Lipids Flashcards
1
Q
What are the five types of lipids and their functions?
A
- Fatty acids
- Truglycerides
- Phospholipids - membranes
- Sphingolipids - membranes
- Steroids - hormones
2
Q
Two ways of numbering a fatty acid
A
- DELTA - numbering from COOH
- OMEGA - numbering from methyl end
3
Q
Describe step one FATTY ACID OXIDATION
A
- TAG converted into FA and glycerol
- Glycerol enters glycosis
- FA gets oxidised into acetyl CoA, this also produced reduced NAD AND FAD
- This then enters krebs
- Total of 129 ATP molecules
4
Q
Describe step two FATTY ACID SYNTHESIS
A
- Excess glucose is converted into pyruvate
- Pyruvate is transported to mitoch, it forms acetyl CoA
- Acetyl CoA + OAA = citrate
- Citrate liberates acetyl CoA and OAA
- OAA transported back to mitoc as pyruvate
- OAA produces NADPH while converted into pyruvate
- Acetyl-CoA is converted into malonyl-CoA by acetyl-CoA carboxylase
- Malonyl-CoA blocks CAT I to prevent FA oxidation
- Condensation, 1st reduction, dehydration and 2nd reduction are the
major steps in FA biosynthesis - 16C palmitic acid is produced and releases
5
Q
Step three CHOLESTROL SYNTHESIS
A
- Cholestrol is synthesised in the liver
- Occurs in five stages
- HMG-CoA reductase is a rate limiting enzyme that controls cholesterol biosynthesis
- Cholesterol is used as a precursor for steroid hormone synthesis,
bile acids and vitamin D - Most of the cholesterol is recycled and a small amount gets excreted
- Excess cholesterol prevents the synthesis
- Excess cholesterol leads to atherosclerosis
- Extremely important to control the cholesterol level to prevent CVDs
- Statins target HMG-CoA reductase to lower cholesterol levels
6
Q
Function of lipoproteins in breaking down fats
A
- lipase breaks down micelles into FAs and monoglycerides and these enter epithelial cells of small intestine
- they then enter ER
- cholesterol is transported through specific channels into small intestine
- cholesterol + triglycerides + protein make chylomicrons
- proteins on chylomicrins make them water soluble and facilitate exocytosis
- chylomicrons are removed by the lymphatic system
