Download Ch 8&9 combined

Energy Flow Through Living
Things: Photosynthesis &
Cellular Respiration
Chapter 8&9
1
8-1 Energy and Life
• Living things need energy to survive
– comes from food
– energy in most food comes from the sun
• Plants use light energy from the sun to
produce food
• autotrophs organisms that make their own food
– Ex - plants
• heterotrophs organisms that must obtain energy
from the foods they consume
– animals
2
Chemical Energy and ATP
• Energy – the ability to do work
– Forms: light, heat, electricity, chemical
compounds
• chemical compound that cells use to store
and release energy is adenosine
triphosphate (ATP)
– ATP - basic energy source for all cells
3
Chemical Energy and ATP
• ATP consists of:
– adenine
– ribose (a 5-carbon sugar)
The three phosphate
groups are the key to
ATP's ability to store
and release energy.
– 3 phosphate groups
Adenine
ATP
Ribose
3 Phosphate groups
4
Chemical Energy and ATP
– Storing Energy
• ADP has two phosphate groups instead of three.
• A cell can store small amounts of energy by adding a
phosphate group to ADP.
ATP
ADP
+
Adenosine Diphosphate
(ADP) + Phosphate
Partially
charged
battery
Energy
Energy
Fully
charged
battery
Adenosine Triphosphate (ATP)
5
Chemical Energy and ATP
– Releasing Energy
• Energy stored in ATP is released by breaking the
chemical bond between the second and third
phosphates.
2 Phosphate groups
P
ADP
6
Chemical Energy and ATP
ATP energy uses:
- cellular activities: active transport,
protein synthesis
- muscle contraction
• Most cells have only a small amount of ATP,
because it is not a good way to store large
amounts of energy.
• Cells can regenerate ATP from ADP as needed
by using the energy in foods like glucose.
7
8-2 Photosynthesis
• Photosynthesis - the process in which
green plants use the energy of sunlight to
convert water and carbon dioxide into
high-energy carbohydrates and oxygen
8
The Photosynthesis Equation
• The Photosynthesis Equation
• The equation for photosynthesis is:
• 6CO2 + 6H2O
Light
• carbon dioxide + water
C6H12O6 + 6O2
Light
sugars + oxygen
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The Photosynthesis Equation
Light energy
H2O
Light-Dependent
Reactions
(thylakoids)
ADP
+
NADP
Sugar
O2
ATP
NADPH
Calvin Cycle
(stroma)
CO2
+
H20
10
Light and Pigments
• photosynthesis requires chlorophyll
– pigments - light-absorbing molecules that
gather the sun's energy
• The main pigment in plants is chlorophyll.
• There are two main types of chlorophyll:
– chlorophyll a
– chlorophyll b
11
Light and Pigments
Estimated Absorption (%)
• Chlorophyll absorbs light well in the blue-violet and
red regions of the visible spectrum.
100
80
60
Chlorophyll b
Chlorophyll a
40
20
0
(nm)
400 450 Wavelength
500 550 600
650 700 750
Wavelength (nm)
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Light and Pigments
Estimated Absorption (%)
• Chlorophyll does not absorb light will in the green
region of the spectrum. Green light is reflected by
leaves, which is why plants look green.
100
80
60
Chlorophyll b
Chlorophyll a
40
20
0
400 450 500 550 600 650 700 750
Wavelength (nm)
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Light Energy
• Light is a form of energy
– compound that absorbs light also absorbs
energy from that light
– chlorophyll absorbs light  the energy is
transferred directly to electrons in the
chlorophyll molecule  raising the energy
levels of these electrons
– high-energy electrons are what make
photosynthesis work
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Pop Quiz
1. This molecule is called _____.
2. Energy in this molecule is stored in the _____.
Word Bank
ADP
Ribose
Phosphate groups
Bonds
ATP
Adenine
Adenosine
3.
5.
4.
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8-3 Inside a Chloroplast
• Inside a Chloroplast
• In plants, photosynthesis takes place inside
chloroplasts.
Plant
Chloroplast
Plant cells
16
Inside a Chloroplast
• Chloroplasts contain thylakoids—saclike
photosynthetic membranes.
Single
thylakoid
Chloroplast
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Inside a Chloroplast
• Thylakoids are arranged in stacks known as grana.
A singular stack is called a granum.
• Stroma – space outside of the thylakoids
Granum
Stroma
Chloroplast
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Inside a Chloroplast
• Proteins in the thylakoid membrane organize
chlorophyll and other pigments into clusters called
photosystems, which are the light-collecting units
of the chloroplast.
Photosystems
Chloroplast
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Photosynthesis Reactions
• reactions of photosystems include:
– light-dependent reactions (requires light)
• take place within the thylakoid membranes
• uses water, ADP, and NADP+
• produces oxygen, ATP, and NADPH
– light-independent reactions (Calvin cycle)
• takes place in the stroma
• ATP and NADPH not stable enough to store the
energy they carry for more than a few minutes
• uses ATP and NADPH energy to build high-energy
sugars for long term storage
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Photosynthesis Reactions
• The two sets of photosynthetic reactions
work together.
