Aerobic Metabolism Flashcards
What are the 3 stages of catabolism of sugars,fats and amino acids?
- Glycolysis, b-oxidation,transamination
Glucose,fatty acids amino acids —-> Pyruvate —> CH3-C=O - Kreb’s cycle or tricarboxylic acid (TCA) cycle
2CO2 molecules produced and 2H molecules produced - Oxidative phosphorylation
2H + O ——> H20 + ATP
Definition of krebs cycle?
Location?
Tissues involved?
Definition: oxidation of acetyl CoA to CO2 and water
Location: Mitochondrial matrix
Tissues:all tissues with mitochondria
(not red blood cells or white muscle fibres)
Function of krebs cycle
- energy trapping
- biosynthesis of intermediates
Describe the link reaction from glycolysis to TCA?
Conversion of Pyruvate to Acetyl CoA
CH3COCOOH + CoASH + NAD+ —————-> CH3 CO S CoA + CO2 + NADH + H+
Pyruvate + coenzyme A (Not attached to acetyl) + oxidised NAD —> Acetyl coenzyme + CO2 + ReducedNAD
Catalysed by enyme- Pyruvate dehydrogenase (use with NAD+)
How is acetyl coenzyme A formed from co enzyme A?
Coenzyme A forms thioester bonds (R−S−C−R) with carboxylic acids
R−S−C−R
Forms a high energy bond -SH
What is the first reaction in the TCA cycle?
**Condensation reaction
**Acetyl CoA + Oxaloacetate ——> Citrate
Catalysed by: Citrate synthase
From 4 Carbon molecule to 6 Carbon molecule
What is the 2nd reaction in the TCA cycle?
Isomerisation
Citrate —>Isocitrate
Catalysed by: Aconitase
What is the 3rd reaction in the TCA cycle?
First loss of CO2 - IMPORTANT (MUST KNOW)
- Loses Carbon (6C to 5C)
- Catalysed by Isocitrate dehydrogenase
- Isocitrate ——————> a-Ketoglutarate (2-oxo glutarate)
- NAD+ in
- NADH and H+ and CO2 produced
What is the name of the type of molecule produced in the 3rd reaction?
Different types of this moleucle?
Dicarboxylic acid
Oxalic acid - 2 Carboxyl groups bonded to each other
Malonic acid - 2 Carboxyl groups bonded to a (CH2)
Succinic acid - 2 Carboxyl groups bonded to 2 CH2
Glutaric acid - 2 Carboxyl groups bonded to 3 CH2
What is the 4th reaction in the TCA cycle?
Second loss of CO2
a-Ketoglutarate (2-oxo glutarate) ———->Succinyl CoA
5 carbons —————————————-> 4 carbons
Cataylsed by a-ketoglutarate dehydrogenase
coenzyme (CoAsh) introduced
NAD+ in
NADH + H+ AND CO2 produced
What is the 5th reaction in the TCA cycle?
(5) Trapping thioester bond energy as GTP
Catalysed by Succinyl-CoA synthetase - used to form succinate
Succinyl CoA —–> Succinate
GDP + Pi ——-> GTP + CoAsh
What is the 6th reaction in the TCA cycle?
(6) Conversion of succinate to fumarate
Succinate —————> Fumarate
Catalysed by Succinate dehydrogenase
FAD in
FADH2 PRODUCED
What is the 7th reaction in the TCA cycle?
(7) Conversion of fumarate to malate
Fumarate + H20 ——-> Malate
Catalysed by Fumarase
What is the 8th reaction in the TCA cycle?
Malate ————-> Oxaloacetate
Catalysed by Malate dehydrogenase
NAD+ IN
NADH + H+ OUT
Complete overview of the TCA Cycle
How is this ATP produced?
The re-oxidation of NADH to NAD+ and FADH2 to FAD via the Electron Transport Chain results in synthesis of ATP from ADP and Pi (Oxidative Phosphorylation)
Energy yields of TCA cycle
3 enzyme reactions produce NADH and H+
1 enzyme reaction produces FADH 2
1 enzyme reaction produces GTP
ATP yields =
3 x 2.5 (2.5 ATP for every NADH)
1 x 1.5 (1.5 ATP for every FADH2)
1 x GTP
______
10 ATP
Which are three key stages?
Describe them?
Why are they important?
