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Respiration. Cellular respiration is the process by which cells transfer chemical energy from sugar molecules to ATP molecules. As this happens cells release CO 2 and use up O 2 Respiration can be AEROBIC or ANAEROBIC. O 2. Breathing. CO 2. Lungs. O 2. CO 2. Bloodstream.

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respiration
Respiration
  • Cellular respiration is the process by which cells transfer chemical energy from sugar molecules to ATP molecules.
  • As this happens cells release CO2 and use up O2
  • Respiration can be AEROBIC or ANAEROBIC
slide2
O2

Breathing

CO2

Lungs

O2

CO2

Bloodstream

Muscle cells carrying out

Cellular Respiration

Glucose + O2

CO2 +H2O +ATP

0

Breathing supplies oxygen to our cells and removes carbon dioxide

  • Breathing provides for the exchange of O2 and CO2

Between an organism and its environment

Figure 6.2

slide3
0.

The human body uses energy from ATP for all its activities.

  • ATP powers almost all cellular and body activities
cellular respiration
CELLULAR RESPIRATION
  • Cellular respiration is an energy- releasing process. It produces ATP
  • ATP is the universal energy source

Making ATP

  • Plants make ATP during photosynthesis
  • Cells of all organisms make ATP by breaking down carbohydrates, fats, and protein
slide5
Phosphategroups

Adenosine diphosphate

Adenosine Triphosphate

H2O

+

P

Energy

P

P

P

P

P

+

Hydrolysis

Adenine

Ribose

ATP

ADP

  • The energy in an ATP molecule
    • Lies in the bonds between its phosphate groups

Figure 5.4A

redox reactions
REDOX REACTIONS
  • The loss of electrons is called oxidation.
  • The addition of electrons is called reduction
overview of aerobic respiration
Overview of Aerobic Respiration

C6H12O6 + 6O2 6CO2 + 6H2O +ATP

glucose oxygen carbon water

dioxide

slide8
Loss of hydrogen atoms (oxidation)

C6H12O6

6 CO2

Energy

6 O2

+

6 H2O

+

+

Glucose

(ATP)

Gain of hydrogen atoms (reduction)

0

  • When glucose is converted to carbon dioxide
    • It loses hydrogen atoms, which are added to oxygen, producing water

Figure 6.5A

stages of cellular respiration
0STAGES OF CELLULAR RESPIRATION

Overview: Cellular respiration occurs in three main stages

  • Glycolysis
  • Krebs Cycle or Citric Acid Cycle
  • Electron Transport Chain or Phosphorylation
slide10
0
  • Stage 1:

Glycolysis

  • No oxygen needed. It is universal
    • Occurs in the cytoplasm
    • Breaks down glucose into pyruvate, producing a small amount of ATP (2)
glycolysis
GLYCOLYSIS
  • Where?: In the cytosol of all cells.

Both aerobic and anaerobic respiration begin with glycolysis.

  • What happens?: The cell harvests energy by oxidizing glucose to pyruvate.
  • One molecule of glucose (6 carbons) is converted to two pyruvate molecules (3 carbons) through a series of 10 reactions mediated by enzymes.
  • Result:

2 pyruvate molecules (each with a 3 carbon backbone)

2 NADH molecules. Carrier that picks up hydrogens stripped from glucose.

2 ATP molecules. 4 are made but cells use 2 to start glycolysis so net gain is 2

preparatory steps to enter the krebs cycle
Preparatory steps to enter the Krebs cycle
  • The 2 pyruvate molecules enter the mitochondrion and an enzyme strips one carbon from each pyruvate.
  • This two carbon molecule is picked up by Co-enzyme A in preparation for the Krebs cycle.
  • This is acetyl CoA. This is what enters the Krebs cycle: C-C-CoA (oxaloacetate)
slide14
0

Stage 2 :

