Cellular respiration and fermentation 04/18/2016 BI102
Announcements Exam 1 after lecture Don t forget to do the online assignments every week! Quiz 2 and lab 2 review
Cellular Respiration
Cells require lots of energy Cell require a constant supply of energy to perform metabolic reactions Energy is transferred from energy-storage molecules like glucose to energy-carrier molecules like ATP The energy used on earth comes almost entirely from the Sun
Energy storage Plants convert glucose to sucrose or starch Animals convert glucose to glycogen and fat We will not cover the conversion of storage molecules to glucose We will cover the breakdown of glucose during respiration
The energy carrier molecule, ATP A nucleoside with three phosphates AMP is a nucleotide in RNA Paired with endergonic reactions dephosphorylation of ATP
Electron (energy) carriers FAD (vitamin B2) and NAD (vitamin B3) are electron carriers They can be easily reduced (add e-) or oxidized (give out e-)
Oxidative phosphorylation chemiosmosis in the cell for ATP production In eukaryotes, oxidative phosphorylation takes place in mitochondria. In prokaryotes, this process takes place in the plasma membrane.
Photosynthesis 6 CO 2 + 6 H 2 O + light energy C 6 H 12 O 6 + 6 O 2 Cellular respiration C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + 38 ATP + heat
Cellular respiration Animals do this too We just bypass photosynthesis by eating, breathing (exhaled)
Cellular Respiration
Cellular respiration Glycolysis generates 2 ATP Kreb s cycle generates 2 ATP Identified in 1937 by Hans Adolf Krebs Electron Transport Chain generates 34 ATP 38 ATP total (in theory)
Glycolysis Glyco sweet Lysis split apart Happens outside the mitochondria Cytoplasm One glucose molecule is converted to two pyruvate molecules 2 ATP and 2 NADH are generated
Kreb s or Citric acid cycle If oxygen is available, the 2 pyruvate will be broken down into 6 CO2 and ATP Takes place in the matrix
Oxidation of pyruvate First, each pyruvate is split, releasing a CO2, leaving an acetyl behind Acetyl reacts with CoA, transferring two electrons to NAD + The CO2 has two of the original six carbons from glucose
Kreb s or Citric acid cycle Start with one molecule of Acetyl CoA By the end of the cycle, two CO 2 will be generated and chemical energy will be stored in 1 ATP, 3 NADH, and 1 FADH 2 CO 2 diffuses from the mitochondrial matrix into your blood where it is transported finally to your lungs
Kreb s or Citric acid cycle If oxygen is available, the 2 pyruvate will be broken down into 6 CO2 and ATP
Energy inventory Glycolysis Each glucose 2 pyruvate + 2 ATP Kreb s cycle Each pyruvate 3 CO 2 + 1 ATP Total is 4 ATP per glucose But the cell has charged up 10 NADH and 2 FADH 2 per glucose These will release electrons during the electron transport chain The depleted energy carriers can be recharged again
Electron Transport Chain (ETC) High-energy electrons jump from molecule to molecule releasing small amounts of energy Energy is used to pump H + across the inner membrane into the intermembrane space
Electron Transport Chain (ETC) The concentration gradient of H + across the membrane is used to drive ATP production by ATP synthase The electrons, the H +, and O 2 combine to form water (1 water molecule/2 electrons)
Electron Transport Chain (ETC)
ATP is recycled by the cell A protein carrier takes the ATP molecules to the intermembrane space (and then the ADP molecules to the matrix) The ATP molecules diffuse through the large pores in the outer membrane and enter the cytosol Then, ADP molecules diffuse back into the intermembrane space
Fermentation What happens when oxygen is unavailable? Cells must generate ATP without oxygen Fermentation Less efficient 2 ATP per glucose Waste products Lactic acid (animals, bacteria (yogurt)) C 6 H 12 O 6 2 Lactic acid + 2 ATP + heat
Lactic acid fermentation
Fermentation Waste products in yeast: ethanol and CO 2 C 6 H 12 O 6 2 CO 2 + 2 Ethanol + 2 ATP + heat
Alcoholic fermentation
Cellular respiration - summary
Amino acids can be sent to glucose canabolism
Glycogen, fats, and proteins can be fed into cell respiration