MCB 2000 Lecture Notes - Lecture 29: Diabetes Mellitus Type 1, Adipose Tissue, Ketone Bodies

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Lecture 29-30
Anabolic Pathways
Synthesis of Fatty Acids
Happen in the fed state
High insulin glucagon, high substrate as dietary nutrients
Reason you do not store all of your energy as glycogen in the body is because glycogen has a lot
of hydroxyl groups
Therefore it is stored with water; making glycogen increases the solubility of the molecule
Solubility means that the molecule interacts with water
If you stored all your energy as glycogen, you would weigh a lot more than you do
Glycogen stores would only last about 24 hours without consuming additional carbs
Triglyceride (glycerol backbone 3 fatty acids) are very hydrophobic, not stored with water
Reason why we store our fats as triglycerides
Also if you oxidize the carbons in a fatty acid, then you will get more energy per
carbon
Partly has to do with the chemistry of fatty acids vs the chemical formula of
glucose
Function of Fatty Acids
Phospholipid → has polar head group
Triglyceride → instead of polar head group, has third fatty acid
Fatty acids are in phospholipids; phospholipids are found in membranes
Some fatty acids serve in signaling (second messenger) - diacylglycerol
Also can insert into the membrane as a liquid anchor
Synthesis of lipids (FA, TG, PL, Cholesterol)
When does it occur
High insulin/GLucagon ratio (after meal)
Excess calories comes from any excess carbs that were consumed in the diet, or carbon
skeletons from excess protein
Es: avg person relies on about 2000 calories a day
To lose weight, LOW CARB DIET & LOW CALORIE DIET
Tissues involved
Fatty acids are synthesized in the liver (and also adipose tissue)
Any excess carbon skeletons above caloric need will go into storing the carbons as triglycerides
Fatty acids → attach to glycerol backbone → triglyceride → store in adipose tissue
Lipogenesis
Availability of insulin is what determines if Acetyl-CoA is converted to fatty acids, which are
attached to glycerol to make triglycerides
Low carb diet works: by restricting carbs to less than 50 g (200cal), you DO NOT trigger insulin
release. Therefore even though caloric needs are adequately met, your body thinks it's in
starvation mode. No insulin = fasting
Low carb diet works because you are breaking down stored triglycerides for energy
Untreated Type I Diabetes (insulin not produced) - all nutrients taken in by individual will form
ketone bodies (diabetic ketoacidosis), too much ketone bodies produced and blood pH decreases
* Critical factor is presence of insulin; insulin favors fatty acid synthesis
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Document Summary

High insulin glucagon, high substrate as dietary nutrients. Reason you do not store all of your energy as glycogen in the body is because glycogen has a lot of hydroxyl groups. Therefore it is stored with water; making glycogen increases the solubility of the molecule. Solubility means that the molecule interacts with water. If you stored all your energy as glycogen, you would weigh a lot more than you do. Glycogen stores would only last about 24 hours without consuming additional carbs. Triglyceride (glycerol backbone 3 fatty acids) are very hydrophobic, not stored with water. Reason why we store our fats as triglycerides. Also if you oxidize the carbons in a fatty acid, then you will get more energy per. Partly has to do with the chemistry of fatty acids vs the chemical formula of carbon glucose. Triglyceride instead of polar head group, has third fatty acid. Fatty acids are in phospholipids; phospholipids are found in membranes.

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