Biochemistry: Beta-oxidation
Beta-oxidation occurs in the mitochondrial matrix, where all required enzymes are located. It breaks down acyl CoA (activated fatty acid) — derived from TAGs — into acetyl CoA, NADH, and FADH₂. Acetyl CoA enters the CAC to help generate ATP. Fatty acids enter mitochondria via the carnitine transport system. Redox and hydration reactions occur during the cycle, and each round shortens the fatty acid by two carbons, releasing one acetyl CoA.
Why does beta-oxidation occur in the matrix of the mitochondria where all of the enzymes needed for beta-oxidation are located?
Each of the beta-oxidation steps require a specific enzyme to facilitate the chemical reaction. The enzymes needed for beta-oxidation are located in the matrix of the mitochondria.
A metabolic reaction always occurs where the enzymes needed for the reaction are located.
Key Terms
Why does beta-oxidation occur in the matrix of the mitochondria where all of the enzymes needed for beta-oxidation are located?
Each of the beta-oxidation steps require a specific enzyme to facilitate the chemical reaction. The enzymes needed for b...
What is the starting input (reactant) for beta-oxidation and what is the final output (end products)?
Input: Fatty acids (specifically acyl CoA)
Output: Acetyl CoA and the reduced coenzymes...
Where does the input required for beta-oxidation come from?
The FAs required for beta-oxidation come from triacylglycerol (TAG).
TAGs are the fat s...
What modification is required so that the fatty acid can be used to start beta-oxidation?
How is the fatty acid derivative moved into the mitochondria where beta-oxidation takes place?
Before the FA can be used in beta-oxidation it must attach to a CoA. (It is then called an acyl CoA.)
What is the final output of beta-oxidation used for? For what purpose?
Output = Acetyl CoA - is taken to the CAC (also in the mitochondria).
Each cycle of the...
Why is it necessary for us to perform beta-oxidation? Why is it important?
Beta-oxidation is needed to produce a lot of acetyl CoA (from FAs) which are used to generate ATP (via CAC, ETC, and OP)...
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| Term | Definition |
|---|---|
Why does beta-oxidation occur in the matrix of the mitochondria where all of the enzymes needed for beta-oxidation are located? | Each of the beta-oxidation steps require a specific enzyme to facilitate the chemical reaction. The enzymes needed for beta-oxidation are located in the matrix of the mitochondria. A metabolic reaction always occurs where the enzymes needed for the reaction are located. |
What is the starting input (reactant) for beta-oxidation and what is the final output (end products)? | Input: Fatty acids (specifically acyl CoA) Output: Acetyl CoA and the reduced coenzymes FADH2 and NADH. 1 NADH |
Where does the input required for beta-oxidation come from? | The FAs required for beta-oxidation come from triacylglycerol (TAG). TAGs are the fat storage compounds found in the adipose tissues. TAG are broken down into three fatty acids and one glycerol. The FAs can then be used for beta-oxidation. |
What modification is required so that the fatty acid can be used to start beta-oxidation? How is the fatty acid derivative moved into the mitochondria where beta-oxidation takes place? | Before the FA can be used in beta-oxidation it must attach to a CoA. (It is then called an acyl CoA.) The carnitine transport system is used to move the acyl CoA from the cytosol into the matrix of the mitochondria (where beta-oxidation occurs). |
What is the final output of beta-oxidation used for? For what purpose? | Output = Acetyl CoA - is taken to the CAC (also in the mitochondria). Each cycle of the CAC requires one acetyl CoA to begin. The CAC produces many electron-rich coenzymes that are then taken to the ETC/OP and used to generate ATP. |
Why is it necessary for us to perform beta-oxidation? Why is it important? | Beta-oxidation is needed to produce a lot of acetyl CoA (from FAs) which are used to generate ATP (via CAC, ETC, and OP). It’s a vital step to generate energy from lipids. |
The first and third steps (chemical reactions) of beta-oxidation are redox reactions where the compound of the reaction is oxidised. How do the NAD+ and FAD coenzymes help facilitate these redox reactions in beta-oxidation? (pic - FAD gains 2 H and NAD+ gains one H) The OH group is converted to . . . ? | Step 1: FAD is reduced to FADH2, (reactant is oxidised as it loses two hydrogen atoms). The product compound forms a double C=C bond to ensure that each carbon atom has four covalent bonds. Step 3: NAD+ is reduced to NADH, (reactant is oxidized as it loses two hydrogen atoms). The oxygen forms a double bond to the carbon to ensure that both the carbon and oxygen atom have their correct number of covalent bonds. The oxidation of the compound converts the alcohol functional group to a ketone functional group. |
Step 2 of beta-oxidation is a hydration reaction. How does the addition of a single H2O result in the addition of an alcohol (-OH) group and the loss of a double carbon-carbon bond? | One of the C-C bonds is broken = two free bonding positions for other atoms to attach to the carbon atoms. H2O splits in two to become OH and H which attach to one of the carbon atoms via a covalent bond. The product compound has gained an OH group. |
Step 4 of beta-oxidation is the thiolysis step that releases an acetyl CoA unit. What happens in the thiolysis reaction that allows an acetyl CoA to be released? After the thiolysis step, what happens to the fatty acid that contains two less carbons? | In the thiolysis step, two carbons of the fatty acid are released. These two carbons are attached to a CoA and are actually an acetyl CoA unit. After an acetyl CoA is released from the fatty acid, the shorter fatty acid will then re-enter another beta-oxidation cycle. |
What is Acyl CoA? | It is the activated FA. The FA is converted into a high-energy derivative of CoA called Acyl CoA. |