anaplerotic reactions and electron transport (4-5)

2 ways PEP can be a source of OAA

1. carboxylate PEP (cardiac/skeletal muscle)

2. carboxylate PEP releasing Pi (anaerobes)

phosphoenolpyruvate (PEP) carboxykinase

• reverse gluconeogenesis reaction

• consume CO2 and produce GTP → OAA

PEP carboxylase

PEP→ OAA

• consumer CO2, but don’t produce NTP, produce Pi

glyoxysome

organelles that plants have

• specialized peroxisomes where acetyl-CoA is formed from fatty acids (where energy is stored)

glyoxylate shunt

converts acetyl-CoA to succinate (or another 4 C intermediate of citric acid cycle)

• allows formation of glucose/other intermediates from stored oils

• skip decarboxylation steps (bc need all the CO2 they can get)

what happens in glyoxylate shunt

acetyl-CoA added→ normal unto isocitrate→ top half (C1-C4) cut off→ succinate

• bottom 2 Cs → glyoxylate → interact with acetyl-CoA #2 → malate

put 2 acetyl-CoAs in

create an extra OAA

• 1 NADH

• Net 4C added

why is glyoxylate shunt used

to regenerate intermediates needed from the TCA cycle to use where they are needed for other reactions

isocitrate lyase

cut isocitrate→ succinate + glyoxylate

malate synthase

glyoxylate +acetyl-CoA → malate CoA-SH

for glyoxylate shunt to happen…

isocitrate dehydrogenase needs to get partially inactivated in the presence of high acetate

• partially because aketogultarate is still needed

when isocitrate dehydrogenase is turned down →

isotrate lyase and isocitrate increases → increase in isocitrate lyase activity

where does succinate go after glyoxylate shunt?

leaves glyoxyzome and goes to mitochondria for normal TCA cycle

what happens when NADH build up?

switch to fermentation → replenish NAD+

what are activators of TCA cycle?

AMP, ADP, NAD+ CA2+

what are inhibitors of TCA cycle?

ATP, excess products for each step, NADH

electrons from where enter the respiratory chain

NADH and FADH2

each NADH and FADH2 → how many ATP?

• NADH→ 2.5 ATP

• FADH2→ 1.5 ATP

how many NADH do we get from EMP glycolysis, PDH complex, and TCA cycle?

EMP- 2

PDH- 2

TCA- 6

= 10 NADH

coupling sites

use change in electron to pump H+ across membrane

• pump protons from in to outside of membrane

P to O ratio

how many phosphoryl groups can we transfer onto ADP to make ATP/ per oxygen we make

terminal electron acceptor

O2 (last electron acceptor)

best terminal electron acceptors for anaerobic respiration

O containing molecules

how many coupling sites for most eukaryotic aerobes?

3

how do NADH get their electrons to the ETC?

transfer their electrons to NADH dehydrogenase

As electrons move through the inner membrane…

each carrier has a decreasing redox potential → move down electron tower → lower energy at each step

flavoproteins

• accept 2 e- and 2 H+ but one in each step

• has to get rid of electrons immediately

quinones

super long hydrocarbon tail (lipid soluble/hydrophobic)

• allows us to carry electrons from enzymes whose active sites are on in the inner membrane of mitochondria→ active sites on outer membrane

ubiquinone (coenzyme Q)

type of quinone

• used for aerobic growth

menaquinone (MQ)

type of quinone

• used in anaerobic growth

plastoquinones (PQ)

type of quinone

• used in light dependent reactions of photosynthesis

cytochromes

contain heme group (has a metal ion)

• Fe3+ or Fe2+ accept/donate 1 electron

• did types of hemes- heme a and b stay covalently bound

• cytc: travels around between dif complexes

ways to determine the sequence of e- carriers (3)

1. electrical potential of electron carriers (start at lowest E’°)

2. reduce carriers in a chain→ so they have a ton of e- → slowly add back O2→ watch which ones become oxidized first

3. add dif drugs to see what would happen if dif electron transfers are blocked

E’°

electrical potential

order of e- carriers (8)

NADH→ Q→ cytochrome b→ cytochrome c_1 → cytochrome c→ cytochrome a→ cytochrome a_3 → O_2

complex I

transfers e- from NADH → ubiquinone (Q)

• NADH dehydrogenase

• transfers 4 H+ per pair of e-

complex II

transfers e- from succinate → Q

• succinate dehydrogenase

• e- from succinate → FAD→ Q

• no transport of H+

why no H+ transport in complex II

not enough of a E’° difference between FADH2 and QH2

complex III

e- from Q→ cytochrom b→ cytochrome c1

• cytochrome bc1

• 4 H+ per pair of e-

• e- leave complex by going to cytochrome c III→ IV

complex IV

e- from cytochrome c→ copper→ cytochrome a→ O2

• cytochrome c oxidase

• 2 H+ across membrane per e- pair

• take 2 H+ from intermembrane space and putting them on O→ H2O

how many waters are mad at a time?

4 electrons used → 2 waters

what do free radicals do?

break DNA→ mutations

break proteins→ protein doesn’t work

lipids→ leak stuff you don’t want to leak

what enzymes neutralize free radicals in aerobes?

1. superoxide dismutase (SOD)

2. catalase/glutathione peroxidase

superoxide dismutase

turns O2- into H2O2

glutathione peroxidase

turns H2O2→ H2O

increase in antioxidants

aging happens later, but life expectancy same

respirasome

supercomplexes containing complexes I, III, IV

• allows things to travel between complexes easily