Lipids Building Blocks Flashcards
Define a biological lipid
Biological compound that are insoluble in water but soluble in organic solvents; hydrophobic.
Arachidonic acid derivatives
-Prostaglandins: Mucosal production, inflammation and fever
-Thromboxanes: formation of blood clots
- Leukotrienes: smooth muscle contraction in lungs and inflammation
Chylomicrons
Triglycerides are digested into fatty acids and monoacylglycerol in SI
Reformed in enterocytes
Packaged into chylomicrons
Enter lymphatic system- become chyle fluid
Fats as fuel storage
Triglycerides are stored in adipose tissue ( formed of adipocytes)
Used for energy during times of fasting or starvation
Lipolysis in adipocytes
Breakdown of stored TAGs to FAs and glycerol
Induced by several hormones (glucagon, epinephrine and cortisol)
FAs and glycerol transported to blood by other organs; skeletal and cardiac muscles and liver
Why can’t brain use fatty acids for energy?
Fatty acids cannot cross the blood brain barrier
Beta-oxidation
FAs are metabolised via beta-oxidation
Occurs in the mitochondria
FAs can’t cross the mitochondrial double membrane
Transported by the carnitine shuttle
Carnitine shuttle process
1) FA bound to CoA- fatty acyl CoA
2) CoA exchanged for carnitine- acyl carnitine
3) Acyl carnitine translocated by facilitated diffusion
4) Carnitine on acyl carnitine exchanged for CoA
Ketogenesis
Excess acetyl CoA converted into ketones
Acetoacetate and B-hydroxybutyrate can be used by brain and muscles as secondary energy source
Acetone has no metabolic function; excreted in breath
Examples of glycerophospholipids
-PHOSPHATIDYLCHOLINE: most common phospholipid in plasma membrane
-PHOSPHATIDYLINOSITOL-4,5-BIPHOSPHATE: involved in cell signalling
-CARDIOLIPIN: found in cardiac tissue & mitochondria, biomarker for apoptosis
Sphingolipids
Similar to phospholipids; only one fatty acid
FA linked to sphingosine NOT glycerol
Sphingomyelin structure
Consists of:
Phosphocholine head
Sphingosine
A fatty acid
Sphingomyelin function
Found in myelin sheath- action potential and transduction
Involved in apoptosis
Examples of steroid hormones
-Sex Hormones
-Cortisol
-Aldosterone
-Steroid drugs
-Brassinolide
Bile Acids
Biological detergents
Detergent: solubilises lipids and makes them water soluble
Breaks fats into micelles to aid digestion
Which vitamins are fat soluble?
Vitamins A, D, E & K
Which vitamins are water soluble?
Vitamins B & C
Vitamin D
Fat soluble
Synthesis involves skin, liver & kidney
Needed for calcium absorption from SI
Vitamin A (retinol)
Fat soluble
Produced from B-carotene
Converted to 11-cis-retinal which can be converted to retinoic acid
Retinoic acid important in gene transcription in embryological development
Vitamin E
Fat soluble
Protects FAs in cell membranes from oxidation
Vitamin K
Fat soluble- hydrophobic
Co-factor in blood coagulation pathway
enzyme: Vit K-dependent carboxylase
Why are water soluble vitamins NOT toxic at high doses when others are?
Can be easily extracted by the kidneys
Fat soluble vitamins need to be converted to a more hydrophilic product for excretion
Waxes: structure and function
Two components joined by an ester bond
- long chain fatty acid
- long chain alcohol
Functions:
- Waterproofing
- Beeswax
- Protection of hair and skin
Lipoprotein pathway
- Transports fatty acids and cholesterol
- Protein shell allows solubility
- Higher cholesterol content
- Named by triglycerol density; VLDL, IDL, LDL, HDL
LIPOGENESIS
Synthesis of fatty acids
- excess glucose is converted into fatty acids and TAGs for long-term storage in adipocytes
- Acetyl CoA from glycolysis and pyruvate
- NADPH required
- Occurs in the liver mainly
- TAGs are exported from liver as VLDL
LIPOGENESIS
Synthesis of fatty acids
- excess glucose is converted into fatty acids and TAGs for long-term storage in adipocytes
- Acetyl CoA from glycolysis and pyruvate
- NADPH required
- Occurs in the liver mainly
- TAGs are exported from liver as VLDL
