Module 1: Carbohydrates III Part 1

Question 1

Physical Characteristics: Outer Membrane (semipermeable)

Answer 1

– 50% lipid, 50% protein
– Porin (transmembrane channel protein)
– Permeability < 5,000 – 10,000 MW
– 6% of total mitochondrial protein

Question 2

Physical Characteristics: Intermembrane space

Answer 2

– 6% of total mitochondrial protein

Question 3

Physical Characteristics: Inner membrane (impermeable)

Answer 3

• 24% lipid, 76% protein (highest proportion of protein than other cellular membranes)
• Cardiolipin
• Cristae
• 21% of total mitochondrial protein
• ANT, ATP synthase, respiratory chain enzymes, transport proteins

Question 4

Physical Characteristics: Matrix

Answer 4

– Hundreds of enzymes, mtDNA, ribosomes, tRNAs

– 67% of total mitochondrial protein

Question 5

What is located in the Matrix?

Answer 5

• TCA cycle enzymes
• Fatty-acid oxidation
• mtDNA replication
• mtDNA transcription/translation
• Fe-S biogenesis
• Protein folding and degradation
• Urea cycle enzymes (liver & small intestines)
• Gluconeogenic enzymes (liver & kidney)

Question 6

What is located in the Inner Membrane?

Answer 6

• Oxidative phosphorylation
• Metabolic transport
• Protein import (TIM)
• Protein assembly
• Protein degradation

Question 7

What is located in the Intermembrane Space?

Answer 7

• Electron transfer (cytochrome c)
• Cristae remodeling (Opa 1)
• Redox enzymes
• Protein imports (s TIMs)
• Apoptosis factors (e.g., cytochrome c, Smac/Diablo)

Question 8

What is located in the Outer Membrane?

Answer 8

• Protein imports (TOM & SAM)
• Metabolite influx/efflux
• Fission, fusion, & distribution
• Apoptosis factors (e.g., Bcl-2, Bax)
• Signaling molecules

Question 9

What do mitochondria do?

Answer 9

-Generate 90% of energy needs via mitochondrial oxidative phosphorylation (they make ATP)
-Aerobic metabolism
Ca2+ signaling (buffering) **
Re-generate NADH for glycolysis **
Urea Cycle
Biosynthesis of amino acids, heme, steroid hormones
“Gatekeepers” for apoptotic signaling (cytochrome c) **
-Make heat (esp. brown adipose tissue)
-Generate free radicals for cell-signaling **

Question 10

How are mitochondria related to circulation and respiration?

Answer 10

• Aerobic metabolism
• Systematically extract energy from nutrient (substrate) molecules
• Constantly remove of excess electrons through the reduction of water
• The respiratory and circulatory system’s primary purpose is to deliver oxygen and substrates to the mitochondria (and to eliminate carbon dioxide)

Question 11

Pi Transport

Answer 11

• Phosphate carrier, an electroneutral Pi-
• H+ symport driven by delta pH
• Maintaining high concentration of Pi for
• ATP synthesis

Question 12

Ca2+ Transport

Answer 12

• Influx driven by membrane potential, (negative inside)

- Efflux driven by Na+ gradient, in exchange for Na+, an antiport

Question 13

NADH Transport

Answer 13

• Transport of NADH formed by glycolysis
• NADH goes cytoplasm -> mitochondria matrix via electron shuttle systems that accept electrons from cytoplasmic NADH
• Reducing equivalents enter mitochondria, and give up the electrons to electron acceptors in the mitochondrial matrix

Question 14

Glycerol phosphate shuttle

Answer 14

• Functions in mammalian skeletal muscle and brain, very energy-demanding tissues (insect flight muscles)
• NADH produced by glycolysis enters the electron transport chain via FADH2, which is less energy efficient.
• For every NADH you get 3 ATP
• For every FADH2 you get 2 ATP

Question 15

ETC Complex I

Answer 15

• NADH-CoQ oxidoreductase, AKA NADH dehydrogenase
• Entry site for NADH
• Transfers e- from NADH to Coenzyme Q
• Proton pump
• e- transfer leads to a net flux of 4 protons to the intermembrane space/P side
• ATP is produced

Question 16

ETC Complex II

Answer 16

• Succinate-CoQ reductase
• Entry site for FADH2
• Transfers e-‘s from succinate to Coenzyme Q (accept electrons from Complex I and II)
• The transfer produces very little free energy, cannot contribute to the formation of the proton gradient (not a proton pump)
• No ATP is produced

Question 17

ETC Complex III

Answer 17

-CoQH2:Cytc oxidoreductase
-Electron transfer from reduced Q, a 2e- carrier, to cytochrome c, single e- carrier
-Two steps, Q Cycle—radical state of Q is formed, semiubiquinone
-2e- transferred to Cyt c and 4 net H+ are pumped into the intermembrane space (two half Q cycles of 2 H+ each)
Pumps protons outside the matrix to the intermembrane space
-ATP produced

Question 18

ETC Complex IV

Answer 18

• Cytochrome c oxidase
• Electron transfer from Cytochrome c to molecular oxygen
• Two protons (per e- pair) are pumped across the membrane
• ATP is produced

Question 19

What are the 4 Complexes of the ETC?

Answer 19

• Complex I: NADH-CoQ oxidoreductase, AKA NADH dehydrogenase
• Complex II: Succinate-CoQ reductase
• Complex III: CoQH2:Cytc oxidoreductase
• Complex IV: Cytochrome c oxidase

Question 20

Summarize the Electron Transport Chain

Answer 20

• The e-‘s from NADH and FADH2 formed during glycolysis, beta-oxidation and the TCA cycle, are transferred to molecular O2, to generate H2O
• Electron transfer occurs through electron transport chain, complexes of electron carriers, in the inner mitochondrial membrane
• For every molecule of NADH that is oxidized, 10 protons are pumped into the intermembrane space of the mitochondria (4 protons from Complex I, 4 protons from Complex III and 2 from Complex IV)
• These protons form a concentration gradient across the membrane (higher concentration in the intermembrane space than in the mitochondrial matrix)