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Biology
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9-1 Chemical Pathways
Photo Credit: Duomo Photography, Inc.
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9-1 Chemical Pathways
Food serves as a source of raw materials for the cells in the body and as a source of energy.
Animal Cells
Animal
Mitochondrion
Plant
Photo Credits: left: ©Bob Gurr/DRK Photo; middle bottom: ©John Durham/Science Photo Library/Photo Researchers, Inc. ; middle top: ©Ron Boardman/Stone; right: ©Keith Porter/Photo Researchers, Inc.
Plant Cells
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Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria.
Outer membrane
Intermembrane space
Mitochondrion
Animal Cells
Inner membrane
Photo Credits: left: ©Bob Gurr/DRK Photo; middle bottom: ©John Durham/Science Photo Library/Photo Researchers, Inc. ; middle top: ©Ron Boardman/Stone; right: ©Keith Porter/Photo Researchers, Inc.
Plant Cells
Matrix
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5. Chemical Energy and Food
One gram of the sugar glucose (C6H12O6), when burned in the presence of oxygen, releases 3811 calories of heat energy.
A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius.
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6. Chemical Energy and Food
Cells don't “burn” glucose. Instead, they gradually release the energy from glucose and other food compounds.
This process begins with a pathway called glycolysis.
Glycolysis releases a small amount of energy.
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7. Overview of Cellular Respiration
If oxygen is present, glycolysis is followed by the Krebs cycle and the electron transport chain.
Glycolysis, the Krebs cycle, and the electron transport chain make up a process called cellular respiration.
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8. Overview of Cellular Respiration
What is cellular respiration?
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9. Overview of Cellular Respiration
Electrons carried in NADH
Electrons carried
in NADH and
FADH2
Pyruvic acid
Glucose
Glycolysis
Cytoplasm
Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place inside the mitochondria.
Mitochondrion
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10. Overview of Cellular Respiration
Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.
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11. Overview of Cellular Respiration
The equation for cellular respiration is:
6O2 + C6H12O6 → 6CO2 + 6H2O + Energy
oxygen + glucose → carbon dioxide + water + Energy
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12. Overview of Cellular Respiration
Each of the three stages of cellular respiration captures some of the chemical energy available in food molecules and uses it to produce ATP.
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13. Overview of Cellular Respiration
Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place in the mitochondria.
Glycolysis
Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place inside the mitochondria.
Cytoplasm
Mitochondrion
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Glycolysis
What happens during the process of glycolysis?
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Glycolysis
Glycolysis
Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound.
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Glycolysis
ATP Production
At the beginning of glycolysis, the cell uses up 2 molecules of ATP to start the reaction….energize it!!
2 ATP
2 ADP
4 ADP
4 ATP
Glycolysis is the first stage in cellular respiration. During glycolysis, glucose is broken down into 2 molecules of pyruvic acid.
Glucose
2 Pyruvic Acid
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Glycolysis
When glycolysis is complete, 4 ATP molecules have been produced from 4 ADP molecules using the energy released from the breakdown of the glucose molecule.
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2 Pyruvic
acid
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Glycolysis
This gives the cell a net gain of 2 ATP molecules.
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2 Pyruvic
acid
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Glycolysis
NADH Production – One of the reactions of glycolysis removes 4 high-energy electrons and passes then to an electron carrier NAD + (taxi)…..each NAD+ accepts a pair
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2 Pyruvic
acid
Glucose is oxidized…loses electrons in chemical reactions
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Glycolysis
The NADH is an energy carrying molecule that holds the electrons (pair) until they can be transferred to other molecules.
2 ATP
2 ADP
4 ADP
4 ATP
2NAD+
2 Pyruvic
acid 2
To the electron transport chain
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Science 122 Sneak Preview:
In many of the chemical reactions that are part of cellular respiration, the molecules involved are gaining or losing electrons: either receiving electrons from another molecule, or giving electrons to another molecule. When a substance loses electrons, we say is oxidized, and when a substance gains electrons, it is reduced.
LEO the lion says GER
Where “LEO” stands for “loss of electrons is oxidation” and “GER” stands for “gain of electrons is reduction.” Typically, in this type of chemical reaction, both reduction and oxidation will happen simultaneously because one molecule is losing electrons as it gives them to another molecule which, therefore, is gaining them. Because of that, chemists and biologists call these kinds of reactions redox reactions (“red-” from “reduction” and “ox” from “oxidation”).
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Glycolysis
The Advantages of Glycolysis
The process of glycolysis is so fast that cells can produce thousands of ATP molecules in a few milliseconds.
Glycolysis does not require oxygen.
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Fermentation
Fermentation
When 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 by producing ATP in the absence of oxygen.
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Fermentation
Fermentation does not require oxygen—it is an anaerobic process.
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Fermentation
What are the two main types of fermentation?
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Fermentation
The two main types of fermentation are lactic acid fermentation and alcoholic fermentation.
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Fermentation
Alcoholic Fermentation
Yeasts and a few other microorganisms use alcoholic fermentation, forming ethyl alcohol and carbon dioxide as wastes.
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Fermentation
Lactic Acid Fermentation
In many cells, pyruvic acid that accumulates as a result of glycolysis can be converted to lactic acid.
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30. PYRUVIC ACID ___________ OXYGEN WITHOUT
2 kinds of fermentation
___________________ & _____________________
WITHOUT
ANAEROBIC
Alcoholic Lactic acid

