AP Biology 2005-2006 The Point is to Make ATP! ATP Making energy!

AP Biology 2005-2006

The Point is to Make ATP!

ATP

Making energy!

AP Biology

Chapter 9 Warm-Up Define:

Glycolysis Respiration Chemiosmosis Phosphorylation Fermentation Electrochemical

gradient FAD FADH2

NAD+ NADH

Explain “glycolysis”. Where does it occur? How does it “work”?

AP Biology

Chapter 9 Warm-up What is the chemical equation for

cellular respiration? Remember OILRIG

In the conversion of glucose and oxygen to CO2 and H2O, which molecule is reduced?

Which is oxidized? What happens to the energy that is

released in this redox reaction?

NAD+ is called a(n) ________________.

Its reduced form is _________.

AP Biology

Chapter 9 Warm-Up Why is glycolysis considered an

ancient metabolic process? Where in the cell does glycolysis

occur? What are the reactants and products of

glycolysis? Which has more energy available:

ADP or ATP? NAD+ or NADH? FAD+ or FADH2?

AP Biology

Chapter 9 Warm-Up Where does the Citric Acid Cycle occur in

the cell? What are the main products of the CAC? How is the proton gradient generated? What is the purpose? Describe how ATP synthase works. In cellular respiration, how many ATP are

generated through Substrate-level phosphorylation? Oxidative phosphorylation?

AP Biology

Chapter 9 Warm-Up In fermentation, how is NAD+ recycled?

AP Biology

What you need to know:

The summary equation of cellular respiration. The difference between fermentation and cellular

respiration. The role of glycolysis in oxidizing glucose to two

molecules of pyruvate. The process that brings pyruvate from the

cytosol into the mitochondria and introduces it into the citric acid cycle.

How the process of chemiosmosis utilizes the electrons from NADH and FADH2 to produce ATP.

AP Biology

Chapter 9.Cellular Respiration and

Fermentation

AP Biology

The Point is to Make ATP!

ATP

What’s the point?

AP Biology 2005-2006

Harvesting stored energy Energy is stored in organic molecules

heterotrophs eat food (organic molecules) digest organic molecules

serve as raw materials for building & fuels for energy

controlled release of energy series of step-by-step enzyme-controlled reactions

“burning” fuels carbohydrates, lipids, proteins, nucleic acids

AP Biology 2005-2006

Harvesting energy stored in glucose Glucose is the model

catabolism of glucose to produce ATP

glucose + oxygen carbon + water + energydioxide

C6H12O6 6O26CO2 6H2O ATP+ + + + heat

CO2 + H2O + heatfuel

(carbohydrates)

combustion = making heat energy by burning fuels in one step

respiration = making ATP (& less heat)by burning fuels in many small steps

ATP

CO2 + H2O + ATP (+ heat)

res

pir

ati

on

AP Biology 2005-2006

How do we harvest energy from fuels? Digest large molecules into smaller ones

break bonds & move electrons from one molecule to another as electrons move they carry energy with them that energy is stored in another bond, released

as heat, or harvested to make ATP

+

e-

+e-

+ –loses e- gains e- oxidized reduced

oxidation reduction

AP Biology 2005-2006

How do we move electrons in biology? Moving electrons

in living systems, electrons do not move alone electrons move as part of H atom

+

H

+H

+ –loses e- gains e- oxidized reduced

oxidation reduction

C6H12O6 6O2 6CO2 6H2O ATP+ + +

oxidation

reductionH

AP Biology 2005-2006

Coupling oxidation & reduction Redox reactions in respiration

release energy as breakdown molecules break C-C bonds strip off electrons from C-H bonds by removing H atoms

C6H12O6 CO2 = fuel has been oxidized

electrons attracted to more electronegative atoms

in biology, the most electronegative atom? O2 H2O = oxygen has been reduced

release energy to synthesize ATP

C6H12O6 6O2 6CO2 6H2O ATP+ + +

oxidation

reduction

O2

AP Biology

Oxidation & reduction Oxidation

removing H loss of electrons releases energy exergonic

Reduction adding H gain of electrons stores energy endergonic

C6H12O6 6O2 6CO2 6H2O ATP+ + +

oxidation

reduction

AP Biology 2005-2006

Overview of cellular respiration 4 metabolic stages

Anaerobic respiration 1. Glycolysis

respiration without O2

in cytosol

Aerobic respiration respiration using O2

in mitochondria

2. Pyruvate oxidation 3. Kreb’s cycle 4. Electron transport chain

C6H12O6 6O2 6CO2 6H2O ATP+ + + (+ heat)

AP Biology

The Point is to Make ATP!

ATP

What’s the point?

