One of the most important things that our cells do is cellular respiration. During respiration, our cells break down the food that we eat in order to make the energy that cells can use. This form of energy is a special molecule called ATP. Every living thing uses ATP as energy, so it is incredibly important. Without it, life as we know it would not exist.
But how do we make ATP? In this video series, we will focus on the breakdown of sugar, particularly glucose, during the process of aerobic respiration, which uses oxygen. During aerobic respiration, glucose from our food and oxygen from the air we breathe are used to make ATP. This process also makes the carbon dioxide that we breathe out and water as waste products.
Check out the equation. But before we get into the sweet details of how our cells get this done, Let's do a quick explosive demonstration to show the energy contained in sugar. Alright, so now we're going to show a quick demo showing the energy contained in sugar.
In here we have a couple teaspoons of sugar and we have a tea light candle. So I'm going to turn off the lights so you can see the explosion that happens. Alright, here we go.
Nice! So that's a lot of energy and sugar, but we don't want to release it like that in our bodies Because then we'd explode So in respiration the energy is released gradually through a bunch of steps in which glucose is broken down Each step releases a little bit of energy as electrons and hydrogens are stripped from glucose a process known as oxidation The oxidation of glucose releases the energy needed to make ATP gradually. Again, not like this.
There are several key processes that comprise aerobic respiration. 1. Glycolysis 2. The link reaction 3. The Krebs cycle 4. The electron transport chain Let's start with glycolysis. Glycolysis happens in the cytoplasm of the cell.
It literally means glucose breakdown, since that is exactly what happens. Basically, glucose, a six carbon molecule, is broken in half to make two molecules of pyruvate, a three carbon molecule. This is actually a ten step process, but we are going to focus on just four conceptual phases.
Here's how it works. Phase one. the energy investment phase or phosphorylation.
During this first phase, two molecules of ATP are invested to get the process started. You may have heard the saying, it takes money to make money. Well that's what's happening here. It takes a little ATP to kickstart glycolysis and get the process moving.
Notice that the ATP molecules transfer their phosphates to glucose. This energizes glucose and makes it unstable so that it will continue to react and get broken down. Phase 2 Lysis.
During this phase the six carbon sugar is broken in half to make two three carbon molecules. Remember lysis means breakdown or splitting so this makes sense. Phase 3 Oxidation During this phase, these remnants of glucose get oxidized, meaning that electrons and hydrogens are stripped off of them and transferred to special electron carrier molecules, making NADH. We will make NADH many times throughout respiration, so remember it. NADH will carry electrons to the final phase of respiration, the electron transport chain.
More on that later. Phase 4 ATP formation. During this phase, phosphates get transferred from our sugars to ADP, making ATP.
This makes two molecules of pyruvate and four molecules of ATP. However, because we invested two molecules of ATP at the beginning of glycolysis, our net gain was only two molecules of ATP. Our net products of glycolysis are therefore two pyruvates, two NADH, and two ATP.
All that for just two ATP. But don't worry, glycolysis is just the first phase and gets us set up for our next phases, the link reaction and the Krebs cycle, which we will check out in the next video. If you are doing the respiration interactive activity at biomanbio.com, you should now return to it and complete the tasks related to glycolysis. The link to the respiration interactive activity is in the description in case you need it.
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