Cellular Respiration

• Notes: 10/8/12

8.1.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs

• Matrix: – Watery substance that contains ribosomes and

many enzymes. – These enzymes are vital for the link reaction and the

Krebs cycle. • Inner membrane:

– The electron transport chain and ATP synthase are found in this membrane.

– These are vital for oxidative phosphorylation.

8.1.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs

• Space between inner and outer membranes: – Small volume into which protons are pumped into. – Small volume high concentration gradient can be

reached very quickly. – This is vital for chemiosmosis.

• Outer membrane: – Separates the contents of the mitochondrion from

the rest of the cell. – Creates a good environment for cell respiration.

8.1.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs

• Cristae: – Tubular projections of the inner membrane – Increase the surface area for oxidative

phosphorylation. • Mitochondrial DNA

– Encode mitochondrial enzymes.• Ribosomes

– Translation of mitochondrial proteins.

8.1.6 Explain the relationship between the structure of the mitochondrion and its function

A. Matrixsite for Krebs' cycle link reaction ATP synthesis

B. Inner Membranesite of oxidative phosphorylation e– transport chain increase surface areaATP synthesis;

C. Inner Membrane SpaceH+ / proton build up;

C

A

B

C

8.1.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs

A: Matrix

B: Inner membrane

C: Intermembrane spaceC

A

B

8.1.2 Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation.

• Occurs in ________________• Is not ___________ dependent• Glucose is Phosphorylated (-__ ATP)• Lysis: phosphorylated 6-carbon sugar is

broken down into __ ____________– Glucose is ___________

• ___________ phosphorylation produces 2 ATP• NET synthesis of ___ ATP and ___ NADH

Glycolysis OverviewMajor phases

– Energy investment– Lysis– Energy harvesting

Summary of glycolysis:– Each molecule of glucose is broken down to two

molecules of pyruvate– A net of two ATP molecules and two NADH (high-

energy electron carriers) are formed

Energy Investment Phase– Glucose is phosphorylated twice– Requires the INVESTMENT of two ATP molecules

Lysis– The phosphorylated glucose is broken into two triose-

phosphate molecules (called G3P)

Energy harvesting phase– In a series of reactions, each molecule is converted

into a pyruvate, generating two ATPs per conversion, for a total of four ATPs

Energy harvesting phase

– each G3P has an inorganic phosphate group added (Pi).

– Simultaneously, NAD+ gains H and 2e- to become NADH

Pi

Pi Pi

NAD+

RemovesH+ and 2 e-

to become

NADH

G3P

Pi

8.1.2 Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation.

Step 1 - Glucose is phosphorylated. Step 2 - Lysis of hexose (6C) biphosphate into two triose (3C) phosphatesStep 3 - Each triose (3C) phosphate molecule is oxidized. Step 4 – Two pyruvate molecules (3C) are formed by removing two phosphate groups from each molecule. Type of phosphorylation?

Glycolysis

• Glucose + 2 ATP + 2 NAD+ 2 Pyruvate (C3) + 2 NADH + 2 ADP + 4 ATP

• (6C) + 2 ATP + 2 NAD+ (6C)-P-P 2 Pyruvate (C3) + 2 NADH + 4 ATP

• NET: 2 Pyruvate + 2 NADH + 2 ATP

Fermentation enables some cells to produce ATP without the use of oxygen• Cellular respiration

– Relies on oxygen to produce ATP• In the absence of oxygen

– Cells can still produce ATP through fermentation

From glycolysisFermentation(anaerobic)

Does not produce more ATP, but is necessary to regenerate NAD+, which must be available for glycolysis to continue Human muscles cells

Bacteria

Yeast

• Fermentation consists of– Glycolysis plus reactions that regenerate NAD+,

which can be reused by glycolysis• In alcohol fermentation

– Pyruvate is converted to ethanol in two steps, one of which releases CO2

• During lactic acid fermentation– Pyruvate is reduced directly to NADH to form

lactate as a waste product

Glycolysis

8.1.4 Explain aerobic respiration, including the link reaction, the Krebs cycle, the role of NADH + H+, the electron transport chain and the role of oxygen

Link Reaction

• Pyruvate enters the mitochondrion by active transport

• Inside the mitochondrion, pyruvate is oxidized and CoA is added to form acetyl-CoA

• This reaction forms one molecule of NADH and releases CO2

• Per Glucose• 2 NADH + 2 CO2 + 2 Acetyl-CoA

Link Reaction

1

2

3

4

Krebs (citric acid) Cycle

• Acetyl-CoA (2C) + oxaloacetate (6C) forms citrate (6C) and releases CoA

• High energy electron carriers NAD+ and FAD+ accept high energy electrons

• NADH and FADH2 donate electrons to the electron transport chain

• 1 ATP is produced• Oxaloacetate is regenerated by the removal of 2 CO2

molecules (originally from pyruvate/glucose)• Per Glucose• NET: 4 CO2 + 6 NADH + 2 FADH2 + 2 ATP

1

2

3

4

Cellular Respiration (Pearson)

Electron Transport Chain (Pearson)

Summary of Cellular Respiration (Pearson)

Keeping Score

ATP NADH FADH2 CO2• Gly 2 2 0 0• Link 0 2 0 2• Krebs 2 6 2 4• Totals 4 10 2 6

Carbohydrates, proteins, and lipids can be used as energy sources; metabolites involved in energy

production can be used to synthesize carbohydrates, proteins, lipids, nucleic acids, and cellular structures.

