Transcript AP Biology Ch. 9 Cellular Respiration Ppt.
Organisms must take in energy from outside sources.
Energy is incorporated into organic molecules such as glucose in the process of photosynthesis.
Glucose is then broken down in cellular respiration. The energy is stored in ATP.
Fig. 9-2 The Flow of Energy from Sunlight to ATP
ECOSYSTEM Light energy CO 2 + H 2 O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules+ 2 ATP ATP powers most cellular work Heat energy
Energy in food is stored as carbohydrates (such as glucose), proteins & fats. Before that energy can be used by cells, it must be released and transferred to ATP.
Aerobic Cellular Respiration: the process that releases energy by breaking down food (glucose) molecules in the presence of oxygen.
Formula: C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O +~ 36 ATP Fermentation: the partial breakdown of glucose without oxygen. It only releases a small amount of ATP. Glycolysis: the first step of breaking down glucose—it splits glucose (6C) into 2 pyruvic acid molecules (3C each)
The transfer of electrons during chemical reactions releases energy stored in organic compounds such as glucose.
Oxidation-reduction reactions are those that involve the transfer of an electron from one substance to another.
• Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions In oxidation, one substance loses electrons, or is oxidized In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) Na will easily lose its outer electron to Cl . Why?
In this reaction, which atom is oxidized?
Which is reduced?
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Redox Reactions of Cellular Respiration
In cellular respiration, glucose is broken down and loses its electrons in the process. The glucose becomes oxidized and the Oxygen is reduced.
becomes oxidized becomes reduced
In cellular respiration, glucose is broken down in a series of steps.
As it is broken down, electrons from glucose are transferred to NAD+, a coenzyme When it receives the electrons, it is converted to NADH. NADH represents stored energy that can be used to make ATP
NADH passes the electrons to the electron transport chain, a series of proteins embedded in the inner membrane of the mitochondria.
The electrons (and the energy they carry) are transferred from one protein to the next in a series of steps.
Energy is released a little at a time, rather than one big explosive reaction:
H 2 + 1 / 2 O 2 ( from food via NADH) 2 H + 2 H + 2 e – Controlled release of energy for synthesis of ATP 1 / 2 O 2 Explosive release of heat and light energy 1 / 2 O 2 ( a) Uncontrolled reaction (b) Cellular respiration
Cellular respiration has three stages: Glycolysis (breaks down glucose into two molecules of pyruvate) The Citric Acid cycle/Kreb’s Cycle (completes the breakdown of glucose)
Electron Transport Chain and Oxidative
phosphorylation (accounts for most of the ATP synthesis) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
An Overview of Cellular Respiration –Part 1
Electrons carried via NADH Glucose Glycolysis Pyruvate Cytosol ATP Substrate-level phosphorylation
An Overview of Cellular Respiration —Part 2
Electrons carried via NADH Electrons carried via NADH and FADH 2 Glucos e Glycolysis Pyruvate Mitochondrion Citric acid cycle Cytosol ATP Substrate-level phosphorylation ATP Substrate-level phosphorylation
An Overview of Cellular Respiration —Part 3
Electrons carried via NADH Glucose Glycolysis Pyruvate Mitochondrion Citric acid cycle Electrons carried via NADH and FADH 2 Oxidative phosphorylation: electron transport and chemiosmosis Cytosol ATP Substrate-level phosphorylation ATP Substrate-level phosphorylation ATP Oxidative phosphorylation
Substrate-level phosphorylation: Phosphate is added to ADP to make ATP by using an enzyme: Oxidative phosphorylation: Phosphate is added to ADP to make ATP by ATP Synthase—a protein embedded in the mitochondria membrane (requires O 2 ) WAY MORE EFFICIENT!! PRODUCES LOTS MORE ATP!
“Glyco”=sugar; “lysis”=to split In this first series of reactions, glucose (C6) is split into two molecules of pyruvic acid (C3).
This occurs in the cytoplasm of cells and does not require oxygen.
This releases only 2 ATP molecules, not enough for most living organisms.
l http://highered.mcgraw hill.com/sites/0072507470/student_view0/cha pter25/animation__how_glycolysis_works.htm
Energy investment phase Glucose 2 ADP + 2 P Energy payoff phase 4 ADP + 4 P 2 NAD + + 4 e – + 4 H + Net Glucose 4 ATP formed – 2 ATP used 2 NAD + + 4 e – + 4 H +
Glycolysis
2 ATP used 4 ATP formed 2 NADH + 2 H + 2 Pyruvate + 2 H 2 O 2 Pyruvate + 2 H 2 O 2 ATP 2 NADH + 2 H +
The Citric Acid Cycle (also called the Kreb’s Cycle) completes the breakdown of pyruvate and the release of energy from glucose.
