BCH2022 Study Guide - Final Guide: Carnitine O-Palmitoyltransferase, Acetyl-Coa, Carnitine

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25 May 2018

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Fatty Acid Oxidation (β-oxidation)

• Location: mitochondrial matrix of all tissues (except brain)

• Function: to produce energy

o Catabolic process

o To produce acetyl-CoA which enters citric acid cycle

o And NADH and FADH2: co-enzymes used in electron transport chain

• Lipids yield more ATP per molecule than glucose

o More important long term energy source

Fatty acid + 8 CoA + 7 NAD+ + 7 FAD → 8 Acetyl-CoA + 7 NADH + H+ +

7FADH2

• -ve ∆G’˚

• ^ equation for C16 (e.g. Palmitic acid).

o 7 cycles of β-oxidation → forms 8 acetyl CoA

Prior β-oxidation: Activation of fatty acid

• Occurs in cytoplasm

• Enzyme: fatty acyl-CoA synthetase

• Cofactors: CoA, ATP

o Produces AMP+ PPi

Fatty Acid Transport – Acyl-Carnitine Transport

• Required for entry of acetyl-CoA into mitochondria via carnitine shuttle

o Due to negative charge

• Carnitine: produced in liver and kidneys from lysine and methionine

• Carnitine acyltransferase I

o Located: outer mitochondrial membrane

• Carnitine acyltransferase II

o Located on inner membrane

• Small chain fatty acids don’t require carnitine, small enough to absorb/move

through membrane

Saturated Fatty Acids (OHOT)

1. (Step 1) Oxidation (dehydration)

• Cofactor: FAD: prosthetic group of enzyme accepts election →

FADH2

• Enzyme: Acyl-CoA dehydrogenase

2. Hydration

• Water added to double bond

• Enzyme: enoyl-CoA hydratase

3. Oxidation

• Cofactor: NAD+

o Accepts 2H+ → NADH

• Enzyme: hydroxyacyl-CoA Dehydrogenase

4. Thiolysis (cleavage)

• Requires reduced CoA (CoASH

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o Cuts off carbon back bone → cleaves off acetyl-CoA (two

carbons shorter)

• Enzyme: thiolase

Energy Yield Per Cycle

• 1 FADH2 → 1.5 ATP

• 1 NADH → 2.5 ATP

o Total 4 ATP

• 1 Acetyl CoA to CAC

o 3 NADH x 2.5 ATP / NADH → 7.5 AT

▪ Requires 3 cycles

o 1 FADH 2 → 1.5 ATP

o 1 GTP → 1 ATP

▪ Total 10 ATP

• E.g. ATP yield of palmitate (C16)

o 2 ATP required to activate fatty acids for mobilization into

mitochondria

o 7 FADH2 = 10.5 ATP

o 7 NADH = 17.5 ATP

o 8 acetyl CoA = 80 ATP

▪ Net yield: 106

Monosaturated Fatty Acids

• Need to break double bond in CIS to a trans bond

• Fats are good fuel for endurance events, not springs

Fate of acetyl Co-A

• Citric acid cycle

o Entry of acetyl-CoA into CAC requires oxaloacetate

▪ When oxaloacetate is depleted, acetyl-CoA is converted into

ketone bodies

• Frees coenzyme A for β-oxidation

• Ketone bodies

Comparing Energy Stores

Carbohydrates

Characteristic

Fats

Skeletal muscle

Stored in

Adipose tissue

Hydrates

Stored in … form

Anhydrous

< 1 day

Store … of energy

Weeks

Soluble

… in blood

Insoluble

Cytosol and mitochondria

Oxidised in …

Mitochondria

Anaerobically/aerobically

Produce ATP…

Aerobically

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Formation of Ketone Bodies (Ketogenesis)

• Location: liver mitochondria

• Formation of ketone bodies: β-hydroxybutyrate, acetoacetate and acetone

o Formed from excess acetyl-CoA produced by β-oxidation

• Occurs: after glycogen stores are exhausted in starvation

• Function: ketone bodies oxidised by other tissues (cardiac and skeletal

muscle) for energy

• Reverse reaction β-ketoacyl-CoA transferase occurs outside liver

• During fasting

o Low glucose/insulin

o Body uses fats as energy source

▪ Liver converts excess fatty acis to keton bodies → increase in

β-hydroxybutyrate and acetoacetate

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Related Questions

Question 18

The process that forms new glucose in the liver is called ...

