BISC EXAM 2-cell respiration Flashcards
Glycolysis
what is cellular respiration and how many phases are there?
a series of chemical reactions, some requiring O2, some do not, to produce the bulk of cellular energy in the form of ATP. there are 4 phases
what are the 4 phases of cellular respiration?
- glycolysis
- pyruvate oxidation
- the Krebs cycle
- oxidative phosphorylation
anaerobic respiration
without oxygen, less energy made but faster
aerobic respiration
needs oxygen, more energy gained but slower
What is glycolysis and where does it happen?
10 constitutive reactions that take place in the cytosol of a cell and catabolize a single molecule of glucose (a six-carbon sugar) into two molecules of pyruvate (a three-carbon sugar). ATP and the electron carrier NADH are produced too. happens for aerobic and anaerobic respiration
what are the two common electron carriers?
NADH, derived from niacin (Vitamin B3) and oxidized to become NAD+
FADH2, derived from riboflavin (Vitamin B2) and oxidized to become FADH (-1 electron) and FAD(-2 electrons)
An atom/ molecule is oxidized when
it loses an electron.
An atom/ molecule is reduced when
it gains an electron.
what is produced at the end of glycolysis?
2 molecules of pyruvate (pyruvic acid)
2 NADH molecules (to be used in oxidative phosphorylation later on)
4 ATP molecules (however, 2 are used in the first phase of glycolysis, and thus, the net result of glycolysis is 2 ATP molecules)
Which reactions make up the “Investment” Phase of glycolysis ? and how many atp are made + final products
1-5, requires 2 atp, 2 G3P molecules produced to double reactions in phases 6-10
Which reactions make up the “Pay-Off” Phase of glycolysis? and how many atp are made + final products
6-10, produces 4 atp, 2 pyruvate at the end
which glycolysis reactions are irreversible?
1, 3, and 10
glycolysis reaction 1:
reactants and products
catalyzing enzyme
number of carbon atoms for reactants and products
- glucose + ATP = glucose 6-phosphate + ADP
- catalyzed by hexokinase
- 6 carbons for both
glycolysis reaction 3:
reactants and products
catalyzing enzyme
number of carbon atoms for reactants and products
- fructose-6-phosphate + ATP = fructose-1,6,-bisphosphate + ADP
- catalyzed by phosphofructonkinase
- 6 carbons
glycolysis reaction 10:
reactants and products
catalyzing enzyme
number of carbon atoms for reactants and products
- phosphoenolpyruvate + ADP → pyruvate + ATP
- catalyzed by pyruvate kinase
- 6 carbon to 2 3 carbon pyruvate molecules
what is a kinase?
an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule (phosphorylates)
what happens to pyruvate made during glycolysis if the cell has no oxygen present?
pyruvate will be used to create lactate (happens in very active muscle tissue that doesn’t get a lot of O2)
OR
ethanol/fermentation (common with yeast)
for both-NADH is oxidized to NAD+
what is pyruvate oxidation and where does it happen?
pyruvate travels in after glycolysis at the junction of the cytosol and mitochondria(l outer membrane) then transported into the mitochondria via a pyruvate shuttle, but it can not be oxidized to (Acetyl-CoA) until it is the matrix. Acetyl-CoA is a two-carbon molecule with the large coenzyme A attached.
what is produced in the process of pyruvate oxidation?
In the process of removing a carbon from pyruvate, Carbon Dioxide (CO2) is produced and eventually removed from the cell (and the body via exhalation).
An additional NADH molecule is also produced during this reaction.
what are co-enzymes?
are a class of molecule typically derived from vitamins
The Krebs Cycle (also known as the Citric Acid Cycle, or TCA Cycle: what is it and where does it happen
occurs in the matrix. This process combines Acetyl-CoA with oxaloacetate, a 4-carbon sugar, to form citrate/ citric acid, a 6-carbon sugar, which then undergoes a series of chemical changes over the course of eight cyclical reactions.
Citric Acid/ Citrate, produced after the first reaction
Oxaloacetate, produced after the eighth reaction (combines with Acetyl-CoA to form Citric Acid/ Citrate)
what is produced by the end of the krebs cycle?
6 NADH molecules (to be used in oxidative phosphorylation later on)
2 FADH2 molecules (to be used in oxidative phosphorylation later on)
4 CO2 molecules (which are exhaled as a byproduct)
2 ATP molecules
what is oxidized and reduced in the krebs cycle?
NAD+ is reduced to NADH
FAD is reduced to FADH2
nothing oxidized?
what krebs cycle reactions are irreversible?
1, 3, and 4
krebs reaction 1:
reactants and products
catalyzing enzyme
oxaloacetate + acetyl-CoA → citrate
catalyzed by the enzyme citrate synthase.
krebs reaction 3:
reactants and products
catalyzing enzyme
isocitrate + NAD+ → alpha-ketoglutarate + NADH + CO2
catalyzed by the enzyme isocitrate dehydrogenase.
krebs reaction 10:
reactants and products
catalyzing enzyme
alpha-ketoglutarate + NAD+ → succinyl-CoA + NADH + CO2
catalyzed by the alpha-ketoglutarate dehydrogenase complex.
what happens during the krebs cycle when the cell has enough of the products from each irreversisble reaction?
