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Metabolism Part 1: Glycolysis. This tutorial will take you through the basics of glycolysis for SC 120. Click this button to move forward . What is the purpose of cellular respiration?. To provide Oxygen to the cells. To use cell energy. - PowerPoint PPT Presentation
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Metabolism Part 1: Glycolysis
This tutorial will take you through the basics of glycolysis
for SC 120
Click this button to move forward
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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 couldn’t accomplish this.
Cells use up energy for all sorts of activities. They need respiration for something else
That’s 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
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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 doesn’t give them energy
That’s right! Cells move energy from one part of the cell to another in the form of ATP
Sorry, cells can’t get power from electricity!
Food
Water
ATP
Electricity
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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
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It’s a little like cooking…
Not everybody wants to eat these raw
But anybody can get energy from these
Clip art from Microsoft
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It’s 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
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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
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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.
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A major fuel for your cells is
glucose
H-C-O-H
C
C C
O
H-C-O-H
H-
H- -O-HH-O
H-C-O-H
HC6H12O6
H
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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
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Breaking glucose in half takes some energy. The ‘chef’ uses 2 ATPs worth of energy to do the chopping.
Clip art from Microsoft
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• 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!!
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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
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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
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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
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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
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But what will happen when all the NADs are filled?
• When the NADs are all filled, you willhave to stop doing glycolysis.Otherwise, your cell wouldstart to fill up with freeelectrons, and they would damage it.
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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, there’s a special name for the process that tells what it does.
Glucogenesis
Glycolysis
Glycogen
ATP generation
Restart Quiz
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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
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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.
That’s way too high – the process uses 2 ATPs and makes 4. So what’s the net gain?
We wish! This is a lot more than you can get from glycolysis.
2
4
6
8
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And what were the ‘leftovers’ produced?
Still funny… not right, but funny
Hey! ATP’s what we WANTED to make, isn’t it? Not leftovers at all.
Pyruvic acid is a byproduct, but it’s 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
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Where will you put those electrons?
Not so much.
Remember, the cell membrane is made of lipid. Polar things like electrons can’t diffuse across it.
That’s right!
BAD, BAD idea. If you put them in the nucleus, they will damage the DNA and make the cell mutate.
That’s 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
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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
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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 MicrosoftSound from Wavsource:Animals
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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+.
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Hydrogen ions buzz around your cell like flies
• They follow electrons wherever they go, the way flies follow garbage.
Clip art from Microsoft
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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.
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• In fact, many books write reduced NAD as
NADH + H+
to show that the Hydrogen ions are hanging around it.
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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.
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This could kill your cell.
• If the cell can’t do glycolysis, it can’t make ATP!
• This is urgent – someone must TAKE OUT THE GARBAGE.
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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!
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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
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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 wouldn’t have to stop.
NAD is reduced NAD is oxidized
Pyruvic acid is oxidized Glycolysis stops
Reset Question
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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!
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What’s 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
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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
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Go to the pyruvic acid
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Pyruvic acid + 2 electrons + 2 H+
Lactic acid
Have you heard of LACTIC ACID?
It’s the stuff that makes your muscles burn when you exercise too hard.
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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
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How will you get rid of the lactic acids?
• You know that after you exercise that hard, you sit down and pant.
• You’re doing that to get rid of the lactic acids and the electrons – but that’s another story, Metabolism part 2.
• You’re done with this tutorial – go back to the menu to try another.
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References
• WavSource: Animals. Sound files for educational use. Retrieved April 3, 2007 from http://www.wavsource.com/animals/animals.htm
