Cell Bio: Chapter 5

Front 1

The early Earth was populated by anaerobes. How did they capture and utilize energy?

Back 1

by oxygen-independent metabolism

Front 2

When did oxygen accumulate in the primitive atmosphere?

Back 2

after cyanobacteria appeared

Front 3

How have aerobes evolved from anaerobes?

Back 3

to use oxygen to extract more energy from organic molecules

Front 4

Where does aerobic respiration take place in eukaryotes?

Back 4

in the mitochondrion

Front 5

How are mitochondria shaped?

Back 5

typical mitochondria are bean-shaped organelles but they can also be round or threadlike

Front 6

Which characteristics of mitochondria reflect the energy requirements of the cell?

Back 6

size and number of mitochondria

Front 7

The balance between fusion and fission is likely a major determinant of which three characteristics?

Back 7

mitochondrial number, length, and degree of interconnection

Front 8

Describe mitochondria when fusion becomes more frequent than fission.

Back 8

mitochondria tend to become more elongated and interconnected

Front 9

Describe mitochondria when fission becomes more frequent than fusion.

Back 9

there are more numerous and distinct mitochondria

Front 10

What does the number and size of mitochondria in a cell depend upon?

Back 10

the role of the cell
the body's condition(s)

Front 11

It has been known for many years that mitochondria and endoplasmic reticulum (ER) engage in extensive interactions. What was discovered to be induced via this contact?

Back 11

mitochondrial fission--> induced by contact with thin tubules from the ER

Front 12

Mitochondria can be split or joined, but they can also...

Back 12

replicate independently of the host cell. This is important for muscle development.

Front 13

How many membranes does the outer boundary of a mitochondrion contain?

Back 13

two - outer and inner

Front 14

Describe the outer membrane of mitochondria.

Back 14

serves as the mitochondrion's outer boundary

Front 15

Describe the inner membrane of mitochondria.

Back 15

subdivided into two interconnected domains:
inner boundary membrane - forms a double membrane outer envelope

cristae - where the machinery for ATP is located

Front 16

Mitochondria have an inner membrane that is folded. What is the significance of this?

Back 16

This increases membrane surface area and allows many reactions that generate ATP to take place on the cristae.

Front 17

The membranes of the mitochondrion divide the organelle into two aqueous compartments. Describe them.

Back 17

matrix - (within the interior of the mitochondrion) has a gel-like consistency due to the high concentration of water-soluble proteins

intermembrane space - proteins located in this space are known for their role in initiating cell suicide

Front 18

What does the mitochondrial matrix consist of and what can be synthesized in it?

Back 18

contains a circular DNA molecule, ribosomes, and enzymes

RNA and proteins can be synthesized in the matrix.

Front 19

The outer and inner membranes of mitochondria have very different properties. What is the outer membrane composed of?

Back 19

~50% lipid by weight and contains a mixture of enzymes involved in diverse activities

Front 20

The outer and inner membranes of mitochondria have very different properties. What is the inner membrane composed of?

Back 20

contains more than 100 different polypeptides and has a very high (3:1) protein/lipid ratio; made of more than 75% protein

Front 21

The inner membrane of mitochondria contains no _______________, but is rich in an unusual phospholipid, _________________. What is the significance of this?

Back 21

no cholesterol

rich in cardiolipin

These are characteristics of bacterial plasma membranes, from which the inner mitochondrial membrane has presumably evolved.

Front 22

The outer membrane of mitochondria contains ________________.

Back 22

a large pore-forming protein called porin

Front 23

Is the inner membrane permeable or impermeable? Outer membrane?

Back 23

inner membrane - impermeable, even to small molecules

outer membrane - permeable to even some proteins

Front 24

The reactions of glycolysis generate ___________ and ____________ in the cytosol.

Back 24

pyruvate and NADH

Front 25

List the steps of glycolysis.

Back 25

1) Glucose is phosphorylated. Lose 1 ATP. Enzyme: hexokinase.

2) Rearrange Glucose 6-phosphate --> Fructose 6-phosphate

3) Fructose 6-phosphate is phosphorylated. Lose 1 ATP. Enzyme: phosphofructokinase. RATE LIMITING STEP

4) Cleave into two isomers.

5) Rearrange dihydroxyacetone phosphate to glyceraldehyde-3 phosphate (isomerization step).

6) Dump a hydrogen, gain a low-energy phosphate.

7) Remove the phosphate on carbon 1. Gain 1 ATP per substrate. Enzyme: phosphoglycerate kinase.

8) Rearrange: move the phosphate from carbon 3 to carbon 2.

9) Dehydrate: lose water.

10) Remove the final phosphate from carbon 2. Gain 1 ATP per substrate. Enzyme: pyruvate kinase.

Front 26

What is the significance of steps 1 and 3 of glycolysis?

Back 26

phosphate groups are transferred from ATP to the six-carbon sugar to produce fructose 1,6-bisphosphate

Front 27

What is the significance of step 6 of glycolysis?

