Glycolysis & Respiration

When you exercise When you exercise Feeling The “Burn” –Muscles need energy in order to perform work –Your cells use oxygen to release energy from the sugar glucose

Aerobic metabolism Aerobic metabolism –When enough oxygen reaches cells to support energy needs Anaerobic metabolism Anaerobic metabolism –When the demand for oxygen outstrips the body’s ability to deliver it Types of Metabolism

Without enough oxygen, muscle cells break down glucose to produce lactic acid Without enough oxygen, muscle cells break down glucose to produce lactic acid –the “burn” associated with heavy exercise If too much lactic acid builds up, muscles give out If too much lactic acid builds up, muscles give out Anaerobic Metabolism

Physical Conditioning Allows body to adapt to increased activity Allows body to adapt to increased activity Long-distance runners wait until final sprint to exceed aerobic capacity Long-distance runners wait until final sprint to exceed aerobic capacity

Energy Flow & Chemical Cycling Energy stored in food can be traced back to the sun Energy stored in food can be traced back to the sun Animals depend on plants to convert solar energy to chemical energy in the form of sugars and other organic molecules Animals depend on plants to convert solar energy to chemical energy in the form of sugars and other organic molecules

Photosynthesis Photosynthesis Producers & Consumers –Light energy from the sun powers a chemical process that makes organic molecules

Autotrophs - “Self-feeders” Plants and other organisms that make all their own organic matter from inorganic nutrients Plants and other organisms that make all their own organic matter from inorganic nutrients Heterotrophs - “Other-feeders” Humans and other animals that cannot make organic molecules from inorganic ones Humans and other animals that cannot make organic molecules from inorganic ones

Role in Ecosystems Producers - Why autotrophs? Producers - Why autotrophs? Consumers - Why heterotrophs Consumers - Why heterotrophs

Chloroplasts rearrange the atoms of carbon dioxide and water to produce sugars (glucose) and other organic molecules Chloroplasts rearrange the atoms of carbon dioxide and water to produce sugars (glucose) and other organic molecules Oxygen gas is a by-product of photosynthesis Oxygen gas is a by-product of photosynthesis Chemical Cycling CO 2 + H 2 O + energy--->C 6 H 12 O 6 + O 2 CO 2 + H 2 O + energy ---> C 6 H 12 O 6 + O 2

Connections

C 6 H 12 O 6 + O 2 --->CO 2 + H 2 O + energy Exergenic & Catabolic Respiration Process

Respiration

Cellular respiration and breathing are closely related Cellular respiration and breathing are closely related –Cellular respiration requires a cell to exchange gases with its surroundings –Breathing exchanges these gases between the blood and outside air Cellular Respiration & Breathing

Figure 6.4 Breathing Lungs Muscle cells Cellular respiration

A common fuel molecule for cellular respiration is glucose A common fuel molecule for cellular respiration is glucose –This is the overall equation for what happens to glucose during cellular respiration The Overall Equation for Cellular Respiration GlucoseOxygenCarbon dioxide WaterEnergy

During cellular respiration, hydrogen and its bonding electrons change partners During cellular respiration, hydrogen and its bonding electrons change partners –Hydrogen and its electrons go from sugar to oxygen, forming water The Role of Oxygen in Cellular Respiration

Chemical reactions that transfer electrons from one substance to another are called oxidation- reduction reactions (REDOX) Chemical reactions that transfer electrons from one substance to another are called oxidation- reduction reactions (REDOX) Redox Reactions

Loss of electrons reaction = oxidation Loss of electrons reaction = oxidation Acceptance of electrons = reduction Acceptance of electrons = reduction Redox Reactions [Oxygen gains electrons (and hydrogens)] Oxidation [Glucose loses electrons (and hydrogens)] GlucoseOxygenCarbon dioxide Water Reduction

When electrons move from glucose to oxygen, it is as though they were falling When electrons move from glucose to oxygen, it is as though they were falling This “fall” of electrons releases energy during cellular respiration This “fall” of electrons releases energy during cellular respiration Release of heat energy Why does electron transfer to oxygen release energy?

