Friday, December 19, 2008

Hey C Block Bio since you've been hearing me talk so much about it I figured I post it on the blog. I got into Bates! I hope everyone has great break.

Wednesday, December 17, 2008

Review for Final!

Hey girls! Here's one last review of Cellular Respiration and Photosynthesis. I’ve included several diagrams to help prepare you for the exam and I hope all of you do well!

Cellular Respiration:

The ATP-generating process that occurs within cells. Energy is extracted from glucose to form ATP from ADP and Pi:
C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O + energy

Anaerobic Respiration is cellular respiration in the presence of oxygen. There are three components of anaerobic respiration:
  • Glycolysis: the decomposition of glucose to pyruvate; this process occurs in the cytosol. Here is a summary of the steps:
    • 2 ATP are added (the first several steps require the input of energy)
    • 2 NADH are produced (NADH forms when NAD+ combines with two electrons and H+) (NADH is a very energy-rich molecule)
    • 4 ATP are produced
    • 2 pyruvate are formed
  • Krebs Cycle: details what happens the pyruvate after glycolysis. Here is a summary of the steps:
    • Pyruvate to acetyl CoA (this is a step leading up to the actual Krebs cycle, pyruvate combines with coenzyme A to produce acetyl CoA, also producing 1 NADH and 1 CO2)
    • Acetyl CoA combines with OOA to form citrate (producing 3 NADH and 1 FADH2, and releasing CO2)
  • Oxidative Phosphorylation: the process of extracting ATP from NADH and FADH2.
    • Electrons from NADH and FADH2 pass along an electron transport chain
    • Along each step of the chain, the electrons give up energy used to phosphorylate ADP to ATP
      • NADH generates about 3 ATP
      • FADH2 generates about 2 ATP
    • The final electron accept is oxygen. The O2 accepts the two electrons and with 2 protons, forms water
Below is a diagram of the process of Cellular Respiration:

The two major processes of Cellular Respiration, the Krebs Cycle and Oxidative Phosphorylation, occur in the Mitochondria.
The Mitochondria has four distinct areas:
    • Outer Membrane: double phospholipid bilayer
    • Intermembrane Space: narrow area between the inner and outer membranes where protons accumulate
    • Inner membrane: double phospholipid bilayer that has convulsions called cristae (this is where oxidative phosphorylation occurs). Within this membrane, the electron transport chain removes electrons from NADH and FADH2 and transports protons from the matrix tot he intermembrane space.
    • Matrix: the fluid material that fills the inner membrane (this is where the Krebs cycle and the conversion of pyruvate the acetyl CoA occur)
Below is a diagram of a mitochondria: Chemisosmosis is the mechanism of ATP generation that occurs when energy is stored in the form of a proton concentration gradient across a membrane. Here is a description of this process during oxidative phosphorylation in mitochondria.
• The Krebs Cycle produces NADH and FADH2 in the matrix and CO2 is generated and substrate level phosphorylation occurs

• Substrate level phosphorylation occurs when a phosphate group and its associated energy is transferred to ADP to form ATP. The substrate molecule donates the high energy phosphate group

• Electrons are removed from NADH and FADH2. These electrons move along the electron transport chain, from one protein complex to the next

• Protein complexes transport H+ ions from the matrix to the intermembrane compartment
• As H+ are transferred, the pH in the intermembrane space decreases, and the pH in the matrix increases.

• ATP synthase generates ATP


Here are some questions about Cellular Respiration:

1. The final electron acceptor of the electron transport chain that functions in anaerobic respiration is:

a) NAD+

b) NADH
c) pyruvate

d) oxygen

e) ADP

2. Which of the following processes occur in the Mitochondria?

a) glycolysis
b) Krebs Cycle
c) Oxidative Phosphorylation

d) all of the above

e) only b and c


3. Glycolysis occurs in the:

a) Outer Membrane of the Mitochondria

b) Cytosol
c) Inner Membrane of the Mitochondria

d) Intermembrane Space of the Mitochondria

e) Matrix of the Mitochondria


Answers:
1. d 2. e 3. b

Photosynthesis:
The process of converting energy in sunlight to energy in chemical bonds, especially glucose. The general chemical equation for photosynthesis is:
6 CO2 + 6 H2O + light ->C6H12O6 + 6O2

Here is a diagram showing the main components of Photosynthesis:


