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7.1 The Importance of Cellular Respiration

7.1 The Importance of Cellular Respiration. Pg. 204-209. Introduction to Chapter 7. The primary role of photosynthesis is to convert light energy into glucose . Glucose in cellular respiration is converted to ATP.

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7.1 The Importance of Cellular Respiration

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  1. 7.1 The Importance of Cellular Respiration Pg. 204-209

  2. Introduction to Chapter 7 • The primary role of photosynthesis is to convert light energy into glucose. Glucose in cellular respiration is converted to ATP. • The glucose can be used immediately, transported or stored, or used to synthesize other energy molecules. • Plants store glucose as starch • Animals and fungus store glucose as glycogen

  3. The role of cellular respiration is to supply the body with ATP. • ATP, released from the cells of plants and animals (glucose) that store energy. ATP can then be use to conduct cellular processes. • The summarized equation is:

  4. Similar to photosynthesis, electrons move from molecule to molecule as energy is transferred. • Oxidization reaction release energy • This energy is used to make ATP • Electron acceptors in Cellular Processes are: NAD+ and FAD • Electron donors in Cellular Processes are: NADH and FADH2 • Act as electron carriers, transfer electrons through Oxidation-Reduction reactions. • The transfer of electrons releases energy that can be used in cellular respiration and other cellular processes and in the making of ATP.

  5. Pg. 205 Fig.1 The energy released from the oxidation-reduction reaction is used to attach a free phosphate to ADP to make ATP. Note that the ATP is a high-energy compound. The oxidation-reduction reaction could be the transfer of elections from high-energy compounds such as when NADH is oxidized to from NAD+ and H+.

  6. Energy, Cells and ATP • ATP supplies the energy cells require • An average cell has one billion molecules of ATP. • They are continually broken into ADP and P as they release energy to do work, and then remade into ATP • Active transport is one of the uses for ATP. • This is the movement of substances through a membrane against a concentration gradient. • This happens through proteins called “pumps” • Eg. Hydrogen protein in the thylakoid membrane

  7. Example: The sodium-potassium pump • Sodium is pumped out, potassium into the cell • Notice for every 3 Na + pumped out, 2 K+ are pumped in (pg. 206 Fig.3) • Without this pump, nerve cells and muscle cells could not function properly. Other substances, such as vitamins, amino acids, and hydrogen ions are also actively transported across membranes by specialized carrier proteins. • All of theses pumps require energy from ATP to operate.

  8. E.g. of the Importance of Cellular Respiration • This is a diagram of active transport. • Active transport. The molecule to be transported attaches to an open binding site on one side of the carrier protein. ATP is converted to ADP on the carrier protein and releases energy. The energy causes a change in the shape of the protein that carries the solute to the other side of the membrane.

  9. Other critical uses of ATP are listed below: • Large-scale motion ie muscle fibers contracting, their shape changes as the result of energy from ATP.

  10. Glucose and ATP • Glucose is relatively small and is highly soluble. Thus, it is ideal for transport between cells. (is our blood sugar) • But why do we need glucose when it is ATP that is needed to run our cells? • All cells use energy from ATP molecules to meet their metabolic energy needs. • ATP is not abundant in food and provide relatively small amount of energy. • Large molecules like sugars are used for storage of energy as well as transportation of energy. • During cellular respiration, some of the energy in glucose is converted to ATP.

  11. Glucose and ATP • A cell is like a large factory in which operations are performed by vending machines that only accept $1 coins. Inorder to perform any task (any cellular action) within the factory, you need a $1 coin. • In cells $1 = ATP, virtually all processes conducted by cells use ATP molecules only as their immediate energy source. • What happens when a $100 bill (glucose) arrives? • It is very valuable, but needs to be exchanged to $1 coins (ATP) before it can be used to run the vending machines (cellular activities).

  12. Releasing Energy • During cellular respiration, chemical bonds in food are broken and new bonds are formed. The result is a release of energy. • Yet, it requires energy to break the original bonds before the release of energy can take place. • Cellular Respiration releases more energy (ATP) than it used to break apart the reactant molecules (food).

  13. Even though glucose($100) has significantly more energy than ATP ($1), the energy is not all available for cellular use. • The conversion of glucose to ATP is only approximately 36% efficient. • 64% of the energy is lost as heat. • This seems like a lot of waste, but remember that animals and birds use this energy to keep warm.

