Energy and Life. Energy = the ability to do work –Life on earth depends on a flow of energy –Cells need energy constantly to continue functioning.

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  • Energy and Life

  • Energy = the ability to do work

    Life on earth depends on a flow of energy

    Cells need energy constantly to continue functioning.

  • Energy comes in many forms

    Examples:LightHeatEnergy stored in chemical compounds (like glucose)

  • Most cellular processes require the input of energy.

    Like what?

  • Examples:Synthesis of new molecules proteins, enzymes, DNA etc.

    Breakdown of molecules chemical digestion

    Build new structures membranes, organelles, etc.

    Maintain Homeostasis eliminate wastes, maintain body temp., active transport, cell movement etc.

  • Where do cells get this energy?

    From food we eat

    We measure the energy content of food in calories.

    Certain reactions break down these molecules to release energy.

  • Energy released from a Gummy Bear

  • Cant use energy directly from food

    Need to store it and release it gradually.

    Store it in molecules of ATP.

  • ATP (Adenosine Triphosphate)Source of cellular energy

    Stores energy as food is broken down so that it can be released slowly to cell when needed rather than all at once.

    A type of energy currency, that can be paid out as the cell needs it.

  • Structure of ATP (Adenosine triphosphate)1 adenine (type of nitrogenous base)1 ribose sugar (5 carbon ring)3 phosphate groups

  • How is ATP Formed?

    Energy is stored in high energy phosphate bonds

  • Cells bond a third phosphate group to ADP

    ADP (adenosine diphosphate)

  • To release this energy again, the cell breaks off the 3rd phosphate group and energy is released.

    Can happen over and over again.

    Like recharging a battery!

  • IMPORTANT TO KNOW!!How does ADP and ATP differ?

    How is this related to energy?

  • Storing EnergyAdd a phosphate to ADP

    ADP + phosphate + energy ATP

  • Releasing EnergyRemove a phosphate from ATP

    ATP ADP + phosphate + energy

    Note: The enzyme that catalyzes this reaction is called ATPase.

  • Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose.

  • ATP/ADP Cycle

  • How do organisms obtain food to make ATP?

  • They eat it

    Heterotrophs: obtain food from consuming other living things.

    Ex: Animals: herbivores, carnivores and omnivoresFungiSome protistsSome bacteria

  • They make it themselves

    Autotrophs: use light energy from the sun to make their own food through photosynthesis.

    Ex: PlantsAlgaeSome bacteria

  • PhotosynthesisProcess by which light energy is converted into the chemical energy of organic compounds (glucose).

  • Occurs in the chloroplasts of plant cells (as wells as some single celled organisms, that can carry out photosynthesis.)

  • Chloroplast StructureStroma: protein containing fluid

    Grana: stacked membranes containing enzymes and chlorophyll.

  • Chlorophyll: green pigment necessary for photosynthesis.

    Absorbs red and blue wavelengths of light and reflects green light. (thats why most plants look green)

  • Note: Other photosynthetic pigments exist besides chlorophyll, but it is the main one used by autotrophs Ex: Carotenoids (orange/red colored pigment)

  • Equation for Photosynthesis

  • Photosynthesis OverviewPlants Take In:Carbon Dioxide GasWaterSunlight (energy)

    Plants Produce:Glucose (form of stored energy)Oxygen Gas

  • The Process of PhotosynthesisHow Does the Chloroplast Work?Light Dependant Reactions (Photochemical)Light Independent Reactions (Carbon Fixation)

  • Light ReactionsLight Dependant Reactions (Photochemical)Happen in the thylakoid membranes of granaDirectly involve chlorophyll and sunlight

    Produces oxygenConverts ADP to ATPConverts NADP+ to NADPH

  • Chlorophyll absorbs sunlightCreates high energy electronsElectrons enter the electron transport chainEventually produce some ATP

  • PhotolysisWater gets split inside grana

    Breaks into:One oxygen atomTwo H+ ions2 electrons

  • The Oxygen produced by splitting water gets released into the air

    Source of nearly all the oxygen in Earths atomosphere!

    Thank you plants!!! You make our lives possible.

  • The H+ ions and electrons

    Join up with NADP+ an electron carrier

    It becomes NADPH

  • Making ATP

    H+ ions build up and cross the thylakoid membrane causing ATP to form as ATP synthase (an enzyme) turns ADP into ATP

  • Dark ReactionsLight Independent Reactions (Calvin Cycle)Does not require lightHappens in stroma

    Carbon Fixation: Carbon gets Fixed from a simple 1 carbon molecule (CO2) to a complex 6 carbon one that holds stored energy (glucose/C6H12O6)

  • Carbon Dioxide Molecules: (CO2) enters from atmosphere (through stomata)

    Combine to make PGAL a 3-carbon molecule2 PGAL combine to produce a 6-carbon glucose

    Energy for these reactions to take place is provided by ATP and NADPH (from light reactions)

  • Photosynthesis Summary

  • Light vs. Dark Reactions

  • Video Overview of Photosynthesis (5min)

  • Factors Affecting Photosynthesis

    TemperatureLight IntensityWater and Carbon Dioxide Availability Tutor Vista:

  • Temperature: Enzymes are needed for photosynthesisFunction best between 0C and 35C.Too hot or too cold and photosynthesis stops

  • Intensity of Light:More intensity = more photosynthesisRemember blue and red wavelengths are most useful for photosynthesis

  • Availability of Water and CO2:One of the raw materials for photosynthesisSplit during photolysis reaction

    Water loss can kill plantsThey have evolved strategies Waxy coatings on leaves

  • Stomata: small openings in plant leaves that normally admit carbon dioxideWater can also escape through opening

    Guard Cells:Can open or close stomata to help prevent excess water loss from plant

  • Stomata and Guard Cells Video:


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