Begins with light-absorbing pigment in plant cells. A pigment molecule is able to absorb the energy from light only within a narrow range of wavelengths. Different pigments, capable of absorbing different wavelengths, act together to optimize energy absorption. These pigments include the green chlorophyll a and chlorophyll b and the carotenoids, which are red, orange or yellow. When the light is absorbed into one of these pigments, the energy from the light is incorporated into electrons within the atoms that make up the molecule. These energized electrons are unstable and almost immediately re-emit the absorbed energy. The energy is then reabsorbed by electrons of a nearby pigment molecule. This process continues, with the energy bounding from one pigment molecule to another. The process ends when the energy is absorbed by one of two special chlorophyll a molecules, P680 and P700 (the numbers represent the wavelengths at which they absorb their maximum amounts of light: 680 and 700 nanometers). Chlorophyll P700 forms a pigment cluster called photosystem I (PS I) and chlorophyll P680 forms photosystem II (PS II)

Photophosphorylation is the process of making ATP from ADP and phosphorylation using energy derived from light. There are two kinds of photophosphorylation:
  • Noncyclic Photophosphorylation: takes the energy in light and the electrons in H2O to make the energy-rich molecules ATP and NADPH. Noncyclic photophosphorylation begins with PS II and follows these steps:
    • Electrons trapped by P680 in photosystem II are trapped by light
    • Two energized electrons are passed to a molecule called the primary electron acceptor.
    • Electrons pass through an electron transport chain consisting of proteins that pass electrons from one carrier protein to the next
    • The two electrons move down the electron transport chain, losing energy. This energy is used to phosphorylate, about 1.5 ATP molecules
    • The electron transport chain terminates with PS I (P700). Here, the electrons are again energized by sunlight and passed to a primary electron acceptor
    • The two electrons pass through a short electron transport chain and then combine with NADP+ and H+ to form NADPH (a coenzyme)
    • The loss of the two electrons from PS II is replaced when H2O is split into two electrons, 2 H+ and 1/2 O2. The two electrons from H2O replace the lost electrons from PS II, one of the H+ provides the H in NADPH and the 1/2 O2 contributes to the oxygen gas that is released
  • Cyclic Photophosphorylation: occurs simultaneously with Noncyclic Photophosphorylation to generate addition ATP. Cyclic Photophosphorylation occurs when the electrons energized in PS I are "recycled".
    • Energized electrons from PS I join with protein carriers and generate ATP
    • Electrons then return to PS I, where they can be energized again to participate in cyclic or noncyclic photophosphorylation
Calvin Cycle: takes chemically unreactive, inorganic CO2 and incorporates it into an organic molecule that can be used in biological systems. The function of the pathway is to produce a single molecule of glucose (C6H12O6), and in order to accomplish this, the Calvin Cycle must repeat six times and use 6 CO2 molecules.
The Calvin cycle is referred to as C3 photosythensis because the first produce formed, PGA contains three carbon atoms.
No light is directly used in the Calvin cycle, however, this process cannot occur in the absense of light.
Here is a summary of the steps (only the most important molecules are mentioned and the molecules involved have been multiplied by 6):

  • Carboxylation: the enzyme rubisco catalyzes the merging of CO2 and RuBP
    • 6 CO2 combine with 6 RuBP to produce 12 PGA
  • Reduction: the energy in the ATP and NADPH molecules is incorporated into G3P. ADP, Pi and NADP+ are released and then re-energized in noncyclic photophosphorylation
    • 12 ATP and 12 NADPH are used to convert 12 PGA to 13 G3P
  • Regeneration: Regenerating the 6 RuBP originally used to combine with 6 CO2 allows the cycle to repeat
    • 6 ATP are used to convert 10 G3P to 6 RuBP
  • Carbohydrate Synthesis: The two remaining G3P are used to build glucose or other monosaccharides
In summary, the Calvin cycle takes CO2 from the atmosphere and the energy in ATP and NADPH to create a glucose molecule.
Below are some diagrams of the Calvin cycle:

The reactions of photosynthesis take place in the Chloroplasts.
Chloroplasts consist of the following areas:
  • Outer Membrane: double layer of phospholipids
  • Intermembrane Space: narrow area between the inner and outer membranes
  • Inner Membrane: double phospholipid bilayer
  • Stroma: fluid material that fills the area inside the inner membrane; where the Calvin cycle occurs
  • Granum: stacks of pancake-like membranes (each individual membrane is a thylakoid). The membranes of the thylakoids contain the protein complexes and other electronc arriers of light-dependent reactions
  • Thylakoid Lumen: inside of the thylakoid, where protons accumulate
Below is a diagram of a chloroplast:


