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Cell Energy

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					Cell Energy
Accessing energy stored by
photosynthesis
Photosynthesis
 Plants harvest energy from photons of
  light
 Use it to excite electrons
 Use excited electrons to form the bonds in
  a sugar molecule

   6H2O + 6CO2--------- C6H12O6 + 6O2
Cellular Energy
   Animal (and fungi and protist) cells need to
    access the energy stored by photosynthesis.

   They release the energy stored in sugars in a
    process that is the reverse of photosynthesis
   C6H12O6 + 6O2 -------- 6H2O + 6CO2
Glycolysis
   The very first reaction

   Breaks Glucose into smaller sugar
    molecules
Different Pathways after Glycolysis

 There are two main pathways to release
  energy from glucose
 The amount of oxygen available controls
  the pathway

     Plentyof Oxygen = Cellular Respiration
     Not much Oxygen = Fermentation
Two types of Fermentation
   Lactic Acid Fermentation: Our muscles
    carry this out when they run low on
    oxygen, producing ATP and Lactic Acid

   Alcoholic Fermentation: Yeast cells carry
    this out, producing ATP and Alcohol.
Picture of Pathway
                       Glycolysis




Cellular Respiration      Alcoholic      Lactic Acid
                          Fermentation   Fermentation
Cellular Respiration
 Using Oxygen to break apart food
  molecules (sugars)
 Takes place in the mitochondria
 Produces lots of ATP and releases CO2
  and H2O as byproducts
 Muscles will do this as long as they don’t
  run out of oxygen
Lactic Acid Fermentation
 Takes place when there’s not enough
  oxygen for cellular respiration
 Produces ATP, but also Lactic Acid
 Muscles do this when they run low on
  oxygen

   Lactic Acid causes the burning sensation
Alcoholic Fermentation
   Occurs in organisms that do not carry out
    cellular respiration or lactic acid
    fermentation

   Produces ATP, but also Alcohol and CO2
    as byproducts.

   Yeast cells do this—we use them to make
    beer, wine, and bread.
Our Cells
   Will either do:
     Cellularrespiration: During slow, steady
      exercise
     Lactic Acid Fermentation: During strenuous
      exercise like sprinting, or lifting heavy
      weights.

   Do not carry out alcoholic fermentation—it
    would kill your cells
What happens during exercise?
 First 90 Seconds: Cells carry out cellular
  respiration, burning mostly ATP.
 Next approximately 20 minutes: Cells
  carry out cellular respiration, but burn
  glycogen (a small sugar) and other simple
  carbohydrates.
 Only after about 20 minutes: Cells burn
  fat reserves.
What Metabolism Really Is
   Metabolism is how fast your body burns
    energy reserves.
     Fast  metabolism—you burn them fast, and it
      seems like you are always hungry and don’t
      gain much weight
     Slow metabolism—you are better at storing
      reserves than others. You may feel hungry,
      but find you gain weight easily
Can Metabolism Change?
   As we age, our bodies tend to slow down.
   We can’t exercise the way we once could.
   Sometimes metabolism slows, but mostly we
    just don’t burn as many calories.

   Maintaining an exercise routine, especially one
    that runs longer than 20 minutes, can maintain
    your metabolism level.
Why is it hard to lose weight?
 Body is good at changing systems to
  maintain the weight it wants.
 When you start to burn fat, your body
  makes you feel tired and may make you
  crave more sugar.
 If you try to control weight just by diet
  alone, your body will slow down in an
  attempt to save your fat reserves.

				
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