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DIP Episode 11 - Glycogen and Lysosomal Storage Diseases

BiochemistryMedium4 - HighHas Q&A

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Topic

Glycogen storage diseases (GSDs); Lysosomal storage diseases (LSDs); Glycogen metabolism pathways.

Key Takeaway

Understanding the specific enzymes and subcellular locations involved in glycogen synthesis, breakdown, and glucose release is critical for diagnosing metabolic disorders like GSDs.

Runtime: 37.7 min

Published: 2018-03-27

Completed audio: Yes

Completed notes: Yes

Anki made: Yes

Section: BIOCHEMISTRY

Open Notion notes Episode source

Episode Notes

Source / episode info

Episode: 11
Title: Divine Intervention Episode 11-Glycogen and Lysosomal Storage Diseases.
Published: 2018-03-27
Source: Episode page

One-liner

This episode reviews the complex biochemistry of glycogen metabolism, detailing the roles of hexokinase/glucokinase, glycogen synthase, branching enzyme, glycogen phosphorylase, and phosphoglucomutase in both synthesis and breakdown, while also introducing the concept of lysosomal storage diseases.

High-yield summary

Glycogen Synthesis: Glucose G6 P (Hexokinase/Glucokinase) UDP-glucose Glycogen polymer (Glycogen Synthase). Branching occurs via Branching Enzyme, creating 1 6 linkages.
Glucose Release Trap: The conversion of Glucose-6-Phosphate (G6 P) to free glucose only occurs in the liver, utilizing specialized enzymes located in the endoplasmic reticulum (ER), allowing the liver to raise blood glucose levels during fasting. Muscle lacks this capability.
Glycogen Breakdown: 1 4 bonds are cleaved by Glycogen Phosphorylase (releasing Glucose-1-Phosphate, G1 P). The 1 6 branches require the action of the Deep Branching Enzyme.
Deep Branching Enzyme: This bifunctional enzyme is crucial for breaking branch points. Its 1 6 glucosidase acetylase subunit directly cleaves free glucose from the branch point, bypassing the need to convert G1 P G6 P first.
Lysosomal Storage Diseases (LS Ds): These are generally more memorization-based; diagnosis relies on identifying the specific accumulated substrate and organ system involvement.

Learning objectives

Describe the enzymatic steps involved in glycogen synthesis and degradation.
Differentiate between the roles of hexokinase, glucokinase, and glycogen synthase in glucose metabolism.
Identify the unique function and location of Glucose-6-phosphatase in maintaining blood glucose homeostasis.
Recognize the general pathophysiology and key features of major Lysosomal Storage Diseases (LS Ds).
Understand the structural importance of \alpha 1 -> 4 versus \alpha 1 -> 6 linkages in glycogen.

Board exam buzzwords

Condition	Key Finding	Association	Board Exam Tip
Glycogen Storage Disease (GSD)	Hypoglycemia, Hepatomegaly	Defect in G6 P release or synthesis	Always consider the liver's role in maintaining blood glucose; defects here cause fasting hypoglycemia.
Lysosomal Storage Diseases (LS Ds)	Accumulation of undigested substrates	Impaired lysosomal hydrolases	Think "storage" = buildup; often affects neurons and reticuloendothelial system.
Glycogen Synthase	Synthesis of 1 4 linkages	Fed state, high glucose load	Deficiency impairs the ability to store excess glucose as glycogen.
Deep Branching Enzyme	Cleavage of 1 6 branch points	Bifunctional enzyme activity	This is a highly specific structural defect that impacts both synthesis and breakdown efficiency.

Rapid review table

Topic	Key Point	Context	Exam Relevance
Glycogen Synthesis	G6 P UDP-glucose Glycogen	Fed state, high glucose availability	Requires insulin signaling; liver/muscle storage.
GS Ds (Liver)	Hypoglycemia upon fasting	Defect in Glucose-6-phosphatase	The most common and clinically significant GSD type due to failure of blood glucose release.
Deep Branching Enzyme	Cleaves 1 6 linkages; releases free glucose	Bifunctional enzyme activity	Crucial for efficient glycogen structure and breakdown, a high-yield structural point.
LS Ds	Accumulation within lysosomes	Defective hydrolase enzymes	Diagnosis requires identifying the specific accumulated substrate (e.g., gangliosides).