Chemisosmosis
is the mechanism of ATP generation that occurs when energy is stored in the form of a proton concentration gradient across a membrane. Here is a description of this process during photophosphorylation in chloroplasts.
• Protons accumulate inside the thylakoids and protons are acarred from the tromas into the lumen by a cytochrome

• A pH and electrical gradient across the thylakoid membrane is created (the pH inside the thylakoid decreases and the pH in the stroma increases)

• ATP synthases generate ATP
• The Calvin Cycle produces G3P using NADPH and CO2 and ATP

There are two other types of Photosynthesis: C4 Photosynthesis and CAM Photosynthesis

C4 Photosynthesis: Improving on photosynthetic efficiency, some plants have evolved a special "add-on" feature to C3 photosynthesis.
  • When CO2 enters the leaf, it is absorbed by the usual photosynthesizing cells, the mesophyll cells.
  • Instead of being fixed by rubisco into PGA, the CO2 combines with PEP to form OAA
  • OAA has four carbon atoms thus the name C4 photosynthesis
  • OAA is then converted to malate, which is shuttled through plasmodesmata to the bundle sheath cells
  • Here, the mala is converted to pyruvate and CO2 and then shuttled back to the mesophyll cells where one ATP is required to convert the pyruvate back to PEP
  • This process then repeats
The purpose for moving CO2 to bundle sheath cells is to increase the efficiency of photosynthesis. Because the bundle sheath cells rarely make contact with an intercellular space, very little oxygen reaches them. When malate delivers CO2 to a bundle sheath cell, rubisco begins the Calvin cycle (C3 photosynthesis).
In order for photosynthesis to occur stomata must be open to allow CO2 to enter; however when the stomata are open, H2O can escape. The higher rate of photosynthesis among C4 plants allows them to reduce the time that the stomata are open, thereby, reducing H2O loss. Therefore, C4 plants are found in hot, dry climates.
Below is a diagram of C4 Photosynthesis:

CAM Photosynthesis: another "add-on" feature to C3 Photosynthesis; the physiology of this pathway is almost identical to C4 photosynthesis.
  • PEP carboxylase still fixes CO2 to OAA
  • OAA is converted to malic acid
  • Malic acid is shuttle to the vacuole of the cell
  • At night, stomata are open, PEP carboxylase are active and malic acid accumulates in the cell's vacuole
  • During the day, stomata are closed, malic acid is shuttled out of the vacuole and converted back to OAA, releasing CO2
  • CO2 is fixed by rubisco and the Calvin cycle proceeds
Advantage of CAM is that photosynthesis can proceed during the day while the stomata are closed, greatly reducing H2O loss. CAM provides an adaptation for plants that grow in hot, dry environments with cool nights.
Below is a diagram of CAM photosynthesis:


Here are some questions about Photosynthesis:

1. The reaction-center chlorophyll of photosystem I is known as P700 because
a) there are 700 chlorophyll molecules in the center
b) this pigment is best at absorbing light with a wavelength of 700 nm
c) there are 700 photosystem I components to each chloroplast
d) it absorbs 700 photons per microsecond
e) the plastoquinone reflects light with a wavelength of 700 nm

2. What are the products of noncyclic photophosphorylation?
a) heat and fluorescence
b) ATP and P700
c) ATP and NADPH
d) ADP and NADP
e) P700 and P680

3. Where does the Calvin Cycle take place?
a) stroma of the chloroplast
b) thylakoid membrane
c) cytoplasm surrounding the chloroplast
d) chlorophyll molecule
e) outer membrane of the chloroplast

Answers:
1. b) 2. c) 3. a)


Finally, I thought it would be helpful to see the relationship between photosynthesis and cellular respiration, so, I have included two diagrams and a chart showing the similarities and differences between the two.


I hope this has helped and good luck!!!

Tuesday, December 16, 2008

Overview of Lab 5: Respiration

Purpose: To measure the rate of cellular respiration in germinating peas by observing the volume of gas surrounding the peas at various intervals.

