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36 Cards in this Set

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Most common fatty acids in human systems contain an even number of carbon atoms. True or False?
True
Where do fatty acids most commonly occur?
Primary occur as esters of of glycerol as mono-, di- or triacylglycerols (TAGs)
Why are TAGs efficient energy stores?
1. On a weight basis, TAGs yield 2.5x more energy than glycogen
2. TAGs are anhydrous, stored without associating with water
3. Their FA's are more reduced than amino acids or monosaccharides
4. Saturated or monounsaturated forms are relatively inert (non-reactive)
What is mobilisation (of triacylglycerols)?
Hydrolysis of triacylglycerols in adipose tissue and release of fatty acids into the bloodstream
What are triacylglycerols broken down into?
Monoacylglycerol + 3 free fatty acids
What is B-oxidation?
The biochemical pathway that degrades fatty acids to acetyl CoA removing two carbons at a time and tielding energy.
Where does B-oxidation occur?
Occurs in the mitochondrial matrix
What is fatty acid transport?
Carnitine is the acyl group transporter ("carnitine shuttle system"), where FAs are transported across the inner mitochondrial membrane in the form of acyl carnitine
Name the 4 steps of B-oxidation.
Step 1: Oxidation (dehydrogenation)
Step 2: Hydration
Step 3: Oxidation (dehydrogenation)
Step 4: Chain Cleavage (thiolysis)
What does the length of the FA determine in B-oxidation?
- determines the number of oxidations
- the total number of acetyl CoA groups
The oxidation of most unsaturated FA's require what two enzymes?
1. isomerase
2. reductase
(in addition to those required for the oxidation of saturated fatty acids)
What is the product of the final thiolytic cleavage of odd-chain fatty acids?
Propionyl CoA (CoA with a C3 acyl group)
What is the product of the final thiolytic cleavage of even-chain fatty acids?
Acetyl CoA (CoA with a C2 acyl group)
What can the propionyl group, derived from B-oxidation of an odd chain fatty acid, be converted to and why?
Glucose, because in mammals, propionyl CoA can be converted to succinyl CoA (TCA intermediated), succinyl CoA can be metabolised to oxaloacetate and then to glucose (oxaloacetate is a substrate of gluconeogenesis)
What does activation of a fatty acid require?
2 ATP
What does one cycle of oxidation of a fatty acid produce?
1 NADH = 2.5 ATP equivalents
1 FADH2 (CoQH2) = 1.5 ATP equivalents
1 Acetyl CoA = 10 ATP equivalents (TCA)
How many ATP molecules does 5 cycles of B-oxidation yield?
78 ATP
How many ATP molecules does the oxidation of glucose to CO2 and water yield? (Glycolysis -> Pyruvate-Acetyl CoA -> TCA)
30 ATP
What happens where there is too much acetyl-SCoA for the TCA to process?
Ketone bodies are formed
What are Ketone bodies?
Compounds produced in the liver that can be used as fuel by muscle and brain tissue
What is Ketogenesis?
The synthesis of ketone bodies from acetyl-SCoA
During prolonged starvation, the brain will switch from glucose to what, to meet up to 75% of its energy needs?
Ketone bodies
What is a highly volatile ketone?
acetone
What is Ketosis?
A condition in which ketone bodies are produced faster than they are utilised (occurs in diabetes)
What is ketonuria?
The presence of ketone bodies in the urine
What is Ketonemia?
The presence of ketone bodies in the urine
What is ketoacidosis?
Increased concentrations of ketone bodies in the blood.

*The ACID part of the name refers to the fact that two of the ketone bodies are carboxylic acids.
What happens in the body/manifestations of ketoacidosis?
- Blood buffers are overwhelmed and blood pH drops
- Dehydration due to increased urine flow
- Laboured breathing because acidic blood is a poor oxygen carrier
- Depression
- (if untreated) coma and death
What is lipogenesis?
The biosynthesis of fatty acids from acetyl-SCoA
What provides a link between carbohydrate, lipid, and protein metabolism?
Lipogenesis
Lipogenesis is the exact reverse of the beta-oxidation pathways. True or False?
False: The reverse of an energetically favourable pathway is energetically unfavourable; lipogenesis is not.
What is an Acyl-carrier protein?
ACP complex that carries the growing fatty acid chain over a number of enzymes (collected into a multi enzyme complex called fatty acid synthase), each of which catalyses a specific reaction
What two reactions need to occur before lipogenesis is able to begin?
(1) transfer of an acetyl group from acetyl-SCoA to an acyl carrier protein (ACP)
(2) conversion of acetyl-SCoA to malonyl-SCoA in a reaction that requires investment of energy from ATP; the malonyl-SCoA is then transferred to the acyl carrier protein (ACP)
In lipogenesis, what occurs occurs at each repetition?
Fatty acids with up to 16 carbon atoms are produced by a series of 4 reactions that lengthen the growing fatty acid chain by 2C atoms with each repetition
What are the names of the 4 reactions that lengthen the fatty acid chain?
(1) Condensation
(2) Reduction
(3) Dehydration
(4) Reduction
Why do we have to gain the essential unsaturated fatty acids linoleic and linolenic acid from our diet?
- In humans and animals, enzymes can only introduce a doube bond between C4 and C5 and between C9 and C10, using desaturases that act on palmitoyl CoA and stearoyl CoA
- Mammalian cells do not contain a desaturase that acts beyond the C9 position