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Transcript of Photosynthesis
By Sarah Durlofsky
Rate of Photosynthesis
What are some factors that can affect the rate of Photosynthesis?
-Carbon Dioxide (CO2)
Two Important Parts of Photosynthesis
are the main cycles that make photosynthesis occur.
6CO2 + 6H2O -> C6H12O6+6O2
Photosynthesis is made up of several cycles, the calvin cycle and the light reaction.
Parts of the Leaf
is a very waxy layer of the leaf. It helps protect the leaf from getting or losing too much water and protects against insects. Without it, the leaf would get destroyed or eaten.
This section of the leaf, known as the
. is needed for photosynthesis. It is transparent so light can go through to the mesophyll.
is a tissue layer (
) of a bunch of very long cells. These cells are very skinny and wide to be able to fit as many across the surface area as possible. The tissue also makes diffusion of Carbon Dioxide and Water to all the cells in the leaf!
contains the openings (
for the leaf. The stoma ois crucial for photosynthesis because it lets carbon dioxide come in and they let the plant release oxygen which is a waste product of photosynthesis. Sometimes the stoma lets too much escape and the resulting dry leaf is unable to start the light reaction.
surround the stomates
(stomates is the plural of stoma)
in the lower eperdermis. The guard cells are able to open the
which let in carbon dioxide and Water. When water comes out of the stomates it is known as transportation. This is very bad for the leaf because it dries the leaf out.
of the leaf consist of both
. These veins are necessary for the leaf because they carry the water and sugar throughout the plant from the roots. The xylem carries the water and the phloem carries the sugar and nutrients throughout the plant.
- (Pigments are embedded)
absorb light. which is then used in the light reaction of photosynthesis. Photosynthesis gives the plant energy in the form of ATP and glucose.
There are many different pigments that are used in photosynthesis. The main ones are
1). The Process starts with 5 carbon molecules of
(a five carbon molecule).
2). A Carbon Dioxide then goes into the the
an enzyme) and the Rubisco catalyzes the the reaction and bonds a CO2 with the RuPB in the active site of the Rubisco.
3). The Carbon Dioxide then bonds with the with the RuBP in the active site of the Rubisco. This makes a 6 carbon molecule!
3a). There are 6 carbon molecules. Each carbon molecule has 6 carbons. This makes a total of 36 carbons. These carbon molecules also are bonded with hydrogen and oxygen.
4). The 6 carbon molecule is very unstable. The molecule then splits into 2 3-Carbon molecules. These molecules are called
5). The energy from ATP in the light reaction rearranges the PGA into another molecule called
. The ADP+P goes back to the light reaction
6). The NADPH from the light reaction has very high energy so it bounces off of the DPG complexes. This makes the NADPH become
7). The NADP+ puts 2 electrons into the DPG. This changes the DPG complexes into
8). Then, the 2 G3P with the highest energy level (have the most electrons) spin out of the cycle. Most of the G3P stay in the cycle. This process is repeated 6 times for the reaction to create a full glucose.
9). The rest of the G3P in still the calvin cycle use more ATP from the light reaction to turn back into RUBP. This cycle then repeats itself.
REMEMBER: The calvin cycle is not at all like a carousel. Instead, pulls necessary ingredients from other cycles and other parts of the stroma. This process occurs many times each second in the stroma of the thylakoid.
1). Water splits into 2 electrons, 2 positively charged hydrogen ions, and 1/2 O2 molecules. This process is called
2). The hydrogen ions stay in the
(this will be important for the creation of ATP) and the 1/2 02 is released by the plant as waste.
3). The electrons then go into the reaction center of
(a pigment) and get energized from the light from the sun.
4). The electrons are now at the peak of their energy from the sun and are in the
5). Then the electrons start to gradually go down the
electron transport chain
6). The electrons have now reached the
reaction center, which has a slightly higher energy level compared to that of photosystem II.
7). The electrons absorb more energy from sunlight and again are at the electron acceptor.
