Metabolism Part 1: Glycolysis This tutorial will take you through the basics of glycolysis for SC 120 Click this button to move forward
Main Menu What is the purpose of cellular respiration? Not really. Some cells can perform respiration without Oxygen! Since cells are so much smaller than the body, a cell couldnt accomplish this. Cells use up energy for all sorts of activities. They need respiration for something else Thats right! The whole point of cellular respiration is to take the food you eat and make it into energy the cells can use. To provide Oxygen to the cells To bring Oxygen into the body To use cell energy To get energy from food for the cell to use
Main Menu What kind of energy is useful to cells? Food is what cells break down to make the form of energy they can use. Cells do produce water – but it doesnt give them energy Thats right! Cells move energy from one part of the cell to another in the form of ATP Sorry, cells cant get power from electricity! Food Water ATP Electricity
Main Menu In cell respiration: A cell takes a molecule of food and breaks it apart By breaking the bonds inside the food molecule, it releases energy It uses this energy to make ATP molecules Which other parts of the cell can break open to get the energy for their own use
Main Menu Its a little like cooking… Not everybody wants to eat these raw But anybody can get energy from these Clip art from Microsoft
Main Menu Its a little like cooking… Not all parts of your cell can get energy from the food you ate But when that energy is packaged in ATP, all parts of the cell can use it
Main Menu If taking energy out of the food molecules you ate and making ATP with it is like cooking, WHO ARE THE COOKS? The cooks are the enzymes that: –Break down the food molecules –Use the energy to make ATP –Get rid of the leftovers
Main Menu Your cell has many groups of cooks In a restaurant kitchen, you would have one area dealing with fish and another area dealing with pastry. Each area would have the expert cooks for that kind of food. Your cell, just like the restaurant, has different areas specialized to deal with different kinds of foods, with expert enzymes in that area.
Main Menu A major fuel for your cells is glucose H- C -O-H C CC O H- -O-H H-O H- C -O-H H C 6 H 12 O 6 H
Main Menu Two sets of enzyme cooks get energy from glucose The first set is out in the cell cytoplasm. As soon as glucose enters the cell, these enzymes grab it and chop it in half! Clip art from Microsoft
Main Menu Glycolysis Glyco = glucose lysis = breaking
Main Menu Breaking glucose in half takes some energy. The chef uses 2 ATPs worth of energy to do the chopping. Clip art from Microsoft
Main Menu But the chopping then releases enough energy to make 4 molecules of ATP. So there is a net gain of 2 ATPs from glycolysis. It also produces some leftovers – electrons that were removed from the glucose. Energy released!!
Main Menu Energy released!! Net gain of 2 ATPs One molecule of glucose (6 carbons) Two molecules of pyruvic acid (3 carbons each) AND – 4 electrons are removed
Main Menu Those electrons are a problem Electrons are dangerous to your cell. They can break other molecules, causing cell damage. So this garbage has to be put in a safe place – an electron carrier. Clip art from Microsoft
Main Menu Where will you put the electrons? Your cell has specialized molecules that act as electron carriers Their names are NAD and FAD Each carrier can carry 2 electrons Clip art from Microsoft
Main Menu Energy released!! Net gain of 2 ATPs One molecule of glucose (6 carbons) Two molecules of pyruvic acid (3 carbons each) AND – 4 electrons are removed Handed to 2 molecules of NAD
Main Menu But what will happen when all the NADs are filled? When the NADs are all filled, you will have to stop doing glycolysis. Otherwise, your cell would start to fill up with free electrons, and they would damage it.
What is the process of chopping glucose in half called? Gluco- means glucose But Genesis means making! Right! Glyco means glucose and lysis means breaking. Sorry – glyco means glucose, but gen means maker While breaking glucose can make ATP, theres a special name for the process that tells what it does. Glucogenesis Glycolysis Glycogen ATP generation Restart Quiz
What is the glucose chopped into? Very funny… Sorry – the energy released by chopping the glucose gives a net gain of 2 ATP molecules. Right! One half of a glucose is a pyruvic acid. The electrons were pulled off when the bonds in theglucose were broken – but there was a lot more in the glucose than electrons. Two lamb chops Two ATP molecules Two pyruvic acids Two pairs of electrons Restart Quiz
How many net ATPs did that make again? Right! Sorry – the energy released by chopping the glucose makes 4 ATP, but you had to use 2 to do the chopping. Thats way too high – the process uses 2 ATPs and makes 4. So whats the net gain? We wish! This is a lot more than you can get from glycolysis. 2 4 6 8 Restart Quiz
And what were the leftovers produced? Still funny… not right, but funny Hey! ATPs what we WANTED to make, isnt it? Not leftovers at all. Pyruvic acid is a byproduct, but its not a problem because your cell can eat it. Right! These electrons are a potential problem for your cell. Two lamb chops Two ATP molecules Two pyruvic acids Two pairs of electrons Restart Quiz
Where will you put those electrons? Not so much. Remember, the cell membrane is made of lipid. Polar things like electrons cant diffuse across it. Thats right! BAD, BAD idea. If you put them in the nucleus, they will damage the DNA and make the cell mutate. Thats going to cause a big problem for your cell… They diffuse out of the cell In the nucleus On the electron carriers Nowhere, they just pile up Restart Quiz
Main Menu Some terminology … When the two pairs of electrons were taken off the glucose, the glucose was OXIDIZED You can remember this by thinking of a lion, LEO: Loss of Electrons is Oxidation. Clip art from Microsoft
Main Menu Some terminology … When the two pairs of electrons were handed to NAD molecules, the NAD molecules were REDUCED You can remember this by thinking of the lion growling, GER: Gain of Electrons is Reduction. Clip art from Microsoft Sound from Wavsource:Animals
Main Menu When NAD is reduced, it becomes negatively charged Because electrons are negative, adding more of them to a molecule gives it a negative charge. This will make that molecule very attractive to positive ions like H+.