3 enzyme steps are highly exergonic & irreversible:
**MUST REMEMBER **
1. citrate synthase
2. isocitrate dehydrogenase
3. α-ketoglutarate dehydrogenase
STEPS 1,3,4
What are oxidation reactions?
- Adding O2 directly to the molecule (rare event in metabolism)
- Removing an electron e-
- Remove a pair of hydrogen atoms
oxidative phosphorylation definition
Location?
Tissue?
Function?
Definition: process for the transfer of H atoms to oxygen
Location: mitochondria
Tissues: most tissues & cell types
(not red blood cells)
Functions: ‘energy trapping’
direct phosphorylation of ADP to produce ATP
Describe the structure of the mitochondria and where oxidative phosphorylation takes place?
the inner compartments of the mitochondria is where oxidative phosphorylation
Components of the ETC are ‘buried’ in the inner mitochondrial membrane
Structure of NADH
(Need to recognise)
remove postive charge
shift e-s around
add h atom on top
More Hs
Structure of NAD+
(Need to recognise)
NAD+ is the one with a plus above the N
Less Hs
What is the ETC and where is it located?
**Electron Transport chain **
* collection of protein complexes found on the inner membrane of mitochondria
* The electron transport chain is made up of a series of membrane proteins/ electron carriers
* They are positioned close together which allows the electrons to pass from carrier to carrier
* The inner membrane of the mitochondria is impermeable to hydrogen ions so these electron carriers are required to pump the protons across the membrane to establish the concentration gradient
Components of the ETC are ‘buried’ in the inner mitochondrial membrane
How does oxidative phosphalation take place and why?
Occurs within matrix
High energy intermediates from krebs cycle : NADH and FADH2 are used
The re-oxidation of NADH to NAD+ and FADH2 to FAD via the Electron Transport Chain results in synthesis of ATP from ADP and Pi (Oxidative Phosphorylation)
High energy intermediates: NADH and FADH2
This reoxidation occurs through the** Stepwise transfer of H atoms to O2 **
Why oxygen important in oxidative phosphorlation?
Oxygen is the terminal electron acceptor in electron transport chain in order to generate ATP
- Oxygen is the final hydrogen ion and electron acceptor.
- The oxygen combines with the hydrogen ions and electrons to form water.
What are components of the elctron transport chain?
**H pair acceptors: **
* Flavin cofactors
* Coenzyme Q CoQ
Electron acceptors:
* Iron sulphur proteins
* Cytochrome proteins
Describe the process of oxidative phosphotlation?
How is the ECT used?
Re oxidation of high energy intermediates: FADH2 and NADH
- Hydrogen atoms are donated by reduced NAD (NADH) and reduced FAD (FADH2) from the Krebs Cycle
- Hydrogen atoms split into protons (H+ ions) and electrons
- The high energy electrons enter the electron transport chain and release energy as they move through the electron transport chain
- The released energy is used to transport protons across the inner mitochondrial membrane from the matrix into the intermembrane space
- A concentration gradient of protons is established between the intermembrane space and the matrix
- The protons return to the matrix via facilitated diffusion through the channel protein ATP synthase
- The movement of protons down their concentration gradient provides energy for ATP synthesis
Oxygen acts as the ‘final electron acceptor’ and combines with protons and electrons at the end of the electron transport chain to form water
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How is ATP Produced from ATP SYNTHASE?
Overall Oxidative phosphorlyation equation?
NADH + H+ ——-> NAD+ + H2O
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What is Flavin Cofactor Reoxidation?
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What is Inhibitors?
What is uncouplers of oxidative phosphorylation?
What is the ATP Yield for oxidative phospholation?
ATP yields:
NADH reoxidised - per 2.5 ATP
FADH2 =1.5 ATP
Balance sheet for ATP production from complete oxidation of 1 molecule of glucose
Glycolysis 2 x ATP
2 x NADH from pyruvate dehydrogenase 5 x ATP
TCA cycle 2 x ATP (via GTP)
6 x NADH from TCA cycle 15 x ATP
2 x FADH2 from TCA cycle 3 x ATP
2 x NADH from glycolysis *5 or 3 x ATP
32 or 30 x ATP
What is the effect of ATP on O2?
Control:
increased [ADP] increases rate of O2 uptake
increased [ATP] decreases O2 uptake
