Chapter 5
Photosynthesis and Cellular Respiration
Section 1: Energy and Living Things
Section 2: Photosynthesis
Section 3: Cellular Respiration
Section 1
Energy and Living Things
Objectives:
•Analyze the flow of energy through living systems.
•Compare the metabolism of autotrophs with that of
heterotrophs.
•Describe the role of ATP in metabolism.
•Describe how energy is released from ATP.
Section 1
Energy and Living Things
Energy in Living Systems
•Building Molecules That Store Energy
Autotrophs make their own food by using energy
from sunlight or inorganic substances to build
organic compounds. Many autotrophs make food
by the process of photosynthesis.
•Breaking Down Food for Energy Energy from
sunlight flows through living systems, from autotrophs
to heterotrophs. Heterotrophs release the energy in food
through the process of cellular respiration.
Section 1
Energy and Living Things
Energy in Living Systems continued
•Transfer of Energy to ATP Cellular respiration
releases much of the energy in food to make ATP,
the energy “currency” inside cells.
Section 1
Energy and Living Things
ATP
•ATP Releases Energy ATP supplies cells with
energy needed for metabolism. Energy is
released upon the breakdown of ATP to ADP.
Section 2
Photosynthesis
Objectives:
•Summarize how energy is captured from sunlight in
the first stage of photosynthesis.
•Analyze the function of electron transport chains in
the second stage of photosynthesis.
•Relate the Calvin cycle to carbon dioxide fixation
in the third stage of photosynthesis.
•Identify three environmental factors that affect
the rate of photosynthesis.
Section 2
Photosynthesis
Using the Energy in Sunlight
•The Stages of Photosynthesis Photosynthesis
has three stages. First, energy is captured from
sunlight. Second, energy is temporarily stored in
ATP and NADPH. Third, organic compounds are
made using ATP, NADPH, and carbon dioxide.
Section 2
Photosynthesis
Stage One: Absorption of Light Energy
•Pigments Pigments, such as chlorophyll, absorb
light energy during photosynthesis.
•Production of Oxygen During photosynthesis,
water molecules are split to release oxygen by an
enzyme inside structures called thylakoids.
Section 2
Photosynthesis
Stage Two: Conversion of Light Energy
•Electron Transport Chains Electrons excited
by light travel through electron transport chains,
in which ATP and NADPH are produced.
Section 2
Photosynthesis
Stage Three: Storage of Energy
•Calvin Cycle Through carbon dioxide fixation,
often by the Calvin cycle, carbon dioxide in the
atmosphere is used to make organic compounds,
which store energy.
•Factors that Affect Photosynthesis Photosynthesis
is directly affected by environmental factors such as
the intensity of light, the concentration of carbon
dioxide, and temperature.
Section 3
Cellular Respiration
Objectives:
•Summarize how glucose is broken down in the first
stage of cellular respiration.
•Describe how ATP is made in the second stage of
cellular respiration.
•Identify the role of fermentation in the second
stage of cellular respiration.
•Evaluate the importance of oxygen in aerobic
respiration.
Section 3
Cellular Respiration
Cellular Energy
•The Stages of Cellular Respiration Cellular
respiration has two stages.
•Glycolysis The first stage of cellular respiration is
called glycolysis.
•Aerobic and Anaerobic Respiration The second
stage of cellular respiration is either aerobic respiration
(in the presence of oxygen) or anaerobic respiration (in
the absence of oxygen). A large amount of ATP is made
during aerobic respiration. NAD+ is recycled during
the anaerobic process of fermentation.
Section 3
Cellular Respiration
Stage One: Breakdown of Glucose
•Glycolysis Glucose is broken down to pyruvate
during glycolysis, making some ATP.
Section 3
Cellular Respiration
Stage Two: Production of ATP
•Krebs Cycle The Krebs cycle is a series of
reactions that produce energy-storing molecules
during aerobic respiration.
•Electron Transport Chain During aerobic
respiration, large amounts of ATP are made in an
electron transport chain.
Section 3
Cellular Respiration
Fermentation in the Absence of Oxygen
•Fermentation When oxygen is not present,
fermentation follows glycolysis, regenerating NAD+
needed for glycolysis to continue.
•Lactic Acid Fermentation In lactic acid
fermentation, pyruvate is converted to lactate.
Section 3
Cellular Respiration
Fermentation in the Absence
of Oxygen continued
•Alcoholic Fermentation In alcoholic
fermentation, pyruvate is broken down to ethanol,
releasing carbon dioxide.
•Production of ATP Although a small amount of
ATP is made during fermentation, most of a cell’s
ATP is made during aerobic respiration.