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AP Biology Ms. Gaynor. Chapter 9 (Part 1): Cellular Respiration. Light energy. ECOSYSTEM. Photosynthesis in chloroplasts. Organic molecules. CO 2 + H 2 O. + O 2. Cellular respiration in mitochondria. ATP. powers most cellular work. Heat energy.

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ap biology ms gaynor

AP BiologyMs. Gaynor

Chapter 9 (Part 1):

Cellular Respiration

energy flows into ecosystems as sunlight and leaves as heat

Light energy

ECOSYSTEM

Photosynthesisin chloroplasts

Organicmolecules

CO2 + H2O

+ O2

Cellular respirationin mitochondria

ATP

powers most cellular work

Heatenergy

Energy Flows into ecosystems as sunlight and leaves as heat

http://wps.aw.com/bc_campbell_biology_7/

reminder
Reminder….
  • Anabolic pathways (“A” for add together)
    • Build molecules from simpler ones (ex: photosynthesis)
    • Consume energy (endergonic)
  • Catabolic pathways (“C” for cut in parts)
    • Break down complex molecules into simpler compounds (ex: cell respiration)
    • Release energy (exergonic)
cellular respiration
Cellular respiration
  • Most efficient catabolic pathway
  • Consumes O2 and organic molecules (ex: glucose)
  • Yields ATP To keep working cells must regenerate ATP
catabolic pathways yield energy by oxidizing organic fuels
Catabolic pathways yield energy by oxidizing organic fuels
  • The breakdown of organic molecules is exergonic
  • One catabolic process, fermentation
    • Is a partial degradation of sugars that occurs without oxygen
  • Another example is cellular respiration
cellular respiration1
Cellular respiration
  • Occurs in mitochondria
    • similar to combustion of gas in an engine after O2 is mixed with hydrocarbon fuel.
      • Food = fuel for respiration.
      • The exhaust =CO2 and H2O.

The overall process is:

organic compounds + O2  CO2 + H2O + energy

(ATP + heat)

    • Carbohydrates, fats, and proteins can all be used as the fuel, but most useful is glucose.
mitochondria
Mitochondria
  • # of mito’s in a cell varies by organism & tissue type
  • has its own independent DNA (and ribosomes)  this DNA shows similarity to bacterial DNA
    • according to the endosymbiotic theory mitochondria (and chloroplasts) are descended from free-living prokaryotes.
mitochondrion structure1
Mitochondrion Structure
  • Outer membrane – similar to plasma membrane; contains integral proteins
  • Inner membrane- NOT permeable to ions (needs help to cross); there is a membrane potential across the inner membrane; contains ATP synthase
      • Cristae – large surface area due to folding
  • Matrix- gel-like in middle or lumen; many contains enzymes for cellular respiration
recall redox reactions
RECALL…Redox Reactions
  • Catabolic pathways yield energy
    • Due to the transfer of electrons
  • Redox reactions
    • Transfer e-’s from one reactant to another by oxidation and reduction
      • In oxidation
        • Substance loses e-s (it’s oxidized)
      • In reduction
        • Substance receives e-s (it’s reduced)
examples of redox reactions

becomes oxidized(loses electron)

Na + Cl Na+ + Cl–

becomes reduced(gains electron)

Examples of redox reactions

Xe- + Y  X + Ye-

**energy must be added to remove e-

X = e- donor = reducing agentand reduces Y.

Y = e- recipient = oxidizing agentand oxidizes X.

oxidation of organic fuel molecules during cellular respiration

becomes oxidized

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

becomes reduced

Oxidation of Organic Fuel Molecules During Cellular Respiration
  • During cellular respiration
    • Glucose is oxidized
    • oxygenis reduced
    • E-’s lose potential energy  energy is released

http://student.ccbcmd.edu/~gkaiser/biotutorials/cellresp/ets_flash.html

slide14

2 e– + 2 H+

2 e– + H+

NAD+

NADH

H

Dehydrogenase

O

O

H

H

Reduction of NAD+

+

+

2[H]

C

NH2

NH2

C

(from food)

Oxidation of NADH

N

N+

Nicotinamide(reduced form)

