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!