Unit 13: Biochemistry and Biochemical Techniques Respiration Unit 13: Biochemistry and Biochemical Techniques

Introduction Respiration is an important process for all living organisms. In this topic we will study the two types of respiration in Mammals.   There are two types: Aerobic (takes place in the presence of oxygen) Anaerobic (takes place in the absence of oxygen)

Aerobic Respiration Energy is generated via the following reaction. Glucose + Oxygen -> Carbon Dioxide + Water C6H12O6 + 6O2 -> 6CO2 + 6H2O

Anaerobic Respiration Energy is generated via the following reaction. Glucose -------> Lactic Acid C6H12O6 -------> 2C3H6O3

The Mitochondrion Intermembrane space Cristae Outer mitochondrial membrane Inner mitochondrial membrane 70S ribosome Matrix

The full process Respiration is not a simple one step process. It takes place in several steps, in both the cytoplasm of the cell and within the mitochondria.   The steps of aerobic respiration are as follows: Glycolysis Link Reaction Citric Acid Cycle (Krebs Cycle) Oxidative Phosphorylation and the Electron Transport Chain

ATP (Adenosine Triphosphate) At GCSE you learned that respiration ‘releases energy’ for living things to do work. That ‘released energy’ is carried in a carried in an organic molecule called adenosine triphosphate ATP.

ATP Label these groups on the molecule in your booklet

ATP This molecule has 3 phosphate groups (hence Triphosphate) The molecule is a good energy-carrying molecule as it can be hydrolysed to remove a phosphate group. This releases 30.5 KJ of energy each time. ATP + H2O -> ADP + P ΔH = -30.5 KJ/mol ADP + H2O -> AMP + P ΔH = -30.5 KJ/mol

ADP + P  ATP + H2O ΔH = +30.5 KJ/mol ATP can also reform by adding phosphate back onto ADP (Adenosine Diphosphate). This is done via a condensation reaction. Write an equation to show this. How much energy is required? ADP + P  ATP + H2O ΔH = +30.5 KJ/mol

Glyoclysis Glycolysis (meaning sugar splitting) is the first stage of respiration and involves the breakdown of glucose. It takes place in the cytoplasm of the cells. Glucose is used as it is a stable molecule containing 6 carbon atoms and many C-H bonds, which yield significant amounts of energy.

Glycolysis During glycolysis one glucose molecule yields 2 Pyruvate (pyruvic acid) molecules, which contain 3 carbon atoms each Glucose is a very stable molecule so 2 phosphate groups are added (phosphorylation) which makes it unstable and thus causes it to split. This requires an input of energy so the phosphate group is sourced from an ATP molecule.

Glycolysis

Glycolysis Questions How many ATPs are used during glycolysis? How many ATPs are made during glycolysis? State the net number produced also. Calculate the net amount of energy that is released in the form of ATP in glycolysis. Each NADH molecule produces 2.5 ATPs. Calculate the total number of ATPs produced in this process. Calculate the total amount of energy is released from (NADH and ATP) in this process.

Answers How many ATPs are used during glycolysis? Answer: 2 How many ATPs are made during glycolysis? State the net number produced also. Answer: 4 therefore NET = 4-2 = 2 ATPs

Answers Calculate the net amount of energy that is released in the form of ATP in glycolysis. Answer 2 ATPs each with 30.5 KJ Therefore 30.5 x 2ATPs = 61 KJ

Answers Answer 1 NADH makes 2.5 ATPs 2 NADHs = 2x 2.5 = 5 ATPs Each NADH molecule produces 2.5 ATPs. Calculate the total number of ATPs produced in this process. Answer 1 NADH makes 2.5 ATPs 2 NADHs = 2x 2.5 = 5 ATPs Therefore Total = 3 + 2 = 7 ATPs

Answer Calculate the total amount of energy is released from (NADH and ATP) in this process. Answer 5 ATPs x 30.5 KJ = 152.5 KJ

The Link Reaction

The Link Reaction Takes place in the Matrix in the Mitochondria. Involves Decarboxylation (CO2 removal) Forms 2 Acetyl-CoA (CoA = Coenzyme A) No ATP formed 2 NADH molecules made from 2 pyruvates

The Krebs Cycle Takes place in the mitochondrial matrix. The Acetyl-CoA produced from the link reaction enters the Krebs Cycle to produce a number of molecules.

Krebs Cycle

Krebs Cycle Acetyl-CoA combines with oxaloacetate to form Citric Acid. A series of enzyme controlled reactions took place forming: ATP NADH FADH2 (Reduced Flavin Adenine Dinucleotide) CO2 Oxalate is regenerated to allow the process to start again.

Question

Answer

Questions Each FADH2 molecule is capable of producing 1.5 ATP molecules. a) Calculate the total amount of ATPs produced (including those from NADH and FADH2) in a single rotation of the Krebs cycle and thus from a single glucose molecule. b) Calculate the total amount of energy released in the form of ATP (including those from NADH and FADH2) from the one Krebs Cycle rotation and thus from 1 glucose molecule. c) Using your knowledge of glycolysis, link reaction and Krebs cycle. Calculate the total number of ATPs (including those from NADH and FADH2) produced from 1 molecule of glucose in aerobic respiration. d) Calculate the total amount of energy in the form of ATP that is produced from 1 molecule of glucose in aerobic respiration.

