Light and Dark Reactions

     Plants and fungi do not eat other organisms to supply their energy.  Instead, they have evolved to use water, carbon dioxide, and sunlight in a process called photosynthesis to make their energy, as shown in picture of basic photosynthesis.  The basic equation of photosynthesis is 3 CO₂ + 3 H₂O --> C₃H₆O₃ + 3 O_3.  

     Photosynthesis happens in two major parts: the Light Reaction, and the Dark reaction.  The light reaction requires sunlight and involves the absorption of light energy, and the conversion of light energy into chemical energy.  The dark reaction, also known as the Calvin Cylce, does not require sunlight and is the process that takes the chemical energy and stores it in the form of usable glucose.

     Plant cells have chloroplasts in them (refer to picture), which consist of groups of stacked thylakoids surrounded by a membrane.  The space surrounding the thylakoids is called the stoma.  Embedded in the membrane of thylakoids is chlorophyll, a green pigment that absorbs light.  Chlorophylls form two types of clusters, called photosystems (PS) I and II. (shown in picture)

     When sunlight comes in contact with a plant, photons from the sunlight hit the chloroplast to start the light reaction.  Solar photons take only eight minutes to reach plants from the sun.  When electrons attached to a chlorophyll are stuck by a photon, they become excited.  These electrons are then so excited that they are transferred from one PS II to one PS I.  An electron transport system is formed between the photosystems, and more electrons are transferred.  Water is oxidized into O₂ and H⁺ in an enzyme by PS II.  Electrons are also formed in the oxidation that replace the electrons lost in the transferring of electrons.  The protons (H⁺) made in the oxidation process accumulate in the thylakoid space, making a difference in the concentration gradient.  When electrons reach PS I, NADP⁺ is reduced to NADPH, which is used later in the Calvin Cycle.  The difference in concentration gradients of protons causes potential energy to build up, and then protons are forced through the ATP synthase, which reduces ADP to ATP.

    The Calvin Cycle (shown in picture) uses the NADPH and the ATP created in the light reaction, along with some carbon dioxide to form sugars that the plant or fungi can use.  To start the calvin cycle, three carbon dioxides are combined with three 5-carbon sugars (RuBp) with the help of the catalyst rubisco, which immediately split into six molecules of a 3-carbon acid.  This first phase is known as Carbon Fixation.  Next, the six 3-carbon acids are rearranged with the energy from one ATP and one NADPH and creates G3P.  One G3P is half of a glucose.  Then, the remaining 5-carbon sugars are rearranged with the help of ATP to create more RuBp, which joins with other carbon dioxides to continue the Calvin Cycle.
     The rate of photosynthesis depends on light levels, water levels, nutrient levels, temperature, and carbon dioxide availability.

Extra Information:
http://www.johnkyrk.com/photosynthesis.html

Cellular Respiration

     In biology class Annie and I made a stop motion to show how cellular respiration works.  We used candy to represent different molecules.   Creating this project really helped me understand the confusing processes of cell respiration and also to learn all the details of it.  We had a lot of fun making this video and I hope you enjoy it!

Lionfish Invasive Species

     Recently, lion fish have invaded the florida keys and have been wrecking havoc there.  This prezi explains how the lion fish invaded, and also the extent of the damage they have caused.

     This video from the New York Times shows how some people are trying to put an end to this invasive species.


For more information:
http://www.miamiherald.com/2010/02/07/1468635/lionfish-invade-the-keys.html
http://www.usnews.com/science/articles/2010/04/23/lionfish-invasion-continuing-to-expand.html?s_cid=related-links:TOP

Krebs Cycle Explained

The Krebs Cycle is the second step in cellular respiration.  From one pyruvate, 3 CO2, 4 NADH, 1 FADH2, and 1 ATP are produced.  

Glycolysis Explained

This is a sketchfu showing how glycolysis works.  Glycolysis is the first step in cellular respiration, a decomposition pathway that provides all cells with energy.  Glycolysis requires one molecule of glucose and 2 molecules of ATP.  The outputs of Glycolysis are 2 pyruvates, a net gain of 2 ATP, and 2 NADH.

Caffeinated Alcoholic Drinks are Dangerous

     On November 17, 2010, the F.D.A. decided that caffeine is an illegal additive to alcoholic drinks.  The F.D.A. particularly condemned the drink Four Loko, a drink that is 12 percent alcohol by volume and has up to 156 milligrams of caffeine per can.  (equivalent to 4 shots of liquor and 3 cups of coffee)  The F.D.A. research over the past year has proven that people who drink these caffeinated alcoholic beverages are more likely to become intoxicated.  The caffeine masks the effects of alcohol, and leads people to "a state of wide-awake drunk".  This causes them to consume more alcohol without passing out, and do crazy things resulting in hazardous and life-threatening situations.
      Four Loko has caused several deaths in the past months.  Students at Ramapo College in Mahway, M.J., and Central Washington University in Ellensburg, Wash. who drank this beverage ended up in emergency rooms with high levels of alcohol poisoning.
     The F.D.A. issued warnings to fourteen major companies that produce these caffeinated alcoholic drinks, urging them to take their products off the shelves.  Many colleges have banned Four Loko.  A few states, including Michigan and Washington have also banned the drinks.  Other states are following them.



For more information:
http://www.hedgefundlive.com/blog/blackout-in-a-can
http://www.nytimes.com/2010/11/18/us/18drinks.html?ref=science
http://southfield.injuryboard.com/defective-and-dangerous-products/caffeinated-party-brew-banned-in-several-states.aspx?googleid=286270

Osmoregulation in Adelie Penguins

     Adelie Penguins (shown in video below) live in Antarctica, with no access to fresh water.  Their diet is largely made up of marine invertebrates, mostly krill.  Because these penguins require lower salt concentrations in their bodies than their surroundings, they need to regulate the levels of salt and water in their cells, or their osmotic concentration.  This is called osmoregulation.

       An Adelie penguin's salt levels are lower than that of its environment, and this causes a concentration gradient that favors the influx of salt.  They also must drink salt water to obtain the water they need.  In order to get rid of the extra salt, the penguins developed a mechanism called the salt gland.  The salt gland lies in the skull of the penguins.

     This picture from http://digimorph.org/specimens/Pygoscelis_adeliae/ shows where the salt glands are located in the skull of the Adelie Penguin.  Salt diffuses into blood cells, and salt ions (Na⁺ and Cl^-) in the blood are removed by the sodium transport mechanism (the sodium potassium pump).  These salt ions are moved to the salt glands where they are secreted into a highly concentrated salty solution and "sneezed out" by the penguins.
     Salt glands are also found in other marine birds, marine reptiles, and sharks.  Without them these organisms would not be able to drink saltwater without becoming dehydrated. 


Information from:
https://elibrary.unm.edu/sora/Auk/v114n03/p0488-p0495.pdf
http://www.cartage.org.lb/en/themes/sciences/zoology/animalphysiology/osmoregulation/osmoregulation.htm