	A.	glycogenolysis
	B.	Krebs cycle
	C.	lipolysis
	D.	gluconeogenisis
	E.	oxidative phosphorylation

Question 57

A person exercises in their âfat burning zoneâ for 4 hours at 35% VO₂peak. The O₂ cost of exercise at that work rate is 0.5L/minute. Following exercise the subject rewards himself with an ice-cream sundae (700kcal). The following statement is true(assume 5kcal/lit of O₂):

	A.	The subject is in neutral energy balance
	B.	The subject consumed fewer calories than they expended during exercise
	C.	The subject consumed more calories than they expended during exercise
	D.	Canât say

Question 52

The primary purpose of the citric acid cycle is...

		aerobic glycolysis
		gluconeogenesis using lactate
		the decarboxylation of carbon compounds to produce NADH.
		the shuttling of hydrogen ions through the inner mitochondrial membrane

Question 51

In aerobic ATP production, the role of oxygen is to...

		to keep the electron transport chain operational
		to accept electrons from the 3rd cytochrome and thereby oxidizing it so it can accept new electrons
		act as a oxidizing agent by accepting electrons from the electron transport chain and combining with hydrogen ions (protons)
		all of the above

Question 50

Glucose is necessary for fatty acid oxidation because...

		its derivative, pyruvate, is condensated with carbonic acid to form oxaloacetate, which in turn is a necessary carbon compound in the citric acid cycle
		it is needed to convert fatty acids to fatty acyl-CoA which in turn is oxidized to acetyl CoA
		glucose is decarboxylated into cytochrome oxidase which is a necessary intermediate in the citric acid cycle
		its derivative, acetyl CoA, is condensated with carbonic acid to form lactase, which in turn is a necessary carbon compound in the citric acid cycle

olivegoat873

1) In Eukaryotic cells, Glycolysis occurs in the __________,Pyruvate Oxidation and the Citric Acid Cycle occur in the ________,and the electron transport chain is in the _____________.

a) Mitochondrial matrix; Mitochrondrial inner membrane;Cytoplasm

b) Cytoplasm; Mitochrondrial inner membrane; Mitochondiralmatrix

c) Mitochrondrial inner membrane; Cytoplasm; Mitochondrialmatrix

d) Cytoplasm; Mitochondrial matrix; Mitochrondrial innermembrane

e) Mitochrondrial inner membrane; Mitochondrial Matrix;Cytoplasm

2) We can detect tyrosinase among thousands of other proteins ina mushroom extract (in a solution or in-gel) because:

a) Its bigger than other proteins

b) Its smaller than other proteins

c) Its more charged than other proteins

d) It reacts with a specific substrate to produce a coloredproduct

e) It converts a specific colored substrate to a colorlessproduct

3) The highest energy carrier (transfer molecule) in cellsis:

a) NADH

b) FADH2

c) ATP

d) GTP

e) Acetyl- coA

amaranthimpala502

Why does an electron have lower potential energy in an H-O bondthan in an O=O bond?

H has a higher electronegativity than O.

O=O is not stable.

O=O contains a double bond.

The electrons are closer to the oxygen atom in the H-O bond.

None of the answers are correct.

How is the energy from the electron transport chain used mostdirectly?

to form the bonds of a water molecule

to pump hydrogen ions across the mitochondrial inner membraneinto the mitochondrial intermembrane space

to join ADP with a phosphate

to decompose glucose into pyruvate

to rotate ATP synthase

Which process provides the energy needed to pump protons acrossthe mitochondrial membrane during oxidative phosphorylation?

the transfer of electrons in redox reactions

the breakdown of ATP to ADP

the rotation of the ATP synthase rotor

oxidation of isocitrate

None of the answers are correct.

What causes the ATP synthase rotor to spin?

the passing of electrons through ATP synthase

the movement of protons across the mitochondrial membrane

the movement of electrons across the mitochondrial membrane

the synthesis of ATP from ADP and a phosphate group

None of the answers are correct.

What of the following generates the proton-motive force duringoxidative phosphorylation?

buildup of NADH molecules at protein complex I

movement of H⁺ ions across the mitochondrial membraneduring electron transport

rotation of the ATP synthase rotor

joining of H⁺ ions with oxygen to form water

None of the answers are correct.

Suppose a microorganism invades a cell, causing damage to ATPsynthase. How would cellular respiration be affected?

Electrons could not be passed down the electron transportchain.

ADP could not be joined with a phosphate to form ATP.

Hydrogen ions could not be pumped into the mitochondrialintermembrane space.

The cell could not release any energy from the glucosemolecule.

Glucose could not be broken down into pyruvate.

Which molecules transport electrons from the citric acid cycleto the electron transport chain?

NADH and FADH₂

ATP and ADP

GTP and GDP

oxaloacetate and citric acid

None of the answers are correct.

Which type of reactions control the energy release from glucoseduring the citric acid cycle?

acid-base reactions

redox reactions

random reactions

All answers are correct.

None of the answers are correct.

What is the role of NAD⁺ in cellular respiration?

to receive electrons from the citric acid cycle and deliver themto the electron transport chain

to catalyze the synthesis of ATP from ADP

to accumulate in the mitochondrial intermembrane space tofacilitate ATP synthesis

to serve as a substrate to bind to acetyl-CoA at the beginningof the citric acid cycle

None of the answers are correct.

10.

Which molecule enters the citric acid cycle?

glucose

pyruvate

ATP

acetyl-CoA

None of the answers are correct.

apricotgoose897

BCH2022 Study Guide - Final Guide: Carnitine O-Palmitoyltransferase, Acetyl-Coa, Carnitine

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