Back 27

oxidation and phosphorylation of glyceraldehyde 3-phosphate to produce 1,3-bisphosphoglycerate and NADH

Front 28

What is the significance of steps 7 and 10 of glycolysis?

Back 28

transfer of phosphate groups from three-carbon phosphorylated substrates to ADP to produce ATP by substrate phosphorylation

Front 29

What is the cyclic pathway that acetyl CoA takes where the substrate is oxidized and its energy is conserved?

Back 29

tricarboxylic acid cycle (TCA cycle) also known as the Kreb's Cycle

Front 30

What is generated from the first step of the Kreb's cycle?

Back 30

1 NADH and 1 CO2

Front 31

What is generated from the second step of the Kreb's cycle?

Back 31

citrate

Front 32

What is the rate limiting step of the Kreb's cycle?

Back 32

step 4

1 NADH and 1 CO2 per glucose. This forms alpha-ketoglutarate.

Front 33

What is generated in step 5 of the Kreb's cycle?

Back 33

1 NADH and 1 CO2

Front 34

What is generated in step 9 of the Kreb's cycle?

Back 34

1 NADH

Front 35

Summarize the Kreb's cycle.

Back 35

4 reactions in the cycle transfer a pair of electrons to NAD+ to form NADH, or to FAD+ to form FADH2.

form 1 GTP by substrate-level phosphorylation

release 3 CO2

Front 36

Reaction intermediates in the TCA cycle are common compounds generated in other catabolic reactions. What is the significance of this?

Back 36

This makes the TCA cycle the central metabolic pathway of the cell.

Front 37

Fatty acids and proteins typically form ____________.

Back 37

acetyl CoA

Front 38

Where does oxaloacetate come from?

Back 38

typically comes from carbs, but can also come from Asn, Asp

Carbs are easier--they're just converted to glucose or fructose first and fit into glycolysis. The Kreb's cycle will not run without oxaloacetate, which is why carbs are important.

Front 39

What are the primary products of the TCA cycle?

Back 39

the reduced coenzymes FADH2 and NADH

Front 40

How does NADH formed from glycolysis enter the mitochondria?

Back 40

via malate-aspartate (proteins as energy) --> reduce NADH to NAD+

OR

glycerol-phosphate shuttles (fats as energy) --> produces FADH2

Front 41

What is the role of the glycerol phosphate shuttle?

Back 41

electrons are transferred from NADH to DHAP to form glycerol 3-phosphate, then to FAD to form FADH

Front 42

What is pumped out of the across the inner membrane as electrons move through the electron-transport chain?

Back 42

H+

Front 43

Summarize the two step process of oxidative phosphorylation.

Back 43

formation and harnessing of the proton gradient

Front 44

What is the term that describes the coupling of H+ translocation to ATP synthesis?

Back 44

chemiosmosis

Front 45

How many molecules of ATP are formed from each pair of electrons donated by NADH?

Back 45

three molecules of ATP

Front 46

How many molecules of ATP are formed from each pair of electrons donated by FADH2?

Back 46

two molecules of ATP

Front 47

What provides the energy required to phosphorylate ADP to ATP?

Back 47

the controlled movements of protons back across the membrane through the ATP-synthesizing enzyme

Front 48

What two ways can ATP be formed in the mitochondria?

Back 48

substrate-level phosphorylation

OR

oxidative phosphorylation --> accounts for more than 160 kg of ATP in our bodies per day

Front 49

Strong oxidizing agents have a ______________ affinity for electrons, while strong reducing agents have a _____________ affinity for electrons.

Back 49

strong oxidizing agents - high affinity

strong reducing agents - weak affinity

Front 50

Redox reactions are accompanied by a _____________ in free energy.

Back 50

decrease

Front 51

What is the term that describes the measure of charge separation caused by the transfer of electrons?

Back 51

redox potential

Front 52

If electrons flow from the sample half-cell to the reference half-cell, the standard redox potential of the sample couple is _____________.

Back 52

negative (preferential)

Front 53

If electrons flow from the reference half-cell to the sample half-cell, the standard redox potential of the sample couple is ______________.

Back 53

positive

Front 54

How do electrons move through the inner membrane of the mitochondrion?

Back 54

via a series of carriers of decreasing redox potential

Front 55

Which specific electron carriers transfer electrons associated with either NADH or FADH2?

Back 55

carriers that make up the electron transport chain

Front 56

Which electron carriers are polypeptides bound to either FAD or FMN?

Back 56

flavoproteins

Front 57

Which electron carriers contain heme groups bearing Fe or Cu metal ions?

Back 57

cytochromes

Front 58

Which electron carriers are located within a single protein complex and alternate between Cu2+/Cu3+?

Back 58

three copper atoms

Front 59

Which electron carriers consist of a lipid-soluble made of five-carbon isoprenoid units?

Back 59

ubiquinone

Front 60

Which electron carriers contain Fe in association with inorganic sulfur?

Back 60

iron-sulfur proteins

Front 61

The energy level of the (negatively charged) electrons _______________ with each step of increasingly positive redox potential.

Back 61

decreases

Front 62

Describe complex I of the electron-transport complexes.

