Photosynthesis and
Cellular Respiration
Outline
I. Photosynthesis
A. Introduction
B. Reactions
II. Cellular Respiration
A. Introduction
B. Reactions
Review: What is ATP?
Review: What is ATP?



Adenosine Triphospate
Adenine + Ribose + 3 Phosphate groups
One of the principle chemical compounds that
cells use to STORE and RELEASE energy.
Storing Energy

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ADP (Adenine diphospate)
Only 2 phosphates (hence the “di”)
Key to how living things STORE energy!
(When energy is available, the cell stores it by
adding phosphate to make ATP=stored battery
ready to power cell).
Releasing Energy

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“Shooting off” 1 phosphate  ENERGY!!
ATP provides energy for a variety of cellular
activities!
Ex: active transport across cell membranes,
protein synthesis, and muscle contraction
ADP ATP

Cells regenerate ATP from ADP as needed by
using energy in FOOD, aka …
ADP ATP

Cells regenerate ATP from ADP as needed by
using energy in FOOD, aka …
GLUCOSE!
Photosynthesis


Photo = light
Synthesis = putting together
Photosynthesis

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Converting sun energy into chemical energy
usable by cells (glucose)
Autotrophs: self feeders, organisms capable of
making their own food
–
–
Photoautotrophs: use sun energy e.g. plants
photosynthesis-makes glucose from light
Chemoautotrophs: use chemical energy, NOT
sunlight

e.g. bacteria that use sulfide or methane
Photosynthesis

Photosynthesis
takes place in
specialized structures
inside plant cells
called chloroplasts
–
Light absorbing
pigment molecules e.g.
chlorophyll
Why are leaves green?


Chlorophyll absorbs all of the light waves except
green. Because the green is not absorbed, it is
reflected, so that is the only color wavelength our
eye can pick up.
Accessory pigments – help to fill in this gap
–
–
Carotenoids – orange (like carrots)
Xanothphyl – yellow
Inside the chloroplast

Thylakoids: Sac-like photosynthetic membranes
arranged in stacks.
–
Organize chlorophyll/other pigments into
photosystems (clusters that collect light).
What does a plant need to survive?
Overall Reaction
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6CO2 + 6H2O + light energy → C6H12O6 + 6O2
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Carbon dioxide + water + light  glucose + oxygen
KNOW BOTH OF THESE EQUATIONS.
YOU WILL SEE THEM AGAIN!
2 types of reactions in photosynthesis
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Light dependent
Light independent (CALVIN CYCLE)
Electron Carriers

Overview:
–
–
–
–
–
Sun excites electrons = gain energy
Need special carrier! (Think red-hot coal!)
Electron acceptor molecules (ex: NADP+)
NADP+ uses hydrogen ions (H+) to trap some of the
sunlight in chemical form = converts to NADPH.
Carries e- to other chemical reactions in the cell
Light Dependent Reactions
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Occur in the thylakoid!
Produce oxygen gas
Converts ADP and NADP+ into energy
carriers ATP + NADPH
Light Dependent Reactions
Overview:
Pigments in Photosystems absorb light = electrons
gain energy
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Electrons are passed on to the Electron Transport Chain
Does the chorophyll run out of electrons?
Light Dependent Reactions

