Cellular Respiration

Mitochondria Rule!

Mr. Kurt Kristensen

Harvard Biovisions

Mitochondria

Summer Session Week 1:

Cellular Respiration Students should….

1) Understand the locations, and functions of the essential phases of cellular respiration.

2) Describe the connections between each phase of cellular respiration.

3) Understand how mitochondria work with the cell to harvest chemical energy.

4) Understand chemiosmosis and its central role in ATP production.

Living is work.

To perform work, cells require energy from outside sources

In most ecosystems, energy enters as sunlight.

Light energy trapped in organic molecules is available to both photosynthetic organisms and others that eat them.

Cell Respiration Review

Back to the big picture,

Cell Respiration (CH2O CO2 + H2O and ATP)

We will be looking at three connected metabolic processes.

The function of these processes is to make ATP.

Bioenergetics: The Big Picture

• The Equations:

• In general…

– Organic Molecules

– Food

• Combustion or Oxidation of Glucose (∆G) = -686 kcal/mole

• Number of ATP/Glucose Molecule

• Regeneration of ATP (from ADP & Pi) (∆G) = +7.3 kcal/mol

• So…. 38 ATP x 7.3 kcal/mol = 277 kcal

• 277 kcal/mol + (-686 kcal/mol) -409 kcal/mol lost as heat

• That’s about 40% efficient!

CH2O + O2 CO2 + H2O + Energy

C6H12O6 + 6O2 6CO2 + 6H2O + ATP + Heat

Consumers (start with organic molecules,

give off CO2)

• Some Details:

Glycolysis

Fermentation Cellular Respiration

These are re-dox reactions

Cellular Respiration • Oxidation of Food Molecules in the presence of Oxygen

– Releases Chemical energy in food

– Converted to less stable, more useful

• Cumulative Function of 3 metabolic stages

– Glycolysis

– Citric Acid (Kreb’s) Cycle

– Oxidative Phosphorylation (OXYPHOS)

Kreb’s Glycolysis OXYPHOS

FOOD Pyruvate e- shuttles

Living organisms don’t tolerate explosions too well…..

Mitochondria Structure

How many per cell?

Cellular Respiration

Where…How…Connections

Our Objective

• Learn the important details about the 3

metabolic stages of cellular respiration

• Glycolysis, Citric Acid Cycle, Oxidative

Phosphorylation

• Remember that the cell is using glucose

to make ATP (it’s harvesting energy)

Remember these stages are connected!

SLP: Substrate Level

Phosphorylation

• RBC’s have no mitochondria

• Hard-working muscle

• Phospocreatine + ADP creatine phosphokinase ATP + creatine

Phase 1: Glycolysis

• Literally…”sugar

break”, the splitting

of sugar

• (2 phases)

– Energy Investment

– Energy Return

Fig 9.8

Glycolysis 1: Energy Investment • What happens, and

why? – 2 ATP molecules are

spent to… 1) Trap the glucose

molecule in the cytosol

2) Destabilize the glucose molecule so it will break in half and more easily “fit” into the mitochondria…or be used in fermentation

• What’s the“end” product? – The end product of

the energy investment phase is 2 molecules of G3P (glyceraldehyde 3-phosphate)

Glycolysis

Glycolysis 2: Energy Return

• G3P is a 3-carbon sugar that can be further rearranged to make Pyruvate

• 2 NET molecules of ATP are returned during this rearragement, but the real energy is in the…

• The “end” product(s): – NADH

– Pyruvate (> 75% of energy of glucose still remains in 2 pyruvate molecules)

Connections: Pyruvate is Oxidized

In the presence of Oxygen, pyruvate is actively transported into mitochondria

and…

1) Pyruvate is converted to a 2-Carbon compound (CO2) is released

2) This 2-Carbon compound is further oxidized (and NAD+ is reduced)

3) Coenzyme A is added to the 2-carbon compound, it’s called Acetyl CoA,

and this enters the Kreb’s Cycle.

Citric Acid Cycle:

• It is a cycle!

• Where does it

happen?

• What are the

outcomes?

Oxaloacetate

(4-C)

Citrate

(6-C)

Citric Acid Cycle:

The Bottom Line…

Pyruvate is completely

oxidized and the energy is

converted to NADH and

FADH2 (ETC) and ATP via

S.L.P.

6 NADH and 2 FADH2

per glucose molecule

This is the intersection

between Glycolysis and

OXY PHOS

You don’t need to learn every step and every enzyme!

Oxidatative Phosphorylation Overview:

During oxidative phosphorylation, chemiosmosis couples electron transport to ATP Synthesis.

This may sound complicated, but it’s something you need to know.

P.C.

Oxidative Phosphorylation1:

E.T.C. • Where?: Along the inner membrane of

the mitochondria – 1000’s

• What? – Proteins with prosthetic groups (co

factors, that alternatively oxidize their “uphill” neighbors, and then get oxidized by their “down hill” neighbors

• How?

