Chapter 8 Cellular Energy *Photosynthesis *Cellular Respiration Cellular Energy Cellular Energy.

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  • Chapter 8Cellular Energy*Photosynthesis*Cellular Respiration

  • ENERGY - is the ability to do work

    ALL ORGANISMS need and use energy!!!!

  • Where do organisms get the energy that they need?

    it comes from food, however, the ultimate source of most of our energy is the SUN

  • Law of Thermodynamics

    Energy cannot be created or destroyed, but it can be converted into other forms

  • MetabolismThe sum of a cells chemical reactionsMetabolism = Catabolism + AnabolismCatabolism: to break down Ex: cellular respirationAnabolism: to build up Ex: photosynthesis*This results in a continuous flow of energy within an organism.

  • organisms meet their energy needs in different ways

    AUTOTROPHS plants, some bacteria & protistsproduce their own food chemoautotrophs go through chemosynthesisphotoautotrophs go through photosynthesis HETEROTROPHS fungi, animals, some bacteria & protists cannot produce their own foodmust obtain energy from the foods they consume

  • ENERGYenergy comes in many forms light, heat, electricity, nuclear, kinetic,

    Some organisms consume foods in order to get the stored energy out of them

  • ATPcellular activities require the use of energyone of the main chemical compounds that cells use to store energy is ATP (adenosine triphosphate)

    ATP consists of :1. a N-containing part called adenine2. a 5-Carbon sugar - called ribose3. three phosphate groups (P and O)

  • Metabolic Pathway of ATP and ADPform a cycle of releasing and absorbing energy

    ATPADPreleases Energyrequires (absorbs) energy

  • ATP and Glucosemost cells have only a small amount of ATP (enough to last for a few seconds of activity)

    more is made as needed by using the stored energy (glycogen)

  • 2 processes of great importance that enable living things to meet their energy needs

    1. PHOTOSYNTHESIS the production of organic compounds

    2. CELLULAR RESPIRATION the break down of organic compounds



    ATP- ADP CYCLELight Energy

    Chemical Energy (organic compounds)


    ADPs + P groups + energy (that can be used to do cellular activities)

  • Photosynthesis process by which a cell captures light energy (photons) and uses it to make food (usually carbohydrates, like glucose)

    photosynthesis occurs in photoautotrophs:plantsalgae some bacteria (prokaryotes)

  • PHOTOSYNTHESIS - process in which water, carbon dioxide, and light energy are converted into oxygen and organic compounds

    the ORGANIC COMPOUNDS made during photosynthesis are usually carbohydrates (sugars and starches)

  • PHOTOSYNTHESIS general equation

    6 CO2 + 6 H2O + light (energy) C6H12O6 + 6 O2

    What are the reactants?What are the products? Where does the light energy come from?Where does the H2O come from?Where does the CO2 come from?

  • Photosynthesis - Overview

  • most photosynthetic organisms are eukaryotes, therefore, photosynthesis occurs inside the CHLOROPLAST

    prokaryotes lack chloroplasts, in these organisms, photosynthesis occurs in the cytoplasm


    ALL photosynthetic organisms contain PIGMENTS (light absorbing substances)

    the principal photosynthetic pigment is (green) CHLOROPHYLL

    in addition to chlorophyll there are other pigments called ACCESSORY PIGMENTS (ex. Carotenoids)

  • Chloroplast Structure

    chloroplasts contain disc like structures calledTHYLAKOID DISKS

    these are arranged in stacks called GRANA

    PIGMENTS are found inside the thylakoid disks

    a fluid called STROMA surrounds the thylakoid disks


    What do the names indicate about these reactions?

  • Light Dependent Reactions(occur in thylakoid disk containing chlorophyll)

    Light Independent Reactions (occur in stroma)

  • Light dependent reaction:What are the reactants? products?Light independent reaction (Calvin Cycle)?What are the reactants? products?

