Cell Energy

1
Cell Energy

• Accessing energy stored by photosynthesis

2
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

3
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

4
Glycolysis

• The very first reaction
• Breaks Glucose into smaller sugar molecules

5
Different Pathways after Glycolysis

• There are two main pathways to release energy
  from glucose
• The amount of oxygen available controls the
  pathway
• Plenty of Oxygen Cellular Respiration
• Not much Oxygen Fermentation

6
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.

7
Picture of Pathway

• Glycolysis

Lots of Oxygen
Not enough Oxygen
Cellular Respiration
Alcoholic Fermentation
Lactic Acid Fermentation
8
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 dont run
  out of oxygen

9
Lactic Acid Fermentation

• Takes place when theres 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

10
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 thiswe use them to make beer,
  wine, and bread.

11
Our Cells

• Will either do
• Cellular respiration During slow, steady
  exercise
• Lactic Acid Fermentation During strenuous
  exercise like sprinting, or lifting heavy
  weights.
• Do not carry out alcoholic fermentationit would
  kill your cells

12
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.

13
What Metabolism Really Is

• Metabolism is how fast your body burns energy
  reserves.
• Fast metabolismyou burn them fast, and it seems
  like you are always hungry and dont gain much
  weight
• Slow metabolismyou are better at storing
  reserves than others. You may feel hungry, but
  find you gain weight easily

14
Can Metabolism Change?

• As we age, our bodies tend to slow down.
• We cant exercise the way we once could.
• Sometimes metabolism slows, but mostly we just
  dont burn as many calories.
• Maintaining an exercise routine, especially one
  that runs longer than 20 minutes, can maintain
  your metabolism level.

15
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.