CELL RESPIRATION

Chapter 9

CP BiologyPAUL VI CATHOLIC HIGH SCHOOL

CELL RESPIRATION• Breathing and Respiration are not the same.

• Breathing allows the exchange of O2 and CO2 between an organism and its environment.

• In cellular respiration Mitochondria use O2 and produces CO2 as waste.

CO2

CO2

O2

O2Bloodstream

Muscle cells carrying out

Cellular Respiration

Breathing

Glucose O2

CO2 H2O ATP

Lungs

CELL RESPIRATIONPhotosynthesis and cellular respiration provide energy for life

– Cellular respiration makes ATP and consumes O2 during the oxidation of glucose to CO2 and H2O

– Photosynthesis uses solar energy to produce glucose and O2 from CO2 and H2O

CO2

H2O

Glucose

O2

ATP

ECOSYSTEM

Sunlight energy

Photosynthesis in chloroplasts

Cellular respiration in mitochondria

(for cellular work)

Heat energy

– Cellular respiration breaks down glucose molecules and banks their energy in ATP

– -”Glucose” used in examples for convenience. Other organic molecules are also used as “food”

– Glucose releases chemical bond energy, which the cell stores in the chemical bonds of ATP

– Multi-step process not a single reactionC6H12O6 CO26 H2O ATPs

Glucose Oxygen gas Carbon dioxide

6

Water Energy

O2 6+ + +

Figure 6.3

CELL RESPIRATION– Electrons lose potential energy during their

transfer from organic compounds to oxygen– When glucose is converted to carbon dioxide

it loses hydrogen atoms, which are added to oxygen, producing water

C6H12O6 6 O26 CO2 6 H2O

Loss of hydrogen atoms (oxidation)

Gain of hydrogen atoms (reduction)

Energy

(ATP)Glucose

+ + +

CELL RESPIRATION

GLUCOSE CATABOLISM

STAGE I: GLYCOLYSISSTAGE II: PYRUVATE OXIDATIONSTAGE III: KREBS CYCLESTAGE IV: ELECTRON TRANSPORT

CELL RESPIRATIONCellular Respiration Overview Video

Glycolysis harvests chemical energy by oxidizing glucose to pyruvate•ATP is used to prime a glucose molecule Which is split into two molecules of pyruvate

NAD NADH H

Glucose

2 Pyruvate

ATP2P2 ADP

22

2

2

+

+

Figure 6.7A

CELL RESPIRATION

CELL RESPIRATIONA.GLYCOLYSIS:

occurs in the cytoplasm of every living cell

1. Glucose Priming: changes glucose into a molecule that can be “cleaved”.

Requires 2 molecules of ATPPhosphofructokinase: commits glucose to glycolysis

– In the first phase of glycolysis ATP is used to energize a glucose molecule, which is then split in two

ATP

Glucose PREPARATORY PHASE

(energy investment)

ADP

Step

Glucose-6-phosphate

Fructose-6-phosphate

P

P

Fructose-1,6-diphosphate

ATP

ADP

PP

 Steps      –   A fuel molecule is energized, using ATP.

 Step      A six-carbon intermediate splits into two three-carbon intermediates.

1

2

3

44

1 3

Figure 6.7C

CELL RESPIRATION

2. Splitting & Rearrangement:Six carbon compound

splits to (2) 3 “C” compounds.

Fructose 1,6, Diphosphate into (2) G3P (Glyceraldehyde-3-

Phosphate)

“Substrate Level Phosphorylation” Making ATP (4 molecules/glucose)

In Glycolysis ATP is produced by

substrate-level phosphorylation

- a phosphate group is transferred from an organic molecule to ADP using an enzyme

Enzyme

Adenosine

Organic molecule(substrate)

ADP ATP

P

PP P

P

Figure 6.7B

Pyruvate

ATP

ADP

ATP

ADP

P

ATP ATP

ADP ADP

P

2-Phosphoglycerate

P

H2O H2O

Phosphoenolpyruvate(PEP)

 Steps     –      ATP and pyruvate are produced.

P 3 -Phosphoglycerate

P

P

9 9

6 6

7 7

8 8

6 9 Step     A redox reaction generates NADH.

P

NADH NADHP

P P P P

P

+H+H

ENERGY PAYOFF PHASE

Glyceraldehyde-3-phosphate(G3P)

1,3 -Diphosphoglycerate

P

5

6 9

5 5

66

7 7

88

9 9

NAD NAD

– In the second phase of glycolysis

• ATP, NADH, and pyruvate are formed

Figure 6.7C

CELL RESPIRATION 3. Oxidation: Removal of electrons

(energy) & transfer to NAD+ NADH

4. ATP Generation: 4 reactions thatconvert G3P to Pyruvate- Generates 2 ATP per Pyruvate

• At the end of Stage 1 (Glycolysis) two molecules of pyruvate have been formed.

• Pyruvate moves from the cytoplasm into the mitochondria.

