CH 3, Part 5-7; CH 4, Part 1 Flashcards
1
Q
Describe the process of “aerobic” glycolysis
A
- breakdown of glucose with oxygen
(1) pyruvate and NADH enter into the mitochondria
(2) they will be consumed in the electron transport chain which requires oxygen- pyruvate is reduced into lactose and NADH is oxidized back into NAD to be fed back into glycolysis
- independent of oxygen, electron transport chain is absent
2
Q
Pyruvate to Acetyl-CoA
A
- from glycolysis ATP, NADH, and pyruvate
- ATP is consumed and NADH and pyruvate go into the mitochondria
- pyruvate is then oxidized to acetyl CoA and will run through the Krebs Cycle
- oxidation rxn is connector rxn btwn glycolysis (cytoplasm) and krebs cycle (mitochondrial matrix)
3
Q
Krebs Cycle
A
- series of oxidation reactions
- isocitrate dehydrogenase is rate limiting enzyme
(1) acetyl CoA joins with oxaloacetate (4-C molecule), releasing CoA group and forms citrate (6-C molecule)
(2) citrate converted to isomer, isocitrate- 2 steps: removal and addition of water molecule
(3) isocitrate oxidized by isocitrate dehydrogenase (enzyme) and releases molecule of carbon dioxide - leaves behind alpha-ketoglutarate (5-C molecule)
- NAD reduced to form NADH
(4) alpha-ketoglutarate oxidized by NAD with help of alpha-ketoglutarate dehydrogenase (enzyme) - NAD is reduced to NADH and CO2 is released
- remaining 4-C molecule picks up Coenzyme A to form succinyl CoA
(5) CoA of succinyl CoA replaces by phosphate group - phosphate group transferred to ADP to make ATP
- some cells use GDP instead of ADP to form GTP
- 4-C molecule produced called succinate
(6) succinate is oxidized to form fumarate (4-C molecule) - 2 hydrogen atoms (w/ e-) transferred to FAD to produce FADH2
- enzyme that carries out rxn embedded in inner membrane of mitochondria so FADH2 can transfer electrons directly to electron transport chain
(7) water is added to fumarate, converting it to malate (4-C molecule)
(8) oxaloacetate (starting 4-C compound) regenerated by oxidation of malate - another molecule of NAD is reduced to NADH
Products:
- 2 steps: removal and addition of water molecule
- makes ATP indirectly by way of generating NADH and FADH2
- electron carries will deposit electrons into electron transport chain to drive synthesis of ATP molecules through oxidative phosphorylation
(1) 2 Cs enter from acetyl CoA –> 2 molecules of CO2
(2) 3 NADH and 1 FADH2 are generated
(3) 1 molecule of ATP/GTP produced
- electron carries will deposit electrons into electron transport chain to drive synthesis of ATP molecules through oxidative phosphorylation
4
Q
Explain how the electron transport chain works to produce ATP
A
- hydrogens from the Krebs Cycle are used in electron transport chain to ultimately make ATP
- electrons from NADH’s hydrogens travel through series of 4 complexes and get pumped from mitochondrial matrix to intermembrane space
- how many ATP are produced?
