CH 9 Glycolysis, Pyruvate Processing, Citric Acid Cycle

Where does Glycolysis occur?

In the cytosol of prokaryotes and eukaryotes

What is Glycolysis overview and what are its 3 stages

Glycolysis the breakdown/spilt of glucose into 2 pyruvate molecules (in the cytoplasm)

its 3 stages are the

Preparatory

Cleavage

Pay off

Explain Preparatory Phase

(how glucose is prepared)

1. 2 ATPs are invested to add phosphate groups to glucose

every time ATP added and consumed making ADP a phosphate group is added (happens twice)

Glucose 6 phosphate

one of the ATPs is used to power enzyme which catalyzes attachment of a phosphate group onto the glucose turning it into glucose 6 phosphate and relasing one ADP molecule

Fructose 6 phosphate

the glucose 6 phosphate is broken down into fructose 6 phosphate with the help of an enzyme

(more symmetric)

Fructose 1-6 biphosphate

the second ATP powers an enzyme to catalyze addition of a phosphate group to fructose 6 phosphate turning it into Fructose 1-6 biphosphate (now it has 2 phosphates). This releases 1 more ADP

(both halves of molecules are fully symmteric making a cleavage point)

1-6 refers to carbon posistion

Explain Cleavage Phase

The fully symmetrical Fructose 1-6 bisphosphate can be spilt down the middle (cleavage point)

into 2 molecules:

dihydroxyacetone phosphate (DHAP) and

glyceraldehyde-3-phosphate (G3P)

both they interchangeable if transformed by enzyme. enzyme converts DHAP into G3P

now there are 2 (G3P)

What is does G3P stand for?

Glycerol dehyde phosphate

Explain Payoff phase

Note: Every time a phosphate group is removed (substrate phosphorylation) ATP is produced through substrate phosphorylation

The 2 G3Ps are oxidized (electrons removed)

An ATP allows phosphate is added to them with the help of an enzyme

the electrons turn 2 NADs into NADHs + H+2

the added phosphates turns G3P into

Biphosphoglycerate (BPG)

each BPG donates a phosphate groups to ADP making ATP

and 3 Phosphoglycerates (3PG)

the 3PG is arranged into 2PG which makes it release H2O and form PEP (phosphoenolpyruvate)

each PEP donates a phosphate group to ADP

making ATP and pyruvate

(also substrate phosphorylation)

In glycosis how many ATP are produced and how many NADH are produced

4 ATP are made (net 2)

2 NADH are produced becasue there are 2 G3Ps

Feedback Inhibition of Glyclyosis

the end products of glycolyisis work to inhibit some enzymes to prevent overproduction of ATP (avoid waste)

specifcally ATP inhibits 3rd anzyme: Phosphofructokinase

Why is phosphofructokinase important

This is an enzyme which catalyzes 3rd step in prepartion process (1-6 fructobiphosphate)

has 2 binding sites for ATP:

active site: binds here to further ATP (make cleavage)

regulartory site: binds here to inhibit

What happens to the Carbon atoms during Glycolysis?

the 6 carbon atoms of Glucose are spilt into 2

3 carbon pyruvate molecules

Glycolitic Step

The 4th step in Glyclyosis where formerly glucose is broken into 2 peices

every 2x after this

Does Glycolysis produce CO2

does not make CO2 only a little ATP (Net 2)

so the Pyruvates still hold significant energy

What does it mean to say Glycolysis is anerobic

no Oxygen is used during its reactions from glucose to pyruvate

What happens to the electrons during Glycolysis?

glucose lost some electrons (partially oxidized) and electrons were moved to NADH

What is the energy yield in Glycolysis

net energy yield was 2 ATP, since 2 of the 4 were consumed

Pyruvate Processing (brief overview)

note: Pyruvate needs O2 to enter mitochondria because citric acid cycle requires O2 to start.

process happens for each pyruvate

1. Pyruvate must be converted to Acetyl CoA before going in Citric Acid cycle

Pyruvate first loses 1 carbon since its a 3 Carbon molecule and

Acetyl is a 2 carbon molecule

1 carbon is lost as CO2 (first in cell resp)

2. as pyruvate is turned into Acetyl CoA molecule its electrons are lost and moved to NAD turning it to NADH

3. after CoA will be attached making Acetyl CoA

Describe structure of Acetyl CoA

Acetyl group (from pyruvate glycolysis)

+

CoA (coenzyme A):

Pantothenic acid (associated with Vitamin B5)

Phosphorylate ADP

Where does pyruvate processing take place?

in the Matrix of the Mitochondria

What happened to Carbons of Pyruvate?

