Lipids 2 Flashcards
In the beta oxidation pathway, how many fatty acid carbons does it break down at a time?
2
What are the products of beta oxidation?
Acetyl CoA, NADH, and FADH2 all sources of energy for ATP
Where does beta oxidation occur?
In the mitochondrial matrix
What does FA released from an adipocyte bind to?
Albumen
What are the stages for fatty acid to undergo beta oxidation?
Activation, transport and degradation (explain each)
How is the fatty acid released from adipocytes?
lipolysis
How does the fatty acyl co a cross the mitochondrial walls?
Fatty acyl co a diffuses across the first membrane. The carnitine shuttle is responsible for the movement of the fatty acyl co a across the second membrane- Co a component of the molecule is removed, remaining molecule then binds to carnitine and passes over the membrane with help from translocase. Carnitine is removed and fatty acyl co a is reformed
What is the effect of malonyl co a?
Malonyl is needed for FA synthesis - therefore prevent the synthesis and degradation happening at the same time.
What is the effect of carnitine fatty acyl tranferase or carnitine palmitoyl transferase deficiency?
No beta oxidation
Hypoglycemia
What are the steps of degradation?
Dehydrogenation - produces FADH2
Hydration - Requires H20
Dehydrogenation- To produce NADH
Thyolysis- Cleaved to produce acetyl co a
What is the precursor of FADH2 and NADH
FADH2 = FAD
NADH = NAD+
What happens to acetyl co a produced?
Joins TCA cycle (citric acid cycle)
What carbon products are produced after every beta oxidation cycle?
A carbon species two carbons shorter than the original + acetyl co a
How much ATP does each of the following molecules give / use?
FADH2
NADH
Acetyl Co A
FADH2 = 2 ATP
NADH = 3 ATP
Acetyl Co a = 12 ATP
Where does a preliminary beta oxidation of very long fatty acids take place?
Peroxisomes
Why is the first step (dehydrogenation) less energy efficient?
No FADH2 is produced
What happens to the FA linked to the carnitine?
Diffuses from peroxisome to mitochondria for further oxidation
What happens to acetyl co a levels during fasting / starvation?
Liver flooded with acetyl co a
What is the effect of high acetyl co a levels on pyruvate dehydrogenase?
Pyruvate dehydrogenase is inhibited reducing further acetyl co a formation
What is the effect of high acetyl co a levels on pyruvate carboxylase?
Activates pyruvate carboxylase and therefore increases the oxaloacetate present
What does the amount of ketogenesis depend on?
The amount of acetyl co a, excess is converted into ketone bodies
What muscles use ketone bodies as an energy source?
The skeletal muscles, and the cardiac muscles
What important organ can ketone bodies also provide energy for?
The brain
Where are ketone bodies formed?
The liver, although the liver cannot actually use them!
How are ketone bodies transported from the liver?
In the blood to other tissues, they are soluble and do not need albumen or lipoprotein
What can lead to very high levels of ketone bodies in the blood?
Starvation or uncontrolled diabetes
What can result from a higher build to use ratio of etone bodies?
Ketonemia, ketonuria and acidosis
fruity breath odour due to acetone
What is the initial trigger for lipolysis?
‘The fasted state’ - glucagon production due to low blood glucose levels
Describe the process of lipolysis?
Triglycerides are broken down by Lipase enzymes into 3 free fatty acids released into the blood and glycerol
Functions of oxidation of fatty acids in the liver
energy for liver, ketone body production
Which pathway is favoured for fatty acid metabolism during fasted state?
Beta-Oxidation and (increased lipolysis)
Which pathway is favoured for fatty acid metabolism during fasted state?
Triglyceride synthesis and (decreased lipolysis)
Steps of Beta-oxidation
- Long fatty acids >22 carbons broken down by peroxisomes
- Dehydration - FADH2
- Rehydration
- Dehydration - NADH + H+
- Breaking bond by introducing CoA - Acetyl group + original molecule -2 carbons
What causes ketone body production?
Fasting state, Glycogon
What happens when acetyl-CoA is produced during fasting state and what can this lead to?
Excessive acetyl-CoA is stored as ketone bodies which are acidic and can lead to ketoacidosis
Where does fatty acid synthesis occur?
Mostly in cytosol of liver (also in lactating mammary gland and adipose tissue)
What is the key molecule needed to add on 2 carbons to a fatty acid during FA synthesis
Malonyl CoA (Formed from Acetyl-CoA)
What is the purpose of the citrate shuttle?
To transfer Acetyl CoA from TCA cycle across mitochondrial membrane into the cytosol (By combining with oxaloacetate then removing when across the membrane)
How is Acetyl-CoA converted into Malonyl-CoA
Acetyl-CoA carboxylase + 1 ATP
What does malonyl CoA react with to synthesis FAs
Acyl carrier protein (ACP)
What FA is produced at the ens of FA synthesis
palmitate (C16)
Where does triglyceride synthesis occur?
Endoplasmic reticulum (contains enzymes to synthesise triglycerides from fatty acid CoAs)
Can FA synthesis and degradation occur at the same time?
No
