1 Cellular Respiration How do living things release energy???Quick Review… Most energy used thru conversion of ATP molecules into ADP molecules Thus cells must continually convert ADP molecules back into ATP molecules This process is known as………. CELLULAR RESPIRATION A working muscle cell converts ADP into ATP at a rate of about 10 million molecules per second. What is the energy source????? Chemical energy stored in food.
2 Lesson Objectives • Give an overview of glycolysis.• Name the three stages of cellular respiration. • Give an overview of glycolysis. • Explain why glycolysis probably evolved before the other stages of aerobic respiration. • Describe the structure of the mitochondrion and its role in aerobic respiration. • List the steps of the Krebs cycle, and identify its products. • Explain how electron transport results in many molecules of ATP. • Describe how chemiosmotic gradients in mitochondria store energy to produce ATP. • State the possible number of ATP molecules that can result from aerobic • Define fermentation. • Describe lactic acid fermentation and alcoholic fermentation. • Compare the advantages of aerobic and anaerobic respiration. • Compare cellular respiration to photosynthesis
3 Breathing versus Cellular RespirationBreathing: physical process that allows animals and humans to come into contact with gases in the air Cellular respiration: chemical process that releases energy from organic compounds (food), gradually converting it into energy that is stored in ATP molecules
4 Correlation between a campfire and Cellular RespirationAnalyzing a campfire can clarify your understanding of cellular respiration. A campfire breaks chemical bonds in wood, releasing stored energy as light and heat Cellular respiration breaks chemical bonds in glucose, releasing stored energy and transferring some to 38 ATP; some energy is lost as heat.
5 Chemical Pathways Food is the raw material that provides theenergy for your body to function Cells use food to synthesize new molecules to carry out their life processes
6 Cells do not BURN glucose, they slowly release energy from it and other food compounds through several pathways (processes) 1st pathway glycolysis: releases only a small amount of energy (2 net ATP) If oxygen present, it will lead to two other pathways that release a lot of energy: Krebs cycle & Electron Transport Chain If oxygen absent glycolysis is followed by a different pathway: Alcoholic Fermentation or Lactic Acid Fermentation Glycolysis Greek glucose means sweet (glucose) Latin lysis means process of loosening or decomposing Glycolysis “breaking glucose” So what would hydrolysis mean??? Breaking with water Pictures of two cells: Top animal cell Bottom plant cell What organelle is pictured on the right??? Mitochondrion
7 Overview of Cellular RespirationIn presence of oxygen (aerobic) glycolysis is followed by: ______________ ______________ Krebs Cycle Electron Transport Chain How many pathways follow glycolysis in presence of oxygen?????? TWO
8 All three combined make up Cellular Respiration: Glycolysis + Krebs Cycle + Electron Transport ChainProcess that releases energy by breaking down food molecules in the presence of oxygen Equation for cellular respiration: 6O C6H12O 6CO H2O + energy (ATP) oxygen glucose carbon dioxide + water energy 1 2 3 These happen in the presence of WHAT????? OXYGEN!!!!!!! Where does the glucose used in respiration come from? From the breakdown of carbohydrates by cells Each of these 3 stages captures some of the chemical energy available in food molecules and uses it to produce ATP
9 What is the process of glycolysis????
10 Glycolysis Process takes place in the cytosol of the cytoplasm outside of mitochondria; coverts glucose with the help of 2 ATP molecules and eventually releases 4 ATP molecules; for a net gain of 2 ATP molecules. Click to show definition of cytosol and cytoplasm for note sheets Top right corner mitochondria
11 Do Lake Nyos…
12 ATP & NADH production in Glycolysisused up become 2 ADP 2 NADH & 2 H+ produced 4 ATP produced Net gain = 2 ATP Step 1: breaks 1 molecule of glucose in half, producing 2 molecules of pyruvic acid (a 3-carbon compound) Step 2: 2 NAD+ ;electron carrier accepts 4 high-energy electrons transfers them to 2 NADH molecules and 2 H+ thus passing the energy stored in the glucose Step 3: 4 ADP added producing 4 ATP Step 4: 2 remaining pyruvic acids enter Krebs Cycle in presence of oxygen; IF no oxygen another pathway is followed Have them answer question in their packet about what else is produced? NAD+ (nicotinamide adenine dinucleotide)
13 Glycolysis is a fast process Cells produce thousands of ATP molecules in a few milliseconds Glycolysis alone DOES NOT require oxygen It can supply chemical energy to cells when oxygen is NOT available However if a cell generates large amounts of ATP from glycolysis it can run into problems a. the cell’s available NAD+ molecules become filled up with electrons b. glycolysis shuts down, cannot proceed without available NAD+ molecules c. ATP production stops
14 Anaerobic to Aerobic RespirationGlycolysis evolved before the other stages of cellular respiration; other stages need oxygen No oxygen in Earth’s atmosphere when life first evolved about 3.5 to 4 b.y.a. Without oxygen anaerobic respiration 2 or 3 billion years ago, oxygen was gradually added to the atmosphere by early photosynthetic bacteria; period the “oxygen catastrophe” aerobic organisms Bya…billion years ago Explain ‘oxygen catastrophe…no photsynthetic organisms at the time According to the endosymbiotic theory, engulfing of some of these aerobic bacteria led to eukaryotic cells with mitochondria, and multicellularity followed. After that, living things could use oxygen to break down glucose and make ATP. Today we live in an atmosphere which is 21% oxygen and most organisms make ATP with oxygen. They follow glycolysis with the Krebs cycle and electron transport chain to make more ATP than by glycolysis alone. Cellular respiration that proceeds in the presence of oxygen is called aerobic respiration.
