Gluconeogenesis, Glycogenesis, Glycogenolysis Flashcards
all carbohydrates enter-
glycolysis
Carbohydrates enter in muscle via
hexokinase
D-Glucose –>
G-6-P
via:
hexokinase
ATP
D-Galactose –>
G-6-P
via:
UDP-Galactose
UDP-Glucose
D-Fructose –>
F-6-P
via:
hexokinase
ATP
Glycogen; Starch –>
G-1-P
via: phosphorylase
G-6-P
via: D-Glucose
Trehalose —>
D-Glucose
via: trehalase
D-Mannose –>
Mannose 6-P –> F-6-P
via: phosphomannose isomerase
Sucrose –>
F6P
via: hexokinase and ATP
synthesis of glucose and/or glycogen from non-carbohydrate sources
-pathway needed by brain
Gluconeogenesis
Glycolytic key enzymes
hexokinase
PFK-1
Pyruvate kinase
Gluconeogenic key enzymes
Glucose-6-phosphatase
Fructose 1,6- bisphosphatase
pyruvate carboxylase
PEP carboxykinase
Sources of Glucose for Gluconeogenesis
Lactate Pyruvate Glucogenic AA Glycerol Odd Chain FA
Importance of gluconeogenesis
Source of blood glucose during fasting and starvation
Removal of waste products such as lactate, glycerol
reaction in conversion of Pyruvate to OAA
carboxylation
reaction in conversion of OAA to PEP
decarboxylation and phosphorylation
Reaction in conversion of PEP to 2-Phosphoglycerate
hydration
Reaction in conversion of 3-Phosphoglycerate to 1,3-Bisphosphoglycerate
phosphorylation
Reaction in conversion of 1,3-BPG to G-3-P
reduction and phosphorylation
reaction in conversion of FBP-1 to F-6-P
hydrolysis and dephosphorylation
reaction in conversion of G-6-P to glucose
hydrolysis and dephosphorylation
uses H2O
11, 9, 3
Produces Pi
11, 9, 6, 1
Uses GTP
2
Products of Reaction 1
ADP + Pi
Products of Reaction 2
GDP + CO2
Products of Reaction 5
ADP
Products of Reaction 6
Pi + NAD+
process of glycogen synthesis in which glucose molecules are added to chains of glycogen for storage
Glycogenesis
site of gluconeogenesis
liver, kidney
site of glycogenesis
liver, skeletal muscle
Steps in Glycogenesis
Formation of G-1-P
Formation of UDP-glucose
Glucose transfer to a glycogen chain
Step 1 glycogenesis
G-6-P ——> G-1-P
Enzyme in Step 1 glycogenesis
phosphoglucomutase
Step 2 glycogenesis
G-1-P + UTP ——–> UDP - glucose
Enzyme in Step 2 glycogenesis
UDP-glucose pyrophosphorylase
Step 3 glycogenesis
UDP-glucose + (glucose)n ———> (glucose) n+1 + UDP
acts as vehicle that carries the glucose molecule which is to be added to the budding glycogen molecule
UDP-glucose
Reaction in step 1 glycogenesis
phosphorylation
uses ATP in glycogenesis
Step 1
breakdown of glycogen to G-6-P or glucose
Glycogenolysis
Steps in glycogenolysis
Phosphorylation/phosphorolysis of Glucose residue
G-1-P Isomerization
Step 1 Glycogenolysis
(Glucose)n + Pi ——-> (glucose) n-1 + G-1-P
Enzyme in Step 1 Glycogenolysis
glycogen phosphorylase
Step Glycogenolysis
G-1-P —–> G-6-P
Enzyme in Step 2 Glycogenolysis
phosphoglucomutase
alternative route for glucose oxidation
not for energy production
HMP
site of HMP
cytosol of liver adipose tissue ovaries testes RBC retina
Steps of HMP
Oxidative
Non oxidative phase
irreversible phase
oxidative
reversible phase
non oxidative
reactions in Oxidative phase
G6P undergoes dehydrogenation and decarboxylation to yield ribulose 5-P
reactions in Non oxidative phase
6 molecules of Ribulose 5P are converted to 5 molecules of Glucose 6P
enzymes used in non oxidative phase
transketolase
transaldolase
ketone
Ribulose 5P
aldose
Ribose 5P
Importance of HMP
I. Provides Ribose 5P
II. Main source of NADPH required in lipid metabolism
required for synthesis of nucleotides and nucleic acids
ribose 5P and many coenzymes
composition of Ribose 5P
ATP GTP UTP CoA NAD/NADH FAD/FADH
G-3-P
F-3-P
Sources of NADPH
A. Reductases
B. Hydroxylases
C. NADPH oxidase
Reductases
Glutathione reductase
Folate, retinal reductase
Reductases of FA, steroid synthesis
Hydroxylases
steroids hydroxylase
NADPH oxidase
phagocytosis (respiratory burst) (WBC)
site of Uronic Acid Pathway
cytosol of liver
Importance of Uronic Acid Pathway
formation of UDP - glucuronate synthesis of L-ascorbic acid GAGs synthesis Conjugation reactions: with bilirubin steroids to make them more soluble easily excreted: detoxication
