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Cellular Respiration:

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Title: Cellular Respiration:


1
Chapter 9
  • Cellular Respiration
  • Harvesting Chemical Energy

2
Respiration Facts
  • All the energy in all the food you eat can be
    traced back to sunlight
  • If you exercise too hard, your muscles shut down
    from a lack of oxygen

3
FEELING THE BURN
  • When you exercise
  • Muscles need energy in order to perform work
  • Your cells use oxygen to release energy from the
    sugar glucose
  • Both aerobic and anaerobic burning of glucose can
    take place in your cells

4
Aerobic Anaerobic Metabolism
  • Aerobic metabolism - When enough oxygen reaches
    cells to support energy needs
  • - Maximum energy production
  • Anaerobic metabolism
  • When the demand for oxygen outstrips the bodys
    ability to deliver it
  • Low energy production

5
Anaerobic Metabolism
  • Without enough oxygen, muscle cells break down
    glucose to produce lactic acid
  • Lactic acid is associated with the burn
    associated with heavy exercise
  • If too much lactic acid builds up, your muscles
    give out

6
Physical Conditioning
  • Allows your body to adapt to increased activity
  • The body can increase its ability to deliver
    oxygen to muscles
  • Long-distance runners wait until the final sprint
    to exceed their aerobic capacity

7
Why Photosynthesis?
  • Only producers are capable of Photosynthesis
  • Light energy from the sun powers this chemical
    process that makes organic molecules (sugars)
  • This process occurs in the mesophyll cells of
    leaves of producers (plants algae)

8
ENERGY FLOW IN THE BIOSPHERE
  • Energy stored in food can be traced back to the
    sun
  • Fuel molecules in food store solar energy in
    chemical bonds
  • Animals depend on plants to convert solar energy
    to chemical energy
  • This chemical energy is in the form of sugars and
    other organic molecules

9
Autotrophs Heterotrophs
  • Autotrophs - Plants and other organisms that
    make all their own organic matter from inorganic
    nutrients
  • Heterotrophs - Humans and other animals that
    cannot make organic molecules from inorganic ones

10
The Cycle of Energy
  • Producers - Biologists refer to plants and other
    autotrophs as the producers in an ecosystem
  • Consumers - Heterotrophs are consumers, because
    they eat plants or other animals

11
Chemical Cycling
  • The ingredients for photosynthesis are carbon
    dioxide and water
  • CO2 is obtained from the air by a plants leaves
  • H2O is obtained from the damp soil by a plants
    roots
  • Chloroplasts rearrange the atoms of these
    ingredients to produce sugars (glucose) and other
    organic molecules
  • Oxygen gas is a by-product of photosynthesis

12
Chemical Cycling
  • Both plants and animals perform cellular
    respiration
  • Cellular respiration is a chemical process that
    harvests energy from organic molecules and occurs
    in the mitochondria
  • The waste products of cellular respiration, CO2
    and H2O, are used in photosynthesis

13
Sunlight supplies the energy!
Sunlight energy
Bonds of Glucose, made in chloroplasts, contain
the stored energy
Ecosystem
Photosynthesis (in chloroplasts)
Raw materials for cellular respiration
Carbon dioxide
Raw materials for photosynthesis
Glucose
Oxygen
Water
Glucose broken down to release energy for
cellular work
Cellular respiration (in mitochondria)
Cellular energy
Heat energy
14
AEROBIC HARVEST OF FOOD ENERGY
  • Cellular respiration is the main way that
    chemical energy is harvested from food and
    converted to ATP for cellular work
  • Cellular respiration is an aerobic process
    requiring oxygen

15
The Versatility of Cellular Respiration
  • Cellular respiration can burn other kinds of
    molecules besides glucose
  • Diverse types of carbohydrates
  • Fats
  • Proteins

15
16
The Overall Equation for Cellular Respiration
  • A common fuel molecule for cellular respiration
    is glucose
  • This is the overall equation for what happens to
    glucose during cellular respiration

Glucose
Oxygen
Carbon dioxide
Water
Energy
17
But Remember
  • Cellular Respiration is a metabolic pathway, not
    a single reaction
  • Many chemical reactions, both aerobic and
    anaerobic, are involved in the process of
    cellular respiration
  • Lots of enzymes are required for the process to
    occur

18
The Relationship Between Cellular Respiration and
Breathing
  • 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

19
Breathing
Lungs
Muscle cells
Cellular Respiration
20
The Role of Oxygen in Cellular Respiration
  • During cellular respiration, hydrogen and its
    bonding electrons change partners
  • Hydrogen and its electrons go from sugar to
    oxygen, forming water

21
Redox Reactions
  • Chemical reactions that transfer electrons from
    one substance to another are called
    oxidation-reduction reactions
  • REDOX short for oxidation-reduction reactions

22
Redox Reactions
  • The loss of electrons during a redox reaction is
    called oxidation
  • The acceptance of electrons during a redox
    reaction is called reduction
  • Reducing agent e- donor
  • Oxidizing agent e- acceptor

23
REDOX in Cellular Respiration
Glucose loses electrons (and hydrogens)
Oxidation
Oxygen
Glucose
Carbon dioxide
Water
Reduction
Oxygen gains electrons (and hydrogens)
24
Comparison
Respiration Photosynthesis
Occurs in all organisms Occurs in only chlorophyll containing organisms
Breaks down glucose Stores light energy as chemical energy in the bonds of glucose
Releases carbon dioxide, water, ATP Produces glucose and oxygen
Exergonic Reaction Endergonic reaction
25
The Metabolic Pathway of Cellular Respiration
  • Cellular respiration is an example of a metabolic
    pathway
  • A series of chemical reactions in cells either
    building or breaking down molecules