15 Let’s look at the pathway that follows gycolysis with the presence of oxygen….. aerobic respiration
16 BUT FIRST…Mitochondrion StructureMitochondrion has two separate membranes: inner and outer membrane. Three compartments: intermembrane space, cristae space, and matrix Have them label structures in packet then do following notes: The inner membrane folds into cristae which divide the organelle into three compartments—intermembrane space (between inner and outer membrane), cristae space (formed by infoldings of the inner membrane), and matrix ( space enclosed by the inner membrane). The second stage of cellular respiration, the Krebs Cycle, takes place in the matrix. The third stage, Electron Transport Chain, takes place on the inner membrane.
17 AEROBIC RESPIRATION: The Krebs Cycle and Electron TransportEnd of glycolysis 90% of chemical energy from glucose still unused, locked in high-energy electrons of pyruvic acid Extracted by world’s most powerful electron receptor Krebs and Electron Transport require oxygen thus they are aerobic processes OXYGEN
18 The Krebs Cycle 1. 2nd stage of cellular respiration2. Named after Hans Krebs, British biochemist in 1937 3. Here pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions 4. Citric acid is the 1st compound formed in this series of reactions, so Krebs is sometimes called the Citric or Citric Acid Cycle.
19 2 turns & 2 pyruvic acid (from glycolysis) yield: Pyruvic acid enters from glycolysis; One carbon removed = CO2 formed NAD+ again changed to NADH CoA joins remaining 2 carbons = Acetyl-CoA Acetyl-CoA added to 4 carbon Compound = Citric acid (6-C) Citric acid broken down to 5-carbon then 4 carbon; more CO2 released Along the way more NADH and FADH2 formed One molecule of ATP also made 2 turns & 2 pyruvic acid (from glycolysis) yield: 10 NADH (2 from glycolysis) 2 FADH2 4 ATP (2 from glycolysis) Cycle starts anew
20 Uses for the products of the Krebs CycleCarbon dioxide is exhaled (waste product) ATP can be used for cellular activities High-energy electrons (stored in NADH & FADH2) can be used to make huge amounts of ATP in the presence of oxygen
21 ATP synthase converts ADP into ATP (DISPLAY)Electrons from Krebs cycle are passed to electron transport chain by NADH & FADH2 At end of the chain an enzyme combines electrons from the electron chain with H+ ions and oxygen to form water Each time 2 high-energy electrons transport down the electron chain, their energy is used to transport H+ ions across the membrane H+ ions build up in intermembrane space it is now positively charged, other side of membrane negatively charged (DISPLAY) Electrochemical gradient (chemiosmotic gradient) created for ATP synthase to work (OFF) ATP synthase converts ADP into ATP (DISPLAY) In eukaryotes, electron transport chain is a series of carrier proteins located in the inner membrane of the mitochondrion In prokaryotes, same chain only in the cell membrane
22 The Total ATP production of Aerobic CRHow much chemical energy comes from one molecule of glucose?? Absence of oxygen: Only 2 ATP molecules from glycolysis Presence of oxygen: 2 net ATP molecules from glycolysis 36 more ATP molecules from Krebs Cycle and electron transport These 38 ATP molecules represent 38% of the total energy of glucose, remaining 62% is released as heat, thus your body feels warmer after vigorous exercise and does not freeze in winter.
23 Let’s look at the pathway that follows gycolysis without the presence of oxygen….. anaerobic respiration
24 Anaerobic Respiration: FermentationThis occurs after glycolysis when oxygen absent, thus anaerobic process Fermentation releases energy from food molecules in absence of oxygen In this process cells convert NADH to NAD+ by passing high-energy electrons back to pyruvic acid Now glycolysis has NAD+ and can continue producing ATP There are 2 types of fermentation: Alcoholic fermentation Lactic acid fermentation
25 Anaerobic and aerobic respiration share the glycolysis pathwayAnaerobic and aerobic respiration share the glycolysis pathway. If oxygen is absent, fermentation may take place, producing lactic acid or ethyl alcohol and carbon dioxide. Products of fermentation still contain chemical energy, and are used widely to make foods and fuels.
