CARBOHYDRATES Flashcards
(91 cards)
1
Q
Rapoport-Luebering shunt pathway
A
- Found in RBCs where the reaction catalyzed by phosphoglycerate kinase is bypassed
-
1,3-BPG → 2,3-BPG
- Enzyme: Bisphosphoglycerate mutase
2
Q
Lysosomal acid maltase deficiency
A
Pompe disease (Type II)
- ↑ Glycogen in lysosomes
- Juvenile onset: hypotonia, death from heart failure by age 2
- Adult onset: muscle dystrophy
3
Q
Essential fructosuria
A
Fructokinase deficiency
• Fructose → Fructose-1-P
• Enzyme: Fructokinase or hexokinase
4
Q
What is the substrate of PPP?
A
Glucose-6-phosphate
5
Q
Liver phosphorylase deficiency
A
Hers disease (Type VI)
• Hepatomegaly, mild hypoglycemia
* No liver Glycogen Phosphorylase, so no liver glycogen breakdown = glycogen accumulates there = hepatomegaly
6
Q
Discuss this graph
A
7
Q
most common enzyme defect in glycolysis?
A
Pyruvate kinase
- converts PEP to pyruvate
- presents as hemolytic anemia
8
Q
2 steps in glycolysis produce ATP via substrate-level phosphorylation
A
-
1,3-Bisphosphoglycerate → 3-Phosphoglycerate
- Enzyme: Phosphoglycerate kinase
-
Phosphoenolpyruvate → Pyruvate
- Enzyme: Pyruvate kinase
9
Q
Differentiate PFK-1 and PFK 2
A
10
Q
non-reducing sugar
A
Sucrose
11
Q
Discuss the process of GLUCONEOGENESIS
A
12
Q
Rate-limiting step of glycogenolysis
A
Shortening of glycogen chains
Enzyme: Glycogen phosphorylase
13
Q
What type of glycolysis is utilized by:
- Cells with mitochondria
- Cells with adequate supply
A
AEROBIC GLYCOLYSIS AKA Embden-Meyerhof-Parnas Pathway
End product: Pyruvate
14
Q
Heinz bodies and bite cells are found in what disorder?
A
G6PD deficiency
15
Q
Second Phase of PPP
A
Nonoxidative and Reversible
- Enzymes:
- Transketolases (Cofactor: Thiamine)
- Transaldolases
- Products:
- Ribose-5 phosphate
- Fructose-6phosphate
- Glyceraldehyde-3phosphate
16
Q
NADPH functions
A
o Reductive biosynthesis of fatty acids and steroids
o Glutathione reduction inside RBCs
o Cytochrome P450 monooxygenase system
o Oxygen-dependent bactericidal mechanism of WBCs
o Synthesis of nitric oxide
17
Q
- Flatulence and diarrhea after ingestion of dairy products
- Seen in up to 90% of adults of African or Asian descent are lactase-deficient
A
Lactose intolerance
Lactase deficiency
18
Q
GLUT 1 is found in ___
A
Brain, kidney, colon, placenta, RBC
19
Q
Mono-saccharides
(Hexoses)
A
Glucose, Fructose, Galactose and mannose
20
Q
- Isomers that differ in configuration around only one specific carbon atom (except the carbonyl carbon)
- Examples: glucose and galactose (differ only in position of –OH in C4), glucose and mannose (differ only in position of –OH in C2)
A
EPIMERS
21
Q
Mono-saccharides
(Pentoses)
A
Ribose, Ribulose and Xylulose
22
Q
What type of glycolysis is utilized by:
- Cells without mitochondria
- Cells without sufficient O2
A
ANAEROBIC GLYCOLYSIS
End product: Lactate
23
Q
Muscle phosphorylase deficiency
A
McArdle syndrome (Type V)
Poor exercise tolerance, muscle cramps and myoglobinuria but no lactic acidosis, high muscle glycogen
* because muscle lacks the phosphorylase enzyme, it cannot retrive glucose residues from glycogen, leading to cramps.
* No GP in the muscle, (GP is the rate-limiting enzyme in
glycogenolysis), so no GP, no muscle glycogen breakdown
24
Q
GLut 4 is found in ___
A
Heart and skeletal muscle, adipose tissue
“FHM” fat, heart, muscle
25
Purpose of PENTOSE PHOSPHATE PATHWAY Also known as the Hexose MonoPhosphate shunt
o Produces **NADPH**
o Produces **ribose 5-phosphate** required for biosynthesis of nucleotides
o Provides a mechanism for the metabolic use of 5-carbon sugars
o Take Note: Neither produces nor consumes ATP
26
* Characterized by **Deficiency in NADPH oxidase**
* Converts molecular oxygen into superoxide in leukocytes (especially neutrophils and macrophages) and used in the respiratory burst that kills bacteria
* Severe, persistent, and chronic pyogenic infections caused by catalase-positive bacteria
**CHRONIC GRANULOMATOUS DISEASE**
## Footnote
\*In the absence of NADPH oxidase, neutrophils will not be able to convert oxygen to superoxide, which is used to kill bacteria that they’ve engulfed.