  14. Two Types of Cellular Respiration • There are two different pathways in which glucose can be converted into ATP • The two processes are aerobic respiration and anaerobic respiration. • Aerobic Cellular Respiration uses oxygenSummarized formula:

  15. There are four stages to Aerobic Cellular Respiration : • 1. Glycolysis, 2. pyruvate oxidation, 3. The Krebs cycle, 4. The electron transport chain and chemiosmosis • Notice 36 ATP are made from one glucose! • Anaerobic Cellular Respiration does not use oxygen. (absence of oxygen) (glucose is not completely oxidized) • There are 2 types with 2 different end products

  16. For each of these processes, there are two stages: glycolysis and fermentation • Anaerobic respiration only produces 2 ATP for every glucose molecule

  17. The Importance of Cellular Respiration • Cells cannot use high-energy molecules, such as glucose, directly. Cellular respiration converts glucose into energy-containing molecules the cells can use directly, such as ATP. • Cells use ATP for their immediate energy needs. • Aerobic cellular respiration takes place in the presence of oxygen and produces 36 ATP molecules per glucose molecule. • Anaerobic respiration takes place in the absence of oxygen and produces 2 ATP molecules per glucose molecule.

  18. Homework… • Textbook: • Pg. 205 #1-2 • Pg. 207 #3-5 • Pg. 209 #1-5 • Pg. 200 #1-12,14-18 • Study for QUEST chp. 6! Its tomorrow! • Key: pg.81-83 practice Test 1 #1-13, WR1

  19. Glycolysis & Pyruvate Oxidation Pg. 210-215

  20. Aerobic Cellular Respiration • Stage 1: glycolysis—a 10-step process occurring in the cytoplasm • Stage 2: pyruvate oxidation—a 1 step process occurring in mitochondria matrix • Stage 3: the Krebs cycle—an 8-step cyclical process occurring in mitochondria matrix • Stage 4: the electron transport chain and chemiosmosis (oxidative phosphorylation) –a multi step process occuring in the inner mitochondrial membrane

  21. Stage 1: Glycolysis • Glycolysisoccurs at the beginning of both anaerobic and aerobic respiration. • Glucose can not be used directly by the cell, thus glycolysis splits the glucose in half during the first step of both types of cellular respiration. • Glycolysis is Greek for “sugar splitting”.

  22. Glycolysis

  23. You will only have to know: • 2 ATP are used & 4 ATP and in redox reactions 2 NADH are made. • One 6 carbon molecule becomes two 3-carbon molecules (pyruvates) • Takes place in the cytoplasm of the cell. ATP are now available to supply energy for cellular functions. • All ten reactions that occur in glycolysis do not require oxygen

  24. The reactants and Products of Glycolysis • The net equation for glycolysis:

  25. Glycolysis is very inefficient: • Only 2.2% of the energy from glucose is converted into ATP • Yet, the two pyruvates and two NADH are used later to produce ATP. • Some single celled organisms can live with just using glycolysis. • Multicellular organisms require more, thus the energy from the 2 pyruvates must be converted into ATP so this is the 1st step in eg. Aerobic respiration.

  26. Aerobic Cellular Respiration • Of the four stages of aerobic respiration, only the first step (glycolysis) does not need oxygen. • The next three steps: pyruvate oxidation, the Krebs cycle and the electron transport chain occur in the presence of oxygen.

  27. Glycolysis occurs in the cytoplasm, but the following stages, which produce the most ATP, occur in mitochondria, and require oxygen.

  28. Mitochondria are eukaryotic cell organelles that conduct aerobic cellular respiration • Specific reactions occur in specific areas of the mitochondria: • The Matrix is the fluid that fills the inner space of the mitochondria • Intermembrane space is the fluid filled space between the inner and outer mitochondrial membranes • of mitochondrial structure.

  29. Stage 2: Pyruvate Oxidation • This stage connects glycolysis in the cytoplasm with the Krebs cycle in the mitochondrial matrix. • Two pyruvate molecules enter this stage and are transformed into acetyl-CoA

  30. Each pyruvate that enters the mitochondrial matrix produces: a CO2, a NADH and a acetyl-CoA • The CO2 is removed from the pyruvate and released as a waste; produced here is 1/3 of the carbon dioxide that you breathe out. • Pyruvate (the 2-C) are oxidized by NAD++2H++2e- NADH. This converts pyruvate to an acetic acid group and transfers high-energy hydrogens to NADH. • The acetyl-CoA formed will be used in the Krebs Cycle & the NADH will be used in the electron Transport system

  31. Homework… • Textbook: • Pg. 212 #1-3 • Pg. 215 #1-3 • Study for Quiz pg. 210-215 Stage 1&2 • Key: Read pg. 65-68 practice Qs #11,12,15-17 • Watch 1st 2 videos (paper response) 5-7 pts each.

