The Museum of Natural History

                The Museum of Natural History had so many interesting artifacts and exhibits, but the one that was most interesting to me was Early human life. Particularly, the period of the Ice Age. Don't you wonder how humans survived such harsh conditions? I know I do. Most of it has to do with Science. 

               An Ice Age occurs when there is a long term reduction in the temperature of the Earth's surface and atmosphere. This increases glaciers and ice sheets around northern and southern hemispheres. But, we still do not know what exactly causes the Ice Ages. When talking about the causes of an Ice Age, you consider atmospheric composition(gases), changes in the Earth's orbit, changes in solar output, volcanic eruptions, and tectonic plates (deals with the amount of ocean crust on Earth's surface).  During these cold periods, temperatures dropped by 9 degrees Fahrenheit. The regions that were usually cold became complete arctic environments. Sea levels were 450 deep than they are today. Areas that are now filled with water were once exposed as land. 

                                                 Extent of major glaciers at the last ice age

           Well, now your probably wondering about the animals and how they were able to survive. Many animals were brought to extinction. Humans were most likely able to survive because of their intelligence and adaptability to the environment. It is during this time that the early humans learned to hunt animals and invent new weapons. 

Recently, researchers have been studying Antarctic species. They found that the species are closer to volcanoes. Mosses, Lichens, and bugs were all found by the volcano. Dr. Aleks Terauds stated,  "The closer you get to volcanoes, the more species you find. This pattern supports our hypothesis that species have been expanding their ranges and gradually moving out from volcanic areas since the last Ice Age.” There are 16 volcanoes in Antarctica and the last time they were active was about twenty years ago. The volcanoes provided a warm area for the species. This helped scientists understand how the species survived past the Ice Age. 

For More Info:

http://www.bbc.co.uk/nature/ancient_earth/Last_glacial_period

Neurons & Nuerotransmitters

        The nervous system has a major role in controlling, sending, and receiving messages within the body. The nervous system is made up of neurons which join together to create nerves. The nerve is a fibers that sends messages to another part within your body. To help the messages go fast, the fibers are covered with a substance called Myelin. At the end of your nerve cell's, there are synaptic terminals. Within the gaps between the cells, there are neurotransmitters. A nerve impulse sends a message and then the neurotransmitters are released. The chemicals move, which sparks the neuron to start moving. But in order to send the message, the neurotransmitter needs to reach -55mV, or better known as action potential.  Once it reaches, the nerve impulses move forward and the message is sent. Sodium begins to enter the cell, while potassium leaves the cell. At the peak, Na+ channels close and K+ leaves the cell.

        Neurons come in different shapes and sizes. Some are 4 microns wide, while others are 100 microns wide. Neurons are similar to other cells in the body in that they have a cell membrane, nucleus, cytoplasm, along with all the other organelles. Now, you're most likely wondering,  'why  neurons are so special and not like any other cell?' If you were not wondering that, I'm going to tell you anyways. Well, neurons have a specific job and their structure helps get the job done. Neurons have dendrites and axons. Dendrites receive signals from the body, while axons send signals to other parts of the body. In fact, neurons communicate through electrochemical processes.
        There are two types of nervous systems, the central nervous system and the peripheral nervous system. The central nervous system is made up of the brain and spinal cord, while the peripheral nervous is made up of a network of your body parts. The peripheral system carries messages to and from the central nervous system. With the help of cranial nerves, the message is sent to different parts of your face such as your eyes and mouth.

Nerve

Here are more ways on how your nervous system works:

FUN FACT:

            Now, you know that neurons have ALOT to do with your brain. But sometimes, things get in the way of the brain functioning properly. One example is alcohol. People who drink usually stumble while walking, do not make sense when they are talking, and/or have memory lapses. This ends up affecting their coordination. The alcohol affects the chemicals needed for neurotransmitters. Neurotransmitters are usually excitatory , which means they are active in brain activity and properly performing their function, or inhibitory, which means they effect the brain negatively.  An inhibitory neurotransmitter GABA is increased and this causes the slow movements and unclear speech from the alcoholics. In addition, alcohol stops the excitatory neurotransmitter, glutamate, from being produced. With the reduction of glutamate production and the enhancement of GABA production, the brain also releases dopamine, which creates the feeling of happiness and satisfaction for the individual.

Your brain on drugs video for more info:

https://www.youtube.com/watch?v=vkpz7xFTWJo

Cellular Respiration

     What is Cellular Respiration?
  Cellular respiration is when organic molecules get together to produce energy (ATP). In cellular respiration, glucose, oxygen, and water are the reactants. The products are carbon dioxide, water, and most importantly ATP (ENERGY).

EQUATION:

       Cellular Respiration takes place in the mitochondria. There are two types of cellular respiration, aerobic and anaerobic respiration. Aerobic requires oxygen, while anaerobic does not need oxygen to perform the process. In both types, glycolysis occurs. Glycolysis occurs in the cytosol. With glycolysis, glucose and two ATP go in. The products are 2 pyruvic acids, 2 NADH, and 4 ATP. If oxygen is present, the 2 pyruvic acids go into the Krebs Cycle. The Krebs cycle occurs in the matrix of the mitochondria. Along with the 2 pyruvic acids, FAD+ and NAD+ are also going into the reaction. As a result, the products of this reaction are CO2, NADH, and FADH. Now, the NADH and FADH go into the Electron Transport Chain. In this final process, ATP is extracted from NADH and FADH. In the ETC, there is a turbine known as ATP Synthase, Due to the concentration gradient, the hydrogen ions try to meet equilibrium inside and outside the mitochondria, The hydrogens go through the ATP synthase, and bonds with an oxygen molecule creating water. ADP goes through the ATP synthase, binds with a phosphate group, and out comes ATP. During this process, about 36-38 ATP is produced.