It occurs in the matrix of the mitochondria.
In the presence of oxygen, pyruvate enters the mitochondria.
Before the pyruvate can enter the Citric Acid Cycle, however, it must be converted to Acetyl Co-A. Some energy is released and NADH is formed.
Converting Pyruvate to Acetyl CoA:
CYTOSOL MITOCHONDRION NAD + NADH + H + 2 Pyruvate Transport protein 1 CO 2 3 Coenzyme A Acetyl CoA
The Acetyl Co-A enters the Citric Acid Cycle in the matrix of the mitochondria.
The Citric Acid cycle breaks down the Acetyl Co-A in a series of steps, releasing CO 2 It produces 1 ATP, 3 NADH, and 1 FADH turn.
2 per
The Citric Acid Cycle • • • The Citric Acid cycle (also called the Krebs Cycle) has eight steps, each catalyzed by a specific enzyme The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate (Citric Acid). The next seven steps decompose the citrate (Citric Acid) back to oxaloacetate, making the process a cycle Oxaloacetate + Acetyl CoA Citric Acid
The Citric Acid Cycle:
Acetyl CoA CoA —SH NADH +H + NAD + 8 Oxaloacetate 1 H 2 O 2 H 2 O Malate Citrate 7 Citric acid cycle Isocitrate NAD + 3 NADH + H + C O 2 Fumarate CoA —SH
-Keto glutarate 4 6 CoA —SH FADH 2 5 FAD Succinate GTP GDP P i Succinyl CoA ADP ATP NAD + NADH + H + C O 2
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• • Each Citric Acid Cycle only produces 1 ATP molecule. The rest of the energy from pyruvate is in the NADH and FADH 2 .
The NADH and FADH 2 produced by the Citric Acid cycle relay electrons extracted from food to the electron transport chain.
The electron transport chain is in the cristae of the mitochondrion Most of the chain’s components are proteins, which exist in multiprotein complexes The carriers alternate reduced and oxidized states as they accept and donate electrons Electrons drop in free energy as they go down the chain and are finally passed to O 2 , forming H 2 O Oxygen is the final electron acceptor.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Electron Transport Chain
NADH 50 40 30 2
e
– NAD + FADH 2 2
e
– FAD FMN Fe•S
Q FAD Fe•S
Cyt b
Multiprotein complexes Fe•S Cyt c 1 Cyt c I V Cyt a Cyt a 3 20 10 0 2
e
– ( from NADH or FADH 2 ) 2 H + + 1 / 2 O 2 H 2 O
Electrons are transferred from NADH or FADH 2 to the electron transport chain Electrons are passed through a number of proteins to O 2 The chain’s function is to break the large free energy drop from food to O 2 into smaller steps that release energy in manageable amounts
http://www.youtube.com/watch?v=xbJ0nbzt 5Kw
Electron transfer in the electron transport chain causes proteins to pump H space + from the mitochondrial matrix to the intermembrane H + then moves back across the membrane, passing through channels in ATP synthase
Animation: http://sp.uconn.edu/~terry/images/anim/ETS.
html
ATP synthase uses the exergonic flow of H + drive phosphorylation of ATP to This is an example of chemiosmosis, the use of energy in a H + gradient to drive cellular work
ATP Synthase
INTERMEMBRANE SPACE H + Stator Rotor Internal rod Cata lytic knob ADP + P i ATP MITOCHONDRIAL MATRIX
Chemiosmosis couples the electron transport chain to ATP synthesis
H + H + H + H + Protein complex of electron carriers Cyt c
V Q
NADH ( carrying electrons from food)
FADH 2 NAD + FAD 2 H + + 1 / 2 O 2 H 2 O ADP + P i ATP synthase ATP 1 Electron transport chain H + 2 Chemiosmosis Oxidative phosphorylation
During cellular respiration, most energy flows in this sequence: glucose NADH electron transport chain proton-motive force ATP About 40% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 38 ATP
+ 6 O
2 6CO 2 + 6H 2 O + 38 ATP
ATP Yield per molecule of glucose at each stage of cellular respiration:
CYTOSOL Electron shuttles span membrane 2 NADH or 2 FADH 2 MITOCHONDRION 2 NADH 2 NADH 6 NADH 2 FADH 2 Glycolysis Glucose 2 Pyruvate 2 Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis + 2 ATP + about 32 or 34 ATP + 2 ATP Maximum per glucose: About 36 or 38 ATP