Carbohydrate Structure & Nomenclature

FSHN 3600

Simple Sugars

Maltose is ___ & ___ bonded in alpha 1,4 linkage.

glucose, glucose

Simple Sugars

Maltose is hydrolyzed by ___.

maltase

Simple Sugars

Lactose is ___ & ___ bonded in beta 1,4 linkage.

glucose, galactose

Simple Sugars

Sucrose is ___ & ___ bonded in alpha 1,4 linkage.

glucose, fructose

Simple Sugars

Sucrose is hydrolyzed by ___.

sucrase

Simple Sugars

What type of reaction forms a bond between 2 monosaccharides?

Condensation/dehydration reaction

• removal of H atom from 1 monosaccharide and removal of OH group from another

Complex CHOs

Describe the monosaccharides, linkages, and which enzyme hydrolyzes each polysaccharide.

Cellulose:

Glucose monosaccharides bonded in a beta 1,4 linkage.

No enzymes to digest cellulose (dietary fiber)

Complex CHOs

Describe the monosaccharides, linkages, and which enzyme hydrolyzes each polysaccharide.

Amylose:

Linear chains of glucose monosaccharides bonded in alpha 1,4 linkage.

Hydrolyzed by amylase

Complex CHOs

Describe the monosaccharides, linkages, and which enzyme hydrolyzes each polysaccharide.

Amylopectin:

Branched and linear chains of glucose monosaccharides bonded in alpha 1,6 & 1,4 linkages. 

Hydrolyzed by gamma-glucosidase (alpha 1,6) & amylase (alpha 1,4)

Glucose Transporters

Describe SGLT1 function & location.

Transports glucose from GI lumen into enterocyte.

Glucose Transporters

SGLT1 requires ___ and displays ___ kinetics. 

energy, saturation

Glucose Transporters

Describe GLUT2 function and location

Bidirectional transporter of glucose in basolateral membrane of enterocytes and liver. 

Glucose Transporters

Describe GLUT2 function and location.

Blood brain barrier, RBCs, fetal tissue

Glucose Transporters

Describe GLUT3 function and location:

Neurons

Glucose Transporters

GLUT1 & GLUT3 have a ___ Km (high affinity)

low

Glucose Transporters

Describe GLUT4 function and location.

Muscle, adipose

Glucose Transporters

GLUT4 is ___-dependent

insulin

Glucose Transporters

Describe GLUT5 function and location.

Transports fructose in enterocyte.

Monosaccharide Absorption

What is 1)?

What does it do?

SGLT1

a symport for sodium and glucose. Uses indirect energy from ATP. A form of active transport.

Monosaccharide Absorption

What is 2)?

What does it do?

GLUT5

transports fructose and uses facilitated diffusion.

Monosaccharide Absorption

What is 3)?

What does it do?

Na/K ATPase

an antiport for sodium and potassium, uses ATP.

Monosaccharide Absorption

What is 4)?

What does it do?

GLUT2

transports glucose down a concentration gradient via facilitated diffusion.

Hepatic Metabolism of Glucose

What are the 3 fates of glucose upon entering the liver?

1. Metabolized for energy

2. Storage (as glycogen)

3. Synthesis of ribose (hexose monophosphate shunt

Glycogenesis is the conversion of glucose to ___ in a ___ state. This occurs in the ___ and muscles. Glucose is converted to ____, which is added to an existing glycogen chain to become a longer chain of glycogen. In the liver, ___ adds a P group to glucose so now it’s glucose-6-phosphate. In the muscle, ___ accomplishes this step.

glycogen

fed

liver

UDP-glucose

glucokinase

hexokinase

Glycogenolysis is the conversion of ____ to glucose in the liver or glycogen into ___-___-___ in muscle tissues during a ___ state. When glycogen is broken down into glucose in the liver, the glucose can be used to ___ blood glucose levels and be used by other ___ in the body. This is the ___ action of glycogenesis. Glucose-6-phosphate is only present in the ___.

glycogen

glucose-6-phosphate

fasted

raise

cells

reverse

liver

Key differences in glycogenesis in the liver and muscle:

Liver — glucokinase

Muscle — hexokinase

Key differences in glycogenolysis in the liver and muscle:

Liver

• Glc-6-P allows glycogen to be converted back to glc

• Glucagon is the signal in a fasted state

Muscle

• No glc-6-P — glycogen can only be converted glc-6-P and sent through glycolysis

• Epinephrine is the signal in the fasted state

• Hexokinase is allosterically inhibited by glc-6-P

Is the phosphrylation of glucose and example of PTM? Why/why not?

No, because glucose is NOT a protein.