Glycogeneis

What is glycogenesis?

Synthesis of glycogen from glucose

What is the main storage form of glucose in animals?

Glycogen

What is the main storage form of glucose in plants?

Amylose and amylopectin

What type of linkage is found in amylose?

α(1→4) glycosidic bonds

What type of linkage forms branches in glycogen?

α(1→6) glycosidic bonds

How often does branching occur in glycogen?

Every 8-14 glucose residues

How often does branching occur in amylopectin?

Every 24-30 glucose residues

Which tissues store the most glycogen?

Liver and muscle

Approximate glycogen content of liver?

10% by weight

Approximate glycogen content of muscle?

1-2% by weight

Why is glycogen highly branched?

Rapid glucose release and storage

What happens to excess energy in the body?

Stored

What is the long-term energy storage form in animals?

Triacylglycerols

Which enzyme converts glucose to glucose-6-phosphate?

Hexokinase

What molecule donates phosphate in the hexokinase reaction?

ATP

What enzyme converts glucose-6-phosphate to glucose-1-phosphate?

Phosphoglucomutase

What enzyme forms UDP-glucose?

UDP-glucose pyrophosphorylase

What substrates form UDP-glucose?

Glucose-1-phosphate and UTP

What is the activated glucose donor in glycogenesis?

UDP-glucose

What byproduct is released when UDP-glucose is formed?

PPi

Which enzyme breaks down PPi?

Inorganic pyrophosphatase

Why is PPi hydrolysis important?

Drives reaction forward

Which enzyme elongates glycogen chains?

Glycogen synthase

What type of bond does glycogen synthase form?

α(1→4) glycosidic bond

Can glycogen synthase start glycogen synthesis alone?

No

What protein acts as primer for glycogen synthesis?

Glycogenin

Which amino acid residue on glycogenin binds glucose?

Tyrosine 194

How many glucose residues does glycogenin add to itself initially?

7 residues

What intrinsic activity does glycogenin possess?

Glucosyltransferase activity

Which enzyme creates branches in glycogen?

Branching enzyme

Another name for branching enzyme?

Amylo-(1,4→1,6)-transglycosylase

What does the branching enzyme transfer?

Segment of 7 residues

Minimum chain length needed for branching?

More than 11 residues

How far from another branch must a new branch be placed?

More than 4 residues away

What ion is required for glycogen synthase activity?

Mg²⁺

What pathway provides glucose-6-phosphate for glycogenesis?

Glycolysis

What intermediate links glycogenesis and nucleotide biosynthesis?

UTP

What is the role of ATP in glycogenesis?

Phosphorylates glucose

What is the role of UTP in glycogenesis?

Activates glucose

What is the function of glycogen in muscle?

Quick energy source

What is the function of glycogen in liver?

Maintain blood glucose

What are glucans?

Glucose polysaccharides

What are the end products of carbohydrate digestion?

Monosaccharides

Which monosaccharides are mentioned in the lecture?

Hexoses and pentoses

Which pathway releases energy from glucose?

Glycolysis

What is the HMP shunt also called?

Pentose phosphate pathway

What are proteins that catalyze reactions called?

Enzymes

What is the terminal electron acceptor in metabolism?

Oxygen

What are the major end products of aerobic metabolism?

CO₂ and H₂O

What is the energy currency of the cell?

ATP

Which nucleotide besides ATP is mentioned as energy source?

GTP

Why is glycogen better than free glucose for storage?

Less osmotic effect

What type of polymer is glycogen?

Highly branched glucose polymer

What linkage is broken during glycogenolysis?

α(1→4) bonds

What linkage requires debranching enzyme during glycogenolysis?

α(1→6) bonds

What enzyme deficiency causes Andersen disease?

Branching enzyme deficiency

What enzyme deficiency causes McArdle disease?

Muscle glycogen phosphorylase deficiency

What enzyme deficiency causes Von Gierke disease?

Glucose-6-phosphatase deficiency

What enzyme deficiency causes Hers disease?

Liver glycogen phosphorylase deficiency

What is the rate-limiting enzyme of glycogenesis?

Glycogen synthase

Which hormone stimulates glycogenesis?

Insulin

Which hormones inhibit glycogenesis?

Glucagon and epinephrine

What is the immediate precursor of glycogen?

UDP-glucose

Where does glycogenesis occur in the cell?

Cytosol

Why is glycogen synthesis important after meals?

Stores excess glucose

What kind of reaction forms glycogen?

Anabolic reaction