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Photosynthesis and Cellular Respiration - Weebly · PDF file Hint –Reverse Photosynthesis Cellular Respiration is like photosynthesis in reverse sort of. The products become reactants

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  • Photosynthesis and

    Cellular Respiration

  • Outline

    I. Energy and Carbon Cycle

    II. Photosynthesis

    A. Introduction

    B. Reactions

    II. Cellular Respiration

    A. Introduction

    B. Reactions

  • Carbon Cycle

     All organisms require energy to maintain life

     The primary form of cellular energy is in ATP

    adenosine triphosphate

    adenosine diphosphate -- carrier

  • Carbon Cycle

     ATP is generated in a process called cellular


     Cellular respiration uses glucose molecules (a

    carbohydrate commonly called sugar)


  • Carbon Cycle

     Glucose is an organic compound, which means it

    contains carbon-hydrogen bonds

     Glucose must be made by organisms

     Organisms that make glucose are called

    autotrophs (auto = self; troph = feed)

     Autotroph means self-feeding, or an organism

    that can make its own food

     Autotrophs are called producers because they

    produce their own food

  • Carbon Cycle

     Producers create glucose in a process called


     Producers include plants, algae, and some

    bacteria and protists

     Once glucose is created, it can be used to make

    the ATP that supplies energy

  • Carbon Cycle

     Plants get the carbon they need to make glucose

    (C6H12O6) from carbon dioxide (CO2)

     This carbon is cycled through photosynthesis

    and cellular respiration through a perpetual

    process that reuses the carbon to create new


     Thus, it is called the Carbon Cycle – and is also

    known as the Energy Cycle

  • Carbon Cycle

  • Human Influence

     Human civilization has a very

    significant influence on the

    carbon cycle.

     Burning of fossil fuels (oil,

    coal, natural gas) releases

    CO2 into the atmosphere.

     CO2 is a greenhouse gas and

    traps heat in the atmosphere.

     This has a warming effect on

    the earth.

  • Human Influence

     Human activity began releasing CO2 into the atmosphere

    in unprecedented amounts starting with the Industrial


     In the last 150 years, the amount of CO2 in the

    atmosphere has increased by more than 30%.

     This is a major contributing factor to global warming.

     2014, 2015, 2016, 2017, and 2018 rank as the 5 warmest

    years (globally) on record.

     125,000 years ago was the last time the Earth was this

    warm. Sea levels were 18-27 feet higher at that time.

  •  The last time CO2 levels were this high was 3-5 million years ago

    during the warmest part of the Pliocene.

     Global temperatures were 3-4 C (5-7 F) higher and temperatures at

    the poles were 10 C (18 F) higher.

     Ice caps were small and sea levels were as much as 90 feet higher

    than today.

     There was a cooling trend toward the end of this epoch, but

    scientists are unclear what caused it.

  • Human Influence

     Impacts of human caused global warming:

    – Temperatures rise  glaciers melt  oceans warm  more

    glaciers melt  temperatures rise further

    – Sea levels rise

     New Orleans, Miami, Boston, L.A., and New York City are among

    the U.S. cities predicted to be underwater in the coming decades

    – Ocean currents disrupted

     Superstorms, hurricanes’ and

    blizzards become more common

    and more severe

    – Desertification

     Forests and grasslands

    become arid deserts

  • Photosynthesis

     Method of converting sun energy into chemical energy usable by cells

     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

     Photosynthesis takes place in specialized

    structures inside plant cells called chloroplasts

    – Light absorbing pigment molecules e.g. chlorophyll

  • Why Plants are Green

     Light is composed of photons

     Photon energy is measured in wavelengths

     Different wavelengths generate different colors of


  • What is Seen

     All wavelengths (colors) together appear as white light

     The white light can be separated into the visible spectrum

    – the rainbow…. ROYGBIV

     Other wavelengths are not visible to humans – Infrared

    (IR) and Ultraviolet (UV)

  • Why Plants are Green

     What is seen is what is reflected back

     All other detectable colors are absorbed

     Chloroplasts contain pigments

     The dominant pigment is chlorophyll, which absorbs red

    and blue while reflecting green and yellow

    The absorbed

    wavelengths provide

    the energy needed to

    power photosynthesis

  • Photosynthesis

     Most easily understood in two parts:

    1. Light dependent reactions

    – make the energy needed to connect carbons

    2. Light independent reactions

    – use the energy to connect the carbons

  • Chloroplast Structure

  • Overall Reaction

     6CO2 + 12 H2O + light energy → C6H12O6 + 6O2+ 6H2O

     Water appears on both sides because 12 H2O molecules

    are required and 6 new H2O molecules are made

     Important carrier molecules are used

    – ADP  ATP

    – NADP  NADPH

  • Light Dependent Reactions

     Three important components

    1. Harnesses sunlight

    2. Splits water

    3. Creates energy molecules

     Composed of two separate processes

    1. Photosystems – creates NADPH

    2. Chemiosmosis – creates ATP

     Both of these occur in the thylakoid membrane

     Both use peripheral and integral proteins

  • Splitting Water

     Water is split into H+, e-, and O2 – H+ and e- are used elsewhere

    – O2 is a waste product

  • Photosystems

    • Light energy is absorbed by

    chlorophyll molecules

    • Energy boosts e- to high energy


    • As the e- fall back down to low

    energy states, NADPH is created

    *The H+ and e- come

    from the split water

  • Chemiosmosis

     Photosystems also create H+

    concentration gradient

     H+ diffuses back through ATP

    synthase to create ATP

  • Light-dependent Reactions


  • Calvin Cycle (light independent or “dark” reactions)

     ATP and NADPH generated in light reactions

    used to fuel the reactions which take CO2 and

    break it apart, then reassemble the carbons into


     Called carbon fixation: taking carbon from an

    inorganic molecule (atmospheric CO2) and

    making an organic molecule out of it (glucose)

     Simplified version of how carbon and energy

    enter the food chain

  • Calvin Cycle

     Takes place in stroma

     Single C m-cules cycled through to

    create C3 m-cules

     C3 m-cules made into glucose later

  • Harvesting Chemical Energy

     Energy enters the food web via autotrophs when they convert light energy into chemical energy.

     All organisms use this chemical energy (glucose) to create energy molecules (ATP) that fuel their metabolism.

     Heterotrophs – unlike autotrophs they don’t create the fuel they use; they must consume it.

  • Cellular Respiration Overview

     Transformation of chemical energy in food

    (glucose and other macromolecules) into

    chemical energy cells can use: ATP

     These reactions proceed the same way in plants

    and animals – CELLULAR RESPIRATION

     Overall Reaction:

    C6H12O6 + 6O2 → 6CO2 + 6H2O

  • Hint – Reverse Photosynthesis

     Cellular Respiration is like photosynthesis in reverse…

    sort of.

     The products become reactants and the reactants the


    Just switch light energy for ATP

    And don’t get any dumb tattoos… it’s

    not that hard to remember.

  • Cellular Respiration Overview

     Breakdown of glucose begins in the cytoplasm --

    the liquid matrix inside the cell

     There are 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


    – Process is an ancient one-all organisms

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