AP Biology

Glycolysis “sugar splitting” Believed to be ancient (early

prokaryotes- no O2 available)

Occurs in cytosol Partially oxidizes glucose (6C) to 2

pyruvates (3C) Net gain: 2 ATP and 2 NADH

Also makes 2H2O

No O2 required

AP Biology

Glycolysis Breaking down glucose

“glyco – lysis” (splitting sugar)

most ancient form of energy capture starting point for all cellular respiration

inefficient generate only 2 ATP for every 1 glucose

in cytosol why does that make evolutionary sense?

glucose pyruvate2x6C 3C

AP Biology 2005-2006

Evolutionary perspective Life on Earth first evolved without

free oxygen (O2) in atmosphere energy had to be captured from

organic molecules in absence of O2

Organisms that evolved glycolysis are ancestors of all modern life all organisms still utilize

glycolysis

You mean, I’m related to them?!

AP Biology

Glycolysis Stage 1: Energy Investment Stage

Cell uses ATP to phosphorylate compounds of glucose

Stage 2: Energy Payoff Stage Two 3-C compounds oxidized For each glucose molecule:

2 Net ATP produced by substrate-level phosphorylation

2 molecules of NAD+ NADH

AP Biology 2005-2006

glucoseC-C-C-C-C-C

fructose-6PP-C-C-C-C-C-C-P

DHAPP-C-C-C

PGALC-C-C-P

pyruvateC-C-C

2 ATP2 ADP

2 NAD+

2 NADH4 ADP4 ATP

Overview10 reactions

convert 6C glucose to two 3C pyruvate

produce 2 ATP & 2 NADH

activationenergy

Substrate level phosphorylation

AP Biology

Glycolysis summary

endergonicinvest some ATP

exergonicharvest a little more ATP& a little NADH

AP Biology 2005-2006

Substrate-level Phosphorylation In the last step of glycolysis, where

did the P come from to make ATP?

P is transferred from PEP to ADP kinase enzyme ADP ATP

I get it!The P came

directly from the

substrate!

AP Biology

Energy accounting of glycolysis

Net gain = 2 ATP some energy investment (2 ATP) small energy return (4 ATP)

1 6C sugar 2 3C sugars

2 ATP 2 ADP

4 ADP 4 ATP

glucose pyruvate2x6C 3C

All that work! And that’s all I

get?

AP Biology

Is that all there is? Not a lot of energy…

for 1 billon years+ this is how life on Earth survived only harvest 3.5% of energy stored in glucose slow growth, slow reproduction

Heck of a way to make a living!

AP Biology 2005-2006

We can’t stop there….

Going to run out of NAD+

How is NADH recycled to NAD+? without regenerating NAD+,

energy production would stop another molecule must

accept H from NADH

glucose + 2ADP + 2Pi + 2 NAD+ 2 pyruvate + 2ATP + 2NADH

Glycolysis

NADH

AP Biology

How is NADH recycled to NAD+? Another molecule must accept H from NADH

anaerobic respiration ethanol fermentation lactic acid fermentation

aerobic respiration

NADH

AP Biology 2005-2006

Anaerobic ethanol fermentation Bacteria, yeast

1C3C 2Cpyruvate ethanol + CO2

Animals, some fungi

pyruvate lactic acid3C 3C

beer, wine, bread at ~12% ethanol, kills yeast

cheese, yogurt, anaerobic exercise (no O2)

NADH NAD+

NADH NAD+

AP Biology

Pyruvate is a branching pointPyruvate

O2O2

Kreb’s cyclemitochondria

fermentation

AP Biology

Glycolysis (summary)

AP Biology

The Point is to Make ATP!

ATP

What’s the point?

AP Biology

Mitochondrion Structure

AP Biology

Cellular Respiration

AP Biology

Glycolysis is only the start

3C 1C

AP Biology

Oxidation of pyruvate Pyruvate enters mitochondria

3 step oxidation process releases 1 CO2 (count the carbons!) reduces NAD NADH (stores energy) produces acetyl CoA

Acetyl CoA enters Krebs cycle where does CO2 go?

Waiting to exhale?

NAD NADH

3C 2C 1C

pyruvate acetyl CoA + CO2[2x ]

AP Biology

Pyruvate oxidized to Acetyl CoA

Yield = 2C sugar + CO2 + NADH

reduction

oxidation

AP Biology

Krebs cycle

AP Biology

4C

6C

4C

4C

4C

2C

6C

5C

4C

CO2

CO2

citrate

acetyl CoACount the carbons and electron carriers!

x2

3Cpyruvate

reduction of electroncarriers and

oxidation of sugars NADH

NADH

FADH2

NADH

ATP

This happens twice for each glucose molecule

AP Biology 2005-2006

So we fully oxidized glucose

C6H12O6

CO2

& ended up with 4 ATP!

