Biochemistry
Study Guide
Authored by a Biochemistry Professor
ADVANCED CARBOHYDRATE
METABOLISM
A High-Yield Guide to GAGs, Glycoproteins, and Monosaccharide
Disorders
,Author: Assoc. Prof. Dr Zeynep Caliskan, Department of Medical
Biochemistry
Copyright © 2025 The Curious Biochemist. 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.
Contents
Glycosaminoglycans and Proteoglycans ............. Page 3
Glycoproteins ................................................................... Page 10
Metabolism of Mono- /Di-saccharides ...................... Page 12
, 3
GLYCOSAMINOGLYCANS (GAGS)
AND PROTEOGLYCANS
GLYCOSAMINOGLYCANS
Glycosaminoglycans are large, typically negatively charged heteropolysaccharide chains.
They are crucial for maintaining the stability of tissue cells and fibrous components, and
for regulating the body's water and salt balance. GAGs also provide the viscous,
lubricating properties of mucous secretions and synovial fluid.
STRUCTURE
GAGs are long heteropolysaccharide
chains made of repeating disaccharide PROPERTIES & FUNCTIONS
units, typically consisting of an acid
Their strong negative charge causes
sugar and an amino sugar.
GAGs to extend in an aqueous
◦ Amino sugars are usually D-
environment, repelling each other and
glucosamine or D-galactosamine.
creating a hydrated layer of water
◦ Acidic sugars are D-glucuronic
around them. When pressure is applied,
acid or L-iduronic acid, with the
they slide away, providing the
exception of keratan, which contains
lubricating viscosity of mucous
galactose instead of an acidic sugar.
secretions and synovial fluid. They
◦ These sugars, along with carboxyl
rapidly regain their original volume
and sulfate groups, confer a strong
when pressure is removed, contributing
negative charge to GAGs at
to the elasticity of synovial fluid and
physiological pH.
the aqueous humor of the eye.
TYPES Chondroitin Hyaluronic
sulfate acid
There are six main types of GAG
monomers based on their glycosidic Keratan GAGs Heparan
bond type and sulfate units sulfate sulfate
Dermatan
Heparin
sulfate
SULFATE SOURCE
The sulfate units in GAGs originate from phosphoadenosyl phosphosulfate (PAPS),
which are active sulfur units.
Study Guide
Authored by a Biochemistry Professor
ADVANCED CARBOHYDRATE
METABOLISM
A High-Yield Guide to GAGs, Glycoproteins, and Monosaccharide
Disorders
,Author: Assoc. Prof. Dr Zeynep Caliskan, Department of Medical
Biochemistry
Copyright © 2025 The Curious Biochemist. 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.
Contents
Glycosaminoglycans and Proteoglycans ............. Page 3
Glycoproteins ................................................................... Page 10
Metabolism of Mono- /Di-saccharides ...................... Page 12
, 3
GLYCOSAMINOGLYCANS (GAGS)
AND PROTEOGLYCANS
GLYCOSAMINOGLYCANS
Glycosaminoglycans are large, typically negatively charged heteropolysaccharide chains.
They are crucial for maintaining the stability of tissue cells and fibrous components, and
for regulating the body's water and salt balance. GAGs also provide the viscous,
lubricating properties of mucous secretions and synovial fluid.
STRUCTURE
GAGs are long heteropolysaccharide
chains made of repeating disaccharide PROPERTIES & FUNCTIONS
units, typically consisting of an acid
Their strong negative charge causes
sugar and an amino sugar.
GAGs to extend in an aqueous
◦ Amino sugars are usually D-
environment, repelling each other and
glucosamine or D-galactosamine.
creating a hydrated layer of water
◦ Acidic sugars are D-glucuronic
around them. When pressure is applied,
acid or L-iduronic acid, with the
they slide away, providing the
exception of keratan, which contains
lubricating viscosity of mucous
galactose instead of an acidic sugar.
secretions and synovial fluid. They
◦ These sugars, along with carboxyl
rapidly regain their original volume
and sulfate groups, confer a strong
when pressure is removed, contributing
negative charge to GAGs at
to the elasticity of synovial fluid and
physiological pH.
the aqueous humor of the eye.
TYPES Chondroitin Hyaluronic
sulfate acid
There are six main types of GAG
monomers based on their glycosidic Keratan GAGs Heparan
bond type and sulfate units sulfate sulfate
Dermatan
Heparin
sulfate
SULFATE SOURCE
The sulfate units in GAGs originate from phosphoadenosyl phosphosulfate (PAPS),
which are active sulfur units.