- First Pump (I): 4 H+
- Second Pump (III): 4 H+
- Third Pump (IV): 2 H+
- 4 H+ required to produce and transport 1 ATP
- NADH (10 H+) = 2.5 ATP
- FADH2 (6 H+) = 1.5 ATP
5
Q
Understanding NADH
A
- NADH is the fuel of all rxns
- purpose of all NADH from glycolysis in matrix is to give hydrogens to complex I
- electrons from hydrogens will then be transported down chain of complexes in a series of oxidation rxns
- every NADH that goes into complex I = 10 hydrogen ions in intermembrane space
- 1 NADH = 10 H+ = 2.5 ATP
6
Q
The Complexes
A
- series of 4 proteins imbedded in the inner membrane of the mitochondria
- job is to pump hydrogen ions from matrix to intermembrane space
- complex I oxidizes 2 NADH back to 2 NAD
- reduced –> holds onto 2 hydrogen electrons and leave 2 hydrogen ions in matrix
- coenzyme Q oxidizes complex I and energy from oxidation rxn pumps 4 hydrogen ions from matrix to intermembrane space
- complex III oxidizes coenzyme Q (complex II is skipped)
- reduced –> no hydrogen ions pumped
- cytochrome C oxidizes complex III and energy from exergonic rxn pumps 4 hydrogen ions from matrix to intermembrane space
- complex IV oxidizes cytochrome C
- reduced –> no hydrogen ions pumped
- oxygen atom oxidizes complex IV and is reduced; combines with 2 hydrogen ions from matrix to form water
- energy from rxn pumps 2 more hydrogen ions from matrix to intermembrane space
7
Q
Hydrogen Gradient
A
- the purpose of the electron transport chain is to pump hydrogen ions that are in the mitochondrial matrix out into intermembrane space
- the “pumping” is performed by four complexes
- for every NADH that goes into CI, 10 hydrogen ions are pumped into intermembrane space
- this creates a net flow and hydrogen ion gradient
- for every NADH that goes into CI, 10 hydrogen ions are pumped into intermembrane space
8
Q
Oxygen
A
- oxygen removes electrons from Complex IV and allows for electrons to be continuously shuttled through the complexes of the electron transport chain
- without oxygen, the ETC (and thus oxidative phosphorylation) cannot exist
- if electrons cannot be removed from CIV due to a lack of oxygen, the electrons will begin to accumulate excessively in all complexes
- this creates a jam and the system can no longer pump hydrogen ions
- if the cell’s ability to receive oxygen is removed, it cannot keep its electron transport chains going and it will die
- cells need oxygen to make ATP via oxidative phosphorylation in the mitochondria
- without oxygen, there is no ability or cells to make ATP and therefore they will die—this is why oxygen is fundamental to human life
- cells need oxygen to make ATP via oxidative phosphorylation in the mitochondria
9
Q
Oxidative Phosphorylation
A
- a series of oxidation reactions through the electron transport chain
- these reactions ultimately allow for the phosphorylation of ADP back to ATP
- the process by which our mitochondria make ATP
10
Q
How and why a cell transitions between using only aerobic glycolysis to both aerobic and anaerobic glycolysis
A
- As long as enough oxygen comes to the muscle cells, they will use aerobic glycolysis because it is the most efficient form of resynthesizing ATP
- However, as the muscle cells continue to run glycolysis at an increasing rate to make more NADH and pyruvate for the mitochondria, there is not enough oxygen to change NADH to ATP
- NADH and pyruvate will accumulate in the cytosol due to a lack of a concentration gradient when oxygen is no longer available to oxidize Complex IV
- the NADH and pyruvate in the mitochondria allosterically activate acetate dehydrogenase which reduces pyruvate to lactate
- anaerobic “fast” glycolysis begins and NADH is oxidized to NAD
- the NADH and pyruvate in the mitochondria allosterically activate acetate dehydrogenase which reduces pyruvate to lactate
11
Q
Describe the difference between passive and active transport
A
- passive transport: net flux is down the electrochemical gradient
- active transport: net flux is up the electrochemical gradient
12
Q
Passive Transport
A
two requirements:
- molecules need to move from a high concentration to a low concentration
- no energy is required ever
types:
- simple diffusion
- facilitated diffusion
- diffusion through channels (pores)
- osmosis
13
Q
Active Transport
A
types:
- primary active transport
- secondary active transport
- vesicular transport
14
Q
Simple Diffusion
A
- a type of passive diffusion when a molecule spontaneously moves past the plasma membrane from high-to-low concentrations with no energy and does not require an integral protein
- a type of diffusion typically used by small, non-polar molecules
- ex: O2, CO2
15
Q
Diffusion Through Channels
A
- a type of passive diffusion when a molecule/ion travels through a channel following a high-to-low gradient
- channels or pores are incredibly specific to one particular molecule or ion
- ex: aquaporins, ion channels
- ions or molecules will always be charged or incredibly large
- ex: sodium, potassium, etc.
