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Cellular Energy
Section 1: How Organisms Obtain Energy
Section 2: Photosynthesis
Section 3: Cellular Respiration
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Section 1
Cellular Energy
How Organisms Obtain Energy
Transformation of Energy
 Energy is the ability to do work.
 Thermodynamics is the study of the flow and
transformation of energy in the universe.
Section 1
Cellular Energy
How Organisms Obtain Energy
Laws of Thermodynamics
 First law—energy can be converted from one
form to another, but it cannot be created nor
destroyed.
 Second law—energy cannot be converted
without the loss of usable energy.
Section 1
Cellular Energy
How Organisms Obtain Energy
Autotrophs and Heterotrophs
 Autotrophs are organisms that make their
own food.
 Heterotrophs are organisms that need to
ingest food to obtain energy.
Section 1
Cellular Energy
How Organisms Obtain Energy
Metabolism
 All of the chemical reactions in a cell
 Photosynthesis—light energy from the Sun is
converted to chemical energy for use by the
cell
 Cellular respiration—organic molecules are
broken down to release energy for use by
the cell
Section 1
Cellular Energy
How Organisms Obtain Energy
ATP: The Unit of Cellular Energy
 ATP releases energy
when the bond between
the second and third
phosphate groups is
broken, forming a
molecule called
adenosine diphosphate
(ADP) and a free
phosphate group.
ATP
Section 2
Cellular Energy
Photosynthesis
Overview of Photosynthesis
 Photosynthesis occurs in two phases.
 Light-dependent reactions
 Light-independent reactions – Dark Rxns
Section 2
Cellular Energy
Photosynthesis
Phase One: Light Reactions
 The absorption of light is the first step in
photosynthesis.
 Chloroplasts capture light energy.
What’s Going on in a Chloroplast?
Section 2
Cellular Energy
Photosynthesis
Electron Transport
Step 1 Light energy excites electrons in photosystem II and
also causes a water molecule to split, releasing an electron
into the electron transport system, H+ into the thylakoid space,
and O2 as a waste product.
Section 2
Cellular Energy
Photosynthesis
Step 2 The excited electrons move from photosystem
II to an electron-acceptor molecule in the thylakoid
membrane.
Step 3 The electron-acceptor molecule transfers the
electrons along a series of electron-carriers to
photosystem I.
Section 2
Cellular Energy
Photosynthesis
Step 4 Photosystem I transfers the electrons to a
protein called ferrodoxin.
Step 5 Ferrodoxin transfers the electrons to the
electron carrier NADP+, forming the energy-storing
molecule NADPH.
Metabolic Pathways
Catabolic Pathway
• Releases Energy
Anabolic Pathway
• Stores (Uses) Energy
• Breaks Down Molecules
• Makes Molecules
Light Dependent RXN Long Version
• Go to 4:50
Section 2
Cellular Energy
Short Version
Section 2
Cellular Energy
Photosynthesis
Phase Two: The Calvin Cycle
 In the second
phase of
photosynthesis,
called the Calvin
cycle, energy is
stored in organic
molecules such
as glucose.
Section 2
Cellular Energy
Section 2
Cellular Energy
Photosynthesis
 Step 1 Six CO2 molecules combine with six 5carbon compounds to form twelve 3-carbon
molecules called 3-PGA.
 Step 2 The chemical energy stored in ATP and
NADPH is transferred to the 3-PGA molecules
to form high-energy molecules called G3P.
Section 2
Cellular Energy
Photosynthesis
 Step 3 Two G3P molecules leave the cycle to
be used for the production of glucose and other
organic compounds.
 Step 4 An enzyme called rubisco converts the
remaining ten G3P molecules into 5-carbon
molecules called RuBP.
 These molecules combine with new carbon
dioxide molecules to continue the cycle.
Section 2
Cellular Energy
Photosynthesis
Alternative Pathways
 C4 plants
Fix carbon dioxide into 4 carbon compounds instead of 3.
Keep their stomata closed during hot days.
