Download Cell Energy: Photosynthesis and Respiration

Cell Energy: Photosynthesis
and Respiration
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Energy and Life
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Energy is the ability to
do work
– 
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All living organisms need
energy
Autotrophs – make their
own food
Heterotrophs – obtain
energy from food they
consume
Chemical Energy and ATP
•  Energy is stored as phosphate groups are added
to Adenosine
•  Adenosine Monophosphate (AMP)
•  Adenosine Diphosphate
(ADP)
•  Adenosine Triphosphate
(ATP)
•  Energy is released when bonds are broken
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continued
•  Adenosine Triphosphate or ATP
–  Composed of:
Adenine (base)
Ribose (5 C sugar)
3 Phosphate Groups
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Photosynthesis: An Overview
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Van Helmont – (1643) trees gain most of
their mass from water
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Priestly - (1771) plants release oxygen
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Ingenhousz – (1779) plants need sunlight
Photosynthesis continued
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Photosynthesis – is the
process in which plants
convert the energy of
sunlight into the energy
of chemical bonds of
carbohydrates
Photosynthesis continued
•  Requirements for photosynthesis:
6 CO2 + 6 H2O
Light
C6H12O6 + 6 O2
Sunlight- almost all organism depend on
energy from the sun
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Pigments – continued
•  Pigments–  Plants absorb light via
pigments in individual
cells
–  Pigments are colored
substances that
absorb or reflect light
–  Primary pigment of
green plants is
chlorophyll
•  Absorbs red and blue
•  Reflects green (and
other wavelengths such
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The Reactions of Photosynthesis
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Inside the chloroplast
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Thylakoid – sac-like
structure
Grana – stacks of thylakoid
In the thylakoid membrane
pigments are arranged in
clusters called photosystems
Stroma- region outside the
thylakoid membrane
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Electron Carriers –
– 
– 
– 
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Sun light excites electrons
in chlorophyll
e- gain energy and require
a special carrier
Something that can accept
a pair of high energy e-’s
NADP+
Will then become NADPH
and carry e- elsewhere in
the cell
Photosynthesis: The Light and Dark
Reactions
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Photosynthesis is divided into two reactions
– 
Light Reaction
Requires light (thylakoid)
l  Uses sunlight to make energy storing compounds
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– 
Dark Reaction
Does not require light (stroma)
l  Uses energy stored by light reaction to make glucose
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continued
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Photosynthesis occurs in the chloroplast
– 
Within the chloroplast are photosynthetic membrane
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– 
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Contain chlorophyll
Light Reactions take place in the photosynthetic membrane
Dark Reactions take place outside the membrane
Light Dependent Reaction page 210
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The energy of sunlight is absorbed and then
converted into the energy of chemical bonds
Light Reactions are broken down into four
basic parts
1. 
2. 
3. 
4. 
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Light Absorption
Electron Transport
Oxygen Production
ATP Formation
Light Absorption –continued
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Takes place in clusters of pigment molecules
within the photosynthetic membrane
(photosystems)
– 
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There are two types of photosystems
Photosystem I
and Photosystem II
l  Each photosystem contain several hundred chlorophyll
molecules and accessory pigments
l  Absorption of light causes electrons in pigments to
become “excited”
l  Energy is passed to specialized chlorophyll molecules in
the reaction center of the photosystem
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Electron Transport –continued
l 
High energy electrons are released from the reaction center and are
transferred along a series of electron carriers in the photosynthetic
membrane.
–  Electron carriers are known as the electron transport chain
–  At the end of the chain an enzyme passes electrons to NADP+
-converting it to NADPH (1st way energy trapped by chemical bonds)
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Oxygen Production –continued
Water is broken down
l  Electrons are taken
from water molecules
l  4 electrons are
removed from 2 water
molecules
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– 
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4 H+ and 2 O atoms
2 O atoms form O2
ATP Formation –continued
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When water decomposes
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Electrons are passed from
chlorophyll to NADP+
H+ are pumped across
membrane
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An enzyme use energy to
add a phosphate group to
ADP forming ATP
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Difference in charge
across membrane is a
source of energy
2nd way energy is trapped
in a chemical bond
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continued
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Summary
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– 
Light reactions use H2O, ADP, and NADP+
Light Reactions produce O2, ATP, and NADPH
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ATP and NADPH are energy storing compounds
Dark Reaction
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The dark reaction is known as the
Calvin Cycle
1. 
2. 
a 5 C sugar bonds with CO2 to form
two 3 C compounds
ATP and NADPH are used and the 3 C
compounds are converted to PGAL
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Most of the PGAL is recycled
1 out of 6 is used to make glucose or other molecules
Calvin cycle must go around twice to make 1 glucose
Intermediate compounds are produced
Dark reaction provides the raw materials to produce
almost everything the cells needs
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Glycolysis and Respiration
§  Respiration occurs in all living cells. It
involves breaking the chemical bonds in
organic food molecules and releasing
energy (ATP). The food molecules are
produced by plants during the process of
photosynthesis.
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Glycolysis –continued
§  Glycolysis is the first phase of respiration
§ 
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Occurs independent of oxygen (anaerobic)
is the breaking down of glucose into pyruvic acid
Occurs in the cytoplasm
2 ATP molecules needed to start reaction
4 ATP molecules are synthesized
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Aerobic Respiration –
continued
§  This process involves O2 in the
breakdown of food molecules to release
energy
§  Uses pyruvic acid
§  Captures most of the energy in glucose
§  34 ATP molecules
§  Occurs in both plants and animal
§  Takes place in the mitochondria
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Krebs Cycle –continued
§  1st step in aerobic respiration
1.  Pyruvic acid moves from the cytoplasm
into the mitochondria
§  Broken down into CO2 & 2C Compound
§  Coenzyme A combines with 2C Compound to
form acetyl-CoA
§  acetyl-CoA combines with 4C molecule to form
Citric Acid
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Krebs Cycle continued
§  9 intermediate reactions take place
§  More CO2 is released
§  NAD+ and FAD are converted to NADH and
FADH2
§  GDP converted to GTP to assist in making
ATP
§  Page 227, Fig 9-6
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continued- Electron
Transport and ATP Formation
§  Electron Transport
§  Oxygen is the final
electron receptor
§  It is needed to obtain
energy from NADH
and FADH2
§  Electrons, H+, and
Oxygen combine and
form water
§  ATP Formation
§  Similar to
photosynthesis, H+
are pumped through a
membrane
§  Movement of H+
powers ATP
formation
§  In total 36 ATP
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Electron Transport Chain
Electron Transport
Hydrogen Ion Movement
Channel
Mitochondrion
Intermembrane
Space
ATP synthase
Inner
Membrane
Matrix
ATP Production
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Fermentation
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Fermentation is an anaerobic process
Allows cells to produce energy in
absence of oxygen
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Fermentation continued
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Lactic Acid
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Pyruvic Acid
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Lactic Acid
Exercise
Yogurt
Sour Cream
Sourdough Bread
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Alcoholic
Pyruvic Acid
n  Yeast
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Alcohol + CO2
Carbon Dioxide = air
spaces in bread
Alcohol found in wine
and beer
Bubbles in
Champagne
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