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Cellular Respiration
Agriculture Biology
Why are photosynthesis and
respiration important in agriculture?
 Biomass is all plant and animal matter on the
Earth's surface. Harvesting biomass such as
crops, trees or dung and using it to generate
energy such as heat, electricity or motion, is
bioenergy.
 Farmers try to maintain a 40:1 ratio of
photosynthesis to respiration, thus increasing
the amount of biomass stored by the plants.
 More Biomass= More Energy
Why is Respiration
Important?
 Plants use oxygen in the air (or water) to
turn their food (glucose) into energy.
This process of using oxygen to release
energy from food is called
cellular respiration
Interest Grabber
 What kind of organisms undergo cellular
respiration?
 All organisms including photosynthetic
organisms, undergo cellular respiration as
long as oxygen is present
Interest Grabber
 How are the products of
photosynthesis and respiration
related?
 The products of photosynthesis are the
starting materials for respiration
Cellular Respiration
C6H12O6 + 6O2
6CO2 + 6H2O + Energy (ATP)
Cellular Respiration
Photosynthesis vs.
Respiration
Photosynthesis
 Food synthesized (made)
 Energy from sun stored in
glucose
 CO2 taken in
 Oxygen given off
 Produces sugars
 Requires light
 Occurs only in the presence
of chlorophyll
Respiration
 Food broken down
 Energy in glucose
released
 CO2 given off
 Oxygen taken in
 Produces CO2 and H2O
 Does not require light
 Occurs in all living cells
Chemical Pathways
 Cells don’t “burn” glucose
 They gradually release the energy from
glucose and other food compounds
 The process begins with a pathway
called GLYCOLYSIS.
 Glycolysis releases only a small amount of
energy (net yield of 2 ATP)
Glycolysis
 Process in which one molecule of
glucose is broken in half
 Occurs in the cytoplasm of the cell
 This is an anaerobic process
 Produces two molecules of pyruvic acid
 A 3 carbon compound
Glycolysis
 At the pathway’s beginning, 2 molecules
of ATP are used up
 These 2 molecules should be looked at as
an “investment”
 Gives the cell 2 net ATP molecules
Glycolysis
 This process seems like it doesn’t create
very much energy
 But…the cells are able to finish the
process so fast, that they can create
thousands of ATP molecules in just a few
milliseconds
Interest Grabber
 Some of the steps in cellular respiration
take place in the membrane inside the
cell structure called the mitochondrion,
which has a folded inner membrane.
What purpose do these folds serve?
 To find out the answer to this question,
perform this activity.
Interest Grabber
 Obtain two sheets of paper and a metric ruler. What is
the surface area of the paper?
 Roll one sheet of paper into a tube lengthwise. What is
the surface area of the rolled paper?
 Fold the second sheet of paper into a fan. Then, roll
the first sheet of paper around the folded paper so it is
inside the rolled paper. What has happened to the
surface area of the inside of the rolled paper?
 What would be the value of increasing the surface area
of the membrane inside a mitochondrion?
The Krebs Cycle
 In the presence of oxygen, pyruvic acid
produced in glycolysis passes to the second
stage of cellular respiration
 The Kreb’s Cycle (also known as the Citric Acid
Cycle) occurs in the mitochondria of the cell
 Named after Hans Krebs
 1937; he discovered the details of what is now
known as the Krebs Cycle
Krebs Cycle
 During the Krebs cycle the following
occurs
 Pyruvic acid is broken down into carbon
dioxide in a series of energy-extracting
reactions
 NADH, FADH2, CO2 and ATP
 A total of 2 ATP are created from this stage
Krebs Cycle
 Every time you exhale, carbon dioxide is
released
 This carbon dioxide is produced by the
Krebs Cycle
 The ATP produced is used for cellular
activities
Electron Transport
 Electrons passed around during the
Krebs Cycle to the electron transport
chain
 The electron transport chain uses the
high-energy electrons from the Krebs
Cycle to convert ADP into ATP
 A total of 32 ATP are created in the
mitochondria during this stage of resp.
Electron Transport Chain
Fermentation
 If oxygen is not present, glycolysis is
followed by a different pathway
 The combined process of this pathway
and glycolysis is called FERMENTATION
 Fermentation releases energy from food
molecules in the absence of oxygen
Fermentation
 There are two types of fermentation
 Alcoholic Fermentation
 Lactic Acid Fermentation
Alcoholic Fermentation
 Produces carbon dioxide and ethyl
alcohol as wastes
 This is what is produced when yeast is
used to make bread
 When the yeast in the dough runs out of air,
it begins to ferment and produces bubbles of
carbon dioxide to rise the dough
Pyruvic Acid + NADH = Alcohol + CO2 + NAD+
Lactic Acid Fermentation
 Produces lactic acid and NAD+ as wastes
 Produced in your muscles during rapid
exercise when the body cannot supply
enough oxygen to the tissue
Pyruvic Acid + NADH = Lactic acid and NAD+
Quick Energy vs.
Long Term Energy
 The body provides enough ATP to last
about 90 seconds-Quick Energy
 Enough time for a runner to finish a 200-300
meter dash
 Fermentation produces lactic acid as a by
product
 Getting rid of lactic acid requires oxygen
 Thus a runner breathes heavily at the end of the
race to rid the muscles of lactic acid that built up
Quick Energy vs.
Long Term Energy
 How about when you need energy for a
long time?
 The body relies on cellular respiration to
release energy more slowly
 This is why athletes must pace themselves
over a long race---why?
 To allow oxygen to fuel the process of cellular
respiration and make more ATP!!!