Cellular Respiration - Biology Courses ?· sugar is called cellular respiration – Cellular respiration…

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  • 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?

  • Sprinters muscles have more FAST FIBERS

    - Fast fibers make ATP without oxygenanaerobically- 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 seethe 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

    CO2ATP

    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

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