The citric acid cycle begins with the
transfer of a two-carbon acetyl group from acetyl-CoA to the four-carbon acceptor compound (oxaloacetate) to form a six-carbon compound (citrate)
. The citrate then goes through a series of chemical transformations, losing two carboxyl groups as CO
2
.
Is citrate produced in the citric acid cycle?
Citrate is produced in the Krebs cycle
(also known as the citric acid cycle or TCA cycle) from the aldol condensation of oxaloacetate, the end product of a previous turn of the cycle, and acetyl-CoA (Figure 1) (36).
How is citrate citric acid made during cellular respiration?
Acetyl CoA links glycolysis and pyruvate oxidation with the citric acid cycle.
In the presence of oxygen, acetyl CoA delivers its acetyl group to a four-carbon molecule, oxaloacetate, to form citrate
, a six-carbon molecule with three carboxyl groups.
How is citrate metabolized?
Citrate is metabolized
by the Krebs cycle (citric acid cycle), mainly in the liver, but also in muscles and kidneys
.
How does citrate from the citric acid cycle affect glycolysis?
Citrate, the first product of the citric acid cycle, can also inhibit PFK. If citrate builds up, this is a sign that
glycolysis can slow down
, because the citric acid cycle is backed up and doesn't need more fuel.
Does citrate inhibit citric acid cycle?
The molecule produced in the reaction,
citrate, can also act as an inhibitor of the reaction
. Because citrate synthase is inhibited by the final product of the citric acid cycle as ATP, ADP (adenosine diphosphate) works as an allosteric activator of the enzyme as ATP is formed from ADP.
How does citrate from the citric acid cycle affect glycolysis quizlet?
How does citrate from the citric acid cycle affect glycolysis?
Citrate can inhibit phosphofructokinase by feedback regulation
.
How does citrate stimulate gluconeogenesis?
Activation effect is exerted on lipid biosynthesis through ACC, which produces malonyl-CoA, the first product of lipid biosynthesis, which, in turn, inhibits the CPT-1, the first enzyme of β-oxidation process.
Through F1,6BPase
, citrate stimulates gluconeogenesis.
What happens during citric acid cycle?
Figure: The citric acid cycle: In the citric acid cycle,
the acetyl group from acetyl CoA is attached to a four-carbon oxaloacetate molecule to form a six-carbon citrate molecule
. Through a series of steps, citrate is oxidized, releasing two carbon dioxide molecules for each acetyl group fed into the cycle.
Why citric acid cycle is called TCA cycle?
Citric acid is a so-called tricarboxylic acid, containing three carboxyl groups (COOH)
. Hence the Krebs cycle is sometimes referred to as the tricarboxylic acid (TCA) cycle.
Why is the citric acid cycle called a cycle quizlet?
Why is the krebs cycle called a cycle?
because the process starts over and over again
because the citric acid is reused as the 4 carbon compound over and over again.
How is citrate converted to bicarbonate?
During this procedure, citrate is administered to the circuit before the filter and chelates calcium, thus impeding coagulation.
Once citrate enters the circulation, it is metabolized to carbon dioxide and then bicarbonate on a 1: 3 basis
; thus, 1 mmol citrate yields 3 mmol carbon dioxide and then bicarbonate.
Where does the citric acid cycle occur?
Within the mitochondrion, the citric acid cycle occurs in
the mitochondrial matrix
, and oxidative metabolism occurs at the internal folded mitochondrial membranes (cristae).
How does citrate cause alkalosis?
Due to citrate metabolism causes intracellular acidosis
. As a result of intracellular acidosis compensation, decompensated metabolic alkalosis + respiratory acidosis and electrolyte imbalance may develop, blood transfusions may result in certain complications.
How are electrons extracted from the citric acid cycle?
The citric acid cycle is a series of chemical reactions that
removes high-energy electrons
and uses them in the electron transport chain to generate ATP. One molecule of ATP (or an equivalent) is produced per each turn of the cycle.
Does citrate activate glycolysis?
For example,
citrate directly inhibits the main regulators of glycolysis
, phosphofructokinase-1 (PFK1) and phosphofructokinase-2 (PFK2) [2,3], while it enhances gluconeogenesis by promoting fructose-1,6-biphosphatase (FBPase) [4].
What does dehydrogenase do in cellular respiration?
Dehydrogenase enzymes
remove hydrogen ions and electrons from intermediates of this cycle
, which are passed to the coenzyme NAD (forming NADH). The hydrogen ions and electrons are passed to the electron transport chain on the inner mitochondrial membrane. This occurs in both glycolysis and the citric acid cycle.
Why is citrate converted to isocitrate?
Thioester hydrolysis helps to displace equilibrium towards product formation
: Citrate is then isomerized to isocitrate, which is then decarboxylated to a-ketoglutarate. If citrate had not been isomerized to isocitrate, this decarboxylation would yield a branched carbon compound, much harder to metabolize.
What activates citrate synthase?
In the citric acid cycle, these remaining carbon atoms are fully oxidized to form carbon dioxide. Citrate synthase starts this process by
taking the molecules of acetate and attaching them to oxaloacetate
, which acts as a convenient handle as the carbon atoms are passed from enzyme to enzyme in the citric acid cycle.
Which are formed during one turn of the citric acid cycle?
Each turn of the cycle forms
one GTP or ATP as well as three NADH molecules and one FADH2 molecule
, which will be used in further steps of cellular respiration to produce ATP for the cell.
How does the formation of NAD+ differ between aerobic and anaerobic respiration?
text{NAD}^{+} {!} is
formed by a fermentation process in anaerobic conditions whereas in aerobic respiration it is formed by the breakdown of pyruvate into lactic acid or alcohol
.
Which of the following best describes how the citric acid cycle relates to glycolysis oxidative phosphorylation and chemiosmosis?
Which of the following best describes how the citric acid cycle relates to glycolysis, oxidative phosphorylation, and chemiosmosis?
Glycolysis produces pyruvate, which is converted to acetyl-CoA and enters the citric acid cycle.
Which steps in the oxidation of pyruvate produces carbon dioxide?
A carboxyl group is removed from pyruvate and released as carbon dioxide
. The two-carbon molecule from the first step is oxidized, and NAD+ accepts the electrons to form NADH. The oxidized two-carbon molecule, an acetyl group, is attached to Coenzyme A to form acetyl CoA.
Does citrate inhibit gluconeogenesis?
The citrate level inside the cells exerts a well- known function as a key regulator of energy production because
citrate inhibits and induces important strategic enzymes located at the entrance and/or at the exit of gly- colysis, TCA cycle, gluconeogenesis, and fatty acids syn- thesis
(Figure 1).
How are triglycerides converted to glucose?
Triglycerides are made up of three units of fatty acids and one unit of glycerol. Glycerol is a component of fatty acids in fats that is released when stored fat is metabolized for energy.
It then enters into the bloodstream and transferred to the liver
where it can be converted to glucose.
What is the role of citrate in fatty acid synthesis?
Citrate in the cytosol of the cell serves as
substrate in the ATP-citrate lyase reaction and activator of acetyl CoA carboxylase
* (5, 6). The acetyl CoA generated is carboxylated to form malonyl CoA en route to the synthesis of fatty acids.
