Bio 106 - TCA cycle and Chemiosmosis

mitochondria

• exist in all eukaryotes

• inner and outer membranes

• energy center is in the matrix

• functions: produces ATP, regulates immunity, balances calcium, cell death and renewal, stem cell regulation

four main categories of cellular respiration

glycolysis, pyruvate oxidation, citric acid (TCA) cycle, electron transport/chemi osmosis (ATP synthase)

Where in the mitochondria do most of the energetic reactions take place? Why might our current idea of the mechanisms of oxidative phosphorylation be incomplete?

• inner mitochondrial membrane (ECT and ATP synthase complexes)

• core concepts (ECT, proton gradient, ATP synthesis) are well established but involvement of other proteins/signaling pathways lead to complexities (ideas may be incomplete)

Before the mitochondria can begin the TCA cycle what molecule must pyruvate be oxidized and stored to? What type of molecule is this and what are its other functions?

• Acetyl-CoA (mitochondria’s favorite molecule)

• high-energy, carries a two-carbon acetyl group to TCA cycle

• in TCA: combines w/ oxaloacetate to form citrate (transforms into ATP)

• other functions: fatty acid synthesis, ketone body formation, regulation of gene expression

TCA cycle is unanimous to…

citric acid cycle, krebs cycle

the TCA cycle begins with ________, H2O is removed to transform citrate to isocitrate, what type of reaction is this

the TCA cycle begins with Acetly-CoA attaching to citrate… dehydration-rehydration rxn

What are the products of the TCA cycle. Where is most of the energy produced stored?

• 3 molecules of NADH and one molecule of FADH2

• stored within electron carriers (NADH and FADH2) which then transfer their energy to the ETC and ultimately generate ATP

NADH and FADH transfer electrons in the form of _________

hydrogen

Flavin adenine dinucleotide (FAD)

• RedOX-active coenzyme

• reduced to FADH2

Succinyl-CoA syntheses

replaces CoA w/ inorganic phosphate (Pi) converting succinyl CoA → succinyl phosphate → (transferred to) ADP → (forms) ATP (or GDP→GTP depending on what enzyme was used)

succinate dehydrogenase

oxidizes succinate by transferring 2 H to the coenzyme FAD to produce FADH2, resulting in fumarate formation

every type of _________ passes through the TCA cycle at some point

every type of macromolecule passes through the TCA cycle at some point (if glycolysis is a hwy, TCA is a roundabout)

oxidative phosphorylation

• powered by ETC

• reduce O2 to H2O using energy passed on by electrons

• yields a lot of ATP

• ADP→ATP powered by energy from the hydrogen conc. gradient

what is the second electron carrier protein in the ETC?

succinate dehydrogenase

each carrier protein in the ETC _______ while being _______ to _______

each carrier protein in the ETC moves/changes while being oxidized/reduced to pump hydrogen to the inter membrane space from the matrix

the ECT “vaccume”

proton gradient between inter membrane space (high conc.) and mitochondrial matrix (low conc.) that drives ATP synthase

ECT from a redox perspective

• each carrier is a better electron acceptor than the last

• oxygen is the final carrier (most electromagnetic)

6 inhibitors of oxidative phosphorylation

• complex 1: rotenone (insecticide)

• complex 2: carboxin (fungicide)

• complex 3: antimycin A (insecticide)

• complex 4: cyanide, carbon monoxide

• ATP synthase: oligomycin

• ATP-ADP translocase: atracyloside (ditaff thistle)

ATP in the TCA (per glucose)

• 4 FADH = 8 ATP

• 24 NADH = 24 ATP

• 2 ATP/GTP

• total: 34 ATP

What is the primary standard condition we are manipulating to power the electron transport chain (ETC)? What are our primary electron donors and acceptors?

proton gradient across mitochondrial membrane, primary electron donor is NADH and primary electron acceptor is O2