cells need...
TRANSCRIPT
1. Organisms obtain energy from food
2. Glucose is main source of food for cells
3. Cells break chemical bonds of glucose; energy released
4. Energy is stored in ATP
5. Making ATP is part of cellular respiration
Slide # 2
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Section:
Cells Need Energy
Respiration
Cellular Respiration
If cellular respiration took place in just one
step:
All of the energy would be released at once
Most would be lost in the form of light and heat.
Instead, a living cell has to release chemical
energy in food molecules a little bit at a time.
Must trap those little bits of energy by using
them to make ATP.
Cellular Respiration
Cellular Respiration - Process that
releases energy by breaking down
glucose and other food molecules in
the presence of oxygen
Cellular Respiration
Requires (Reactants):
1. Glucose
2. Oxygen
Gives Off (Products):
1. Water
2. Carbon Dioxide
3. Energy
3 Stages of Cellular
Respiration
1. Glycolysis
2. Krebs Cycle
3. Electron Transport Chain
Each stage captures some of the chemical energy available in food molecules and uses it to produce ATP.
First Stage: Glycolysis
Glycolysis –A molecule of glucose is
broken into two molecules of pyruvic
acid.
Occurs in the cytoplasm
Does not require oxygen (anaerobic)
1 Glucose 2 Pyruvic Acid
C-C-C-C-C-C C-C-C C-C-C
Glycolysis
Glucose
C-C-C-C-C-C
C-C-C C-C-C
2 Pyruvic Acid
C-C-C C-C-C
2 ATP
2 ADP
4 ADP
4 ATP2 NADH
2 NAD+
TO THE
ELECTRON
TRANSPORT
CHAIN
Products of Glycolysis
1. NET Gain 2 ATP (Major Energy molecule)
2. 2 NADH (Minor Energy molecule)
3. 2 Pyruvic Acid Molecules
http://www.youtube.com/watch?v=C78BMJ7D68I (Glucose – Sugar Sugar Song)
Glycolysis
Fermentation Krebs Cycle
Anaerobic
(no oxygen)
Aerobic
(oxygen)
Second Stage: Fermentation
or Krebs Cycle
Glycolysis can be followed by
fermentation or the Krebs cycle
depending if oxygen is present.
Fermentation will occur if no oxygen is
present.
Krebs Cycle will occur if oxygen is
present.
Second Stage: Fermentation
Fermentation - Releases energy from
food molecules by producing ATP in
the absence of oxygen.
Anaerobic - Does not require oxygen
Occurs in the cytoplasm (cytosol)
Fermentation
Two types of Fermentation:
1. Alcoholic Fermentation
2. Lactic Acid Fermentation
Alcoholic Fermentation
Produces:1. Ethyl alcohol
2. Carbon dioxide
Examples: Used to produce beer and wine
Causes bread dough to rise
Carried out by yeasts and a few other microorganisms
Lactic Acid Fermentation Produces:
1. Lactic Acid
Examples: Produced in your muscles during rapid exercise
Buildup of lactic acid causes a painful, burning sensation…why muscles feel sore
Used in production of cheese, sour cream, yogurt, and pickles.
Carried out by animals and some unicellular prokaryotes (bacteria).
At the End of Glycolysis
90% of the chemical energy that was
available in glucose is still unused
Locked in the high-energy electrons of pyruvic
acid
Oxygen is required for the final steps of
cellular respiration.
Oxygen is the world's most powerful electron
acceptor.
Therefore, cellular respiration is aerobic
(requires oxygen).
Second Stage: Krebs Cycle
Krebs Cycle -
Pyruvic acid is
broken down into
carbon dioxide in a
series of energy-
extracting
reactions.
Occurs in the
mitochondrion.
Krebs Cycle
Starts: Pyruvic Acid
Produces: Carbon Dioxide
Source of all the carbon dioxide in your breath.
Energy Tally - Each Molecule of Pyruvic
Acid Produces:
1 ATP (and NADH/FADH2) All energy molecules!
Third Stage: Electron
Transport Chain
The electron transport chain uses the
high-energy electrons from the Krebs
cycle to convert ADP into ATP.
Oxygen serves as the final electron
acceptor.
Occurs in the mitochondrion.
ATP
Glycolysis: 2 ATP molecules per glucose molecule Needs 2 ATP (Investment)
Produces 4 ATP
Net gain of 2 ATP molecules.
Krebs Cycle and Electron Transport: 34 ATP molecules per glucose molecule
Total = 36 ATP
Black eyed peas review
respiration song
http://www.youtube.com/watch?v=3aZr
kdzrd04&feature=email
Exercise: Quick Energy
1. Muscles only contain enough ATP for a
few seconds of intense activity
2. Then, muscle cells produce their ATP
by lactic acid fermentation.
Lasts only about 90 seconds or about 200 -
300 meters.
Produces lactic acid, which requires oxygen
debt (must repay after the race with plenty
of heavy breathing).
Exercise: Long-Term Energy
(Longer than 90 seconds)
Cellular Respiration is the only way to generate a continuing supply of ATP
Releases energy slowly (why athletes must pace themselves) Body stores energy in muscle and
other tissues in the form of the carbohydrate glycogen (usually enough to last for 15 - 20 min.)
After that, your body begins to break down other stored molecules, including fats, for energy
Photosynthesis vs. Respiration
Photosynthesis and cellular respiration take
place in opposite directions!
Photosynthesis: Use light energy to build a sugar.
carbon dioxide + water + light energy → sugars + oxygen
Respiration: Break down sugar to release energy.
oxygen + sugars → carbon dioxide + water + energy
Respiration: Break Down Glucose
Photosynthesis: Build Glucose
Photosynthesis vs. Respiration
Cellular Respiration
Occurs In:
All eukaryotes
Some prokaryotes
Photosynthesis
Occurs In:
Plants
Algae
Some bacteria
F. Review
1. What is the source of carbon for cellular respiration?
Glucose (C6H
12O
6) is the carbon source.
F.
Review
2. Where do Stages 2 and 3 of cellular respiration take place?
in mitochondria