Carbs & Pathways Flashcards
(128 cards)
1
Q
Empirical formula for most carbohydrates
A
(CH2O)n
2
Q
Functions of carbohydrates (5)
A
1) energy source and storage
2) structural component of cell walls and exoskeleton
3) lubricant
4) protection
5) communication in cell-cell signaling
3
Q
Number of sugars in a oligosaccharide
A
3-10
4
Q
Number of sugars in a polysaccharide
A
> 10
5
Q
What is it called if the carbonyl group is at the end of the carbon chain
A
aldehyde/aldose
6
Q
What is it called if the carbonyl group is not at the end of the carbon chain
A
ketone/ketose
7
Q
same composition and same order of atomic connections but different molecular arrangements in space
A
stereoisomers
8
Q
Pairs of stereoisomers that are mirror images of one another but cannot be superimposed on each other
A
enantiomers
9
Q
When the -OH group on the carbon next to the terminal alcohol carbon is on the right
A
D isomer
10
Q
When the -OH group on the carbon next to the terminal alcohol carbon is on the left
A
L isomer
11
Q
Pairs of stereoisomers that are not mirror images of each other
A
diastereomers
12
Q
Two sugars that differ only in configuration around one carbon atom
A
epimers
13
Q
Six-sided carbohydrate ring structure
A
pyranose
14
Q
Five-sided carbohydrate ring structure
A
furanose
15
Q
The addition of an -OH group to the carbonyl carbon of an aldehyde
A
hemiacetal
16
Q
The addition of an -OH group to the carbonyl carbon of an ketone
A
hemiketal
17
Q
Which carbon from the linear carbohydrate becomes the chiral center
A
C1 (now called the anomeric carbon)
18
Q
What does the former carbonyl carbon become in a ring structure carbohydrate?
A
hydroxyl group
19
Q
In a carbohydrate ring, if the -OH group is on the opposite of the ring as CH2OH, the configuration is…
A
alpha
20
Q
In a carbohydrate ring, if the -OH group is on the same of the ring as CH2OH, the configuration is…
A
beta
21
Q
Bond formed when the -OH from another carbohydrate comes together with the hemiacetal/hemiketal of the carbohydrate
A
glycosidic bond
22
Q
Glycosidic bond with a methanol, glycerol, sterol, phenol or base
A
aglycone
23
Q
What is formed from a glycosidic bond between a sugar and steroid
A
cardiac glycosides
24
Q
Monosaccharides can be oxidized by mild oxidizing agents such as…
A
Cu2+ ions
25
What is the carbonyl carbon oxidized to in reducing sugars
carboxyl group
26
Two reducing sugars we learned
lactose and maltose
27
Two non-reducing sugars we learned
sucrose and trehalose
28
Polysaccharide storage in plants
starch
29
Two types of starches in plants
Amylose and Amylopectin
30
Unbranched polymer of alpha-1 -> alpha-4 linked D-glucose molecules
amylose
31
Polymer of alpha-1 -> alpha-4 linked D-glucose with alpha-1 -> alpha-6 branches every 24-30 residues
amylopectin
32
Polymer of alpha-1 -> alpha-4 linked D-glucose with alpha-1 -> alpha-6 branches every 8-12 residues
glycogen
33
Benefit of storing glycogen over glucose
Can store higher concentrations as glycogen
34
What is inulin a polysaccharide of?
Fructose
35
Inulin is soluble in water and not digested. What is its ultimate fate in the body?
Filtered through the kidneys and excreted in urine
36
What is inulin excretion used to determine?
glomerular filtration rate (GFR)
37
Polysaccharide made by yeast and bacteria which is made up of a1-a6 linked poly-D-glucose also with a1-a3, a1-a2, and a1-a4 branches.
Dextrans
38
Where can dextrans be found in the human body?
dental plaque
39
Linear, unbranched glucose polymer whose residues have the beta configuration
cellulose
40
Contain amino sugars and uronic acids.
Glycosaminoglycans
41
Proteins containing branched or unbranched oligosaccharide chains. Carbohydrates attached via their anomeric carbon.
Glycoproteins
42
Too little glucose
hypoglycemia
43
Symptoms of hypoglycemia
lethargy, coma, permanent brain damage, death
44
Too much glucose
hyperglycemia
45
Symptoms of hyperglycemia
impaired blood flow, changes in osmolality of bodily fluids, intracellular acidosis, and increased superoxide radical production
46
What is this process doing? Drop of blood added to test strip containing glucose oxidase. The glucose is then oxidized to gluconolactone which has water added to it to form gluconic acid. Gluconic acid reacts with ferricyanide to form ferrocyanide. An electrode test strip oxidizes ferrocyanide which generates current.
measuring blood glucose
47
Normal A1C
5%
48
Diabetics A1C goal
7%
49
Level that untreated diabetic A1C can reach
13%
50
Sugar in which the anomeric carbon is not involved in a glycosidic bond and therefore can undergo oxidation
reducing sugar
51
sugar in which the anomeric carbon is involved in a glycosidic bond and cannot undergo oxidation
non-reducing sugar
52
Isomers of monosaccharides that differ in configuration about the C1 carbon
anomers
53
Four roles of glucose as a precursor
1) synthesis of structural polymers
2) oxidation via pentose phosphate pathway
3) oxidation via glycolysis
4) storage
54
What is the most highly conserved metabolic pathway?
