Biochemistry
Study Guide
Authored by a Biochemistry Professor
GLUCOSE HOMEOSTASIS AND
DIABETES MELLITUS
,High-Yield Biochemistry Study Guide
For Doctors and Medical Students
Author: Assoc. Prof. Dr Zeynep Caliskan, Department of Medical
Biochemistry
Copyright © 2025
This book was prepared by Assoc. Prof. Dr Zeynep Caliskan. All
rights reserved. No part of this publication may be reproduced,
distributed, or transmitted in any form or by any means, electronic
or mechanical, including photocopying, recording, or by any
information storage and retrieval system, without the prior written
permission of the author.
Disclaimer
This study guide has been prepared solely for educational and
academic purposes. The content is based on standard medical
textbooks and is not intended to replace clinical judgment or
professional medical advice. Students are advised to consult
qualified healthcare professionals in real clinical settings.
Acknowledgement
I would like to express my gratitude to my colleagues, fellow
academics, and especially my students, whose curiosity and
dedication to learning have been a constant source of motivation.
, T A B L E O F
Contents
Overview of Energy Substrates and 1
Metabolism
Hormonal Regulation of Fuel 2
Metabolism
Fed-Fast Cycle 5
Diabetes Mellitus 7
Hipoglycemia 21
Multiple Choice questions 23
Active Recall Summary 28
, Overview of Energy
Substrates and Metabolism
Key Energy Substrates
Glucose: Primary fuel for the brain, preferred for initial stages of muscle
exercise. Stored as glycogen in the liver (75g) and muscle (400g).
Fatty Acids: Stored as triacylglycerols in adipose tissue with virtually
unlimited capacity. Used for energy during prolonged fasting and
exercise
Amino Acids: Primarily for protein synthesis, but can be
converted to glucose during prolonged fasting or metabolic
stress.
Glucose Homeostasis Mechanisms
Glycogenolysis: Breakdown of glycogen to
release glucose into circulation.
Gluconeogenesis: Synthesis of glucose
from noncarbohydrate compounds
(lactate, alanine, glycerol). Occurs mostly
in the liver, with kidney contribution during
prolonged fast.
Insulin: Anabolic hormone, decreases
plasma glucose. Promotes storage of
carbohydrates and lipids, and protein
synthesis. Suppresses catabolic pathways.
Glucagon: Catabolic hormone, increases plasma glucose. Mobilizes fuel reserves by
stimulating glycogenolysis and gluconeogenesis. Opposes insulin's effects.
Counterregulatory Hormones: Glucagon, catecholamines (epinephrine), cortisol, growth
hormone. All increase plasma glucose.
1
Study Guide
Authored by a Biochemistry Professor
GLUCOSE HOMEOSTASIS AND
DIABETES MELLITUS
,High-Yield Biochemistry Study Guide
For Doctors and Medical Students
Author: Assoc. Prof. Dr Zeynep Caliskan, Department of Medical
Biochemistry
Copyright © 2025
This book was prepared by Assoc. Prof. Dr Zeynep Caliskan. All
rights reserved. No part of this publication may be reproduced,
distributed, or transmitted in any form or by any means, electronic
or mechanical, including photocopying, recording, or by any
information storage and retrieval system, without the prior written
permission of the author.
Disclaimer
This study guide has been prepared solely for educational and
academic purposes. The content is based on standard medical
textbooks and is not intended to replace clinical judgment or
professional medical advice. Students are advised to consult
qualified healthcare professionals in real clinical settings.
Acknowledgement
I would like to express my gratitude to my colleagues, fellow
academics, and especially my students, whose curiosity and
dedication to learning have been a constant source of motivation.
, T A B L E O F
Contents
Overview of Energy Substrates and 1
Metabolism
Hormonal Regulation of Fuel 2
Metabolism
Fed-Fast Cycle 5
Diabetes Mellitus 7
Hipoglycemia 21
Multiple Choice questions 23
Active Recall Summary 28
, Overview of Energy
Substrates and Metabolism
Key Energy Substrates
Glucose: Primary fuel for the brain, preferred for initial stages of muscle
exercise. Stored as glycogen in the liver (75g) and muscle (400g).
Fatty Acids: Stored as triacylglycerols in adipose tissue with virtually
unlimited capacity. Used for energy during prolonged fasting and
exercise
Amino Acids: Primarily for protein synthesis, but can be
converted to glucose during prolonged fasting or metabolic
stress.
Glucose Homeostasis Mechanisms
Glycogenolysis: Breakdown of glycogen to
release glucose into circulation.
Gluconeogenesis: Synthesis of glucose
from noncarbohydrate compounds
(lactate, alanine, glycerol). Occurs mostly
in the liver, with kidney contribution during
prolonged fast.
Insulin: Anabolic hormone, decreases
plasma glucose. Promotes storage of
carbohydrates and lipids, and protein
synthesis. Suppresses catabolic pathways.
Glucagon: Catabolic hormone, increases plasma glucose. Mobilizes fuel reserves by
stimulating glycogenolysis and gluconeogenesis. Opposes insulin's effects.
Counterregulatory Hormones: Glucagon, catecholamines (epinephrine), cortisol, growth
hormone. All increase plasma glucose.
1
