Cellular Respiration

Biology 11A. Allen

http://fusionanomaly.net/mitochondria.htmlhttp://fusionanomaly.net/mitochondria.html

1

Cellular Respiration

• Cellular respiration is…

The process by which a cell breaks down sugar or other organic compounds to release energy used for cellular work; may be anaerobic or aerobic, depending on the availability of oxygen. Aerobic respiration can be summarized by the following formula:

C6H12O6 + 6O2 6H20 + 6CO2 + energy (36 ATP)

2

Glycolysis• Glycolysis is the first stage of cellular respiration.• Glycolysis has two parts; Glycolysis I & Glycolysis II. In order to

‘kick-start’ glycolysis I, activation energy is required (ATP). Sugar is split into two PGAL’s. In glycolysis II, PGAL is oxidized and ATP is produced. The overall pathway gets its name from this sugar splitting (glyco = sugar, lysis = split).

• Glycolysis occurs in the cytosol (The fluid portion of the cytoplasm, outside the organelles ).

3

An overview of Aerobic Cellular Respiration

Can you find Glycolysis?

4

Glycolysis IGlucose6-C

Glucose ~P“glucose-6-phosphate”

6-C, 1 Phosphate

ATP

ADP

P~ Fructose ~P“Fructose 1,6-bisphosphate”

6-C, 2 Phosphates

ATP

ADP

X2PGAL

AKA G3P(3-C, 1 phosphate)

• Glycolysis I is a series of endergonic reactions

1. Glucose enters the cell by diffusion

2. ATP donates a phosphate to the substrate. (1 ATP used) Glucose-6-phosphate is produced.

3. Glucose-6-phosphate is rearranged to fructose-6-phosphate (another 6-C sugar)

4. another ATP donates its phosphate (1 ATP used). Fructose 1,6-bisphosphate is produced.

5. The fructose 1,6 bisphosphate molecule is split into 2 PGALs (phosphoglyceraldehyde), a 3-carbon compound. Note PGAL is also known as glyceraldehyde 3-phosphate (G3P)

**Glycolysis I …**•2 ATP (2 ATP’s are used.)

PGALAKA G3P

Animation

11

22

33

44

5

Fructose~P“fructose-6-phosphate”

6-C, 1 Phosphate

55

Glycolysis II

X2

PGAL (G3P)(3-C, 1 phosphate)

Pyruvate (Pyruvic Acid)(3-C, 0 phosphates)

PiNAD+

NADH

• In Glycolysis II, each PGAL (2 from 1 molecule of glucose) is oxidized to release energy. This process is exergonic.

1. PGAL is oxidized. NAD takes electrons (NADH is formed). The oxidized PGAL then accepts a Pi from the cytosol. 1,3 bisphosphoglyerate (BPG) is formed

2. ADP is phosphorylated to ATP (x2) as it removes the phosphate from the substrate. 3-phosphoglycerate (PGA) is formed. (substrate level phosphorylation: when ADP removes Pi from the substrate to form ATP)

3. 3-phosphoglycerate is rearranged to 2-phosphoglycerate which is then rearranged to phosphoenolpyruvate (PEP). Water is given off in this process.

4. PEP gives a phosphate to ADP to make ATP. Pyruvate (AKA Pyruvic acid) is formed.

ADP

ATP

**Glycolysis results in a net gain of …**•2 ATP (2 ATP’s are used and 4 are produced)•2 NADH These hydrogens are transported to the mitochondria for more ATP production

Animation

11

33

44

1,3 bisphosphoglycerate (BPG)(3-C, 2 phosphates)

22ATP

ADP

3-phosphoglycerate (PGA)

(3-C, 1 phosphate)2-phosphoglycerate

(3-C, 1 phosphate)

phosphoenolpyruvate (PEP)

H2O

6

Substrate Level Phosphorylation

• The direct phosphate transfer of phosphate from an organic molecule to ADP.

IMPORTANT!

7

Think Together!Partners `A` and `B` take turns answering the questions below.

A.What is the basic difference between Glycolysis I and Glycolysis II?

B.What is the role of NAD?