Materials:
  • A total of 6 respirometers
  • glass beads
  • germinating seeds
  • non-germinating seeds
  • water bath with 10 degrees water
  • water bath with 25 degrees water (room temperature)
  • KOH solution
  • absorbent cotton
  • non-absorbent cotton
Instructions:
  1. Soak the absorbent cotton with KOH in each of the three vials.
  2. Cover with non-absorbent cotton.
  3. Add 25 germinating peas to vial 1
  4. Add 25 non-germinating peas to vial 2 and cover them with enough glass beads to that it is at the same volume as vial 1.
  5. Add enough glass beads to vial 3 to have the same volume of vials 1 and 2. Vial 3 is the control.
  6. Cap each vial with a stopper, seal the respirometor, and add weights to each vial (so they don't float in the water).
  7. Place the three vials in the container with water of 10 degrees, with the tips of the vials resting on a sling. Allow the vials to equilibrate for a few minutes.
  8. Lower the tips into the water, and take an initial reading.
  9. Take readings from each respirometer for 15 minutes with 5 minute intervals. This is done by reading the water graduations on the pipettes. The reading is a measurement of oxygen consumption and therefore an indirect measurement of repiratory rate.
  10. Repeat steps 7,8,9 with a second set of vials in a water bath of 25 degrees.

Results:
  • Water will enter the pipettes and travel a short distance. As respiration occurs, O2 is consumed in the vials, and pressure in the vials and pipettes drops. When the pressure drops, additional water from the water bath will enter the pipettes.
  • The experiment should yield results which follow the generalizations,
  1. As temperature decreases/increases respiration decreases/increases.
  2. Germinating seeds respire more.

Cellular respiration
is the breakdown of glucose with oxygen to produce carbon dioxide, water, and energy

The volume of gas can be affected by both the use of oxygen gas and the product of carbon dioxide, carbon dioxide is removed by using potassium hydroxide. KOH reacts with O2 to produce solid K2CO3.

Because CO2 gas is removed from the reaction, the gas volume change can only be effected by consumption of oxygen (as a result of respiration), change in temperature, and change in atmospheric pressure.

Questions

1. What was the purpose of the beads?

Glass beads are added to maintain equal volumes so that oxygen gas can be measured accurately.

2. What happens to the temperature of gas when the pressure increases (assuming volume remains constant)?

The temperature of gas increases when the pressure increases.

3. What happens to the volume of gas when the temperature decreases (assuming pressure remains constant?

The volume of gas decreases when the temperature of gas decreases.


Monday, December 15, 2008

Lab 4:Plant Pigments & Photosynthesis

Intro:
*Photosynthesis: when plant cells convert light energy to chemical energy which is stored in sugar and other organic compounds.
*Chlorophyll: primary photosynthetic pigment pigment in chloroplasts- crtitcal to photosynthesis.
*This lab contains 2 seperate activities: Plant Pigment Chromatography & Measuring the Rate of Photosynthesis

Plant Pigment Chromatography:
*Key Concepts:
-Paper chromatography: technique used to seperate a mixture into its component molecules. These molecules move up the paper at different rates because of differences in solubility, molecular mass, and hydrogen bonding with the paper.
  • Example: draw a large circle in the center of filter paper with black water-soluble, felt-tip pen. Fold the paper into a cone and place the tip in a container of water. In a few minutes you will have tie-dyed filter paper.

The green, blue, red , and lavender colors that come from the black ink should help understand that what might appear to be a single color may be composed of different pigments.

*Design of the Experiment I:

-Pigments in paper chromatography are dissolved in a solvent that carries them up the paper. The solvent in the ink example is water. To seperate the pigments, you must use an organic solvent.
chromatography setupIn this activity, you will seperate plant pigments using an organic solvent such as a mixture of ether and acetone. Make sure to keep the bottle tightly closed except for when using it because the solvent can be readily vaporized and produce fumes you shouldn't breathe.
*Depositing the Pigment:
-Deposit pigment by rolling a quarter over a spinach leaf about 15 times to make a heavy green line.
pigment separation
*Analysis of results I:
-If you would do many chromatographic seperations, each for a different length of time, the pigments would migrate a different distance. However, the migration of each pigment relative to the migration of the solvent would'nt change. This migration of pigment can be calculated by using this formula:

Measuring the Rate of Photosynthesis:
*Key Concepts:
-In the light reactions of photosynthesis, light energy excites electrons in plant pigments like chlorophyll and raising them to a higher energy level. These electrons reduce compounds in the thylakoid membrane, and the energy is eventually captured in the chemical bonds of NADPH and ATP.