       In anaerobic respiration, the pyruvic acid and NADH from glycolysis go to either alcoholic fermentation or lactic acid fermentation. In alcoholic fermentation, pyruvic acid and NADH go in. The products are CO2, alchohol, and NAD+. In lactic acid fermentation, the same reactants as alcoholic fermentation enter the process, but the products are lactic acid and NAD+. Then, the product NAD+ goes back to glycolysis, so the process can happen all over again. Lactic Acid fermentation is essential when you exercise. The only way you are able to keep exercising is because of lactid acid fermentation. 

Here's a video to a link that explains Cellular Respiration in more detail:

http://www.discovery.com/tv-shows/other-shows/videos/assignment-discovery-shorts-06-07-07-08-cellular-respiration.htm

Now, whats the relationship between photosynthesis and cellular respiration?

          Isn't it mind blowing that Cellular Respiration happens less than 15 microseconds? Without cellular respiration, one would not be able to survive. This process plays an essential role in the ecosystem. However, respiration in multicellular organisms require a more complex process with the respiratory system. The respiratory organs of organisms such as insects connect with their internal tissues. Similarly, respiration in vertebrates uses the circulatory system. This system holds gases between cells and organs. 
         In order to use the respiratory system, the respiratory system needs to be big enough to take in large amounts of oxygen. This happens so the organisms can take in oxygen and release waste gas. In addition, respiratory membranes need to be wet, so the gases can get across the membrane. An animal that uses this process is an earthworm. An earthworm uses its body as a respiratory organ. If you pay close attention, you probably notice that earthworms have moist outer skin. This benefits them when they go through cellular respiration. The moist surface allows oxygen to go across and go into the blood, which is present in the dense capillary snare (right below the skin). In fact, blood brings the oxygen to the body cells. When it gets to the body cells, carbon dioxide carries the oxygen to the skin capillaries. Then, they diffuse out of the body. Earthworms go through a more complex process because small animals have a high ratio of surface to volume.

            Cellular Respiration is crucial to all organisms, even though it might vary in the way it is performed. It's amazing how fast these process happen in the body. We take advantage of our every breath. In fact, we fail to realize how much our body does for us so we can live. 

Cell Membrane

Jina Joseph
AP Bio
10.3.14   

The Cell Membrane 

     The cell membrane is very important to the body. Yet, some people fail to see and appreciate the cell membrane and it's ability to keep the body functioning. Did you know that one of the earliest moments of evolution may have been the formation of a membrane that enclosed a solution? Every organism is made up of cells. All cells are contained by a cell membrane. The cell membranes are made up by phospholipids and proteins, and are sometimes known as "phospholipid bi-layer".

Above is a model of a cell membrane. The spheres are the phosphate end, which means they are soluble and hydrophilic. The extensions, also known as the tails, are hydrophobic.

      A membrane is held together by hydrophobic interactions, which are weaker than covalent bonds. The movement of phospholipids in the membrane are quick. Phospholipids, which are next to each other, switch positions about 10^7 times per second. A membrane is constantly fluid as a temperature decreases until the phospholipids create a closely packed arrangement. The membrane brings it's fluid to a lower temperature when there are rich phospholipids with unsaturated hydrocarbon tails. Due to the kinks located in the tails, unsaturated hydrocarbon tails cannot be placed closely together. 

      The cell membrane is selectively permeable. This means that the cell only allows certain things to go in and out of the cell. In fact, this is one reason the membrane is structured this way. Due to the way it is structured, there is a greater ratio of surface area to volume allowing the flow of molecules in and out of the cells at an easier way. Particles with no charge can pass through the membrane. Some molecules have charges so it is more difficult to get across the membrane. Proteins such as a channel protein and an aquaporin helps molecules to get in and out of the cell membrane. A membrane is also known a a mosaic fluid because its consists of various proteins.  Integral proteins and Peripheral proteins are two out of the hundreds of proteins in a person's body. Integeral proteins go through the hydrophobic center of the lipid bilayer, while peripheral proteins are not in the lipid bilayer, but they are appendages connected to the surface of the membrane. On the cytoplasmic side of the membrane, membrane proteins are retained in place by the cytoskeleton. On the extracellular side, some membrane proteins are connected to fibers of the extracellular matrix. The membrane alone could not provide support to the cell. 

     Diffusion is the result of thermal motion. Diffusion is the movement of molecules of any substance so that they spread out evenly into available space. Processes such as diffusion and facilitated diffusion use passive transport because there is no energy being used. The diffusion of water across the cell membrane is known as something specific, osmosis. Now this relates to the tonicity of a solution. The tonicity of a solution depends the concentration of the solution that cannot cross the membrane. Cells without walls are seen in three enviroments: isontonic, hypertonic, and hypotonic. In an isotonic enviroment, there will be no net movement. The solutes concentration is the same on the inside and outside of a cell meaning the state of equilibrium has been reached. A hypertonic solution is when there is more concentration on the outside of the cell. On the other hand, the hypotonic solution is when there is more concentration in the inside of the inside of the cell.

In a hypotonic solution, the cell can burst or result in lysed. This means that their is too much water in the cell. On the contrary, hypertonic solutions can result in cells shrinking because the solution continues to decrease.