In Thylakoid:
–
–
–
System that provides new e- to chlorophyll to replace
ones lost
Electrons come from water! H2O
Enzymes on inner surface membrane of thylakoid
break up each H2O into:
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2 e- (replace e- lost to the ETC)
2H+ions (released inside thylakoid membrane)
1 oxygen atom (released into the air!)
Light-dependent Reactions
5. H+ ions cant cross membrane directly
–
ATP synthase!
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Allows H+ ions to pass through it!
As it turns, binds ADP and phosphate group ….
Producing ATP!
Energy Shuttling
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Recall ATP: cellular energy-nucleotide based
molecule with 3 phosphate groups bonded to it,
when removing the third phosphate group, lots of
energy liberated= superb molecule for
shuttling energy around within cells.
Other energy shuttles-coenzymes (nucleotide
based molecules): move electrons and protons
around within the cell
NADP+, NADPH
NAD+, NADP
FAD, FADH2
This light dependent reaction is the source of nearly
ALL of the oxygen in Earth’s atmosphere!
Thanks photosynthesis!
Light-dependent Reactions
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Photosystem: light capturing unit, contains chlorophyll,
the light capturing pigment
Electron transport system: sequence of electron
carrier molecules that shuttle electrons, energy released
to make ATP
Electrons in chlorophyll must be replaced so that cycle
may continue-these electrons come from water
molecules, Oxygen is liberated from the light reactions
Light reactions yield ATP and NADPH used to fuel
the reactions of the Calvin cycle (light independent or
dark reactions)
Uses: H2O, ADP, and NADP+
Makes: Oxygen, ATP, and NADPH
Calvin Cycle (light independent or
“dark” reactions)
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ATP and NADPH generated in light reactions
used to fuel the reactions which take CO2 and
H+ to make glucose.
Simplified version of how carbon and energy
enter the food chain
Harvesting Chemical Energy
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Plants and animals both use products of
photosynthesis (glucose) for metabolic fuel
Heterotrophs: must take in energy from outside
sources, cannot make their own e.g. animals
When we take in glucose (or other carbs),
proteins, and fats-these foods don’t come to
us the way our cells can use them
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular Respiration
CO2 and O2
Water
Glucose
Location: Where
does it take place?
Light
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
CO2 and O2
Water
Glucose
Location: Where
does it take place?
Light
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
CO2 and O2
Water
Glucose
Location: Where
does it take place?
Light
Uses CO2; Produces
O2
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
CO2 and O2
Water
Glucose
Location: Where
does it take place?
Light
Uses CO2; Produces
O2
Uses water
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
CO2 and O2
Water
Glucose
Location: Where
does it take place?
Light
Uses CO2; Produces
O2
Uses water
Produces glucose from
energy
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
CO2 and O2
Water
Uses CO2; Produces
O2
Uses water
Glucose
Produces glucose from
energy
Location: Where
does it take place?
Chloroplasts of green
plants, algae, and some
microorganisms
Light
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
CO2 and O2
Water
Uses CO2; Produces
O2
Uses water
Glucose
Produces glucose from
energy
Location: Where
does it take place?
Chloroplasts of green
plants, algae, and some
microorganisms
Light
Requires light
(light-dependent reaction;
Calvin Cycle can occur in
light or dark.)
Cellular Respiration Overview
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Transformation of chemical energy in food into
chemical energy cells can use: ATP
These reactions proceed the same way in plants
and animals. Process is called cellular
respiration
Overall Reaction:
–
C6H12O6 + 6O2 → 6CO2 + 6H2O
Cellular Respiration Overview


Breakdown of glucose begins in the cytoplasm:
the liquid matrix inside the cell
At this point life diverges into two forms and two
pathways
–
–
Anaerobic cellular respiration (aka fermentation)
Aerobic cellular respiration
C.R. Reactions

Glycolysis
–
–
–
–
Series of reactions which break the 6-carbon glucose
molecule down into two 3-carbon molecules called
pyruvate
Process is an ancient one-all organisms from simple
bacteria to humans perform it the same way
Yields 2 ATP molecules for every one glucose
molecule broken down
Yields 2 NADH per glucose molecule
Anaerobic Cellular Respiration

Some organisms thrive in environments with little or no
oxygen
–
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Marshes, bogs, gut of animals, sewage treatment ponds
No oxygen used= ‘an’aerobic
Results in no more ATP, final steps in these pathways
serve ONLY to regenerate NAD+ so it can return to pick
up more electrons and hydrogens in glycolysis.
End products such as ethanol and CO2 (single cell fungi
(yeast) in beer/bread) or lactic acid (muscle cells)
Aerobic Cellular Respiration
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
Oxygen required=aerobic
2 more sets of reactions which occur in a
specialized structure within the cell called the
mitochondria
–
–
1. Kreb’s Cycle
2. Electron Transport Chain
Kreb’s Cycle