Excitation of electrons

-Using DPIP As an Electron Acceptor:

Light excitation of DPIPIn this activity, you will measure the rate of the electron excitation when light hits chlorophyll. You will use DPIP, a blue compound, as an electron acceptor.

When light strikes the chloroplasts, the DPIP is then reduced by the "excited" electrons from chlorophyll and becomes colorless as it accepts the electrons. You wil use a spectrophotometer to measure the color change, which tells us the rate of the light reactions under various conditions.

-The Spectrophotometer: an instrument that can be adjusted to illuminate a sample with a specific wavelength of light. it measures the amount of light energy that has been absored or transmitted by the sample. As DPIP becomes colorless, the amount of light of wavelength 605 nm transmitted through the sample will increase. Even though you can see the color change, the spectrophotometer quantifies the change.

  1. Close the lid on the empty sample chamber
  2. Use the knob to select desired wavelength (605 nm)
  3. Use th e"On-Off" knob to adjust the meter needle to 0% transmittance
  4. Put the blank tube in the sample chamber and close the lid
  5. Use the third knob to adjust tje meter to 100% transmittance
  6. Put the sample in the sample chamber and close the lid
  7. Without moving any knobs, read the % transmittance on the meter

*Design of the Experiment:

Flowchart of the experiment

-After illuminating the reaction tubes, use the spectrophotometer to measure the percentage of transmittance at wavelength 605 nm.

-If DPIP is in an oxidized state it will appear blue and the percentage of the light transmitted will be low. If chlorophyll's electrons have been excited and reduce the DPIP, the sample will become paler allowing more light energy to pass through the sample. You can measure this change over time until the sample is almost colorless and the percentage of transmittance is high.

-In this experiment, one tbe will contain all solutions used except DPIP. since the tube contains chloroplasts, it wil be green. the other tubes will be experimental, containing either boiled or unboiled chloroplasts.

*Helpful Hints:

  • Be sure to read the % transmittance IMMEDIATELY after adding the chloroplasts to each tube.
  • Keep the test tubes clean!
  • Mix each sample thoroughly before measuring
  • Be sure to place all test tubes into the spectrophotometer in the same orientation each time so that variations in the glass do not mask your results.
  • Maintain a constant distance from the light source to the sample for ALL tubes.

*Analysis of Results II:

-Print the graphs below and based on your understanding of light reactions, draw in the approximate shapes of the curves you predict.

-Expose the tubes to light and make an initail spectrophotometer reading at 5, 10, and 15 minutes.

*Some questions:

1. If a different solvent were used for the chlorophyll chromatography described earlier, what results would you expect? (activity I)

a)the traveling distances for each pigment will be different, but Rf values stay the same.

b)Relative position of bands will be different.

c)If time is held constant, results will be the same.

2.What is the role of DPIP in this activity II?

a)It does the same thing as chlorophyll by taking in light energy.

b)Its an elctron donor and stops the formation of NADPH.

c)Its an electron acceptor and is reduced by electrons from chlorophyll.

A photosynthesis website

This came across my AP list serve and thought it might be used as a review tool.

Linkhttp://www.botany.uwc.ac.za/ecotree/Defaultnetscape.htm

Enjoy
Mrs. Lyon

Chapter 10 Notes

There are two other ways in which plants can fix carbon—C4 photosynthesis and CAM photosynthesis

Lots of plants living in hot, dry climates use C4 fixation instead of C3 fixation (the standard Calvin cycle). In C4 fixation, the first carbon compound formed in the Calvin cycle contains four carbons instead of three.

C4 plants have two different kinds of photosynthetic cells: bundle-sheath cells and mesophyll cells. The bundle-sheath cells are grouped around the leaf’s veins, and the mesophyll cells are dispersed elsewhere around the leaf.


The steps of C4 photosynthesis are as follows:

1. CO2 is added to phosphoenolpyruvate (PEP) to form the four carbon compound oxaloacetate of oxaloacetate acid. This enzyme is catalyzed by PEP carboxylase, and this process is very quick and efficient.