As with the previous two reactions, the products from this reaction act directly on the enzyme complex to inhibit the reaction when sufficient quantities of the products exist within the cell (mitochondria).
is the krebs cycle anabolic or catabolic
Trick: it’s amphibolic, These pathways can be anabolic (for example, in the case of amino acid synthesis) or catabolic (for example, in the case of fatty acid breakdown).
Oxidative Phosphorylation: what is it and where does it happen
takes place at the Electron Transport Chain, which consists of four membrane-bound protein complexes and the speciafinallized protein pump ATP Synthase, embedded in the mitochondrial Cristae membrane. All the electron carriers accumulated from the previous phases of anaerobic and aerobic respiration are now “cashed in” to power the production of the majority of ATP produced from cellular respiration (32 ATP molecules result from this phase)
what is the final electron acceptor involved in oxidative phosphorylation?
Oxygen serves as the final “electron acceptor” in the chain, effectively providing the “motivating force” for electrons to move through each complex(energy harnessed through reducing oxygen to water). The energy generated from this electron flow allows for protons (H+) to be pumped against their concentration gradient across the cristae membrane
what is the net reaction of oxidative phosphorylation?
2NADH + 2H+ + O2 → 2NAD+ + 2H2O
what is the MAJOR final result of cellular respiration (all 4 stages)?
32 atp for each initial glucose (technically 36 but NET is 32)
describe protein complex 1 under oxidative phosphorylation
Complex I (NADH Dehydrogenase).
NADH is oxidized to NAD+. This redox reaction results in:
2 electrons (e-) transferred to the next complex in the chain.
4 protons (H+) being pumped from the matrix to the intermembrane space (cristae lumen)
describe protein complex 2 under oxidative phosphorylation
Complex II (Succinate Dehydrogenase).
Succinate is oxidized to Fumarate, and in turn, FAD is reduced to FADH2.
This redox reaction results in 2 electrons (e-) being transferred to the next complex in the chain via a lipid-based electron carrier known as Coenzyme Q (CoQ), or ubiquinone.
No protons are pumped across the cristae membrane at this complex.
describe protein complex 3 under oxidative phosphorylation
Complex III (Cytochrome C Reductase).
Cytochrome C, another electron carrier, is reduced when it accepts the electrons from Coenzyme Q. This redox reaction results in:
2 electrons (e-) transferred to the next complex in the chain.
4 protons (H+) being pumped from the matrix to the intermembrane space (cristae lumen)
describe protein complex 4 under oxidative phosphorylation
Complex IV (Cytochrome C Oxidase).
The Cytochrome C that came from complex III is now oxidized, and these 2 electrons are used to reduce Oxygen (O2) to water (H2O).
In addition, 2 protons (H+) are pumped from the matrix to the intermembrane space (cristae lumen)
what structure is after protein complex 4 under oxidative phosphorylation?
ATP Synthase
what happens at the ATP Synthase complex?
the flow of electrons is necessary to generate the steep proton (H+) gradient required to “power” the ATP Synthase protein.
For every 3 protons (H+) that diffuse through the ATP Synthase protein channel, 1 ATP molecule is synthesized from ADP and Pi.
are ATP synthase complexes in only eukaryotes?
you should be aware that ATP Synthases exist in all cells- including prokaryotic cells- and that they are found in the plasma membrane and perform the same function as eukaryotic ATP Synthases.
For every individual glucose molecule oxidized through all three major phases of cellular respiration (glycolysis, the Krebs Cycle and oxidative phosphorylation), the following reactants are used and the following products are generated:
36 ATP molecules produced (approximation)
10 NADH molecules used (in oxidative phosphorylation)
2 NADH produced in one round of glycolysis
2 NADH produced in pyruvate oxidation
6 NADH produced in one round of the Krebs Cycle (2 Acetyl-CoA input)
2 FADH2 molecules produced (at the second protein complex in the ETC)
6 CO2 molecules produced
2 CO2 produced during pyruvate oxidation
4 CO2 produced during the Krebs Cycle
what type of energy is a concentration gradient
potential energy
what happens if you uncouple ATP synthesis and the electron transport chain
can disrupt the synthesis of ATP without interrupting the flow of electrons via the electron transport chain: the reverse is not true. Electron movement is required to generate the proton gradient necessary to promote ATP synthesis.
An example of an uncoupling agent is the chemical dicoumarol, which is used to treat deep vein thrombosis.
what is chemiosmosis?
Chemiosmosis refers to the movement of hydrogen ions across the membrane via ATP synthase
where does the ATP produced from cellular respiration go?
- vast majority of the ATP produced from oxidative phosphorylation will be used by other organelles in the cell, will need to be transported out of the mitochondria.
- relocated out of the mitochondria via an antiporter called Adenosine Nucleotide Translocase. This antiporter also brings in more ADP to allow oxidative phosphorylation to continue.
-Additionally, Phosphate Translocase is a symporter that moves inorganic phosphates into the mitochondrial matrix to also contribute to ATP synthesis.
