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TRANSCRIPT
Lecture 12-13
Chapter 6
CellularRespiration
Lecture 12-13
Chapter 6
CellularRespiration
• Long-distance runners have manySLOW FIBERS in their muscles– Slow fibers break down glucose for ATP
production aerobically (using oxygen)– These muscle cells can sustain repeated, long
contractions
How do marathon runners and sprinters differ?
• Sprinter’s muscles have more FAST FIBERS
- Fast fibers make ATP without oxygen—anaerobically- They can contract quickly and supply energy for short bursts of intense activity
The dark meat of a cooked turkey is an example of slow fiber muscleLeg muscles support sustained activity
The white meat consists of fast fibers- Wing muscles allow for quick bursts of flight
• Nearly all the cells in our body break down sugars for ATP production
• Most cells of most organisms harvest energy aerobically, like slow muscle fibers– The aerobic (+O2) harvesting of energy from
sugar is called cellular respiration– Cellular respiration yields CO2, H2O, and a large
amount of ATP
INTRODUCTION TOCELLULAR RESPIRATION
• Cellular respiration breaks down glucose molecules and banks their energy in ATP– The process uses O2 and releases CO2 and H2O
Glucose Oxygen gas Carbon dioxide
Water Energy
O2 CO2BREATHING
Lungs
CO2 O2Bloodstream
Muscle cells carrying out
CELLULAR RESPIRATION
• Breathing supplies oxygen to our cells and removes carbon dioxide
MITOCHONDRION
Mitochondria use the energy in sugars, fats and proteinsto make ATP
High-energy electrons carried by NADH
GLYCOLYSISGlucose Pyruvic
acid
KREBSCYCLE
ELECTRONTRANSPORT CHAIN
AND CHEMIOSMOSIS
MitochondrionCytoplasmic
fluid
Fig. 6.16
•Cellular respiration oxidizes sugar and produces ATP in three main stages:–GLYCOLYSIS occurs in the cytoplasm –The KREBS CYCLE (TCA) and
the ELECTRON TRANSPORT CHAINoccur in the mitochondria
Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid
Glucose Pyruvicacid
• Details of glycolysis
• Read and think about each step so that you can ‘see’the big picture
• Memorize and understand the NET REACTIONS
See Figure 6.18
PREPARATORYPHASE
(energy investment)
ENERGY PAYOFF PHASE
Steps – A fuelmolecule is energized,using ATP.
1 3
1
GlucoseStep
2
3
4
Glucose-6-phosphate
Fructose-6-phosphate
Glyceraldehyde-3-phosphate (G3P)
Step A six-carbonintermediate splits into two three-carbon intermediates.
4
Step A redoxreaction generatesNADH.
55
1,3-Diphosphoglyceric acid(2 molecules)
6
Steps – ATPand pyruvic acidare produced.
6 9 3-Phosphoglyceric acid(2 molecules)7
2-Phosphoglyceric acid(2 molecules)8
2-Phosphoglyceric acid(2 molecules)
9
(2 moleculesper glucose molecule)
Pyruvic acid
Fructose-1,6-diphosphate
6.7 Using Coupled Reactions to Make ATP• Glycolysis is the first stage in cellular respiration
– Takes place in the cytoplasm – Occurs in the presence or absence of oxygen– Involves ten enzyme-catalyzed reactions
• These convert the 6-carbon glucose into two 3-carbon molecules of pyruvate
1 6-carbon glucose(Starting material)
6-carbon sugar diphosphate
P P
2 ATP
Priming reactions
2
6-carbon sugar diphosphate
P P
3-carbon sugarphosphate
P
3-carbon sugarphosphate
P
Cleavage reactions
3
3-carbonpyruvate
3-carbonpyruvate
NADH
ATP2
3-carbon sugarphosphate
P
3-carbon sugarphosphate
P
NADH
ATP2
Energy-harvesting reactions
Fig. 6.17
6.8 Harvesting Electrons from Chemical Bonds
• The oxidative stage of aerobic respiration occurs in the mitochondria
• It begins with the conversion of pyruvate into acetyl coA
