NSB 211: DIGESTIVE SYSTEM NUTRITION
AND METABOLISM

TOPIC;

•CELLULAR RESPIRATION
Lecturer: Dr. G. Kattam Maiyoh
11/20/13
...
Learning Objectives
• Explain why cells need breakdown
biomolecules (E.G. glucose)
• Describe the basic steps in;
– Glycol...
Overview of Cellular Respiration

11/20/13

GKM/NSB 211: DIGESTIVE SYSTEM
NUTRITION AND METABOLISM/2013
Overview of Cellular Respiration
• Cellular respiration is the step-wise release of
energy from carbohydrates and other
mo...
• Metabolism refers to all the chemical reactions
of the body
– some reactions produce the energy stored in
ATP that other...
Catabolism and Anabolism
• Catabolic reactions breakdown complex
organic compounds
– providing energy (exergonic)
– glycol...
ATP Molecule & Energy
a

b
• Each cell has about 1 billion ATP molecules that last for less than
one minute
• Over half of...
Mechanisms of ATP Generation
• Phosphorylation is the addition of phospahate
group.
– bond attaching 3rd phosphate group c...
Phosphorylation in Animal Cells
• In cytoplasm (1)
• In mitochondria (2, 3 & 4)

11/20/13

GKM/NSB 211: DIGESTIVE SYSTEM
N...
• (Insert Fig. 7.4a)

11/20/13

GKM/NSB 211: DIGESTIVE SYSTEM
NUTRITION AND METABOLISM/2013

Sld 38
Carbohydrate Metabolism--In Review
• In GI tract
– polysaccharides broken down into simple sugars
– absorption of simple s...
Glucose Movement into Cells
• In GI tract and kidney tubules,
Na+/glucose symporters
• Most other cells, GluT facilitated
...
Glucose Catabolism
• Cellular respiration
– 4 steps are involved
– glucose + O2 produces
H2O + energy + CO2

• Anaerobic r...
• Each step of cellular respiration
requires a separate enzyme.
• Some enzymes use the oxidationreduction coenzyme NAD+
(n...
6 CH OPO 2−
2
3
5
O

H
4

OH

H
OH
3

H

H
2

H
1

OH

OH

glucose-6-phosphate

Glycolysis takes place in the cytosol of c...
6 CH2OH
5

H
4

OH

O

H
OH

H
2

3

H

OH

glucose

6 CH OPO 2−
2
3
5
O

ATP ADP
H
H
1

OH

Mg2+

4

H
OH

OH

3

H
1

H
...
Glycolysis & Fate of Pyruvic Acid
• Breakdown of six-carbon
glucose molecule into 2 threecarbon molecules of pyruvic
acid
...
10 Steps of Glycolysis

11/20/13
GKM/CHE 214/LEC 03/SEM 02/2011

GKM/NSB 211: DIGESTIVE SYSTEM
25-18
NUTRITION AND METABOL...
11/20/13

GKM/NSB 211: DIGESTIVE SYSTEM
NUTRITION AND METABOLISM/2013
If O2 shortage in a cell
•Pyruvic acid is reduced to lactic acid so that
NAD+ will be still available for further
glycolys...
Why does fermentation occur?
Pyruvate is reduced to lactate when
oxygen is not available because
fermentation uses NADH an...
Two types of Anaerobic Respiration

Fermentation-yeast

Lactic Acid or lactate-muscles
11/20/13

GKM/NSB 211: DIGESTIVE SY...
Advantages and Disadvantages of
Fermentation
• Fermentation can provide a rapid burst of ATP
in muscle cells, even when ox...
Efficiency of Fermentation
• Two ATP produced during fermentation are
equivalent to 14.6 kcal; complete oxidation of
gluco...
Glycolysis summary
•Inputs:
•Glucose
•2 NAD+
•2 ATP
•4 ADP + 2 P

11/20/13

•Outputs:
•2 pyruvate
•2 NADH
•2 ADP
•2 ATP (n...
Transition Reaction
• The transition reaction connects glycolysis to
the citric acid cycle, and is thus the transition
bet...
Formation of Acetyl Coenzyme A
• Pyruvic acid enters the
mitochondria with help of
transporter protein
• Decarboxylation
–...
Krebs Cycle (Citric Acid Cycle)
• Citric acid cycle – a cyclical oxidationreduction & decarboxylation reactions
occurring ...
11/20/13

GKM/NSB 211: DIGESTIVE SYSTEM
NUTRITION AND METABOLISM/2013
THE TCA

The names of the various enzymes in
the previous slide are indicated in the
figure below