Board-speak -> diagnosis

Board-speak / Vignette phrase	Diagnosis / Concept	Why it fits
A patient presents with hypoglycemia, hepatomegaly, and lactic acidosis following fasting, due to a defect in glycogen breakdown.	Glycogen Storage Disease (GSD) Type I (e.g., Glucose-6-Phosphatase Deficiency)	The inability to convert G6 P to free glucose prevents the liver from releasing stored energy into the bloodstream.
A metabolic disorder characterized by the accumulation of undigested material within lysosomes, leading to progressive organ failure.	Lysosomal Storage Disease (LSD)	LS Ds are defined by impaired lysosomal degradation pathways, causing substrate buildup in cellular organelles.
Deficiency of the enzyme responsible for cleaving 1 6 linkages at branch points, resulting in abnormal glycogen structure.	Deep Branching Enzyme deficiency	This specific defect impairs the structural integrity and efficient breakdown of glycogen polymers.
A patient presents with muscle weakness and myopathy due to impaired energy storage and utilization within skeletal muscle cells.	Glycogen Storage Disease (GSD) Type V (McArdle disease, affecting muscle phosphorylase)	Muscle-specific defects impair local energy supply, leading to exercise intolerance without systemic hypoglycemia.
A patient develops progressive neurological decline and hepatosplenomegaly due to the accumulation of gangliosides in lysosomes.	Lysosomal Storage Disease (e.g., Tay-Sachs disease)	The buildup of specific macromolecules within lysosomes is the hallmark pathology of LS Ds.

Differential diagnosis / distinguishing features

Lysosomal Storage Diseases (LS Ds)

Key Features	Distinguishing Findings	Next Step
Tay-Sachs Disease	Accumulation of GM2 gangliosides; progressive neurodegeneration.	Positive Hexosaminidase A assay in leukocytes/skin fibroblasts.
Niemann-Pick Disease	Accumulation of sphingomyelin; hepatosplenomegaly, foam cells (lipid storage).	Measurement of specific lipid substrates in affected organs.
Mucopolysaccharidoses (MPS)	Accumulation of glycosaminoglycans (GA Gs); skeletal dysplasia, coarse facies.	Urine analysis for elevated GA Gs (e.g., Dermatan sulfate).

Management pearls

For suspected GS Ds, initial management involves preventing hypoglycemia through frequent carbohydrate feeding and avoiding prolonged fasting.
LS Ds often require enzyme replacement therapy (ERT) or substrate reduction therapy (SRT), depending on the specific deficiency.
In cases of severe metabolic crisis due to glycogen accumulation, supportive care (IV dextrose, managing acidosis/electrolytes) is paramount.

Don't miss

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Liver vs Muscle: The ability to convert G6 P -> free glucose via Glucose-6-phosphatase is restricted only to the liver. This is a critical distinction for understanding hypoglycemia in different types of metabolic disorders.

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Deep Branching Enzyme Function: Remember that this enzyme not only helps synthesize but also efficiently breaks down glycogen by cleaving the branch points, releasing free glucose directly.

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LSD Diagnosis: The diagnosis relies on identifying the specific accumulated substrate (e.g., GM2 gangliosides for Tay-Sachs) and confirming impaired lysosomal function.

Integration & clinical reasoning

Biochemistry/Pathophysiology Integration: GS Ds represent a failure of metabolic catabolism, while LS Ds represent a failure of cellular degradation (lysosomes). Both result in the accumulation of macromolecules, but through different pathways.
Clinical Correlation: The clinical presentation often dictates the type of storage disorder; neurological symptoms suggest lysosomal defects (LS Ds), whereas profound fasting hypoglycemia suggests G6 P release defects (GS Ds).

Concept connections / cross-references

No explicit cross-references.