Sugar cane and corn
 CAM plants
Crassulacean acid metabolism
Only allow CO2 to enter leaves at night when its cooler and humid
Pineapple plant, cacti, orchids
Section 3
Cellular Energy
Cellular Respiration
Overview of Cellular Respiration
 Organisms obtain energy in a process called
cellular respiration.
 The equation for cellular respiration is the
opposite of the equation for photosynthesis.
Section 3
Cellular Energy
Cellular Respiration
 Cellular respiration occurs in two main parts.
 Glycolysis
 Aerobic respiration
Section 3
Cellular Energy
Cellular Respiration
Glycolysis
 Glucose is broken down in the cytoplasm
through the process of glycolysis.
 Two molecules of ATP and two molecules
of NADH are formed for each molecule of
glucose that is broken down.
Section 3
Cellular Energy
Cellular Respiration
Krebs Cycle
 Glycolysis has a net result of two ATP and
two pyruvate.
 Most of the energy from the glucose is still
contained in the pyruvate.
 The series of reactions in which pyruvate is
broken down into carbon dioxide is called the
Krebs cycle.
Section 3
Cellular Energy
Cellular Respiration
 The net yield from the
Krebs cycle is six CO2
molecules, two ATP,
eight NADH, and two
FADH2.
Section 3
Cellular Energy
Section 3
Cellular Energy
Cellular Respiration
Electron Transport
 Final step in the breakdown of glucose
 Point at which ATP is produced
 Produces 24 ATP
Section 3
Cellular Energy
Cellular Respiration
Anaerobic Respiration
 The anaerobic pathway that follows glycolysis
 Two main types
 Lactic acid fermentation
 Alcohol fermentation
Cellular Respiration
Chapter
Cellular Energy
Chapter Resource Menu
Chapter Diagnostic Questions
Formative Test Questions
Chapter Assessment Questions
Standardized Test Practice
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Vocabulary
Animation
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Chapter
Cellular Energy
Chapter Diagnostic
Questions
Which statement describes the law of
conservation of energy?
A.
B.
C.
D.
Energy cannot be converted or destroyed.
Energy can be converted and destroyed.
Energy can be converted but not destroyed.
Energy can be destroyed but not converted.
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Chapter Diagnostic
Questions
In which metabolic process are molecules
broken down to produce carbon dioxide and
water?
A. photosynthesis
B. cellular respiration
C. homeostasis
D. fermentation
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Chapter Diagnostic
Questions
At the end of the Calvin cycle, where is energy
stored?
A. NADPH
B. ATP
C. chloroplast
D. glucose
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Section 1 Formative
Questions
Which law of thermodynamics explains why the
ladybug receives the least amount of usable energy?
A. the first law of thermodynamics
B. the second law of thermodynamics
1.
2.
A
B
Chapter
Cellular Energy
Section 1 Formative
Questions
All of the energy from the
food you eat comes from
the sun.
A. true
B. false
1.
2.
A
B
Chapter
Cellular Energy
Section 1 Formative
Questions
Why is cellular respiration a catabolic pathway?
A. Energy is used to form glucose and oxygen.
B. Energy is converted from water to carbon
dioxide.
C. Energy that is lost is converted to thermal
1.
energy.
2.
3.
D. Energy is released by the breakdown of4.
molecules.
A
B
C
D
Chapter
Cellular Energy
Section 1 Formative
Questions
Why is adenosine triphosphate (ATP) such an
important biological molecule?
A. It captures light energy from the sun.
B. It is produced in anabolic pathways.
C. It stores and releases chemical energy.
D. It converts mechanical energy to thermal
energy.
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Section 2 Formative
Questions
Where in the plant cell does
photosynthesis take place?
A. chloroplasts
B. Golgi apparatus
C. mitochondria
D. vacuoles
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Section 2 Formative
Questions
Which range of
wavelengths is reflected
by chlorophylls a and b?
A. 400-500 nm
B. 500-600 nm
C. 600-700 nm
1.
2.
3.
A
B
C
Chapter
Cellular Energy
Section 2 Formative
Questions
Which mechanism of photosynthesis uses
the movement of hydrogen ions (H+) across
a concentration gradient to synthesize ATP?
