Metabolism 2

CSF Exam 3

Where does Kreb's Cycle take place

cytoplasm in prokaryotes
mitrochondrial matric in eukaryotic cells

what does TCA cycle stand for

Tricarboxylic Acid Cycle (TCA)
Citric Acid Cycle
Kreb's Cycle

why is it important that TCA happens in mito matrix

products from TCA (NADH and FADH2) will be used in oxidative phosprylation (OXPHOS)

when FADH2 is produced in kreb's cycle what is its usage

used in OXPHOS and to make QH2 (ubiquinol)

what does the citric acid cycle play a major role in

catabolic (breakdown) and anabolic (synthesis) pathways

what is Acetyl CoA used for

make lipids for membranes

what is Alpha-Ketoglutarate used for

to make amino acids like glutamate

what is Succinyl CoA used for

used to make heme

what is succinate used for

fuels the inflammatory response

what is oxaloacetate used for

needed for gluconeogenesis also for making amino acids like aspartate and asparagine

take home message of TCA special cycle

central hub for making and breaking things
accomplishes this bc it's a cycle
one major function is production of NADH and FADH2

each pyruvate molecules goes around the circle twice

first pass: pyruvate to oxaloacetate (product of step 8)
second pass: ocaloacetate to CO2

would the kreb's cycle ever go backwards

on early earth conditions were different and TCA likely went in reverse (still seen in some anaerobic molecules)

before making NADH we need to convert pryuvate to Acetyl CoA

pyruvate enters citric acid cycle through acetyl coA
release first CO2 and reduces another NAD+

acetic acid fermentation general

breakdown of fats into Acetyl CoA is a major energy source and uses a process called beta oxidation

what do the reduced electron carriers of TCA have

they contain a lot of energy

what do we have at the end of TCA

lots of electrons and not much free energy

what are the two major pieces of OXPHOS

electron transport system and ATP synthase

what is the goal of the electron transport system

use the electrons from TCA to create a proton gradient

what is the goal of ATP synthase

use the proton gradient to generate ATP

complexs 1,3,4,5

contain proteins from both mitochondrial and nuclear genomes

what are we trying to do with the orientation of the complexs

we are trying to create a gradient in the intermembrane space.
look at the way the protons H+ are getting pumped

big picture of ETS

shuttling electrons through 4 protein complexs
three of the complexs pump protons into intermembrane space (1,3,4)

proton gradient of the ETS

high concentration in the intermembrane space and low concentration in the matrix

what are the two entry points to the ETS

NADH (made in TCA) enters complex 1
FADH2 (made in TCA) enters complex 2

C1 road to QH2

NADH enters complex 1
remove 2H from NADH --> NAD+
two hydrogens added to Q to make QH2
electrons not directly moving from NADH to Q

what is a protein complex that removed hydrogen from NADH

complex 1 = NADH dehydrogenase

In C1 how many protons are pumped where

4 protons are pumped into intermembrane space contributing to the gradient

The C2 road to QH2

FADH2 enters complex 2
remove two hydrogens from FADH2 --> FAD
two hydrogen added to Q to make QH2
electrons not directly moving from FADH2 to Q

another name for FADH2 entering

succinate dehydrogenase

why is C2 special

it is simultaneously working in TCA and OXPHOS

DOESNT PUMP PROTONS

what does the Q cycle do

it will pump 4 protons which contribute to the gradient

are we oxidizing or reducing CtyC

cytC is reduced C3 and oxidized by C4

summary of complex 1: NADH dehydrogenase

NADH enters and converted to NAD+
creating QH2 to be transported to C3
pumping 4 protons to contribute to gradeitn

overall relationship with the complexs with Q cycle

Q cycle means C3 is making/recycling its own QH2

summary of C3 - cytochrom C reductase

performes Q cycle (2 steps) using two QH2 molecules
adds electrons to Cytochrome C to be transported to Complex 4
regenrated QH2 in the second cycle
pumping 4 protons to contribute to the gradient

summary of complex 2: succinate dehydrogenase

FADH2 enters and is converted to FAD
creating QH2 to be transported to C3
functioning simultaneously in TCA cycle (Step 6)

summary of complex 4: Chtochroma X oxidate

removes electrons from CytC and pumps 2 protons to contribute to the gradient

how does ATP synthase generate ATP

e- transport generate potential difference across membrane
protons flow through F0 and convert potential energy to mechanical rotation
rotation alternates conformations of F1 subunits
alternating conformations drive enzyme through enzymatic cycle to make ATP

ATP yield per NADH

process yields max 3 ATP per 10 protons
e transport moved 10 protons for 1 NADH
max yeild is 3 ATP per NADH
inefficiencies and other uses for protons makes yield ~2.5 ATP/NADH

why are eukaryotes better at making ATP

internal membrane bound compartments that allow for a more efficient and regulated process, higher energy yield