A.Using your notes, describe glycolysis to your partner using the terms reduce, oxidize & phosporylation

B.How is substrate-level phosphorylation involved in glycolysis? Where?

8

Coenzyme

• A substance that enhances or is necessary for the action of enzymes. They are generally much smaller than enzymes themselves. NAD is a coenzyme that serves and an electron carrier.

9

Vocabulary GAME!

• Glucose• fructose• PGAL• Pyruvate• phosphate• Glucose-6 phosphate• NADH• ADP• endergonic

10

Circle the end products of glycolysis. Where do they go next?11

Pyruvate Oxidation (Pyruvic Acid Oxidation)

Remember, in glycolysis, glucose was oxidized to 2 pyruvate molecules. Therefore, the above biochemical pathways run twice for every molecule of glucose! Pyruvate Oxidation ONLY HAPPENS IF O2 is present!

Pyruvate(pyruvic acid)

(3-C)NAD+

NADH CO2

Acetate(Acetic acid )

(2-C)

Coenzyme A(or ‘CoA’)

acetyl coenzyme A(or ‘acetyl coA’)X2

1

2

2.2. Acetic acid combines with Acetic acid combines with coenzyme coenzyme AA to form to form acetyl coenzyme Aacetyl coenzyme A..

1.1. The The twotwo pyruvate from glycolysis pyruvate from glycolysis diffuse into the mitochondrion’s diffuse into the mitochondrion’s matrix. Here, it is oxidized by matrix. Here, it is oxidized by NADNAD++ (which is reduced to(which is reduced to NADH NADH) to make ) to make acetateacetate, a 2-carbon compound. (The , a 2-carbon compound. (The carbon is lost in the form of COcarbon is lost in the form of CO22))

Animation**Pyruvate Oxidation results in a net gain of …**•2 NADH. These hydrogens are transported to the Electron Transport Chain for more ATP production

12

Stop & Think!

• Under what conditions would the rate of pyruvate oxidation in the muscle cells of an athlete slow down?

13

Can you find Pyruvate oxidation? Where does it occur? 14

KrebsCycle

1. Acetyl coenzyme A enters the Krebs cycle and combines with Oxaloacetate (4-C), to make citrate (6-C). Coenzyme A is recycled for further use.

2. Citrate is rearranged to isocitrate (6-C)

3. NAD accepts hydrogens from isocitrate which is therefore oxidized. One molecule of CO2 is given off as isocitrate loses one carbon. α-ketoglutarate (5-C) is formed.

4. α -ketoglutarate (5-C) is oxidized to succinyl Co-A (4-C). A CO2 is removed, coenzyme A is added, and 2 hydrogen atoms reduced NAD to NADH. Succinyl C0-A is produced.

5. Succinyl Co-A (4-C) is converted to succinate (4-C). A Pi from the matrix displaces C0-A from succilyl Co-A. The phosphate is then tansfered to GDP (guanosine diphosphate) to make GTP. Then the Pi is transferred to ADP to make ATP!

CitrateCitrate (6-C)

α α --ketoglutarateketoglutarate (5-C)

SuccinateSuccinate

((4-C )

OxaloacetateOxaloacetate (4-C)

NAD

CO2

CO2

NAD

NADH

acetyl coenzyme A

(or ‘acetyl coA’)

11Coenzyme A

(or ‘CoA’)

NADH

3

44

X2

Animation

GTP GDP + Pi

ATP

ADP + Pi

IsocitrateIsocitrate (6-C)

Succinyl-CoASuccinyl-CoA

((4-C )

Co-ACo-A

Co-ACo-A

2

55

15

KrebsCycle

6. Succinate (4-C) is oxidized to fumarate (4-C). Not enough energy is released to reduce NAD, so FAD is instead reduced to FADH2.

7. Fumarate (4-C) is converted to malate (4-C).

8. Malate is oxidized to oxaloacetate (4-C). 2 hydrogens are reduced NAD to NADH. Oxaloacetate has been restored, so the cycle can continue! Yahoo!

Only 2 ATP’s have been produced from Krebs cycle.

