Transcript Photosynthesis & Respiration

Food for thought…
1. What goes in
and where does
it enter?
2. What comes out?
3. Where does the
matter in the tree
come from?
Answers: Plants make their food!
• 1. CO2 enters a plant through pores in
leaves; Water enters through the roots;
Sunlight is absorbed by structures in the
leaves.
• 2. Oxygen is released through pores in
the leaves.
• 3. The matter comes from atoms in the
Carbon dioxide and water!
Where does the cow get mass and
energy?
4. What goes in?
5. What comes out?
Answers:
• 4. Food (including Glucose) and
Oxygen
• 5. Carbon Dioxide and Water
How do plants get organic
molecules and energy?
• They make them!
• Using the energy in sunlight, plants
convert the inorganic Carbon in CO2 to
simple sugars (organic molecules) and
oxygen (O2).
• This process is called Photosynthesis.
Is making sugars by
photosynthesis all a plant needs?
• NO
• The plant ALSO releases the chemical
energy stored in the sugars to grow (as do
all animals!).
• This 2nd process is called CELLULAR
RESPIRATION.
How do animals get organic
molecules and energy?
• We cannot convert inorganic Carbon
(CO2) to organic molecules.
• We consume Food!
• Like plants, we convert the chemical
energy in food to a form the cell can use
by CELLULAR RESPIRATION.
Photosynthesis and Cellular Respiration
provide Organic molecules AND
Energy for ALL life
• Energy is necessary for ALL life processes
– These include growth, transport, manufacture,
movement, reproduction, and others
– Energy that supports life on Earth comes from
sun’s light energy captured and transformed by
plants!
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What is Photosynthesis?
The process of photosynthesis is a
series of chemical reactions.
It is the most important chemical
process on our planet!!
Why is Photosynthesis important?
• It is the key process on Earth that
transforms light energy to
chemical energy that is stored in
the bonds of organic sugars (like
GLUCOSE)
• It is the main way energy is
introduced into life on Earth!
Who does it?
Plants, algae & some bacteria & protists
Photosynthesis
Use Light
To synthesize
i.e., MAKE
Food
Plants = Autotrophs
Self
Food
• Autotrophs make their own food without
using organic molecules from other organisms
– Photoautotrophs - use light energy to make
organic “food” molecules
– Examples:
– Plants, algae, some bacteria, some protists
– CRITICAL to all Ecosystems as Producers
of the Biosphere!
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Plant Power
– Earth’s plants produce 160 billion metric tons of
sugar each year through photosynthesis, a
process that converts solar energy to chemical
energy
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What is the SUMMARY equation for the
chemical reaction of photosynthesis?
Sunlight (ENERGY!)
6CO2+6H2O
C6H12O6 + 6O2
Glucose!
Summary questions:
1. Where does the plants organic mass come
from?
2. Where does the energy come from to make
the organic molecules?
3. What do we call the above process?
4. What process converts the energy in the
sugars to a form that plants and animals can
use?
What is the SUMMARY equation for the
chemical reaction of photosynthesis?
Sunlight (ENERGY!)
6CO2+6H2O
C6H12O6 + 6O2
Glucose!
A Disclaimer……
• Actually, Photosynthesis does NOT
directly produce glucose- it produces
simple 3 Carbon sugars that can be
joined to form glucose.
It is typically written this way because it
flows better with Cellular Respiration……
Where does Photosynthesis happen?
• Mostly in leaf cells
Photosynthesis in Chloroplasts!
• What are Chloroplasts?
• organelles that consist of
photosynthetic pigments, enzymes,
and other molecules grouped together
in membranes
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Chloroplast: Structure = Function
• Thylakoids location of light
absorbing pigments
• CHLOROPHYLL, a
key light absorbing
pigment, plays a BIG
role in photosynthesis
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Gives plants their
GREEN color.
Thyme-moss cells
Break it down: 2 Stages
to Photosynthesis
• Photosynthesis occurs in two linked
metabolic stages
– Stage 1: The Light Reactions
– Stage 2: The Calvin Cycle
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Each reactant
is important
for a different
cycle.
SNEAK
PREVIEW
Stage 1: The Light Reactions
– Main purpose:
– Convert light energy to chemical energy
– Where it occurs:
– Thylakoid membrane (in granum)
– What happens (part of the rxn):
– H2O and SUNLIGHT come in.
– H2O is split (need that H!) – leftover
oxygen is released.
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Absorption of VISIBLE light
DRIVES the Light Reactions
• Sunlight = ENERGY called electromagnetic
radiation (ER)
– Visible light (ROY G BIV) is only a small part
– Travels in waves w/different lengths.
