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Transcript
Do our cells breathe? …Using glucose to make energy (ATP) If plants need ATP (energy) to form glucose, how can glucose be a source of energy for plants and animals? How does our body use glucose to make energy? Why do your muscles get really sore when you exercise intensely, but not when you pace yourself? How do you get wine from grapes? Plants get energy from the sun and store it in the bonds of ___________. glucose • How do we get energy? – • by eating food. What types of food provide the most energy? – Carbs (sugars or glucose) have the most energy • e.g. candy bars, wheat, potatoes, rice, pasta • What does your body do to the food you eat? - Our body digests our food (breaks apart bonds), releasing energy Breaking bonds releases energy! Energy is “stored” in the glucose bonds; breaking them releases the energy What form of energy do our cell (and our body) use? the molecule ATP So.. our body breaks down glucose and uses it to make ATP (ENERGY!) Which organelle is responsible for producing energy for our cells? The MITOCHONDRIA ATP (adenosine triphosphate) is a nucleic acid that can transfer energy within the cell. Ex: a small amount of energy from a glucose molecule can be used directly… The extra energy is transferred to ATP. The energy in ATP is stored in the bonds between the phosphates (ATP has 3 phosphates). http://www.brooklyn.cuny.edu/bc /ahp/LAD/C7/graphics/C7_atp_2 .GIF Remember…cellular respiration is using glucose to make energy Step 1: glycolysis glyco = refers to glucose lysis = break apart Glycolysis = break down 1 glucose into 2 pyruvic acid molecules, which have three carbons each (splits glucose in half) Also makes 2 ATP! Takes place in the cytoplasm Why would we need to break down glucose in the cytoplasm first before we use it in the mitochondria? (think transport) Glucose molecules are too large to move into the mitochondria, so glycolysis makes them smaller to get through the mitochondria’s membranes After glycolysis, there are two possible paths: Aerobic respiration – requires oxygen Anaerobic respiration – does not require oxygen; happens if oxygen is lacking Oxygen? Aerobic Respiration Anaerobic Respiration An aerobic process (requires oxygen). Reaction releases energy from the chemical bonds of carbohydrates. Takes place in the mitochondria. Equation: 6O2 + C6H12O6 6H20 + 6CO2 + 36ATP Oxygen + Glucose Water + Carbon Dioxide + Energy Equation for photosynthesis: Energy + 6H2O + 6CO2 C6H12O6 + 6O2 Equation for aerobic cellular respiration: 6O2 + C6H12O6 6H20 + 6CO2 + 36ATP http://www.channelislandsrestoration.com/photos/images/Isl andFox1.jpg http://www.rhs.org.uk/chelsea/2005/exhibitors/plants/images/GlebeCott agePlants.jpg http://www.ucmp.berkeley.edu/fungi/basidio/mushroomsismall.jpg Plants Animals Fungi Protists Some bacteria …almost everything alive! Recap: Step 1 = glycolysis – 2 ATPs produced in cytoplasm and enter mitochondria. For aerobic respiration, in mitochondria: Step 2 = Krebs Cycle (Citric Acid Cycle) – in matrix Step 3 = Electron Transport Chain – in inner membrane ATP is generated in each step, but most of the ATP is made in the Electron Transport Chain Right before the Krebs Cycle, the Pyruvate from glycolysis is converted to Acetyl-CoA. During Krebs, the Acetyl-CoA is broken down into CO2 & electrons (H+). 2 ATP are created. The electrons then move on to the Electron Transport Chain. We start with one molecule of glucose and end up with 6 CO2 molecules, a handful of electrons (H+) and 4 ATP molecules. The CO2 is waste that will move out of the cell (and which you exhale). The 4 ATP molecules can be used by the cell as energy. What about the other 32 ATPs from our equation? Embedded in the mitochondria inner membrane are proteins called electron carriers. The electrons (H+) from Glycolysis and the Krebs Cycle are passed from electron carrier to electron carrier (like a bucket brigade). With every pass, energy is released from the electrons, and ATP is made. As a result, 32 ATP are made in the Electron Transport Chain. C6H12O6 Glucose + 6O2 → 6CO2 + 6H2O + 36 ATP + Oxygen → Carbon dioxide + Water + ATP (Krebs Cycle) What happens with respiration of lipids, proteins, and nucleic acids? Starch: broken down into glucose, which enters glycolysis Fats: broken down into fatty acids and glycerol; fatty acids are cut into 2-carbon compounds, converted to Acetyl-CoA, and enter the Krebs Cycle Proteins: broken down into amino acids, which can be converted into Acetyl-CoA or other compounds that enter the Krebs cycle at various points The amino group is removed & excreted as urea. Nucleic Acids Nucleotides Proteins Carbohydrates Lipids Sugars Fatty Acids/ Glycerol Amino Acids Pyruvate Acetyl-CoA Krebs Cycle Urea H2O CO2 During aerobic respiration, where do the electrons (H+) end up as they are passed from protein to protein? They end up in the loving arms of oxygen. When oxygen accepts electrons, water is made. If oxygen wasn’t there to accept the electrons, the Electron Transport Chain would get backed up, and no energy would be produced. What type of respiration happens when there is no oxygen? …and where does it happen? AKA: fermentation Two types: Alcohol fermentation Lactic acid fermentation Both take place in the cytoplasm. Each creates 2 ATP from each pyruvic acid molecule. http://www.schmohz.com/images/beerfermenter.jpeg Yeast can do aerobic or anaerobic respiration. Grapes turn to alcohol by adding yeast in containers with out oxygen. Bread rises because yeast gives off CO2 bubbles while fermenting in dough. http://www.utoronto.ca/greenblattlab/images/a/yeast%201.jpg When humans (and other animals) exercise intensely, their muscles often use more O2 than is available When O2 runs out, muscles switch to anaerobic respiration to try to keep up with energy demand. This is lactic acid fermentation. The build up of lactic acid is what makes your muscles sore. http://www.donlemmonsknowhow.com/img/exercisesession.jpg You get way more ATP from aerobic cellular respiration than from fermentation. Fermentation is mostly used to provide organisms with short-term bursts of energy when oxygen is not available. http://www.athleticsireland.ie/content/wpcontent/uploads/2006/08/washington.jpg