Nicotinamide(oxidized form)

CH2

O

O

O

O–

P

O

H

H

OH

O

O–

HO

P

NH2

HO

CH2

O

N

N

H

N

H

N

O

H

H

HO

OH

Figure 9.4

Electrons are not transferred directly to oxygen but are passed first to a coenzyme called NAD+ or FAD

NAD+ and FAD= e- acceptor and oxidating agent

slide15

2 H

+

1/2 O2

(from food via NADH)

Controlled release of energy for synthesis ofATP

2 H+ + 2 e–

ATP

ATP

Free energy, G

Electron transport chain

ATP

2 e–

1/2 O2

2 H+

H2O

Electron Flow =

(b) Cellular respiration

food  NADH/FADH2 ETC  oxygen

the stages of cellular respiration
The Stages of Cellular Respiration
  • Respiration is a cumulative process of 3 metabolic stages

1. Glycolysis

2. The citric acid cycle

3. Oxidative phosphorylation

the 3 stages
The 3 Stages
  • Glycolysis
    • Breaks down glucose into 2 molecules of pyruvate
    • Makes NADH
  • Kreb’s Cycle (Citric acid cycle)
    • Completes the breakdown of glucose
    • Makes NADH and FADH2
  • Oxidative phosphorylation
    • Driven by the electron transport chain
    • Generates ATP
slide18

Electrons carried

via NADH and

FADH2

Electrons

carried

via NADH

Oxidativephosphorylation:electron transport andchemiosmosis

Citric acid cycle

Glycolsis

2 Pyruvate

Glucose

Cytoplasm

Mitochondrion Matrix

ATP

ATP

ATP

Substrate-level

phosphorylation

Oxidative

phosphorylation

Substrate-level

phosphorylation

Figure 9.6

  • An overview of cellular respiration

Inner Mitochondrion Membrane (Cristae)

slide19

Enzyme

Enzyme

ADP

P

Substrate

+

ATP

Product

Figure 9.7

  • Both glycolysis and the citric acid cycle
    • Can generate ATP by substrate-level phosphorylation (not using ATP synthase!)
stage 1 glycolysis
Stage #1: Glycolysis
  • Glycolysis produces energy by oxidizing glucose  pyruvate
  • Glycolysis
    • Means “splitting of sugar”
    • Breaks down glucose into pyruvate
    • Occurs in the cytoplasmof the cell

1 glucose breaks down  4 ATP made + 2 pyruvate molecules

(net gain of 2 ATP…NOT 4 ATP)

slide22

Glycolysis

Oxidativephosphorylation

Citricacidcycle

ATP

ATP

ATP

Energy investment phase

1 Glucose

2 ADP + 2

used

P

2 ATP

Energy payoff phase

formed

4 ATP

4 ADP + 4

P

2 NAD+ + 4 e- + 4 H +

2 NADH

+ 2 H+

2 Pyruvate + 2 H2O

Glucose

2 Pyruvate + 2 H2O

4 ATP formed – 2 ATP used

2 ATP

+ 2 H+

2 NADH

2 NAD+ + 4 e– + 4 H +

  • Glycolysis consists of two major phases

1. Energy investment phase (endergonic= uses 2 ATP)

2. Energy payoff phase

(exogonic = makes 4 ATP)

glycolysis
Glycolysis

NET

  • Glucose  2 pyruvate (pyruvic acid) + 2 H2O
  • 4 ATP formed – 2 ATP used  2 ATP GAIN
    • substrate-level phosphorylation used
  • 2 NAD+ + 4e- + 4H+  2 NADH + 2H+

**Glycolysis can proceed WITHOUT O2

the energy investment payoff phases of glycolysis
The energy investment & Payoff phases of Glycolysis
  • Let’s take a closer look….
    • Page 166-167 in textbook
    • 10 steps in glycolysis occuring in 2 phases
slide25

