Chapter 8 Photosynthesis Energy & Life

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Energy and Life Energy is the ability to do work Every activity depends on one kind of energy or another Chemical Solar Electrical

Chemical Energy Potential Energy Kinetic Energy of an Apple Falling down

Solar Energy

Electrical Energy

Energy of Life Plants and some other types organisms are able to use light energy from the sun to produce food

Autotrophs Are organisms that produce their own food, and consequently, their own energy (Plants)

Heterotrophs Are Organisms that have to obtain energy from food that they consume (Animals)

To Live, ALL Organisms must release the energy in sugars and other compounds

Chemical Energy and ATP Energy can come in many forms Light Heat Electricity Chemical

Cellular activities are powered by chemical energy ◦ Primarily ATP – Adenosine Triphosphate ▪ Nitrogen –Containing Compound Adenine ▪ 5 – Carbon Sugar Ribose ▪ 3 – Phosphate Groups

Production of ATP

ADP (Adenosine Diphosphate) is the same as ATP except it has 1 less phosphate group Cell stores energy by attaching a phosphate group to ADP to form ATP Cell releases energy by detaching a phosphate group from ATP to form ADP

The characteristics of ATP make it an exceptionally useful molecule that is used by all types of cells as their basic energy source

ATP powers the (Na+) \ (K+) pump in many membranes ◦ Also powers movement of organelles within the cell ◦ Moving along microtubles with motor proteins ◦ Motor proteins use energy from ATP to move organelles

ATP and Glucose Most cells have only enough ATP to last a few seconds ◦ ATP not a good molecule to store large amounts of energy ▪ A molecule of the sugar glucose stores as much energy as 90 molecules of ATP ▪ More efficient for cells to keep small supply of ATP and ADP on hand… regenerate supply as needed from carbohydrates like glucose

Photosynthesis ● When an organism uses light energy to convert water (H2O) and carbon dioxide (CO2) into oxygen (O2) and high-energy carbohydrates- sugars and starches ◦ Plants then use the sugars to make complex carbohydrates

Photosynthesis Equation 6 CO H 2 O → 6(CH 2 O) + 6 O 2

Van Helmont’s Experiment ◦ 1600’s ◦ Did experiment to see if plants grew by taking material from the soil ▪ He determined the mass of the dry soil and small seedling ▪ Watered it regularly ▪ Grew for 5 years ▪ Determined the mass of the small tree to be 75kg ▪ Mass of soil was unchanged

Van Helmont’s Experiment

▪ Concluded that the water was the only contributing factor “Hydrate” part of carbohydrate ▪ Could not account for the addition of carbon “Carbo” part of carbohydrate ▪ He did not realize that the carbon was being extracted from the air around the plant in the form of CO2

Priestly’s Expeiment 1700’s Took candle and lit it, placed it under a jar and observed that the flame went out after a while Concluded that something in the air was present to keep the flame burning and when it was used up, the flame went out That substance was Oxygen (O2)

Next, he placed a live sprig of mint under the jar for a few days The candle would relight for a while They produced O 2 Plants absorb CO 2 and release O 2

Later, Jan Ingenhousz that Priestly’s experiment only occur if the plant was exposed to sunlight Showed that light is necessary for plants to produce O2 These Experiments, along with others, showed that in the presence of light, plants transform CO2 and H2O into carbohydrates and release O2 These Experiments, along with others, showed that in the presence of light, plants transform CO2 and H2O into carbohydrates and release O2

Light and Pigment Photosynthesis also requires Chlorophyll, a molecule in chloroplasts Give them their green color Light is actually made up of many different wavelengths Different colors in the visible and invisible Spectrum Plants absorb sun’s energy with molecules known as pigments

Principal pigment in plants is chlorophyll 2 Types: ◦ Chlorophyll A ◦ Chlorophyll B Chlorophyll absorbs light well in the red and blue regions of the spectrum…not as well in the green part of the spectrum

This is why plants get their green color When light is absorbed by the chlorophyll Energy is transferred into electrons of chlorophyll molecule Raises energy level of the electrons These high energy electrons make photosynthesis work

The Reactions of Photosynthesis Thylakoids Thylakoids are sac-like photosynthetic membranes found inside a chloroplast ◦ Arranged in stacks known as granaum ChlorophyllProteins Photosystems ◦ Contain clusters of Chlorophyll and Proteins known as Photosystems that are able to capture the energy from sunlight ◦ Light dependant reactions

The StromaThylakoid The Stroma is the area outside the Thylakoid

Stroma Thylakoid The Stroma is the area outside the Thylakoid ◦ Calvin Cycle ◦ Light independent reactions

NADPH NADPH A carrier molecule is a compound that accepts a pair of high energy electrons and transfer them along with their energy to another molecule ◊ NADP+ is a carrier moleucle ◦ ◊ Accepts a 2 e- and a H+

Converts it to NADPH Converts it to NADPH This is a way that some of the Suns energy can be captured in chemical form NADPH e-’s NADPH then carries the high energy e-’s all over the cell to build a variety of molecules …Carbohydrates like glucose