Glycolysis
55
Net yield from glycolysis (one glucose molecule)
2 ATP, 2 NADH, 2 pyruvate, 2 H20
56
What three things use only glucose for energy
brain, red blood cells, and sperm
57
What cells do not need insulin for their glucose transporters
liver cells
58
Compare general hexokinase and glucokinase, the enzyme catalyzing the first step in glycolysis
* Hexokinase is in most tissues, glucokinase in liver
* affinity for glucose much higher in hexokinase
* hexokinase inhibited by glucose-6-phosphate, glucokinase is not
59
Positive regulators of phosphofructokinase-1 (2)
1) AMP (indication of low energy in cell)
| 2) fructose-2,6-bisphosphate
60
Negative regulators of phosphofructokinase-1 (3)
1) ATP (indication of high energy in cell)
2) citrate
3) H+
61
Key regulatory enzyme in glycolysis which is activated by fructose-1,6-bisphosphate and dephosphorylation and inhibited by ATP and phosphorylation
pyruvate kinase (converts phosphoenolpyruvate to pyruvate)
62
Cancer cells carry out glycolysis at much higher rate than normal cells, even when oxygen is available
Warburg effect
63
Fate of pyruvate under anaerobic conditions in humans
lactic acid
64
Fate of pyruvate under anaerobic conditions / fermentation
ethanol
65
Fate of pyruvate under aerobic conditions
converted to Acetyl-CoA in mitochondria
66
Where do we get galactose usually
lactose digestion
67
What is galactose metabolized into
glucose-1-phosphate
68
An excess build up of what causes cataracts and CNS damage
galactitol
69
Defect in galactose-1-phosphate uridyltransferase (GALT) which results in a galactose-1-phosphate and galactitol build up
Galactosemia
70
What is galactose-1-phosphate toxic to (in excess)
the liver
71
Treatment for galactosemia
removal of lactose and galactose from the diet
72
What is fructose converted to in the liver
fructose-1-phosphate
73
What does aldolase B cleave fructose-1-phosphate into in glycolysis/fructose metabolism
dihydroxyacetone phosphate (DHAP) and Glyceraldehyde
74
Why can fructose-1-phosphate accumulate easily
the activity of fructokinase exceeds that of aldolase B
75
What type of regulator is fructose-1-phosphate for several enzymes of carbohydrate metabolism
allosteric regulator
76
What can accumulation of fructose-1-phosphate do in the liver?
inhibit oxidative phosphorylation and cause damage
77
How does fructose build-up lead to high concentration of uric acid?
ADP and AMP accumulate
78
Results of fructose bypassing phosphofructokinase-1 in glycolysis (2)
1) high levels of lactic acid
| 2) high levels of lipogenesis
79
Two genetic deficiencies of fructose metabolism
1) aldolase B deficiency - fructose intolerance
| 2) fructokinase deficiency - essential fructosuria
80
Gluconeogenesis occurs primarily in the ____ (90%) and some in the _____ (10%)
Liver; Kidney
81
Glucose can be made via gluconeogenesis from what three precursors
1) amino acids
2) lactate
3) glycerol
82
Three irreversible reactions in glycolysis
1) glucose to glucose-6-phosphate (E: hexokinase)
2) phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate (E: phosphofructokinase-1)
3) conversion of phosphoenolpyruvate to pyruvate (E: pyruvate kinase)
83
The reaction of pyruvate to oxaloacetate by pyruvate carboxylase requires what other three things
1) bicarbonate
2) ATP
3) biotin (co-factor)
84
Strong allosteric activator of pyruvate carboxylase
acetyl CoA
85
What stimulates and inhibits PEP carboxykinase (PEPCK)
1) glucagon stimulates
| 2) insulin stmulates
86
high levels of citrate is an indicator of what
that the cell is meeting its energy needs
87
The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate by fructose 1,6-bisphosphatase-1 (FBPase-1) is a key regulatory step in gluconeogenesis. What inhibits it?
AMP
88
Fructose 2,6-bisphosphate is an important regulator of both PFK-1 (glycolysis) and FBPase-1 (gluconeogenesis). Which enzyme, part of a single protein, forms it and which breaks it down?
Formed from fructose-6-phosphate by phosphofructokinase-2 (PFK-2). Broken down by fructose 1,6-bisphosphatase-2 (FBPase-2)
89
How does Fructose 2,6-bisphosphate regulate PFK-1?
