5 ATP Flashcards
How can more energy (ATP) be provided after glycolysis?
citric cycle (kreb cycle) and ETC
only a small amount of energy available in glucose is captured in glycolysis
What is ATP?
- adenosine 5’-triphosphate
- nucleic acid
- building block of RNA
- the most commonly used energy currency
What kind of rxn is ATP hydrolysis? (exergonic or endogonic)
exergonic
What are exergonic reactions?
rxns that release energy
Would hydrolysing ATP into AMP or ADP release mroe energy?
if hydrolyse both = AMP will release more energy but not commonly used, perhaps has evolutionary reason
What is the cycle involving ATP that is the fundamental mode of energy exchange in biological systems?
ATP-ADP cycle
what do endergonic reactions do? example?
absorb energy
transferring a phosphate from ATP to glucose
used in glycolysis
What is an example of rxn coupling and what is coupled?
Glucose + ATP -> G6P + ADP
glucose -> G6P (endergonic)
ATP -> ADP + Pi (exergonic)
a thermodynamically unfavourable rxn can be driven by being coupled to a thermodynamically favourable one
Are ATP and ADP at equilibrium?
no
far from equilibrium for hydrolysis rxn
What happens when ATP level drops?
- the amount of fuel decreases
- the fuel loses its potency i.e. phosphorylation potential is diminished
phosphorylation potential = the ability to transfer a phosphate group from a high-energy molecule, like ATP (adenosine triphosphate), to another molecule.
basically using the hydrolyzing the ATP
less ATP = less hydrolyzing activity of it
What do living cells have to maintain high concentrations of ATP?
development mechanisms
What compounds can help form ATP from ADP?
compounds that have a higher phosphoryl transfer potential than ATP
can transfer their phosphoryl group to ADP = ATP
What 2 components in glycolysis have a higher phosphoryl transfer potential than ATP?
- phosphoenolpyruvate
- 1,3- bisphosphoglycerate
therefore these compounds can transfer their phosphoryl group to ADP
Where does glycolysis occur?
cytoplasm
Where does the citric acid cycle (kreb cycle) and ETC occur?
both in mitochondria
citric cycle = in the mitochondrial matrix
* except succinate dehydrogenase, which is located in the inner membrane
ETC = inner membrane
What does the double membrane of mitochondria lead to?
4 distinct compartments
* outer membrane
* intermembrane space (IMS)
* inner membrane
* matrix
What kind of environment is it in intermembrane space (IMS)?
- simlar environment to cytosol
- higher proton concentration (lower pH compared to the matrix)
What is located on the inner membrane? how do they increase their SA?
- location of ETC complexes
- convolutions called cristae serve to increase the surface area
What processes goes on in the matrix?
location of the citric acid cycle and parts of lipid and AA metabolism
Which has lower pH (higher proton conc): IMS or matrix?
IMS
What is the permeability of outer membrane and inner membrane?
outer: relatively porous; allows passage of metabolites
inner: relatively impermeable, has proton gradient across it
How is pyruvate transported to the matrix?
pyruvate generated in cytosol
transported to mitochondrial matrix by the mitochondrial pyruvate carrier
What is pyruvate converted to in the matrix? by what enzyme?
acetyl coA by pyruvate dehydrogenase complex
1 NADH is generated in the process
What enters the citric acid cycle?
Acetyl-coA
from pyruvate by pyruvate dehydrogenase complex
How many steps does one round of citric acid cycle involve?
8
What compounds are all channeled to the citric acid cycle?
compounds derived from the breakdown of carbs, fats, and proteins
to be oxidised to CO2 and water etc
Are the intermediates of this cycle used up?
the pathway is cyclic so they are not used up
for each oxaloacetate used (step 1), one is produced (step 8)
How many ATP/GTP is generated by each acetyl-coA?
1
for each acetyl-coA oxidised by the citric acid cycle, 1 ATP/GTP is generated
one cycle = 1 ATP
What is GTP?
alternate energy currency, first choice is always ATP
What type of phosphorylation is ATP generated from glycolysis and citric acid cycle?
substrate level phosphorylation
ATP generated from ADP and transfer of phosphate group from a substrate
What is produced from each acetyl coA oxidsed by the TCA cycle?
1 FADH2
3 NADH
What are FADH2 and NADH?
electron carriers that temporarily holds the energy of oxidation
they are dinucleotides
What is the relationship of NAD and NADH, NADP and NADPH
NAD and NADH (reduced form of NAD)
NADP and NADPH (reduced form of NADP)
NADP - is just NAD with additional phosphate
Where are NADPH and NADH produced?
NADPH = in the pentose phosphate pathway
NADH = from pyruvate oxidation to acetyl CoA
What do both NADH and FADH2 contain a pair of?
each contain a pair of electrons with **high transfer potential*
What are the electrons from NADH and FADH2 used for?
used to reduce oxygen to water = large amount of energy is liberated
this energy is used to form ATP
What is oxidative phosphorylation?
- process in which ATP is formed as a result of electrons from NADH and FADH2 transported to O2 by a series of electron carriers (collectively known as ETC complexes)
What does the ETC complexes contain?
a series of electron carriers
How many ETC complexes are there in ETC?
4
What are the names of the 4 complexes on the ETC?