The path that electrons take on their way down from glucose to oxygen involves many stops The path that electrons take on their way down from glucose to oxygen involves many stops NADH & Electron Transport Chains 1/21/2 (from food via NADH) 2 H  2 e  Energy for synthesis of Electron transport chain 2 e  2 H  1/21/2

first stop = electron acceptor NAD + Transfer of electrons from organic fuel to NAD + reduces it to NADH Transfer of electrons from organic fuel to NAD + reduces it to NADH Rest of the path = electron transport chain Rest of the path = electron transport chain –This chain involves a series of redox reactions –These lead ultimately to the production of large amounts of ATP

3 Stages: 3 Stages: – Oxidation of Pyruvate – Kreb’s Cycle – Electron Transport Chain Cellular Respiration A example of a metabolic pathway: a series of chemical reactions in cells A example of a metabolic pathway: a series of chemical reactions in cells

Mitochondria Outer membrane =semi-permeable Outer membrane =semi-permeable Inner membrane = folded CRISTAE Inner membrane = folded CRISTAE –HIGHLY SELECTIVE

Road Map for Cellular Respiration Cytosol Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Glycolysis Glucose 2 Pyruvic acid Krebs Cycle Electron Transport

Stage 1: Glycolysis Glucose is split into two molecules of pyruvic acid Glucose is split into two molecules of pyruvic acid Glucose 2 Pyruvic acid

Aerobic Glycolysis Occurs in the cytoplasm, in the presence of oxygen Occurs in the cytoplasm, in the presence of oxygen Splits ONE glucose into TWO pyruvate molecules Splits ONE glucose into TWO pyruvate molecules Reaction is first ENDERGONIC, then EXERGENIC Reaction is first ENDERGONIC, then EXERGENIC

Glycolysis makes some ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP Glycolysis makes some ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP Enzyme

Aerobic Glycolysis 2 ATP molecules are USED to "kick-off" the reaction (endergonic) 2 ATP molecules are USED to "kick-off" the reaction (endergonic) 4 ATP molecules are generated during exergenic steps 4 ATP molecules are generated during exergenic steps 2 NADH molecules are also generated 2 NADH molecules are also generated

Aerobic Glycolysis NAD + gains a hydrogen and an electron and becomes NADH NAD + gains a hydrogen and an electron and becomes NADH NADH = an electron ‑ carrier NADH = an electron ‑ carrier Energy from 1 NADH is enough to phosphorolate 3 ATP Energy from 1 NADH is enough to phosphorolate 3 ATP

Aerobic Glycolysis Energy is generated by a series of reactions ultimately used to form ATP from ADP Energy is generated by a series of reactions ultimately used to form ATP from ADP Net gain of ATP for aerobic glycolysis = Net gain of ATP for aerobic glycolysis =

Glucose 2 Pyruvic acid

Stage 2: The Krebs Cycle Completes breakdown Input Acetic acid ADP 3 NAD  FAD Krebs Cycle Output 2 CO

In the Krebs cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl-CoA In the Krebs cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl-CoA CoA Pyruvic acid Acetic acid Coenzyme A Acetyl-CoA (acetyl-coenzyme A) CO 2

Oxidation of Pyruvate Pyruvate pulled into mitochondria Pyruvate pulled into mitochondria – May take the energy of 2 ATP Broken down into: Broken down into: – 2 CARBON DIOXIDE – 2 molecules of NADH – 2 molecules of Acetyl CoA

Oxidation of Pyruvate

Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO 2 Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO 2 –The cycle uses some of this energy to make ATP –The cycle also forms NADH and FADH 2

Kreb’s Cycle 4 carbon beginning product is regenerated at the end of the cycle 4 carbon beginning product is regenerated at the end of the cycle

Kreb’s Cycle Products are broken down, generating: Products are broken down, generating: – 4 molecules of CARBON DIOXIDE, – 6 molecules of NADH, – 2 molecules of FADH 2 – 2 molecules of ATP for a total of

Input Acetic acid ADP 3 NAD  FAD Krebs Cycle Output 2 CO

Stage 3: Electron Transport Protein complex Electron carrier Inner mitochondrial membrane Electron flow Electron transport chain ATP synthase ETC releases the energy cells need to make ATP ETC releases the energy cells need to make ATP

Electron Transport Chain 2) Involves a drop in energy levels from one carrier to the next 3) Depends upon a proton gradient in the cristae to work (CHEMIOSMOSIS)

When the hydrogen ions flow back through the membrane, they release energy When the hydrogen ions flow back through the membrane, they release energy –The ions flow through ATP synthase –ATP synthase takes the energy from this flow and synthesizes ATP

Electron Transport Chain 4) Ultimately converts ADP to ATP 5) Forms molecules of WATER at the end

Versatility of Cellular Respiration Cellular respiration can “burn” other kinds of molecules besides glucose Cellular respiration can “burn” other kinds of molecules besides glucose – Diverse types of carbohydrates – Fats – Proteins

