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BIOL 2P05 (128)
Lecture

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Department
Biology
Course
BIOL 2P05
Professor
John Mitterer
Semester
Fall

Description
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  Chemical signal → vesicles move towards plasma membrane  Vesicle fuses with membrane → increases glucose carrier proteins o Activates enzymes / Converts glucose to glycogen / Promotes fat synthesis Low Blood Glucose Concentration  Detected by α-cells in islets of Langerhans →
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