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.
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 Bearhttp://www.youtube.com/watch?v=uj9D3mc7tVg&feature=related&safe=active
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.
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
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)
Light vs. Dark Reactions
Video Overview of Photosynthesis (5min)http://www.youtube.com/watch?v=mYbMPwmwx88&safe=active
Factors Affecting Photosynthesis
TemperatureLight IntensityWater and Carbon Dioxide Availability Tutor Vista:http://www.youtube.com/watch?v=vmmWiJ3g9Cg&safe=active
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:http://www.youtube.com/watch?v=cFX4JrsPaUs&safe=active