Ch 13 - 14 Flashcards
Define Oxidative phosphorylation (identify steps and describe amount of ATP generated by single molecule of glucose when fully oxidized)
Oxidative phosphorylation: membrane-based process that creates ATP via the transfer of electrons from food molecules (and active carriers to molecular oxygen)
Generates 30 molecules of ATP for 1 molecule of glucose
Step 0: pyruvate and fatty acids enter mitochondrial matrix to produce acetyl CoA which is tehn metabolized into NADH and FADH2
Step 1: NADH and FADH2 (produced from the citric acid cycle) donate electrons (are oxidized) to the electron-transport chain
Step 2: As electrons are passed through the chain, reducing and oxidizing each unit involved in electron-transport, it reaches molecular O2.
Step 3: The process of reduction and oxidization releases energy that transports H+ across the inner mitochondrial membrane
Step 4: The H+ concentration gradient drives the protein complex ATP synthase to create ATP
Compare and contrast oxidative phosphorylation and glycolysis
Oxidative phosphorylation:
- needs O2 (ultimate electron acceptor –> ensures that ETC components are oxidized so that they can get reduced again)
- needs membrane (to set up proton gradient)
Glycolysis:
- does not need O2
- does not need membrane
Describe mitochondrial structure, and list factors that influence mitochondrial size, shape and number
- Mitochondrial matrix
- mix of enzymes involved in pyruvate oxidation and fatty acids involved in citric acid cycle - Outer mitochondrial membrane
- permeable to molecules of 5000 daltons or less - inner mitochondrial membrane
- folded into cristae
- contains electron-transport chain proteins + ATP synthase - inter membrane space
- contains many enzymes that use ATP to phosphorylate nucleotides
- can contain high concentration of H+
Factors:
- location
(mitochondria in sperm wrap around the flagellum while mitochondria in cardiac cells are not)
- energy demands
(higher numbers of mitochondria are found in organs / muscles that are most active)
List the respiratory enzyme complexes and describe how they establish a proton gradient across the inner mitochondrial membrane
- Complex 1 - NADH Dehydrogenase
- Cytochrome c reductase
- Cytochrome c oxidase
ubiquinone and cytochrome c –> mobile electron carriers that ferry electrons from one complex to another
The energy released during the redox reaction of the complexes fuels the “pumping” of protons across inner mitochondiral membrane (establishes a protongradient)
Force that drives momvement of electrons within and between ETC?
Redox Potential
- electrons gravitate towards molecules with the largest redox potential (or highest affinity for electron) –> ensures that the complexes become oxidized in preparation for more electrons to come
Describe how protons are “pumped” across the inner mitochondrial membrane at the molecular level
Movement of Protons:
1. when electron carriers are reduced, it takes in an electron and a proton
2. when it is oxidized it will release both an electron and a proton
3. Proton is passed onto water and moves onto the other side of the membrane (granted that the electron carriers are oriented in such a way to take in hydrogen from 1 side and release it to the other side)
Name the subunits of ATP synthase protein, and describe how this protein uses a proton gradient to generate ATP
- Transmembrane H+ carrier
- Central stalk
- F1 ATPase head
- Peripheral stalk
(1 revolution of ATP synthease produces 3 molecules of ATP)
Mechanism behind ATP synthesis:
1. Proton bind to the transmembrane H+ carrier
2. Conformation change occurs and the central stalk rotates
3. ADP and P (which were already binded to the F1 ATPase head) gets converted to ATP due to the energy provided when H+ leaves the Transmembrane H+ carrier
4. ATP is released from the F1 ATPase head.
Discuss other functions of ATP synthase and additional benefits of the proton gradient.
