CATABOLIC PATHWAYS + ETC and OXIDATIVE PHOSPHORYLATION

Question 1

Nicotinamide adenine dinucleotide (NAD)

Answer 1

Loves to oxidise -CH2-CHOH- to -CH2-C=O
* Becomes NADH
* Donates H/e- to complex I

Question 2

Flavin adenine dinucleotide (FAD)

Answer 2

Loves to oxidise –CH2-CH2- to -CH=CH-
* Becomes FADH2
* Stuck inside complex II
* Acceptor + donator of H’s
* Likes to rip H from a saturated hydrocarbon chain

Question 3

Beta oxidation

Answer 3

FA from adipose tissue fat
* triglyceride or triglycerol esterify FA to FA-CoA (trapped)
* swap CoA w/ Carnitine → matrix
* swap back again via CAT-1 & CAT-2

Question 4

Energy in the trapping of FA

Answer 4

ATP converted to AMP
* FA + CoA →(Fatty acyl CoA synthetase)→ FA-CoA
* ATP → AMP + PPi
* PPi hydrolsed by pulling reaction over

Question 5

Coenzyme A (CoA)

Answer 5

• Carrier of acyl groups
• Great for trapping metabolites in cell
• HS - reactive group (where we add things)

Question 6

First H/e- stripping step in beta oxidation

Answer 6

1. FAD introduce double bond
2. FAD → FADH2
3. Oxidation → hydration → oxidation → cleavage
4. water comes in and joins itself on double bond (-OH)

Question 7

Second H/e- stripping step in beta oxidation

Answer 7

1. Now NAD+ does stripping
2. NAD+ → NADH + (H+)
3. forms -C=O group
4. New CoA comes to break a chunk of AcCoA

Question 8

Each time H/e- stripping steps occur…

Answer 8

The chain gets two carbons shorter
* Repeated

Question 9

glycolysis starts with…

Answer 9

Glucose uptake
* Hexokinase adds phosphate → G6P (trapped)

Question 10

GLUT-1

Answer 10

present in all cells all the time

Question 11

GLUT-4

Answer 11

In muscle and adipose tissue (the insulin sensitive tissues)
* Travelling to cell surface to bring extra glucose to fuel exercise

Question 12

GLUT-2

Answer 12

Liver and pancreas (blood glucose regulating tissues)
* Sense it outside the cell
* Flow in and out as much as they like “wide open door”
* Liver needs a way of pumping glucose from glycogen stores into blood

Question 13

Early Glycolysis: ‘Investment phase’

Answer 13

G6P → Fructose6P
* Phosphofructokinase and ATP to produce fructose 1,6-bisphosphate
* split to give 2 3-carbon sugar phosphates

Question 14

Late glycolysis: ‘Return phase’

Answer 14

Bring in phosphate
* oxidise with NAD → super energy molecule
* Recoup some ATP and react with super energy mol
* Recoup some ATP → 2x pyruvate

Question 15

A kinase is an enzyme that…

Answer 15

uses ATP to add a phosphate group to the substrate

Question 16

The Krebs cycle

Answer 16

Fully oxidising Acetyl-CoA to CO2
* Produce lots of NADH, FADH2, even an ATP (…not directly)
* Performing the reactions on a carrier molecule - regenerate the carrier

Question 17

The krebs cycle generates

Answer 17

3 NADH, 1 reduced FAD (FADH2) plus a GTP

Question 18

Oxaloacetate is ____ in the cycle

Answer 18

NOT ‘net’ consumed
* Acts as a carrier

Question 19

Availability of cofactors

Answer 19

NAD, FAD, ADP
* Drive catabolic pathways
* Generally, the more of these, the faster they go

Question 20

Coupling

Answer 20

Rate of O2 consumption matches rate of ATP usage

Question 21

Uncoupling

Answer 21

Short circuit for H+
* NO longer through ATP sythase
* proton gradient dissipate
* NO ATP made