CitrateCitrate (6-C)

α α ketoglutarateketoglutarate (5-C)

OxaloacetateOxaloacetate (4-C)

NAD

CO2

FADFADH2

NAD

NADH

acetyl coenzyme A

(or ‘acetyl coA’)

11Coenzyme A

(or ‘CoA’)

NADH

3

66

77

88

Final products of Krebs Cycle per molecule of glucose:Final products of Krebs Cycle per molecule of glucose:

3 x 2 = 3 x 2 = 6 NADH 6 NADH (to electron transport chain (to electron transport chain to make ATPto make ATP))

1 x 2 = 1 x 2 = 2 FADH2 FADH22 (to electron transport chain (to electron transport chain to make ATPto make ATP))

1 x 2 = 1 x 2 = 2 ATP2 ATP

X2

Animation

NAD44

GTP GDP + Pi

ATP

ADP + Pi

SuccinateSuccinate

((4-C )NADH

CO2

IsocitrateIsocitrate (6-C)malatemalate (4-C)

fumaratefumarate (4-C)

HH2200

Succinyl-CoASuccinyl-CoA

((4-C )

Co-ACo-A

Co-ACo-A

2

55

16

Think Together!

• Why is there a “X2” on the diagram of the Krebs Cycle?

• Krebs cycle only yields 2 ATP per molecule of glucose, but it also results in 6 NADH and 2 FADH2 produced. What do you think NADH and FADH2 is for?

17

18

Oxidative Phosphorylation (Electron Transport Chain)

• The electron transport chain is located on the inner membrane of the mitochondrion. It consists of several electron carriers which accept electrons from NADH and FADH2 (from glycolysis and Krebs cycle). It requires O2!

Animation #1

Animation #2

19

…Oxidative Phosphorylation (Electron Transport Chain)

[1] Energized electrons from Glycolysis and Krebs cycle are carried to the electron transport chain via NADH...

[2] ...and FADH2

2211

Animation #1Animation #1

Animation #2Animation #2

20

…Oxidative Phosphorylation (Electron Transport Chain)

[3] Electrons are passed through a series of electron carriers which become reduced/oxidized as they pass off the electrons [complexes I -IV]. At different places along this chain, the energy released from the electrons is used to ‘pump’ protons (H+) across the inner membrane of the mitochondrion into the intermembrane space

[4] This creates a concentration gradient in the intermembrane space.

33

44

2211NADH Dehydrogenase

(H+ pump)Cytochrome bc1 complex (H+ pump)

Cytochrome c oxidase complex (H+ pump)

Animation #1Animation #1

Animation #2Animation #2

21

…Oxidative Phosphorylation (Electron Transport Chain)

[5] The H+ ions are allowed to pass back into the matrix through ATP synthase.

[6] Using the energy from the flow of protons, ADP is united with Pi to form ATP.

Note that because NADH and FADH2 enter the electron transport chain at different locations,

they yield different amounts of ATP; NADH yields 3 ATP and FADH2 yields 2 ATP.

[7] The electrons unite with protons (H+) and oxygen at the end of the ETC to form water.

If insufficient O2 is available in the cell, the ETC will not work! What happens then?......

33

44

2211

55

66

77

NADH Dehydrogenase

(H+ pump)Cytochrome bc1 complex (H+ pump)

Cytochrome c oxidase complex (H+ pump)