NAD NADH H

Glucose2 Pyruvate

ATP2P2 ADP

22

2

2

+

+

CELL RESPIRATION

CELL RESPIRATION

Glycolysis Results in:

Glucose 2 molecules Pyruvate

Each pyruvate 2 ADP 2 ATP

Each G3P 2 NAD+ NADH

CELL RESPIRATION B. Oxidation of Pyruvate: Occurs

in mitochondrion

1. Aerobic conditions Pyruvate OXIDIZED to Acetyl CoA

2. Anaerobic conditions result in FERMENTATION REACTIONS

CELL RESPIRATION

CELL RESPIRATION

CELL RESPIRATIONFERMENTATION REACTIONS: 1.Lactic Acid Fermentation:

Pyruvate REDUCED to LactateNo CO2 removalNADH NAD+

2. Alcohol Fermentation:Fungal (Yeast) CellsPyruvate REDUCED to AlcoholCO2 Removed; NADH NAD+

CELL RESPIRATION

CELL RESPIRATION

CELL RESPIRATION

C. KREBS CYCLE: 1. “Priming” Reactions

Prepares molecule for energy extraction

Acetyl CoA (2C) joins oxaloacetate (4C) to form Citrate (6C)

Citrate isomerizes to Isocitrate

Krebs Cycle/ Citric Acid Cycle Video

CELL RESPIRATION

CELL RESPIRATION

C. KREBS CYCLE: 2. “Energy Extraction”

Oxidation rxns disassemble the molecule

•Decarboxylation Reactions

•Reduction NAD+ NADH

•Reduction FAD+ FADH2

•Regeneration oxaloacetate

CELL RESPIRATION

CELL RESPIRATIOND. ELECTRON TRANSPORT System of REDOX reactions Series of membrane electron carriers

• Ubiquinone (quinone molecule)

• Cytochromes (contain Fe++)

OXYGEN is final electron acceptor

Water is final product (two H+) attach to oxygen

CELL RESPIRATION

CELL RESPIRATIOND. ELECTRON TRANSPORT:

The movement of electrons down the concentration gradient to

O2 (the final acceptor) sends protons (H+) to the intermembrane

space ETC Video Video clip

Protons move thru ATP synthase making ATP from ADP

(Oxidative Phosphorylation)Gradients (ATP Synthase) video

Most ATP production occurs by Oxidative Phosphorylation

• Most of the carrier molecules are included in the three main protein complexes

• Carriers bind and release electrons in redox reactions

Intermembrane space

Inner mitochondrial membrane

Mitochondrial matrix

Protein complex

Electron flow

Electron carrier

NADH NAD+

FADH2 FAD

H2OATPADP

ATP synthase

H+ H+ H+

H+

H+H+

H+

H+

H+

H+

H+

H+

H+

H+

P

O2

Electron Transport Chain Chemiosmosis

.

OXIDATIVE PHOSPHORYLATION

+ 212

– Energy released redox reactions sed to pump H+ into the space between the mitochondrial membranes

– Resulting H+ gradient stores potential energy– In chemiosmosis, the H+ diffuses back through the

inner membrane through ATP synthase complexes• Driving the synthesis of ATP

Intermembrane space

Inner mitochondrial membrane

Mitochondrial matrix

Protein complex

Electron flow

Electron carrier

NADH NAD+

FADH2 FAD

H2OATPADP

ATP synthase

H+ H+ H+

H+

H+H+

H+

H+

H+

H+

H+

H+

H+

H+

P

O2

Electron Transport Chain Chemiosmosis

.

OXIDATIVE PHOSPHORYLATION

+ 212

Figure 6.10

CELL RESPIRATIONENERGY (ATP) YIELD per GLUCOSE

Glycolysis: 2 ATP (substrate level phosphorylation)

Ox. of Pyruvate: 2 NADH (3 ATP per) Krebs Cycle: 6 NADH (3 ATP per)

2 FADH2 (1-2 ATP per)2 ATP via GTP

Electron Transport: 32 ATP (oxidative phosphorylation)

CELL RESPIRATION

Overview of Aerobic Respiration

CYTOPLASM

Glycolysis

Electron Transfer

Phosphorylation

KrebsCycle ATP

ATP

2 CO2

4 CO2

2

32

water

2 NADH

8 NADH

2 FADH2

2 NADH 2 pyruvate

e- + H+

e- + oxygen

(2 ATP net)

glucose

Typical Energy Yield: 36 ATP

e-

e- + H+

e- + H+

ATP

H+

e- + H+

ATP2 4

Figure 8.3Page 135

MITOCHONRIA

6

CELL RESPIRATION

Alternate Sources for Metabolism Glycolytic pathway thru ETS is

“final common pathway” Other macromolecules can be utilized

Lipids via β-oxidation Proteins via deamination (NH3) Nucleic Acids via deamination

CELL RESPIRATION

Alternative Energy Sources

FOOD

complex carbohydrates

simple sugars

pyruvate

acetyl-CoA

glycogenfats proteins

amino acids

carbon backbones

fatty acids

glycerol

NH3

PGAL

glucose-6-phosphate

GLYCOLYSIS

KREBS CYCLE

urea

Figure 8.11Page 145

CELL RESPIRATIONControl of Glucose Catabolism

Feedback inhibition

Phosphofructokinase inhibited by: ATP levels Citrate levels

Phosphofructokinase stimulated by ADP levels AMP levels

CELL RESPIRATIONThere is a mutualistic symbioticrelationship between the productsof glycolysis and the reactants for photosynthesis.

This is an interrelationship between the mitochondria and chloroplast.

CELL RESPIRATION

Processes Are Linked

sunlight energy

water+

carbondioxide

PHOTOSYNTHESIS

AEROBICRESPIRATION

sugarmolecules

oxygen

In-text figurePage 146