The Cycles Flashcards
What structure is used to oxidize Pyruvate from glucose to make acetyl CoA?
Pyruvate Dehydrogenase complex (PDH ) complex
When is the PDH complex inhibited?
*when ample fuel is available in the form of fatty acids and acetyl-CoA
* when the cell’s ATP concentration and [NADH]/[NAD+] ratio are high,
When is the PDH complex stimulated?
*when energy demands are high
*greater flux of acetyl-CoA into the citric acid cycle is required.
In the Krebs cycle, what is the name of the enzyme that catalyses citrate to isocitrate, through the intermediary formation of the cis-aconitate?
Aconitase
By what process is Isocitrate converted to alpha-ketoglutarate?
Oxidative decarboxylation
What enzyme catalyzes the process of which Isocitrate converted to alpha-ketoglutarate?
Isocitrate Dehydrogenase
By what process is α-ketoglutarate is converted to succinyl-CoA and O2 ?
Oxidative Decarboxylation
What enzyme catalyzes the process of which α-ketoglutarate is converted to succinyl-CoA and O2 ?
α-ketoglutarate dehydrogenase complex
How much energy is released in the conversion of Succinylcholine-CoA to Succinate?
-2.9kJ/mol
What enzyme catalyzes the process of conversion of Succinylcholine-CoA to Succinate?
Succinylcholine coA synthesise
Fill in the blank. “Succinate is Oxidized to Fumarate by the enzyme _____”
Succinate Dehydrogenase
By what process is Fumarate converted to L-Malate and by what enzyme is this done?
Hydration - fumarase (fumarate hydratase)
What amount of Energy is given off when Malate is converted to Oxaloacetate?
29.7kJ/mol
Fill in the blanks.” ________ catalyzes the oxidation of L-malate to oxaloacetate”
NAD-linked L-malate dehydrogenase
What amount of Energy is given off whenCitrate is converted to Isocitrate
13.3 kJ/mol
At what stages of the Krebs cycle is CO2 released?
Through the oxidation of isocitrate and alpha- ketoglutarate
By what two processes can Oxaloacetate be produced?
*Carboxylation of Pyruvate
*Transamination of Aspartate
By what levels is the TCA regulated?
*The conversion of pyruvate into acetyl-CoA, the starting material for the cycle (the pyruvate dehydrogenase [PDH] complex reaction)
*The entry of acetyl-CoA into the cycle (the citrate synthase reaction).
By what substance is the enzyme alpha-ketoglutarate dehydrogenase complex inhibited by?
NADH & succinyl coA
What are the three factors that govern the rate of metabolites flow through the citric acid cycle?
*substrate availability,
*inhibition by accumulating products,
*allosteric feedback inhibition of early enzymes by later intermediates in the cycle
Which reaction is described as substrate limited?
Malate dehydrogenase reaction
True or False? ATP inhibits both citrate synthase and isocitrate dehydrogenase?
TRUE!!
Inhibition of Citrate synthase by ATP can be relieved by what substance?
ADP (allosteric activator of this enzyme)
A deficiency of what enzyme can cause lactic acidosis?
Pyruvate Dehydrogenase complex (PDH)
What is Oxidative Phosphorylation?
Oxidative phosphorylation is the process by which the energy stored in NADH and FADH2 is used to produce ATP.
What is the Oxidation Step?
*NADH +( H+) + O2 ——-> NAD+ + H2O
*FADH2 + O2 ———-> FAD + H2O
What is the Phosphorylation Step?
ADP + Pi ——-> ATP
What structures are found in the mitochondrial matrix?
-the pyruvate dehydrogenase complex
-the TCA cycle enzymes
-the fatty acid β-oxidation pathway
-the amino acid oxidation
Which enzyme can react with either NAD+ or NADP+?
Glutamate dehydrogenase
What are the 4 complexes found in the electron transport chain?
- NADH dehydrogenase
2.Succinatedehydrogenase/ FADH - Cytochrome c reductase
- Cytochrome oxidase
and ATP synthase (not a complex just to remember)
Which complexes act together to catalyze electron transfer from succinate to O2?
II , III & IV
Which complexes results in the transfer of electrons from NADH to O2?
I, III & IV
What is Chemiosmosis?
This is a process in which energy from a proton gradient is used to make ATP.
What is the name of the substance that allows free flow of protons across the inner mitochondrial membrane?
Dinitrophenol
Which drug inhibits Complex I ?
Rotenone, barbiturates(sedative)
Which drug inhibits Complex IV?
Cyanide, azides, carbon monoxid
What substance does drug Oligomycin?
ATP synthase
The drug Antimycin blocks which complex?
Complex III
In the working state, What processes occur?
Lipolysis ,glycolysis, gluconeogenesis ,ketogenesis (physical activity, dominated by adrenalin)
In the Fasted state, What processes occur?
Lipolysis ,gluconeogenesis, ketogenesis (dominated by glucagon and corticosteroids)
In the Fed state, What processes occur?
Liopgenesis, Glycolysis
Proteolysis occurs in what state?
Infected State
What is the major oxidative fuel in the liver?
Fatty Acids
Fill in the blanks. “Excess acetyl-CoA from oxidation of fatty acids not required by the liver is converted into _____.”
Ketone bodies
To which molecule does free fatty acids bind to?
Albumin
Where do most fatty acid synthesis take place?
In hepatocytes
What is the primary source of energy used by muscles at rest?
Free fatty acids from adipose tissue and ketone bodies from the liver.
By what pathway does the Heart gain most of its energy?
Oxidative Phosphorylation
What hormones are important regulators of the blood?
Insulin, Glucagon and Epinephrine
Which diabetes is insulin dependent ?
Type 1
Who discovered the Urea Cycle?
Hans Krebs and Kurt Henseleit in 1932
Where does the formation of Urea?
In the liver
What is the rate limiting step in the Urea cycle?
The conversion of ammonium ions to carbamoyl phosphate via the enzyme carbamoyl phosphate synthetase-1.
By what enzyme is Citrulline formation is done by what enzyme?
Ornithine Transcarbomylase
By what substance is Carbomoyl phosphate sythetase 1 activated by?
N-acetlyglutamate
Where is PDH complex located?
In the mitochondria
Fill in the blanks. “ ______ is the immediate precursor of both ammonia and aspartate”
Glutamate
What are examples of Ammonotelic animals?
Aquatic animals
Mamals or fish that excrete area via their urine is known as?
Urotelic animals
Which type of animals excrete amino nitrogen as uric acid?
Birds & Terrestrial reptiles
What is the normal blood level of Ammonia?
5-50 mol/L
Which disorder can be associated with a musty odour to the baby’s wet skin and urine, microcephaly ,albinism?
Pheynylketonuria (PKU)- Autosomal recessive
What substance produces this must odour?
Phenylacetate, one of the ketones produced
What enzyme is PKU a deficiency of?
hepatic enzyme phenylalanine hydroxylase (PAH), or cofactor, tetrahydrobiopterin (BH4)(rare)
What are alternative metabolites produced by PKU?
*phenylpyruvate
* phenylpyruvic acid
* phenyllactic acid
* phenylacetic acid
What is the first inborn error to be identified?
Alkaptonuria (black urine disease)
Fill in the blanks. Alkaptonuria is an inborn error of ______metabolism.
Tyrosine
The absence of which enzyme causes black urine disease?
Homogentisate oxidase
Maple syrup disease is caused by a deficiency in?
Branched-chain alpha- keto acid dehydrogenase (BCKDH) enzyme.
What amino acids are increased in Maple syrup disease?
Leucine, isoleucine and valine
How can one detect Maple syrup disease?
Gas chromatography
