Zaidi Comp Flashcards
GLUT 1
GLUT 2
GLUT 3
GLUT 4
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)
- stage 1 of glycolysis
- glucose → ____
- ____ ATPs consumed
- ____ ATPs generated
- strategy of stage 1:
- stage 2 of glycolysis
- G3P → ____
- ____ ATPs consumed
- ____ ATPs generated
- G3P
- 2
- 0
- trap glucose in cell and form a compound that can be readily cleaved into 2 phosphorylated 3-carbon units
- pyruvate
- 4
- 0
glycolysis:
- glucose → ____ (via ____ )
- Glucose 6-Phosphate → ____ (via ____ )
- Fructose 6-P → ____ (via ____ )
- F, 1-6 BP → ____ (and DHAP) (via ____ )
- G3P → ____ (via ____ )
- 1, 3 BPG → ____ (via ____ )
- 3-PG → ____ (via ____ )
- 2-PG → ____ (via ____ )
- PEP → ____ (via ____ )
- Glucose 6-Phosphate (via hexokinase)
- Fructose 6-Phosphate (via phosphoglucose isomerase)
- Fructose 1,6-BP (via PFK)
- G3P (via aldolase)
- 1, 3 BPG (via G3PDH)
- 3-PG (via phosphoglycerate kinase)
- 2-PG (via phosphoglycerate mutase)
- PEP (via enolase)
- pyruvate (via pryuvate kinase)
major regulatory enzymes of glycolysis
hexokinase
PFK (rate-limiting step)
Pyruvate kinase (irreversible step)
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
- fructose
- galactose
- fat
regulation of glycolysis in muscle:
____ levels regulate glycolysis
ATP
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 = ____
- glucose
- glucokinase
- hexokinase
- glucokinase
- PFK
- F-2, 6-BP
- citrate
- phosphorylation
- inactive
- active
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
- PFK
- pyruvate and acetyl CoA
- fatty acids
lactose intolerace is the inabilty to metabolize ____
caused by deficiency in ____ , which breaks down lactose to glucose and galactose
lactose
lactase
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 ____
- galactosemia
- cataracts
gluconeogeneis:
occurs in ____ and ____
converts ____ into ____
major precursors:
____ of ATP/GTP consumption
liver and kidneys
pyruvate into glucose
lactate, amino acids, and glycerol
3
gluconeogenesis:
- pyruvate → ____ via ( ____ )
- Pyruvate carboxylase (PC) is a ____ enzyme
- OAA transported to cytoplasm (out of mitochondria via ____ shuttle
- OAA → ____ → ____ → ____ → ____ → ____
- G3P → ____
- fructose 1,6-BP → ____ (via ____ -rate-limiting step)
- fructose 6-phosphate → ____
- glucose 6-phosphate → ____ (via ____ )
- OAA (via pyruvate carboxylase)
- mitochondrial
- malate
- PEP → 2-PG → 3-PG → 1,3-BPG → G3P
- Fructose-1,6-BP
- Fructose 6-Phosphate (via fructose 1,6-bisphosphatase)
- glucose -phosphate
- glucose (via glucose 6-phosphatase)
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
- ER
- T1
- T2
- T3
gluconeogenesis bypases the irreversible steps of glycosysis through 4 enzymes
pyruvate carboxylase
PEP carboxykinase
fructose 1,6-bisphosphatase
glucose 6-phosphatase
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
- PFK
- PFK2 and fructose bisphosphatase 2 (FBPase2)
- insulin and glucagon
- glycolysis
- gluconeogenesis
cori cycle:
____ produced in skeletal muscle and RBCs can be converted back to ____ in the liver
pyruvate can enter the gluconeogenic pathway and regenerate ____
lactate, pyruvate
glucose
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
- homopolymer
- a-1,4- glycosidic bonds
- a-1,6-glycosidic bonds
- hydroxyl
- glycogenin
- non-reducing
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
- liver, muscle
- granules
- enzymes
- storage
functions of glycogen:
____ glycogen: regulates blood glucose levels
____ glycogen: provides reservoir of fuel (glucose) for physical activity
liver
muscle
key steps of glycogenesis:
- ____ and ____ of glucose
- glucose 6-phosphate → ____ (via ____ )
- glucose 1-phosphate → ____ (via ____ )
- ____ of a glycogen primer
- ____ ____ (rate-limiting step)
- catalyzes transfer of glucose from UDP-glucose to non-reducing end of glycogen)
- ____ ____ (rate-limiting step)
- ____ of glycogen chains
- when glycogen reach _____ residues, a fragment (7 residues long) is broken off and reattached through an ____ bond via ____ )
- branching increases ____ of glycogen
- trapping and activation
- glucose 1-phosphate (via PGM)
- UDP-glucose (via UDP-glucose pyrophosphorylase)
- elongation
- glycogen synthase
- branching
- 11, a-1.6 bond, glucosyl (4:6) transferase
- solubility
glycogenolysis:
- in liver:
- in muscle:
- 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)
4 key enzymes of glycogenolysis:
- glycogen phosphoryalse (rate limiting)
- adds an ____ and releases a glucose residue as glucose-1-phosphate
- uses ____ ____ (vitamin B6) as a cofactor
- PGM
- converts ____ to ____
- transferase (debranching enzyme) transfers a block of ____ of remaining 4 glucose to the non-reducing end
- a-1,6 glucosidase (debranching enzyme) convert branched glycogen into a ____ structure for further action by glycogen phosphorylase
- orthophosphate
- pyridoxal phosphate
- PGM
- glucose 1-phosphate to glucose 6-phosphate
- 3
- linear (by taking the last of the 4 glucoses that was branched)
glycogen synthase:
- non-phosphorylated “a” : ____ form
- phosphorylated “b” : ____ form
- phosphorylated by ____
- under control of ____
- allosteric regulation, ____ is a powerful activator
- active
- inactive
- glycogen synthase kinase (GSK)
- insulin
- glucose -6- phosphate
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
- liver glycogen phosphorylase is inactivated by free ____
- active
- inactive
- R and T
- glucose
- active
- AMP
- inactive
- glucose
- glycogensis favored in ____ state
- blood glucose ____
- insulin ____
- cellular ATP ____
- glycogenolysis favored in ____ state
- blood glucose ____
- glucagon ____
- glycogenolysis also favored during ____
- cellular ____ high
- ____ high
- fed
- high
- high
- high
- fasting
- low
- high
- exercise
- calcium
- AMP
glycogen metabolism regulation by insulin:
- four key protein involved
- GLUT ____
- protein kinase ____
- protein phosphatse ____
- glycogen synthase ____ 3
- net result: glycogen synthesis via activation of ____ and inactivation of ____
- 4
- B
- 1
- kinase
- glycogen synthase, glycogen phosphorylase
glycogen metabolism regulation by glucagon and epinephrine:
- key enzymes and second messengers
- ____ protein
- adenylate cyclase and ____
- protein kinase ____
- protein phosphatase ____
- phosphorylase ____
- net results: glycogen breakdown via inactivation of ____ and activation of ____
- G
- cAMP
- A 1
- kinase
____ ____ is the glucose sensor in liver cells
glycogen phosphorylase
glycogen storage diseases:
- GSD 0 → ____ → ____
- GSD 1 → ____ → ____
- GSD 2 → ____ → ____
- GSD 3 → ____ → ____
- GSD 4 → ____ → ____
- GSD 5 → ____ → ____
- GSD 6 → ____ → ____
- 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