A. absorption
B. chemiosmosis
C. electron transport
D. C2 pathway
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Section 2 Formative
Questions
How are the C4 pathway and the CAM pathway
an adaptive strategy for some plants?
A. They accelerate photosynthesis.
B. They release more oxygen.
C. They help the plant conserve water.
D. They reduce the requirement for ATP.
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Section 3 Formative
Questions
What is the overall purpose of cellular
respiration?
A. to make ATP
B. to process H2O
C. to store glucose
D. to deliver oxygen
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Section 3 Formative
Questions
Which represents the general sequence of
cellular respiration?
A. TCA cycle  chemiosmosis  glycolysis
B. glycolysis  Krebs cycle  electron transport
C. electron absorption  catalysis 
phosphorylation
D. aerobic pathway  anaerobic pathway 
fermentation
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Section 3 Formative
Questions
Which stage of cellular respiration is the
anaerobic process?
A. glycolysis
B. Krebs cycle
C. electron transport
1.
2.
3.
A
B
C
Chapter
Cellular Energy
Section 3 Formative
Questions
Which molecule
generated by the Krebs
cycle is a waste product?
A. CoA
B. CO2
C. FADH2
D. NADH
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Chapter Assessment
Questions
Look at the following figure.
Which part of the chloroplast
is a sac-like membrane
arranged in stacks?
A. grana
B. stroma
C. thylakoids
D. Golgi apparatus
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Chapter Assessment
Questions
During the Krebs cycle,
pyruvate is broken down
into what compound?
A. H2O
B. O2
C. CO
D. CO2
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Chapter Assessment
Questions
Look at the following figure.
Which molecule is released
when ATP becomes ADP?
A. phosphate group
B. water molecule
C. ribose sugar
D. energy cells
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Standardized Test
Practice
Which metabolic process is photosynthesis?
A
1.
2.
B
A
B
Chapter
Cellular Energy
Standardized Test
Practice
At the beginning of photosynthesis, which
molecule is split to produce oxygen (O2) as
a waste product?
A. CO2
B. H2O
C. C6H12O6
D. 3-PGA
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Standardized Test
Practice
Which molecule helps provide the energy that
drives this cycle?
A. 3-PGA
B. CO2
C. NADPH
D. rubisco
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Standardized Test
Practice
Which product of the Calvin cycle is used for
the production of glucose and other organic
compounds?
A. ADP
B. CO2
C. G3P
D. NADP+
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Standardized Test
Practice
What is the final step of cellular respiration?
A. O2 and H+ form H2O.
B. Electrons and H2O generate ATP.
C. C6H12O6 is broken down into CO2.
D. NADH and FADH2 gain electrons.
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Standardized Test
Practice
What prevents pyruvate from
entering the Krebs cycle and
instead results in this pathway?
A. a buildup of CO2
B. a lack of oxygen
C. an excess of glucose
D. an increased demand for ATP
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Standardized Test
Practice
Which is not a process that occurs in both
cellular respiration and glycolysis?
A. chemiosmosis
B. electron transport
C. glycolysis
D. production of G3P
1.
2.
3.
4.
A
B
C
D
Chapter
Cellular Energy
Glencoe Biology Transparencies
Chapter
Cellular Energy
Image Bank
Section 1
Cellular Energy
Vocabulary
Section 1
energy
thermodynamics
metabolism
Photosynthesis
cellular respiration
adenosine triphosphate (ATP)
Section 2
Cellular Energy
Vocabulary
Section 2
thylakoid
granum
stroma
pigment
NADP+
Calvin cycle
rubisco
Section 3
Cellular Energy
Vocabulary
Section 3
anaerobic process
aerobic respiration
aerobic process
glycolysis
Krebs cycle
fermentation
Chapter
Cellular Energy
Animation
 ATP
 The Calvin Cycle
 Visualizing Electron Transport
 The Krebs Cycle (Citric Acid Cycle)
Chapter
Cellular Energy
Chapter
Cellular Energy
Chapter
Cellular Energy