Immune System Quiz

1. How does the immune system provide an immediate non-specific immune response?

     There are multiple ways in which the immune system can provide an immediate non-specific immune response. One way is through an inflammatory response. This occurs after tissue is damaged by bacteria, extreme pH levels, or heat. This damage causes histamine, bradykinin, and prostaglandin are released. These causes swelling because these hormones cause an overflow in the blood vessels into the damaged tissue cells.

   The other way is to use chemical barriers, which can be fatty acids, secreted antimicrobial peptides, or enzymes such as phospholipase and lysozyme. These barriers counteract the antigens in order to protect the body from getting an infection. The different reactions each of these barriers have vary greatly, for example some of react therapeutically while others attack certain polymers on the outside of invading bacteria.


      A third way is to use a complement system, which uses complement antibodies from the immune system to destroy invading bacteria. This system is made up of 25 proteins, and after the activation of a single protein, the rest become activated. This causes a release of molecules designed to target the bacteria's cell wall and cause it to implode.

2. How does the immune system activate T and B cells in response to an infection?
   
     B and T cells are types of lymphocytes found in the immune system. They are the primary defense of our immune system. T cells are broken down into "killer" T cells (Cytotoxic) and "helper" T cells and B cells are antigen receptors. The killer T cells have CD4 that is a growth stimulant so that more of these killer T cells are created. These killer T cells can target and kill toxic cells. They are activated when the T cell receptor binds with an antigen.

3. How does the immune system respond to a later exposure to the same infectious agent?

     One way is the use of memory cells (ex. T or B cells). They are called memory cells because they have devices that are specifically for recognizing specific pathogens. For example if you get the chicken pox once, you can not get it again because these memory cells will remember it and attack it extremely effectively.
     Another way is using Major Histocompatibility Complex (MHC). This is a group of molecules on the surface that bind together to prevent the pathogen from entering the system. This is split up into 3 classes.

4. How does the immune system distinguish self from non-self?

     One method is the ability to distinguish between "self markers" which exist on everybody's molecules and are unique for every individual. This allows the immune system to easily tell which molecules our part of our bodies and which are invaders.
     Another method is antigens, which are substances that set off an immune response. They do this by binding with immune receptors. This can trick the immune system very easily, because it believes that it is binding with a self cell.

http://www.youtube.com/watch?v=2-57bqFSJ1E
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Cell Respiration - Standard 9

Cell Respiration 

Throughout the past few weeks I have noticed that I have struggled a lot with understanding Cellular Respiration, and this was also evident on my most recent test. After this realization I knew I had to make extra time in my schedule to understand Cellular Respiration. I cannot simply watch a video or flip through a powerpoint to understand the material, so I have decided to type up, in my words, what cellular respiration is and how it works, and then take this information and connect it to other information.

DEFINITIONS

Oxidized - when a chemical (compound/element) is oxidized it loses electrons

Reduced - when a chemical (compound/element) is reduced it gains electrons

These play into the equation for cellular respiration: 

(C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy (ATP))

In this equation C6H12O6 becomes oxidized and becomes 6 CO2. This means that it loses electrons; This happens by Dehydrogenase which is an enzyme, and NAD+, which is a coenzyme, these transfer 1 or more protons and a pair of electrons to an acceptor. This entire first step of cellular respiration is called glycolysis, because while NAD+ is transporting electrons, the C6H12O6 is becoming pyruvic acid. This process uses 2 ATP and produces 4 ATP, so the cell gains 2 ATP from this first step alone.

The enzymes used in glycolysis and the other steps of cell respiration allow the processes to use less energy and to be done faster, and they are all created through PROTEIN SYNTHESIS!!!

Lets Review:

1st Step - Transcription from mRNA --> DNA (flashback to DNA replication)

This step occurs inside the Cell Nucleus (flashback to cell organelle projects)

First the RNA polymerase lays down corresponding RNA bases (A, U (replaces T), G, C). This creates pre-mRNA.

2nd Step - Processing 

The splicesome cuts out the introns, which is "junk DNA" or non-coding DNA. It also attaches a poly-A tail and cap. These are to protect the RNA strand from enzymes in the Cytoplasm. Instead of breaking down the important RNA information, they will break down the poly-A tail. 

