Cellular Respiration

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Cellular Respiration

• How do living things release energy???
• Quick Review
• Most energy used thru conversion of ATP molecules
  into ADP molecules
• Thus cells must continually convert ADP molecules
  back into ATP molecules
• This process is known as.
• CELLULAR RESPIRATION

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Lesson Objectives

• Name the three stages of cellular respiration.
• Give an overview of glycolysis.
• Explain why glycolysis probably evolved before
  the other stages of aerobic respiration.
• Describe the structure of the mitochondrion and
  its role in aerobic respiration.
• List the steps of the Krebs cycle, and identify
  its products.
• Explain how electron transport results in many
  molecules of ATP.
• Describe how chemiosmotic gradients in
  mitochondria store energy to produce ATP.
• State the possible number of ATP molecules that
  can result from aerobic respiration.
• Define fermentation.
• Describe lactic acid fermentation and alcoholic
  fermentation.
• Compare the advantages of aerobic and anaerobic
  respiration.
• Compare cellular respiration to photosynthesis

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Breathing versus Cellular Respiration

• Breathing physical process that allows animals
  and humans to come into contact with gases in the
  air
• Cellular respiration chemical process that
  releases energy from organic compounds (food),
  gradually converting it into energy that is
  stored in ATP molecules

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Correlation between a campfire and Cellular
Respiration

• Analyzing a campfire can clarify your
  understanding of cellular respiration.
• A campfire breaks chemical bonds in wood,
  releasing stored energy as light and heat
• Cellular respiration breaks chemical bonds in
  glucose, releasing stored energy and transferring
  some to 38 ATP some energy is lost
• as heat.

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Chemical Pathways

• Food is the raw material that provides the
• energy for your body to function
• Cells use food to synthesize new molecules
• to carry out their life processes

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• Cells do not BURN glucose, they slowly release
  energy from it and other food compounds through
  several pathways (processes)
• 1st pathway ? glycolysis releases only a small
  amount of energy (2 net ATP)
• If oxygen present, it will lead to two other
  pathways that release a lot of energy Krebs
  cycle Electron Transport Chain
• If oxygen absent glycolysis is followed by a
  different pathway Alcoholic Fermentation or
  Lactic Acid Fermentation

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Overview of Cellular Respiration

• In presence of oxygen (aerobic) glycolysis is
  followed by ______________
• ______________

Krebs Cycle
Electron Transport Chain
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• All three combined make up Cellular Respiration
  Glycolysis Krebs Cycle Electron Transport
  Chain
• Process that releases energy by breaking down
  food molecules in the presence of oxygen

Equation for cellular respiration 6O2
C6H12O6 -------? 6CO2 6H2O energy
(ATP) oxygen glucose -----? carbon
dioxide water energy
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2
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Each of these 3 stages captures some of the
chemical energy available in food molecules and
uses it to produce ATP
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• What is the process of
• glycolysis????

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Glycolysis

• Process takes place in the cytosol of the
  cytoplasm outside of mitochondria coverts
  glucose with the help of 2 ATP molecules and
  eventually releases 4 ATP molecules for a net
  gain of 2 ATP molecules.

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ATP NADH production in Glycolysis
2 ATP used up become 2 ADP
2 NADH 2 H produced
4 ATP produced Net gain 2 ATP
Step 1 breaks 1 molecule of glucose in half,
producing 2 molecules of pyruvic acid (a
3-carbon compound) Step 2 2 NAD electron
carrier accepts 4 high-energy electrons
transfers them to 2 NADH molecules and 2 H thus
passing the energy stored in the glucose Step
3 4 ADP added producing 4 ATP Step 4 2
remaining pyruvic acids enter Krebs Cycle in
presence of oxygen IF no oxygen another pathway
is followed
NAD (nicotinamide adenine dinucleotide)
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• Glycolysis is a fast process
• Cells produce thousands of ATP molecules in a few
  milliseconds
• Glycolysis alone DOES NOT require oxygen
• It can supply chemical energy to cells when
  oxygen is NOT available
• However if a cell generates large amounts of ATP
  from glycolysis it can run into problems
• a. the cells available NAD molecules
  become filled
• up with electrons
• b. glycolysis shuts down, cannot proceed
  without
• available NAD molecules
• c. ATP production stops

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Anaerobic to Aerobic Respiration