Question 22

If there is no proton gradient…

Answer 22

NO driving force for ATP synthesis
* No back-pressure to stop H+ pumping
* No restriction on H/e - movement down transport chain > O2
* Instant regeneration of NAD from NADH
* Massive fuel oxidation rate
* Massive O2 consumption

Question 23

Dinitrophenol (DNP)

Answer 23

Hydrophobic when protonated
* Can move freely across membrane
* Weak acid
* When H + comes off -ve charge can be delocalized

Question 24

DNP mechanism

Answer 24

Pick up H+, uncharged, travel into matrix, lose it back to sol.
* Again
* Ring structure: -ve charge can dissipate, share around resonance structure
* Can still travel

Question 25

UCP-1 (Uncoupling protein-1)

Answer 25

Thermogenin
* Generates heat
* Found only in brown adipose tissue
* Full of mito

Question 26

Thermogenin

Answer 26

Heat
* smaller/hibernating animals
* Under hormonal control
* Noradrenaline binds 𝛃3-receptors on cell surface
* Stims FA release
* Opens proton channels

Question 27

ETC

Answer 27

4 complexes embedded in inner mito membrane
* structural (shape
* prosthetic group (transport H/e-)
* proteins arranged so that H+ expelling reactions (outside)
H+ consuming reactions (matrix)

Question 28

NAD+

Answer 28

accepts H ion and 2 e- > equivalent to hydride ion H-
* become NADH + (H+)

Question 29

UQ (ubiquinone)

Answer 29

e- move around Complex I from one prosthetic group to another until they reach Q pool
* hydrophobic
* picks up Hs from complex II

Question 30

UQH2

Answer 30

Reduced UQ
* transfers Hs to complex III

Question 31

Cytochrome C & Iron

Answer 31

Cyt C picks up e- from Complex III and gives the e- to complex IV
* Cyt C has a prosthesis group which contains an iron atom
* Changes from ferrous <-> ferric as it loses/accepts the electrons
* Iron does NOT carry hydrogens!

Question 32

Proton pump force has two components

Answer 32

1. energy in gradient based on both charge and conc
2. electrochemical gradient/proton/motive force

Question 33

Glycerol 3-Phosphate Shuttle

Answer 33

NADH effectively by-passing complex I
* get into ETC

Question 34

Malate aspartate shuttle

Answer 34

NADH transferred without loss of proton pumping potential

Question 35

The 4 Routes to Q

Answer 35

1. Complex I
2. Complex II (succinate dehydrogenase in Krebs)
3. First step of β-oxidation
4. Glycerol 3-P shuttle

Question 36

The danger of free radicals

Answer 36

e- in UQ pool can react with molecular O2
* Produce free radicals
* Mutations in DNA
* They are disposed
* Less likely to form if complex III is vacant

Question 37

ATP synthase

Answer 37

Using H+ gradient to make ATP
* movement 3 H+ > 1 ATP
* 10 H+ pumped out for each NADH

Question 38

F0F1 ATPase structure

Answer 38

12 cylindrical proteins rotate around γ subunit as protons enter
* causes β subunit of F1 to change its conformation in 3 ways

Question 39

3 ways the causes β subunit of F1 can change its conformation

Answer 39

1. Accepting ADP and Pi
2. Reacting them together to give ATP
3. Releasing the ATP

Question 40

Rotenone

Answer 40

Inhibits at Complex I
* whole chain stops, H+ pumping stops
* everything downstream is oxidised

Question 41

Cyanide, Azide, Carbon Monoxide

Answer 41

Inhibits at Complex IV
* whole chain stops, H+ pumping stops
* everything upstream stays reduced

Question 42

Alternative acceptor (e.g. Methylene Blue)

Answer 42

Accepts e- from Complex IV before the cyanide blockage point
* Will allow e- transport to continue
* Provided there was a steady supply of methylene blue!