Photosynthesis and
Cellular Respiration
Outline
I. Metabolism
A. Catabolic pathway
B. Anabolic pathway
II. Photosynthesis
A. Introduction
B. Reactions
III. Cellular Respiration
A. Introduction
B. Reactions
Metabolism


Sum of all the chemical processes that occur in
the body.
Two types of metabolic pathways
Catabolic and Anabolic
Two Metabolic Pathways
1. Catabolic
 Breaks down
molecules
 Large Molecules to
small molecules
 Release energy
Examples:
Cellular Respiration and
Hydrolysis
2. Anabolic
 Build large
molecules
 Small molecules to
large molecules
 Store Energy
Examples:
Photosynthesis and
Dehydration synthesis
Anabolic vs. Catabolic
Photosynthesis
 Anabolic Pathway
 Build molecule of Glucose
 Energy is stored in
chemical bonds
 Light energy from sun is
transferred into chemical
energy for the cell.
Cellular Respiration
 Catabolic Pathway
 Breakdown Glucose
molecule
 Energy is released
 Organic molecules are
broken down to release
energy
Energy Transfer
Photosynthesis
6CO2 +
12 H2O + light energy → C6H12O6 + 6O2+ 6H2O
Cellular Respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O

Products of Photosynthesis are the reactants of
Cellular Respiration.
Autotrophs
Autotrophs: self feeders, organisms capable of
making their own food
–
–
Photoautotrophs: use sun energy e.g. plants
photosynthesis-makes organic compounds (glucose)
from light
Chemoautotrophs: use chemical energy e.g.
bacteria that use sulfide or methane
chemosynthesis-makes organic compounds from
chemical energy contained in sulfide or methane
Photosynthesis-Location

Photosynthesis takes place in specialized
structures inside plant cells called chloroplasts
–
Light absorbing pigment molecules e.g. chlorophyll
Inside A Chloroplast
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Chloroplast Structure
Double membrane organelle:
Outer Membrane- Smooth
Inner membraneforms stacks of connected sacs called
thylakoids
-Thylakoid stack is called the granum
(grana-plural)
-Gel-like material around grana called
stroma
Function of the Stroma
Light Independent reactions occur here
 ATP used to make carbohydrates like
glucose
 Location of the Calvin Cycle
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Function of the Thylakoid
Membranes
Light Dependent reactions occur
here
 Photosystems are made up of
clusters of chlorophyll molecules

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Pigments
Found in thylakoids
 Absorb different wavelengths of light
 Where light dependent reaction occurs
 Chlorophyll A and Chlorophyll B are main
pigments. They absorb violet/blue spectrum
 Carotenoids- another type of pigment, absorb the
blue/green spectrum
Photosynthesis Overview
6CO2 + 12 H2O + light energy → C6H12O6 + 6O2+ 6H2O
Method
of converting sun energy into chemical
energy usable by cells
Product
is glucose (carbohydrate)
Water is split releasing O2 as a byproduct
Consists of two phases:
Phase 1- Light Dependent reaction
Phase 2- Calvin Cycle (Light Independent reaction)
Phase 1-Light Dependent Reaction
Location: Thylakoids
Reactants: H20 and Light
Products: ATP and NADPH (energy storing
molecules)
Consists of two processes
1.) Electron Transport-produced NADPH
2.) Chemiosmosis- produces ATP
Light-dependent Reactions

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Photosystem: light capturing unit, contains chlorophyll,
the light capturing pigment (in thylakoids)
Electron transport system: sequence of electron
carrier molecules that shuttle electrons, creates NADPH
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)
Light Dependent Reaction
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Phase II-Calvin Cycle
(Light Independent reaction)
Location: Stroma
Reactants: CO2, ATP and NADPH
Products: Glucose
Light Independent Reaction
 ATP
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& NADPH from light reactions
used as energy
 Atmospheric C02 is used to make
sugars like glucose and fructose
 Six-carbon Sugars made during the
Calvin Cycle
 Occurs in the stroma
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The Calvin Cycle
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The Calvin Cycle
Two turns of the Calvin Cycle are
required to make one molecule of
glucose
 3-CO2 molecules enter the cycle to
form several intermediate compounds
(PGA)
 A 3-carbon molecule called Ribulose
Biphosphate (RuBP) is used to
regenerate the Calvin cycle
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