High-yield association table

Condition	Association	Mechanism	Clinical Significance
Glycogen Synthesis	UDP-glucose formation	Requires Glucose-1-Phosphate and UTP; catalyzed by UDP-glucose pyrophosphorylase.	Defects here impair the entire process of glycogen storage, leading to hypoglycemia.
GSD Type I	Hypoglycemia/Hepatomegaly	Deficiency of Glucose-6-phosphatase (G6 P glucose) in the ER.	The most common cause of fasting hypoglycemia; diagnosis is key for metabolic screening.
Deep Branching Enzyme	Cleavage of 1 6 linkages	Bifunctional enzyme activity releasing free glucose directly from branch points.	Essential for maintaining proper glycogen structure and efficient breakdown kinetics.
Lysosomal Storage Diseases (LS Ds)	Accumulation of undigested substrates	Defective lysosomal hydrolases (e.g., Hexosaminidase A).	Leads to progressive, multi-system failure affecting the nervous system and reticuloendothelial system.

Key terms glossary

Term	Definition	Context	Example
Glycogen Synthase	Enzyme that catalyzes the formation of 1 4 glycosidic bonds between glucose units.	Glycogen synthesis (anabolism).	Converts UDP-glucose into a growing glycogen chain.
Phosphoglucomutase	Enzyme that interconverts Glucose-1-Phosphate and Glucose-6-Phosphate.	Both synthesis and breakdown pathways.	Necessary step to move from G1 P (from phosphorylase) back to G6 P for glucose release.
Deep Branching Enzyme	Bifunctional enzyme responsible for cleaving 1 6 linkages at branch points.	Glycogen structure/breakdown.	Ensures the glycogen polymer remains soluble and accessible for degradation.
Lysosomal Storage Disease (LSD)	A group of metabolic disorders caused by the inability to break down specific macromolecules within lysosomes.	Pathophysiology; diagnosis based on accumulated substrate.	Tay-Sachs disease (accumulation of GM2 gangliosides).

Study optimization

Topic	Study Approach	Priority	Resources
Glycogen Metabolism	Pathway mapping and enzyme function review.	High (Step 1/2)	Reviewing the specific roles of G6 P, UDP-glucose, and the three key enzymes (Synthase, Phosphorylase, Branching Enzyme).
GS Ds vs LS Ds	Comparative analysis of metabolic failure types.	Medium (Conceptual)	Focus on where the defect occurs: cytoplasmic/ER (GS Ds) vs. lysosome (LS Ds).
Lysosomal Storage Diseases	Memorization of specific substrates and associated enzymes.	High (Step 1/2)	Use mnemonics or flowcharts to link the accumulated substrate (e.g., GM2 gangliosides Tay-Sachs).

Question pattern recognition

Metabolic pathway failure leading to systemic symptoms (Hypoglycemia, organomegaly).
Differentiation between storage defects in different organelles (Cytosol vs. Lysosome).
Understanding enzyme function and the consequences of deficiency on metabolic flux.

Test yourself

Common mistakes to avoid

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Mistake 1: Confusing GS Ds and LS Ds. Remember that GS Ds are defects in cytoplasmic metabolism (glycogen breakdown/synthesis), while LS Ds are defects in lysosomal degradation.

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Mistake 2: Assuming all metabolic disorders cause hypoglycemia. While many GS Ds do, not all storage diseases present with profound fasting hypoglycemia; the specific enzyme defect determines the clinical picture.

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Mistake 3: Overlooking the Deep Branching Enzyme's role. Do not forget that this enzyme is critical for both structure and efficient breakdown by releasing free glucose directly from branch points.

Common traps

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Trap 1 (Location): Assuming all G6 P -> Glucose conversions happen in the cytosol. Correction: This crucial step must occur in the ER of liver cells to prevent a futile cycle.

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Trap 2 (Muscle vs Liver): Believing that muscle can raise blood glucose levels during fasting. Correction: Muscle lacks Glucose-6-phosphatase and cannot release free glucose into circulation.