• Glycolysis evolved before the other stages of
  cellular respiration other stages need oxygen
• No oxygen in Earths atmosphere when life first
  evolved about 3.5 to 4 b.y.a.
• Without oxygen ? anaerobic respiration
• 2 or 3 billion years ago, oxygen was gradually
  added to the atmosphere by early photosynthetic
  bacteria period the oxygen catastrophe
  ?aerobic organisms

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Lets look at the pathway that follows gycolysis
with the presence of oxygen.. aerobic
respiration
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BUT FIRSTMitochondrion Structure

• Mitochondrion has two separate membranes inner
  and outer membrane.
• Three compartments intermembrane space, cristae
  space, and matrix

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AEROBIC RESPIRATIONThe Krebs Cycle and Electron
Transport

• End of glycolysis? 90 of chemical energy from
  glucose still unused, locked in high-energy
  electrons of pyruvic acid
• Extracted by worlds most powerful electron
  receptor?
• Krebs and Electron Transport require oxygen thus
  they are aerobic processes

OXYGEN
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The Krebs Cycle

• 1. 2nd stage of cellular respiration
• 2. Named after Hans Krebs, British
• biochemist in 1937
• 3. Here pyruvic acid is broken down
• into carbon dioxide in a series
  of
• energy-extracting reactions
• 4. Citric acid is the 1st compound
• formed in this series of
  reactions,
• so Krebs is sometimes called the
  
• Citric or Citric Acid Cycle.

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Pyruvic acid enters from glycolysis One carbon
removed CO2 formed NAD again changed to
NADH CoA joins remaining 2 carbons
Acetyl-CoA Acetyl-CoA added to 4 carbon
Compound Citric acid (6-C) Citric acid broken
down to 5-carbon then 4 carbon more CO2
released Along the way more NADH and FADH2
formed One molecule of ATP also made 2 turns
2 pyruvic acid (from glycolysis) yield 10 NADH
(2 from glycolysis) 2 FADH2 4 ATP (2 from
glycolysis) Cycle starts anew
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Uses for the products of the Krebs Cycle

• Carbon dioxide is exhaled (waste product)
• ATP can be used for cellular activities
• High-energy electrons (stored in NADH FADH2)
  can be used to make huge amounts of ATP in the
  presence of oxygen

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• Electrons from Krebs cycle are passed to electron
  transport chain by NADH FADH2
• At end of the chain an enzyme combines electrons
  from the electron chain with H ions and oxygen
  to form water
• Each time 2 high-energy electrons transport down
  the electron chain, their energy is used to
  transport H ions across the membrane
• H ions build up in intermembrane space it is now
  positively charged, other side of membrane
  negatively charged (DISPLAY)
• Electrochemical gradient (chemiosmotic gradient)
  created for ATP synthase to work (OFF)
• ATP synthase converts ADP into ATP (DISPLAY)

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The Total ATP production of Aerobic CR

• How much chemical energy comes from one molecule
  of glucose??
• Absence of oxygen
• Only 2 ATP molecules from glycolysis
• Presence of oxygen
• 2 net ATP molecules from glycolysis
• 36 more ATP molecules from Krebs Cycle and
  electron transport
• These 38 ATP molecules represent 38 of the total
  energy of glucose, remaining 62 is released as
  heat, thus your body feels warmer after vigorous
  exercise and does not freeze in winter.

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Lets look at the pathway that follows gycolysis
without the presence of oxygen.. anaerobic
respiration
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Anaerobic Respiration Fermentation

• This occurs after glycolysis when oxygen absent,
  thus anaerobic process
• Fermentation releases energy from food molecules
  in absence of oxygen
• In this process cells convert NADH to NAD by
  passing high-energy electrons back to pyruvic
  acid
• Now glycolysis has NAD and can continue
  producing ATP
• There are 2 types of fermentation
• Alcoholic fermentation
• Lactic acid fermentation

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• Anaerobic and aerobic respiration share the
  glycolysis pathway. If oxygen is absent,
  fermentation may take place, producing lactic
  acid or ethyl alcohol and carbon dioxide.
  Products of fermentation still contain chemical
  energy, and are used widely to make foods and
  fuels.