• Light behaves as discrete packets of energy
called PHOTONS
SHORT wavelength = HIGH energy
LONG wavelength = LOW energy
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Increasing energy
10–5 nm 10–3 nm
Gamma
rays
X-rays
103 nm
1 nm
UV
106 nm
Infrared
103 m
1m
Microwaves
Radio
waves
Visible light
380 400
600
500
Wavelength (nm)
700
650
nm
750
Stage 1: The Light Reactions, cont.
• Pigments = molecules that ABSORB light
• Found in the Thylakoid membrane
• ABSORB some wavelengths of light and
reflect (aka TRANSMIT) others
*We SEE the color that is
TRANSMITTED.
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Light
Reflected
light
Chloroplast
Absorbed
light
Thylakoid
Transmitted
light
Visible radiation drives the light reactions
PIGMENT
ABSORBS
TRANSMITS
Chlorophyll a
blue violet;
red
green
Chlorophyll b blue; orange
yellowgreen
Carotenoids
yellow;
orange
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blue-green
Photosystems capture Visible Light Energy!
• Pigments absorb photons of light –
release e• 1) e- jump to higher energy level =
excited state (unstable)
• 2) e- electrons drop back to a stable
ground state, emitting the energy
Excited state
e–
Heat
Photon
Photon
(fluorescence)
Ground state
Chlorophyll
molecule
Photosystems capture solar power and
transform it to chemical Energy
• The energy released from the e- is passed
from one pigment molecule to another
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Step 1: Light Reactions, cont.
• The harvested light energy is
transformed into the chemical
energy of ATP and NADPH by
the 2 Photosystems
(Photosystem I & PhotosystemII)
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• Eventually, the energy is
passed to the Reaction
center that is able to
DONATE a high energy
ELECTRON!
Chemical Energy: NADPH & ATP
• Electrons from split H2O are passed through two
photosystems (II and I) and are accepted by NADP+
NADP+
Photosystem II
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Photosystem I
NADPH
Chemical Energy: NADPH & ATP
• Between photosystems is an e- transport chain that
provides energy to make ATP
NADP+
e- Transport Chain
Photosystem II
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Photosystem I
NADPH
ATP!!!
Chemical Energy: NADPH & ATP
• NADPH and ATP are used for Stage 2: The Calvin
Cycle
CALVIN
CYCLE
NADP+
e- Transport Chain
Photosystem II
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Photosystem I
NADPH
ATP!!!
Stage 2: The Calvin Cycle
– Main purpose:
– Use energy from light reactions to
construct Sugars!
– Where it occurs:
– Stroma of chloroplast
– What happens:
– CO2, ATP & NADPH come in.
– Glucose is synthesized & exits
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Stage 2: The Calvin Cycle
• Occurs outside the Thylakoids, in
the chloroplast Stroma (fluid).
Chloroplast
Stage 2: The Calvin Cycle, cont.
• A cyclic series of reactions
• Uses the energy from the light
reactions to build sugar
molecules (organic molecules)
from CO2 (inorganic carbon)
• Process called Carbon Fixation
Calvin Cycle, cont.
– Where does the energy to build the
sugar come from?
– ATP and NADPH (from the light
reactions) provide the chemical
energy
– The Calvin cycle is sometimes called
the dark (or light-independent)
reactions
CO2
H2O
Chloroplast
Light
NADP+
ADP
P
LIGHT
REACTIONS
CALVIN
CYCLE
(in stroma)
(in thylakoids)
ATP
NADPH
O2
Sugar
Don’t worry about
the details
Photosynthesis – The fate of sugar!
• Conundrum: leaves are mostly responsible for
photosynthesis, but the entire plant needs
energy!
• Sugars move through tubes in the leaf to the
roots, stems, fruits etc
• Some sugar used immediately by cellular
respiration!
• Some stored as starch
• Some built into plant tissue
Why Photosynthesis is essential to life
on Earth:
• The energy that was in sunlight was
transformed into chemical energy in
sugars by photosynthesis!!
• CO2 has been converted to organic
carbon in MATTER that all organisms
can use as a source of Carbon!
• Oxygen is produced and released to
the atmosphere
Light
Reactions
Where?
Reactants
Products
Purpose of
Reaction
Calvin Cycle
Photosynthesis
Where does it
occur?(organelle)
Why is it
important?
What is the
Substrate?
Products?
What is the
formula?
Who does it?
(Plant, Animal)
Respiration