzyme
59
what is the bond that links monosaccharides
glycosidic bonds
60
where is maltose found
usually only found in low amounts, except as a breakdown product of starch -eg in the ‘malting’ process in barley
61
which monosaccharides are 'reducing' sugars and why
Lactose and maltose are ‘reducing’ sugars as their anomeric carbon can open up
Sucrose is not a reducing sugar as both anomeric carbons are bound to glycosidic bond –When sucrose is split by invertase two reducing sugar are formed
62
what carbon in monosaccharide is used to react to give colour characteristic
OH on carbon 1 free to react with copper ion
63
where is the carbonyl group in ketoses
carbon 2
64
how is five member furanose ring formed
fructose cyclises
65
how can monoscaccharides be modified
to include amino acid groups and phosphate groups
66
what does the stereochemistry of glycosidic bonds determine
susceptibility to enzymic attack
67
where are oligosaccharides not usually found
free in cells or tissues, except as breakdown products of polysaccharides
68
how big are oligonucleotides
~5-15 monomers
69
what are the three main types of polysaccharide that carbohydrates are present as
cellulose
starch
glycogen
70
what does cellulose do
structural in plants
71
what does starch do
storage
72
where is glycogen
high in liver where stored
73
what is the structure of cellulose compared to glucose
Cellulose is a linear homo-polymer of glucose
74
how are glucose monomers joined
beta 1-4 glycosidic bonds
75
what is the structure of cellulose monomers joined
line up end to end
each neighbouring glucose molecule is rotated 180 degrees
thousands of glycan chains lining up parallel
76
what bond joins cellulose molecules
hydrogen
77
where are the hydrogen bonds that join cellulose
between hydroxyl groups
78
what gives cellulose support
surrounded by other polysaccharides for support
79
what gives cellulose strength and rigidity
high strength and rigidity from criss cross structure
80
what reaction is joining the cellulose monomers
condensation reaction Water is largely excluded, making solubilisation very difficult
81
what enzyme do most animals not possess, but what does
enzymes capable of breaking the 1-4 linkage between glucose units
a few microorganisms and fungi do
82
what do ruminants need to get release of glucose
rely on microorganisms with the enzyme that can break the beta 1-4 glycosidic bond
very slow process
83
what can fermentation technology produce
cellulase enzyme
84
what is cellulase for
valuable to be able to release glucose for foods or for biofuels
85
what is characteristic of de-repressed mutants and cellulase
De-repressed mutants have been found that can make large quantities of cellulase
86
what is the growth of a non mutant like with glucose and cellulase present
Glucose gets lower as is used up, till too low
| Cellulase starts to breaks down materials to make glucose
87
what is the growth of a mutant like with glucose and cellulase present
Mutant always has cellulase even when high amount of glucose, to make more glucose
88
how is cellulase made into glucose
cut by three enzymes
- endoglucanase
- exoglucanse
- cellobiase
89
what does endoglucanase do
initial cut into cellulose chain
90
what does exoglucanase do
makes a second cut next to first produces glucose dimer cellobiase
91
what does cellobiase do
breaks down bits into individual glucose molecules
92
what is hemicellulose
complex polymers of xylan and other monosaccharides
93
what is lignin
complex cross-linked polymers of phenolic compounds
94
what can we use biomass for
- Composting
- Feeding to ruminants
- Adding ‘cellulase’ and releasing sugars for biofuels
- Genetically engineering plants to contain their own ‘cellulase’
95
what is chitin
an abundant polymer found in crustaceans, insects and fungal cell walls
96
what are the links to join monomers to form chitin
beta 1-4 linked homopolymer of glucosamine
97
what are starch and glycogen designed for
glucose stores to be rapidly utilised as fuels
98
what is starch's function
plant energy reserves consisting of alpha-amylase and
| amylopectin
99
what is alpha-amylase
enzyme
| linear homopolymer of starch
100
what is amylopectin
branched polymer of starch
| contains up to a million glucose units
101
where is alpha amylase present
present in saliva
102
what does alpha amylase do
randomly attacks the long chain, yielding disaccharides (maltose) and trisaccharides
103
what happens to di- and tri- saccharides that are formed
further degraded in the small intestine by an alpha - glucosidase
104
in animals what attacks amylopectin
alpha and beta - amylase
105
what effect does the attack of alpha and beta amylase have on amylopectin
cannot break 1-6 linkage
106
what starch is very resistant to digestion
potato
| almost crystalline structure
107
what is glycogen with regards to glucose
glucose homopolymer
108
what is glycogen function
major storage polysaccharide in animal cells
109
what are the glycosidic links in glycogen
alpha1-4
| alpha 1-6
110
what particles does glycogen form
cytosolic
111
what effect does greater branching have on glucose and starch storage
more glucose can be packed in smaller volume than in starch
| more 'ends' capable of being attacked by glycogen phosphorylase
112
where is glycogen phosphorylase
liver and muscle
113
what is glycogen phosphorylase
highly-regulated enzyme
114
what is glycogen phosphorylase needed for in animals
energy production during the ‘fight or flight’ response in animals
115
what does glycogen phosphorylase sense
'energy status’ of the cell (ATP + ADP + AMP) particularly the level of AMP
116
what does the enzyme glycogen phosphorylase respond to
stimulation by the nervous system (via Calcium ion release)
| stimulation by adrenaline (via phosphorylation)
117
what is glycogen phosphorylase regulated by
Ca++, AMP and adrenaline