GKM/NSB 211: DIGESTIVE ...
What happens in the cycle?
• During the cycle, oxidation occurs when NAD+
accepts electrons in three sites and FAD
accepts...
Products of the Krebs Cycle
• Energy stored in bonds is released step by step to form several
reduced coenzymes (NADH & FA...
Citric acid cycle inputs and outputs per
glucose molecule
•Inputs:
•2 acetyl groups
•6 NAD+
•2 FAD
•2 ADP + 2 P

•Outputs:...
The Electron Transport Chain
• Involves a series of integral
membrane proteins in the
inner mitochondrial
membrane capable...
Chemiosmosis

• Small amounts of energy
released as substances are
passed along inner
membrane
• Energy used to pump H+ io...
Steps in Electron Transport

• Carriers of electron transport chain are clustered into 3 complexes
that each act as proton...
Proton Motive Force & Chemiosmosis

•
•

Buildup of H+ outside the inner membrane creates + charge
– electrochemical gradi...
Energy yields from Glycolysis -TCA
• Glycolysis and the citric acid cycle accounts for
four ATP.
• ETC accounts for 32 or ...
• Most ATP is produced by the electron
transport system and chemiosmosis.
• Per glucose molecule, ten NADH and two
FADH2 t...
A Summary of the Energy Yield of
Aerobic Metabolism

Figure 25.7
Thank you for listening !!

11/20/13

GKM/NSB 211: DIGESTIVE SYSTEM
NUTRITION AND METABOLISM/2013
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Cellular respiration (glycolysis, TCA and ETC)

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A step by step discussion of vital processes in the release of energy from biomolecules by cells.

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  • Glycolysis takes place in the cytoplasm of almost all cells.
  • The electrons received by NAD+ are high-energy electrons that are usually carried to the electron transport system. NAD+ can be used over and over again. FAD accepts two electrons and two hydrogen ions (H+) to become FADH2.
  • Oxidation of 2 PGA by removal of water results in 2 high-energy PEP (phosphoenolpyruvate) molecules. In the final step, removal of high-energy phosphate from PEP by 2 ADP produces 2 ATP and 2 pyruvate molecules. There are four ATP molecules produced, and 2 invested in the first step of glycolysis for a net gain of 2 ATP.
  • The inputs of fermentation include glucose, 2 ATP, and 4 ADP + 2 P. Outputs are 2 lactate, or 2 alcohol and 2 CO2, and 4 ATP (net 2 ATP).
  • On each occasion, NAD+ accepts two electrons and one hydrogen to become NADH. FAD accepts two electrons and two hydrogen ions to become FADH2.
  • Cellular respiration (glycolysis, TCA and ETC)