26 Alcoholic FermentationYeast and a few other microorganisms use alcoholic fermentation, forming ethyl alcohol and carbon dioxide as wastes Equation for alcoholic fermentation: pyruvic acid + NADH ethyl alcohol + CO2 + NAD+ This causes bread dough to rise a. Yeast runs out of oxygen, starts to ferment b. gives off bubbles of carbon dioxide making air spaces you see in a slice of bread c. small amount of alcohol is formed, evaporates when bread is baked
27 Lactic Acid FermentationMany cells convert accumulated pyruvic acid from gycolysis to lactic acid; lactic acid fermentation regenerates NAD+ so glycolysis can continue Equation for lactic acid fermentation: pyruvic acid + NADH lactic acid + NAD+ 4. When your body cannot supply enough oxygen to muscle tissues during exercise, this is produced 5. Without oxygen the body is unable to produce all the ATP it requires, so lactic acid fermentation takes over
28 Running, swimming, or riding a bike as fast as you can = large muscles in your legs and arms that quickly run out of oxygen…muscles begin to rapidly produce ATP by lactic acid fermentation. The buildup of lactic acid fermentation causes a painful burning sensation making your muscles feel sore… How do you stop it????? NEED TO INTAKE OXYGEN
29 Energy and Exercise Initially body uses ATP which is already available in muscles Then new ATP made by Lactic Acid Fermentation and Cellular Respiration Eventually energy supply runs out A. Quick Energy 1. ATP in muscles only lasts a few seconds 2. ATP from lactic acid fermentation lasts about 90 seconds - this then creates a by-product (lactic acid) which the body must get rid of, the body releases it by panting heavily (intake of oxygen)
30 - exercise lasting longer than 90 seconds utilizes B. Long-Term Energy - exercise lasting longer than 90 seconds utilizes cellular respiration to generate a continuous supply of ATP - cellular respiration releases energy slower than fermentation, thus athletes can pace themselves - body stores energy in muscles and tissues in the form of glycogen (carbohydrate) -- stores of glycogen usually lasts for minutes of activity, then the body starts to break down other molecules like fat for energy HOW LONG DO YOU NEED TO ACTIVE BEFORE YOU START TO BURN FAT????? 17-22 minutes
31 Aerobic vs. Anaerobic Respiration: A ComparisonAdvantages of Aerobic Respiration Major advantage more energy released Enough energy to produce up to 38 ATP Advantages of Anaerobic Respiration Lets organisms live in places where there is little or no oxygen Quickly produces ATP The amount of energy produced by aerobic respiration may explain why aerobic organisms came to dominate life on Earth. It may also explain how organisms were able to become multicellular and increase in size.
32 Relationship between Cellular Respiration and PhotosynthesisEquation for Cellular Respiration: 6O C6H12O6 6CO H2O + energy (ATP) Equation for Photosynthesis: 6CO H2O + energy (sunlight) 6O C6H12O6
33 Almost opposite processes:Photosynthesis deposits energy; cellular respiration withdraws energy Photosynthesis removes carbon dioxide from atmosphere; cellular respiration puts it back Photosynthesis releases oxygen into the atmosphere; cellular respiration uses it to release energy from food Cellular respiration in all eukaryotes and some prokaryotes Photosynthesis only occurs in plants, algae, and some bacteria
34 LET’S REVIEW… How many stages does cellular respiration have? ____________ What are the stages of cellular respiration? ________________________________________________________________________ Where does glycolysis take place? ____________________________________ Where does the Krebs cycle take place? ___________________________________ 3 GLYCOLYSIS, KREBS CYCLE, AND ELECTRON TRANSPORT CHAIN CYTOSOL OF THE CYTOPLASM OF MITOCHONDRIA IN THE MATRIX OF MITOCHONDRIA
35 Where is the Electron Transport Chain locatedWhat do high-energy electrons help the cells build? ____________________________________________________________________ What are the stage(s) of aerobic respiration? ____________________________________________________________________ INNER MEMBRANE OF MITOCHONDRIA MOLECULES LIKE GLUCOSE; ATP GLYCOLYSIS, KREBS CYCLE, AND ELECTRON TRANSPORT CHAIN
36 What are the stage(s) of anaerobic respirationWhat are the two types of fermentation? ____________________________________________________________________ Which fermentation process do humans use? __________________________________ GLYCOLYSIS, FOLLOWED BY FERMENTATION ALCOHOLIC FERMENTATION AND LACTIC ACID FERMENTATION LACTIC ACID FERMENTATION
37 Lesson Summary In the two to three billion years since photosynthesis added oxygen to earth’s atmosphere, life has become mostly aerobic. Some organisms and types of cells retain the older, anaerobic pathways for making ATP; these pathways comprise anaerobic respiration or fermentation. Muscle cells can continue to produce ATP when O2 runs low using lactic acid fermentation, but muscle fatigue and pain may result. Both alcoholic and lactic acid fermentation pathways change pyruvate in order to continue producing ATP by glycolysis. Aerobic respiration is far more energy-efficient than anaerobic respiration. Aerobic processes produce up to 38 ATP per glucose. Anaerobic processes yield only 2 ATP per glucose.