– Each Protein in the ETC is more electronegative (better at pulling electrons) from it’s uphill neighbor. Oxygen drives the whole thing, because oxygen is the most electronegative element in the chain.

• What else happens?

– Oxygen is reduced to water

– Hydronium ions (“protons”, H+) are pumped across the inner membrane into the intermembrane space of the mitochondria.

Oxidative Phosphorylation 2

• So What? – E.T.C. sets up a proton gradient

across the innner membrane of mitochondria

– Higher [H+] in the intermembrane space compared to the matrix

• ATP Synthase – This is a protein complex

that allows H+ to diffuse back across the membrane and “makes” ATP as the H+ flow through

• (much like a turbine generates electricity as water flows through it)

Oxidative Phosphorylation 3: Putting it all together

[ ]

[ ]

1)

2)

3)

1) e- flow down the electron transport chain

2) as e- flow, H+ are pumped against their concentration

gradient

3) ATP synthase couples the flow of H+ with ATP synthesis

Oxidatative Phosphorylation Overview:

During oxidative phosphorylation, chemiosmosis couples electron transport to ATP Synthesis.

Chemiosmosis! An energy-coupling

mechanism that uses energy stored in the form of a H+ gradient across a membrane to drive cellular work.

Cellular Respiration: Review (F9.16) (don’t look at the book, let’s work this out together.)

Reactants, Products, major intermediates, processes, specific locations

Net ATP Production

Mode of ATP Production

Get to know this figure…it’s great review.

ATP Accounting? • Catabolism of Glucose, ∆G = -686 kCal/mol

• Anabolism of ATP from ADP + Pi, ∆G = 7.3 kCal/mol

• About 36-38 mol ATP/mol glucose

• ATP synthesis is roughly… 40% efficient. Compare that cars ≈ 25% efficient

• Where does the rest of the energy go? It generates body heat (e.g. 37°C)

If you didn’t eat pure sugar today…Have I got a deal for you.

What about Fermentation?

Fermentation: an alternate pathway for

energy production (ATP synthesis)

• Fermentation is further

oxidation of pyruvate in an

anoxic environment

• fermentation starts with...

– Glycolysis

• F.A…Facultive Anaerobes

– (mammals, some bacteria)

• O.A…Obligate Anaetobes

– (e.g. Botulism)

Fermentation: (2 processes)

• What do these pathways have in common?

– start with glycolysis

– generate ATP through reduction of NAD+ to NADH

• What’s different? – alcohol fermentation = 2 steps

– Lactate fermentation = 1 step

• What’s the significance of alcohol fermentation?

– Downfall of Western Civilization

• What’s the significance of lactic acid fermentation?

– fatigue

• What else do these pathways have in common?

– Both keep glycolysis going!

– Both have by products the cell has to export, and that slow down glycolysis.

Comparing Fermentation and Cellular

Respiration

• Commonalities: Both are energy-yielding pathways that convert chemical energy in organic molecules to ATP

• Differences: Cellular respiration requires Oxygen. Cellular respiration is 16-18x more efficient than fermentation! – That’s 18x more ATP from

the same amount of food. That’s huge!

Oxidative Phosphorylation

Glycolysis is ancient…

• How old is it? – Est. to be 3 billion years

old

• What else do we know

– Is found in prokaryotes and eukaryotes

– Does not require membranes

– Does not require organelles

– therefore…evolved before eukaryotes, but has been conserved b/c it is still useful

Video Review

• http://www.suman

asinc.com/webco

ntent/animations/

content/cellularre

spiration.html

• http://www.brooks

cole.com/chemistr

y_d/templates/stu

dent_resources/s

hared_resources/

animations/oxidati

ve/oxidativephosp

horylation.html

1. In what part of the cell does glycolysis take place?

2. List the reactants and products of glycolysis. 3. Describe the event that occurs when pyruvate enters the mitochondria? 4. In what major area of the mitochondria does the Krebs Cycle take place? 5. List the reactants and products of the Krebs Cycle. 6. Identify the major structure or area where the Electron Transport System (ETS) take place. 7. What is/are transferred from the Krebs Cycle to the Electron Transport System? 8. What reactant molecule is essential for electron transport to occur? 9. What molecule is the final electron acceptor of the ETS? 10. Describe two main functions of the ETS.

Cellular Respiration: Critical Thinking

1. If a person moved from San Diego, CA (sea-level) to Estes Park, CO (elevation 7500 ft.), what would be the effect on cellular respiration for this person? 2. In terms of cellular respiration, why is it necessary to incorporate plants into a terrarium along with fauna (animals)? 3. What effect might smoking cigarettes have on cellular respiration? 4.Describe any disease symptoms that might be related to the interference or interruption of the processes of cellular respiration. 5. According to your model of cellular respiration, what could be happening when a runner must revert to walking?

Cell Respiration Application Problems: