exam 3 pt 2 Flashcards
what enzymes are secreted by the pancreas for lipid digestion?
lipase & colipse
how are secretin & CCK involved in lipid digestion?
secretin: release stimulated by the acidic chyme & acts on the pancreas to cause the release of bicarbonate-rich pancreatic juice
CCK: release of bile from gallbladder & stimulated release of enzyme-rich pancreatic juice
how are various lipids absorbed?
hydrolysis of dietary fat in the lumen of the intestine followed by uptake of hydrolyzed products by enterocytes
describe the events that occur after the lipids have been absorbed into the enterocyte.
intracellular metabolism: formation of lipoproteins (chylomicrons)
what is the final product of lipid digestion? how does it enter circulation of the body?
free fatty acids are in the circulation bound in albumin (formed in adipose tissue)
what tissues utilize glucose?
all tissues metabolize glucose
what are the 3 transcription factors involved in glucose metabolism? how are they activated/regulated? what is their functions?
carbohydrate response element binding protein (ChREBP)
- activated by high glucose
- regulated by target genes
- strongly regulated glycolytic & lipogenic pathways
sterol regulatory element binding protein (SREBP)
- encoded by SREBP 1 & 2 gene
- functions: activates genes for cholesterol & fatty acid synthesis (1a), carbohydrate metabolism (1c), responds to cholesterol levels (2)
liver x receptors
- primary function: regulation of cholesterol metabolism
- activated by oxysterols
what are the different PPAR isoforms? what are they activated by? what is their functions?
a, B, y isoforms: molecular sensors for fat, protein, carb metabolism
activated by:
- polyunsaturated, branched chain, & oxidized fatty acids
- phospholipids
- other ligands & agonists
describe the differences in allosteric & covalent post-translation modifications.
allosteric: changes occur via interaction of enzyme with substrate, intermediate product, or actual products of the enzyme
covalent: involving changes directly on the enzyme, with the most common being phosphorylation of the enzyme
what are the 4 different hexokinase enzymes? where are there located? how are they activated/regulated? what are these functions?
hexokinase can supply tissues with glucose on the basis of need
- hexokinase 1: expressed in most tissues - not regulated in most tissues, G6P allosteric regulation
- hexokinase 2: many tissues: predominant in muscle, adipose, & heart - insulin-inducible, G6P allosteric regulation
- hexokinasae 3: bone marrow - insulin-inducible, G6P allosteric regulation
- glucokinase: liver, pancreas, brain - insulin-inducible, not allosterically regulated by G6P levels
how does glucokinase differ from the other hexokinase enzyme? how is it regulated?
not allostically regulated by G6P levels; regulated by insulin-inducible
adapted to regulate the supply of glucose
describe the process of glycogenesis? how is it related?
the conversion of glucose to glucose-6-phosphate (covalent modification)
under what conditions will glycogenesis occur?
glycogenolysis occurs during fasting &/ between meals in the liver
describe the insulin/glucagon signaling cascade & how it affects glycogen synthase & glycogen phosphorylase depending on the energy status in the body.
- can prompt the catabolism of glucose
- inhibits glycogen synthesis in the liver & activates a phosphate that leads to glycogen formation
how is calcium utilized in glycogen metabolism?
muscle contraction & activates actin/myosin interactions