2nd Step - Translation from mRNA --> Amino Acids --> peptide chain

The mRNA leaves the Nucleus through nuclear pores and enters into cytoplasm. In the cytoplasm the two pieces of a ribosome will fit together and began reading the mRNA strand from the 5'-->3' end. The strand will first enter the A or acceptor site of the ribosome. A tRNA will bind (using an enzyme) with an Amino Acid. Each different codon (3 mRNA bases) has a different Amino Acid it corresponds to. As it enters into the P site, the tRNA with the corresponding Amino Acid will begin the peptide strand. After this the mRNA will enter into the E or exit site and the process will continue until the Ribosome reads a stop codon, and will release the strand. Most of these Ribosomes are found in the Rough Endoplasmic Reticulum.

BACK TO CELL RESPIRATION:

These NAD+ are also stored energy, because they are electron carriers. This entire processes is simply moving around electrons. After NAD+ gains this electron it will be reduced to NADH. It will then transport this electron to the electron transport chain, which moves electrons through a series of small steps, rather than one gigantic step. This electron transport chain releases controlled amounts of energy for the synthesis of ATP (done by the enzyme ATP synthase). 

NEXT STEP:

Before this step can begin, Pyruvic Acid/Pyruvate must be converted to Acetyl Co A which happens by the bonding of the two carbons and co enzyme A - there are two Acetyl Co A going into the Citric Acid Cycle.

The Citric Acid Cycle takes place in the mitochondrial matrix, unlike glycolysis which takes place in the cytosol. First the two Acetyl Co A will each combine with an oxaloacetate which will form citrate. After this it breaks back down into oxaloacetate through a series of steps. This process creates NADH and FADH2 that will move electrons to the electron transport chain. The citric acid cycle or Kreb cycle will only produce 2 ATP. 

LAST STEP:

The last and final step in cell respiration is ATP Synthesis. The last two steps were known as "Substrate-level phosphorylation", however this step is known as oxidative phosphorylation. In this final phase the electrons pump protons across the inner mitochondrial membrane, then the oxygen joins with hydrogen to form water. After this the protons diffuse back into the mitochondrial matrix which causes the synthesis of 32-34 ATP.

THIS IS ME SHOWING YOU THAT I NOW UNDERSTAND CELL RESPIRATION AND CAN CONNECT IT TO OTHER THINGS WE HAVE LEARNED THIS YEAR. :)

Ghrelin

         Ghrelin is a hormone typically referred to as the ‘hunger hormone’ because it stimulates your brain to increase your appetite and your ability to store food. This hormone is produced in the PDI cells located in your stomach lining, otherwise known as the pituitary gland. After this water-soluble, 28 amino acid peptide is created, it can be released through the pancreas, small intestine, brain or stomach. It is released when there is an absence of food, and therefore an absence of energy. It has a simple neuroendocrine pathway, which allows it to attach to a sensory neuron in the hypothalamus, a small section of the brain, which is responsible for controlling appetite. Sensory neurons are neurons that convert external stimuli, such as chemical hormones, to internal stimuli. This sensory neuron will then secrete a growth hormone into the blood system. This new hormone will then connect to an endocrine cell, causing a release of a different stimulus, which eventually attach to its target effectors. This is the part of the cycle that finally causes the stimulation of appetite and increase in ability to store food. This cycle is actually called a negative feedback loop, meaning that when energy decreases, the amount of Ghrelin increases to counteract this deficit. Once a sufficient amount of food has been eaten, Ghrelin production will stop for the time being. A large amount of Ghrelin can also be caused by fasting or increased exercise.

Works Cited

Stengel, Andreas and Taché, Yvette. “Ghrelin – A Pleiotropic Hormone Secreted from Endocrine X/A-Like Cells of the Stomach.” US National Library of Medicine. National Institutes of Health, 12 Feb. 2012. Web. 27 February 2014.

"You & Your Hormones.” Society for Endocrinology, 2011. Web. 27 February 2014.

"Balancing Your Hunger Hormone." Infinity Medical Systems. 2005. Web. 1 March 2014.