    1. 1. NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM TOPIC; •CELLULAR RESPIRATION Lecturer: Dr. G. Kattam Maiyoh 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    2. 2. Learning Objectives • Explain why cells need breakdown biomolecules (E.G. glucose) • Describe the basic steps in; – Glycolysis, – The TCA cycle, – The electron transport chain (ETC) • Summarize the energy yield of all above steps cellular respiration 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    3. 3. Overview of Cellular Respiration 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    4. 4. Overview of Cellular Respiration • Cellular respiration is the step-wise release of energy from carbohydrates and other molecules; energy from these reactions is used to synthesize ATP molecules. • This is an aerobic process that requires oxygen (O2) and gives off carbon dioxide (CO2), and involves the complete breakdown of glucose to carbon dioxide and water. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    5. 5. • Metabolism refers to all the chemical reactions of the body – some reactions produce the energy stored in ATP that other reactions consume – all biological molecules will eventually be broken down and recycled or excreted from the body 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    6. 6. Catabolism and Anabolism • Catabolic reactions breakdown complex organic compounds – providing energy (exergonic) – glycolysis, Krebs cycle and electron transport • Anabolic reactions synthesize complex molecules from small molecules – requiring energy (endergonic) • Exchange of energy requires use of ATP (adenosine triphosphate) molecule. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013 25-6
    7. 7. ATP Molecule & Energy a b • Each cell has about 1 billion ATP molecules that last for less than one minute • Over half of the energy released from ATP is converted to heat GKM/NSB 211: DIGESTIVE SYSTEM 11/20/13 NUTRITION AND METABOLISM/2013 25-7
    8. 8. Mechanisms of ATP Generation • Phosphorylation is the addition of phospahate group. – bond attaching 3rd phosphate group contains stored energy • Mechanisms of phosphorylation – within animals • substrate-level phosphorylation in cytosol • oxidative phosphorylation in mitochondria – in chlorophyll-containing plants or bacteria • photophosphorylation. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND25-8 METABOLISM/2013
    9. 9. Phosphorylation in Animal Cells • In cytoplasm (1) • In mitochondria (2, 3 & 4) 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013 25-9
    10. 10. • (Insert Fig. 7.4a) 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013 Sld 38
    11. 11. Carbohydrate Metabolism--In Review • In GI tract – polysaccharides broken down into simple sugars – absorption of simple sugars (glucose, fructose & galactose) • In liver – fructose & galactose transformed into glucose – storage of glycogen (also in muscle) • In body cells --functions of glucose – oxidized to produce energy – conversion into something else – storage energy as triglyceride in fat 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM 25-11 NUTRITION AND METABOLISM/2013
    12. 12. Glucose Movement into Cells • In GI tract and kidney tubules, Na+/glucose symporters • Most other cells, GluT facilitated diffusion transporters move glucose into cells • Glucose 6-phosphate forms immediately inside cell (requires ATP) thus, glucose hidden in cell • Concentration gradient favorable for more glucose to enter 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013 25-12
    13. 13. Glucose Catabolism • Cellular respiration – 4 steps are involved – glucose + O2 produces H2O + energy + CO2 • Anaerobic respiration – called glycolysis (1) – Results in formation of acetyl CoA (2) is transitional step to Krebs cycle • Aerobic respiration – Krebs cycle (3) and electron transport chain (4) 11/20/13 GKM/NSB 211: DIGESTIVE SYSTE M NUTRITION AND METABOLISM/2013 25-13
    14. 14. • Each step of cellular respiration requires a separate enzyme. • Some enzymes use the oxidationreduction coenzyme NAD+ (nicotinamide adenine dinucleotide). • When a metabolite is oxidized, NAD+ accepts two electrons plus a hydrogen ion (H+) and NADH results; NAD+ can also reduce a metabolite by giving up electrons. • FAD (flavin adenine dinucleotide) is sometimes used instead of NAD+. GKM/NSB 211: DIGESTIVE SYSTEM 11/20/13 NUTRITION AND METABOLISM/2013
    15. 15. 6 CH OPO 2− 2 3 5 O H 4 OH H OH 3 H H 2 H 1 OH OH glucose-6-phosphate Glycolysis takes place in the cytosol of cells. Glucose enters the Glycolysis pathway by conversion to glucose-6-phosphate. Initially there is energy input corresponding to cleavage of two ~P bonds of ATP. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    16. 16. 6 CH2OH 5 H 4 OH O H OH H 2 3 H OH glucose 6 CH OPO 2− 2 3 5 O ATP ADP H H 1 OH Mg2+ 4 H OH OH 3 H 1 H 2 OH Hexokinase H OH glucose-6-phosphate 1. Hexokinase catalyzes: Glucose + ATP  glucose-6-P + ADP The reaction involves nucleophilic attack of the C6 hydroxyl O of glucose on P of the terminal phosphate of ATP. ATP binds to the enzyme as a complex with Mg++. GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    17. 17. Glycolysis & Fate of Pyruvic Acid • Breakdown of six-carbon glucose molecule into 2 threecarbon molecules of pyruvic acid – 10 step process occurring in cell cytosol – produces 4 molecules of ATP after input of 2 ATP – utilizes 2 NAD+ molecules as hydrogen acceptors 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013 25-17
    18. 18. 10 Steps of Glycolysis 11/20/13 GKM/CHE 214/LEC 03/SEM 02/2011 GKM/NSB 211: DIGESTIVE SYSTEM 25-18 NUTRITION AND METABOLISM/2013