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Trap 3 (LSD Diagnosis): Assuming all LS Ds are caused by a single enzyme deficiency. Correction: The key is identifying the specific accumulated substrate (e.g., sphingomyelin, GM2 gangliosides) to narrow down the diagnosis.

Original transcript with highlights

Okay, welcome to the 11th episode of the Divine Intervention Podcasts. My name is Divine. I am a fourth-year medical student and I am happy to discuss some biochem stuff today. Basically, a discussion today will include the glycogen storage diseases and the lysosomal storage diseases. These are things that are incredibly annoying to learn but they are very high yield for many exams. They do shop on Step 1, they certainly shop on Step 2 C cable if it or not. And they also show up on the Pediatrics shelf exam. So it's something you definitely want to know. The glycogen storage diseases, I feel that they are essentially an exercise in logic reasoning. The lysosomal storage diseases less so, they are mostly more memorization. But I will say that for the LS Ds, I'm not referring to the drug LSD, don't think about that, that's bad thinking. The LS Ds, lysosomal storage diseases, that's how I'm going to refer to them. The glycogen storage diseases are referred to them as GS Ds. The LS Ds are more memorization based but there are a few key things you want to know about each one that should help you spot it on the exam. So let's jump right into it. So the glycogen storage diseases. Before we jump into the diseases, I believe it's worthwhile to have a very quick review of glycogen metabolism. So we all know that glycogen is a storage form of glucose. And they're two high-yield organs in general that help with storing glucose as glycogen. They'll be liver and muscle. Liver and muscle.

Now, how do we make glycogen? We obviously make glycogen in a fed state. When you have surplus money in the bank, I mean when you have surplus money coming in like you have a very high salary or whatever. Then you can begin to think of making some kind of savings and sucking away some money in the bank. That's what happens when you're in a fed state, you have a ton of glucose around. You don't know what to do with all that glucose. The next thing you do is to begin to store it as glycogen. So the thing that happens is glucose gets into the cell and it's phosphorylithic by hexokinase if you're essentially everywhere else in the body or glucose kinase if you're in the liver or you're in the beta cells of the pancreas. So you have phosphorylation of glucose to glucose six phosphate that glucose six phosphate is trapped in the cell. And remember that glucose kinase is induced by insulin if we're dealing with the liver in this case. So you form glucose six phosphate that glucose six phosphate by some magic becomes UDP glucose and then glycogen synthase helps us convert that UDP glucose to glycogen polymers. And those glycogen polymers have alpha one for linkages. But if you're remembering from your med school biochemistry course, glycogen does not just contain the linear alpha one for linkages. It also contains branched alpha one six linkages. Those alpha one for linkages via the linear bonds those are made by glycogen synthase.

Those alpha one six branches are made by what enzyme do you think? Branching enzyme branching enzyme. So branching enzyme helps you make the alpha one six linkages. And again remember the alpha one six linkages are only found at the branch point only found at the branch point. And basically at each branch point you have an alpha one six linkage and then after that you have alpha one for alpha one for alpha one for alpha one for alpha one for alpha one for. So that's how you make glycogen now. Do you break down glycogen pretty straightforward as well? We said that there are two kinds of bonds the alpha one for linkages and there are for one six linkages to break the alpha one for linkages down we use an enzyme known as glycogen phosphorelease glycogen phosphorelease breaks bonds. It converts basically breaks the alpha one for linkages in glycogen it makes glucose one phosphate some extremely low yield enzyme force for glucose mute is converts the glucose one phosphate to glucose six phosphate. And then that glucose six phosphate is converted to free glucose and remember that that G6 P to glucose conversion happens in the endoplasmic reticulum that's a kind of a special regulation because remember the conversion of glucose to glucose six phosphate which is the reverse reaction of that occurs in the cytosol under the action of glucose or hexokinase.