Back 62

(NADH dehydrogenase) catalyzes transfer of electrons from NADH to ubiquinone and transports four H+ per pair

Front 63

Describe complex III of the electron-transport complexes.

Back 63

(cytochrome bc1) catalyzes the transfer of electrons from ubiquinone to cytochrome c and transports four H+ per pair

Front 64

Describe complex II of the electron-transport complexes.

Back 64

(succinate dehydrogenase) catalyzes transfer of electrons from succinate to FAD to ubiquinone without transport of H+

Front 65

Describe complex IV of the electron-transport complexes.

Back 65

(cytochrome c oxidase) catalyzes transfer of electrons to O2 and transports H+ across the inner membrane

Front 66

What is a large complex that adds four electrons to O2 to form two molecules of H2O?

Back 66

cytochrome oxidase

Front 67

Which metabolic poisons bind catalytic sites in complex IV?

Back 67

CO, N3-, and CN-

Front 68

What is the gateway to the electron-transport chain?

Back 68

complex I

Front 69

Describe what complex I consists of.

Back 69

Complex I contains a peripheral hydrophilic domain and a membrane-embedded hydrophobic domain.

Front 70

What is electron transfer in the peripheral hydrophilic arm of complex I coupled with?

Back 70

conformational changes to proton translocation across the membrane domain

Front 71

What promotes proton translocation in complex I?

Back 71

unprotonated glutamic acid and protonated lysine residues driven by transmembrane helix conformational changes

Front 72

What is the term that describes the proton pump in synthetic liposomes that adds four electrons to O2 to form two molecules of H2O (complex IV)?

Back 72

cytochrome oxidase

Front 73

What rate are electrons transferred in complex IV?

Back 73

one at a time

Front 74

What is thought to drive conformational changes in complex IV? What do these changes promote?

Back 74

energy released by O2 reduction

These changes promote H+ ions movement through protein

Front 75

What does the tendency for electrons to be transferred from one carrier to the next depend upon?

Back 75

the energy potential difference between the two redox centers

Front 76

What does the rate of transfer of electrons depend upon?

Back 76

the catalytic activities of the proteins involved

Electrons may travel 10-20A (considerable distances) between adjacent redox centers.

Front 77

What is the term that describes the route in which electrons probably flow that consists of a series of covalent and hydrogen bonds that stretch across parts of several amino acid residues?

Back 77

tunneling pathways

Front 78

Explain the two components of the proton gradient.

Back 78

pH gradient (ΔpH) - created by the concentration gradient between matrix and intermembrane space

electric potential (Ψ) - results from the separation of charge across the membrane

Front 79

What is the term that describes energy present in both components of the proton gradient?

Back 79

proton-motive force (Δp)

Front 80

What uncouples glucose oxidation and ATP formation? How?

Back 80

Ditrophenol (DNP) uncouples glucose oxidation and ATP formation by increasing the permeability of the inner membrane to H+, thus eliminating the proton gradient

Front 81

What accounts for differences in metabolic rate?

Back 81

differences in uncoupling proteins (UCP)

Front 82

What did the isolation of coupling factor 1, or F1, show? What is the significance of this?

Back 82

it hydrolyzed ATP

Under experimental conditions, it acts as an ATP synthase. This led to the conclusion that an ionic gradient establishes a proton-motive force to phosphorylate ADP.

Front 83

What are the two major portions of ATP synthase? Explain.

Back 83

F1 - catalytic subunit, contains 3 catalytic sites for ATP synthesis

F0 - attaches to the F1 and is embedded in the inner membrane; base contains a channel through which protons are conducted from the intermembrane space to the matrix

Front 84

How many structural units are in the c ring of ATP synthase?

Back 84

10-14 subunits (varies depending on the source of the enzyme)

Front 85

Both the yeast mitochondrial and E. coli ATP synthase have _____ c subunits.

Back 85

10

Front 86

The chloroplast ATP synthase has _____ c subunits.

Back 86

14

Front 87

Describe the F0 mechanism.

Back 87

The c subunits of the F0 base form a ring.

Protons moving through the membrane rotate the ring.

The rotation provides a twisting force that drives ATP synthesis.

Front 88

Binding sites on the catalytic subunit F1 can be _______, ___________, or __________.

Back 88

open, loose, or tight

Front 89

What is the special peroxisome that plants contain? What does it do?

Back 89

glyoxysome - converts fatty acids to glucose by germinating seedlings

(why seeds and nuts are oil-rich)

Front 90

What is the term that describes membrane-bound vesicles that contain oxidative enzymes which carry out the two-step reduction of molecular oxygen to water?

Back 90

peroxisomes

Front 91

What is the function of peroxisomes?

Back 91

oxidize very-long-chain fatty acids and synthesize plasmalogens (a class of phospholipids)

Front 92

What drives the transport of ADP into and ATP out of the mitochondrion?

Back 92

H+ gradient

Front 93

What is the most important factor controlling the respiration rate in a mitochondrion?

Back 93

ADP

Front 94

What alters the binding affinity of the active site during the ATPase mechanism?

Back 94

movement of protons through ATP synthase