Animation #1Animation #1

Animation #2Animation #2

22

Electron Transport and Chemiosmosis

NADH

H+

NAD+

H+

H+

H+

CoQ

NADH

Dehydrogenase

23

Fig. 9.15

Electron Transport and Chemiosmosis

NADH

H+

NAD+

H+

H+

H+

CoQ

Cytochrome bc1

complex Cyt CNADH

Dehydrogenase

24

Fig. 9.15

Electron Transport and Chemiosmosis

NADH

H+

NAD+

H+

H+

H+

CoQ

Cytochrome c

oxidase complex

NADH

Dehydrogenase

Cytochrome bc1

complex Cyt C

25

Fig. 9.15

Electron Transport and Chemiosmosis

NADH

H+

NAD+

H+

H+ H+

2 H+ + ½ O2

H20

Electron transport chain chemiosmosis

CoQ

NADH

Dehydrogenase

Cytochrome bc1

complex Cyt C

Cytochrome c

oxidase complex

26

Electron Transport and Chemiosmosis

NADH

H+

NAD+

H+

H+ H+

2 H+ + ½ O2

H20

H+ H+

H+ H+

H+

H+ H+

H+

H+

H+ H+

H+

H+

H+ H+

H+ H+

ADP + P ATP

27

Smokin’ Chemiosmosis & Electron Transport Animations

• http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm

• http://vcell.ndsu.nodak.edu/animations/etc/movie.htm

28

Can you see why FADH2 & NADH end in different ATP yields?

29

Cyanide Blocks the Electron Transport Chain

• Cyanide is a poison that inhibits cytochrome oxidase activity. Why can cyanide cause death?

30

Cyanide Blocks the Electron Transport Chain

• Cyanide is a poison that inhibits cytochrome oxidase activity, preventing oxygen from acting as the final electron acceptor in the electron transport chain. This disruption virtually shuts down ATP production resulting in coma and death. That is why cyanide is a poison. However, it is not poisonous to all organisms. Anaerobic bacteria, called MIT-13 actually live on cyanide – they use it the same way aerobes use oxygen.

31

Summary of Aerobic Cellular Respiration

32

33

Structural Formula of ATP

34

• Label the diagram

35

36

Net Energy Yield of Aerobic Respiration

 ATPs  NADHs  FADH2sATPs From

ETC Total ATPs

 Glycolysis  2  2  0  4  6

Pyruvic AcidOxidation

 0  2  0  6  6

 Krebs Cycle  2  6  2  22  24

           

 Total  4  10  2  32  36

AA BB CC DD EE

FF GG HH II JJ

KK LL MM NN OO

PP QQ RR SS TT

Huh?!Huh?!

37

Anaerobic vs. Aerobic Respiration • NOTE: What happens after glycolysis depends on whether or not

oxygen is present…

If O2 is absent…. If O2 is present….

Pyruvate(Pyruvic Acid)

(3-C)

NADH

NAD+ X2

Lactate(Lactic acid)(3-C)

Pyruvate Goes to the Kreb’s cycle in the mitochondria (aerobic respiration) for complete oxidation.

This process is called …

lactate (lactic acid) fermentation

Lactic acid (animals) Once thought to make muscles fatigued after Strenuous exercise)

38

Think Together!With your partner, discuss:• Does lactic acid fermentation yield any

energy?• Assume the energy demands within a cell

greatly exceeds the body’s ability to deliver oxygen. What is the point of pyruvic acid being converted to lactic acid? HINT: NAD is a limited commodity in the cell.

39

Alcoholic Fermentation (in yeast)• An anaerobic step that yeast use after glycolysis that breaks down pyruvate to

ethanol (aka ethyl alcohol) and carbon dioxide.

Pyruvate (Pyruvic Acid)

(3-C)

NADH

NAD+ X2

Ethanol (the alcohol found in beer, wine, etc.)(2-C)

Acetaldehyde (2-C)

C02

40

Alternate Pathways• Carbohydrates are your body’s nutrient of choice. • Proteins lipids and nucleic acids can also be used.

41

Protein Catabolism• Proteins are made of different

types of amino acids.• The amino groups of amino

acids are removed (deamination).

• What remains of the amino acids tar ether converted to various components of glycolysis or Krebs i.e pyruvate, acetyl CoA, alpha ketoglutarate.

• You know the rest!

42

Lipid Catabolism• Triglycerides are made of

glycerol and fatty acids. Your digestive system breaks triglycerides into these components.

• Glycerol may be converted into glucose via gluconeogenesis or to DHAP (what’s next…?)

• The fatty acids enter the matrix and undergo beta oxidation (acetyl groups are removed from the fatty acids and combine with CoA to form Acetyl CoA…

43

44

References• http://cwx.prenhall.com/bookbind/pubbooks/mcmurrygob/medialib/media_portfolio/21.html

• http://members.aol.com/BearFlag45/Biology1A/LectureNotes/lec10.html

• Nelson Biology 12

45