27
Insulin is needed in \_\_\_
GLUT 4 transporter ("FHM" - fat, heart, muscle)
28
Important products of PPP
NADPH and Ribose-5-phosphate
29
Most common cause of congenital lactic acidosis
**Pyruvate dehydrogenase deficiency**
* X-linked dominant
* ↑ lactate (anaerobic glycolysis) + ↓ acetyl CoA (citric acid cycle) leads to brain deprived of acetyl CoA leading to psychomotor
* retardation and death
* Treat with ketogenic diet
30
Where does TCA occur?
* In all cells with mitochondria
* Mitochondrial matrix
* Except: succinate dehydrogenase (inner mitochondrial membrane)
31
What are the fates of Pyruvate?
32
Glucose 6 phosphatase is present in \_\_\_
The **liver** but not in the muscle.
The end product of glycogenolysis in the muscle is Glucose - 6 - Phosphate
33
GLUT 5 is found in \_\_\_
**Small intestine (lumen)**
for the Absorption of **fructose**
34
ATP yield of Glycolysis
35
This final step is shared by gluconeogenesis and glycogenolysis, because both pathways yield glucose.
GLUCOSE-6-PHOSPHATE → GLUCOSE
## Footnote
**Enzyme: Glucose 6-phosphatase**
36
**Classic galactosemia**
(Galactose-1-phosphateuridyltransferase deficiency)
**Galactose-1P + UDP-glucose → UDP-galactose + Glucose-1P**
**Enzyme: Galactose-1-P uridyl transferase (GALT)**
* Autosomal recessive
* More severe symptoms
* Galactosemia, galactosuria, **cataracts**, diarrhea, vomiting, **jaundice**
* Poor growth in children, severe mental retardation, and liver damage
* Premature ovarian failure in females
37
Hexokinase and glucokinase are \_\_\_\_
Isozymes
38
Which step is rate-limiting step of **glycolysis**?
Fructose-6-phosphate → Fructose-1,6-bisphosphate
## Footnote
**Enzyme: Phosphofructokinase-1**
39
Differentiate hexokinase from Glucokinase.
40
* Functional group is a **ketone**
* Carbonyl carbon at any other position
* Example: fructose
Ketose
41
What is the rate-limiting step of Glycogenesis?
**Elongation of glycogen chains i.e., creation of α-(1,4) glycosidic bonds Enzyme: Glycogen synthase**
42
* Optical isomers or stereoisomers
* Pairs of structures that are **mirror images of each other**
* The enantiomers are designated as a D-sugar (Dextrorotatory) and an L-sugar (Levorotatory)
* D-sugars are more common
ENANTIOMERS
43
What are the substrates for gluconeogenesis?
o Intermediates of glycolysis and the TCA
o **Lactate** through the Cori Cycle
o **Glycerol** and **propionyl CoA** from triacylglycerols
o Carbon skeletons of glucogenic **amino acids**
44
In this cycle, Lactate formed by glycolysis in skeletal muscle is transported to the liver where it is converted back to glucose through gluconeogenesis
Cori cycle
45
Branching enzyme deficiency
**Andersen disease (Type IV)**
Hepatosplenomegaly,↑ polysaccharide with few branch points, death from heart or liver failure before age 5
46
What are the 5 coenzymes of Pyruvate dehydrogenase (pyruvate to Acetyl CoA)?
**o Thiamine pyrophosphate** (from vitamin **B 1** )
**o FAD** (from vitamin **B 2** )
**o NAD+** (from vitamin **B 3** )
**o Coenzyme A** (contains pantothenic acid) (from vitamin **B 5** )
**o Lipoic acid** (antioxidant)
47
Carbohydrates that can act as reducing agents because they have an aldehyde group or a free ketose group
REDUCING SUGARS
48
Insulin is not needed in \_\_\_\_
RBc, intestinal mucosa, liver, brain
49
How may ATPs will be produced for every molecule of ACetyl CoA from tha TCA cycle?
50
Galactokinase deficiency
Galactose → Galactose-1-P
Enzyme: Galactokinase
* Autosomal recessive
* Relatively mild symptoms
* Galactosemia and galactosuria
**• Cataracts in early childhood**
51
Where does PPP occur?
o RBCs and tissues that produce lipids (liver, adipose tissue, adrenals, thyroid, testes, lactating mammaries)
o In the cytosol
52
* Intolerance of ingested sucrose
* Seen in about 10% of the Inuit people of Greenland and Canada
**Sucrase isomaltase complex deficiency**
53
Glucose + Galactose
lactose
54
Disaccharides
55
Which step is rate-limiting in TCA cycle?
