Zaidi Comp

Question 1

GLUT 1

GLUT 2

GLUT 3

GLUT 4

Answer 1

ubiquitous but expressed highly in brain and RBCs - high affinity

liver - low affinity

neurons - high affinity

skeletal muscle, heart, adipose tissue - insulin dependent (regulated by insulin)

Question 2

1. stage 1 of glycolysis
   
   1. glucose → ____
   2. ____ ATPs consumed
   3. ____ ATPs generated
   4. strategy of stage 1:
2. stage 2 of glycolysis
   
   1. G3P → ____
   2. ____ ATPs consumed
   3. ____ ATPs generated

Answer 2

1. 1. G3P
   2. 2
   3. 0
   4. trap glucose in cell and form a compound that can be readily cleaved into 2 phosphorylated 3-carbon units
2. 1. pyruvate
   2. 4
   3. 0

Question 3

glycolysis:

1. glucose → ____ (via ____ )
2. Glucose 6-Phosphate → ____ (via ____ )
3. Fructose 6-P → ____ (via ____ )
4. F, 1-6 BP → ____ (and DHAP) (via ____ )
5. G3P → ____ (via ____ )
6. 1, 3 BPG → ____ (via ____ )
7. 3-PG → ____ (via ____ )
8. 2-PG → ____ (via ____ )
9. PEP → ____ (via ____ )

Answer 3

1. Glucose 6-Phosphate (via hexokinase)
2. Fructose 6-Phosphate (via phosphoglucose isomerase)
3. Fructose 1,6-BP (via PFK)
4. G3P (via aldolase)
5. 1, 3 BPG (via G3PDH)
6. 3-PG (via phosphoglycerate kinase)
7. 2-PG (via phosphoglycerate mutase)
8. PEP (via enolase)
9. pyruvate (via pryuvate kinase)

Question 4

major regulatory enzymes of glycolysis

Answer 4

hexokinase

PFK (rate-limiting step)

Pyruvate kinase (irreversible step)

Question 5

entry points of other monosaccharides into glyocsis:

• sucrose is a disaccharide of glucose and ____
• lactose is a disacharide of glucose and ____
• fructose quickly turned to ____ in times of high energy

Answer 5

• fructose
• galactose
• fat

Question 6

regulation of glycolysis in muscle:

____ levels regulate glycolysis

Answer 6

ATP

Question 7

regulation of glycoysis in liver:

• goal: to maintain blood ____ levels
• goal: to provide building blocks for other pathways
• trapping of glucose: ____
  
  • no ____ in liver
• rate-limiting step: ____
  
  • activated by ____
  • inhibited by ____
• pryuvate kinase is regulated by ____
  
  • phosphorylated = ____
  • dephosphorylated = ____

Answer 7

• glucose
• • glucokinase
    
    • hexokinase
• PFK
  
  • F-2, 6-BP
  • citrate
• phosphorylation
  
  • inactive
  • active

Question 8

excessive fructose consumption can lead to pathological conditions:

• fructose bypasses the rate-limiting step in glycosis, the ____-catalyzed reaction
• excess fructose is processed by glycolysis to ____ and ____ ____ in an unregulated fashion
  
  • excess acetyl CoA is converted to ____ ____ which results in obesity and fatty liver

Answer 8

• PFK
• pyruvate and acetyl CoA
  
  • fatty acids

Question 9

lactose intolerace is the inabilty to metabolize ____

caused by deficiency in ____ , which breaks down lactose to glucose and galactose

Answer 9

lactose

lactase

Question 10

defects in galactose metabolism:

• disruption in galactose metaoblism is called ____
• classic galactosemia (most common form) is an inherited deficiency in galactose 1-phosphate uridyl transferase activity
• accumulated galactose can be reduced to galactitol to form ____

Answer 10

• galactosemia
• • cataracts

Question 11

gluconeogeneis:

occurs in ____ and ____

converts ____ into ____

major precursors:

____ of ATP/GTP consumption

Answer 11

liver and kidneys

pyruvate into glucose

lactate, amino acids, and glycerol

3

Question 12

gluconeogenesis:

1. pyruvate → ____ via ( ____ )
   
