Ketone Body Synthesis Quiz

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Questions and Answers

What is the end product of TAG hydrolysis by hormone-sensitive lipase?

Free fatty acids and glycerol (correct)

Acetoacetate and acetone

Acetyl-CoA and glycerol kinase

Triacylglycerol

In tissues like the liver and kidney, what is glycerol converted into?

Triacylglycerol

Acyl-CoA

Glycerol 3-phosphate (correct)

Ketone bodies

What enzyme is responsible for converting FFA to acyl-CoA in adipose tissue?

Hormone-sensitive lipase

Gluconeogenesis enzyme

Acyl-CoA synthase (correct)

Glycerol kinase

When does the accumulation of FFA in plasma occur?

During lipolysis Signup and view all the answers

What is the alternative fuel source for cells during conditions like starvation according to the text?

Ketone bodies Signup and view all the answers

Which additional functional group do phospholipids have?

Phosphate group Signup and view all the answers

In which group do fatty acids fall in terms of being hydrophilic or hydrophobic?

Hydrophobic Signup and view all the answers

What is the predominant lipid found in cell membranes?

Phospholipids Signup and view all the answers

Which class of lipids includes glycerophospholipids?

Steroids Signup and view all the answers

Which part of phospholipids forms the hydrophobic group?

Fatty acids Signup and view all the answers

What is the role of thiolase in the process described?

It catalyzes the breakdown of HMG-CoA into acetoacetate and acetyl-CoA Signup and view all the answers

What is the purpose of the non-enzymatic decarboxylation of acetoacetate to acetone?

To facilitate the release of acetone in breath, which can be used as a diagnostic marker Signup and view all the answers

In the context of ketolysis, what is the role of succinyl-CoA?

It provides a CoA molecule for the conversion of acetoacetate to acetoacetyl-CoA Signup and view all the answers

What is the primary reason for the production of ketone bodies in individuals with type I diabetes?

Lack of insulin leads to the inability to use glucose as a fuel source, so fat is used instead Signup and view all the answers

What is the role of NADH in the ketolysis process?

It is produced during the oxidation of 3-hydroxybutyrate to acetoacetate Signup and view all the answers

What is the significance of the liver constantly synthesizing ketone bodies during fasting?

It provides an alternative energy source when glucose is unavailable Signup and view all the answers

Study Notes

Lipolysis and Re-Esterification

TAG undergoes hydrolysis by hormone-sensitive lipase to form free-fatty acids (FFA) and glycerol
Glycerol is transported to liver and kidney, where it is converted to glycerol 3-phosphate by glycerol kinase
FFA can be reconverted to acyl-CoA by acyl-CoA synthase and re-esterified with glycerol 3-phosphate to form triacylglycerol
There is a continuous cycle of lipolysis and re-esterification within the tissue

Importance of Carbohydrates

Carbohydrates are essential for metabolism of fat
Acetyl-CoA from fatty acid can enter and be oxidized in TCA cycle when carbohydrates are available

Ketogenesis

Ketogenesis occurs when carbohydrates are unavailable, such as in starvation, fasting, and diabetes mellitus
Acetyl-CoA formed from fatty acid oxidation is converted into ketone bodies (acetoacetate, 3-hydroxybutyrate, acetone)
Liver mitochondria convert acetyl-CoA from fatty acid oxidation into ketone bodies

Type I Diabetes Mellitus

Characterized by ↓ insulin and ↑ glucagon
Biochemical findings:
- ↑Blood glucose
- ↓Blood pH
- ↓HCO3
- Benedict’s test positive → Glucose
- Rothera’s test positive → Ketone bodies
- Free fatty acids in plasma
Hepatic output of ketone bodies
Ketoacidosis: Ketonemia – 90 mg/dl, Keturia – 5000 mg/24hr
Fruity odour on breath

Phospholipids

Complex lipids with phosphate as the additional functional group
Amphipathic molecules with hydrophilic and hydrophobic groups
Phosphate and nitrogen base (e.g. choline, ethanolamine) forms the hydrophilic group
Fatty acids form the hydrophobic group
Predominant lipids of cell membranes (Phospholipid bilayer)
Two classes of phospholipids: Glycerophospholipids and Sphingophospholipids

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Description

Test your knowledge on ketone body synthesis process which includes reactions catalyzed by thiolase, formation of HMG-CoA, degradation to acetoacetate, and reduction to 3-hydroxybutyrate. Learn about the non-enzymatic decarboxylation of acetoacetate to acetone.