Metabolism 1 and 2 : Metabolism overview, carbohydrate metabolism Flashcards
What are the fates of acetyl CoA
Fatty acid synthesis and sterols
Citric acid cycle
Ketone bodies
Preferred fuels of liver
glucose, fatty acid oxidation, amino acids
Preferred fuels of adipose tissue
Fatty acids
Preferred fuels of skeletal muscle
At rest - beta oxidation (FA)
During exercise - glucose
Preferred fuels of heart muscle
Beta oxidation
Preferred fuels of brain
Glucose always, but in starvation it’ll use ketone bodies
Major carbohydrates and fuels in which they are found
Amylose (starch) Sucrose (table sugar, desert) Lactose (milk products) Fructose (fruit and honey) gluocse (fruit, honey) Maltose (barley) trehalose (mushroom) cellulose (plant walls)
What will happen if a person who is lactose intolerant eats milk?
This person is deficient in lactase - this is going to make lactase go through tract an led to osmotic diarrhea and co2 production from bacteria metabolising the lactose.
Carbohydrate metabolism pathways active in red blood cells
Glycolysis only - no mitochondria
Carbohydrate metabolism processes in brain
Glycolysis, TCA, ETC
Carbohydrate processes available to heart and skeletal muscle
Glycolysis, TCA, ETC, Glycogenolysis
Adipocytes
Conversion of glucose to fats
Hepatocytes
glycolysis, TCA, ETC, glycogenolysis, gluconeogenesis, pentose phosphate pathway
Glut2
Insulin independent transporter (liver)
High capacity, low affinity (almost never saturated)
Bidirectional
glut 4
insulin dependent transporter (low capacity, high affinity) - heart, skeletal muscle, adipocytes - not active in fasting states
SGLT1
will transport glucose or galactose with using sodium as a secondary active transport assistant
3 irreversible enzymes of glycolysis
hexokinase/glucokinase
phosphofructokinase 1
pyruvate kinase
Tissue localization: Hexokinase vs glucokinase
Hexokinase - everywhere
glucokinase - liver and pancreas technically
kinetic characteristics of hexokinase / glucokinase
Hexokinase - Low Km for glucose (constantly saturated)
Glucokinsae - High Km for glucose (rarely saturated)
Regulation of hexokinase / glucokinase
Hexokinase - constitutively active, constant amount, but allosterically regulated by its product, G6P
Glucokinase- shuttled between nucleus and cytosol for activity, F6P will suttle to nucleus and glucose brings to cytosol - this one is also inducible and will be induced by insulin to be synthesized
allosteric regulators of glucokinase and hexokinase
Hexokinase - allostericlally inhibited by glucose 6 phosphate
Glucokinase - allosterically activated by glucose, inactivated by fructose 6 phosphate
Allosteric regulation of phosphofuctokinase 1
Activators: F-2,6-BP, AMP, ADP (low energy, high glucose/ active PFK2)
Inhibitors: Citrate, ATP (high energy, glycolysis and TCA are going on)
Allosteric regulation of pyruvate kinase
Positive: F-1,6-BP (upstream)
Negative ATP, alanine
Covalent regulation of pyruvate kinase
Insulin –> dephosphorylated –> more active
Glucagon/ epinephrine –> phosphorylated –> less active