All Organisms Use Energy to Carry Out the Functions of Life Plants are the primary producers The use direct sunlight for energy through a process called photosynthesis Autotrophic vs. Heterotrophic What is the difference?
Photosynthesis - Involves a complex set of chemical reactions that form a biochemical pathway.
Why are plants green? Chlorophyll –Two types: Chlorophyll a and Chlorophyll b Accessory pigments Carotenoids Xanthophylls –Pigments seen in FALL!!!
The Balance Sheet for Photosynthesis Light Reaction –Produces stored energy in the form of ATP and NADPH from light energy. Calvin Cycle –Produces organic compounds, using the energy stored in ATP and NADPH during the light reactions. The Simplest Chemical Equation for Photosynthesis: CO 2 + H 2 O + light energy -> (CH 2 O) + O 2 The Balanced Chemical Equation for Photosynthesis: 6CO 2 + 6H 2 O+ light energy -> C 6 H 12 O 6 + 6O 2
Alternative Pathways C3 plants fix carbon exclusively through the Calvin Cycle, because the three carbon PGA is formed. Plants that do not produce the three carbon PGA live in hot or dry climates and utilize alternative pathways. –C4 pathway enables plants to fix into four carbon compounds. Examples include: corn, sugar cane, and crabgrass. –Cactuses, pineapples, and certain other plants that live in hot, dry climates fix carbon through the CAM pathway.
Summing it up… A plant’s environment can effect its rate of photosynthesis. Light intensity can also be a factor. As well as, CO 2 levels and temperature.
Photosynthesis Cellular Respiration
C 6 H 12 O 6 + 6O 2 -> 6CO 2 + 6H 2 O + energy (ATP)
How are Photosynthesis and Cellular Respiration Related? Photosynthesis –Uses Light Energy –Uses Carbon Dioxide –Uses Water –Makes Glucose –Makes Oxygen –Happens in the Chloroplasts 6CO 2 + 6H 2 O + light energy -> C 6 H 12 O 6 + 6O 2 Cellular Respiration –Makes Energy (ATP) –Makes Carbon Dioxide –Makes Water –Uses Glucose –Uses Oxygen –Happens in the Mitochondria C 6 H 12 O 6 + 6O 2 -> 6CO 2 + 6H 2 O + energy (ATP)
1 st Step in Cellular Respiration – Glycolysis Breakdown or splitting of glucose (6 carbons) into two 3- carbon molecules called pyruvic acid Does not need oxygen in any of its chemical reactions Serves as the first step in a variety of anaerobic and aerobic reactions Happens in the cytoplasm of cells FYI: The one metabolic pathway found in all living organisms Net yield of two ATP molecules for every molecule of glucose that is converted into pyruvic acid
Molecular Pictures Glucose 2 molecules of Pyruvic Acid Images taken from: llresp.htm llresp.htm 2 ATP molecules
Fermentation Pyruvic acid molecules are turned into some “waste” product Occurs in anaerobic situations Two of the most common types of fermentation are: –lactic acid and alcoholic fermentation
Lactic Acid Fermentation Done by some fungi, some bacteria like the Lactobacillus acidophilus in yogurt, and sometimes by our muscles. The 3-carbon pyruvic acid molecules are turned into lactic acid This process is used in making cheese and yogurt. Once our muscles form lactic acid, they can’t do anything else with it, so until it is gradually washed away by the blood stream and carried to the liver (which is able to get rid of it) until it is converted back to pyruvic acid when oxygen becomes available
Alcoholic Fermentation Done by yeast and some kinds of bacteria. The “waste” products of this process are ethanol and carbon dioxide (CO 2 ). This process is used in making bread, beer, and wine.
Fermentation – Two Major Types Lactic Acid Fermentation Muscles produce lactic acid Causes muscles to become tired Occurs after exercise Why does this happen? –Your muscle cells can’t get the oxygen they need to produce ATP by cellular respiration. Alcoholic Fermentation Yeast cells produce carbon dioxide and alcohol Example: carbon dioxide causes bubbles to form in bread Why does this happen? –Yeast cells eat sugar and expel carbon dioxide, which causes bubbles to form in bread.
Anaerobic Pathways as the oldest known way of producing ATP??? Glycolysis is probably the oldest known way of producing ATP. There is evidence that the process of glycolysis predates the existence of O2 in the Earth’s atmosphere and organelles in cells: –Glycolysis does not need oxygen as part of any of its chemical reactions. It serves as a first step in a variety of both aerobic and anaerobic energy-harvesting reactions. –Glycolysis happens in the cytoplasm of cells, not in some specialized organelle. –Glycolysis is the one metabolic pathway found in all living organisms. –Total Efficiency of Glycolysis 3.5%
2 nd Step of Cellular Respiration – Krebs Cycle In prokaryotes, the reactions of the Krebs Cycle take place in the cytosol of the cell. In eukaryotes, the reactions take place in the mitochondrial matrix The pyruvic acid produced in glycolyis diffuses across the double membrane of the mitochondria into the mitochondrial matrix where it reacts with a molecule called coenzyme A to form acetyl CoA, which then enters the Krebs Cycle In short…the Krebs Cycle breaks down acetyl CoA, produces CO2, hydrogen atoms, and ATP
Krebs Cycle Cont… Recall that…in glycolysis one glucose molecule produced two pyruvic acid molecules, which can then form two molecules of acetyl CoA. Thus…one glucose molecule causes two turns of the Krebs Cycle. The two turns produce: –Six molecules of NADH -> electron transport chain –Two molecules of FADH2 -> electron transport chain –Two molecules of ATP -> can be used as energy –Four CO2 molecules -> released by the organism
3 rd Step in Cellular Respiration – The Electron Transport Chain The concentration gradient drives the synthesis of ATP by chemiosmosis, the same process that generates ATP in photosynthesis!!! ATP is produced when NADH and FADH2 release hydrogen atoms By combining with both electrons and protons (H+), oxygen forms water!!! Here is the formula: O 2 + 4e - + 4H + -> 2H 2 O
How many ATP molecules are made in aerobic respiration? 38 ATP per one glucose molecule!!! WOW!!! FYI: the actual number of ATP molecules generated through aerobic respiration varies from cell to cell. Most produce 36 ATP molecules per glucose molecule.
How efficient is aerobic respiration? 66% compared to 3.5% of glycolysis. This means that aerobic respiration is 20 times more efficient than anaerobic!!! It is even more efficient than a car engine which is only 25%!!!
Summing Up Cellular Respiration… Cellular respiration provides the ATP that all cells need to support the activities of life. Cells also need specific organic compounds (sugars and starches) from which to build macromolecules, which not always come from the food we eat. That is why Glycolysis and the Krebs Cycle are used by cells to make the compounds that are missing in food. C 6 H 12 O 6 + 6O 2 -> 6CO 2 + 6H 2 O + energy (ATP)