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Cellular Energy Production

Teacher/Instructor Patrick Roisen
Patrick Roisen

M.Ed., Stanford University
Winner of multiple teaching awards

Patrick has been teaching AP Biology for 14 years and is the winner of multiple teaching awards.

There are several types of cellular energy production. Plants produce energy from light through a process known as photosynthesis. Eukaryotic cells use their mitochondria to generate ATP through a process called cell respiration. Respiration that uses oxygen is called aerobic respiration while oxygen-less respiration is called anaerobic respiration.

One of the more challenging yet at the same time simplest concepts in Science is the idea of energy. What is energy? Now as I define it perhaps not as a physicist but as I define it energy is the ability to do work or cause a change and once you get what energy is you'll see why that kind of complex definition isn't really that necessary you just kind of get it after a while. What's energy? Well you guys know you've probably heard about potential energy and you know that if I have a box down on a table low like this versus up here there's a difference. Now it's the same box but by lifting it up I'm using my muscles, I'm using my own internal energy, I'm breaking down my food and I'm giving energy to the box. Now where is the energy?

It's in the box, how can I get the energy out, can I just pour it out no. But I can release that energy by dropping the box and it creates a change, it does work, it moves, it hits the table and it makes sound. These are all forms of energy, your cells in order to do the work that they need to do to stray alive every second of their existence; they need to be spending energy. Now they need to be getting it from some place and transferring it to other places. So one of the most important molecules for energy is the molecule called ATP which is short for Adenosine Triphosphate. Let's take a look at this picture over here and see what that actually means. So ATP is the Adenosine Triphosphate and what it is, is a regular RNA nucleotide and here we see nitrogenous base adenine here we see our 5 carbon sugar but instead of the normal one phosphate that you'll see in DNA or RNA nucleotide here we have 1, 2, 3 phosphates.

Hence ATP, now each these phosphates as you can see has a negative charge, if you know anything about Chemistry you know that like charges 2 negatives repel each other. So in order for this oxygen and that oxygen to be close to each other the bond between those 2 phosphates has to be pretty strong. And this third phosphate it's going in to this region of great negativity so there is a lot of strain on that bond and so very easily dink, you can break it off and it flies off kind of like one of those old sucker dart guns where you push it back load up a spring and then pull the trigger and doink, out would go the energy. When you break that third phosphate off your Adenosine Triphosphate becomes Adenosine Diphosphate and you can easily put it back on and take it back off. Put it back on take it back off, this means ATP is a very good molecule for a very temporarily transferring energy from one molecule to the next.

It's sometimes called the energy currency of the cell because it's kind of like how you do work say at MacDonald's and you build a bunch of big Macs and you sell them and you're given money little pieces of paper. You can then go Macy's and give those little pieces of paper, that money, that currency to the people at Macy's so you can get yourself a jacket. Otherwise you'd have to go to Macy's and say I would like that jacket can I make you can say 14 hamburgers for you? It's a lot more difficult, using ATP is kind of like using money. It allows you to change energy into a simple form that you can use in lots of other places of the cell. If we take a look back over here, you can see the two basic processes that involve energy in the cell, are photosynthesis and this is how new energy comes into the eco-system and aerobic respiration.

That's how the energy that was stored during the process of photosynthesis, that's how that energy is released. And if you take a look at these equations you'll start to notice some things. So the basic equation for photosynthesis once we've simplified and canceled out some of the molecules that are involved in both sides is you'll have 6 carbon dioxide molecules plus 6 water molecules plus energy in the form of light. They get combined and turn into glucose C6H12O6+6 oxygen molecules O2 gas. Aerobic respiration has C6H12O6 that same glucose plus 6O2 molecules breaks down to form 6 carbon dioxides, 6 waters and again energy only this time in the form of ATP. If you take a look of what's over here as the reactings is over here on that side as the products. The products of photosynthesis are the reactants of aerobic respiration.

These 2 processes are essentially near images of each other. So this is how plant or an algea grabs the energy from the sun and stores it temporarily in the chemical bonds of glucose. Releasing some oxygen gas as just kind of a toxic waste product. But then during aerobic respiration you can take that glucose and using oxygen gas from the air you can rip apart the glucose releasing all the energy that was stored and giving off the carbon dioxide and water that have been used in order to make the glucose originally.

Let's take a look a little bit closer here and this shows here how light energy comes in and using the chloroplast the organelles, photosynthesis that light mg is transferred into sugars like glucose and oxygen gas. In the rest of the cell whether it's a plant cell or of animal cell you'll find the mitochondria. The mitochondria and the cytoplasm together work to tear apart those sugars using the oxygen that released a bunch of ATP and give off the carbon dioxide and water. That ATP then is what powers most cellular work whether it's protein synthesis, transport of materials in or out of the cell or even mitosis. And that's how cells produce and use energy.