Amazing Zoology

Category: Biochemistry

  • The chemistry of milk

    The chemistry of milk

    Image Credit: Compound Interest

    Milk is a complex mixture of Water, fat, proteins, minerals and other compounds. As fats and water don’t mix well, fat and water form an emulsion in milk.

    Triglycerides make up the fats in milk. These are molecules with a glycerol backbone and three fatty acid chains attached. Most common fatty acids in milk are palmitic, oleic, stearic, and myristic acids. The variations in the amounts of these acids are a consequence of what cows eat.

    Proteins are another important component in milk that gives milk its white appearance. Casein is the main type of protein among hundreds of others.

    In milk, proteins cluster together to form structures called micelles. They grow from small clusters of calcium phosphate, which held the proteins together. The micelles are on average about 150 nanometres in diameter, and are able to scatter light that hits them. This scattering gives the milk its white colour.

    Other compounds found dissolved in milk are vitamins, minerals and a sugar called lactose. Lactose is a sugar found only in milk and dairy products.

  • What makes poison dart frog resistant to their own poison?

    What makes poison dart frog resistant to their own poison?

    © Brian Gratwicke | CC BY 2.0

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    Poison Dart Frog

    Golden poison frog (Phyllobates terribilis) is one of the deadliest poisonous animals in the world. These animals are endemic to the Pacific coast of Colombia. An average one milligram of poison available in one frog is enough to kill 10-20 humans1. Indigenous people carefully expose the frog to the heat of a fire, and the frog exudes small amounts of poisonous fluid. The tips of arrows and darts are soaked in the fluid. Their deadly effect kept for over two years2. The interesting question is, what makes the frog itself resistant to this deadly poison!

    How is the toxin produced?

    These animals store Batrachotoxin, a steroidal alkaloid toxin in their skin glands. This toxin is not actually synthesized by the frogs. When these frogs are removed from their natural habitat and bred in captivity, they lose skin toxicity. This lead to the conclusion that the frogs synthesise the toxin from their diet.

    The toxicity of these frogs appear from the consumption of small insects or other arthropods. Recently it has been suggested that the toxin might be derived from a small family of beetles called Melyridae. One species of this beetle is found to produce this toxin.3

    Physiology of the toxin

    Batrachotoxins are potent modulators of voltage-gated sodium channels. They keep the sodium channels irreversibly open and depolarize nerve and muscle cells. Thus, they prevent nerves from transmitting nerve impulses and ultimately result in muscle paralysis. Heart is also susceptible and ends in cardiac failure.4

    You may be interested in New ant species discovered from the stomach of a frog!

    Why doesn’t the toxin affect the frog itself?

    To find out the reason behind batrachotoxin resistance in these frogs, researchers from State University of New York5 looked into the amino acid sequence of sodium channels in their muscles. And they found five naturally occurring amino acid substitutions. Now they tested these five mutations in rats to identify the real hero.

    Finally, they concluded that a single amino acid substitution was responsible for batrachotoxin resistance. The one substitution that remained resistant was called N1584T. In this mutation, the amino acid asparagine was replaced with threonine.5

    An equivalent asparagine-to-threonine substitution not only preserved the functional integrity of sodium channels in rat muscle, rat muscle but also rendered them highly resistant to batrachotoxin. And the interesting find is that, such resistance could evolve through a single nucleotide mutation.

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    References

    1.
    Most poisonous creature could be a mystery insect. USA TODAY. http://usatoday30.usatoday.com/news/science/wonderquest/2002-06-07-poison.htm. Published July 6, 2012. Accessed September 15, 2017.
    2.
    Golden poison frog. Wikipedia. https://en.wikipedia.org/wiki/Golden_poison_frog. Accessed September 15, 2017.
    3.
    Dumbacher JP, Wako A, Derrickson SR, Samuelson A, Spande TF, Daly JW. Melyrid beetles (Choresine): A putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds. Proceedings of the National Academy of Sciences. 2004;101(45):15857-15860. doi:10.1073/pnas.0407197101
    4.
    Phyllobates terribilis. Animal Diversity Web. http://animaldiversity.org/site/accounts/information/Phyllobates_terribilis.html. Accessed September 15, 2017.
    5.
    Wang S-Y, Wang GK.             Single rat muscle Na            +            channel mutation confers batrachotoxin autoresistance found in poison-dart frog            Phyllobates terribilis          . Proceedings of the National Academy of Sciences. September 2017:201707873. doi:10.1073/pnas.1707873114
  • Know your Mitochondria – Infographic

    Know your Mitochondria – Infographic

    © www.mitoq.com

    © www.mitoq.com

  • Why does the consumption of alcohol produce a burning sensation?

    Why does the consumption of alcohol produce a burning sensation?

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    Why does drinking alcohol feels like burning?

