Module 8.1: Cell Metabolism + Lipid Droplets

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Questions and Answers

What is the role of cellular trafficking in metabolism?

Transport of waste out of cells

Control of cell division

Regulation of cell size

Transport of energy into cells (correct)

What is the function of insulin in the body?

Regulate body temperature

Facilitate uptake and storage of nutrients (correct)

Break down lipids

Stimulate muscle growth

What is the primary site of insulin production and packaging in the body?

β-cells in the pancreas (correct)

Liver

Thyroid gland

Adrenal glands

What activates proteases to cleave proinsulin into the active hormone in the pancreas?

Acidic vesicles Signup and view all the answers

What is the function of lipid droplets in cellular metabolism?

Storage and transport of energy Signup and view all the answers

What is the role of hormone receptor trafficking in cellular metabolism?

Facilitate cellular response to hormones Signup and view all the answers

What percentage of cells in the pancreas make up the β-cells responsible for insulin production?

1-2% Signup and view all the answers

Which nutrients are used to make energy in cellular metabolism?

Sugars, fat, and protein Signup and view all the answers

What is the primary function of dense core granules in the pancreas?

Production and packaging of insulin Signup and view all the answers

What is the essential role of cell trafficking in hormone processing and secretion?

Facilitate hormone release from cells Signup and view all the answers

Which glucose transporter is regulated by insulin in muscle, adipose, and heart cells?

GLUT4 Signup and view all the answers

What is the primary purpose of insulin receptor internalization?

Decreasing hormone action in the cell Signup and view all the answers

What contributes to insulin resistance in diabetes?

Decreased insulin receptor levels Signup and view all the answers

What is the function of lipid droplets in cells?

Serve as a primary energy source for the cell Signup and view all the answers

Which cells are particularly efficient in lipid droplet function?

Adipocytes Signup and view all the answers

What is the form in which fat is stored in lipid droplets?

Acyl-glycerols Signup and view all the answers

What is the role of insulin in lipid synthesis and storage?

Stimulates lipid synthesis and storage Signup and view all the answers

What is the primary factor controlling the level of glucose that can enter muscle and fat cells?

Insulin receptor levels Signup and view all the answers

What is the consequence of long-term insulin exposure on insulin receptor recycling?

Receptor degradation Signup and view all the answers

Apart from storage, what crucial role does the lipid droplet play in cellular energy regulation?

Serving as a source of energy Signup and view all the answers

What is the primary structure of lipid droplets?

Single, phospholipid protein-containing hemimembrane Signup and view all the answers

What is the main function of Rab proteins in relation to lipid droplets?

Regulate interactions with specific organelles Signup and view all the answers

What does the presence of different associated proteins in lipid droplets suggest?

Subsets with different properties and functions Signup and view all the answers

How are lipid droplets formed?

Accumulation of neutral lipid between the leaflets of the phospholipid bilayers in the endoplasmic reticulum (ER) Signup and view all the answers

What do lipid droplets store for the cell's use?

Free fatty acids Signup and view all the answers

How do lipid droplets move around and interact with various organelles?

Travel along microtubules Signup and view all the answers

What is the primary role of lipid droplets in cellular metabolism?

Store newly synthesized lipids and carry proteins or lipid-soluble molecules to areas of the cell where they are needed Signup and view all the answers

How does viral infection affect lipid droplets?

Increases the size of lipid droplets, affecting cell function Signup and view all the answers

What is the consequence of viral proteins and RNA being concentrated and transported on the surface of lipid droplets?

Aids in viral assembly and replication, and promotes secretion of lipoproteins with attached virus into circulation Signup and view all the answers

What essential roles do membrane vesicles, including lipid droplets, play in cellular metabolism?