The citric acid cycle or Krebs cycle

  • Takes place in the mitochondria
  • Completes the breakdown of glucose (catabolism), producing a small amount of ATP (2ATP)
  • Pyruvate is broken down to carbon dioxide
  • More coenzymes are reduced .Supplies the third stage of cellular respiration with electrons (hydrogen carriers such as NADH)
krebs cycle or citric acid cycle
KREBS CYCLE or citric acid cycle
  • This cycle involves a series of 8 steps forming and rearranging. Each time it releases CO2 and NADH carries hydrogen to the last step. 6 CO2are given off as waste (this is the most oxidized form of Carbon)In total:

6 CO2

6 NADH are produced and

2 FADH and only

2 ATP

slide17
0

Stage 3:

Oxidative phosphorylation or electron transport chain

  • Occurs in the mitochondria (inner membrane)
  • Uses the energy released by “falling” electrons to pump H+ across a membrane
  • Harnesses the energy of the H+ gradient through chemiosmosis, producing ATP
chemiosmosis
Chemiosmosis

Chemiosmosis is an energy coupling mechanism that uses energy stored on H+

Chemiosmosis is the coupling of the REDUX reactions of the electron transport chain to ATP synthesis

slide19
NADH

ATP

NAD+

+

2e

Controlled release of energy for synthesis of ATP

H+

Electron transport chain

2e

1

O2

2

H+

2

H2O

0

  • NADH passes electrons to an electron transport chain
  • As electrons “fall” from carrier to carrier and finally toO2
    • Energy is released in small quantities

Figure 6.5C

electron transport chain
ELECTRON TRANSPORT CHAIN
  • Electron transport systems are embedded (proteinmolecules) in inner mitochondrial membranes (cristae)
  • NADH and FADH2 give up electrons that they picked up in earlier stages to electron transport system
  • Electrons are transported through the system
  • The final electron acceptor is oxygen. The hydrogen combines with the oxygen to form water
electron transport chain21
.

H+

H+

H+

H+

H+

Protein complex

H+

H+

ATP synthase

H+

Electron carrier

H+

Intermembrane space

Inner mitochondrial membrane

FADH2

FAD

Electron flow

1

+2

O2

H+

NAD+

NADH

2

H+

H+

Mitochondrial matrix

+

P

ATP

ADP

H+

H2O

H+

Chemiosmosis

Electron Transport Chain

OXIDATIVE PHOSPHORYLATION

Figure 6.10

Electron transport chain
how much total atp energy was produced
HOW MUCH TOTAL ATP(ENERGY) WAS PRODUCED?
  • Glycolysis

2 ATP formed by substrate-level phosphorylation

  • Krebs cycle and preparatory reactions

2 ATP formed by substrate-level phosphorylation

  • Electron transport phosphorylation

32-34 ATP formed

2+2+34=38

Most ATP production occurs by oxidative phosphorylation or electron transport chain

why oxygen
WHY OXYGEN?
  • Electron transport phosphorylation requires the presence of oxygen
  • Oxygen withdraws spent electrons from the electron transport system, then combines with H+ to form water
web site tutorials to check
Web site tutorials to check:
  • http://www.sp.uconn.edu/~terry/Common/respiration.html
  • http://www2.nl.edu/jste/electron_transport_system.htm
  • http://www.wisc-online.com/objects/MBY2604/MBY2604.swf
how efficient is cellular respiration
How efficient is cellular respiration?
  • Only about 40% efficient.

In other words, a call can harvest about 40% of the energy stored in glucose.