CH2OH

Citric

acid

cycle

H

H

Oxidative

phosphorylation

H

Glycolysis

H

HO

HO

OH

H

OH

Glucose

1

2

3

5

4

ATP

Hexokinase

ADP

CH2OH

P

O

H

H

H

H

OH

HO

H

OH

Glucose-6-phosphate

Phosphoglucoisomerase

CH2O

P

O

CH2OH

H

HO

HO

H

H

HO

Fructose-6-phosphate

ATP

Phosphofructokinase

ADP

CH2

O

O

CH2

P

P

O

HO

H

OH

H

HO

Fructose-

1, 6-bisphosphate

Aldolase

H

O

CH2

P

Isomerase

C

O

O

C

CHOH

CH2OH

O

CH2

P

Dihydroxyacetone

phosphate

Glyceraldehyde-

3-phosphate

Figure 9.9 A

Phase #1: The Investment Phase of Glycolysis(endergonic)

slide26

Phase #2: The Payoff Phase of Glycolysis

(exogonic)

2 NAD+

Triose phosphate

dehydrogenase

P i

2

2

NADH

+ 2 H+

10

7

9

6

8

2

O

C

O

P

CHOH

P

CH2

O

1, 3-Bisphosphoglycerate

2 ADP

Phosphoglycerokinase (PFK)

2 ATP

O–

2

C

CHOH

O

P

CH2

3-Phosphoglycerate

Phosphoglyceromutase

O–

2

C

O

C

P

H

O

CH2OH

2-Phosphoglycerate

Enolase

2 H2O

O–

2

C

O

P

C

O

CH2

Phosphoenolpyruvate

2 ADP

Pyruvate kinase

2 ATP

O–

2

C

O

C

O

CH3

Figure 9.8 B

Pyruvate

  • Phosphofructoskinase (PFK)
  • is an allosteric enzyme
  • ATP acts as an allosteric inhibitor to PFK
  • High [ATP]  stops glycolysis via inhibition (blocks active site)
slide27

Glycolysis

  • http://www.northland.cc.mn.us/biology/Biology1111/animations/glycolysis.html
  • http://www.hippocampus.org/AP%20Biology%20II
    • Watch Glycolysis
stage 2 the kreb s cycle
Stage #2: The Kreb’s Cycle
  • The citric acid cycle
    • Takes place in the matrix of the mitochondrion

**NEEDS O2 TO PROCEED

(unlike glycolysis)

slide29

CYTOSOL

MITOCHONDRION

NAD+

+ H+

NADH

O–

CoA

S

2

C

O

C

O

C

O

CH3

1

3

Acetyle CoA

CH3

Coenzyme A

(a vitamin)

CO2

Pyruvate

Transport protein

Figure 9.10

  • Stage #1 ½ : The Citric Acid Cycle
  • Before the citric acid cycle can begin
    • Pyruvate must first be converted to acetyl CoA, which links the citric acid cycle to glycolysis

Acetyl group= unstable

Uses active transport

Diffuses out of cell

the kreb s cycle
The Kreb’s Cycle
  • Also called the “Tricarboxylic Acid Cycle”or the“Citric Acid cycle”
  • NAD+ and FAD (both are coenzymes) = electron “carriers”; proton acceptors
    • They are reduced and carry e-’s from Citric cycle to ETC
    • Dehydrogenase catalyzes hydrogen transfer reaction
nad and fad
NAD+ and FAD

Oxidized Form Reduced Form

NAD+ NADH (2 e-, 1 H)

FAD FADH2(4 e-, 2 H)

THINK: FADH2 come into play in the 2nd stage of cellular respiration; it is also the 2nd electron carrier 

slide32

Pyruvate (from glycolysis,2 molecules per glucose)

Glycolysis

Citricacidcycle

Oxidativephosphorylation

ATP

ATP

ATP

CO2

CoA

NADH

+ 3 H+

Acetyle CoA

CoA

CoA

Citricacidcycle

2 CO2

3 NAD+

FADH2

FAD

3 NADH

+ 3 H+

ADP + P i

ATP

Figure 9.11

An overview of the citric acid cycle

(this occurs for EACH pyruvate molecule)

the kreb s cycle1
The Kreb’s Cycle
  • Let’s take a closer look….
    • Page 169 in textbook
    • 8 steps in citric cycle in MATRIX
    • 1 turn of cycle  2 reduced carbons enter  2 oxidized carbons leave
slide34