1. Outline two basic methods to make ATP through respiration. (2 marks)

Substrate-level phosphorylation Producing ATP by adding a phosphate molecule to ADP from a carbon (organic) substrate molecule. This method doesn’t produce very much ATP.

Oxidative PhosphorylationProducing ATP in the electron transport chain by adding inorganic (not attached to carbon substrate) molecules to ADP. This produces a lot of ATP.

IB Exam Question

2. Explain the process of aerobic respiration including oxidative phosphorylation and

chemiosmosis. (12 marks)

In GlycolysisOne Glucose molecule is broken into 2 pyruvate molecules in glycolysisGlycolysis occurs in the cytoplasmThese pyruvates enter the mitochondria by active transport via a member protein;

In Link ReactionOnce inside, the pyruvate is converted to acetyl CoA in the link reaction This link reaction forms NADH and CO2 Acetyl CoA enters the Citric Acid cycle

IB Exam Question

2. Explain the process of aerobic respiration including oxidative phosphorylation and

chemiosmosis. cont. (12 marks)In Citric Acid Cycle

In Citric Cycle, FAD / NAD+ accepts hydrogen and a high-energy electron to form NADH / FADH2;These electron –carriers (FADH2 / NADH) donate electrons to electron transport chain

IB Exam Question

2. Explain the process of aerobic respiration including oxidative phosphorylation and

chemiosmosis. cont. (12 marks)In Oxidative Phosphorylation

These electrons transfer their energy to member proteins (proton pumps) and actively pump protons (hydrogen ions) across inner membrane;Oxygen is the final electron acceptor and produces water as a “waste product”;The build up of protons (proton gradient) in the intermembrane space of the mitochondrion is then turned into ATP as protons flow into matrix of mitochondria through ATPase; (this step is called chemiosmosis)Producing the ATP involves adding a phosphate to ADP. This is phosphorylation.Produces 36 / 38 ATP (per glucose);

IB Exam Question

3. Explain the similarities and differences in anaerobic and aerobic cellular respiration. (8 marks)

Similaritiesboth can start with glucose;both use glycolysis;both produce ATP/energy (heat);both produce pyruvate;carbon dioxide is produced;(both start with glycolysis) aerobic leads to Krebs' cycle and anaerobic leads to fermentation;

Differencesanaerobic produces lactic acid in humans;anaerobic produces ethanol and CO2 in yeast;anaerobic occurs in cytoplasm of the cell;aerobic produces a larger amount of ATP (36-38 ATP) / anaerobic produces less ATP (2);aerobic can use other compounds / lipids / amino acids for energy whereas anaerobic cannot;

IB Exam Question

4. Be able to draw and label mitochondrion structure and describe the relation ship of it’s structure to its function.

A: Matrixsite for Krebs' cycle link reaction ATP synthesis

B: Innermembranesite of oxidative phosphorylation e– transport chain increase surface areaATP synthesis;

C: Intermembrane space

H+ / proton build up;

IB Exam Question

5. What is the relationship between the structure of

the mitochondrion and its function? (2 marks)

Having 2 membranes allows compartmentalization of hydrogen ions during chemiosmosisHaving a folded inner membrane increases the length available to the electron transport chain, therefore maximizing ATP production during chemiosmosis

IB Exam Question

About 40% of the energy in a glucose molecule is transferred to ATP

• About 40% of the energy in a glucose molecule– Is transferred to ATP during cellular respiration,

making approximately 38 ATP

• At certain steps along the electron transport chain– Electron transfer causes protein complexes to

pump H+ from the mitochondrial matrix to the intermembrane space

• The resulting H+ gradient– Stores energy– Drives chemiosmosis in ATP synthase– Is referred to as a proton-motive force

• Chemiosmosis– Is an energy-coupling mechanism that uses energy

in the form of a H+ gradient across a membrane to drive cellular work

Electron shuttlesspan membrane

CYTOSOL 2 NADH

2 FADH2

2 NADH 6 NADH 2 FADH22 NADH

Glycolysis

Glucose2

Pyruvate

2AcetylCoA

Citricacidcycle

Oxidativephosphorylation:electron transport

andchemiosmosis

MITOCHONDRION

by substrate-levelphosphorylation

by substrate-levelphosphorylation

by oxidative phosphorylation, dependingon which shuttle transports electronsfrom NADH in cytosol

Maximum per glucose:About

36 or 38 ATP

+ 2 ATP + 2 ATP + about 32 or 34 ATP

or

Figure 9.16

Fermentation enables some cells to produce ATP without the use of oxygen• Cellular respiration

– Relies on oxygen to produce ATP• In the absence of oxygen

– Cells can still produce ATP through fermentation

• Glycolysis– Can produce ATP with or without oxygen, in

aerobic or anaerobic conditions– Couples with fermentation to produce ATP

• Fermentation consists of– Glycolysis plus reactions that regenerate NAD+,

which can be reused by glyocolysis• In alcohol fermentation

– Pyruvate is converted to ethanol in two steps, one of which releases CO2

• During lactic acid fermentation– Pyruvate is reduced directly to NADH to form

lactate as a waste product

• Both fermentation and cellular respiration– Use glycolysis to oxidize glucose and other organic

fuels to pyruvate• Fermentation and cellular respiration

– Differ in their final electron acceptor• Cellular respiration

– Produces more ATP