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Photosynthesis - light

Page history last edited by Charles Forstbauer 14 years, 4 months ago

Totaled and closed 11/12 Mr F

 

http://www.youtube.com/watch?v=Idy2XAlZIVA

Totaled 11/09 Mr F 

Totaled 11/06 Mr F

Page restored. I repeat -if you make a mistake FIX IT! Use the page history and restore to the page BEFORE it got messed up. At the very least - put a notice on the page to let people know it is messed up so they don't add to it.

Dani, Jeff your edits are gone please put them back in.

 

Totaled 11/03 Mr F

Totaled 10/29  Mr F

 

Chapter 8 Notes: “Photosynthesis” (pages 200-219)

 

8-1: Energy and Life

 

1)      Autotrophs and Heterotrophs

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

b)      autotrophs- organisms that make their own food (ex. plants)

c)      heterotrophs- organisms that cannot use the sun’s energy directly and obtain energy from the foods they consume (ex. grasses, eating animal that eat autotrophs, or even decomposing other organisms)

d)      Autotrophs use light energy from the sun to produce food

 

Autotrophs versus Heterotrophs

    In the haploid bread-mold Neurospora, wild-type autotrophs are able to grow either on complete medium containing a variety of amino acids, or minimal medium containing only basic CHNOPS salts (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur). After exposure to X-rays, a series of mutant heterotrophs are obtained that are able to grow only on complete medium: something has affected their ability to synthesize amino acids. "Growth" and "No Growth" on minimal medium are alternative phenotypes.

 

 

2)      Chemical Energy and ATP

     Energy comes in many forms, including light, heat, and electricity.

a)      adenosine triphosphate- a chemical compound that living things use to store energy (ATP)

b)      ATP is used by all types of cells as their basic energy source

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

 

 ATP, a nucleotide has ribose sugar, phosphate and an adenine base

 

Cells use the energy provided by ATP in a number of ways:

     a) Active Transport: Many cell membranes contain a sodium-potassium pump that moves sodium ions out of the cell and potassium ions into it.

     b) ATP powers movement within the cell: Cell organelles are moved along microtubules by motor proteins that use the engergy of ATP to generate force

 

 

8-2: Photosynthesis: An Overview

 

1)      photosynthesis- plants use the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy carbohydrates; sugars and starches

 

2)      Investigating Photosynthesis

a)      Many scientists have contributed to understanding how plants carry out photosynthesis. Early research focused on the overall process. Later researchers investigated the detailed chemical pathways.

b)      Jan van Helmont (1643)- After careful measurements of a plant’s water intake and weight increase, van Helmont concludes that trees gain most of their mass from water

c)      Joseph Priestley (1771) - Using a bell jar, a candle, and a plant, Priestley finds that the plant releases a substance that keeps the candle burning- a substance that we now know as oxygen.

d)      Jan Ingenhousz (1779) - Ingenhousz finds that aquatic plants produce oxygen bubbles in the light but not in the dark. He concludes that plants need sunlight to produce oxygen.

e)      The experiments performed by van Helmont, Priestley, Ingenhousz, and other scientists reveal that in the presence of light, plants transform carbon dioxide and water into carbohydrates and release oxygen

f)        Photosynthesis is a series of reactions that uses energy from the sun to convert water and carbon dioxide into sugars and oxygen

g) Begins when pigments in photosystem II absorb light (called #2 because it was discovered after #1)

 

 

3)      The Photosynthesis Equation

a)      Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high energy sugars

b)      6CO2 + 6H2O    light     C6H12O6 + 6O2

 

 

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I found this video to be extremely helpful in understanding the relationship between the light and dark reactions.  In addition, it is a clever song with a clever song, and has rhymes to help remember tricky concepts.

 

Here is a visual picture to go with the equation for photosynthesis above. This picture very clearly shows how everything from the equation fits into the real reaction.

 

4)      Light and Pigments

a)      In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll, a molecule in chloroplasts

b)      pigments- light-absorbing colored molecules (plants gather the suns energy through pigments, the plants principle pigment is chlorophyll)

c)      chlorophyll- a plant’s main pigment

d)      Photosynthesis requires light and chlorophyll, which absorbs light energy

 

8-3: The Reactions of Photosynthesis

 

 

1)      Inside a Chloroplast

 

 

 *There are two stages in photosynthesis involving chloroplast- 1 is light-dependent (takes place inside the thylakoid), 2- independent reactions takes place in the stroma) ( (Calvin Cycle)

      a)      thylakoids- saclike photosynthetic membranes in chloroplasts (arranged in stacks) that contain clusters of chlorophyll and other pigments and proteins known as photosystems that can capture the energy of sunlight.

b)      stroma- region outside the thylakoid membranes where Calvin cycle takes place

c)    granmum- a whole stack of thylakoids, like a stack of quarters

d)    inner&outer membrane- phospholipid bilayer outside the chloroplast

e) phtosystems- Clusters of pigment and protein that absorb light energy (found in the thylakoid)

 

http://en.wikivisual.com/images/1/11/Chloroplast-new.jpg

 

 

2)      NADPH

a)      NADP+- (nicotinamide adenine dinucleotide phosphate) one of the carrier molecules that transfers high-energy electrons from chlorophyll to other molecules. These high energy electrons are used to help build a variety of molecules the cell needs, including carbohydrates like glucose.

