Respiration Review  Fill in the blanks! A=2,B=3, C=4D=8E=32 F=36******************************************************  Glycolysis makes ____ NET ATP and ______  (Intermediate Step) 2 pyruvate  2 acetyl CoA makes _____________  Krebs Cycle makes ____________, _________, and _______ ATP

Photosynthesis 6CO2 + 6 H20  C6H12O6 + 6O2

Inside a leaf  Chloroplasts are in cells of the mesophyll, green tissue in the leaf’s interior  CO2 enters and O2 exits the leaf thru pores called stomata  Stomata are controlled by guard cells which can open and close them

LIGHT Dependent Reaction!  Takes place in the thylakoid (multiple thylakoids= granum)  Photons of light (energy units) strike a leaf and activate chlorophyll which will excite electrons.  Activated chlorophyll molecule then passes these excited electrons down to a series of electron carriers to produce ATP and NADPH  Point of light reaction…make ATP + NADPH

A bit about light… Sunlight is electromagnetic. It has a behavior that is both wavelength and particle like… -The wavelengths are the distance between crests of electromagnetic waves -Wavelengths that are absorbed disappear…what color would a pigment that absorbs all wavelengths be? -When white light which contains all wavelengths of visible light illuminates a pigment, the color you see is the color most reflected or transmitted by the pigment

Chlorophyll a + Chlorophyll b + carotenoids -Chlorophyll a= only pigment that works directly and green in color -Chlorophyll b=blue-green -Cartenoids= yellow-orange…these have the ability to dissipate excessive light energy that would otherwise damage chlorophyll

Photosystems  Chlorophyll a, b, and cartenoids are assembled into photosystems within the thylakoid.  Photosystems are light harvesting complexes.  Each photosystem has: -Antenna complex -Reaction center chlorophyll -Primary Electron Acceptor

Photosystem I and II  Photosystem I=has specialized chlorophyll a molecule known as p700  Photosystem II= has specialized chlorophyll a molecule known as p680  They were named I and II because of the order they were discovered, but photosystem II actually occurs before photosystem I.

 Noncyclic Photophosphorylation  produces ATP and NADPH using Photosystem I and II. Step 1) P680 (photosystem II) captures light and passes 2 excited electrons down an ETC to make ATP and then returned to P700 Step 2) A molecule of water is split (photolysis) by sunlight which releases….? Step 3) P700 (photosystem I) captures light and passes excited electrons down an ETC to produce NADPH

Chemiosmosis in Photosynthesis  H+ ions accumulate in thylakoids…as photolysis occurs this releases H+ to the inside of thylakoids (oxygen released outside) AND H+ accompany electrons as they pass in the ETC between PS 1 and 2  Similar situation as with chemiosmosis in respiration…pH and electric gradient is made, ATP synthase generates ATP

Reminder of What Chemiosmosis Is:  Chemiosmosis is the diffusion of ions across a membrane. More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane. ions membranehydrogenions membranehydrogen  Requires: a phospholipid bilayer, a proton pump, protons and ATPase  Chemical Energy is used to pump protons through a proton pump (intrinsic protein). This creates a high concentration of protons (H+). ATP synthase has a channel that allows for the facilitated diffusion of protons back in through the membrane which in turn catalyzes the formation of ATP.  Exists in respiration (in mitochondria) and photosynthesis (in chloroplasts)

 Cyclic Phosphorylation  Step 1) P700 (Photosystem 1) captures light and passes excited electrons down an ETC to make ATP…it’s much simpler.  Step 2) ATP is made BUT NADPH is NOT and water is NOT split by sunlight  Why is this done? Calvin needs a LOT of ATP, and this pathway is quick and another way to supplement the ATP needed besides noncyclic. ANIMATION:

Calvin Cycle (Light Independent, C3)  This takes place in the stroma  It will use what was made in light reaction (ATP, NADPH) to make SUGAR  Also, this is where the CO2 will be taken in. CO2 will be “fixed” in this cycle.  CO2 enters, and is combined with rubisco (RuBP)  6 CO2+ 6 RuBP= 12 PGA (phosphoglycerate)

 12 ATP + 12 NADPH are used to convert 12 PGA to 12 PGAL (phosphoglyceraldehyde) …basically what you’re doing is giving it more energy (from the ATP and NADPH)  2 of the PGAL is used to build glucose. From glucose you can make fructose or OR combine with disaccharides (like sucrose)  10 of the PGAL is converted (by the help of 6 ATP) to make 6 RuBP to allow the cycle to repeat: (6 CO2+ 6 RuBP= 12 PGA )

 Overall equation for Calvin Cycle was: 6CO2+ 18 ATP + 12 NADPH  18 ADP + 18 Pi + 12 NADP+ 1 gulcose

The Problem of Photorespiration…  RuBP is one of the most common proteins on Earth. A great thing for plants, but it’s not so picky. It can fix CO2 but it also will just as well fix O2.  Bright light can stunt the growth of C3 plants. Why do you think this could be?  The specific name of this is called photorespiration which means it fixes oxygen. The products of this aren’t useful so plant perioxisomes are often used to help break them down.

Added Help  C4 Photosynthesis…an “add on feature” that enhances CO2 fixation in areas that are hot and would have lots of photorespiration  Carbon dioxide can combine with phoenolpyruvate (PEP) now instead of rubisco. It makes OAA (oxaloacetate) which is then converted to malate.  Malate is like a bus that will deliver CO2 to specialized cells called the bundle sheath cells. These cells are deeply packed and not in contact w/ much O2

 In the sheath cell, malate is converted into pyruvate and CO2..pyruvate is shuttled back and ATP will convert it back into PEP CAM PHOTOSYNTHESIS: CAM PHOTOSYNTHESIS: -Similar to C4 photosynthesis EXCEPT the OAA is converted into malic acid (instead of malate) and sent to a cell’s vacuole at night. During the day, it converts back to oxaloacetate and CO2 is released for photosynthesis -Very useful for very dry environments. Cacti and succulents commonly do CAM photosynthesis

Why CAM Photosynthesis is Useful  Most plants open stomata (leaf pores) in the day time to take in CO2. But CAM photosynthesis allows stomata to open at night (as these plants in dry environments want to conserve water and do not want to lose water during the hot, sunny daytime)

Ultimate Question For the following, pick (A) Photosynthesis, (B) Respiration, or (C) both. 1.Uses NAD+, an electron carrier. 2.Uses chemiosmosis to generate ATP. 3.Has a step that takes place in the thylakoid. 4.Generates CO2 as a byproduct. 5.Is endergonic. 6.Can be done by bacteria. 7.Needs a proton (H+) pump. 8.A probe that measures oxygen could determine its rate.