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. 

Space between inner and outer membranes: 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. Matrix site for Krebs' cycle link reaction ATP synthesis B. Inner Membrane site of oxidative phosphorylation e– transport chain increase surface area ATP synthesis; C. Inner Membrane Space H+ / proton build up;

8.1.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs C A B A: Matrix B: Inner membrane C: Intermembrane space C

Occurs in ________________ Is not ___________ dependent 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 Overview Major 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 G3P Pi NAD+ Removes H+ and 2 e- to become NADH Pi 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) phosphates Step 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 NET: 2 Pyruvate + 2 NADH + 2 ATP 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

In the absence of oxygen 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

Fermentation (anaerobic) From glycolysis Does not produce more ATP, but is necessary to regenerate NAD+, which must be available for glycolysis to continue Human muscles cells Bacteria Yeast

FIGURE 8-3b Fermentation (b) Bread rises as CO2 is liberated by fermenting yeast, which converts glucose to ethanol. The dough on the left rose to the level on the right in a few hours.

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 Per Glucose 2 NADH + 2 CO2 + 2 Acetyl-CoA 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 4 3

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 4 3

Cellular Respiration (Pearson)

Electron Transport Chain (Pearson)

FIGURE 8-8 The electron transport chain of mitochondria NADH and FADH2 donate their energetic electrons to the carriers of the transport chain. As the electrons pass through the transport chain, some of their energy is used to pump hydrogen ions from the matrix into the intermembrane space. This creates a hydrogen ion gradient that is used to drive ATP synthesis. At the end of the electron transport chain, the energy-depleted electrons combine with oxygen and hydrogen ions in the matrix to form water.

FIGURE 8-10 Energy harvest from the breakdown of glucose Why do we say that glucose breakdown releases "36 or 38 ATP molecules," rather than one specific number? Glycolysis produces two NADH molecules in the cytosol. The electrons from these two NADH molecules must be transported into the matrix before they can enter the electron transport chain. In most eukaryotic cells, the energy of one ATP molecule is used to transport the electrons from each NADH molecule into the matrix. Thus, the two "glycolytic NADH" molecules net only two ATPs, not the usual three, during electron transport. The heart and liver cells of mammals, however, use a different transport mechanism, one that does not consume ATP to transport electrons. In these cells, the two NADH molecules produced during glycolysis net three ATPs each, just as the "mitochondrial NADH" molecules do.

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.

IB Exam Question 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 Phosphorylation Producing ATP in the electron transport chain by adding inorganic (not attached to carbon substrate) molecules to ADP. This produces a lot of ATP.

One Glucose molecule is broken into 2 pyruvate molecules in glycolysis IB Exam Question 2. Explain the process of aerobic respiration including oxidative phosphorylation and chemiosmosis. (12 marks) In Glycolysis One Glucose molecule is broken into 2 pyruvate molecules in glycolysis Glycolysis occurs in the cytoplasm These pyruvates enter the mitochondria by active transport via a member protein; In Link Reaction Once 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

In Oxidative Phosphorylation 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) Similarities both 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; Differences anaerobic 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: Matrix site for Krebs' cycle link reaction ATP synthesis B: Innermembrane site of oxidative phosphorylation e– transport chain increase surface area ATP 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 chemiosmosis Having a folded inner membrane increases the length available to the electron transport chain, therefore maximizing ATP production during chemiosmosis

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

Figure 9.16 MITOCHONDRION CYTOSOL or Glycolysis Citric 2 acid Pyruvate Electron shuttles span membrane CYTOSOL 2 NADH 2 FADH2 6 NADH Glycolysis Glucose 2 Pyruvate Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis MITOCHONDRION by substrate-level phosphorylation by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol Maximum per glucose: About 36 or 38 ATP + 2 ATP + about 32 or 34 ATP or Figure 9.16

In the absence of oxygen 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