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BMSC 220 > Mitochondria, Cholorplasts, and Peroxisomes > Flashcards

Mitochondria, Cholorplasts, and Peroxisomes Flashcards

1
Q

What is mitochondria the site of?

A

Metabolic energy generated in the form of ATP by the breakdown of carbohydrates and lipids through the process of oxidative phosphorylation.

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2
Q

What reinforces the theory of endosymbiotic origin of mitochondria?

A

The presence of mitochondrial DNA.

Rickettsia sp. is an intracellular parasitic proteobacteria whose genome has many similarities to mitochondrial genomes.

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3
Q

What is the function of the outer membrane of mitochondria? What is its composition?

A 
Outer membrane defines the outer perimeter of the mitochondria.
Contains porins (specialized proteins that form transmembrane channels permeable to all molecules below a size of 10kDa) and has a similar composition to the plasma membrane.
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4
Q

What is the function of the inner membrane? What is its composition?

A

Primary site of ATP production by oxidative metabolism and is the only effective permeability barrier between the matrix and cytoplasm.

  • Contains cardiolipins, which are specialized phospholipids with 4 fatty acyl tails that decrease permeability of the inner membrane to protons.
  • 80% protein by weight.
  • contains cristae (folds of the inner membrane) .
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5
Q

What is the function of the innermembrane space? What is its composition?

A

Proteins in the innermembrane space are used for protein import and export as well as other mitochondrial functions.
Has a similar composition to the cytoplasm.

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6
Q

What is the function of the matrix? What is its composition?

A

Contains the majority of enzymes involved in oxidative metabolism and is the site of mitochondrial DNA, RNA, and proteins synthesis.
Has a 50% protein solution and a higher pH and negative charge relative to the cytoplasm.

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7
Q

What are the characteristics of the mitochondrial genome? (3)

A
  1. located in the matrix
  2. circular DNA with one origin of replication.
    • all genes are transcribed at the same time (polycistronic)
  3. maternally inherited
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8
Q

How do mitochondria in cells adjust to meet changing energy demands?

A

Variation in shape and intracellular organization

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9
Q

How are mitochondria organized? How can this organization be altered?

A

Organized into networks which can be altered by changing the number of mitochondria, their size, and their location.

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10
Q

How do mitochondria arise?

A

Through fission (division) and/or fusion of pre-existing mitochondria.

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11
Q

What does fusion allow for?

A

Allows mitochondria to share genetic material and proteins, and to increase in size.

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12
Q

Why is fission important ? (2 reasons)

A
  1. to distribute mitochondria evenly to daughter cells during cell division
  2. increase the number of mitochondria in a cell when more energy is needed.
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13
Q

What does continual fusion and fission allow for?

A

Mitochondria to modify their morphology within the cell.

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14
Q

What does mitochondrial division (fission) require? (5 things)

A
  1. DNA replication
  2. RNA synthesis
  3. membrane generation via phospholipid transfer from the smooth ER
  4. protein synthesis within mitochondria
  5. protein importation from cytoplasm
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15
Q

What is catabolism?

A

The breakdown of large, complex molecules into smaller, simpler molecules with release of chemical energy.

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16
Q

What is the energy released from catabolism used for?

A

Majority of the energy is captured predominantly by ATP to form phosphoanhydride bonds (high energy phosphate bonds)

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17
Q

What is the standard free energy change for ATP hydrolysis?

A

-7.3kcal/mole

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18
Q

What are the concentrations of ATP, ADP, and Pi in a typical cell?

A

ATP: 10mM
ADP: 10mM
Pi: 1mM

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19
Q

How much ATP does the oxidation of a glucose molecule yield?

A

38 ATPs (net)

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20
Q

How much more energy/gram does fat produce vs sugar?

A

2.5X more energy/gram

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21
Q

How much ATP does the oxidation of NADH and FADH2 yield?

A

NADH: 3 ATP
FADH2: 2 ATP

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22
Q

What occurs when NAD+ is reduced to NADH? What happens when NADH is oxidized?

A

When reduced it accepts both a proton (H+) and 2 electrons.

When oxidized it releases a proton and 2 electrons.

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23
Q

What are 2 sources for acetyl CoA?

A
  1. pyruvate: product of glucose breakdown through glycolysis
  2. fatty acids: product of fat (triglyceride) breakdown
24
Q

What are the primary products of the citric acid cycle?

A

NADH (3 molecules) and FADH2 (1 molecule)

25
Q

What occurs during oxidative phosphorylation in the electron transport chain?

A

Electrons that enter the electron transport chain from NADH and FADH2 combine with O2 to produce H2O.