- NADH: ubiquinone oxidoreductase
- Succinate dehydrogenase
- Ubiquinone: cytochrome c oxidoreductase
- cytochrome oxidase
what is complex I NADH:ubiquinone oxidoreductase?
- catalyzes the electron transfer from NADH to ubiquinone
- also acts as a proton (H+) pump, from matrix (N side) to the intermembrane space (P side)
electrons to ubiquinone and pumps proton to intermembrane space, happen at the same time
Whats the role of complex II: succinate dehydrogenase?
a single enzyme with dual roles:
* convert succinate to fumarate in the TCA cycle
* catalyze the electron transfer from succinate to ubiquinone via FADH2
What is happening in complex III ubiquinone:cytochrome C oxidoreductase?
Carries electrons from reduced ubiquinone from complex I and II to cytochrome C
What is happening in complex IV: cytochrome oxidase?
completes the sequence by transferring the electons from cytochrome c to O2, reducing O2 to water
What is the transfer pathway of electrons in the complexes?
Complex I: from NADH to ubiquinone
Complex 2: from succinate to ubiquinone via FADH2
complex 3: reduced ubiquinone carries the electrons to cytochrome c
complex 4: electrons from cytochrome C goes to O2 = makes water
complete 2 convert succinate to fumerate and FADH2 is made in the process and so it carries the electrons to go to ubiquinone
What are the 2 paths of electron transport in ETC?
For electrons from NADH
* complex 1 -> 3 -> 4
for electrons from FADH2
* complex 2 -> 3 -> 4
What is the proton gradient created by?
electron transport chain
* flow of electrons from NADH or FADH2 in ETC is highly exergonic (energy releasing)
* this energy released is used to pump H+ out of the matrix (N side) into the intermembrane space (P side)
* = creates a proton gradient
Which direction does the ETC complex pump protons?
from matrix (N side) to intermembrane space (P side)
makes the intermembrane space more acidic (higher H+)
For each pair of electrons transferred to O2, how many protons are pumped out of the complexes?
Complex I: 4 protons
Complex II: 4 protons
Complex IV: 2 protons
How many protons are pumped out in total by the 2 paths?
(NADH) complex I-> IV = 10H+
(FADH2) complex II-> IV 6H+
Why is the proton gradient important?
- generates a **proton motive force **to drive ATP synthesis by ATP synthase
- protons enter back to matrix via proton-specific channels in F0
- driven by chemical and electrcial gradient
- chemical gradient (more alkaline in matrix)
- electrical gradient (more negative in the matrix)
How is ADP and Pi transported into the matrix?
ADP from antiporter and Pi from symporter
ADP into matrix, ATP out to IMS
Pi in along with H+
What 2 functional units does ATP synthase complex contain?
F1 - soluble complex in the matrix
* individually catalyzes the hydrolysis of ATP (by itself can break ATP, but work tgt with F0 can make can phosphorylate ADP -> ATP)
F0 - integral membrane complex
* transport protons from intermembrane space to matrix, dissipating the proton gradient
* energy transferred to F1 to catalyze phosphorylation of ADP
what does proton translocation causes in ATP synthase?
- causes a rotation of F0 subunit in the central shaft y
- this causes a conformation change within all the 3 αβ pairs in F1
- the conformational change in one of the 3 pairs promotes condensation of ADP and Pi into ATP
What is the amonut of ATP produced by the 2 pathways of ETC?
NADH pathway complex 1to 4 -> 2.5 ATP
FADH2 pathway complex 2 to 4 -> 1.5 ATP
Summary of electron transport and ATP made (chemical equation)
What is the differnce between substrate level and oxidiative phosphorylation?
Oxidative = Any ATP generated from FADH2 or NADH
Substrate-Level Phosphorylation = Direct transfer of a phosphate group from a phosphorylated substrate to ADP.
What is the number of ATP produced by one NADH or one FADH2
1 NADH = 2.5 ATP
1 FADH2 = 1.5 ATP
What is the final yield of ATP from NADH in glycolysis?
3 or 5
Why is the final yield of ATP from NADH in glycolysis either 3 or 5
Glycolysis makes 2 pyruvate 2 NADH and 2 ATP in the cytosol
the NADH cannot directly enter the ETC at complex I
so 2 methods are used to feed the electrons from NADH from cytosol into the mitochondria
the number of ATP generated depends on which pathway is used
what are the 2 pathways used to feed 2NADH from cytosol into mitochondria?
malate-aspartate shuttle
glycerol-3-phosphate shuttle
How is the malate-aspartate shuttle used?
- used in liver, kidney and heart for transporting cytosolic NADH into the mitochondrial matrix
- makes 5 ATP out of 2 NADH
How is the glycerol-3-phosphate shuttle used?
- this shuttle operates in the skeletal muscles and brain
- dihydroxyacetone phosphate (DHAP) is converted to glycerol-3-phosphate by accpeting the electrons from NADH
- this reaction is facilitated by the cytosolic form of glycerol-3-phophate dehydrogenase
- then the mitochondrial form of glycerol 3-phosphate dehydrogenase transfers the electrons from glycerol 3-phosphate and form FADH2
- and FADH2 brings the electrons to ubiquinone
2NADH are converted to 2FADH
and 1FADH only produces 1.5ATP