Metabolism, hormone packaging and secretion, glucose regulation, and organelle function Signup and view all the answers

Study Notes

Insulin and Glucose Regulation in Cells

Insulin is stored in vesicles distributed throughout the cell, particularly in high volumes in β-cells and is released in response to external stimuli such as glucose or hormone signals.
Insulin release from β-cells involves coordinated mitochondrial and calcium signaling, and metabolism and trafficking are required to control the two phases of insulin secretion.
Glucose uptake into cells is dependent on the trafficking of glucose transporters such as GLUT1, GLUT2, GLUT3, and GLUT4, with only GLUT4 being regulated by insulin in muscle, adipose, and heart cells.
Insulin stimulates the recruitment of GLUT4 to the plasma membrane, allowing glucose entry into muscle and fat cells and controlling the level of glucose that can enter these cells.
Insulin receptor activity is tightly controlled by ligand-mediated receptor internalization, which can lead to hypoglycemia if uncontrolled, and the internalized receptor has purposes beyond decreasing hormone action in the cell.
Insulin receptor internalization has purposes beyond decreasing hormone action in the cell, including the activation of the Ras/MAP kinase pathway and sustainment of ligand-induced Akt phosphorylation.
Insulin receptor internalization also involves ligand degradation, and the levels of receptor at the cell surface control how well insulin works, with decreased insulin receptor levels contributing to insulin resistance in diabetes.
Long-term insulin exposure may lead to receptor degradation instead of recycling, and altered recycling kinetics of the receptor are seen in cells from diabetic patients and those exposed to high glucose for long periods.
Lipid droplets store fat and are stimulated by insulin, serving as a readily available source of energy during times of energy demand.
Lipid droplets are present in all cells but are particularly efficient in cells such as adipocytes and hepatocytes.
Lipid droplets store fat in the form of cholesteryl esters or acyl-glycerols, and lipid synthesis and storage are stimulated by insulin.
The lipid droplet has a basic structure and is located in the cell, and it is not just for storage anymore, as it plays a crucial role in cellular energy regulation.

Lipid Droplets and Their Interactions with Organelles: Key Insights

Lipid droplets have a single, phospholipid protein-containing hemimembrane, making physical contact with outer membranes of other organelles.
Proteomic analysis of lipid droplets has identified a number of different Rab proteins that regulate interactions with specific organelles.
Not all lipid droplets in a cell have the same associated proteins, suggesting subsets with different properties and functions.
The most accepted theory is that lipid droplets are formed following the accumulation of neutral lipid between the leaflets of the phospholipid bilayers in the endoplasmic reticulum (ER).
Lipid droplets store free fatty acids synthesized or taken up by the cell, which can be broken down by lipases when needed for fuel.
Lipid droplets can move around and interact with various organelles such as mitochondria, peroxisomes, and the ER for the exchange of proteins and lipids for fuel.
Lipid droplet movement in cells includes oscillation in specific areas, travel along microtubules, and induction by various factors such as infections and hormones.
Lipid droplets serve as storage space for newly synthesized lipids and can recruit and carry proteins or lipid-soluble molecules to areas of the cell where they are needed.
They also allow fusion/fission, may serve as sites for protein translation, and act as a source of lipid building blocks or fuel for organelles.
Viral infection increases the size of lipid droplets, affecting cell function, and hepatitis C virus (HCV) uses lipid machinery of liver cells for replication and spread.
Viral proteins and RNA are concentrated and transported on the surface of lipid droplets, aiding in viral assembly and replication, and promoting secretion of lipoproteins with attached virus into circulation.
Membrane vesicles, including lipid droplets, play essential roles in metabolism, hormone packaging and secretion, glucose regulation, and organelle function, with implications for metabolic diseases and treatment.

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Description

Test your knowledge of insulin and glucose regulation in cells and lipid droplets and their interactions with organelles with this informative quiz. Explore the intricate mechanisms of insulin release, glucose uptake, insulin receptor activity, and lipid droplet function in cellular energy regulation. Gain key insights into the roles of lipid droplets in cellular metabolism, viral infection, and organelle interactions.