26
The Metabolic Pathway of Cellular Respiration
  • All of the reactions involved in cellular
    respiration can be grouped into three main stages
  • Glycolysis occurs in cytoplasm
  • The Krebs cycle occurs in matrix of
    mitochondria
  • Electron transport occurs across the
    mitochondrial membrane

27
A Road Map for Cellular Respiration
Mitochondrion
Cytosol
High-energy electrons carried mainly by NADH
High-energy electrons carried by NADH
Glycolysis
Krebs Cycle
2 Pyruvic acid
Electron Transport
Glucose
28
Glycolysis
  • Stage One

29
Stage 1 Glycolysis
  • Glycolysis takes place in the cytoplasm
  • Oxygen NOT required
  • Process breaks a six-carbon glucose into two,
    three-carbon molecules
  • A molecule of glucose is split into two molecules
    of pyruvic acid
  • These molecules then donate high energy electrons
    to NAD, forming NADH

30
Glycolysis
METABOLIC PATHWAY
2 Pyruvic acid
Glucose
31
Glycolysis
CoA
Acetic acid
Pyruvic acid
Acetyl-CoA (acetyl-coenzyme A)
CO2
Coenzyme A
31
32
Glycolysis Summary
  • The Krebs cycle extracts the energy of sugar by
    breaking the acetic acid molecules all the way
    down to CO2
  • The cycle uses some of this energy to make ATP
  • The cycle also forms NADH and FADH2 ( 2 energy
    carrier molecules)

32
33
Krebs Cycle
  • Stage Two

34
Stage 2 The Krebs Cycle
  • The Krebs cycle completes the breakdown of sugar
  • It occurs inside the mitochondria
  • In the Krebs cycle, pyruvic acid from glycolysis
    is first prepped into a usable form by
    combining it with enzyme Co-A to make Acetyl-CoA

35
ACETYL Co-A
Input
Output
2
Acetic acid
1
2 CO2
3
ADP
Krebs Cycle
3 NAD?
4
FAD
5
6
36
Electron Transport
  • Stage 3

37
Stage 3 Electron Transport
  • Electron transport releases the energy your cells
    need to make the most of their ATP
  • The molecules of electron transport chains are
    built into the inner membranes of mitochondria

38
Stage 3 Electron Transport
  • The chain functions as a chemical machine that
    uses energy released by the fall of electrons
    to pump hydrogen ions across the inner
    mitochondrial membrane
  • These ions store potential energy

39
Electron transport chain
  • Cytochromes carry electron carrier molecules
    (NADH FADH2) down to oxygen
  • Chemiosmosis energy
    coupling mechanism
  • ATP synthase produces ATP by using the H
    gradient (proton-motive force) pumped into the
    inner membrane space from the electron transport
    chain this enzyme harnesses the flow of H back
    into the matrix to phosphorylate ADP to ATP
    (oxidative phosphorylation)

40
Protein complex
Electron carrier
Inner mitochondrial membrane
Electron flow
ATP synthase
Electron transport chain
41
Food
Polysaccharides
Fats
Proteins
Sugars
Glycerol
Fatty acids
Amino acids
Amino groups
Acetyl- CoA
Krebs Cycle
Glycolysis
Electron Transport
42
Adding Up the ATP
Cytosol
Mitochondrion
Glycolysis
2 Acetyl- CoA
Krebs Cycle
2 Pyruvic acid
Electron Transport
Glucose
Maximum per glucose
by ATP synthase
by direct synthesis
by direct synthesis
Figure 6.14
43
FERMENTATION ANAEROBIC HARVEST OF FOOD ENERGY
  • Some of your cells can actually work for short
    periods without oxygen (anaerobic respiration)
  • For example, muscle cells can produce ATP under
    anaerobic conditions
  • Called Fermentation
  • Involves The anaerobic harvest of food energy

44
Fermentation in Human Muscle Cells
  • Human muscle cells can make ATP with and without
    oxygen
  • They have enough ATP to support activities such
    as quick sprinting for about 5 seconds
  • 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

45
  • 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

46
2 ADP 2
Glycolysis
2 NAD?
2 NAD?
Glucose
2 Pyruvic acid
2 H?
2 Lactic acid
Lactic acid fermentation
47
Fermentation in Microorganisms
  • Various types of microorganisms perform
    fermentation
  • Yeast cells carry out a slightly different type
    of fermentation pathway
  • This pathway produces CO2 and ethyl alcohol

48
2 ADP 2
2 CO2 released
2 ATP
Glycolysis
2 NAD?
2 NAD?
2 Ethyl alcohol
Glucose
2 Pyruvic acid
2 H?
Alcoholic fermentation
49
  • The food industry uses yeast to produce various
    food products

50
Related metabolic processes
  • Fermentation alcohol pyruvate to ethanol
    lactic acid pyruvate to lactate
  • Facultative anaerobes (yeast/bacteria)
  • Beta-oxidation lipid catabolism

51
Review Cellular Respiration
  • Glycolysis
  • 2 ATP (substrate-level phosphorylation)
  • Krebs Cycle
  • 2 ATP (substrate-level phosphorylation)
  • Electron transport oxidative phosphorylation
  • 2 NADH (glycolysis) 6ATP
  • 2 NADH (acetyl CoA) 6ATP
  • 6 NADH (Krebs) 18 ATP
  • 2 FADH2 (Krebs) 4 ATP
  • 38 TOTAL ATP/glucose


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