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

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!

The Cell II

After covering the animal cell, I’d like to talk just briefly about a few other types of cells.  We’ll go over plant cells and prokaryote cells.

Plant cells

Plant cells are very similar to animal cells.  Major differences are that plants have a cell wall outside of their cell membrane.  The cell wall provides structure, support, and protection for the cell.  Plant cells also have chloroplasts which are an organelle used to capture sunlight energy and make glucose (food).  The chloroplasts are what give plants their green color; chloroplasts are filled with a green pigment called chlorophyll.  The last major difference is that plant cells tend to have one large, central vacuole (when present in animal cells, they are smaller) which serves to house waste and add structural support.

Prokayote cells

Prokaryotes, organisms without a nucleus (like bacteria), are even more different from plant and animal cells.  They also lack other membrane-bound organelles such as mitochondria and chloroplasts.  Prokaryotes tend to be unicellular, unlike plants and animals.  While they do have DNA, it is in the form of chromosomes you are used to seeing; it tends to be in simple circle or tangled-looking loop shape.

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