   1. Pyruvate carboxylase (PC) is a ____ enzyme
   2. OAA transported to cytoplasm (out of mitochondria via ____ shuttle
2. OAA → ____ → ____ → ____ → ____ → ____
3. G3P → ____
4. fructose 1,6-BP → ____ (via ____ -rate-limiting step)
5. fructose 6-phosphate → ____
6. glucose 6-phosphate → ____ (via ____ )

Answer 12

1. OAA (via pyruvate carboxylase)
   
   1. mitochondrial
   2. malate
2. PEP → 2-PG → 3-PG → 1,3-BPG → G3P
3. Fructose-1,6-BP
4. Fructose 6-Phosphate (via fructose 1,6-bisphosphatase)
5. glucose -phosphate
6. glucose (via glucose 6-phosphatase)

Question 13

glucose 6-phosphatase:

• located in the lumen of the ____
• ____ transports Glucose 6-phosphate to ER
• ____ transports inorganic phosphate back into cytosol
• ____ transports glucose back to cytoplasm

Answer 13

• ER
• T1
• T2
• T3

Question 14

gluconeogenesis bypases the irreversible steps of glycosysis through 4 enzymes

Answer 14

pyruvate carboxylase

PEP carboxykinase

fructose 1,6-bisphosphatase

glucose 6-phosphatase

Question 15

regulation of glycolysis and gluconeogenesis in liver:

• fructose 2,6-bisphosphate stimulates ____ (rate limiting step in glycolysis)
• the concentration of fructose 2,6-bisphosphate is controlled by a bi-functional enzyme with a kinase and phosphatase domain ( ____ and ____ )
• byfunctional enzyme is regulated by ____ and ____
  
  • insulin: stimulates phosphoprotin phosphatase → ____ is stimulated
  • glucagon: stimulates PKA → ____ is stimulated

Answer 15

• PFK
• PFK2 and fructose bisphosphatase 2 (FBPase2)
• insulin and glucagon
  
  • glycolysis
  • gluconeogenesis

Question 16

cori cycle:

____ produced in skeletal muscle and RBCs can be converted back to ____ in the liver

pyruvate can enter the gluconeogenic pathway and regenerate ____

Answer 16

lactate, pyruvate

glucose

Question 17

structure of glycogen:

• long chain ____ of glucose
• glucose molecule within linear chain linked via ____ bonds
• branch points formed via ____ bonds
• non-reducing ends (multiple) contains a terminal glucose with a free ____ group at carbon-4
• reducing end consists of glucose monomer connected to a protein called ____
• glycogen is degraded and extended from ____ ends

Answer 17

• homopolymer
• a-1,4- glycosidic bonds
• a-1,6-glycosidic bonds
• hydroxyl
• glycogenin
• non-reducing

Question 18

glycogen storage:

• stored in ____ , _____ , and other tissues
• stored as ____
• granules contain not only glycogen but also the ____ needed for glycogen metabolism
• defects in these enzymes can lead to glycogen ____ disorders

Answer 18

• liver, muscle
• granules
• enzymes
• storage

Question 19

functions of glycogen:

____ glycogen: regulates blood glucose levels

____ glycogen: provides reservoir of fuel (glucose) for physical activity

Answer 19

liver

muscle

Question 20

key steps of glycogenesis:

1. ____ and ____ of glucose
   
   1. glucose 6-phosphate → ____ (via ____ )
   2. glucose 1-phosphate → ____ (via ____ )
2. ____ of a glycogen primer
   
   1. ____ ____ (rate-limiting step)
      
      1. catalyzes transfer of glucose from UDP-glucose to non-reducing end of glycogen)
3. ____ of glycogen chains
   
   1. when glycogen reach _____ residues, a fragment (7 residues long) is broken off and reattached through an ____ bond via ____ )
   2. branching increases ____ of glycogen

Answer 20

1. trapping and activation
   
   1. glucose 1-phosphate (via PGM)
   2. UDP-glucose (via UDP-glucose pyrophosphorylase)
2. elongation
   
   1. glycogen synthase
3. branching
   
   1. 11, a-1.6 bond, glucosyl (4:6) transferase
   2. solubility

Question 21

glycogenolysis:

• in liver:
• in muscle:

Answer 21

• liver: glycogen → glucose 1-phosphate (via glycogen phosphorylase- rate limiting) → glucose 6-phosphate (via PGM) → glucose (via glucose 6-phosphatase)
• in muscle: glycogen → glucose 1-phosphate (via glycogen phosphorylase -rate limiting) → glucose 6-phosphate (PGM) → pyruvate (via glycolysis)

Question 22

4 key enzymes of glycogenolysis:

1. glycogen phosphoryalse (rate limiting)
   
   1. adds an ____ and releases a glucose residue as glucose-1-phosphate
   2. uses ____ ____ (vitamin B6) as a cofactor
2. PGM
   
   1. converts ____ to ____
3. transferase (debranching enzyme) transfers a block of ____ of remaining 4 glucose to the non-reducing end
4. a-1,6 glucosidase (debranching enzyme) convert branched glycogen into a ____ structure for further action by glycogen phosphorylase

Answer 22

1. 1. orthophosphate
   2. pyridoxal phosphate
2. PGM
   
   1. glucose 1-phosphate to glucose 6-phosphate
3. 3
4. linear (by taking the last of the 4 glucoses that was branched)

Question 23

glycogen synthase:

• non-phosphorylated “a” : ____ form
• phosphorylated “b” : ____ form
• phosphorylated by ____
  
  • under control of ____
• allosteric regulation, ____ is a powerful activator

Answer 23

• active
• inactive
• glycogen synthase kinase (GSK)
  
  • insulin
• glucose -6- phosphate

Question 24

glycogen phosphorylase:

• phosphorylated “a” form : ____ form
• nonphosphorylated “b” form : ____ form
• both isozymes exist in equilibrium between ____ and ____
  
  • liver glycogen phosphorylase is inactivated by free ____
    
    • default “a” ____ form
  • muscle glycogen phosphorylase is activated by ____
    
    • default “b” ____ form

Answer 24

• active
• inactive
• R and T
  
  • glucose
    
    • active
  • AMP
    
    • inactive

Question 25

1. glycogensis favored in ____ state
   
   1. blood glucose ____
   2. insulin ____
   3. cellular ATP ____
2. glycogenolysis favored in ____ state
   
   1. blood glucose ____
   2. glucagon ____
3. glycogenolysis also favored during ____
   
   1. cellular ____ high
   2. ____ high

Answer 25

1. fed
   
   1. high
   2. high
   3. high
2. fasting
   
   1. low
   2. high
3. exercise
   
   1. calcium
   2. AMP

Question 26

glycogen metabolism regulation by insulin:

1. four key protein involved
   
   1. GLUT ____
   2. protein kinase ____
   3. protein phosphatse ____
   4. glycogen synthase ____ 3
2. net result: glycogen synthesis via activation of ____ and inactivation of ____

Answer 26

1. 1. 4
   2. B
   3. 1
   4. kinase
2. glycogen synthase, glycogen phosphorylase

Question 27

glycogen metabolism regulation by glucagon and epinephrine:

1. key enzymes and second messengers
   
   1. ____ protein
   2. adenylate cyclase and ____
   3. protein kinase ____
   4. protein phosphatase ____
   5. phosphorylase ____
2. net results: glycogen breakdown via inactivation of ____ and activation of ____

Answer 27

1. 1. G
   2. cAMP
   3. A 1
   4. kinase

Question 28

____ ____ is the glucose sensor in liver cells

Answer 28

glycogen phosphorylase

Question 29

glycogen storage diseases:

• GSD 0 → ____ → ____
• GSD 1 → ____ → ____
• GSD 2 → ____ → ____
• GSD 3 → ____ → ____
• GSD 4 → ____ → ____
• GSD 5 → ____ → ____
• GSD 6 → ____ → ____

Answer 29

• 0 → no name → glycogen synthase
• 1 → Von Gierke → glucose 6-phosphatase
• 2 → Pompe → Acid Maltase
• 3 → Cori disease → debranching enzyme (a-1,6-glucosidase)
• 4 → Andersen → glucosyl (4:6) transferase
• 5 → McArdle → muscle glycogen phosphorylase
• 6 → Hers → liver glycogen phosphorylase