  • Most energy is released as heat
evolution of cellular respiration
Evolution of cellular respiration
  • When life originated, atmosphere had little oxygen
  • Earliest organisms used anaerobic pathways
  • Later, photosynthesis increased atmospheric oxygen
  • Cells arose that used oxygen as final acceptor in electron transport (without oxygen to act as the final hydrogen acceptor the cells will die)
fermentation
Fermentation
  • Fermentation allows some cells to produce ATP without oxygen.
  • This is Anaerobic respiration
anaerobic respiration fermentation is an anaerobic alternative to cellular respiration
ANAEROBIC RESPIRATIONFermentation is an anaerobic alternative to cellular respiration
  • Do not use oxygen
  • Produce less ATP( 2) than aerobic pathways
  • Two types. One produces alcohol and the other lactic acid as waste products
    • Fermentation pathways
    • Anaerobic electron transport
fermentation34
Fermentation
    • Under anaerobic conditions, many kinds of cells

can use glycolysis alone to produce small amounts of ATP

  • Begin with glycolysis
  • Do not break glucose down completely to carbon dioxide and water
  • Yield only the 2 ATP from glycolysis
  • Steps that follow glycolysis serve only to regenerate NAD+
yeast
Yeast
  • Single-celled fungi
  • Carry out alcoholic fermentation
  • Saccharomyces cerevisiae
    • Baker’s yeast
    • Carbon dioxide makes bread dough rise
  • Saccharomyces ellipsoideus
    • Used to make beer and wine
our muscle cells
Our muscle cells…
  • In the absence of oxygen our muscles can carry out fermentation, but the pyruvate from glycolysis is turned into lactic acid instead of alcohol
slide37
NADH

NAD+

2

NAD+

NADH

2

2

2

GLYCOLYSIS

2 ADP + 2

CO2

released

2

P

2

ATP

2 Ethanol

Glucose

2 Pyruvate

Figure 6.13B

0

  • In alcohol fermentation
    • NADH is oxidized to NAD+ while converting pyruvate to CO2 and ethanol

Figure 6.13C

two stages of glycolysis
Two stages of glycolysis
  • Energy-requiring steps
    • ATP energy activates glucose and its six-carbon derivatives
  • Energy-releasing steps
    • The products of the first part are split into three-carbon pyruvate molecules
    • ATP and NADH form
slide40
H+

2

+

2

NAD+

2

NADH

Glucose

2 Pyruvate

+

2

2

P

ATP

2 ADP

0

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

Figure 6.7A

slide41
4

3

1

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

PREPARATORY PHASE(energy investment)

 Steps      –   A fuel molecule is energized, using ATP.

Glucose

ATP

Step

1

ADP

Glucose-6-phosphate

P

2

P

Fructose-6-phosphate

ATP

3

ADP

P

Fructose-1,6-diphosphate

P

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

4

Figure 6.7C

slide42
5

5

6

6

7

7

8

8

9

9

  • In the second phase of glycolysis
    • ATP, NADH, and pyruvate are formed

P

P

Glyceraldehyde-3-phosphate(G3P)

 Step     A redox reaction generates NADH.

5

6

9

ENERGY PAYOFF PHASE

NAD

NAD

P

6

6

P

NADH

NADH

+H

+H

P

P

P

P

1,3-Diphosphoglycerate

 Steps     –      ATP and pyruvate are produced.

9

6

ADP

ADP

7

7

ATP

ATP

P

3-Phosphoglycerate

P

P

P

8

8

2-Phosphoglycerate

H2O

H2O

P

P

Phosphoenolpyruvate(PEP)

9

9

ADP

ADP

ATP

ATP

Pyruvate

net energy yield from glycolysis
Net Energy Yield from Glycolysis

Energy requiring steps:

2 ATP invested

Energy releasing steps:

2 NADH formed

4 ATP formed

Glycolysis net yield is 2 ATP and 2 NADH

preparatory reactions before the krebs cycle
Preparatory reactions before the Krebs cycle
  • Preparatory reactions
    • Pyruvate is oxidized into two-carbon acetyl units and carbon dioxide
    • NAD+ is reduced

pyruvate + coenzyme A + NAD+

acetyl-CoA + NADH + CO2

  • One of the carbons from pyruvate is released in CO2
  • Two carbons are attached to coenzyme A and continue on to the Krebs cycle
slide45
+ H+