8). The electrons then go through another shorter electron transport chain and finally reach the final phase of the electron transport chain, which is bonding with
NaDP+ and H+
9). The electrons bond with the NaDP+ and H+ to create
. NaDPH is crucial to the calvin cycle.
plants are plants that grow in moderate environments. This means that the plant lives in a temperate environment and the environment does not have changes in temperature and water
plants only make up about 5 percent of all plants. Cactuses and the bonsai trees are two examples of cam plants. These types of plants only open their stomates at night. Therefore the plant is only able to take in carbon dioxide at night. During the day, the plant carries out photosynthesis with the carbon dioxide it stored during the night. If the plant runs out of Carbon Dioxide, it can no longer photosynthesize. Cam plants live in very hot dry climates, so having the stomates closed helps the plant keep in water.
plants open their stomates for short bursts throughout the night and day.
2). The Carbon Dioxide bonds to a 3 Carbon molecule called
3). The entering carbon dioxide bonds make
, a 4 carbon molecule. The carbon dioxide is now DISGUISED in the PEP.
4). This makes the concentration gradient larger so more Carbon Dioxide can come into the plant quicker (rate of diffusion).
5). The Oxacolacetane takes the Carbon Dioxide to the cloroplast (in c4 plants is located in the vein).
6). The Carbon Dioxide gets dropped off and the 3- Carbon molecules that are left get rearranged back into PEP to go pick up more Carbon Dioxide.
It is important to note that part 6 uses ATP. This means that there is an additional energy cost to break these bonds. This requires plants to create much more ATP and that is why not all plants are c4 plants.
Enzymes only work in ideal temperatures. Therefore enzymes will become denatured if the temperature is too low and will be unable to catalyze certain reactions. If the temperature is too high then the enzymes become denatured and are unable to catalyze certain reactions that are needed for photosynthesis.
Carbon Dioxide is necessary for photosynthesis to occur. At lower amounts of carbon dioxide, the rate of photosynthesis increases. If there is an excess of Carbon Dioxide, the enzymes can not catalyze it all fast enough and so the rate of photosynthesis plateaus.
Light is needed for the photosynthesis. If lower amount of light, the rate of photosynthesis increases. If there is too much light, the photosynthesis rate reaches a saturation point and the light reaction can not go through the reaction any faster.
Water, like Carbon Dioxide and light, is needed in photosynthesis. At lower amounts of water, the rate of photosynthesis increases. Without water, photosynthesis can not occur. However, if there is too much water, the light reaction can not move fast enough and therefore the rate plateaus.
"goo" in the chloroplast.
The Chloroplast is located in the mesophyll tissue.
Chlorophyll a is the main pigment for photosynthesis (it reflects bluish green)
The other pigments are-
chlorophyll b (reflects yellowish green)
Carotenes (reflects orange)
Xanothophylls (reflects yellow)
Tannin (reflects brown)
Phycocyanins/antecyanins (reflect red and purple)- these are only produced in the fall
Carotenes and Xanthophylls are called Carotenoids, this means that they always exist in the leaf.
Light Reaction inside the Thylakoid
The Hydrogen ions are broken off from the water molecules in photolysis and are now in the lumen (empty space) of the thylakoid. They get this energy from the energy in the Electron transport chain. This hydrogen is building up inside the lumen and goes through the protein channel. These special channels are called
. This passage of the H+ through the channels causes the ATP synthase to spin like a turbine engine and the spinning forces bonds the ADP+P which makes ATP. The ATP is used for the NADPH in the electron transport chain or goes back into the thylakoid.
If there is too much oxygen,
occurs. This means that there is too much oxygen in the system. This is bad for photosynthesis and therefore bad for the plant. Oxygen and carbon dioxide molecules look very similar. In fact, oxygen is able to fit into the active site of the rubisco enzyme in the calvin cycle. When this happens, no carbon fixation is able to occur, therefore no sugar is made. Instead, a waste molecule gets made. This wastes energy and is not good for plants.