Lecture 29 - Fatty acids as a fuel molecule Flashcards
Glucose as a fuel molecule in muscle
Red muscle cells tend to use fats (white muscles tend to use glucose)
Red muscle Long distance running Slow twice Fats as fuels Usually in aerobic conditions
White muscle Sprinting (high impact) Fast twitch Glucose as a fuel Work more under anaerobic conditions when we are working hard and can’t supply adequate oxygen. Anaerobic conditions means that the mitochondrial pathways are not working very well therefore they often use glucose through glycolysis in order to produce the energy that is required
Fatty acids as a fuel molecule
Fatty acids are the preferred fuel for most tissues
Fat is the primary energy reserve (as TAGS aka triacylglycerols which is a glycerol with 3 fatty acids attached) - makes up 5-25% of a mammalian’s body weight
Excess energy consumed as glucose is stored as fat …. Glucose goes through glycolysis which results in pyruvate which then gets turned into acetyl-CoA using pyruvate dehydrogenase, acetyl-CoA is then turned into a free fatty acid and the free fatty acid is then turned into triacylglycerol
Why store fuel as fats?
Fatty acids are more reduced than carbohydrates (more energy released when oxidised in pathways) - fatty acids do not have as much water when they are stored.
Stored carbohydrate (glycogen) is approximately 2/3 water (approx 2/3 of its weight comes from water)
Fatty acid pathway as a fuel molecule
Delivery to cells (for fuel)
Activation
Entry into mitochondria
Beta oxidation occurs
Delivery of fatty acids for fuel
In the adipose tissue (storage), inside the cell the TAG is cleaved to form FFA and glycerol via the lipase enzyme, this enzyme can be stimulated by various different signals
THe FFA and glycerol is then passively transported out of the adipose cell into the blood.
The glycerol gets processed on the liver
The FFA is hydrophobic. It in in the blood but since it is non polar there is a protein called albumin which binds the free fatty acid. This albumin protein has hydrophilic residues on the surface fo it is soluble in liquid but it provides hydrophobic pockets where the FFAs can sit (albumin-FFA). This will transport the FFA passively to the tissues that need this as a fuel molecule. Moves passively because it can move down its concentration gradient.
Once it gets to the tissues it has to be transported across the cell membrane. It does not need to be transported via facilitation because it is non-polar. However once it is in the cell it binds to FABP which is a fatty acid binding protein since the inside of the cell is hydrophilic.
Fatty acid activation
Fatty acids are activated for oxidation
Occurs before the fatty acid enters the mitochondria
Activated by attachment to CoA making fatty acyl-CoA
Energy from hydrolysis of ATP (energy accounting cost = 2 ATP) (ATP to AMP + PP) - spent some ATP to put CoA onto our fatty acid to get it into the form where it can be oxidised to then start releasing energy
Difference between fatty acyl-CoA vs Acetyl-CoA
Fatty acyl-CoA = a carbon chain of any length (activated fatty acid)
Acetyl-CoA= A two carbon chain
ATP to AMP + PP
ATP to AMP+PP require 2 ATP - one ATP required to get AMP to ADP and then another ATP required to get ADP to ATP
Where does the oxidation of fatty acids occur?
Mitochondrial matrix
What happens in the inner membrane of the mitochondria?
Electron transport chain
Inner membrane of the mitochondria is folded into
Cristae
What kind of environment is the matrix?
Aqueous environment
Mitochondrial outer membrane purpose
Barrier between the cytoplasm and the mitochondria
What happens in the matrix of the mitochondria?
Citric acid cycle
Beta oxidation
Pyruvate dehydrogenase
Transport of fatty acids into the mitochondrial matrix
Try to draw diagram from poster for this card as well
The fatty acyl-CoA must pass through two membranes
Outer membrane - fatty acyl-CoA
Inner membrane - requires the conversion to fatty acyl-carnitine