 

3)      Light-Dependent Reactions

a)      light-dependent reactions- require light, therefore plants need light to grow.

b)      The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH

c)      ATP synthase- protein in the membrane that allows H+ ions to pass through it

 

 

 

*STEPS: 1. Energy is absorbed from the light by electrons, increasing their energy level (electrons are then passed down through the electron transportation chain) 2. The electrons move through the electron transport chairn from photosystem II to photosystem I. Electron energy is used by the molecules in the tectron transport chain to transport H+ ions from the stroma to the thylakoid. 3. Pigments from photosystem I use energy from light to reorganize the electrons. NADP+ then picks up these electrons at the thylakoid membrane (along with H+ ions) and become NADPH. 4. Due to the process in step 3, the thylakoid membrane becomes positivly charged, contrasting the other charges accrross the membrane, creating ATP. 5. H+ ions pass through the membrane using ATP synthesis.

 

 

 

 

4)      The Calvin Cycle

a)      Calvin cycle- plants use the energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time

b)      The Calvin cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars

c)    Because the cycle does not require light, these reactions are called the light independent reactions.

d) Named after the American scientis Melvin Calvin

 

 

*STEPS: 1. 6 CO2 molecules enter the cycle. The CO2 molecules combine with six 5-carbon molecules, creating tweleve 3-carbon molecules. 2. The twelve 3-carbon melecules are then changed into higher-energy forms coming from ATP and NADPH electrons. 3. Two of the twelve 3-carbon molecules are converted intow other 3-carbon molecules that are used to form 6-carbon sugars and other compounds. 4.The last ten 3-carbon molecules are changed back into six 5-carbon molecules. These molecules combine with six new CO2 molecules to begin the next cycle.

http://www.biologycorner.com/resources/photosynthesis-overview.gif

 

 

 

 

 

 

During photosynthesis, light energy is used to generate chemical free energy, stored in glucose. The light-independent Calvin cycle, also (misleadingly) known as the "dark reaction" or "dark stage", uses the energy from short-lived electronically-excited carriers to convert carbon dioxide and water into organic compounds that can be used by the organism (and by animals which feed on it). This set of reactions is also called carbon fixation. The key enzyme of the cycle is called RuBisCO. In the following equations, the chemical species (phosphates and carboxylic acids) exist in equilibria among their various ionized states as governed by the pH.

The enzymes in the Calvin cycle are functionally equivalent to many enzymes used in other metabolic pathways such as gluconeogenesis and the pentose phosphate pathway, but they are to be found in the chloroplast stroma instead of the cell cytoplasm, separating the reactions. They are activated in the light (which is why the name "dark reaction" is misleading), and also by products of the light-dependent reaction. These regulatory functions prevent the Calvin cycle from operating in reverse to respiration, which would create a continuous cycle of carbon dioxide being reduced to carbohydrates, and carbohydrates being respired to carbon dioxide. Energy (in the form of ATP) would be wasted in carrying out these reactions that have no net productivity.

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This video shows the proccess of ATP Cycle. It is very well done and very easy to follow and understand.  (for some reason it wont play on the wiki so just hit the whatch on youtube link and it will bring you to it.)

 

The following animation is the same animation Mr. F played for us in class. It's good to see it again to review and help visualize it (before 1 minute it shows the mitochondria we saw in class):

http://vcell.ndsu.edu/animations/atpgradient/movie.htm

 

   <----- visual on the Calvin Cycle

 

 

 

 

 

 

 

 

 

 

 This is a basic web on the photosynthesis process, where/ when molecules (H20, CO2) are entering the process. 

 

The Following Video Shows The Calvin Cycle:

 

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A picture diagram of photosynthesis that makes it even easier to understand. 

This diagram really helps too because it emphasizes on how water comes from the ROOTS and not the surface of the leaves. It also gives the basic inputs and outputs of the entire photosynthesis reaction

 

 

 

 

 

 

 

Light behaves both as a wave and a particle. Wave properties of light include the bending of

the wave path when passing from one material (medium) into another (i.e. the prism, rainbows, pencil in a glass-of-water, etc.). The particle properties are demonstrated by the photoelectric effect. Zinc exposed to ultraviolet light becomes positively charged because light energy forces electrons from the zinc. These electrons can create an electrical current. Sodium, potassium and selenium have critical wavelengths in the visible light range. The critical wavelength is the maximum wavelength of light (visible or invisible) that creates a photoelectric effect.