2. Mesophyll cells export the oxaloacetate to the bundle sheath cells, which break the oxaloacetate back down into CO2.

3. The CO2 is converted into carbohydrate through the regular Calvin cycle.

Basically C4 photosynthesis is just a way to speed up regular photosynthesis, since PEP carboxylase works much faster than rubisco, the enzyme o fC3 photosynthesis.

The alternative to C3 photosynthesis is CAM photosynthesis

CAM photosynthesis is also an adaption to hot dry climates. The plants that participate in this kind of photosynthesis open their stomata at night and close them during the day, so that they experience minimal water loss during the day when the sun is out. (Non-CAM plants do the opposite of this). Because their stomata are closed during the day, CO2 can’t get into the leaves during the day—so they take it up at night.

CAM plants take CO2 into their leaves at night, convert it into carious rganic compounds, and put it into temporary storage in their vacuoles. When morning comes and their stomata close, these plants release the stored CO2 so that they can use light energy to perform the normal reactions of photosynthesis.

In both C4 and CAM photosynthesis, CO2 is first transformed into an organic intermediate before it enters the Calvin cycle. All of the processes—C3, C4 and CAM photosynthesis—use the Calvin cycle; they just have different methods for getting there.

What are the two ways in which plants can fix carbon?
a) C4 photosynthesis
b) the Calvin Cycle
c) CAM phosphorylation
d) ATP synthase

Which process is most directly driven by light energy?
a) creation of a pH gradient by pumping protons across teh thylakoid membrane
b)carbon fixation in the stroma
c)reduction of NADP+ molecules
d) removal of electrons from the chloroplasts from chlorophyll molecules
e)ATP synthase

Cooperation of the two photosystems of the chloroplast is required for?
a) ATP synthesis
b)reduction of NADP+
c)cyclic photophosphorylation
d) oxidation of the reaction center of photosystem I
e)generation of a proton-motive force

Sunday, December 14, 2008

Friday, December 12th






CAM Plants and CAM Photosynthesis

An Alternative to C3 is CAM Photosynthesis

CAM photosynthesis is also an adaptation to hot, dry climates. The plants that participate in this kind of photosynthesis open their stomata at night and close them during the day, so that they experience water loss during the day when the sun is out. (Non-CAM plants do the opposite of this). Because their stomata are closed during the day, Carbon Dioxide can’t get into the leaves during the day-so that they take it up at night.

CAM Cycle:




CAM plants take Carbon Dioxide into their leaves at night, convert it to various organic compounds and put it into temporary storage in their vacuoles. When morning comes and their stomata close, these plants release the stored Carbon Dioxide so that they can use light energy to perform the normal reactions of photosynthesis.

CAM Plants:



In both C4 and CAM photosynthesis, Carbon Dioxide is first transformed into an organic intermediate before it enters the Calvin Cycle. All of the processes-C3, C4 and CAM photosynthesis- use the Calvin Cycle; they just have different methods for getting there.

The difference is that in C4 plants, the intial steps of carbon fixation are separated structurally from the Calvin Cycle, whereas in CAM plants, the two steps occur at separate times but within the same cell. But, as stated above, CAM, C4, and C3 plants all eventually use the Calvin Cycle to make sugar from Carbon Dioxide.



Questions:

1. All of the following are considered CAM plants, except:
a. Pineapple
b. Cacti
c. Succulent Plants
d. Sugar Cane

2. Which of the following is true concerning CAM Plants:
a. CAM plants open their stomata during the day
b. During the day, CAM plants take up Carbon Dioxide and form organic acids
c. CAM plants close their stomata during the day
d. During the night, CAM plants take up Carbon Dioxide and form organic acids
e. Both (a) and (d) are correct

3. How is the CAM pathway similar to the C4 pathway?
a. Carbon Fixation and the Calvin Cycle both occur in different types of cells
b. Carbon Fixation and the Calvin Cycle both occur in the same cell at different times
c. Carbon Dioxide is first incorporated into organic intermediates before it enters the Calvin Cycle
d. The initial steps of carbon fixation are separated structurally from the Calvin Cycle

4. What are the solutions to maintaining photosynthesis with stomata partially or completely closed on hot, dry days?
a. Chemiosmosis
b. C3 plants and C4 plants
c. C4 plants and CAM plants
d. Only CAM plants
e. Only C3 Plants

Answers: d, e, c, c

Just a reminder that tomorrow is the in-class comprehensive essay. After that, we will have two in-class, open-book quizzes. Hope you had a great weekend!