26
Q

What is chemiosmotic coupling?

A

A mechanism used to drive ATP synthesis after energy has been released from oxidation/reduction reactions in the electron transport chain.

27
Q

What are electron carriers?

A

negatively charged molecules that can transfer a proton

28
Q

What is coenzyme Q (ubiquinone)?

A

Lipid soluble electron carrier (electrons are carried to complex III)

29
Q

What is cytochrome c (Cyt c)?

A

a peripheral membrane protein on the outer face of the inner membrane (electrons are carried to complex IV)

30
Q

How is FADH2 generated?

A

succinate is reduced by succinate dehydrogenase to fumarate within complex II

31
Q

What occurs when FADH2 is reduced to FAD+H2?

A

Donates electrons to coenzyme Q but no protons are pumped by complex II

32
Q

How are electrons transported down the electron transport chain?

A

electrons are transported through complex III and IV, driving the proton pump, as described for complex I

33
Q

How many protons per pair of electrons carried do complexes I and III transfer?

A

4 protons from the matrix to isolation membranes per pair of electrons carried.

34
Q

How many protons per pair of electrons carried does complex IV transfer?

A

2 protons per pair of electrons, plus 2 protons combined with O2 to form H2O in the matrix.

35
Q

What is complex V?

A

ATP synthase

36
Q

What are the 2 subunits of ATP synthase? What are their functions?

A
  • F0 spans the inner membrane and forms a channel through which protons move.
  • F1 catalyzes the synthesis of ATP
37
Q

What are the 4 potential target locations of imported proteins?

A
  1. outer membrane
  2. inner membrane
  3. intermembrane space
  4. matrix
38
Q

What mechanism is used to target proteins from the cytoplasm to mitochondria?

A

Presequence: 15-55 positively charged amino acids, taken to amino terminal and removed by proteolytic cleavage following import.
Targets proteins to the matrix.

39
Q

What must proteins contain to be targeted to the inner membrane?

A

An additional internal compartment targeting amino acid sequence

40
Q

What is needed to target proteins to the outer compartments of mitochondria?

A

Internal mitochondrial import signals - can be one or a series of amino acid sequences within the protein.

41
Q

Where do internal compartment targeting amino acids direct cytosolic proteins to?

A
  • the outer membrane
  • the intermembrane space
  • some inner membrane proteins
42
Q

What is the Tom complex?

A

Translocase of the outer membrane

43
Q

What is the Tim complex?

A

Translocase of the inner membrane

44
Q

What is Hsp70?

A

Hsp70 are chaperones that keep proteins unfolded until reaching their final destination. Once at the final destination, helps to fold the protein into its proper sequence.

45
Q

What is the function of MPP (matrix processing peptidase)?

A

Cleaves the targeting sequence following transport.

46
Q

What are Tim9 and Tim10?

A

Intermembrane space chaperones that carry proteins to the Tim22 channel complex.

47
Q

What is Oxa?

A

Translocase within the inner membrane for proteins synthesized within the matrix of mitochondria.

48
Q

Where is Mim1 located? What does it do?

A

Mim1 is located on the outer membrane and inserts proteins with a single alpha helical transmembrane domain.

49
Q

What is the function of SAM (sorting and assembly machinery)

A

Moves some proteins from the intermembrane space to the outer membrane, such as porins.

50
Q

What is cardiolipin? What does it do?

A

A unique 4 fatty acyl tail phospholipid found in the mitochondrial inner membrane.
It is synthesized within mitochondria and decreases permeability of the inner membrane to protons

51
Q

What does the chloroplast genome encode?

A

Encodes genes involved in photosynthesis, rRNA, tRNA, ribosomal proteins, and metabolism.

52
Q

What are the functions of peroxisomes?

A
  • metabolize reactive oxygen species (ROS), also known as free radicals
  • oxidizes fatty acids which produce energy
  • in liver, synthesize bile salts
53
Q

What does the enzyme catalase break down?

A

Breaks down H2O2, which is produced by oxidation reactions, into H2O and O2.

54
Q

How are peroxisomes assembled?

A
  • By proteins synthesized on free ribosomes

- By proteins transported into vesicles from the ER

55
Q

What are the two types of peroxisome target sequences?

A

PTS1 and PTS2

56
Q

What are Pex proteins (peroxins)?

A

Involved in peroxisome assembly

57
Q

What are the two mechanisms in which new peroxisomes are formed?

A
  1. de novo synthesis from the ER (completely new contents)

2. through growth and division of existing peroxisomes

BMSC 220 (13 decks)

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