S2) Energy Production III — Lipids, β-Oxidation & Ketone Bodies Flashcards
Identify and describe the three different classes of lipids
- Fatty acid derivatives – fatty acids and triacylglycerol
- Hydroxy-methyl-glutaric acid derivatives – ketone bodies, cholesterol
- Vitamins – ADEK
Explain how energy storage varies between a healthy and obese man
Describe the structure of triacyglycerol
Triacylglycerols are hydrophobic
Describe the storage of TAG
- Stored in an anhydrous form
- Stored in adipose tissue
- Storage / mobilisation under hormonal control
Identify three circumstances where triacylglycerols are used
- Prolonged exercise
- Starvation
- Pregnancy
Identify the tissues involved in triglyceride metabolism and illustrate their role
Where does stage 1 of TAG metabolism occur?
Gastrointestinal tract (extracellular)
What occurs in stage 1 of TAG metabolism?
- Extracellular hydrolysis of dietary lipids (TAG) in small intestine by pancreatic lipases
- Fatty acids and glycerol are formed
In 5 steps, describe what happens in TAG metabolism after absorption in to the GI tract
⇒ Converted back to triglycerides in GI tract
⇒ Packaged into lipoprotein particle (chylomicrons)
⇒ Released into circulation via lymphatics
⇒ Carried to adipose tissue
⇒ Stored as triglyceride
Describe fat mobilisation
- Fatty acids are released when needed
- They are carried to tissues as albumin-fatty acid complex
Fat mobilisation is under hormonal control.
Describe this
Hormone-sensitive lipase:
- Increases with glucagon/adrenaline
- Decreases with insulin
Which consumer tissues are fatty acids not mobilised to?
- Cells without mitochondria e.g. RBC
- Brain; fatty acids do not easily pass blood-brain barrier
In 5 steps, describe and illustrate the triglyceride/fatty acid cycle in adipose tissue
1 – Glucose transport
2 – Glycolysis
3 – Esterification
4 – Lysis
5 – Re-esterification
What causes the release of fatty acids as alternative fuel?
Low extracellular [glucose]
Describe the molecular structure of fatty acids
Amphipathic: contain hydrophilic & hydrophobic groups