Wednesday, December 10, 2008

Ch. 10 Notes Continued

Today Mrs. Lyon had to leave early, so we just took notes in class.
  • The vocab quiz has been moved to tomorrow.
  • Mrs. Lyon will go over the notes we took today in class tomorrow.

Here's how far B block got today:

The Light Reactions

Light is electromagnetic energy and it behaves as though it is made up discrete particles called photons--each of which has a fixed quantity of energy.

Substances that absorb light are called pigments, and different pigments absorb light of different wavelengths. Chlorophyll is a pigment that absorbs not only red and blue but also green. This is why we see summer leaves as green.



Sunlight encompasses a broad spectrum of light, most of which is not absorbed by chlorophyll. O
nly certain wavelengths of light spectrum are utilized in providing plants with energy. This is the spectrum of light absorption for chlorophyll, as you can see the rate of absorption is highest in the red and blue area, whereas it is lowest in the green. The green light is reflected back, giving us the leaf color we see.






When chlorophyll absorbs light energy in the form of photons, one of the molecule’s electrons is raised to an orbital of higher potential energy. The chlorophyll is then said to be in an “excited” state.


Photons of light are absorbed be certain groups of pigment molecules in the thylakoid membrane of the chloroplasts. These groups are called photosystems. Photosystems have an antenna complex made up of chlorophyll molecules and caretenoid molecules (accessory pigments in the thylakoid membrane); this allows them to gather light effectively.


There are two photosystems in the thylakoid membrane that are important to photosynthesis-- photosystem I (PSI) and photosystem II (PSII). Each of these photosystems has a reaction center (the site of the first light-driven chemical reaction of photosynthesis)



Here are the major steps of the light reactions of photosynthesis:
  1. Photosystem II absorbs light in the 680 nm wavelength range. An electron in the reaction center chlorophyll (called P680) becomes excited and then is captured by a primary electron acceptor. The reaction center chlorophyll is oxidized and needs an electron.
  2. An enzyme supplies the missing electron taken from photolysis water (the splitting of water) to P680; what is split in the process, and a free oxygen is created-- this oxygen combines with another oxygen to form O2
  3. The original excited electron passes from the primary electron acceptor of photosystem II to photosystem I through an electron transport chain.
  4. The energy from the transfer of electrons down the electron transport chain is used to phosphorylate ADP to ATP in the thylakoid membrane, in a process called noncyclic photophosphorylation. Later this ATP will be used as energy in the formation of carbohydrates, in the dark reactions, or the Calvin cycle.
  5. The electrons that get to the end of the electron transport chain donated to the chlorophyll in the P700 in photosystem I. (this meeds for an electron be PSI is created when light energy excites an electron in P700, and that electron is taken up by the primary acceptor of photosystem I).
  6. The primary electron acceptor of photosystem I passes along the excited electrons to another electron transport chain, which transmits them to ferredoxin, and then finally to NADP+, which is reduced to NADPH, the second of the two important light-reaction products.

An alternative to noncyclic electron flow in cyclic electron flow. While non cyclic electron flow produces nearly equal quantities of ATP and NADHP, the Calvin cycle reactions use more ATP than NADPH. In the cyclic electron flow, photosystem II is bypassed, and the electrons from ferredoxin cycle back to a portion of the electron transport chain of PSII and its cytochromes and the to P700. Neither NADPH nor oxygen is produced, but ATP is still a product. This process is called cyclic photophosphorylation. Cyclic photophosphorolation can occur in some photosynthetic bacteria.



The Calvin Cycle

In the course of the Calvin cycle, CO2 is converted to a carbohydrate called glyceraldehyde-3-phosphate (G3P), and ATP and NADPH are both consumed. But in order to make one molecule of G3P, the cycle must go go through three rotations and fix three molecules of CO2.

