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BIOCHEMICAL PATHWAYS

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Title: BIOCHEMICAL PATHWAYS


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CHAPTER 6 BIOCHEMICAL PATHWAYS
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BIOCHEMICAL REACTIONS
  • Organisms obtain energy through enzyme-controlled
    biochemical reactions
  • Release energy stored in chemical bonds
  • The ultimate source of all energy is the sun
  • Converted to chemical energy through
    photosynthesis
  • Organisms convert this chemical energy (food)
    into usable energy through cellular respiration
  • Controlled release
  • Large organic molecules are broken down
  • Photosynthetic organisms produce food for their
    own use and for others

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BIOCHEMICAL REACTIONS
  • All organisms carry out cellular respiration
    which may be
  • Aerobic uses oxygen
  • Anaerobic does not use oxygen
  • Organisms can be classified based on how they
    obtain nutrients
  • Autotrophs make their own food (green plants,
    algae)
  • Heterotrophs obtain food from their
    surroundings (all animals, fungi)

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BIOCHEMICAL REACTIONS
  • Some bacterial cells can produce food through
    chemosynthesis (chemical reactions)
  • Occur within the cytoplasm
  • In eukaryotic cells, these reactions are carried
    out in specific organelles
  • Photosynthesis chloroplasts
  • Cellular respiration mitochondria

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BIOCHEMICAL PATHWAYS
  • Can be classified two ways
  • Catabolic reactions - breakdown of organic
    molecules releases energy
  • Anabolic reactions - synthesis of new organic
    molecules requires energy
  • Energy for these reactions is supplied by
    adenosine triphosphate (ATP)
  • Energy is released when ATP is broken down into
    ADP
  • Reformed when a phosphate group is added to ADP
    (phosphorylation reaction)

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Like charging a battery
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The actual process
AMP
ADP
ATP
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AEROBIC CELLULAR RESPIRATION
  • The breakdown of glucose molecules in the
    presence of oxygen
  • Carbon dioxide and water are produced
  • C6H12O6 6 O2 ? 6 CO2 6 H2O energy
    (ATP heat)
  • glucose oxygen ? carbon dioxide water
    energy

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AEROBIC CELLULAR RESPIRATION
  • Begins in the cytoplasm and is completed in the
    mitochondria.
  • Series of enzyme-controlled reactions that are
    divided into three pathways
  • Glycolysis
  • Krebs cycle (citric acid cycle)
  • Electron transport system

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GLYCOLYSIS
  • Glycolysis the breakdown of glucose occurs in
    the cytoplasm
  • Glucose (6-carbon atoms) is broken into two
    3-carbon molecules called pyruvate (pyruvic
    acid).
  • 2 ATP molecules are produced
  • Electrons released from these reactions are
    transferred to the electron transport chain.
  • Will be attached to oxygen atoms

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GLYCOLYSIS
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KREBS CYCLE
  • The pyruvate produced in the cytoplasm moves into
    the mitochondria, releasing
  • Carbon dioxide (remnants of pyruvate)
  • Electrons
  • 2 ATP molecules
  • The electrons are transferred to NADH and FADH2
    (electron carriers), which take them to the
    electron transport system.

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KREBS CYCLE
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ELECTRON TRANSPORT CHAIN
  • When electrons receive additional energy they
    move to a higher energy level.
  • When the electrons fall back to their original
    position they give up that energy.
  • Special molecules (NADH, NADPH, FADH2) capture
    these excited electrons and transfer them to
    other chemical reactions
  • Tied to the formation of ATP
  • Oxidation-reduction reactions
  • Electrons usually come from hydrogen creating H
    (hydrogen nucleus)

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ELECTRON TRANSPORT SYSTEM
  • Electrons are transferred through a series of
    reactions until they are accepted by oxygen
  • Oxygen combines with hydrogen ions to make water.
  • This process generates large amounts of ATP
  • 32 ATP total

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Electron Transport System
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FERMENTATION(Anaerobic Respiration)
  • Two main types of fermentation
  • Alcoholic fermentation
  • Lactic acid fermentation
  • Alcoholic fermentation used by yeast cells in
    the absence of oxygen
  • Pyruvate from glycolysis is converted to ethanol
    and carbon dioxide
  • The yeast cells gain 2 ATP

18
FERMENTATION
  • Lactic acid fermentation pyruvate from
    glycolysis is converted to lactic acid
  • 2 ATP molecules are produced
  • In bacteria, the build up of lactic acid
    interferes with metabolic functions and they die.
  • Humans use lactic acid waste products from these
    types of bacteria to make yogurt, cultured sour
    cream, cheeses, and other fermented dairy
    products.

