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BIO chapter 7

by: Natalie Berry

BIO chapter 7 BIO 101

Natalie Berry

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About this Document

These notes cover chapter 7
Biology in Your World
Kyoungtae Kim
Class Notes
Biology, bio101
25 ?




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This 5 page Class Notes was uploaded by Natalie Berry on Sunday September 25, 2016. The Class Notes belongs to BIO 101 at Missouri State University taught by Kyoungtae Kim in Fall 2016. Since its upload, it has received 24 views. For similar materials see Biology in Your World in Science at Missouri State University.


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Date Created: 09/25/16
Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important Chapter 7: Deriving Energy from Food  Breathing and oxygen are a part of energy transfer  They are a part of a system that allows us to extract the energy that is used to put ATP together food  Remember: the body uses ATP to power activities like muscle contraction, thinking and cell repair to name a few  We need large amount of ATP to live and we use oxygen to produce most of it  If we don’t get enough oxygen to produce ATP, our bodies and minds start failing  Oxygen is not required for all energy extraction, but the essential product is ATP  Energizing ATP  Remember: ATP has 3 phosphate groups and powers a given reaction by losing the outermost of these phosphate groups  When ATP is left with 2 phosphate groups it becomes ADP (adenosine diphosphate) rd  For ADP to return to its more energized state (ATP), it needs a 3 phosphate group attached again  This requires a trip up the “energy hill” because the product (ATP) contains more energy than the reactrdt (ADP + phosphate group)  Basically getting the 3 phosphate requires energy  This energy comes from food and the energy extracted from it Energy Hill Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important  To illustrate how energy goes from food to ATP, we’ll use glucose  Glucose electrons, high in energy, go down the energy hill  They will channel off a few at a time and their downhill drop will power ADP’s transformation to ATP  The glucose electrons are transferred to several intermediate molecules while going downhill  The final molecule that will receive them downhill is oxygen  We need to breathe because oxygen serves as this final electron receptor  Redox reactions  The reason for electron transfer down the energy hill is that some substances more strongly attract electrons than others  Oxidation: when a substance loses one or more electrons to another  Reduction: when a substance gains electrons by an atom or molecule  The fact that it’s called reduction even though it’s gaining molecules is confusing, but remember that electrons are negatively charged so any substance that gains electrons loses its positivity  Oxidation and reduction don’t happen independently; if one substance is oxidized, another must be reduced  This is called a reduction-oxidation reaction, or a redox reaction  Redox reaction: the process by which electrons are transferred from one molecule to another  The substance oxidized in a redox reaction has its electrons traveling energetically downhill  Many molecules can oxidize other molecules  The term oxidation might make you think oxygen is involved in any redox reaction, but that’s not the case  Any compound that serves to pull electrons from another is an oxidizing agent  A large # of molecules are involved in energy transfer and each has a certain tendency to gain or lose electrons relative to others  This is how electrons can be passed down the energy hill:  The starting molecule is oxidized by another molecule, which in turn is oxidized by the next molecule down the hill  Electron carriers: molecules that serve to transfer electrons from one molecule to another in ATP formation  What makes an electron carriers’ job difficult is that many of the electrons they accept are bound up in hydrogen atoms  Remember: a hydrogen atom has only one electron and proton  So by transferring a hydrogen atom a molecule is transferring a single electron (bound to a proton) a redox reaction has occurred  Redox through intermediates: NAD  The most important carrier is the molecule NAD (nicotinamide adenine dinucleotide) Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important  Think of NAD as a cab that exist in 2 states: loaded with passengers or empty. The passengers being electrons  The “empty” state NAD comes in is ionic: NAD+  From what we know about ions, we see that NAD+ is positively charged so it has more protons than electrons  In a redox reaction, NAD+:  1. Picks up a hydrogen atom (one proton and one electron) and a solo electron (from a second hydrogen atom)  2. The isolated electron NAD+ picks up turns it from positively charged to neutral NAD+ NAD  3. The whole hydrogen atom takes