ATP synthase :
- Can also act as a proton pump if matrix H+ is high (if there is a lot of H+ inside the mitochondria matrix, it can rotate in the other direction and use ATP to pump H+ away
Proton gradient :
assists in transport of
- Pyruvate Into the matrix
- ADP into matrix
and P
Define catabolism, describe what happens in each stage of catabolism, and where in the cell each stage takes place
enzymes degrade complex organic molecules into simpler ones
Step 1: Digestion
(stomach, intestines, lysosomes)
- enzymes convert polymers into monomers
Step 2: Glycolysis and pyruvate oxidation to Acetyl CoA
(cytosol (glycolysis), inner mitochondrial membrane (pyruvate oxidation))
glycolysis –> degrades gluose into pyruvate + generates ATP & NADH
pyruvate oxidation –> converts pyruvate into CO2 and acetyl CoA via the pyruvate dehydrogenate complex (also generated NADH)
Step 3: Citric acid cycle
(mitochondrial matrix)
acetyl group in acetyl CoA is transferred to oxaloacetate molecule to form citrate
- transferred acetyl group oxidized to CO2 and produces large amounts of NADH
Step 4: Electron transport chain / oxidative phosphorylation
(inner mitochondrial membrane)
high energy electrons from NADH pass along the electron-transport chain (drives oxidative phosphorylation to produce ATp and consume O2. )
Describe the energy use and energy yield of glycolysis, and the series of enzymatic reactions involved in this process
Uses 2 ATP and 1 glucose to produce 2 pyruvate, 2 ATP and 2 NADH
Class 1(1 -3): Energy investment
- 2 ATP donate an inorganic phosphate to glucose
- glucose phosphroylate by ATP to form sugar phosphate
- isomerization moves carbonyl oxgen from carbon 1 to carbon 2
- hydroxyl group on carbon 1 is phosphorylated by ATP via phosphofructokinase
Class 2 (4 - 5) : Sugar cleavage
- glucose turns into fructose and is then cleaved into 2 three-carbon sugars
4. 6-carbon sugar is cleaved into 2 3 carbon molecules
5. other product of step 4 is isomerized so that both both 3-carbon molecules are the same isomers
Class 3 (6 - 10): Energy generation
- the inorganic phosphate bind of from the 3-carbon sugars to form NADH and 2 ATP as well as 2 pyruvate molecules
6. 2 molecules of glyceraldehyde 3-phosphate (products of step 4 and 5) are oxidized to produce NADH
7. ADP is transferred to high-energy phosphate group to form ATP
8. remaining phosphate ester linkage moved from carbon 3 to carbon 2
9. removable of water from product of step 8 creates high-energy phosphate linkage
10. ADP transferred to high-energy phosphate group to form ATP
List the different types of activated carrier molecules generated by catabolic processes in the cell, discuss how their regeneration enables glycolysis to continue
Glycolysis produces NADH and ATP
NADH is used in fermentation in muscle cells
- enables glycolysis to continue with insufficient oxygen
- Pyruvate in cytosol is converted into lactate
- This reaction causes NADH to give up its electrons to from NAD+, an activated carrier required in glycolysis to continue
( 1 glucose –> 2 pyruvate –> 2 lactate –> 2 NAD+)
Describe the energy use and energy yield of the citric acid cycle, and the series of enzymatic reactions involved
Citric acid cycle: series of 8 reactions that catalyzes the oxidation of carbon atoms of acetyl groups in acetyl CoA
Step 1:
- enzyme removes proton from acetyl group and forms bond to oxaloacetate (loss of CoA via hydrolysis drives reaction forward)
Step 2:
- isometrization reaction moves hydroxyl group from one carbon atom to neighbour
Step 3:
- carbon carrying hydroxyl group converted to carbonyl group to form CO2 and NADH
Step 4:
- the product of step 3: alpha ketoglutarate dehydrogenase complex resembles pyruvate dehydrogenase complex (both perform oxidation to produce NADH, CO2)
Step 5:
- inorganic phosphate displaces CoA to form high energy phosphate
- phosphate is passsed to GDP to form GTP
Step 6:
- FAD accepts two hydrogen to form FADH2
Step 7:
- addition of water places carbonyl to carbon
Step 8:
- carbon carrying hydroxyl group converted to carbonyl group to form NADH and oxaloacetate needed for step 1
List the different types of activated carrier molecules generated by the citric acid cycle
for 1 molecule of acetyl CoA:
3 NADH, 1 FADH2, 1 GTP are released along with 2 CO2
activated carriers can donate electrons to generate up to 30 molecules of ATP per glucose (glucose can only produce 2 ATP per glucose)
Name two checkpoints that adjust glycolysis and citric acid cycle in response to activated carriers / ATP
Phosphofructokinase (regulates glycolysis)
- enzyme in step 3 of glycolysis (controls the entry of sugar into glycolysis) How?
- activated by presence of ADP and inactivate by presense of ATP (when ATP is abundant: enzyme is shut off and glycolysis is shuts downs)
Isocitrate dehydrogenase (citric acid cycle)
List two important energy storage molecules and where they are stored in the body
Glycogen (stores glucose) and is found in liver
Lipid Droplets (stores fatty acids) and is found in adipose tissue