Depending on needs
Fig. 6.20
• Takes place in the mitochondria• It consists of nine enzyme-catalyzed reactions that can be divided into three stages
– 1 Acetyl CoA binds a 4-carbon molecule producing a 6-carbon molecule– 2 Two carbons are removed as CO2– 3 The four-carbon starting material is regenerated
• Krebs cycle enzymes strip away electrons and H+ from each acetyl group generatingmany NADH and FADH2 molecules
The Krebs Cycle
1CoA–
(Acetyl-CoA)
4-carbon molecule(Starting material) 6-carbon
molecule
2
6-carbon molecule
4-carbonmolecule
5-carbonmolecule
NADH
NADH
CO2
ATP
CO2
3
NADH
FADH2
4-carbon molecule(Starting material)
4-carbon molecule
Fig. 6.22
6.9 Using the Electrons to Make ATP
Energy Transferin the Mitochondria
• Glucose is entirely consumed in the process of cellular respiration
• Glucose is converted to six molecules of CO2– used to buffer the pH of blood– breathe out as waste
• The glucose energy is transformed to– 4 ATP molecules– 10 NADH electron carriers– 2 FADH2 electron carriers
• THE REDUCING POWER INTHESE ELECTRON CARRIERSIS USED TO MAKE 32 ATPMOLECULES IN THEELECTRON TRANSPORT CHAIN
6.9 Using the Electrons to Make ATP
Mitochondrial matrix
Intermembrane spacePyruvate from
cytoplasm
NADH
Acetyl-CoA
FADH2
NADH
Krebscycle
ATP2
CO2
e–
e–
1. Electrons are harvestedand carried to the transportsystem.
e–
2. Electrons provideenergy to pumpprotons across themembrane.
H+ H+
H+
O2O2
1
2
H2O
3. Oxygen joins withprotons to form water.
+ 2H+
H+ATP32
4. Protons diffuse backin, driving the synthesisof ATP.
ATPsynthase
Fig. 6.26 An overview of the electron transport chain and chemiosmosis
6.9 Using the Electrons to Make ATP
Fig. 6.25
• In chemiosmosis,the H+ ions diffuse throughATP synthase complexes,which capture the energyto make ATP
• The electrons carried by NADH and FADH2are donated to the electron transport chain
• Energy released by the electrons is used topump H+ into the space between themitochondrial membranes
• Chemiosmosis in the mitochondrion
Figure 6.12
Intermembranespace
Innermitochondrialmembrane
Mitochondrialmatrix
Proteincomplex
Electroncarrier
Electronflow
ELECTRON TRANSPORT CHAIN ATP SYNTHASE
• Food sources, other than sugars, can be used in cellular respiration
• These complex molecules are first digested into simpler subunits– Polysaccharides can be hydrolyzed to
monosaccharides and then converted to glucose for glycolysis
– Proteins can be digested to amino acids, which are chemically altered and then used in the Krebs cycle
– Fats are broken up and fed into glycolysis and the Krebs cycle
Other Sources of Energy
Fig. 6.27 How cells obtain energy from foods
• The use of inorganic terminal electron acceptors other than oxygen
Anaerobic Respiration
Sulfur bacteria
Methanogens
Reduced Product
Terminalelectron
acceptor
Organism
CO2ArchaeaCH4
Methane
SO4Sulfate
H2SHydrogen
sulfide
• The use of organic terminal electron acceptors• The electrons carried by NADH are donated to a derivative of pyruvate
– This allows the regeneration of NAD+ that keeps glycolysis running• Two types of fermentation are common among eukaryotes
– Lactic fermentation and Ethanolic fermentation
Fermentation
Fig. 6.19
Occurs in animal
muscle cells
Occurs in yeast
cells
BIG PICTURELife from the Sun
• Nearly all the chemical energy that organisms use comes ultimately from sunlight
Sunlight energy
Chloroplasts,site of photosynthesis
CO2+
H2O
Glucose+O2Mitochondria
sites of cellularrespiration
(for cellular work)
Heat energy
This is aVERY IMPORTANT
cycle