Citric

acid

cycle

Oxidative

phosphorylation

Glycolysis

S

CoA

C

O

CH3

Acetyl CoA

CoA

SH

O

C

COO–

H2O

NADH

1

COO–

CH2

+ H+

COO–

CH2

COO–

NAD+

Oxaloacetate

C

8

COO–

HO

CH2

2

CH2

HC

COO–

COO–

COO–

HO

CH

HO

CH

Malate

Citrate

COO–

CH2

Isocitrate

COO–

CO2

Citric

acid

cycle

3

H2O

7

NAD+

COO–

NADH

COO–

CH

+ H+

Fumarate

CH2

CoA

SH

HC

a-Ketoglutarate

CH2

COO–

C

O

4

6

SH

CoA

COO–

COO–

COO–

CH2

5

CH2

FADH2

CO2

CH2

CH2

NAD+

FAD

C

O

COO–

Succinate

NADH

CoA

P i

S

+ H+

Succinyl

CoA

GDP

GTP

ADP

ATP

Figure 9.12

Figure 9.12

kreb s cycle summary
Kreb’s Cycle Summary
  • pyruvate  Acetyl-CoA + 1 NADH
  • Each turn of cycle uses 1 pyruvate
    • So… 1 glucose molecule produces 2 turns of Kreb’s cycle
  • 1 turn of cycle yields 4 NADH, 1 ATP, and 1 FADH2 and 3 CO2 (as waste product)

Remember to multiply by 2…why?

  • http://www.hippocampus.org/AP%20Biology%20II
    • Watch Pyruvate
stage 3 oxidative phosphorylation electron transport chain etc chemiosmosis
Stage #3: Oxidative Phosphorylation(Electron Transport Chain (ETC) + Chemiosmosis)
  • Chemiosmosiscouples electron transport to ATP synthesis
  • NADH and FADH2
    • Donate e-s to ETC, which powers ATP synthesis using oxidative phosphorylation

**OCUURS IN CRISTAE

(folds of inner membrane)

what is oxidative phosphorylation
What is “oxidative phosphorylation”?
  • Recall…
    • Take H+/e-s away, molecule = “oxidized”
    • Give H+/e-s, molecule = “reduced”
    • Give phosphate, molecule = “phosphorylated”
  • So…oxidative phosphorylation = process that couples removal of H+’s/ e-’s from one molecule & giving phosphate molecules to another molecule
the pathway of electron transport
The Pathway of Electron Transport
  • In the ETC…
    • e-s from NADH and FADH2 lose energy in several steps

**NEEDS O2 TO PROCEED

(unlike glycolysis)

etc characteristics
ETC Characteristics
  • Lots of proteins (cytochromes) in cristae  increases surface area
    • 1000’s (many) copies of ETC
  • ETC carries e-’s from NADH/FADH2 O2
  • O2 = pulls e-s “down” ETC due to electronegativity (high affinity for e-s)
slide40

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesishttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesis

Inner

Mitochondrial

membrane

Oxidative

phosphorylation.

electron transport

and chemiosmosis

Glycolysis

ATP

ATP

ATP

H+

H+

H+

H+

Cyt c

Protein complex

of electron

carriers

Intermembrane

space

Q

IV

I

III

ATP

synthase

II

Inner

mitochondrial

membrane

H2O

FADH2

2 H+ + 1/2 O2

FAD+

NADH+

NAD+

ATP

ADP +

P i

(Carrying electrons

from, food)

H+

Mitochondrial

matrix

Chemiosmosis

ATP synthesis powered by the flow

Of H+ back across the membrane

Electron transport chain

Electron transport and pumping of protons (H+),

which create an H+ gradient across the membrane

Oxidativephosphorylation

Figure 9.15

Protin motive force is used!

  • Chemiosmosis and the electron transport chain
slide41

What happens at the end of the ETC chain?