Activates it by increasin its affinity for fructose 6-phosphate
90
How does fructose 2,6-bisphosphate regulate FBPase-1
it inhibits it
91
What happens to fructose 2,6-bisphosphate levels when glucose is high?
1) PFK-2 activated
2) more F26BP produced
3) PFK-1 more active
4) increased glycolysis
92
What happens to fructose 2,6-bisphosphate levels when glucose is low?
1) FBPase-2 activated
2) less F26BP present
3) inhibition of FBPase-1 relieved
4) increased gluconeogenesis
93
Name of the enzyme catalyzing the conversion from glucose 6-phosphate to glucose
glucose 6-phosphatase
94
Where is glucose 6-phosphatase located
Endoplasmic reticulum of only liver and kidney
95
Glycerol is phosphorylated by glycerol kinase and enters gluconeogenesis at level of....
dihydroxyacetone phosphate (DHAP)
96
Lactate generated by glyolysis in muscle is transported to live. In the liver lactate is converted to glucose, which can then be transported back as fuel. What is this process called?
Cori cycle
97
How is glycogen stored in cells?
In large cytosolic granules
98
Structure of glycogen
1-4 linked glucose with 1-6 branches
99
The addition and removal of glucose to glycogen occurs at which end
non-reducing ends
100
Three enzymes which catalyze glycogen breakdown
1) glycogen phosphorylase
2) glycogen debranching enzyme
3) phosphoglucomutase
101
Removes glucose from non-reducing ends of glycogen
glycogen phosphorylase
102
What does glycogen phosphorylase needs a a cofactor
Pyridoxal Phosphate
103
When does glycogen phosphorylase stop and what is required to alleviate this?
The enzyme stops when it reaches four glucose molecules from an a1-a6 branch point. Further degradation requires glycogen debranching enzyme
104
Two activities of glycogen debranching enzyme
1) transferase activity moves 3 glucose molecules from branch to non-reducing end
2) glucosidase activity removes remaining glucose molecule
105
Enzyme catalyzing conversion of glucose 1-phosphate to glucose 6-phosphate
phosphoglucomutase
106
Glucose 6-phosphate is converted to glucose by glucose 6-phosphatase. Where is this enzyme found?
It is expressed by liver and kidney cells
107
Starting point of glycogen synthesis
glucose 6-phosphate
108
Glucose 6-phosphate is converted to glucose 1-phosphate at the beginning of glycogen synthesis. What happens next?
It's converted to UDP-glucose by UDP-glucose pyrophosphorylase
109
When the glucose residue is added to the non-reducing end of the growing glycogen chain by glycogen synthase, what is removed?
UDP is removed from UDP-glucose.
110
Describe the initiation of a glycogen branch chain
Requires a primer, which is usually a preformed a1-a4 plyglucose chain or branch having at least 8 glucose residues
111
What acts as both an enzyme and primer for a newly formed glycogen chain?
Glycogenin
112
Structure of glycogen phosphorylase
Homo dimer. Each subunit exists in two forms, a (catalytically active) and b (less active)
113
What is the activity of glycogen phosphorylase when its Ser residues are phosphorylated?
Active (a form).
114
Enzyme phosphorylating glycogen phosphorylase
phosphorylase b kinase
115
Enzyme dephosphorylating glycogen phosphorylase
phosphoprotein phosphatase 1 (PP1)
116
Glycogen phosphorylase regulation in the muscle. What does epinephrine do?
Increase Ca2+, increased AMP stimulates kinases
117
Glycogen phosphorylase regulation in the liver. What stimulates intracellular kinases?
glucagon
118
Four things inhibiting glycogen phosphorylase
1) ATP
2) glucose 6-phosphate (muscle)
3) glucose (liver)
4) insulin
119
What form is glycogen phosphorylase in when glucose levels are low?
glycogen phosphorylase a
120
What form is glycogen phosphorylase in when glucose levels are high?
glycogen phosphorylase b
121
Is glycogen synthase phosphorylated in its active "a" form?
No. It's unphosphorylated
122
Is glycogen synthase phosphorylated in its inactive "b" form?
Yes.
123
Activators of glycogen synthase (3)
1) insulin
2) glucose 6-phosphate
3) glucose
124
Inhibitors of glycogen synthase (2)
1) glucagon
| 2) epinephrine
125
What type of receptor do muscle cells lack (in relation to energy metabolism)
Glucagon receptors
126
What is special about pyruvate kinase in muscle cells?
It isn't phosphorylated by protein kinase A. Glycolysis stays active when levels of cAMP are high
127
Three things that muscle cells due in response to insulin
1) increase glucose uptake
2) increase glycogen synthesis
3) increase glycolysis
128
Is hypoglycemia too little glycogen or glucose?
Glycogen
