Oxidation Pathways Flashcards
What are the stages of fatty acid or beta oxidation?
- Transport - fatty acids from blood to cytoplasm
- Trapping fatty acids in the cytoplasm
- Transporting fatty acids into the mitochondria
- Stripping h/e out to make acetyl CoA
How do fatty acids exist in the bloodstream?
Loosely associated with albumin.
What is meant by the amphiphilic nature of fatty acid molecules? What does this mean for transport in the blood?
Had hydrophilic and hydrophobic parts. Bound to albumin so it doesn’t act like a detergent in the blood.
How does transport from the blood to the cytoplasm occur of fatty acids?
Mostly passive.
What are fatty acid molecules associated within the cytoplasm?
Fatty acid binding proteins.
What is linked to fatty acid to trap the molecules inside the cytoplasm?
Coenzyme A. It is always attached to CoA from this point onwards.
What activates the fatty acid inside the cytoplasm?
Attachment to CoA
What are the energy requirements of activating fatty acids by turning them into FA-CoA?
High - ATP converted to AMP and pyrophosphate is hydrolysed.
What is CoA? What is involved in its form?
A large charged molecule. (Card 5 for form).
How does the transport of fatty acids to the mitochondria occur?
React the fatty acid CoA with carnitine to make fatty acylcarnitine which can be transported across the mitochondrial membrane to the matrix. (Carnitine acyl-transferases)
Once inside the mitochondria what happens to the FA?
The opposite to how it got in - carnitine goes back to the cytoplasm.
What occurs in the first H/e- stripping step of fatty acid oxidation?
FAD rips hydrogens out of CH2CH2 links and forms a double bond between beta and alpha carbon atoms. This is hydrated to give rise to an OH group at the beta position.
How is the first H/e- stripping step of fatty acid oxidation catalysed?
By a dehydrogenase that uses FAD (acyl-CoA dehydrogenase).
What occurs in the second H/e stripping step of fatty acid oxidation?
NAD stips from the OH group. Rips out hydrogens and electrons from the alcoholic group and turns it into a keto group. The keto carbon is attacked by CoA and get acetyl-CoA - comes off the original chain and leaves a 14 carbon acyl CoA.
Glycolysis occurs in the ______.
Cytoplasm.
What is the purpose of glycolysis? ie what does it bridge?
Forms bridge between the processing of glucose from the blood and endogenous glycogen to provide acetyl CoA for Krebs cycle or lactate to be recycled by the liver.
What is the first step of glycolysis?
Glucose uptake by the glucose transporters?
What are the glucose transporters and where are they located?
GLUT 1 - present in all cells at all times
GLUT 4 - live in golgi apparatus and come out during exercise or stimulated by insulin (muscle and adipose tissue)
GLUT 2 - in liver and pancreas
What happens to glucose when it moves from the blood into the cytoplasm?
Hexokinase using ATP transforms glucose into glucose 6-phosphate.
What is the preparatory phase of glycolysis?
Phosphorylation and trapping. Further phosphorylation to a molecule that can be phosphorylated in the 1 and 6 positions (ATP used).
What are we left with at the end of the preparatory phase of glycolysis?
A symmetrical molecule that is ready to liberate energy and split in two at the end of the phase to produce 2 3-carbon molecules. (Card 6)
What occurs in the first step of phase 2 of glycolysis?
Use of NAD to give NADH and convert it to energy-dense molecule which is primed for direct phosphorylation of ADP.
What occurs in the second step of phase 2 of glycolysis?
1,3-bisphosphoglycerate phosphorylates ADP to ATP at the substrate level.
What occurs in the third step of phase 2 of glycolysis?
The 3 carbon molecules made in phase 1 are rearranged to make phosphoenolpyruvate - make ATP and lose phosphate to make pyruvate. Happens twice for every molecule of glucose (2 3-carbon). Card 6
What do we have at the end of glycolysis?
2 ATP per glucose, 2 pyruvates and two NADH
How do we complete glycolysis?
Pyruvate undergoes oxidation either aerobic or anaerobic.
How does oxidation of pyruvate occur?
Transport into mitochondria and oxidised with pyruvate dehydrogenase.
How do we maintain the supply of NAD?
Peroxide NADH - leads to lactate production.
The Krebs cycle occurs in the ________.
Mitochondria
What is the role of the Krebs cycle?
NOT to produce ATP but produce NADH and FADH2 for the electron transport chain.
What else (not nadh or fadh2) is generated in the Krebs cycle and how ?
Acetyl CoA oxidise all acetate carbons to carbon dioxide. CO2.
Oxaloacetate is a ____ carbon molecule that is converted to _____ using _________.
- Citrate (6C) using acetyl CoA.
Citrate in the Krebs cycle undergoes_______?
Two oxidation steps that result in the formation of carbon dioxide.
After the two carbon dioxides are made from the oxidation steps in the Krebs cycle what happens?
The rest of the steps are used to synthesise oxaloacetate so the reaction can go again. (Card 7)
Provide an overview of exactly what is generated in the citric acid cycle.
(Card 7)
How are the beta oxidation pathways regulated?
Mainly by availability of co-factors NAD, FAD and ADP and inhibited by high energy change (ATP:ADP)
