Would you rather…
Your parents are giving you $100 for your
birthday…
– Would you rather receive the money as $100
check or $100 in cash? Why?
– What are the advantages and disadvantages for
each option?
1.) Where do living things get their
energy?
• Heterotrophs?
• Autotrophs?
• Does food give you energy??
Does food give you energy??
The answer…
yes AND no!
Does food give you energy??
Yes! The food we eat has potential energy stored in
the form of carbon-based macromolecules
-Lipids
Biomolecules
-Proteins
-Carbohydrates
-Nucleic Acid
NO!The energy stored within the food is not a type of
energy that our cells can use…in order to get that energy
your cells must conduct cellular respiration
2.) So what is the energy cells use??
ATP!
(Adenosine Triphosphate)
• All living things use ATP for energy
• ATP helps cells to build molecules and move materials
into and out of the cell
• ATP is like
• Cells can “spend” ATP but they constantly have to work
to make more ATP so they don’t run out.
What does ATP look like?
• Adenine (nitrogenous base)
• Ribose (sugar)
• 3 phosphate groups
How do cells use ATP?
• Energy is released
when the bond
between the last
two phosphate
groups is broken
4.) What is ADP? How is it created?
How is ADP like a nearly empty wallet?
ADP
(Adenosine Diphosphate)
• Created when the 3rd phosphate group is removed
from ATP
• This is the “uncharged” form of ATP
• To “recharge” it, the 3rd phosphate group must be
reattached
(this happens
during cellular
respiration)
5.) How are the energy needs of plant cells
similar to those of animal cells? Explain how
plants obtain ATP.
How do cells get ATP?
• Remember, food does not contain ATP
• Food contains macromolecules that can be
broken down to make ATP
• Plants and animals perform Cellular
Respiration to convert the energy stored in
food into ATP
6.) The number of ATP molecules produced
depends on what?
What type of molecule is most commonly
broken down?
How many ATP molecules does glucose (sugar)
break down? How many lipids (fats) does it
yield?
How do cells get ATP?
• The amount of ATP that can be made depends on
the type of biomolecule that is used to create ATP
– Glucose (carbohydrate/sugar) yields about 36 ATP
– A triglyceride (lipid/fat) can yield up to 146 molecules of
ATP
Biomolecules
Lipids
ATP
Carbohydrates
Check your understanding!
• What does ATP stand for?
• Sketch an ATP molecule and label the parts
• Does food contain energy? (EXPLAIN!)
• List three macromolecules found in food.
• Sketch the ATP/ADP cycle
Cellular Respiration – the series of
chemical reactions that convert potential
energy stored in macromolecules of food
into ATP (usable energy).
The equation for the overall process of
cellular respiration is:
C6H12O6 + 6O2  6CO2 + 6H2O + usable energy (ATP)
Chemical Reaction
C6H12O6 + 6O2  6CO2 + 6H2O + usable energy (ATP)
What are the reactants?
What are the products?
Chemical Reaction
C6H12O6 + 6O2  6CO2 + 6H2O + usable energy (ATP)
What are the reactants? C6H12O6 + 6O2
What are the products? 6CO2 + 6H2O
Cellular respiration takes part in 3 stages:
1.) Glycolysis
2.) Krebs Cycle
3.) Electron Transport Chain
Cellular respiration
• Glycolysis is the first step of turning food into
usable energy.
– Takes place in the cytoplasm of the cell
– Does not require oxygen (anaerobic)
– Means “splitting sugar”
• What happens during glycolysis?
– Glucose (6-carbon sugar) is split into two 3-carbon
molecules called pyruvate
Pyruvate
What are the reactants and what are
the products of glycolysis?
2 ATP
Pyruvate
2 ATP
Glucose
2 NAD+
Pyruvate
2 NADH
Review of Glycolysis
• GOAL: to break down glucose to form two pyruvates
• WHO: All life on Earth performs glycolysis
• WHERE: Glycolysis occurs in the cytoplasm of the cell
• Glycolysis produces 4 ATP’s and 2 NADH, but uses 2
ATP’s in the process for a net of 2 ATP and 2 NADH
• NOTE*- This process does not require O2 and does not
yield much energy
• If oxygen is available, the product of glycolysis
(2 pyruvate) is used for the process of cellular
respiration….
– Krebs Cycle
– Electron Transport Chain
The Krebs Cycle
• The main purpose of the Krebs cycle is
to produce the energy carrying
molecules NADH and FADH2.
• Takes place in mitochondrial matrix
• What happens during the Kreb Cycle?