  32. Stage 3: Krebs Cycle & 4:ELT 7.2b Pg. 215-220

  33. Review: Act it out…  • ATP ADP + P • Energy is released. • ADP + P ATP • Energy is stored.

  34. Aerobic Cellular Respiration • Stage 1: glycolysis—a 10-step process occurring in the cytoplasm • Stage 2: pyruvate oxidation—a 1 step process occurring in mitochondria matrix • Stage 3: the Krebs cycle—an 8-step cyclical process occurring in mitochondria matrix • Stage 4: the electron transport chain and chemiosmosis (oxidative phosphorylation) –a multi step process occurring in the inner mitochondrial membrane

  35. Stage 3: The Krebs Cycle • This is an 8-step process which requires an enzyme at each step. • Reactions that transfer energy from organic molecules to ATP, NADH, FADH2, and removes Carbon atoms as CO2 • The final product in stage 8 is used in stage 1 of the cycle. The Krebs cycle occurs here

  36. The result of each cycle produces free energy as:3 NADH’s, a FADH2and an ATP. • There is also 2 CO2Created as waste. • REMEMBER 1 glucose makes two 3-C which each make two acetyl-CoA, so the Krebs cycle occurs twice for 1 glucose molecule. Products*2 • Notice that all 6 C will be oxidized to CO2 and released from the cell as metabolic waste. …What do plants need? • NADH and FADH2 go to Stage 4.

  37. Stage 4: Electron Transport and Chemiosmosis • The Electron transport system takes energy from NADH and FADH2 in a chain reaction to pump H+ into the intemembranespace of the mitochondria. • Ongoing process with countless NADHs and FADH2 (has lower electron energy) delivering e-s to the ETC continuously.

  38. The NADH and to a lesser extent FADH2 give up high energy electron to the ETC. • These electrons are passed down a number of protein pumps which push H+ through the inner mitochondrial membrane. • The build up of H+ in the intermembrane space produces a large amount of potential energy. • This system results in a transformation of chemical energy into electrochemical energy. • Note that Oxygen is the last electron acceptor in the electron transport system. (We -aerobic organisms- need Oxygen!) • The chemical energy of the electrons is converted electrochemical potential energy of an H+ ion gradient that forms across the inner mitochondrial membrane. This energy is used to make lots of ATP in chemiosmosis.

  39. Chemiosmosis & Oxidative ATP Synthesis • Chemiosmosis: a process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme. • This is the place where most of the ATP made by our bodies occurs. • This happens just like the processes found in plant cell that contain chloroplasts. • The build up of H+ in the intermembrane space produces a large amount of potential energy in the electrochemical gradient. • An ADP is converted to an ATP as H+moves across the electrochemical gradient through the ATPasecomplex (ATP synthase).

  40. One NADH pump enough H+ ions across to generate 3 ATP; One FADH2 pump enough H+ ions across to generate 2 ATP. • Energy is released in the ETC by a series of oxidations which result in the production of ATP. • Thus, the process referred to as Oxidative ATP synthesis. • ETC and Chemiosmosis need electrons (from food, ie glucose) and oxygen (acts as an electron acceptor).

  41. Aerobic Respiration Energy Balance Sheet • How much energy was transferred from glucose to ATP in the entire aerobic respiration process? • A total of 36 ATP are created in the processing of one glucose. • Can you identify where the ATP were produced? Note in Glycolysis the NADHs produced are not able to generate 3 ATP each, instead they transfer their electrons to FADswhich are used in the ETC to produce 2 ATPseach. Remember that glycolysis was 2.2% efficient, aerobic respiration is over 32% efficient, so the actual yield is about 30 ATP

  42. Aerobic Respiration Energy Balance Sheet

  43. Homework… All to hand in. • Textbook: • Pg. 219 #4-6 • Pg. 220 #1-10 • Key: • Pg. 68 Read & Qs #4,6,13,14,18,NR1, NR2, NR3

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