NADH

NAD+

CoA

Pyruvate

Acetyl CoA(acetyl coenzyme A)

CO2

Coenzyme A

Figure 6.8

Pyruvate is gets ready for the citric acid cycle

  • Prior to the citric acid cycle
    • Enzymes process pyruvate, releasing CO2 and producing NADH and acetyl CoA

2

1

3

krebs cycle
Krebs cycle
    • The acetyl units are oxidized to carbon dioxide
    • NAD+ and FAD are reduced

Products:

  • Coenzyme A
  • 2 CO2
  • 3 NADH
  • FADH2
  • ATP
slide47
Acetyl CoA

CoA

CoA

CO2

2

CITRIC ACID CYCLE

NAD+

3

FADH2

3

FAD

NADH

+

3 H+

ADP +

ATP

P

0

The citric acid cycle (Krebs)completes the oxidation of organic fuel (glucose), generating many NADH and FADH2 molecules

  • In the citric acid cycle
    • The two-carbon acetyl part of acetyl CoA is oxidized

Figure 6.9A

for each turn of the krebs cycle
For each turn of the Krebs cycle
  • Two CO2 molecules are released (All of the carbon molecules in pyruvate end up in carbon dioxide)
  • Three NADH and one FADH2 (Coenzymes are reduced, they pick up electrons andhydrogen)
  • One molecule of ATP is formed for each turn so the net yield of ATP for the Krebs or Citric Acid cycle is 2 ATP molecules.
what happened to co enzymes nad and fad during the first two stages
What happened to co-enzymes (NAD and FAD) during the first two stages?

Co-enzymes were reduced (gainedelectrons)

  • Glycolysis 2 NADH
  • Preparatory

reactions 2 NADH

  • Krebs cycle 2 FADH2 + 6 NADH
  • Total 2 FADH2 + 10 NADH
slide51
0

Most ATP production occurs by oxidative phosphorylation or electron transport chain

  • Electrons from NADH and FADH2
    • Travel down the electron transport chain to oxygen, which picks up H+ to form water
  • Energy released by the redox reactions
    • Is used to pump H+ into the space between the mitochondrial membranes
electron transport chain or phosphorylation
ELECTRON TRANSPORT CHAIN OR PHOSPHORYLATION
  • Takes place in the mitochondria
  • Coenzymes deliver electrons to electron transport systems
  • Electron transport sets up H+ ion gradients
  • Flow of H+ down gradients powers ATP formation
  • The net yield from oxidative phosphorilation is 32 to 34 ATP molecules
slide54
.

H+

H+

H+

H+

H+

Protein complex

H+

H+

ATP synthase

H+

Electron carrier

H+

Intermembrane space

Inner mitochondrial membrane

FADH2

FAD

Electron flow

1

+2

O2

H+

NAD+

NADH

2

H+

H+

Mitochondrial matrix

+

P

ATP

ADP

H+

H2O

H+

Chemiosmosis

Electron Transport Chain

OXIDATIVE PHOSPHORYLATION

Figure 6.10

0

  • In chemiosmosis, the H+ diffuses back through the inner membrane through ATP synthase complexes
    • Driving the synthesis of ATP
certain poisons interrupt critical events in cellular respiration
Cyanide, carbon monoxide

Rotenone

Oligomycin

H+

H+

H+

ATPSynthase

H+

H+

H+

H+

H+

H+

DNP

FAD

FADH2

1

+

O2

2

H+

NADH

NAD+

2

H+

+

ATP

P

ADP

H+

H2O

H+

Electron Transport Chain

Chemiosmosis

0

Certain poisons interrupt critical events in cellular respiration
  • Various poisons
    • Block the movement of electrons
    • Block the flow of H+ through ATP synthase
    • Allow H+ to leak through the membrane

Figure 6.11

slide56
0
  • Review: Each molecule of glucose yields many molecules of ATP
    • Oxidative phosphorylation, using electron transport and chemiosmosis
      • Produces up to38 ATP molecules for each glucose molecule that enters cellular respiration