– Breaks down the 2 three-carbon
pyruvate molecules from glycolysis
• The Krebs Cycle is a series of chemical
reactions that further breaks down the
2 three-carbon molecules (pyruvate)
from glycolysis to form ATP, 2 FADH2,
and 8 NADH
Reactants of Krebs Cycle
Products of Krebs Cycle
Electron Transport Chain (ETC)
• 3rd stage of cellular respiration:
• The ETC produces a large amount of ATP = 34 ATP!
• Takes place in the inner mitochondrial membrane
• Energy transferred to electron transport chain (from the
Kreb Cycle)
• Oxygen must enter (reactant)
• Water is released as waste
(product)
Reactants of ETC
Products of ETC
Fermentation
• Fermentation allows glycolysis to continue
making ATP when oxygen is NOT PRESENT
• Fermentation is an anaerobic process
– Occurs when oxygen is NOT available for cellular
respiration
Fermentation
• If no oxygen is available after glycolysis, cells can obtain energy
through the process of anaerobic respiration.
• A common anaerobic process is fermentation.
• Fermentation is NOT an efficient process for making ATP and
results in the formation of far fewer ATP molecules than aerobic
respiration (cellular respiration).
Cellular respiration = 36-38 ATP
Fermentation = approx. 2 ATP
• There are two primary fermentation processes:
1. Lactic Acid Fermentation
2. Alcohol Fermentation
FEEL THE BURN!
• Lactic acid fermentation occurs when oxygen is
NOT available in your cells.
– For example, in muscle tissues during rapid and
vigorous exercise, muscle cells may be depleted of
oxygen (NO O2 is left to conduct cellular respiration!)
– As a result, your muscles switch from cellular
respiration to lactic acid fermentation.
FEEL THE BURN!
• Lactic acid fermentation occurs when oxygen is
NOT available in your cells.
• The pyruvate and NADH formed during glycolysis
is broken down into lactic acid and ATP is
released
C6H12O6 + 2 ADP + P --> 2 C3H5OOH + 2 ATP
Glucose
Lactic Acid
Energy
How Lactic Acid Fermentation Works
• The process of lactic acid
fermentation replaces the
Krebs Cycle & the ETC so
that the cell can have a
continual source of energy,
even in the absence of
oxygen.
• However this shift is only
temporary and cells need
oxygen for sustained
activity.
The lactic acid that builds up in
the tissue causes a burning,
painful sensation.
Fermentation
• If no oxygen is available after glycolysis, cells can obtain
energy through the process of anaerobic respiration.
• A common anaerobic process is fermentation.
• Fermentation is NOT an efficient process for making ATP and
results in the formation of far fewer ATP molecules than
aerobic respiration (cellular respiration).
Cellular respiration = 36-38 ATP
Fermentation = 2-6 ATP
• There are two primary fermentation processes:
1. Lactic Acid Fermentation
2. Alcohol Fermentation
Alcoholic Fermentation
• Occurs in yeasts and bacteria
• Pyruvate and NADH formed during glycolysis is
broken down to produce alcohol and carbon
dioxide and a few ATP
C6H12O6 + 2 ADP + P --> 2 C2H5OH + 2 CO2 + 2 ATP
Glucose
Ethanol
(alcohol)
Carbon
dioxide
Energy!
Fermentation is used in food
production
•
•
•
•
•
•
•
•
•
•
Yogurt
Cheese
Bread
Beer/Meade
Sauerkaraut
Soy sauce
Vinegar
Olives/pickles
Wine/ale
Malt
7. What are the two types of fermentation? What are their chemical equations?
The two main types of fermentation are alcoholic fermentation and lactic fermentation.
In alcoholic fermentation pyruvic acid, an intermediate molecule, is converted into ethanol with
liberation of carbon dioxide. The alcoholic fermentation equation is as follows:
C6H12O6 + 2 ADP + P --> 2 C2H5OH + 2 CO2 + 2 ATP
In lactic fermentation pyruvic acid is transformed into lactic acid and there is no production of
carbon dioxide. The lactic fermentation equation is:
C6H12O6 + 2 ADP + P --> 2 C3H5OOH + 2 ATP
8. In general what are the reagents and products of fermentation?
In fermentation glucose (sugar) is degraded into pyruvic acid (each glucose molecule forms two
pyruvic acid molecules). In this process two molecules of ATP are produced.
According to the type of fermentation, pyruvic acid can produce ethanol and carbon dioxide (in
alcoholic fermentation) or lactic acid (in lactic fermentation). There are other varieties of
fermentation in which pyruvic acid can generate acetic acid (acetic fermentation), propionic
acid, isopropanol (an alcohol too), etc. The type of fermentation depends on the species of the
involved organisms.