Cellular Respiration and Fermentation

on a sunny day you might decide to go for a run outside you feel up for your run by eating a healthy breakfast maybe a piece of fruit but how does your body take this fruit and turn it into energy today we will learn about two processes that the cells in your body use to make energy the first is cellular respiration and the second is fermentation by the end of this video you will be able to tell these processes apart and even predict which processes occur based on a given organisms environment your body produces energy during a process called cellular respiration cellular respiration all starts with glucose a sugar breaking down the glucose through the various steps of cellular respiration yields adenosine triphosphate or ATP which is used as a source of energy for various cellular functions ATP contains 3 phosphate groups and energy is released when one of the phosphate groups is taken off of this molecule leaving adenosine diphosphate or ADP cellular respiration turns adp into ATP by adding back the third phosphate group this stores energy in the bonds of the molecule so that the cell can later use this energy to perform its functions cellular respiration has three steps glycolysis the citric acid cycle and the electron transport chain the first step in cellular respiration is glycolysis this step takes place in the cytoplasm of a cell during this process the cell takes a molecule of glucose and breaks it down producing two molecules of pyruvate the cell needs to use two molecules of ATP to break down the glucose however the process of glycolysis also produces four ATP so this step of cellular respiration results in a net gain of two ATP the next step of cellular respiration is the citric acid cycle this step takes place in the mitochondria the mitochondria are organelles known as the powerhouses of the cell because they transform the pyruvate into ATP a usable form of energy if the cell does not have mitochondria like in single-celled organisms such as bacteria this next step occurs in the cytoplasm the two pyruvates are processed producing two more ATP as well as carbon dioxide this is the carbon dioxide that we breathe out when we exhale while the pyruvates are being processed the citric acid cycle takes electrons from the pyruvate and adds them to carrier molecules that carry the electrons to the next step in respiration the cell has now in total created four ATP carbon dioxide and electron carrying molecules what else can the cell do what comes next the next and final step of cellular respiration is the electron transport chain this step occurs across a membrane either the mitochondrial membrane for organisms with mitochondria or the cellular membrane for single-celled organisms the electron carrying molecules created in the citric acid cycle release their electrons into the membrane as the electrons move along the membrane they release some of their energy to transport proteins in the membrane the energy released by the electrons powers these transport proteins allowing them to pump hydrogen ions to the other side of the membrane the electron is passed along to several proteins as a result there is a high concentration of hydrogen ions on one side of the membrane the cells in our body want the concentration of substances such as hydrogen ions to be at equilibrium in order to re-establish equilibrium the hydrogen ions want to move back to the opposite side of the membrane they move through a protein called ATP synthase the movement of hydrogen ions through this protein gives ATP synthase the power to convert ADP into ATP by adding on that third phosphate group this step can produce up to 34 ATP for your body to use as energy now that we've gone over the whole process let's talk about the different kinds of cellular respiration there are two types aerobic respiration and anaerobic respiration aerobic means that oxy is involved in the process in some way anaerobic means just the opposite oxygen is absent from the process the two processes are very similar they only differ in the final step of respiration the electron transport chain one question we have not answered is this where do the electrons go after they are passed along the membrane these electrons bind to a final electron acceptor at the end of the electron transport chain in aerobic respiration this final electron acceptor is oxygen most plants and animals including humans do aerobic respiration in anaerobic respiration the final electron acceptor is a molecule other than oxygen which differs depending on the organism for example some bacteria that live on the bottom of the ocean might use the sulphur from vents on the ocean floor as the final electron acceptor some organisms can do both types of respiration others like humans can only do a aerobic respiration still others can only do anaerobic respiration and die in the presence of oxygen remember that run you were going on at the beginning of the video well after running for a long time you begin to get tired and you're having a hard time breathing you're not getting enough oxygen so what does your body do it cannot do cellular respiration without enough oxygen to serve as the final electron acceptor your body resorts to a process called fermentation fermentation is an anaerobic process because oxygen is not required for it to occur but fermentation is not the same as anaerobic respiration the first step in fermentation is glycolysis just like in cellular respiration the cell breaks down a molecule of glucose to form two ATP and two pyruvates what happens next is where fermentation and respiration differ instead of using the pyruvates to form more ATP or electron carrying molecules as the cell does during respiration the pyruvate stay in the cytoplasm and are used to produce either lactic acid or ethanol as a result of fermentation you have used a whole mole kyoool of glucose and produced only two ATP this is significantly less efficient compared to cellular respiration which can produce up to 38 ATP per glucose molecule fermentation can result in a production of either lactic acid or ethanol a type of alcohol whether an organism carries out lactic acid fermentation or alcoholic fermentation depends on the organism humans can only perform lactic acid fermentation when you have been running for a long time and your body is not getting enough oxygen your cells must resort to using lactic acid fermentation instead of aerobic respiration to give you energy yeast cells on the other hand do alcoholic fermentation this is why yeast can be used to make alcoholic beverages such as beer we covered a lot of material today do you remember the three steps of cellular respiration can you now describe the key difference between aerobic and anaerobic respiration what about the differences between respiration and fermentation what steps to cellular respiration and fermentation have in common cellular respiration and fermentation are processes that produce the molecules we need in order to have the energy to go about everyday activities such as going for a run you

Channel: MITx Bio

Views: 46,438

Rating: 4.8981323 out of 5

Keywords: Cellular Respiration, Fermentation, ATP, Glucose

Id: vmEvzsKTRwc

Length: 8min 12sec (492 seconds)

Published: Sun Sep 28 2014