  • At the end of the chain
    • Electrons are passed to oxygen, forming water
    • O2 = final e- acceptor
  • NAD delivers e- higher than FAD  NAD provides 50% more ATP
etc is a proton h pump
ETC is a Proton (H+) Pump
  • Uses the energy from “falling” e-s (exergonic flow) to pump H+’s from matrix  to outer compartment
  • A H+ (proton) gradient forms inside mitochondria
  • ETC does NOT make ATP directly but provides stage for CHEMIOSOMOSIS to occur
recall chemiosmosis
RECALL…Chemiosmosis
  • Is an energy-coupling mechanism that uses energy in the form of a H+ gradient across a membrane to drive cellular work
  • Uses ATP synthase
  • Makes ~90% of ATP in Cell Resp.
  • Proposed by Peter Mitchell (1961)
chemiosmosis the energy coupling mechanism

A rotor within the membrane spins clockwise whenH+ flows past it down the H+ gradient.

INTERMEMBRANE SPACE

H+

H+

H+

H+

H+

H+

H+

A protein anchoredin the membraneholds the knobstationary.

A rod (or “stalk”)extending into the rotor/ knob alsospins, activatingcatalytic sites inthe knob.

H+

Three catalytic sites in the stationary knobjoin inorganic

Phosphate to ADPto make ATP.

ADP

+

ATP

P i

MITOCHONDRIAL MATRIX

Figure 9.14

Chemiosmosis: The Energy-Coupling Mechanism
  • ATP synthase
    • Is the enzyme that actually makes ATP

http://www.sigmaaldrich.com/life-science/metabolomics/learning-center/metabolic-pathways/atp-synthase.html

a comparison of chemiosmosis in chloroplasts and mitochondria
A Comparison of Chemiosmosis in Chloroplasts and Mitochondria
  • Chloroplasts and mitochondria
    • Generate ATP by the SAME basic mechanism: chemiosmosis
    • But use different sources of energy to accomplish this
    • http://student.ccbcmd.edu/~gkaiser/biotutorials/cellresp/atpase_flash.html
slide46
The spatial organization of chemiosmosis
    • Differs in chloroplasts and mitochondria
  • In both organelles
    • electron transport chains generate a H+ gradient across a membrane
  • ATP synthase
    • Uses this proton-motive force to make ATP
slide47
At certain steps along the ETC
    • Electron transfer causes protein complexes to pump H+ from the mitochondrial matrix  intermembrane space
      • Inside (matrix) = low [H+]
      • Outside = high [H+]
slide48
The resulting H+ gradient…
    • Stores energy
    • Drives chemiosmosis in ATP synthase
    • Is referred to as a proton-motive force
slide49

Electron shuttles

span membrane

MITOCHONDRION

CYTOSOL

2 NADH

or

2 FADH2

2 FADH2

2 NADH

2 NADH

6 NADH

Glycolysis

Oxidative

phosphorylation:

electron transport

and

chemiosmosis

Citric

acid

cycle

2

Acetyl

CoA

2

Pyruvate

Glucose

+ 2 ATP

+ about 32 or 34 ATP

by substrate-level

phosphorylation

by substrate-level

phosphorylation

by oxidative

phosphorylation

About

36 or 38 ATP

Maximum per

glucose:

Figure 9.16

  • There are three main processes in this metabolic enterprise

+ 2 ATP

slide50
About 40% of the energy in a glucose molecule
    • Is transferred to ATP during cellular respiration, making ~36- 38 ATP
overall aerobic respiration
Overall (Aerobic Respiration)

ATP GRAND TOTAL = ~36-38 ATP per 1 GLUCOSE

ap biology ms gaynor1

AP BiologyMs. Gaynor

Chapter 9 (Part 2):

Fermentation

fermentation
Fermentation
  • Fermentation enables some cells to produce ATP without the use of oxygen (O2)
  • Cellular respiration
    • Relies on oxygen to produce ATP
  • In the absence of oxygen
    • Cells can still produce ATP through fermentation
slide54
Glycolysis
    • Can produce ATP with or without oxygen, in aerobic or anaerobic conditions
    • Couples with fermentation to produce ATP
types of fermentation
Types of Fermentation
  • Fermentation consists of
    • Glycolysis plus reactions that regenerate NAD+, which can be reused by glyocolysis
alcohol fermentation
Alcohol Fermentation
  • Pyruvate is converted to ethanol (ethyl alcohol) in two steps, one of which releases CO2
      • Ex: bacteria and yeast
slide57
In alcohol fermentation
    • Pyruvate is converted to ethanol (ethyl alcohol) in two steps, one of which releases CO2