You don't want to maintain a futile cycle so you try to spatially regulate it that's when the endoplasmic reticulum you express glucose six phosphaties and it helps you convert glucose six phosphate to free glucose. Now here's one important thing you need to remember this glucose six phosphate to glucose reaction occurs only in the liver it does not occur in muscle. Muscle does not have glucose six phosphaties the job of muscle is not to raise blood glucose levels in the setting of a fast so that is something you definitely definitely definitely want to keep in mind. Muscle can perform glycogen glycogen or lysis but its job is not to raise blood glucose levels unlike the liver very important. So we've talked about how you break down the alpha one for linkages with glycogen phosphorylase to break down the alpha one six linkages think about it if forming those alpha one six linkages required branching enzymes branching enzyme what will be required to break those alpha one six linkages that will be the deep branching enzyme the deep branching enzyme. Now the thing is the deep branching enzyme is one of two high yield bifunctional enzymes you want to know in biochemistry the first one is the combo of phosphofructokinase two and fructose two six base phosphaties this is the second one.

Deep branching enzyme is a bifunctional enzyme that has two basically two subunits one subunit is known as alpha one six glucose side ace the second subunit is known as four alpha D glucano transferase. So alpha one six glucose side ace what it does is it breaks the branching bond and releases free glucose so notice a very important point here I said that in breaking the one for linkages in glycogen right you split those off if I'm glucose one phosphate it's converted to glucose six phosphate and then glucose six phosphaties helps you go from glucose six phosphate to free glucose. The alpha one six glucose side ace part of deep branching enzyme directly splits off free glucose from the glycogen polymer at the branch point very very high to know that.

Now the second part the for alpha D glucano transferase basically the way it works is when glycogen for four release has chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop chop

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Practice questions — USMLE style

Question 1 — Biochemistry/Physiology

A 30-year-old man presents to the emergency department with severe hypoglycemia following a period of fasting, accompanied by lactic acidosis and elevated lactate levels. Laboratory testing reveals markedly elevated glucose-6-phosphate (G6 P) in his blood. The physician suspects a defect in the ability to convert G6 P into free glucose. Which enzyme is most likely deficient in this patient, leading to impaired hepatic gluconeogenesis and glycogenolysis?

A) Hexokinase
B) Glycogen Synthase
C) Phosphoglucomutase
D) Glucose-6-phosphatase
E) Branching Enzyme

Answer: D. The inability to convert glucose-6-phosphate (G6 P) into free glucose is the hallmark of defects in glucose-6-phosphatase. This enzyme, located in the endoplasmic reticulum, is crucial for releasing stored glucose from both glycogen and gluconeogenesis products into the bloodstream. Deficiency leads to severe hypoglycemia and accumulation of G6 P derivatives. Hexokinase (A) traps glucose but does not release it; Glycogen Synthase (B) builds glycogen; Phosphoglucomutase (C) interconverts G1 P and G6 P, but Glucose-6-phosphatase is the rate-limiting step for free glucose release in the liver.

Question 2 — Biochemistry/Enzymology

Glycogen is a highly branched polysaccharide composed of linear $\alpha 1 \rightarrow 4$ linkages and branch points containing $\alpha 1 \rightarrow 6$ linkages. The breakdown of these complex structures requires specific enzymes to cleave both types of bonds. Which enzyme is responsible for specifically hydrolyzing the $\alpha 1 \rightarrow 6$ glycosidic bonds at the branch points, releasing free glucose molecules directly from the glycogen polymer?

A) Glycogen Phosphorylase
B) Glucose-1-phosphate Uridylyltransferase
C) Branching Enzyme
D) Deep Branching Enzyme (specifically the $\alpha 1 \rightarrow 6$ glucosidase subunit)
E) Hexokinase

Answer: D. While the general breakdown of linear bonds uses Glycogen Phosphorylase (A), and the overall process involves multiple enzymes, the specific enzyme complex responsible for cleaving the branch points ($\alpha 1 \rightarrow 6$) and releasing free glucose is the Deep Branching Enzyme. This enzyme is a bifunctional protein containing an $\alpha 1 \rightarrow 6$ glucosidase subunit that directly hydrolyzes these bonds to release free glucose.