These are the steps of the Calvin cycle:


  1. The three CO2 molecules are attached to three ribose biphosphate molecules (RuBPs); these reactions are catalyzed by rubisco to produce an unstable product that immediately splits into two three-carbon compounds called 3-phosphoglycerate
  2. 2.) The 3-phosphoglycerate molecules are phosphorylated to become 1, 3-diphosphoglycerate
  3. Next NADPHs reduce the 1, 3-diphosphoglycerates to create glyceraldehyde-3-phosphates (G3P)
  4. Finally the RuBP is regenerated as the 5 G3Ps are reworked into 3 of the starting molecules, with the expenditure of 3 ATP molecules

The results of the Calvin cycle (which produces one G3P molecules for each trip through the cycle) are that:

  • 9 molecules of ATP are consumed (to be replenished by the light reactions)
  • 6 molecules oh NADPH are consumed (also to be replenished by the light reactions)
  • The G3P that was created is later metabolized into larger carbohydrates
Review Questions:

1. The final product of the Calvin cycle is

A) RuPB
B) PGA
C) ATP
D) G3P

2.) Colors of light most useful in photosynthesis are

A) green, yellow, and orange
B) red, violet, and blue
C) infrared, red, and yellow
D) red, white, and blue

3.) The pigment molecules responsible for photosynthesis are located in the

A) mitochondria
B) cytoplasm of the cell
C) stroma of the chloroplast
D) thylakoid membrane of the chloroplast
E) all of the above

4.) Which of the following occurs during the light-dependent reactions of plants?

A) electron transport
B) chemiosmosis
C) splitting of water
D) all of the above
E) none of the above

5.) Production of one molecule of 3-phosphoglyceraldehyde requires how many turns of the Calvin cycle?

A) 1
B) 2
C) 3
D) 6
E) 12


The answers are D, B, D, D, C.



Tuesday, December 9, 2008

Chapter 10

Photosynthesis in Nature
In plant cells, chloroplasts capture light energy from the sun and convert it to chemical energy that can be stored in sugars and other organic com
pounds. This process is called photosynthesis.

Chloroplast






- Stroma = Matrix

Chloroplast are plant cell organelles that are mostly located in the cells that make up the Mesophyll tissue, which is part of the plant's leaf. The exterior of the lower epidermis of the leaf cell contains many tiny pore called stomata, through which carbon dioxide can enter and oxygen can exit the leaf.

Mesophyll Stomata









Chorolplasts have an outer membrane and an inner membrane. Inside the inner membrane is the stroma, which is a dense fluid filled area. Within the stroma (matrix) is a vast network of innerconnected thylakoid membranes, inside which lies the thylakoid space (space between the thylakoids).

Chlorophyll is located in the thylakoid membranes and is the light-absorbing pigment that drives photosynthesis and gives plants their green color.

Chloroplast Analogy

  1. Granum = Stack of pancakes

  2. Thylakoid = Individual pancake

  3. Stroma = Syrup

Photosynthesis Reaction

6CO2 + 12H2O + Light energy --> C6H12O6 + 6O2 + 6H2O

Plants can produce organic compounds and oxygen (O2) using light energy, carbon dioxide (CO2), and water (H2O). The 2 main parts of photosnythesis are:

  1. Light reaction
  2. Calvin cycle

In the light reactions of photosynthesis, solar energy is converted to chemical energy. Light is absorbed by chlorophyll and drives the transfer of electrons from water to NADP+ (to create NADPH), which stores them. Water is split during the course of these reactions, and O2 is given off. The light reactions also produce ATP from ADP in photophosorylation. The net products of the light reactions are NADH (which stores electrons), ATP and Oxygen.
















- Net product = NADPH, ATP, Oxygen

In the Calvin cycle, CO2 from the air is incorporated into organic molecules in carbon fixation. The fixed carbon is then used to make carbohydrates. NADPH is used to power carbon fixation. The Calvin cycle also uses ATP in the course of its reactions.

Differences between Cellular Respirations and Photosynthesis

Cellular Respiration Photosynthesis

3 main parts of whole cycle 2 main parts of cycle

- Glycolosis - Light Reaction

- Krebs Cycle - Calvin Cycle

- Chemisomoses

C6H12O6 (oxidized) + O2--> H2O + CO2 H2O + CO2 --> C6H12O6 (Reduced) + O2

Catabolic (break down) Anabolic (build up)

- release ATP - produced ATP

NAD+ oxidized --> NADH NADP+ reduce --> NADPH

- reduced charge

Mitochondria Chloroplast

Glycolysis & Krebs Light Reaction

- build ATP - release ATP

ETC Calvin cycle

- release ATP - break down ATP

- synthesis glucose

Eukaryotes Plants

Created by Alyssa Hamilton