 

 

           Light has a big role in photosynthesis.  But the color that comes out is also important.  The visible light scale reaches from violet being the strongest, with the shortest wavelengths, to red being the weakest with the longest wavelengths.  all the colors are absorbed except for green.  The colors are absorbed while the green is reflected.  As plants that have leaves and such, start to get older and die, different colors are absorbed.  Leaves turn red, yellow, brown and other colors.  This means that those colors are being reflected, while all others are being absorbed. 

 

The following video shows how photosynthesis works in an easy to understand way and with some cool graphics. Its short but straight to the point:

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Light Independent Process (Light Reactions)

-products of light reaction form C-C bonds

-occurs in stroma

-can occur during the night as long as there is excess energy from light process

 

 

 

 

 

 

Chemiosmosis

 

Chemiosmosis is the diffusion of ions across a selectively-permeable membrane. This includes the generation of ATP and the movement of hydrogen ions across the membrane during cell respiration. The hydrogen ion will diffuse from an area of high concentration to an area of low concentration. The generation of ATP occurs  in chloroplasts and the mitochondria. Chemiosmosis allows protons to pass through the membrane using kinetic energy. The theory of chemiosmosis suggests that most ATP synthesis in respirating cells come from an electrochemical gradient across the inner membranes of the mitochondria by using the energy of NADH and FADH which is formed from the breaking down  of bonds which create energy using rich molecules such as glucose.

 

 

Chemiosmosis is the diffusion of ions across a selectively-permeable membrane. More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration.

An Ion gradient has potential energy and can be used to power chemical reactions when the ions pass through a channel (red).

Hydrogen ions (protons) will diffuse from an area of high proton concentration to an area of lower proton concentration. Peter Mitchell proposed that an electrochemical concentration gradient of protons across a membrane could be harnessed to make ATP He likened this process to osmosis, the diffusion of water across a membrane, which is why it is called chemiosmoss.

ATP synthase is the enzyme that makes ATP by chemiosmosis. It allows protons to pass through the membrane using the kinetic energy to phosphorylate ADP making ATP. The generation of ATP by chemiosmosis occurs in chloroplasts and mitochondria as well as in some bacteria.

 

The following graphic is what happens during chemiosmosis. If you notice, this is the step right before the calvin cycle occurs.

 

 

This is  a picture showing Chemiosmosis.

 

 

 

 

Here is another picture depicting Chemiosmosis. You will notice that the stroma is now on the bottom, unlike most pictures we use in class. Regardless of this, the picture shows how water is split into it's oxygen parts, and electron parts. there is a red arrow showing the path of these electrons and how they are used in the creation of NADPH. This arrow is labled the 'electron transport chain' and flow through Photosystem two and one. There is also a very clear concentration gradient of the H+ ions and how ATP synthetase helps transport them across the membrane.

The following video is a very helpful representation of the electron transport chain, otherwise known as chemiosmosis. http://www.youtube.com/watch?v=Idy2XAlZIVA 

 http://www.wiley.com/college/boyer/0470003790/animations/photosynthesis/photosynthesis.htm - Here is an interactive website that goes through the steps of light and dark reactions in photosynthesis, covering these major concepts. This website also covers photo respiration.

 

 

 

 

 

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Here is an interesting video that explains how photosynthesis works with specific layers of a plant (includes illustrated diagrams to show the process of photosynthesis).

 

*Here are some of the notes I took during the jeopardy reveiw game during class today.  This might help you study for the quizzes:

~What are the wavelengths used in photosynthesis? : 450-550

~What happens to the light energy during photosynthesis? : it is stored in the bonds of the hydrogen ions.

~What are the inputs and outputs of the light reaction? : Inputs are ADP, NADP, and sunlight.  Outputs are ATP, NADPH and oxygen.

~What molecule is charged by the electron transport chain? : NADPH

~Why is water needed for photosynthesis? : Once inside the chloroplast, the water molecule is broken up, and the hydrogens are combined with ADP to make ATP, which will go on to the Calvin Cycle, and the oxygen is released as a waste product which we need to survive. 

 

This is on the wrong page!

 

EFFECTS ON PHOTOSYNTHESIS:

1. Shortage of water (b/c it is one of the raw materials of photosynthesis)

http://www.ears.nl/ppm/user_images/LPD-ficus_copy.jpg

 

2. Temperature (b/c photosynthesis depends on enzymes that work best in 0-35 degree celcius temperatures)

http://image.tutorvista.com/content/nutrition/temperature-versus-rate-of-photosynthesis.jpeg

 

3. Light Intensity (the more light, the faster the rate of photosynthesis up to a maximum point, then it will no longer affect it)

http://www.skoool.ie/skoool/uploadedImages/contentimages/graph2.gif

 

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This video gets to the good stuff at around 1:15

 

 

 

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