class 8

Glycolysis overview

Location: Cytoplasm (cytosol)

Purpose: breaks down glucose into pyruvate

Starting molecule: glucose

Input: ATP

Produces: ATP, NADH

End molecule: pyruvate

Citric acid cycle overview

Location: Mitochondrial matrix

Purpose: To oxidize acetyl coa into CO2

Start molecules: Acetyl CoA and Oxaloacetate

Input: Acetyl CoA, oxaloacetate, NAD+, FAD, GPP + Pi

Output: NADH, FADH, GTP, CO2

End molecules: oxaloacetate

What happens to free energy in the order of Glucose > Pyruvate > CO2

free energy decreases

Substrate level phosphorylation

Produces ATP by directly transferring phosphate group from high energy substrate molecule to ADP

No oxygen req (anaerobic)

Very fast

low yield of ATP

Thermodynamics of respiration...explain how its a redox process.

ADP + Pi energy = ATP (endergonic)

Breakdown of ATP to ADP is exergonic

(ATP —> energy + Pi + ADP)

If stopped breathing, what would happen to ATP levels and ADP levels

ATP levels inhibit

ADP levels increase

Catabolism vs anabolism

Catabolism: release energy stored (ex. glycolysis)

• breaks down large molecules

• Exergonic rxns, neg. delta G

Anabolism: use small simple molecules to build complex molecules

• Store energy

• Endergonic rxns, positive delta G

What do high/low ratios of ATP/ADP and NADH/NAD+ represent

High ATP/ADP = healthy cell

Low= stress

High NADH/NAD+ = Oxidative state

Low = Reductive stress

Oxidation of FADH2 comes after Complex I....why is that important?

Complex I generates more proton motive force than Complex II

• its e- has lower energy potential

Where does proton pumping take place

Complex 1, Complex 3, Complex 5

pumps from matrix to inner membrane

Oxidative phosphorylation

Last stage of cellular respiration where ATP is produced using energy derived from redox reactions in the electron transport chain (ETC)

Chemiosmosis

The accumulated proton gradient drives the enzyme ATP synthase to phosphorylate ADP, creating ATP

Why chemiosmosis is built of proton gradients....(why not other molecules).

Can never run out of protons to pump

abundant and charged

Importance of redox-active cofactors in electron transport (requirements for metals like Fe - iron).

Cofactors are redox active - can undergo cycles of being reduced and oxidized, grab an electron and pass it on, over and over = Lots of iron here
No iron = no electron transport

Understand why electrons move spontaneously down the chain from NADH to O2

each cofactor has greater affinity for e- than the one before

Concept of coupling electron transport with ATP synthesis....and concept of uncoupling

• uncoupling dissipates gradient to produce heat instead of ATP

• Holes are in membrane, then H+ thinks that it can can go thru holes instead of ATP synthase, so the no ATP is produced.

There are uncoupling proteins (UCPs) that animals express and chemical uncouplers (e.g. Ripped Freak).

Uncoupling proteins: are good

• hibernations

• babies

• require less ATP but do require the heat

Link between uncoupling expression and being skinny

• Uncoupling expression cant make enough ATP so metabolism for everything else before making ATP is very fast

Why chemical uncouplers (2,4-dinitrophenol) are toxic.....how does it alter metabolism.

• Causes protons to leak in thru membrane and disrupt oxidative phosphorylation

How does metabolism shifts in response to low oxygen...(cool for e.g. muscle cells, just not your brain). 

shifts to anaerobic glycolysis

• fermentation

Importance of fermentation to keeping glycolysis going...(NADH)

it regenerates NAD+ from NADH in the absence of oxygen

What is the Warburg effect

• rely only on glycolysis even when O2 high, never goes thru oxphos

• Almost universal in cancer cells

• Changes in expression of key proteins

role of glucose transporter, hexokinase, and pyruvate dehydrogenase kinase.

All three are expressed more

• glucose transporter is expressed more because cancer cells need more glucose to thrive

• hexokinase is catalyst in glycolysis

• PDK: blocks pyruvate from entering mitchon.

Hypotheses about why the Warburg Effect occurs

1. Increase in acidity = weaker immune acidity so cancer thrives

2. produces waste carbon that creates unnecessary mass

3. fermentation is more efficient for energy production

Basics of cancer detection based on metabolism (using radioactive forms of glucose)

• Inject patient with radioactive glucose and scan where there is high rates of glucose

What stage do cancer cells only rely on?

Glycolysis