it from NAD NADH  4. The result is that NAD+ has become NADH by oxidizing a substance (accepting electrons from a substance)  Now as NADH it is loaded with “passengers”  It proceeds down the energy hill and donates electrons to molecules that have greater potential to accept electrons  Once it drops all its passengers, it turns back into NAD+  Electron transfer through intermediate molecules like NAD+ provides the energy for most of the ATP produced  The 3 types of cellular respiration  Cellular respiration: the 3 stage, oxygen dependent (or aerobic) harvesting of energy that goes on in most cells  The molecular formula is: C6H12O6 + 36 ADP + 36P 6CO2 + 6H2O + 36ATP  The starting molecule is glucose (food) storing chemical energy, then ADP, and then inorganic phosphate molecules (the 36P)  The products of this reaction are carbon dioxide (6CO2) and water (6H2O) as byproducts and energetic ATP molecules  Respiration is divided into 3 main phases: glycolysis, the Kreb’s cycle, and the electron transport chain (ETC)  First stage: Glycolysis  First phase of energy harvesting and means “sugar splitting”  Takes place in the cytosol  Glycolysis produces only 2 ATP molecules per glucose molecule  Takes place in all living things and is sometime the only way of harvesting energy for unicellular organisms  It’s more ancient than the other 2 stages  The starting molecule is glucose and, in short, what happens in glycolysis is:  1. The one molecule of glucose has to be prepared for energy release (ATP is used for this)  2. The sugar is then split in half Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important  3. The two molecules formal each have 3 carbons (the original glucose molecule had 6)  4. After this all the pieces continue to divide into two halves  Glycolysis accomplishments 3 valuable things in energy harvesting:  It yields two ATP molecules, 2 NADH molecules, and it results in 2 pyruvic acid molecules  The pyruvic acid molecules are the derivatives of the original glucose molecule  Now they are the molecules that will be oxidized in the next stage  2 ndstage: the Kreb’s cycle  The pyruvic acid that resulted from the glycolysis still has a lot of energy left over that will be harvested in the Kreb’s cycle  The first product of this cycle is citric acid  This cycle serves to set the stage for the big harvest of ATP in the ETC by stripping our molecules of pyruvic acid of their electrons and sending them to the ETC  The site of harvesting for this cycle is the inner compartment of the mitochondrial membrane  There is actually a transition step between glycolysis and the Kreb’s cycle where the pyruvic acid combines with the substance coenzyme A forming the substrate acetyl coenzyme A (acetyl CoA)  In the first step of the Kreb’s Cycle CoA combines with a substance called oxaloacetic acid to make citric acid  After the CoA molecule transforms into various molecules, it’s oxidized by electron carriers and sent to the ETC rd  3 stage: The electron transport chain (ETC)  Takes place in the inner membrane of the mitochondria  (to get an image of the difference between the inner mitochondrial membrane and the inner compartment of the mitochondrial membrane, check out figure 7.9 in the text)  The “links” in this transport chain are a series of molecules  This is the destination of electron carriers like NADH  Electron carriers donate electrons and hydrogen ions (H+) to the ETC on their way down the energy hill  There are 3 large energy complexes in the ETC  Regarding ATP harvesting the ETC, since we’ve only talked about electrons  In the first enzyme complex the movement of electrons through it is enough to power the movement of hydrogen ions through the complex  This pushes them from the inner compartment into the outer compartment  By the time the electrons are done moving through the ETC, the pumping of hydrogen ions will happen with the other two enzyme complexes  These hydrogen ions are being pumped against their concentration and electrical gradients Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important  Basically the ions are being pumped up the energy hill with energy supplied by the downhill fall of electrons through the ETC  The hydrogen ions that have been pumped into the outer compartment move back down their gradients into the inner compartment through an enzyme called ATP synthase  ATP synthase is driven by the hydrogen ions flowing through it which causes it to rotate  Kind of like a waterwheel but replace the water with hydrogen ions  It is this energetic spinning that puts the 3 phosphate on ADP  ATP synthase: an enzyme that functions in cellular respiration by bringing together AFP and inorganic phosphates to make ATP  Other foods, other pathways  Basically different nutrients can be channeled through different pathways in cellular respiration in accordance with the needs of an organism


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