Food Polysaccharides FatsProteins SugarsGlycerolFatty acidsAmino acids Amino groups Glycolysis Acetyl- CoA Krebs Cycle Electron Transport

Adding Up the ATP from Cellular Respiration Cytosol Mitochondrion Glycolysis Glucose 2 Pyruvic acid 2 Acetyl- CoA Krebs Cycle Electron Transport by direct synthesis by direct synthesis by ATP synthase Maximum per glucose:

Summary Generates 95% of the ATP made heterotrophic cells Generates 95% of the ATP made heterotrophic cells

Anaerobic Glycolysis Occurs in the cytoplasm, in the absence of oxygen Occurs in the cytoplasm, in the absence of oxygen Follows the same beginning steps as aerobic glycolysis Follows the same beginning steps as aerobic glycolysis Instead of entering mitochondria, pyruvate diverts to other pathways, yielding small amounts of energy. Instead of entering mitochondria, pyruvate diverts to other pathways, yielding small amounts of energy.

Anerobic Glycolysis Some of your cells can actually work for short periods without oxygen Some of your cells can actually work for short periods without oxygen –For example, muscle cells can produce ATP under anaerobic conditions Fermentation Fermentation –The anaerobic harvest of food energy

Glycolysis is the metabolic pathway that provides ATP during fermentation Glycolysis is the metabolic pathway that provides ATP during fermentation –Pyruvic acid is reduced by NADH, producing NAD+, which keeps glycolysis going –In human muscle cells, lactic acid is a by-product

2 ADP+ 2 Glycolysis Glucose 2 NAD  2 Pyruvic acid + 2 H  2 NAD  2 Lactic acid (a) Lactic acid fermentation

Lactic Acid Pathway Excess produces pain, fatigue Excess produces pain, fatigue When O2 is available again, resynthesized in liver to pyruvate When O2 is available again, resynthesized in liver to pyruvate also yields only 2 ATP also yields only 2 ATP –CRITICAL to keep the body going in time of need

Human muscle cells can make ATP with and without oxygen Human muscle cells can make ATP with and without oxygen –enough ATP to support activities such as quick sprinting for 5 secs –A secondary supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds –To keep running, your muscles must generate ATP by the anaerobic process of fermentation Human Muscle Cells

Yeast cells carry out a slightly different type of fermentation pathway Yeast cells carry out a slightly different type of fermentation pathway Produces CO 2 & ethyl alcohol Produces CO 2 & ethyl alcoholMicroorganisms

Glucose 2 ADP+ 2 2 ATP Glycolysis 2 NAD  2 Pyruvic acid 2 CO 2 released + 2 H  2 NAD  2 Ethyl alcohol Alcoholic Fermentation Yeast mixed with juices of sugar- containing plants, stored under anaerobic conditions Yeast mixed with juices of sugar- containing plants, stored under anaerobic conditions

Fermentation ENDERGENIC reaction, yielding a net gain of 2 ATP per molecule of Glucose ENDERGENIC reaction, yielding a net gain of 2 ATP per molecule of Glucose Once sugar content is used up, fermentation stops, alcohol level is fixed. Once sugar content is used up, fermentation stops, alcohol level is fixed. Other uses of yeast?

What would life be like without oxygen? Life On An Anaerobic Earth

Glycolysis is a metabolic heirloom from the earliest cells that continues to function today in the harvest of food energy Glycolysis is a metabolic heirloom from the earliest cells that continues to function today in the harvest of food energy

Evolutionary History Anerobic pathways probably evolved FIRST: needs no oxygen Anerobic pathways probably evolved FIRST: needs no oxygen Prokaryotes + protists were small, needed little energy) Prokaryotes + protists were small, needed little energy)

Adding Up the ATP from Cellular Respiration Cytosol Mitochondrion Glycolysis Glucose 2 Pyruvic acid 2 Acetyl- CoA Krebs Cycle Electron Transport by direct synthesis by direct synthesis by ATP synthase Maximum per glucose:

Summary Of Key Concepts Chemical Cycling Between Photosynthesis and Cellular Respiration Chemical Cycling Between Photosynthesis and Cellular Respiration Sunlight Heat Photosynthesis Cellular respiration

Overall Equation for Cellular Respiration Oxidation: Glucose loses electrons (and hydrogens) GlucoseCarbon dioxide Electrons (and hydrogens) Energy Oxygen Reduction: Oxygen gains electrons (and hydrogens)

Designedby Anne F. Maben These images are for viewing only and may not be published in any form