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How do human cells oxidize?

  1. Aug 2, 2017 #1
    I read that cells in human body are continuously oxidized. Can you explain in layman's term what this means? Is it possible to explain cell oxidation withot reference to "electron loss." Because I cannot imagine visually how a cell can lose an electron or what that means.
  2. jcsd
  3. Aug 2, 2017 #2
    when oxygen is metabolised it get split into single atoms with unpaired electrons which seek out any molecules or other materials to share electrons, when oxygen attaches to iron it gets carried all over the body. if the lonely oxygen atom can't find a iron atom it sometimes attaches to any DNA or other molecules. The body can cope with this, but an overload of this can cause diseases such as heart disease, liver disease or even some forms of cancers.
  4. Aug 2, 2017 #3

    jim mcnamara

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    This is not at all scientific, but couched in other terms. I have omitted a lot of things, but the gist of what I have said below, mostly without special terms, should give you a start.

    Definition: a molecule is two [or more] atoms bound together by chemical bonds, attraction if you like. Some molecules have thousands and thousands of atoms. Some have as few as two. Table salt has two atoms, muscle proteins have thousands.

    Sugar molecules are central.

    There are different sugars. The one I mean when I use the word sugar below is a very important sugar is called glucose. It is sweet and found in many foods humans eat. We use glucose for energy. It is really a handy place to play with and to store energy. Plus, we can turn starches into (glucose) sugar, and fats into sugar, too. Think of energy stored in glucose as the calories sweet/starchy foods have. Another name them is carbs, short for carbohydrates. You see both words: calories and carbohydrate, on food labels all the time. Calories measure the amount of stored energy we can get from the food item.

    Cells get sugar. Cells make energy from sugar to run all of the huge number of chemical factories in the cell. To get from sugar to carbon dioxide, cells perform what is called "respiration".

    This is the respiration process: Sugar gets all of the energy chemically squeezed out of it, combines with oxygen and becomes carbon dioxide. That term, respire, is based on the people breathing. In goes oxygen and out goes carbon dioxide. We humans respire. Why? Because we are made of billions of cells. Each cell in us takes in glucose and oxygen,does the respiration chemical tricks, gives out carbon dioxide. Each cell gets energy that way. We use our lungs and circulatory system to move sugar, oxygen, and carbon dioxide around inside us, to the places they should go. Lungs and circulatory processes are powered by what? You guessed it: Respiration. Your brain is powered by what?

    The main powerhouse of each cell is found in small to large numbers inside every cell. This powerhouse thing is called a mitochondrion. This little guy charges up molecules that kind of act like batteries for the cell machinery. The mitochondrion uses energy that originally came from sugar to charge the batteries. The battery molecules recycle back and forth, carrying out energy to where it is needed, coming back in, empty, to the mitochondrion for a recharge.

    What I described works for all plants and animals as well. Some bacteria and other single celled beasties use other molecules than sugar. We do not want to go there now.
  5. Aug 3, 2017 #4
    Thanks for this great explanation. Even without knowing the details I understand that the cell takes sugar and outputs carbon dioxide. I actually see this gas when I make sauerkraut. The bacteria in cabbage "eats" the sugar in cabbage and turns it into the gas called carbon dioxide. These are the bubbles that rise up while the fermentation continues. So these bacteria, do they take the oxygen from the water in the jar? Does the cell go through a transformation after releasing the gas? How much gas can a cell or bacteria produce before "getting tired"?

    I asked this question because of the following quote. The person who wrote this was trying to say that human body is not a perpetual motion machine because cells lose more energy than they output:


    We are made of living cells. Our weakest part is that while our cells are multiplying they are also disappearing.

    We live and reproduce in an environment that contains oxides. We cannot live without oxygen but at the same time we are oxidizing. That is, we are losing electrons. It's not possible to stop this electron loss. We have to breath.

    In fact the process that makes us continue to live by burning what we eat also prepares our end by wearing us out and making us old.


    Do you agree with this description of getting old?
  6. Aug 3, 2017 #5
    I wouldn't agree with that since getting old is atributed to the shortening of chromosomes.
  7. Aug 3, 2017 #6


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    2017 Award

    There is no one single cause of aging. Aging results in and results from a variety of different factors that change in the body as one gets older. Certainly the shortening of the structures that cap chromosomes (called telomeres) have been recognized as a factor as well as oxidative damage from reactive oxygen species (i.e. free radicals). However, there are a variety of other changes that occur in the body contributing to age-related diseases such as protein misfolding (leading to diseases like Alzheimer's), DNA damage (leading to diseases like cancer), and problems with nutrient sensing (leading to diseases like diabetes). For a fairly good (but fairly technical) review of the biological factors associated with aging see the following paper:

    López-Otín et al. 2013 The Hallmarks of Aging. Cell 153: 1194 doi:10.1016/j.cell.2013.05.039

    With regard to oxidation, molecular oxygen (O2) is a very reactive molecule. In fact, if aliens were to look at Earth, one of the first signs that there was life on Earth would be the high percentage of oxygen in our atmosphere. Without something to continuously replenish the oxygen in our atmosphere, it would gradually react with substances in the environment to be locked up as oxides.