Main Menu Hydrogen ions buzz around your cell like flies They follow electrons wherever they go, the way flies follow garbage. Clip art from Microsoft
Main Menu So when electrons are handed to your NAD molecules, the H + go too. When your NAD molecules are full of electrons, they are also full of Hydrogen.
Main Menu In fact, many books write reduced NAD as NADH + H + to show that the Hydrogen ions are hanging around it.
Main Menu Now, back to glycolysis! Your enzymes were working away, chopping glucose in half and making 2 ATP for every glucose they chopped. But then, all of the NAD electron carriers got full of electrons. The cell had to stop doing glycolysis, because it had no place to put the electrons.
Main Menu This could kill your cell. If the cell cant do glycolysis, it cant make ATP! This is urgent – someone must TAKE OUT THE GARBAGE.
Main Menu What can your cell do with all those electrons? Your cell has a very clever way of getting rid of the electrons so it can keep doing glycolysis. It puts them back on the pyruvic acids!
Main Menu Energy released!! Net gain of 2 ATPs One glucose Two pyruvic acids AND – 4 electrons are removed Handed to 2 molecules of NAD, reducing them 2 electrons handed to each pyruvic acid
When NAD hands its electrons to pyruvic acid, what happens? Remember GER: Gain of Electrons is Reduction. Did the NAD gain electrons? Remember LEO: Loss of Electrons is Oxidation. Did the pyruvic acid lose electrons? RIGHT! NAD has lost electrons, and Loss of Electrons is Oxidation. Nope! The whole point of handing off the electrons was to empty the NADs so glycolysis wouldnt have to stop. NAD is reduced NAD is oxidized Pyruvic acid is oxidized Glycolysis stops Reset Question
Main Menu Energy released!! Net gain of 2 ATPs One glucose Two pyruvic acids AND – 4 electrons are removed Handed to 2 molecules of NAD, reducing them 2 electrons handed to each pyruvic acid Now the NAD is oxidized and can be used again! Glycolysis can go on!
Whats happened to the pyruvic acid? Right! Gain of Electrons is Reduction. The pyruvic acid gained 2 electrons and was reduced. Remember LEO: Loss of Electrons is Oxidation. Did the pyruvic acid lose electrons? To make glucose, you would have to stick those pyruvic acids back together. Nope! The molecule is still there, it just has two more electrons than it did before. It has been reduced It has been made back into glucose It has been oxidized It has been destroyed Restart Questions
What will the H + ions do? Hydrogen ions follow electrons. Did the NAD gain or lose electrons? Die? How could you kill an ion? RIGHT! Those H+ will follow the electrons wherever they go. H+ are polar, and cannot diffuse across the cell membrane. Stay with the NAD Die Diffuse out of the cell Restart Questions Go to the pyruvic acid
Main Menu Pyruvic acid + 2 electrons + 2 H+ Lactic acid Have you heard of LACTIC ACID? Its the stuff that makes your muscles burn when you exercise too hard.
Main Menu Energy released!! Net gain of 2 ATPs One glucose Two pyruvic acids AND – 4 electrons are removed Handed to 2 molecules of NAD, reducing them 2 electrons handed to each pyruvic acid Making 2 LACTIC ACIDS NAD is re- oxidized
Main Menu How will you get rid of the lactic acids? You know that after you exercise that hard, you sit down and pant. Youre doing that to get rid of the lactic acids and the electrons – but thats another story, Metabolism part 2. Youre done with this tutorial – go back to the menu to try another.
Main Menu References WavSource: Animals. Sound files for educational use. Retrieved April 3, 2007 from http://www.wavsource.com/animals/animal s.htm http://www.wavsource.com/animals/animal s.htm