  • Alternative PathwaysUsed when water and/or carbon dioxide are not present or in insufficient amounts2 types:The C4 pathway Sugar cane, cornThe CAM pathwayPineapple, cacti, orchids

  • Factors Affecting Photosynthesisavailability of wateravailability of carbon dioxidetemperaturelight intensity

  • Biochemical (Metabolic) Pathway



    ATP- ADP CYCLE Light Energy

    Chemical Energy (organic compounds)


    ADPs + P groups + energy (that can be used to do cellular activities)

  • Cellular Respiration process that releases energy (in the form of ATPs) from food (organic compounds)

    All living things undergo some form of cellular respiration, but remember living things differ so this process may differ

  • There are 2 possible ways in which a cell can accomplish cellular respiration and harvest energy from food.

    (aerobic) Cellular Respiration = oxidative respirationorFermentation (anaerobic respiration)

    *both start with the same first stepGLYCOLYSIS

  • (aerobic) Cellular Respiration or Oxidative Respiration

    releases energy (in the form of ATPs) from food (organic compounds)

    ~in the presence of oxygen~

  • 3 steps of (aerobic) Cellular Respiration

    1. Glycolysis2. Krebs Cycle 3. Electron Transport Chain

  • 1. Glycolysis

    occurs in the cytoplasmanaerobic splitting of glucose into pyruvic acid (pyruvate) net gain of 2 ATP and 2 pyruvate

  • 2. Krebs Cycle

    occurs in mitochondrion (of eukaryotes) aerobic breaks down pyruvic acidproduces CO2 and a net gain of 2 ATP

  • 3. Electron Transport Chain

    occurs in mitochondria(of eukaryotes) aerobic uses electrons to release energy and produce ATPproduces H2O and up to 34 ATP

  • How many ATPs from (aerobic) Cellular Respiration?

    Glycolysis (2)Krebs Cycle (2)Electron Transport Chain (maximum 34) possible 38 ATPs

    the actual number of ATPs varies from cell to cellmost eukaryotic cells produce 36 ATPs

  • General Equation for (aerobic) Cellular Respiration C6H12O6 + 6O2 6CO2 + 6H2O + ATP (energy)

    What are the reactants?What are the products?

  • if no oxygen is present.. glycolysis is followed by fermentation

    Fermentation (anaerobic respiration) releases energy (in the form of ATP) from food (organic compounds)

    ~in the absence of oxygen~

  • 2 steps of Fermentation (anaerobic respiration)1. Glycolysis2. Fermentation

  • 1. Glycolysisoccurs in the cytoplasmanaerobic splitting of glucose into pyruvic acid (pyruvate) net gain of 2 ATP and 2 pyruvate

  • 2. Fermentationoccurs in the cytoplasmanaerobic the break down of pyruvic acid in the absence of oxygennet gain of 0 ATP

  • How many ATPs from FERMENTATION?Glycolysis (2)Fermentation (0) possible 2 ATP

    * fermentation is not nearly as efficient in releasing energy from food as is (aerobic) Cellular Respiration

  • 2 common types of FermentationLACTIC ACID FERMENTATIONconverts pyruvic acid into lactic acidprocess used to make yogurt, cheese, sour creamoccurs in some fungi and some bacteria occurs in skeletal muscle cells of animals = lactic acid or sore muscles

  • 2 common types of FermentationALCOHOLIC FERMENTATIONconverts pyruvic acid into ethanol (ethyl alcohol)process used in the making of bread and alcoholic beverages - wine, beer,occurs in yeasts, some bacteria, some plantsethanol is added to gasoline to make gasohol

  • Visualizing Cellular Respiration

  • Lets see the process again

  • Photosynthesis and Cellular Respiration are a metabolic (biochemical) pathways


  • The products of photosynthesis are used as the reactants in cellular respirationThe products of cellular respiration are used as the reactants in photosynthesis

  • Cellular Respiration Virtual Lab


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