BIOL 2050U Lecture Notes - Protease, Hypoglycemia, Hydrolysis

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29 Jan 2013
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Control of Blood Glucose Concentration
The Factors which Influence Blood Glucose Concentration
Digestion of carbohydrates in diet
o Digestion → polysaccharide → glucose
o Fluctuation of glucose blood level depend on amount + type of carbohydrate eaten
Breakdown of glycogen
o Excess glucose → glycogen → glucose
o Storage polysaccharide made from excess glucose by glycogenesis
o Glycogen is abundant in liver + muscles
Conversion of non-carbohydrates to glucose by gluconeogenesis
Oxidation of glucose by respiration
o Glucose → ATP → energy
o Rate of respiration varies for different activities
o This affects glucose uptake from blood into cells
Brain is unable to store carbohydrates
o Lack of glucose in blood → no respiratory substrate → insufficient energy for
brain
o Short period of time already causes brain to malfunction
Normal glucose level in blood ≈90mg per 100cm²
After a meal it rarely exceeds 150mg per 100cm²
The Pancreas
Endocrine role is to produce hormones
Contains islets of Langerhans → sensitive to blood glucose conc
Islet cells contain
o α-cells → secrete glucagon and β-cells → secrete insulin
o capillaries into which hormones are secreted
o delta cells → produce hormone somatostatin → inhibits secretion of glucagon
Insulin mainly affects muscles, liver, adipose tissue
Exocrine role is to produce digestive enzymes
Active trypsin damages pancreas / digests proteins that make up pancreas / amylase leaks
into blood from damaged tissues / amylase conc in blood higher
High Blood Glucose Concentration
Detected by β-cells in islet of Langerhans (receptor) → secrete insulin
Increase in insulin secretion (corrective mechanism → effectors bring about a return to
norm)
o Speeds up rate of glucose uptake by cells from blood
Glucose enters cells by facilitated diffusion via glucose carrier proteins
Cells have vesicles with extra carrier molecules present in their cytoplasm
Insulin binds to receptor in plasma membrane
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