    19. 19. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    20. 20. If O2 shortage in a cell •Pyruvic acid is reduced to lactic acid so that NAD+ will be still available for further glycolysis •This process is known as fermentation •Lactic acid rapidly diffuses out of cell to blood •Liver cells remove it from blood & convert it back to pyruvic acid 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    21. 21. Why does fermentation occur? Pyruvate is reduced to lactate when oxygen is not available because fermentation uses NADH and regenerates NAD+. In this way NAD+ is now free to pick up more electrons during early steps of glycolysis; this keeps glycolysis going. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    22. 22. Two types of Anaerobic Respiration Fermentation-yeast Lactic Acid or lactate-muscles 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    23. 23. Advantages and Disadvantages of Fermentation • Fermentation can provide a rapid burst of ATP in muscle cells, even when oxygen is in limited supply. • Lactate, however, is toxic to cells. • Initially, blood carries away lactate as it forms; eventually lactate builds up, lowering cell pH, and causing muscles to fatigue. • Oxygen debt occurs, and the liver must reconvert lactate to pyruvate. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    24. 24. Efficiency of Fermentation • Two ATP produced during fermentation are equivalent to 14.6 kcal; complete oxidation of glucose to CO2 and H2O represents a yield of 686 kcal per molecule of glucose. • Thus, fermentation is only 2.1% efficient compared to cellular respiration. • (14.6/686) x 100 = 2.1% 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    25. 25. Glycolysis summary •Inputs: •Glucose •2 NAD+ •2 ATP •4 ADP + 2 P 11/20/13 •Outputs: •2 pyruvate •2 NADH •2 ADP •2 ATP (net gain) GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    26. 26. Transition Reaction • The transition reaction connects glycolysis to the citric acid cycle, and is thus the transition between these two pathways. • Pyruvate is converted to a C2 acetyl group attached to coenzyme A (CoA), and CO2 is released. • During this oxidation reaction, NAD+ is converted to NADH + H+; the transition reaction occurs twice per glucose molecule. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    27. 27. Formation of Acetyl Coenzyme A • Pyruvic acid enters the mitochondria with help of transporter protein • Decarboxylation – pyruvate dehydrogenase converts 3 carbon pyruvic acid to 2 carbon fragment (CO2 produced) – pyruvic acid is oxidized so that NAD+ becomes NADH • 2 carbon fragment (acetyl group) is attached to Coenzyme A to form Acetyl coenzyme A which enter Krebs cycle – coenzyme A is derived from pantothenic acid (B vitamin). 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013 25-27
    28. 28. Krebs Cycle (Citric Acid Cycle) • Citric acid cycle – a cyclical oxidationreduction & decarboxylation reactions occurring in matrix of mitochondria • Gives off CO2 and produce one ATP per cycle; occurs twice per glucose molecule • It finishes the same as it starts (4C) – acetyl CoA (2C) enters at top & combines with a 4C compound – 2 decarboxylation reactions peel 2 carbons off again when CO2 is formed GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    29. 29. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    30. 30. THE TCA The names of the various enzymes in the previous slide are indicated in the figure below GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    31. 31. What happens in the cycle? • During the cycle, oxidation occurs when NAD+ accepts electrons in three sites and FAD accepts electrons once. • A gain of one ATP per every turn of the cycle; it turns twice per glucose. • During the citric acid cycle, the six carbon atoms in glucose become CO2. • The transition reaction produces two CO2, and the citric acid cycle produces four CO2 per molecule of glucose. 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    32. 32. Products of the Krebs Cycle • Energy stored in bonds is released step by step to form several reduced coenzymes (NADH & FADH2) that store the energy • In summary: each Acetyl CoA molecule that enters the Krebs cycle produces yields; – 2 molecules of CO2 • one reason O2 is needed – 3 molecules of NADH + H+ – one molecule of ATP – one molecule of FADH2 • Remember, each glucose produced 2 acetyl CoA molecules 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    33. 33. Citric acid cycle inputs and outputs per glucose molecule •Inputs: •2 acetyl groups •6 NAD+ •2 FAD •2 ADP + 2 P •Outputs: ½ of the above per cycle 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013 •4 CO2 •6 NADH •2 FADH2 •2 ATP
    34. 34. The Electron Transport Chain • Involves a series of integral membrane proteins in the inner mitochondrial membrane capable of oxidation/reduction • Each electron carrier is reduced as it picks up electrons and is oxidized as it gives up electrons • Small amounts of energy is released in small steps • Energy used to form ATP by chemiosmosis GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    35. 35. Chemiosmosis • Small amounts of energy released as substances are passed along inner membrane • Energy used to pump H+ ions from matrix into space between inner & outer membrane • High concentration of H+ is maintained outside of inner membrane • ATP synthesis occurs as H+ diffuses through a special H+ channel in inner membrane GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    36. 36. Steps in Electron Transport • Carriers of electron transport chain are clustered into 3 complexes that each act as proton pump (expel H+) • Mobile shuttles pass electrons between complexes • Last complex passes its electrons (2H+) to a half of O2 molecule to form a water molecule (H2O) GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    37. 37. Proton Motive Force & Chemiosmosis • • Buildup of H+ outside the inner membrane creates + charge – electrochemical gradient potential energy is called proton motive force ATP synthase enzyme within H+ channel uses proton motive force to synthesize ATP from ADP and P GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    38. 38. Energy yields from Glycolysis -TCA • Glycolysis and the citric acid cycle accounts for four ATP. • ETC accounts for 32 or 34 ATP, and the grand total of ATP is therefore 36 or 38 ATP. • Cells differ as to the delivery of the electrons from NADH generated outside the mitochondria. • If they are delivered by a shuttle mechanism to the start of the electron transport system, 6 ATP result; otherwise, 4 ATP result. GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013
    39. 39. • Most ATP is produced by the electron transport system and chemiosmosis. • Per glucose molecule, ten NADH and two FADH2 take electrons to the electron transport system; three ATP are formed per NADH and two ATP per FADH2. • Electrons carried by NADH produced during glycolysis are shuttled to the electron transport chain by an organic molecule. 7-39
    40. 40. A Summary of the Energy Yield of Aerobic Metabolism Figure 25.7
    41. 41. Thank you for listening !! 11/20/13 GKM/NSB 211: DIGESTIVE SYSTEM NUTRITION AND METABOLISM/2013

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