Chapter 6 Respiration 2021 PDF

**Chapter 6** **How Cells Release Energy** - ATP powers almost every activity in the cell **all cells** - Most ATP is produced in **an Aerobic** reaction requiring oxygen - This reaction is called **AEROBIC CELLULAR RESPIRATION.** - Plants make their own food in photosynthesis and they...

**Chapter 6** **How Cells Release Energy** - ATP powers almost every activity in the cell **all cells** - Most ATP is produced in **an Aerobic** reaction requiring oxygen - This reaction is called **AEROBIC CELLULAR RESPIRATION.** - Plants make their own food in photosynthesis and they use the food for their energy - Using **AEROBIC CELLULAR RESPIRATION.** - Photosynthesis produces **O~2~** \-- plants use only about ½ of what is produced - For their respiration.... The other half... makes up the 21% **O~2~** in the atmosphere - So, all oxygen comes from photosynthesis - The cell burns food energy (sugar) in the same way your car burn gas - **A little bit at a time.** - If the cell were to burn sugar in an uncontrolled reaction - You would die - - - if a car were to burn a tank of gas in an uncontrolled reaction... - A car's engine is about 25% efficient based on the energy in gasoline - Aerobic cellular respiration is about 39% efficient - We do "good" - Where is the energy in sugar (and other foods) located?... In the **electrons** \-- - Remember ATP was used to attach the high energy in the NADPH from the light reaction - These high energy electrons were attached to the PGALs.... By Reduction in the carbon reaction - And 2 of these PGALs became sugar The ELECTRONS hold the energy.... - And respiration will rearrange the electrons in food - To produce the high energy ATPs - **The process of photosynthesis was composed of 2 reactions - the light reaction & the carbon reaction** **AEROBIC CELLULAR RESPIRATION. Is composed of 4 reactions** **Glycolysis The Transition Reaction Krebs Cycle (=Citric Acid cycle) Electron Transport system** - Only Glycolysis occurs in the cytoplasm - The other 3 reactions occur in the Mitochondria - To remind you... **GLYCOLYSIS** - This is a **universal metabolic pathway** - Found in aerobic and anaerobic organisms - And again **IT OCCURS IN THE CYTOPLASM** - **No oxygen is needed** - So at the end you have Pyruvate C~3~H~3~O~3~ - You have **used** 2 ATPs - And you have **produced 4 ATPs {or a net of 2 ATPs} and you have 2 NADHs** - If the organisms where the above reaction occurred \-\-- are **anaerobic** - **Like some bacteria and some Archea** - Or if there is no oxygen present - The reaction will not go beyond this point - Instead.... **FERMENTATION NOW OCCURS** - **Fermentation is the anaerobic method of dealing with the end products of Glycolysis** - **These end products are** - The 2 pyruvate molecules **Which can't be broken down any further in an anaerobic reaction** - **AND NADHs -- which must be converted back into NADs so they can be used again** - **Anaerobic bacteria do Fermentation all the time...** - **With various end products - - produced mostly from the Pyruvate molecules** - **Aerobic organisms do Fermentation...** - **When insufficient oxygen... prevents the continuation of Aerobic Cellular Respiration** Various products of Anaerobic Respiration in bacteria and and Saccharomyces (yeast) is a facultative anaerobe http://pbmo.files.wordpress.com/2012/10/fermentation.jpg  \*\*\*\*\*\*\*\* - **If there is oxygen** - And the organism is aerobic or has mitochondria - the rest of the reactions occurs **Glycolysis ↘ The Transition Reaction Krebs Cycle (=Citric Acid cycle) Electron Transport system** Fermentation??? Or moving on?? ### Transition Step. After pyruvate moves into a mitochondrion, it is oxidized to form a 2-cargon acetyl group + CO2 and NADH. The acetyl group joins with a coenzyme... Coenzyme A to form acetyl CoA - - this is the molecule that enters the Krebs cycle - Transition Reaction brings the 2 pyruvates into the mitochondria -- **Where everything else occurs**. - As this happens 2 CO~2~s are given off and 2 MORE NADHs are created as high energy electrons are moved to the NADs. - Now, there are two 