31. ALCOHOLIC FERMENTATION
Instead of going to ETC in cell respiration
_______ +_____ →__________ + ______ + _____
PYRUVIC ACID
ALCOHOL
CO2
NAD+
Happens when yeast makes bread dough rise
CO2 bubbles make _____________ in bread
Alcohol _______________
during cooking
air spaces
evaporates

32. ALCOHOLIC FERMENTATION
_______ +_____ →__________ + ______ + _____
PYRUVIC ACID
ALCOHOL
CO2
NAD+
Happens when
___________ make _______ or
____________ make ______
yeast
beer
bacteria
wine

33. LACTIC ACID FERMENTATION
_______ +_____ →______________ + ________
PYRUVIC ACID
LACTIC ACID
NAD+
muscles
Happens in _____________ during ____________when body
can’t get oxygen to tissues
fast enough.
Lactic acid builds up in
muscles causing soreness
exercise

34. LACTIC ACID FERMENTATION
_______ +_____ →______________ + ________
PYRUVIC ACID
LACTIC ACID
NAD+
Happens when bacteria are used to make ___food_______and ____beverages____ like:
Yogurt, buttermilk,
sauerkraut, pickles, cheese
sour cream, & kimchi

35. WHY DO FERMENTATION? WHY NOT JUST KEEP MAKING ATP USING GLYCOLYSIS?
WITHOUT OXYGEN, PYRUVIC ACID ___________ and all the _______ carriers get full.
Eventually glycolysis will
builds up
NAD+
NAD+

36. → → FERMENTATION HAPPENS so cells can ____________________
PYRUVIC ACID
_______ +_____ →__________ + ______ + _____
CO2
NAD+
ALCOHOL →
NAD+
LACTIC ACID
______ →
You get the NAD+ taxis back
FERMENTATION HAPPENS so cells can ____________________
needed to keep glycolysis going
REGENERATE the NAD+

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9-1
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9-1
The raw materials required for cellular respiration are
carbon dioxide and oxygen.
glucose and water.
glucose and oxygen.
carbon dioxide and water.
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9-1
Glycolysis occurs in the
mitochondria.
cytoplasm.
nucleus.
chloroplasts.
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9-1
The net gain of ATP molecules after glycolysis is
3 ATP molecules.
2 ATP molecules.
3 pyruvic acid molecules.
4 pyruvic acid molecules
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9-1
Fermentation releases energy from food molecules in the absence of
oxygen.
glucose.
NADH.
alcohol.
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9-1
The first step in fermentation is always
lactic acid production.
the Krebs cycle.
glycolysis.
alcohol production.
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43. END OF SECTION