Completes the breakdown of glucose
–
–

Takes the pyruvate (3-carbons) and breaks it down,
the carbon and oxygen atoms end up in CO2 and H2O
Hydrogens and electrons are stripped and loaded onto
NAD+ and FAD to produce NADH and FADH2
Production of only 2 more ATP but loads up
the coenzymes with H+ and electrons which
move to the 3rd stage
Electron Transport Chain
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Electron carriers loaded with electrons and
protons from the Kreb’s cycle move to this chainlike a series of steps (staircase).
As electrons drop down stairs, energy released
to form a total of 32-34 ATP
Oxygen waits at bottom of staircase, picks up
electrons and protons and in doing so becomes
water
Energy Tally
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
34-36 ATP for aerobic vs. 2 ATP for anaerobic
–
Glycolysis
2 ATP
–
Kreb’s
2 ATP
–
Electron Transport
32-34 ATP
36-38 ATP
Anaerobic organisms can’t be too energetic but
are important for global recycling of carbon
Photosynthesis vs.
Cellular Respiration

Comparing/Contrasting worksheet!
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
Energy is released
CO2 & O2
Water
Uses CO2; Produces
O2
Uses water
Glucose
Produces glucose from
energy
Location: Where
does it take place?
Chloroplasts of green
plants, algae, and some
microorganisms
Light
Requires light
(light-dependent reaction;
Calvin Cycle can occur in
light or dark.)
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
Energy is released
CO2 & O2
Water
Uses CO2; Produces
O2
Uses water
Glucose
Produces glucose from
energy
Location: Where
does it take place?
Chloroplasts of green
plants, algae, and some
microorganisms
Light
Requires light
(light-dependent reaction;
Calvin Cycle can occur in
light or dark.)
Uses O2;
Produces CO2
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
Energy is released
CO2 & O2
Water
Uses CO2; Produces
O2
Uses O2;
Produces CO2
Uses water
Produces Water
Glucose
Produces glucose from
energy
Location: Where
does it take place?
Chloroplasts of green
plants, algae, and some
microorganisms
Light
Requires light
(light-dependent reaction;
Calvin Cycle can occur in
light or dark.)
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
Energy is released
Uses CO2; Produces
O2
Uses O2;
Produces CO2
Uses water
Produces Water
Glucose
Produces glucose from
energy
Burns glucose from energy
Location: Where
does it take place?
Chloroplasts of green
plants, algae, and some
microorganisms
CO2 & O2
Water
Light
Requires light
(light-dependent reaction;
Calvin Cycle can occur in
light or dark.)
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
Energy is released
Uses CO2; Produces
O2
Uses O2;
Produces CO2
Uses water
Produces Water
Glucose
Produces glucose from
energy
Burns glucose from energy
Location: Where
does it take place?
Chloroplasts of green
plants, algae, and some
microorganisms
Glycolysis: Cytoplasm of
eukaryotic, prokaryotic cells
CO2 & O2
Water
Aerobic respiration:
mitochondria of ALL
eukaryotes
Light
Requires light
(light-dependent reaction;
Calvin Cycle can occur in
light or dark.)
ENERGY
Photosynthesis
Cellular Respiration
Photosynthesis
vs.
Cellular
Respiration
Energy is
stored
Energy is released
Uses CO2; Produces
O2
Uses O2;
Produces CO2
Uses water
Produces Water
Glucose
Produces glucose from
energy
Burns glucose from energy
Location: Where
does it take place?
Chloroplasts of green
plants, algae, and some
microorganisms
Glycolysis: Cytoplasm of
eukaryotic, prokaryotic cells
CO2 & O2
Water
Aerobic respiration:
mitochondria of ALL
eukaryotes
Light
Requires light
(light-dependent reaction;
Calvin Cycle can occur in
light or dark.)
Occurs in dark and light