**Isocitrate → α-ketoglutarate**
**Enzyme: Isocitrate dehydrogenase**
56
Glucose-6-phosphatase deficiency
**Von Gierke disease (Type Ia)**
↑ Glycogen in liver and renal tubule cells, hypoglycemia, lactic acidosis, ketosis, hyperlipemia
\*because you do not have glucose-6-phosphatase, you cannot produce glucose, resulting to hypoglycemia.
57
Most common type of glycolysis.
Embden-Meyerhof-Parnas pathway
58
Glucose → Sorbitol
Enzyme?
Sorbitol → Fructose
Enzyme?
Aldose reductase
Sorbitol dehydrogenase
59
Discuss the pathway for glycolysis
60
What is the substrate and the end-products of glycolysis?
Glucose to 2 molecules of either pyruvate or lactate
61
3 to 10 sugar units
62
Where does glycogenesis occur?
o Liver and muscle
o Cytosol
63
Complete oxidation of Glucose will yield how many ATPs?
64
* Functional group is an **aldehyde**
* Carbonyl carbon at the end
* Examples: glucose, galactose, mannose
65
What are the products of GLYCOGENOLYSIS?
o Glucose in liver
o Glucose-6-phosphate in muscle
66
Discuss TCA/Kreb's/ Citric Acid Cycle
67
Reactions catalyzed by carboxylase and requires BIOTIN as a cofactor.
**Pyruvate → Oxaloacetate (Pyruvate carboxylase)**
**Acetyl CoA → Malonyl CoA (Acetyl CoA carboxylase)**
**Propionyl CoA → Methylmalonyl CoA (Propionyl CoA carboxylase)**
68
GLUT 3 is found in \_\_\_\_
**Brain**, placenta, kidney
69
What is the rate limiting step in Gluconeogenesis?
**Fructose 1,6-bisphosphate → Fructose 6-phosphate**
**Enzyme: Fructose 1,6-bisphosphatase**
70
SGLT 1 is found in \_\_\_
Small intestine and kidneys
71
Which step is rate-limiting in PPP?
Glucose-6-phosphate → 6-phosphogluconate
Enzyme: **Glucose-6-phosphate dehydrogenase (G6PD)**
72
Protein that serves as a primer for glycogen synthesis when glycogen is completely depleted
GLYCOGENIN
73
What are the products of TCA?
* 2 CO2
* 1 GTP
* 3 NADH
* 1 FADH2
74
Debranching enzyme deficiency
**Cori disease (Type IIIa)**
Fasting hypoglycemia, hepatomegaly in infancy, **↑ limit dextrin**, muscle weakness
75
Where does Gluconeogenesis occur?
o Occurs in the **liver** (90%) and the **kidney (**10%)
o Occurs in **both** mitochondria and cytosol
76
Anaerobic Glycolysis
77
First Phase of PPP
**Oxidative and Irreversible**
* Glucose-6-phosphate dehydrogenase
* Products: 2 **NADPH** and Ribulose-5 phosphate
78
Glucode and Galactose are ___ epimers
C4 epimers
79
Glucose + Glucose
Maltose
80
can undergo interconversion (from α to β, and vice versa) without energy expenditure or the need for enzymes, in a process called **mutarotation**
ANOMERS
81
* Compounds that have the **same chemical formula**
* Glucose, fructose, galactose, and mannose are all isomers of one another because they have the same formula C 6 H 12 O 6
ISOMERS
82
The sugar units are linked together by \_\_\_\_
glycosidic bonds
83
Glucose and Mannose are ___ epimers
C2
84
What are the 2 shuttles for transport of NADH in the ETC?
85
* 1 step in glycolysis produces **NADH**
* This is an oxidation reaction that passes electrons to NAD+ to make NADH
Glyceraldehyde-3-Phosphate → 1,3-Bisphosphoglycerate
## Footnote
**Enzyme: Glyceraldehyde-3-phosphate dehydrogenase**
86
What is the substrate for TCA?
Acety CoA
87
GLUT 2 is found in \_\_\_
**Liver, pancreas,** small intestine **(basement membrane)**, kidney
88
Hereditary fructose intolerance
**Aldolase B deficiency**
## Footnote
**• Fructose-1-P → DHAP + Glyceraldehyde**
**• Enzyme: Aldolase B**
* Profound hypoglycemia and vomiting after consumption of fructose or sucrose
* Jaundice, hemorrhage, hepatomegaly and liver failure, renal dysfunction, hyperuricemia, lactic acidosis, and death
* Symptoms appear after weaning from milk
89
Polysaccharides
\> 10 sugar units
Glycogen, Starch, Cellulose, Inulin
90
where does glycolysis occur?
In the **cytosol** of all mammalian cells
91
Glucose + Fructose
sucrose
