Forms Of Energy And The Fate Of Glucose Flashcards
What do animals need energy for?
Biological processes, movement, growth, production, reproduction
How do enzymes recognize substrates?
Electrostatic attractions
What happens after glucose is absorbed?
Stored as glycogen, oxidized for energy, fatty synthesis and storage
Why does the body use glycogen, if only 2-4% is used?
Since dietary glucose is sporadic and the synthesis is slow, it helps to speed up the process
What is glycogene used for?
Storage in skeletal muscle and liver and fuel reserve for ATP synthesis
What is glycogene made of?
Alpha1-4 and alpha1-6 linkages made from alpha-D-glucose
How is UTP used for glycogenesis?
Acts as a placeholder for ATP when it is transferred
What does UDP stand for?
Uridine diphosphate
What are the steps to glycogenesis?
- Glucose enters the cell through facilitated diffusion
- Glucose is phosphorylated by hexokinase and forms glucose-6-phosphate, which traps glucose in the cell
- G6P is isomerized by phosphoglucomutase and forms glucose-1-phosphate
- Phosphate group is transferred from C6 to C1
- UDP transfers UTP to G1P and forms UDP-glucose and PPi
- Glycogenin glucosylates a tyrosine residue and forms an alpha1-4 glycosidic bond
- Glycogen synthase and glycogen branching enzyme work together to transfer outer end of the chain to the alpha1-6 position on the neighboring chain
What are the steps of glycogenolysis?
- Glucagon and epinephrine bind to receptors on the cell surface which activates protein kinase A
- PKA phosphorylates and activates phosphorylase kinase
- PK activates glycogen phosphorylase
- GP acts on the alpha1-4 glycosidic bond and removes the glucose residues from glucose-1-phosphate
- Glucan transferase relocates residues to the branch point, this generates a non-reducing end and exposes the branch point
- Glycogen debranching enzyme hydrolyses the alpha1-6 glycosidic bond and releases glucose
What happens to G6P once it is isomerized?
- G6P is transported to the ER by G6P translocase
- G6P dephosphorylates and produces glucose
- Hepatocytes release glycogen derived glucose into circulation to maintain blood-glucose levels
- Muscle cells trap G6P molecules to use for later
What is type 1 diabetes?
Pancreatic b-cells are destroyed and so do not produce enough insulin
Mainly dogs
What is type 2 diabetes?
Insulin production is reduced or resistant
Usually cats
How is glucose metabolism regulated in the strained muscle?
Insulin increases glycogenesis, glycolysis, and protein synthesis
Decreases proteolysis
How is glucose metabolism regulated in adipose tissue?
Insulin increases TAG formation and storage
Decreases lipolysis
How is glucose metabolism regulated in the liver?
Insulin increases glycogenesis, glycolysis, and carbohydrate usage
Decreases glycogenolysis and ketogenesis
Glucagon increases glucose synthesis and ketogenesis
What are the three requirements that need to happen before glycogenolysis can occur?
- Glycogen synthase makes an a1-4 link with G1P
- Have elongated existing chains
- Must have glycogen fragments to serve as primers