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ANAEROBIC RESPIRATION
  • In humans, red blood cells produce energy through
    lactic acid fermentation
  • They dont have mitochondria
  • Muscle cells can use aerobic and anaerobic
    respiration.
  • For anaerobic respiration, lactic acid
    accumulates resulting in fatigue, cramping, and
    pain.
  • Must stop the activity or muscles will die
  • When enough oxygen is available, lactic acid is
    converted to pyruvic acid Krebs cycle will
    proceed.

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ANAEROBIC RESPIRATION
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RESPIRATION
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FAT RESPIRATION
  • Fats and proteins can also be used as a source of
    energy.
  • Fats are digested to fatty acids and glycerol
  • Proteins are digested to amino acids
  • Requires several more complex steps.
  • In fats, fatty acids and glycerol are broken down
    through the Krebs cycle in the mitochondria.
  • Can produce more ATP than carbohydrates
  • Serve as long term energy storage
  • Twice as much energy per gram of fat than gram of
    carbohydrate

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PROTEIN RESPIRATION
  • After proteins are broken down to amino acids,
    the amino group is removed.
  • The carbon skeleton enters the respiratory cycle
    as acetyl, pyruvic acid, or other molecules found
    in the Krebs cycle.
  • The removed amino group is converted to ammonia.
  • Excreted as ammonia, uric acid, or urea (very
    toxic must be eliminated)
  • Proteins cannot be stored, so they are converted
    to fat or carbohydrates.

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PHOTOSYNTHESIS
  • Process in which energy from sunlight is
    converted to chemical energy.
  • Anabolic process
  • Used by plants, algae, and some bacteria
  • The green pigment chlorophyll absorbs sunlight.
  • Takes place in chloroplasts, which have 2
    regions
  • Granum stacks of membranous sacs (thylakoids)
    that contain chlorophyll
  • Stroma - the space between the membranes

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PHOTOSYNTHESIS
  • Can be summarized by the following equation
  • Light energy 6 CO2 6 H2O ? C6H12O6 6 O2
  • carbon dioxide water? glucose
    oxygen
  • Opposite of cellular respiration!

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PHOTOSYNTHESIS
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PHOTOSYNTHESIS
  • Three separate events
  • Light-capturing events
  • Light-dependent reactions
  • Light-independent reactions
  • Visible light is a combination of different
    wavelengths of light seen as different colors.
  • Chlorophyll absorbs red and blue light, reflects
    green
  • Pigments called carotenoids (yellow, orange, red)
    also capture light, produce excited electrons
    visible in the fall

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PHOTOSYNTHESIS
  • Light-capturing events
  • Pigments capture light energy which causes some
    electrons to become excited
  • Pigments are arranged into clusters called
    photosystems helps concentrate energy
  • Light-dependent reactions
  • Take place in the thylakoid membranes of the
    grana
  • Excited electrons are passed through an electron
    transport system, producing ATP and NADPH
    (electron carrier)
  • Some electrons split water producing oxygen gas,
    hydrogen ions, and additional electrons

29
PHOTOSYNTHESIS
  • Light-independent reactions
  • Occur in the stroma
  • Energy from excited electrons is used to make
    glucose, lipids, phospholipids, steroids, and
    other organic molecules from carbon dioxide
  • Some of these molecules may also be used to
    produce DNA, RNA, or ATP

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OTHER ASPECTS OF PLANT METABOLISM
  • Plants produce carbohydrates, fats, proteins, and
    nucleic acids from the products of photosynthesis
  • Can produce some toxins and organic molecules
    that are used as medicines
  • May also produce vitamins for themselves and
    other organisms
  • Produce oxygen in photosynthesis which is used
    for cellular respiration by all living things

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AUTOTROPHS AND HETEROTROPHS
  • All living things need oxygen for cellular
    respiration
  • Green plants produce oxygen in photosynthesis,
    but they also use it in cellular respiration
  • Produce more than enough and release the rest
  • Animals are dependent on plants not only for
    oxygen, but also for essential nutrients to
    maintain metabolism and construct tissues
  • Animals supply materials needed by plants and
    vice versa.
  • Essential to life on Earth

34
Need to Know
  • What is cellular respiration?
  • What are the 3 steps?
  • How much ATP is formed at each step?
  • Where in the cell do these occur?
  • What is ATP?
  • What is photosynthesis?
  • What are the 3 steps?
  • Where do these processes occur in a cell?

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CHAPTER 6 BIOCHEMICAL PATHWAYS
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AMP
ADP
ATP
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PHOTOSYNTHESIS
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CHAPTER 6 BIOCHEMICAL PATHWAYS
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AMP
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ATP
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PHOTOSYNTHESIS
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