Question 3 — Biochemistry/Metabolic Regulation

A patient with chronic liver failure presents with signs of metabolic distress. Biochemical analysis reveals impaired ability to mobilize stored glucose, despite normal muscle function. The physician notes that the primary site for converting G6 P into free glucose is compromised. Which statement accurately describes the physiological difference between glycogen breakdown in the liver versus skeletal muscle?

A) Skeletal muscle relies solely on hexokinase for initial glucose phosphorylation, whereas the liver uses glucokinase.
B) Both tissues utilize Glucose-6-phosphatase to raise blood glucose levels during fasting.
C) The endoplasmic reticulum is required for G6 P conversion to free glucose in both liver and muscle.
D) Only the liver possesses the necessary machinery (Glucose-6-phosphatase) to release stored glucose into circulation, preventing hypoglycemia during fasting.
E) Muscle glycogen breakdown proceeds via a pathway that bypasses phosphoglucomutase entirely.

Answer: D. The critical difference is the presence of Glucose-6-phosphatase in the liver but its absence in skeletal muscle. This restriction ensures that muscle can use its stored glucose for local energy needs (e.g., during exercise) but cannot contribute to maintaining systemic blood glucose levels, which is a vital function reserved for the liver.

Question 4 — Biochemistry/Enzyme Function

The process of synthesizing glycogen involves two key enzymatic steps: forming linear $\alpha 1 \rightarrow 4$ linkages and creating branched $\alpha 1 \rightarrow 6$ linkages. The enzyme responsible for generating these branch points is crucial for maintaining the highly compact, storage structure of glycogen. Which metabolic step requires the action of the Branching Enzyme?

A) Phosphorylation of glucose to trap it within the cell.
B) Conversion of UDP-glucose into a polymer chain by Glycogen Synthase.
C) Cleavage of $\alpha 1 \rightarrow 4$ bonds to yield glucose-1-phosphate.
D) Creation of new $\alpha 1 \rightarrow 6$ linkages at branch points.
E) Final conversion of glucose-6-phosphate into free glucose in the ER.

Answer: D. The Branching Enzyme is specifically tasked with creating the $\alpha 1 \rightarrow 6$ linkages, which are necessary to form the characteristic branched structure of glycogen. Glycogen Synthase (B) builds the linear chains ($\alpha 1 \rightarrow 4$), while Phosphorylase (C) breaks them down.

Quick fire review

What are the two primary organs that store glycogen?

Liver and Muscle.

Which enzyme is responsible for creating the $\alpha 1\to 6$ linkages in glycogen?

Branching Enzyme.

Where does the conversion of Glucose-6-phosphate (G6 P) to free glucose occur, and what enzyme is required?

In the Endoplasmic Reticulum (ER), catalyzed by Glucose-6-phosphatase.

What critical function do muscle cells not perform regarding blood glucose levels?

They cannot raise blood glucose levels because they lack Glucose-6-phosphatase.

Name one high-yield bifunctional enzyme in glycogen metabolism.

Deep Branching Enzyme.

If a patient has difficulty breaking down the $\alpha 1\to 4$ linkages of glycogen, which enzyme is deficient?

Glycogen Phosphorylase.

What enzyme catalyzes the conversion of G6 P to free glucose in the liver?

Glucose-6-phosphatase (This reaction occurs in the ER).

Which type of linkage ($\alpha 1\to 4$ or $\alpha 1\to 6$) is formed by Glycogen Synthase, and which enzyme forms the other?

$\alpha 1\to 4$ linkages are made by Glycogen Synthase; $\alpha 1\to 6$ linkages are made by Branching Enzyme.

What is the primary difference in glycogenolysis between muscle and liver tissue?

The liver possesses Glucose-6-phosphatase, allowing it to release free glucose into the blood; muscle lacks this enzyme.

Name the two subunits that make up the Deep Branching Enzyme.

$\alpha 1\to 6$ Glucosidase and 4-O-Glucano Transferase.

What is the fate of G6 P in a fed state, and what initial enzyme traps it inside the cell?

It is converted to UDP-glucose for storage; Hexokinase (or Glucose Kinase) phosphorylates glucose to trap it as G6 P.

Quick recall / Anki-style questions