1 Carbon of each pyruvate is lost as CO2 (to become Acetyl)

The remaining carbons form the acetyl molecule

What happened to the electrons of Pyruvate?

As pyruvate is getting made to Acetyl CoA

the electrons of Pyruvate get removed and transferred to NAD turning it into NADH

What was the net energy yield of pyruvate processing?

none it yields no ATP

Why is the citrus acid cycle called tricarboxlyic cycle?

called citric acid cycle because the

1st molecule in citric acid cycle is citrate

which has 3 carboxyl groups (thus tricarboxylic cycle)

Briefly describe what Krebs cycle does

oxidizes Acetyl CoA (derived from pyruvate) using enzyme catalyzed reactions

to produce 1 ATP, 1 FADH, 3 NADH per cycle

the cycle has 8 steps

What does the Citrus Acid cycle produce (per round)

1. Acetyl CoA enters, it spins once in cycle producing 2 CO2, 3 NADH, 1 ATP,1 FADH2

How much energy is yielded during citrus acid cycle? (per glucose)

2 ATP because

1 glucose = 2 pyruvate = 2 Acetyl CoA

and 1 ATP, 3 NADH, 1 FADH2 per Acetyl CoA in cycle

so total (per glucose)

yields 2 ATP, 6 NADH, 2 FADH2

What are the 8 steps of the Krebs Cycle

each step of the cycle has its own enzyme catalyst (only need to know step 1/end cos cycle)

1. :

   Acetyl of Acetyl CoA joins the cycle

   Acetyl (2 carbons) combines with Oxaloacetate which has 4 carbons and this forms citrate (6 carbons)

   note: Citrate will be oxidized ( electrons removed)

when high energy electrons are lost, they move to NAD making NADH.

NAD into NADH and Carbons lost make CO2

later

Then Coenzyme A is added to Ketoglutarate

to make Succinyl CoA (larger molecule) which is important, because CoA helps attach a phosphate group, and

Pi + ADP creates ATP

FADH2 made

NADH made

back to Oxacelate

note ATP GTP same basically

Which carbons are elminated (as CO2) in 1st round of krebs cycle?

Oxoacetate carbons will be eliminated as CO2

Does the Citrus Acid cycle function udner Anerobic conditons

No it cannot

while it doesnt use oxygen directly it cannot produce FAHD2 without it since that needs O2

while NAHD reoxidizes without O2, FADH2 can only be reoxidized with O2

the cycle is thus Aerobic

When in CoA used in cycle and how often?

CoA is used at the start of the cycle when forming citrate (larger moelcule)

and once more to form Succinyl CoA so it can take phosphate group

this is an example of how anabolic (making complex molecules) steps are needed for catabolic pathways (break into simple)

Where does the citric Acid cycle take place?

cycle takes place in the mitochondrial matrix

What happened to carbons of Acetyl CoA

the 2 carbons of Acetyl CoA get combined with Oxoacetate (C4) to make Citrate (C6)

and when citrate gets broken down the Carbons it got from oxoacetate are released as CO2 in first round

(not most reacently added carbons into CO2)

but C from Acetyl CoA will eventually get relased as CO2 in future rounds

What happened in Citrus Acid cycle in terms of Redox reactions?

he just said Oxidative, Anabolic look up later

guess:

Acetyl CoA was oxidized (lost electrons with Carbon lost as CO2) and some lost electrons turned NAD into 3 NADH

FAD 1 FADH2

What was the net energy yield in the citric acid cycle?

it was 1 ATP, 3 NADH, 1 FADH2 per Acetyl CoA

since theres 2 Acetyl Coa per glucose

products listed are 2x

note: round means part of cycle, cycle is whole so fix prior explanations

Cellular respiraton equation recap from glycosis to krebs cycle whats happened

the glucose molecule has been consumed into ATP energy

2 made during glycolysis

2 made during Krebs cycle

C 6 H 12 O 6 check

6 CO 2 molecules produced

2 made during Pyruvate processing

4 during Krebs cycle

all energy remaining to be prcoessed is in electron carriers up until krebs cycle there are

10 NADH

2 FADH2