GLUCOSE  Pyruvate  Ethanol and CO2

      • Ex: bacteria and yeast do this
slide58

P1

2 ATP

2 ADP + 2

O –

C

O

C

O

Glucose

Glycolysis

CH3

2 Pyruvate

2 NADH

2 NAD+

CO2

2

H

H

H

C

C

O

OH

CH3

CH3

2 Acetaldehyde (gets reduced by NADH. It is the oxidizing agent.)

2 Ethanol

(a) Alcohol fermentation

2 ATP

P1

2 ADP + 2

Glucose

Glycolysis

O–

C

O

C

O

2 NADH

2 NAD+

CH3

O

C

O

H

OH

C

CH3

2 Lactate

(b) Lactic acid fermentation

lactic acid fermentation
Lactic Acid Fermentation
  • During lactic acid fermentation
    • Pyruvate is reduced directly to NADH to form lactate as a waste product
    • NO CO2 is released
      • Ex #1: fungus and bacteria in dairy industry to make cheese/ yogurt
      • Ex #2: Human muscle cells
slide60

P1

2 ATP

2 ADP + 2

O –

C

O

C

O

Glucose

Glycolysis

CH3

2 Pyruvate

2 NADH

2 NAD+

CO2

2

H

H

H

C

C

O

OH

CH3

CH3

2 Acetaldehyde

(gets reduced by NADH. It is the oxidizing agent.)

2 Ethanol

(a) Alcohol fermentation

2 ATP

P1

2 ADP + 2

Glucose

Glycolysis

O–

C

O

C

O

2 NADH

2 NAD+

CH3

O

C

O

H

OH

C

CH3

2 Lactate

(b) Lactic acid fermentation

NO CO2made

2 Pyruvate

(gets reduced by NADH. It is the oxidizing agent.)

fermentation and cellular respiration compared
Fermentation and Cellular Respiration Compared
  • Both fermentation and cellular respiration
    • Use glycolysis to oxidize glucose and other organic fuels to pyruvate
slide62
Fermentation and cellular respiration
    • Differ in their final electron acceptor
      • Cell respriraition uses O2
      • Fermentation uses NAD+
  • Cellular respiration
    • Produces more ATP (~36-38 ATP)
  • Fermentation
    • Produces 2 ATP per cycle
slide63

Glucose

CYTOSOL

Pyruvate

No O2

present

Fermentation

O2 present

Cellular respiration

MITOCHONDRION

Acetyl CoA

Ethanol

or

lactate

Citric

acid

cycle

Figure 9.18

  • Pyruvate is a key juncture in catabolism
the evolutionary significance of glycolysis
The Evolutionary Significance of Glycolysis
  • Glycolysis
    • Occurs in nearly all organisms
    • Probably evolved in ancient prokaryotes before there was oxygen in the atmosphere
      • O2 in air ~2.7 bya; oldest prokaryotes ~3.5 bya
      • Also does not require organelles
slide65

Fats

Proteins

Carbohydrates

Amino

acids

Fatty

acids

Sugars

Glycerol

Glycolysis

Glucose

Glyceraldehyde-3- P

NH3

Pyruvate

Acetyl CoA

Citric

acid

cycle

Oxidative

phosphorylation

Figure 9.19

  • The catabolism of various molecules from food called “intermediates”
slide66

Glucose

AMP

Glycolysis

Stimulates

Fructose-6-phosphate

+

Phosphofructokinase

Fructose-1,6-bisphosphate

Inhibits

Inhibits

Pyruvate

Citrate

ATP

Acetyl CoA

Citric

acid

cycle

Oxidative

phosphorylation

Figure 9.20

  • The control of cellular respiration through feedback inhibition
  • PFK is an allosteric enzyme
slide67

Excellent Overall Tutorial of Cell Respiration

http://www.wiley.com/college/pratt/0471393878/student/animations/citric_acid_cycle/index.html

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