Energy!

This post has the most monstrous image I’ve made to date.  I hope it will become more popular and useful than my current heavy hitters the cell and even Louis Pasteur’s experiment of spontaneous generation, which I’ve seen make the top ranks of both Google and Bing image search!

In this image, I’ve covered energy as it passes from the sun in the form of light to the chloroplast of plants. In the chloroplasts, there are structures called thylakoids where the magic happens. This is where photosynthesis takes place in two parts, 1) light-dependent reactions and, 2) Calvin Cycle.

The waste products here are eliminated and the useful products are then sent to the mitochondria.  The first step is 1) glycolysis, followed then by 2) the Krebs cycle (also called the Citric Acid Cycle) under aerobic conditions OR, 2) fermentation (under anaerobic conditions)

There’s a LOT of stuff that happens here. These are the basics.  This stuff can get extraordinarily complicated–the guy the Krebs cycle is named for won a Nobel prize for his work!

I’ve never, personally seen an image that attempted to go from the sun to photosynthesis to cellular respiration but I tried to keep it as simple as possible. That said, if you feel something’s missing, its probably because it is. Some steps weren’t explicitly mentioned for simplicity’s sake.

One final note: ATP gives you a burst of energy. If you need energy to do anything for longer than about a minute and a half, you want sugar. Sugars provide longer-lasting energy.  ATP (which makes up about a half-pound of your total body weight) doesn’t store, in other words, it gets used shortly after it’s made. ATP actually gets recycled over 1,000 times a day by humans!

Energy path thumb

Click for full size

Scientists finish a 53-year-old classic experiment on the origins of life

Harold Urey, circa 1963

Urey, circa 1963. Image via Wikipedia

Sometimes an article is so well written that you can do nothing to better it.  Ed Yong is the type of writer to consistently put out articles of that quality-level.

And so all I can do is send you to his blog, for you to read for yourself.

It concerns the Urey experiment on possible origins of life, meticulous science, and more than 50 years of advances around undisturbed samples.

Read all about it here.

Photosynthesis

Previously you read about autotrophs and heterotrophs.  The difference being in the way they obtain energy.  Plants are autotrophs, and today I’d like to focus on how plants get the energy they need.

Plants need the following things to get energy to live:

  • Water (H2O)
  • Carbon Dioxide (CO2)
  • Sunlight

The process of converting H2O and CO2 in the presence of sunlight into energy is called photosynthesis.

In order for the water to get to the leaves of a plant where photosynthesis takes place, it is absorbed from the surrounding ground through roots and is brought up through tissue like your blood vessels.

The carbon dioxide is absorbed my the leaf directly through openings (or pores) on the under side of the leaf.

Light-absorbing molecules called pigments capture sunlight for the plant.  The primary pigment in plants is called chlorophyll.  Chlorophyll gives plants their green color because it absorbs reds and blues and reflects green!

Chlorophyll is housed in organelles called chloroplasts.  This is where photosynthesis takes place.

The equation for synthesis looks like this:

6CO2 + 6H2O (in the process of light) -> C6H12O6 + 6O2

carbon dioxide (in) + water (in) -> glucose (used for energy) + oxygen (out)

(That’s the same oxygen we need to breathe!!!)

All that happens in plants which are pretty fascinating, even if they aren’t furry and cuddly!

Energy

Every organism needs energy to live.  But where does that energy come from?  Let’s find out…

There are two types of organisms: autotrophs, which make their own food, and heterotrophs, which must consume food from an outside source.

Most autotrophs convert light energy from the sun into usable energy.  These are the only types of autotrophs you need to be concerned with for now.  Your typical autotroph would be any plant, a grass, a tree, a shrub.  Unicellular organisms can be autotrophs too!

Examples of heterotrophs include animals, such as yourself or a lion, as well as fungi plus some unicellular organisms like some protists or bacteria.

Energy comes in many forms.  We already mentioned light energy from the sun.  There’s also heat energy and other types like the electricity that powers your television.

The type of energy that cells can best use is chemical energy.  Specifically it’s in the form of a chemical called ATP.  Really the only thing you need to know is that ATP is like a fully charged battery.  A bond is broken and energy is released. That turns ATP into ADP.  Or you can think of it like this A3P =>release of energy => A2P.  ADP is like a battery waiting to be recharged.

ADP + Engery stored = ATP

For some reason this seems to really trip people up.  If you have any questions, drop me a comment or a tweet @AmoebaMike.

What is Life? II

To go just a little further in depth as to what we meant last time when we discussed the characteristics of living things, I wanted to make a follow up post.  I’ve been putting this off, but it’s time to bite the bullet.

  • All living things are made up of 1 or more cells.  Cells are the basic unit of life.  Most are smaller than you can see with the naked eye, but they are composed of different parts called “organelles” that work together to allow the cell to function and reproduce.
  • All living things reproduce.  Reproduction creates offspring, which are similar, but not identical to the parent(s).  Reproduction can be sexual (two parents) or asexual (one parent).
  • All living things are based on a genetic code.  Usually that code is DNA (but sometimes RNA in the case of some viruses, which remember are technically not living), which is a molecule that tells your cells what to do in order to function.  Essentially the genetic code is a set of instructions for your cells.
  • All living things grow and develop.  Some organisms simply grow larger and prepare for reproduction.  Other organisms may develop legs or wings for movement, or teeth for chewing, or breasts for feeding their young.
  • All living things obtain and use energy.  Just as you need food, so do plants, fungi, and even bacteria.  The sum of all chemical reactions to build up and break down materials is called metabolism.
  • All living things respond to their environment.  A stimulus is a signal to which an organism responds.  When you get pollen in your nose, you sneeze.  When soil is moist and warm, a seed germinates.  When you turn on a light, roaches run away!
  • All living things maintain a stable internal environment.  No matter what goes on outside the body, all organisms keep their internal conditions stable.  The process to do this is called homeostasis.  When you get cold, your body tries to keep your internal temperature from dropping too much.  So you begin to move involuntarily.  We call this shivering.  Likewise, if you’re too hot, you’re body sweats to cool you off.

What is Life?

If Biology is the study of life, how do we define life?  Is there one characteristic that defines all life?  If you ask a room of students “how can you tell if something is alive” you’ll hear things like “poke it with a stick and see if it moves.”  Unfortunately, that isn’t right.  In fact, there is not one characteristic that defines all life.  Living things are defined by a few characteristics.

All living things:

  • are made up of 1 or more cells.
  • reproduce.
  • are based on a genetic code .
  • grow and develop.
  • obtain and use energy.
  • respond to their environment.
  • maintain a stable internal environment.

Even nonliving things can meet some of these descriptions, so it’s important to be able to tell living from nonliving. For example, a car obtains and uses energy and maintains a stable internal environment.  Some can even respond to their (external) environment!  To be defined as living an object must meet ALL of these requirements.

Technically, viruses don’t meet this description of life and many scientists don’t  consider them to be living things.  However, since they act like living things, they are studied under the umbrella of biology in a field either specifically called Virology or as a broader biology field called Microbiology.

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