Lipids 2 Flashcards
Can fatty acids be converted to glucose?
No because pyruvate to acetyl conenzyme A is irreversible
What does the beta-oxidation pathway do?
Degrades fatty acids two carbons at a time, producing acetyl coenzyme A, NADH and FADH2
Where does beta-oxidation occur?
Mitochondiral matrix
Why can red blood cells not perform beta-oxidation?
They have no mitochondria
What are the 3 stages of beta-oxidation?
- Activation of fatty acid in cytosol
- Transport into the mitochondria
- Degradation to two carbon as acetyl coenzyme A
What do fatty acids form when they are activated?
Fatty acyl coenzyme A
Where does the activation of fatty acids occur?
The cytosol
What does the reaction of the activation of a fatty acid looking like?
Can fatty acyl coenzyme A pass the membrane without help?
No, it needs to use the carmitine shuttle
What is the process of the carnitine shutle?
- Carnitine reacts with acyl coenzyme A to produce acyl carnitine which crosses the mitochondrial membrane
- Inside the mitochondria acyl carnitine reactions with coenymze A to produce acyl conenzyme A
- Carnitine crosses the membrane and returns to the cytosol to be used again
What does the carnitine shuttle look like?
What enzymes are used in the carnitine shuttle?
Carnitine palmityl transferase I and II
What can inhibit carnitine polmityl transerase?
Malonyl coenzyme A when their is enough broken down fatty acids
What does malonyl coenzyme A ensure?
That synthesis and degradation do not happen at the same time
Where does carnitine come from?
The diet
Made from lysine or methionine
What does carnitine palmitoyl transferase dificiency lead to?
No beta-oxidation (hypoglycemia)
Coma
What is the treatment of carnitine palmitoyl transferase difficiency?
Eating medium and short chain fatty acids that do not require the carnintine shuttle
What are the stages of the degradation of beta-oxidation occurs in four stages?
- Dehydrogenation to produce FADH2
- Hydration
- Dehydrogenation to produce NADH
- Thiolysis (cleaved) to produce acetyl coenzyme A
What does each beta-oxidation cycle produce?
1 acetyl coenzyme A
Spieces of carbon 2 carbons shorter than the original
What would 7 beta-oxidation pathways produce?
8 acetyl coenzyme A
7 NADH
7 FADH2
What is the total net energy yield of beta-oxidation?
129 ATP molecules
What do very long chain fatty acids (>22 carbons) need to undergo before beta-oxidation?
Preliminary beta-oxidation in peroxisomes
How are very long chain fatty acids (>22 carbons) degraded?
- Preliminary beta-oxidation in peroxisomes, does not produce FADH2 so not as efficient as shorter chains
- Shortened fatty acid links to carntine and diffuses into the mitochondria for beta-oxidation
Why are very long chain fatty acids not as efficient as shorter ones?
Preliminary beta-oxidation in peroxisomes does not produce FADH2
What happens during starving/fasting?
- Liver flooded with acetyl coenzyme A
- Acetyl coenzyme A inhibits pyruvate dehydrogenase (pyruvate to acetyl coenzyme A) and activates pyruvate carboxylase (pyruvate to oxaloacetate)
- Oxaloacetate is used to produce glucose for gluconeogenesis
What happens to excess acetyl coenzyme A during fasting?
Converted into ketone bodies
What tissues can use ketones for fuel?
Cardiac and skeletal muscle
When can brain cells use ketones for fuel?
During starvation
Where are ketone bodies made?
In the liver (mitochondrial matrix) and then transported in the blood to other tissues
What cannot use ketones for energy?
The liver
What cannot use fatty acids for energy?
The brain
Why do ketones not need albumin or lipoprotein to transport in the blood?
They are soluble
What leads to high ketone concentration?
Uncontrolled diabetes or starvation
What happens when the rate of ketone production becomes greater than the rate they are used?
Body becomes acid (ketosis) which causes a fruity oddur in breath due to acetone
What ensure that fatty acid synthesis and degradation do not happen at the same time?
Inhibition and the two happening in different places