Answers a) 1 ATP from Krebs Cycle 3 NADHs = 3 x 2.5 = 7.5 ATPs 1 FADH2 = 1.5 ATPs Total = 7.5 + 1.5 +1 = 10 ATPs 2 Acetyl-CoA mols in Krebs= 10 ATP x 2 =20 ATPs

Answers b) 1 cycle = 10 ATP 10 ATP X 30.5 KJ = 305 KJ 1 Glucose = 2 cycles 305 KJ X 2 = 610 KJ

Number of ATP molecules Answers c) Stage of respiration Molecules produced Number of ATP molecules Glycolysis 2 ATP 2 2 reduced NAD 2 x 2.5 = 5 Link reaction (x2) Krebs cycle (x2) 6 reduced NAD 6 x 2.5 = 15 2 reduced FAD 2 x 1.5 = 3 Total ATP = 32

Answers d) 32 ATPs formed each 30.5 KJ of energy. 32 X 30.5 KJ = 976 KJ

Oxidative Phosphorylation Takes place in the intermembrane space of mitochondria. The final step of aerobic respiration. Generates ATP from NADH and FADH2. Only takes place in the presence of oxygen.

H O H+ H H Pi H+ H+ H+ e- e- H+ H+ H+ H+ H+ NAD H Matrix O FAD H+ NAD H H Pi H+ H+ H+ e- ADP e- H+ Oxidation of reduced NAD and FAD. NAD = 3H, FAD = 2H Inter membrane space Electron carriers ATP Synthase H+ H+ H+ H+

H O H+ Pi H+ H+ H+ e- e- H+ H+ H+ H+ H+ NAD H Matrix O H+ Pi H+ H+ H+ e- ADP e- H+ Inter membrane space H+ H+ H+ H+

H Matrix Pi H+ Inter membrane space H+ H+ H+ H+ H+ H+ NAD ATP ADP Phosphorylation of ADP Inter membrane space H+ H+ H+ H+ H+ H+ H+

Note: As oxygen is found as O2, Matrix NAD H O O H+ Pi H+ H O ADP e- e- Note: As oxygen is found as O2, technically only ½ oxygen molecule is needed in the creation of 1 water molecule Oxygen is the final electron acceptor and stops electrons accumulating Inter membrane space H+ H+ H+ H+

Task You have been provided with all of the steps in the electron transport chain. You should use the information that you have just been given to put these steps into the correct order. There are 6 steps; you should write ‘1’ next to the first step, ‘6’ next to the last step and so on. EXTENSION ACTIVITY Calculate the number of ATP molecules that are produced throughout aerobic respiration.

Hydrogen atoms are released from reduced NAD and reduced FAD as they are oxidised to NAD and FAD. The H atoms split into protons (H+) and electrons (e-). The electrons move along the electron transport chain (made up of three electron carriers), losing energy at each carrier. This energy is used by the electron carriers to pump protons from the mitochondrial matrix into the intermembrane space. The concentration of protons is now higher in the intermembrane space than in the mitochondrial matrix – this forms an electrochemical gradient. Protons move down the electrochemical gradient back into the mitochondrial matrix, via ATP synthase. This movement drives the synthesis of ATP from ADP and inorganic phosphate. The movement of protons across a membrane, which generates ATP is chemiosmosis. In the mitochondrial matrix, at the end of the electron transport chain, the protons, electrons and oxygen combine to form water. Oxygen is said to be the final electron acceptor.

Anaerobic Respiration Takes place in the absence of oxygen. Therefore NADH and FADH2 cannot be oxidised during oxidative phosphorylation so they do not produce ATP. The NADH produced in glycolysis is used to reduce pyruvate into lactic acid (lactate). Causes muscle pain durring strenuous exercise.

Anaerobic Respiration

Anaerobic Respiration Pyruvate cannot enter the link reaction. Krebs Cycle halted. Significantly less energy is released. Build up of Lactic Acid causes muscle pain. The lactic acid can be oxidised back into pyruvate in the presence of increased oxygen concentration. This is called oxygen debt.

Questions Calculate the number of ATP molecules produced during anaerobic respiration. 2 ATPs no ATPs produced from NADH Calculate the amount of energy in the form of ATP that is produced in anaerobic respiration. 2 x 30.5 KJ = 61 KJ

Tasks P6 - Identify the main differences between anaerobic and aerobic glucose degradation. M4 - Compare the sites of ATP production and consumption during aerobic and anaerobic breakdown of glucose in cells. D4 - Evaluate the regulation of glycolysis in terms of energy requirements in cells.

Task 1 – P6 Produce a table that Identifies the main differences between anaerobic and aerobic glucose degradation. You should include the following details; substrates, pathways, site, energy yield, energy consumption and products.

Task 1 P6 Type of Respiration Aerobic Respiration Anaerobic Respiration Substrates Reaction Pathways Location of Respiration ATP Yield ATP Consumption Energy Yield (KJ) Products of Process

Task 2 – M4 Produce a poster/presentation that clearly illustrates the anaerobic and aerobic pathways of glucose metabolism in cells.

Task 2 – M4 You must include diagrams showing glycolysis (anaerobic and aerobic pathways), link reaction and Krebs cycle. For each process you must include: Sites of ATP, NADH and FADH2 production and consumption. The total and net amount of ATP molecules produced (including those from NADH and FADH2). The total amount of energy produced in the form of ATP (including those from NADH and FADH2) at each site. You should also include a diagram illustrating oxidative phosphorylation showing how ATP is produced. You must include the location of each process within the cell.

Task 3 – D4 Write a detailed article to evaluate the energy consumption of a sprinter and a marathon runner. Considering a single muscle cell, your discussion should refer to the effect of changing concentrations of ATP, ADP, Hydrogen ions and citrate and the subsequent effect they have on glycolysis regulation. The effect of the build up and subsequent removal of lactic acid during anaerobic glycolysis should be included.