Whassup?

What’s thePoint?

AP Biology 2005-2006

Krebs cycle produces large quantities of electron carriers NADH FADH2

stored energy! go to ETC

NADH & FADH2

What’s soimportant

about NADH?

AP Biology

Citric Acid Cycle (Krebs) Occurs in mitochondrial matrix Acetyl CoA→ Citrate→

Net gain: 2 ATP, 6 NADH, 2 FADH2 (electron carrier)

ATP produced by substrate-level phosphorylation

CO2

CO2

AP Biology

So why the Krebs cycle? If the yield is only 2 ATP, then why?

value of NADH & FADH2

electron carriers reduced molecules store energy! to be used in the Electron Transport Chain

AP Biology

The Point is to Make ATP!

ATP

What’s the point?

AP Biology

Cellular respiration

AP Biology

ATP accounting so far… Glycolysis 2 ATP Kreb’s cycle 2 ATP

Life takes a lot of energy to run, need to extract more energy than 4 ATP!

There’s got to be a better way!

What’s thePoint?

AP Biology

There is a better way! Electron Transport Chain

series of molecules built into inner mitochondrial membrane mostly transport proteins

transport of electrons down ETC linked to ATP synthesis

yields ~34 ATP from 1 glucose! only in presence of O2 (aerobic)

Thatsounds more

like it!

AP Biology

Mitochondria Double membrane

outer membrane inner membrane

highly folded cristae* fluid-filled space

between membranes = intermembrane space

matrix central fluid-filled space

* form fits function!

AP Biology

Electron Transport Chain

AP Biology 2005-2006

PGAL

GlycolysisKreb’s cycle

2 NADH

8 NADH2 FADH2

Remember the NADH?

AP Biology

Electron Transport Chain NADH passes electrons to ETC

H cleaved off NADH & FADH2

electrons stripped from H atoms H+ (H ions) electrons passed from one electron carrier to next in

mitochondrial membrane (ETC) transport proteins in membrane pump H+ across inner

membrane to intermembrane space

AP Biology

But what “pulls” the electrons down the ETC?

electrons flowdownhill to

O2

AP Biology 2005-2006

Electrons flow downhill Electrons move in steps from

carrier to carrier downhill to O2

each carrier more electronegative controlled oxidation controlled release of energy

AP Biology 2005-2006

Why the build up H+? ATP synthase

enzyme in inner membrane of mitochondria

ADP + Pi ATP

only channel permeable to H+ H+ flow down concentration

gradient = provides energy for ATP synthesis

molecular power generator! flow like water over water wheel flowing H+ cause change in

shape of ATP synthase enzyme powers bonding of Pi to ADP

“proton-motive” force

AP Biology 2005-2006

Chemiosmosis couples ETC to ATP synthesis build up of H+ gradient just so H+ could flow through

ATP synthase enzyme to build ATP

ATP synthesis

So that’sthe point!

Oxidative phosphorylation

AP Biology

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?

C6H12O6 6O2 6CO2 6H2O ~36 ATP+ + +

AP Biology

Taking it beyond… What is the final electron acceptor in

electron transport chain?

O2

So what happens if O2 unavailable?

ETC backs up ATP production ceases cells run out of energy and you die!

AP Biology

The Point is to Make ATP!

ATP

What’s the point?

AP Biology

Any Questions??

AP Biology

Glycolysis

Fermentation Keep glycolysis going

by regenerating NAD+

Occurs in cytosol No oxygen needed Creates ethanol [+

CO2] or lactate

2 ATP (from glycolysis)

Respiration Release E from

breakdown of food with O2

Occurs in mitochondria

O2 required (final electron acceptor)

Produces CO2, H2O and up to 32 ATP

O2 presentWithout O2Without O2

AP Biology

Various sources of fuel

Carbohydrates, fats and proteins can ALL be used as fuel for cellular respiration

Monomers enter glycolysis or citric acid cycle at different points

AP Biology

pyruvate oxidation

ENERGY

glycolysis(cytosol)

glycolysis(cytosol)

ethanol + CO2

(yeast, some bacteria)

ethanol + CO2

(yeast, some bacteria)

anaerobic (without O2)

aerobic cellular respiration

(with O2)

lactic acid(animals)

lactic acid(animals)

ETCETC

chemiosmosischemiosmosis

oxidative phosphorylation

oxidative phosphorylation

citric acid cycle

citric acid cycle

mitochondria Fermentation(cytosol)

Fermentation(cytosol)