Cellular Respiration

Cellular Respiration

1. Glycolysis

2. Oxidation of Pyruvate

3. Krebs Cycle

Glycolysis is only the start

 Glycolysis

 Pyruvate has more energy to yield

 3 more C to strip off (to oxidize)

 if O

2 is available, pyruvate enters mitochondria

 enzymes of Krebs cycle complete oxidation of sugar to CO₂

2x

6C 3C

glucose      pyruvate

3C 1C

Step 2: Oxidation of pyruvate



 3 step oxidation process

 releases 1 CO

2 (count the carbons!)

 reduces NAD  NADH (stores energy)

 produces acetyl CoA



 where does CO

2 go?

NAD NADH

3C 2C 1C

pyruvate acetyl CoA + CO₂

[

Pyruvate oxidized to Acetyl CoA

Yield = 2C sugar + CO₂ + NADH

reduction

Step 3: Kreb’s Cycle

This happens twice for each glucose

molecule

4C 6C 4C 4C 4C 2C 6C 5C 4C CO₂ CO₂ citrate acetyl CoA

Count the carbons and electron carriers!

x

2

So we fully oxidized

glucose

C₆H₁₂O₆



CO₂

& ended up with 4 ATP!



produces large quantities of

electron carriers

 NADH

 FADH

2

 stored energy!

 go to ETC

Energy accounting of Krebs cycle



= 6 NADH + 2 FADH₂

3 NAD + 1 FAD 3 NADH + 1 FADH₂

1 ADP 1 ATP

2x

acetyl - CoA          CO

]

[

2x

ATP accounting so far…











Mitochondria



 outer membrane

 inner membrane

 highly folded cristae*

 _{intermembrane space}

 matrix

STAGE 4: Oxidative Phosphorylation



glucose to produce ATP

PART A. Electron Transport Chain

a)

(mostly) transport proteins built into the inner membrane is used to link electron transport to ATP synthesis.



Electron transport chain

NADH NAD+

FADH₂ FAD

H₂O ADP ATP ATP synthase H+ _H+ _H+

H+

H+ H + H+ H+ H+ H+ H+ H+ H+ H+  _P O₂

Electron Transport Chain Chemiosmosis

b) The electrons arrive using electron carriers NADH and

FADH₂

 NADH is oxidized at NADH dehydrogenase, releasing 2

electrons

 FADH

But what “pulls” the

Electrons flow downhill



carrier to carrier downhill to O₂

 each carrier more electronegative

 controlled oxidation AND controlled release of

H₂O NAD NADH ATP H H Controlled release of energy for synthesis of ATP Ele ctro_n tran spo rt c hain

2 2e O₂



2e 



electrons are releasing energy which is used to move H+ from the matrix to the intermembrane space



At the end



oxygen

 oxygen is reduced as it picks up 2 e and 2

protons (from matrix) to make _____





PART B: OXIDATIVE PHOSPHORYLATION









synthesize ATP as H+ move through the ATP synthase channel protein



concentration gradient through the ATP synthase

 ATP synthase turns and releases energy to

 ATP synthase

 enzyme in inner membrane of

mitochondria

 only channel permeable to H+

 flowing H+ cause change in

shape of ATP synthase

enzyme and powers bonding of P_i to ADP

c) At the end

For every H+ proton through the ATP synthase channel 1 ATP is formed

 NADH yields 3 ATP

 FADH

2 yields 2 ATP



An overview of cellular respiration (Layer 3)

 How efficient is cellular respiration?



In other words, a call can harvest about 40% of the energy stored in glucose.

Taking it beyond…



O









Certain poisons interrupt critical events in cellular respiration

 Various poisons

 _{Block the movement of electrons}

 Block the flow of H+ through ATP synthase

 _{Allow H}+ _{to leak through the membrane}

H+

H+ H+

H+

H+

H+ _H+ _H+ H+

H+

H+

H+ H+

O2

H2O P ATP NADH NAD+

FADH2 FAD

Rotenone Cyanide,

carbon monoxide Oligomycin

DNP

ATP Synthase

₂

ADP

Electron Transport Chain Chemiosmosis

1 2

Summary of cellular respiration

 Where did the glucose come from?

 Where did the O₂ come from?

 Where did the CO₂ come from?

 Where did the H₂O come from?

 Where did the ATP come from?

 What else is produced that is not listed in this equation?

 Why do we breathe?

Energy Yields







Anaerobic: Lactic Acid Fermentation

 occurs in humans and other mammals

 The product of Lactic Acid fermentation, lactic acid, is toxic to

mammals

 This is the "burn" felt when undergoing strenuous activity

 The only goal of fermentation reactions is to convert NADH to NAD+ (to use in glycolysis).

 No energy is gained

 Note differences - anaerobic respiration - 2 ATP's produced (from glycolysis), aerobic respiration - 36 ATP's produced (from glycolysis, Krebs cycle, and Oxidative Phosphorylation)

 Carbohydrates, fats, and proteins can all

fuel cellular respiration

 _{When they are converted to molecules that}

enter glycolysis or the citric acid cycle

OXIDATIVE PHOSPHORYLATION

(Electron Transport and Chemiosmosis)

Food, such as peanuts

Carbohydrates Fats Proteins

Sugars Glycerol Fatty acids Amino acids Amino groups

Beyond glucose: Other carbohydrates



 polysaccharides    glucose

 _{ex. starch, glycogen}

 other 6C sugars    glucose

 _{ex. galactose, fructose}

hydrolysis



Beyond glucose: Proteins

hydrolysis

amino group = waste product

excreted as ammonia, urea,

or uric acid

enter

Krebs cycle as acetyl CoA

Beyond glucose: Fats



 glycerol (3C)   PGAL   glycolysis

 fatty acids 

hydrolysis 2C acetyl groups  acetyl coA  Krebs cycle glycerol enters glycolysis

as PGAL

Carbohydrates vs. Fats

fat

carbohydrate



 more C in gram of fat

 more O in gram of carbohydrate



digestion & synthesis

 by regulating enzyme



 digestion of

carbohydrates, fats & proteins

 all catabolized through same pathways

 enter at different points

 cell extracts energy

from every source

Metabolism

Metabolism

Krebs cycle

intermediaries  

amino acids pyruvate   glucose

acetyl CoA   fatty acids

 Coordination of digestion & synthesis

 by regulating enzyme

 Synthesis

 enough energy?

build stuff!

 cell uses points in

glycolysis & Krebs cycle as links to pathways for

synthesis

 _{run the pathways}

“backwards”

 eat too much fuel, build fat

Cells are versatile &

 Food molecules provide raw materials for biosynthesis

 Cells use some food molecules and intermediates from glycolysis and the citric acid cycle as raw materials

 This process of biosynthesis

 Consumes ATP

ATP needed to drive biosynthesis

ATP CITRIC ACID CYCLE GLUCOSE SYNTHESIS Acetyl

CoA Pyruvate G3P Glucose

Amino groups

Amino acids Fatty _{acids Glycerol} Sugars

Carbohydrates Fats

Proteins

Cells, tissues, organisms



 All organisms

 _{Can harvest energy from organic molecules}

 Plants, but not animals

 _{Can also make these molecules from inorganic}

sources by the process of photosynthesis