Lecture 8

Question 1

The mitochondria is the site of _____ respiration

Answer 1

• Aerobic

Citric Acid Cycle,Fatty acid oxidation (b-oxidation), Electron transport chain

Question 2

General mitochondria size is…

Answer 2

Mitochondria: 0.5 to 5 mm diameter

Question 3

Mitochondria will contain their own (2)

Answer 3

-Contain own DNA
mtDNA: circular, no histones (bacterial-like)
-Contain own ribosomes
Bacteria: 70S ribosome
Mitochondria: 70S ribosome (bacterial-like)
Eukaryote: 80S ribosome

Question 4

Mitochondria has a _____ membrane and replicates through ______ fission

Answer 4

• double/binary

Question 5

Endosymbiont Theory (4)

Answer 5

1. Early atmosphere had no O2
   - Cells relied upon anaerobic metabolism
2. Photosynthetic microbial organisms began to evolve (chemical energy from light energy)
   
   • CO2 + H2O ↔ Sugar and O2
3. Increased O2 in the atmosphere/environment
4. Aerobic bacteria evolved
   
   • Krebs cycle enzymes in cytosol
   • Electron transport chain molecules on plasma membrane

Question 6

Endosymbiont Theory cont….

Slides 6-9

Answer 6

At about the same time:

• Protoeukaryotes (early ancestors of eukaryotes) evolved the ability to ingest materials via phagocytosis
• Protoeukaryotes phagocytized the aerobic bacteria (which survived the phagocytic process within a vesicular structure)
  
  • Developed a mutualistic relationship
    - Aerobic bacteria: survive within a protected environment
    - Protoeukaryote: new source for ATP (aerobic respiration)

Question 7

The outer mitochondrial membrane contains _______ and will allow for ______ of fairly _______ substances

Answer 7

pores, diffusion, large

Question 8

The mitochondria is made up of 4 structures

Answer 8

1. Outer mitochondrial membrane
2. Inner Mitochondrial membrane (Cristae)
   -ATP Synthase (a mitochondrial enzyme localized in the inner membrane, where it catalyzes the synthesis of ATP from ADP and phosphate, driven by a flux of protons across a gradient generated by electron transfer from the proton chemically positive to the negative side.)
3. Intermembrane space: ↑[H+]
4. Matrix
   mtDNA, ribosomes
   Krebs cycle enzymes
   Other enzymes

Question 9

The outer membrane is ________ permeable, but the inner membrane is rather _________

Answer 9

-highly/ impermeable

Question 10

How do substrates get moved in and out of the matrix?

Answer 10

Specific transport systems use either the electrical or acid/base (ΔpH) gradients (components of the proton gradient) to help move substrates in and out of the matrix.

Question 11

NAD/NADH are also “shuttled” across the inner membrane via specific shuttles:

Answer 11

1. Glycerol phosphate shuttle

2. Malate aspartate shuttle

Question 12

Movement across the _______ membrane occurs freely through large _______ like ______

Answer 12

• outer/ pores like VDAC

Question 13

Functions of the mitochondrial outer membrane (3)

Answer 13

• Phospholipid synthesis, fatty acid desaturation, and fatty acid elongation

Question 14

Functions of the Inner membrane (3)

Answer 14

-Electron transport, oxidative phosphorylation, and metabolite transport

Question 15

Functions of the Matrix (5)

Answer 15

• RNA synthesis (transcription), Protein synthesis (translation), DNA replication, Pyruvate oxidation, TCA Cycle

Question 16

Mitochondria DNA is ______ (circular, round, helix?) and has only ___ genes

Answer 16

-Circular/ 37 (only 13 of the 37 are involved in mitochondrial respiratory function)

Question 17

Mitochondrial Genome Encodes:

Answer 17

2 ribosomal RNA (rRNA) molecules
22 transfer RNA (tRNA) molecules
13 polypeptides (respiratory complexes)

Question 18

The 13 polypeptides participate in…

Answer 18

-building several protein complexes embedded in the inner mitochondrial membrane

Question 19

NRF-1 (Nuclear respiratory factor -1):

Answer 19

• a nuclear encoded transcription factor that activates the expression of nuclear genes required for mitochondrial respiration

Question 20

Some respiratory complexes/proteins have some subunits that are encoded by the _____ genome and others encoded by the _______ genome

Answer 20

-nuclear, mitochondrial

Question 21

Tfam (Transcription factor A of mitochondria):

Answer 21

• Is a nuclear encoded transcription factor that activates the expression of mitochondrial genes required for mitochondrial respiration.

Question 22

Calcineurin:

Answer 22

-Is a nuclear encoded calcium activated phosphatase

Question 23

NFAT (Nuclear factor of activated T-cells) :

Answer 23

• Is a nuclear encoded transcription factor that translocates to the nucleus upon dephosphorylation by calcineurin. Activates the expression of various nuclear encoded mitochondrial proteins and other proteins

Question 24

PGC-1 (Peroxisome proliferator activated receptor gamma coactivator-1):

Answer 24

** Helps to turn on nuclear encoded mitochondrial genes

• Is a nuclear encoded transcriptional coactivator that assists PPARg (peroxisome proliferator activated receptor gamma, a transcription factor) & other transcription factors (including NRF-2) in activating gene transcription of nuclear encoded genes related to mitochondrial function.

Question 25

During conditions when requirement for either more mitochondria or elevated mitochondrial function (size):
-> Physiological signals induce expression of (2)

Answer 25

• PGC-1 and the NRFs (typically involves calcineurin and NFAT) → increased expression of nuclear and mtDNA encoded mitochondrial proteins.

Question 26

How do the proteins get into the mitochondria

Answer 26

• TOM = translocase of outer membrane
• TIM = translocase of inner membrane
• Nuclear encoded mitochondrial proteins generally have an amino-terminal mitochondrial transit sequence (frequently an a-helix structure)