    Everyone ever tasted alcohol knows the burning sensation it produces. But what is actually producing this burning sensation? New research clearly throws some light into it. There was a lot of misconceptions regarding how alcohol is producing this feeling.

    These were the old theories:

    • Alcohol deprives water content out of our mucous epithelium. This drying up of mucous epithelium is producing the burning sensation. Alcohol absorbs water from tissues, but it is not the reason for the burning sensation!
    • Alcohol expands blood vessels thereby increasing he circulation, which is producing the heat. Just tasting the alcohol won’t increase blood circulation. Only after consumption of alcohol that the circulation to stomach is increased.
    • It irritates skin and produces the burning feeling. The truth is, it produces a cooling effect when comes in contact with the skin. This cooling effect is produced by fast evaporation of alcohol by absorbing the body heat.

    Here is the truth!

    There is a particular kind of protein receptor in our body called Vanniloid Receptor-1 (VR1), also known as capsaicin receptor. It is a member of ‘Transient receptor potential cation channel subfamily V (TrpV1)’ and in humans is encoded by the TRPV1 gene. VR1 is a non selective gated ion channel. It is usually activated by temperatures greater than 43 degrees Celsius, acidic conditions, capsaicin (it is the irritating compound present in chilies), etc. The activation of VR1 leads to painful burning sensation. Burning sensation produced by chilies is caused by the activation of VR1 receptors by capsaicin. TrpV1 receptors are found in many parts of the body including the taste receptors of our tongue.1

    VR1 receptor is sensitive to alcohol in a concentration dependent fashion. Particular concentrations of alcohol (ethanol) increases the sensitivity of VR1 receptors by decreasing its heat sensitivity from 42°C to approximately 34°C.2 Normal temperature inside our mouth is more than 34°C, so alcohol is prompting the receptors to perceive our own body temperature as hot! It is proved that, knocking out of TrpV-1 receptor in mice causes an increased consumption of alcohol compared to their normal counterparts.3 This is also a possible explanation for the sensitivity of inflamed tissues to ethanol, such as esophagitis, neuralgia or wounds.

    Whole thing can be summerised as

    • Alcohol activates the VR1 heat receptor in your mouth and throat.
    • Ethanol and capsaicin both bind to the VR1 receptors in your mouth, but ethanol merely makes them more sensitive.
    • Ethanol lowers the activation threshold of your VR1 receptors, which means that your own body heat causes a burning sensation.

    [cite]

    References

    1.
    Lyall V, Heck GL, Vinnikova AK, et al. The mammalian amiloride-insensitive non-specific salt taste receptor is a vanilloid receptor-1 variant. The Journal of Physiology. 2004;558(1):147-159. doi:10.1113/jphysiol.2004.065656
    2.
    Trevisani M, Smart D, Gunthorpe MJ, et al. Ethanol elicits and potentiates nociceptor responses via the vanilloid receptor-1. Nature Neuroscience. 2002;5(6):546-551. doi:10.1038/nn0602-852
    3.
    Blednov YA, Harris RA. Deletion of vanilloid receptor (TRPV1) in mice alters behavioral effects of ethanol. Neuropharmacology. 2009;56(4):814-820. doi:10.1016/j.neuropharm.2009.01.007
  • How do animals see in the dark?

    How do animals see in the dark?

    We humans can’t do anything in dark as we can’t see in dark. But many animals like cats and owls can see in dark, but how? A new TED Ed video created by Anna Stöckl, from Lund University in Sweden explains.

    How our eyes work?

    Our eyes have a photo receptive area called retina. When light, essentially photos hit retina, it produces electrical signals. These electrical signals are transmitted to the brain and there it is interpreted into an image. When there is more light, more photos arrive at our eye and we can see brighter images. When it is dark, the amount of photos reaching the eye reduces and we see really fuzzy images. So during darkness our eye adjusts itself to capture more light by increasing the size of pupil. Still we are not good at seeing in dark.

    How their eyes work?

    Animals like Tarsiers have eyes which are large as their brains. Actually, they have the biggest eyes proportional to head size among all of mammals. This large eyes help them collect more light. And more light means good image!

    Owls also have large eyes and specialised rod cells. In addition to this large eyes, owls have a layer of light reflecting system behind their retina called Tapetum lucidum. These reflect the light back to the retina, which means more light in retina.

    Cats also benefit from tapetum lucidum. This layer bounces the light back to retina and then to outside. This gives cat eyes, an astonishing glow. This is almost similar to the reflecting plates used in roads.

    Toads use a different technique. Their eyes allow as many photos to arrive and take some time to build up the image. So they are getting an updated image only in every four seconds. But it is enough to catch slow moving targets.

    Finally, hawkmoths collect information from all neighbouring photoreceptors together. It causes the loss of details and sharpness. But the interesting fact is, this ability helps them detect the colour of flowers even in dark!