– The light-dependent reactions trap sunlight
energy in chemical form.
– The light-independent reactions use that
chemical energy to produce stable, highenergy sugars from carbon dioxide and water.
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Inside a Chloroplast
H2O
CO2
Light
NADP+
ADP + P
Lightdependent
reactions
Calvin
Calvin
cycle
Cycle
Chloroplast
O2
Sugars
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Electron Carriers
• electrons in chlorophyll absorb sunlight 
electrons gain energy
– Cells use electron carriers to transport these
high-energy electrons from chlorophyll to
other molecules
– One carrier molecule is NADP+.
• transport electrons
• NADP+ accepts and holds 2 high-energy electrons
along with a hydrogen ion (H+) - NADP+  NADPH
• energy of sunlight can be trapped in chemical form
• NADPH carries high-energy electrons to chemical
reactions elsewhere in the cell to make
23
carbohydrates
Factors Affecting
Photosynthesis
• Many factors affect the rate of
photosynthesis, including:
• Water
• Temperature
• Intensity of light
24
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
Plant Cells
25
• Both plant and animal cells carry out the final
stages of cellular respiration in the mitochondria.
Outer membrane
Intermembrane
Mitochondrion
space
Animal Cells
Plant Cells
Inner
membrane
Matrix
26
Chemical Energy and Food
• Chemical Energy and Food
– One gram of the sugar glucose (C6H12O6),
when burned in the presence of oxygen,
releases 3811 calories of heat energy
– calorie - the amount of energy needed to
raise the temperature of 1 gram of water 1
degree Celsius
• Cells gradually release the energy from glucose
and other food compounds beginning with
glycolysis - releases a small amount of energy.
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Overview of Cellular Respiration
• If oxygen is present:
– cellular respiration - the process that
releases energy by breaking down glucose
and other food molecules in the presence
of oxygen
– glycolysis  Krebs cycle  electron transport
chain
• equation:
– 6O2 + C6H12O6 → 6CO2 + 6H2O + Energy
– oxygen + glucose → carbon dioxide + water + Energy
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Overview of Cellular Respiration
Electrons carried in NADH
Pyruvic
acid
Glucose
Electrons carried
in NADH and
FADH2
Glycolysis
Cytoplasm
Mitochondrion
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Overview of Cellular Respiration
• Glycolysis – cytoplasm
• Krebs cycle and electron transport - mitochondria
Glycolysis
Cytoplasm
Mitochondrion
30
Stretch break
You have 2 minutes to talk,
stretch, stand up…
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Glycolysis
• the process in which one molecule of glucose is
broken in half, producing two molecules of
pyruvic acid, a 3-carbon compound
– ATP Production
• cell uses up 2 molecules of ATP to start the reaction
• When glycolysis is complete, 4 ATP molecules have
been produced  a net gain of 2 ATP molecules
– NADH Production
• removes 4 high-energy electrons  electron carrier
called NAD+  becomes an NADH molecule.
• The NADH molecule holds the electrons until they can
be transferred to other molecules.
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Glycolysis
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2 Pyruvic
acid
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Glycolysis
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2 Pyruvic
acid
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Glycolysis
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2 Pyruvic
acid
35
Glycolysis
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2NAD+
2 Pyruvic
acid
36
Glycolysis
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2NAD+
2
2 Pyruvic
acid
37
Glycolysis
2 ATP
2 ADP
4 ADP
2NAD+
4 ATP
2
2 Pyruvic
acid
To the electron
transport chain
38
Glycolysis
– The Advantages of Glycolysis
• very fast - cells can produce thousands of ATP
molecules in a few milliseconds
• does not require oxygen
39
Fermentation
• oxygen is not present  glycolysis is
followed by a different pathway fermentation
– Fermentation – release of energy (ATP) from
food in the absence of oxygen
– cells convert NADH to NAD+ by passing highenergy electrons back to pyruvic acid
– Anaerobic – does not require oxygen
40
Fermentation
– Alcoholic Fermentation
• Yeasts and a few other microorganisms use
alcoholic fermentation
• Forms ethyl alcohol and carbon dioxide as wastes
– equation:
• pyruvic acid + NADH → alcohol + CO2 + NAD+
41
Fermentation
– Lactic Acid Fermentation
• pyruvic acid that accumulates from glycolysis 
converted to lactic acid
• regenerates NAD+ so that glycolysis can continue
– converts glucose into lactic acid
– equation:
• pyruvic acid + NADH → lactic acid + NAD+
42
Fermentation
• The first part of the equation is glycolysis.
43
Fermentation
• The second part shows the conversion of pyruvic
acid to lactic acid.
44
The Totals
45
Comparing Photosynthesis and Cellular
Respiration
• The energy flows in photosynthesis and
cellular respiration take place in opposite
directions.
46
Comparing Photosynthesis and Cellular
Respiration
• On a global level, photosynthesis and
cellular respiration are also opposites.
– Photosynthesis removes carbon dioxide from
the atmosphere and cellular respiration puts it
back.
– Photosynthesis releases oxygen into the
atmosphere and cellular respiration uses that
oxygen to release energy from food.
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