Electron shuttleacross membrane

Mitochondrion

2

2

NADH

NADH

Cytoplasm

(or 2 FADH2)

2

2

6

FADH2

NADH

NADH

OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis)

GLYCOLYSIS

2 AcetylCoA

2

CITRIC ACIDCYCLE

Glucose

Pyruvate

+ about 34 ATP

+ 2 ATP

+ 2 ATP

by substrate-level phosphorylation

by oxidative phosphorylation

by substrate-level phosphorylation

About38 ATP

Maximum per glucose:

Figure 6.12

anaerobic electron transport
Anaerobic Electron Transport
  • Carried out by certain bacteria
  • Electron transport system is in bacterial plasma membrane
  • Final electron acceptor is compound from environment (such as nitrate), NOT oxygen
  • ATP yield is almost as good as from aerobic respiration
interconnections between molecular breakdown and synthesis
0INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS
  • Cells use many kinds of organic molecules as fuel for cellular respiration
slide59
Food, such aspeanuts

Carbohydrates

Fats

Proteins

Sugars

Fatty acids

Amino acids

Glycerol

Aminogroups

OXIDATIVEPHOSPHORYLATION(Electron Transportand Chemiosmosis)

CITRICACIDCYCLE

AcetylCoA

Pyruvate

Glucose

G3P

GLYCOLYSIS

ATP

0

  • Carbohydrates, fats, and proteins can all fuel cellular respiration
    • When they are converted to molecules that enter glycolysis or the citric acid cycle

Figure 6.14

how is energy obtained from proteins
How is energy obtained from proteins?
  • Proteins are broken down to amino acids
  • Amino acids are broken apart
  • Amino group is removed, ammonia forms, is converted to urea and excreted
  • Carbon backbones can enter the Krebs cycle
how do we get energy from fats
How do we get energy from fats?
  • Most stored fats are triglycerides
  • Triglycerides are broken down to glycerol and fatty acids
  • Glycerol is converted to PGAL, an intermediate of glycolysis
  • Fatty acids are broken down and converted to acetyl-CoA, which enters Krebs cycle
le 9 19
Proteins

Carbohydrates

Fats

Amino

acids

Sugars

Glycerol

Fatty

acids

LE 9-19

Glycolysis

Glucose

Glyceraldehyde-3-

P

NH3

Pyruvate

Acetyl CoA

Citric

acid

cycle

Oxidative

phosphorylation

slide63
ATP needed to drive biosynthesis

ATP

GLUCOSE SYNTHESIS

CITRIC

ACID

CYCLE

Acetyl

CoA

Glucose

Pyruvate

G3P

Amino

groups

Fatty

acids

Amino acids

Sugars

Glycerol

Carbohydrates

Proteins

Fats

Cells, tissues, organisms

0

  • Food molecules provide raw materials for biosynthesis
    • Cells use some food molecules and intermediates from glycolysis and the citric acid cycle as raw materials
    • This process of biosynthesis
      • Consumes ATP

Figure 6.15

slide64
0
  • The fuel for respiration ultimately comes from photosynthesis
    • All organisms
      • Can harvest energy from organic molecules
    • Plants, but not animals
      • Can also make these molecules from inorganic sources by the process of photosynthesis

Figure 6.16

electrons fall from organic molecules to oxygen during cellular respiration
Electrons “fall” from organic molecules to oxygen during cellular respiration
  • In cellular respiration, glucose and other fuels are oxidized, releasing energy.
  • In the summary equation of cellular respiration: C6H12O6 + 6O2 6CO2 + 6H2O+ ATP
  • Glucose is oxidized (loses electrons), oxygen is reduced ( gains electrons)
  • Cellular respiration does not oxidize glucose in a single step that transfers all the hydrogen in the fuel to oxygen at one time.

glucose is broken down gradually in a series of steps, each catalyzed by a specific enzyme

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