    The reactivity of oxygen is what enables our cells to generate the energy they require to function. For example, carbon-oxygen bonds are much more stable than oxygen-oxygen bonds, so anytime oxygen has a chance to form a new bond with carbon, energy is released that can be used by the cell to perform work. In this way, the conversion of sugars (with approximately one carbon-oxygen bond per carbon atom) to carbon dioxide (four carbon-oxygen bonds per carbon atom) is able to power most of what we do.

    During the process of converting sugars to carbon dioxide, however, the cell can sometimes make mistakes. After all, oxygen is (relative to other components of the cell) a very reactive molecule, so it can very easily react inappropriately to damage components of the cell. The reactive oxygen species (ROS, sometimes also referred to as free radicals) that are generated as a byproduct of cellular respiration can damage many components inside of the cell, including the DNA that stores our genetic information. This DNA damage can cause mutations that could ultimately lead to diseases like cancer. The damage to the cells can manifest in other ways, and lead to the decreased ability of those cells to perform essential functions in the body.

    This "free radical theory" of aging, however, has been undergoing a re-evaluation in the past few years. You may have heard of "antioxidants"— substances, either natural or artificial, that can sop up these free radicals before they can damage the cell. The free radical theory of aging would predict that antioxidants should have protective effects against aging and aid in the prevention of diseases like cancer. Experimental evidence about antioxidants, however, is more mixed, and in many cases changing the balance between free radicals and antioxidants in animal experiments do not seem to give results consistent with the free radical theory of aging. For example, mice that produce more ROS and show more oxidative damage do not seem to age faster than normal mice (http://physiolgenomics.physiology.org/content/16/1/29), and similarly, mice with increased antioxidant defenses do not show longer lifespans (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2667893/). While people believed consuming antioxidants could prevent cancer, some research has shown that antioxidants can make cancer worse. One theory is that low levels of ROS and oxidative damage is actually helpful to the cell in activating damage repair pathways to maintain the cell. It may be that ROS cause problems only when these natural repair pathways become overwhelmed.

    So, while we understand some of the connection between oxidation, free radicals and aging, there is still much that we do not understand (which can probably said about all aspects of aging).
    Last edited: Aug 3, 2017
  8. Aug 3, 2017 #7

    jim mcnamara

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    @Regla - do you mean shortening of telomeres? There are several hypothesis about aging. Each has some support from research. This is one.

    'nih: cellular changes in aging' -- this search will get lots of hits, even some about available grants to support research into changes in tissue function with aging.
  9. Aug 3, 2017 #8

    jim mcnamara

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    @Zeynel - in a word, no. There is not one single 'cause' of aging, but probably many.

    Interestingly, some behavioral changes associated with aging may have come from the positive effect of these behavioral changes on the probability of survival of the group. Again a very un-technical explanation follows -

    Basic concept:
    For a very long time, human social groups have slept together, in small shelters or out in the open. A group of soundly sleeping humans is probably a quick way for humans to become lion chow. Sleeping people are easy to catch. Awake people shooting arrows at a lion is not an easy way for the lion to get dinner. Or stay alive with a bunch of arrow wounds. So if there are almost always awake people, then any predator sneaking up is much more like to be spotted early on and then becomes a pin cushion.

    A recent study lends some support to the idea that changes in sleep patterns in older adults may have been something that helped groups survive better. Fewer lion attacks. The study found that over an average 24 hour period - looked at for several months - there were very tiny periods of time when everybody in an extended family group of the Hazda people was sleeping. This all-sleep period averaged 16 minutes out of a 24 hour day. This was due to grandparents going to sleep early, waking up early, and having 'fractured sleep' patterns compared to younger adults. The study did not use the term 'fractured sleep' that is a term sleep research people use. They simply described it. This wakefulness contributed a lot to more watchful, awake eyes that could spot predators at night, like lions.

    You can search for fractured sleep to see what that means, it mostly is old people waking up at odd hours of the night, staying awake for long periods, probably napping during the day to compensate.

    If you want to try to read the popular take on the research report - https://phys.org/news/2017-07-live-in-grandparents-human-ancestors-safer.html It is not too bad on terminology.
  10. Aug 3, 2017 #9
    yes I meant telomeres.
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