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). /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  An aerobic respiration – does not require oxygen; happens if oxygen is lacking Oxygen? NO Anaerobic Respiration Aerobic Respiration YES

 An aerobic process (requires oxygen).  Reaction releases energy from the chemical bonds of carbohydrates.  Takes place in the mitochondria.  Equation: 6O 2 + C 6 H 12 O 6 6H CO ATP Oxygen + Glucose Water + Carbon Dioxide + Energy

Equation for photosynthesis: Energy + 6H 2 O + 6CO 2 C 6 H 12 O 6 + 6O 2 Equation for aerobic cellular respiration: 6O 2 + C 6 H 12 O 6 6H CO ATP

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 Plants  Animals  Fungi  Protists  Some bacteria  …almost everything alive!

 Recap: Step 1 = glycolysis 2 ATP molecules are 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 CO 2 & 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 CO 2 molecules, a handful of electrons (H + ) and 4 ATP molecules.  The CO 2 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.

C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + 36 ATP Glucose + 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 AcidsProteins Carbohydrates Lipids Amino Acids Sugars Fatty Acids/ Glycerol Pyruvate Acetyl-CoA Krebs Cycle Urea H2OH2O CO 2 Nucleotides

 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  An anaerobic process (does not require oxygen)  Two types of fermentation:  Alcohol fermentation  Lactic acid fermentation  Both take place in the cytoplasm. fermenter.jpeg

Pyruvic acid + NADH NAD + + alcohol + CO ATP

 Yeast perform alcohol fermentation in the absence of oxygen.  The alcohol produced is the type that we drink.  The CO 2 produced is used to make bread rise.

 Pyruvic acid + NADH NAD + lactic acid 2 ATP *Lactic acid is what makes your muscles sore when you exercise.

 Humans (and other animals) - when they are exercising and their muscles aren’t getting enough O 2 to keep up with the energy demand.  The build up of lactic acid is what makes your muscles start to burn. session.jpg

 You get way more ATP from aerobic cellular respiration than you do from anaerobic cellular respiration (fermentation).  Fermentation is mostly used to provide organisms with short-term bursts of energy when oxygen is not available. content/uploads/2006/08/washington.jpg