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Alcoholic Fermentation

• Yeast and a few other microorganisms use
  alcoholic fermentation, forming ethyl alcohol and
  carbon dioxide as wastes
• Equation for alcoholic fermentation
• pyruvic acid NADH ? ethyl alcohol CO2
  NAD

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Lactic Acid Fermentation

• Many cells convert accumulated pyruvic acid from
  gycolysis to lactic acid lactic acid
  fermentation regenerates NAD so glycolysis can
  continue
• Equation for lactic acid fermentation
• pyruvic acid NADH ? lactic acid NAD
• 4. When your body cannot supply enough oxygen
  to muscle tissues during exercise, this is
  produced
• 5. Without oxygen the body is unable to
  produce all the ATP it requires, so lactic acid
  fermentation takes over

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• Running, swimming, or riding a bike as fast as
  you can large muscles in your legs and arms
  that quickly run out of oxygenmuscles begin to
  rapidly produce ATP by lactic acid fermentation.
• The buildup of lactic acid fermentation causes a
  painful burning sensation making your
• muscles feel sore
• How do you stop it?????
• NEED TO INTAKE OXYGEN

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Energy and Exercise

• Initially body uses ATP which is already
  available in muscles
• Then new ATP made by Lactic Acid Fermentation and
  Cellular Respiration
• Eventually energy supply runs out
• A. Quick Energy
• 1. ATP in muscles only lasts a few
  seconds
• 2. ATP from lactic acid fermentation
  lasts
• about 90 seconds
• - this then creates a by-product
  (lactic acid)
• which the body must get rid of, the
  body
• releases it by panting heavily
  (intake of oxygen)

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• B. Long-Term Energy
• - exercise lasting longer than 90 seconds
  utilizes
• cellular respiration to generate a
  continuous supply
• of ATP
• - cellular respiration releases energy slower
  than
• fermentation, thus athletes can pace
  themselves
• - body stores energy in muscles and tissues
  in the
• form of glycogen (carbohydrate)
• -- stores of glycogen usually lasts for
  15-20 minutes
• of activity, then the body starts to
  break down
• other molecules like fat for energy
• HOW LONG DO YOU NEED TO ACTIVE BEFORE YOU START
  TO BURN FAT?????

17-22 minutes
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Aerobic vs. Anaerobic Respiration A Comparison

• Advantages of Aerobic Respiration
• Major advantage ? more energy released
• Enough energy to produce up to 38 ATP
• Advantages of Anaerobic Respiration
• Lets organisms live in places where there is
  little or no oxygen
• Quickly produces ATP

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Relationship between Cellular Respiration and
Photosynthesis
Equation for Cellular Respiration 6O2
C6H12O6 ? 6CO2 6H2O energy
(ATP) Equation for Photosynthesis 6CO2
6H2O energy (sunlight) ? 6O2 C6H12O6
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LETS REVIEW

• How many stages does cellular respiration have?
  ____________
• What are the stages of cellular respiration?
  __________________________________________________
  ______________________
• Where does glycolysis take place?
• ____________________________________
• Where does the Krebs cycle take place?
  ___________________________________

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GLYCOLYSIS, KREBS CYCLE, AND ELECTRON TRANSPORT
CHAIN
CYTOSOL OF THE CYTOPLASM OF MITOCHONDRIA
IN THE MATRIX OF MITOCHONDRIA
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• Where is the Electron Transport Chain located?
  __________________________________
• What do high-energy electrons help the cells
  build? ___________________________________________
  _________________________
• What are the stage(s) of aerobic respiration?
  __________________________________________________
  __________________

INNER MEMBRANE OF MITOCHONDRIA
MOLECULES LIKE GLUCOSE ATP
GLYCOLYSIS, KREBS CYCLE, AND ELECTRON TRANSPORT
CHAIN
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• What are the stage(s) of anaerobic respiration?
  __________________________________________________
  __________________
• What are the two types of fermentation?
  __________________________________________________
  __________________
• Which fermentation process do humans use?
  __________________________________

GLYCOLYSIS, FOLLOWED BY FERMENTATION
ALCOHOLIC FERMENTATION AND LACTIC ACID
FERMENTATION
LACTIC ACID FERMENTATION
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Lesson Summary

• In the two to three billion years since
  photosynthesis added oxygen to
• earths atmosphere, life has become mostly
  aerobic. Some organisms
• and types of cells retain the older, anaerobic
  pathways for making ATP
• these pathways comprise anaerobic respiration or
  fermentation.
• Muscle cells can continue to produce ATP when O2
  runs low using lactic acid fermentation, but
  muscle fatigue and pain may result.
• Both alcoholic and lactic acid fermentation
  pathways change pyruvate in order to continue
  producing ATP by glycolysis.
• Aerobic respiration is far more energy-efficient
  than anaerobic respiration.
• Aerobic processes produce up to 38 ATP per
  glucose. Anaerobic processes yield only 2 ATP per
  glucose.