Test 3 Review Flashcards
Enzymes of irreversible reactions in glycolysis in liver
Glucokinase
Phosphofructokinase
Pyruvate kinase
Gluconeogenesis
Synthesis of glucose from noncarbohydrate precursors
Major precursors are lactate, amino acids and glycerol (not fatty acids)
Pathway converts pyruvate into glucose
Pathway is not a reversal of glycolysis
3 reactions in glycolysis are irreversible
Hexokinase step
Phosphofructokinase step
Pyruvate kinase step
Gluconeogenesis occurs in
Liver
Gluconeogenesis
Occurs in liver
Synthesis of glucose from noncarbohydrate precursors
Major precursors are lactate, amino acids and glycerol
Pathway converts pyruvate into glucose
Pathway not a reversal of glycolysis
Bypass the pyruvate - get it from the mitochondria
This pathway converts pyruvate into glucose
gluconeogenesis
3 irreversible reactions in glycolysis in liver
Glucokinase
Phosphofructokinase
Pyruvate kinase
Regulation of Gluconeogenesis
Glycolysis generates ATP, gluconeogenesis consumes ATP
E charge (ATP/ADP ratio) determines which pathway will be most active
Gluconeogenesis and glycolysis are reciprocally regulated
Gluconeogenesis _______ ATP
Consumes
Glycolysis __________ ATP
Generates
Can get glucose from
Glycogen
Glucose Storage
Glycogen
Enzyme most important in getting glucose from glycogen
Phosphorylase
Phosphorylase a
Active form
Phosphorylase b
Inactive form
Glucose 1-phosphate
Gets trapped in cell
Transferase
Debranching enzyme
used to remove long chains
alpha-1,6-glucosidase
Glucose is product
Glycogen Synthesis
UDP-glucose pyrophosphorylase step
Glycogen Synthesis
Branching enzyme step
Branching enzyme breaks alpha (1,4) and forms alpha (1,6) branch points by transferring segments 7 to 8 glucoses in length
Increases solubility
Increases rate at which glycogen can be synthesized and degraded
Regulation of Glycogen Metabolism
Regulated by glucagon (from pancreas) and epinephrine (from adrenal medulla)
- can’t get across membrane like steroid hormones
- these two can block pathways when insulin is present
Insulin
Can stimulate synthesis
–glucagon and epinephrine can block insulin
Citric Acid Cycle
CAC More ATP generated from glucose than glycolysis -net 2 ATP - 2 consumed, 4 made Aerobic conditions Take place in mitochondria vs cytosol
CAC Overview
Oxidation of 2-Carbon units to produce
- 2 CO2 molecules
- 1 GTP
- Electrons in the form of 3NADH and 1FADH2
CAC generates
ONE high E containing GTP
Cellular Respiration
High E electrons are removed from carbon fuels
Electrons reduce O2 - generating a proton gradient
Gradient used to synthesize ATP in oxidative phosphorylation
Glycolysis and TCA cycle
Carbohydrates - glucose - can be converted to pyruvate in glycolysis
Pyruvate from glycolysis can be converted to acetyl CoA –aerobic only
Under anaerobic contitions pyruvate is converted to lactate or ethanol
Aerobic conditions result in pyruvate entering the mitochondria
Pyruvate dehydrogenase
Highly regulated
E1-oxidative decarboxylation of pyruvate
E2-transfer of acetyl group to CoA
E3-Regeneration of the oxidized form of lipoamide
High acetyl CoA directly inhibits
E2
Isocitrate dehydrogenase
Re-dox reaction
Produces NADH
-this step is important in determining the rate of the cycle
alpha-ketoglutarate dehydrogenase
Complex similar to pyruvate dehydrogenase (PDH)
Succinyl CoA synthetase
ONLY step that generates GTP
PDH
Turns on and off the citric acid cycle
Pentose Phosphate Pathway
This is an anabolic pathway, trying to get 5C sugars (ex ribose and deoxyribose)
Produces NADPH needed for reductive biosynthesis
Alternate pathway for the oxidation of glucose
Initial step is rate limiting
-Glucose 6-phosphate dehydrogenate
Problem with Pentose Phosphate Pathway
X-linked recessive
Hemolytic anemia because of deficient levels of NADPH in red cells
Warberg Effect
In hypoxic conditions we are activating glycolysis (produce energy) followed by lactic acid fermentation in the cytosol, not in the mitochondria
SIRT1
Nuclear
When activated will regulate transcription through deacetylation of histones. Genes are wrapped in histones
SIRT3
Mitochondrial
Regulate metabolic processes
