Lipid Synthesis and Degradation
This lecture is about how we can synthesise lipids from other components,
predominantly carbohydrates.
Fatty acid synthesis and degradation join onto the pathway we’ve been studying, this
is shown below
Fats are obtained either from the diet or made de novo (new) from carbohydrates.
Fats play an essential role in many biological functions including:
- Membranes
- Important in uptake of fat-soluble vitamins
- Used as precursors for steroid hormones
- As an energy store
Fat is such an important store of energy because the energy content of fat per gram is
over twice that of either carbohydrate or protein. So fat is a very good way of storing
energy
There are major health implications of fat, 40% of the energy of the British Diet is
from fat. In 2010 62.8% of adults (16+) were overweight or obese. 30.3% of children
(2-15) were overweight or obese. A massive 26.1% of all adults and 16% of children
were obese.
This has huge costs on the NHS and results in many premature deaths every year.
The culprits of these problems are:
-> Fatty acids
-> Triglycerides or Neutral Fats
-> Cholesterol
, Fat Synthesis
When calorific intake (usually in form of carbs) exceeds consumption, excess is laid
down as fat. This is because we are derived as hunter-gatherers, the body is designed
for periods of famine.
Some tissues such as cardiac muscle use fats as their preferred energy source.
However, dietary carbohydrate is the most common source, although amino acids
can also be used.
Lipid Synthesis and Degradation
Most of the lipid synthesis and degradation occurs in the liver hepatocytes, with
synthesis occurring in the cytosol and the breakdown (through beta oxidation)
mostly occurring in the mitochondria. An example of compartmentalization.
These reactions are largely reciprocally regulated, you get synthesis when there is
excess calorie intake and during this breakdown is inhibited. If you need breakdown
then the reactions leading to synthesis are inhibited.
Triglycerides are neutral fats (how most fats are stored), they consist of three fatty
acids attached to a glycerol backbone. Triglycerides are concentrated stores of
energy.
Remember that the glycerol can be made from glycolysis by glycerol-3-phosphate,
glycerol can also be fed into glycolysis at this point.
A triglyceride
Fatty acids are chains of methyl groups with a carboxyl group at the end (terminal).
The fatty acids can be saturated with single bonds or unsaturated with double bonds.
An example of two important ones are palmitate and oleate.
Humans are unable to create double bonds in positions less than position nine, so
fatty acids that have these are essential fatty acids and we must obtain them from out
diet.
This lecture is about how we can synthesise lipids from other components,
predominantly carbohydrates.
Fatty acid synthesis and degradation join onto the pathway we’ve been studying, this
is shown below
Fats are obtained either from the diet or made de novo (new) from carbohydrates.
Fats play an essential role in many biological functions including:
- Membranes
- Important in uptake of fat-soluble vitamins
- Used as precursors for steroid hormones
- As an energy store
Fat is such an important store of energy because the energy content of fat per gram is
over twice that of either carbohydrate or protein. So fat is a very good way of storing
energy
There are major health implications of fat, 40% of the energy of the British Diet is
from fat. In 2010 62.8% of adults (16+) were overweight or obese. 30.3% of children
(2-15) were overweight or obese. A massive 26.1% of all adults and 16% of children
were obese.
This has huge costs on the NHS and results in many premature deaths every year.
The culprits of these problems are:
-> Fatty acids
-> Triglycerides or Neutral Fats
-> Cholesterol
, Fat Synthesis
When calorific intake (usually in form of carbs) exceeds consumption, excess is laid
down as fat. This is because we are derived as hunter-gatherers, the body is designed
for periods of famine.
Some tissues such as cardiac muscle use fats as their preferred energy source.
However, dietary carbohydrate is the most common source, although amino acids
can also be used.
Lipid Synthesis and Degradation
Most of the lipid synthesis and degradation occurs in the liver hepatocytes, with
synthesis occurring in the cytosol and the breakdown (through beta oxidation)
mostly occurring in the mitochondria. An example of compartmentalization.
These reactions are largely reciprocally regulated, you get synthesis when there is
excess calorie intake and during this breakdown is inhibited. If you need breakdown
then the reactions leading to synthesis are inhibited.
Triglycerides are neutral fats (how most fats are stored), they consist of three fatty
acids attached to a glycerol backbone. Triglycerides are concentrated stores of
energy.
Remember that the glycerol can be made from glycolysis by glycerol-3-phosphate,
glycerol can also be fed into glycolysis at this point.
A triglyceride
Fatty acids are chains of methyl groups with a carboxyl group at the end (terminal).
The fatty acids can be saturated with single bonds or unsaturated with double bonds.
An example of two important ones are palmitate and oleate.
Humans are unable to create double bonds in positions less than position nine, so
fatty acids that have these are essential fatty acids and we must obtain them from out
diet.