2-carbon molecule (from the original two 3-C Pyruvate) in the matrix of the mitochondria - These two 2-carbon molecule are attached to Co Enzyme A and become **Acetyl CoA and moved into Krebs** - So we have produced a total of: 2 ATPs + 4 NADHs + 2 CO~2~ \-\-- and we are in the matrix of the mitochondria ### Energy Yield of Respiration.... This is what we are working toward.... ### Krebs cycle. In the mitochondrial matrex (1) acetyl CoA enters the Krebs cycle and (\#2& \#3) is oxidized to two molecules of CO~2~ (4, 5, 6) in the rest of the Krebs cycle, potential energy is trapped as ATP, NADH, and FADH~2~ - So, what have we used.... and what have we produced so far - **C~6~H~12~O~6~ + 6O~2~** **6H~2~O + 6CO~2~ + 36 ATPs (so far we have only 4 ATPs)** - **But we also have 10 NADHs produced and 2 FADH~2~ produced** - **These molecules are ALL carrying high energy electrons -- because they are electron carriers** - **So, what happens now??** - **We make the rest of the ATPs** - **How does this happen?** - **The electrons are released in an Electron transport system** - **Where we will create a concentration gradient of hydrogen ions** - **This gradient will be between the outside membrane of the mitochondria** - **And the membrane of the cristae** - **In a way similar to the hydrogen concentration within the thylackoids of Photosynthesis** - **And ATP Synthesaze will produce the ATPs as it allows the H^+^ across the membrane** - **One more thing....** - **At the end of the Electron transport chain** - **There are many LOW Energy electrons and hydrogen ions from the carrier molecules** - **These have to be dealt with - - and they are...** - **C~6~H~12~O~6~ + 6O~2~** **6CO~2~ + 6H~2~O + 36 ATPs** - - **We have NOT used the 6O~2~ or produced the 6H~2~O and we have only produced a net of 4 ATPs** - And as the production of the other 32 ATPs occurs - The 6 oxygens bind to the hydrogen ions and electrons and form Water ### Summary of Energy Yield of Respiration. - - - Breaking down glucose to carbon dioxide can in theory yield as many as 36 ATPs, mostly from the electron transport chain. +-----------------------+-----------------------+-----------------------+ | **GLYCOLYSIS** | 2 ATPs used | Net 2 ATP produced | | | | | | Occurs in the | 4 ATP produced | | | Cytoplasm does not | | | | require oxygen | 2 NADH produced = | | | | converted into **3 | | | | ATPs** each in | | | | electron transport | | | | system | | +=======================+=======================+=======================+ | | | 6 ATPs from the NADHs | +-----------------------+-----------------------+-----------------------+ | **TRANSITION | 2 CO~2~ s produced | 6 ATP from NADH | | REACTION** | | | | | 2 NADH produce = | | | Occurs as Pyruvate | Converted into **3 | | | enters the | ATP** each in | | | Mitochondria | electron transport | | | | system | | +-----------------------+-----------------------+-----------------------+ | **KREBS CYCLE** | 4 CO~2~ s produced | 2 ATP produced | | | | | | Occurs in the matrix | 2 ATP produced | | | of the mitochondria | | | | | 6 NADH produced = | | | | Converted into **3 | | | | ATP** each in | | | | electron transport | | | | system | | | | | | | | 2 FADH~2~ produced | | | | =Converted into **2 | | | | ATP** each in | | | | electron transport | | | | system | | +-----------------------+-----------------------+-----------------------+ | | | 18 ATPs from the NADH | +-----------------------+-----------------------+-----------------------+ | | | 4 ATP from the | | | | FADH~2~ | | | | | | | | 2 ATP are used to | | | | transport the NADHs | | | | from cytoplasm into | | | | the mitochondria | +-----------------------+-----------------------+-----------------------+ | **TOTAL:** 36 ATP | | | +-----------------------+-----------------------+-----------------------+ We don't eat just carbohydrates.... we eat proteins and fats. What happens to those? ### Energy from Proteins, Polysaccharides, and fats. Although glucose is the [primary] source of energy, cells can also use proteins, starches, glycogen, and fats to generate ATP. http://bio1151.nicerweb.com/Locked/media/ch09/09\_20Catabolism-L.jpg