CELLULAR RESPIRATION

By the end of the lesson (s), I can:  Describe the process of cell respiration, including reactants and products, glycolysis, the Krebs cycle, and the electron transport chain.  Distinguish between aerobic and anaerobic respiration.

 Harvesting Chemical Energy Cellular respiration is the complex precess in which cells make adenosine triphosphate (ATP) by breaking down organic compounds. Both autotrophs and heterotrophy undergo cellular respiration to breakdown organic compounds into simpler molecules to release energy. Some energy is used to make ATP which is then used by the cells to do work.

The figure shows that autotrophs and heterotrophs use cellular respiration to make CO 2 and water from organic compounds and oxygen. ATP is also made during cellular respiration. Autotrophs then use the CO 2 and water to produce oxygen and organic compounds. Therefore, we can say that the products of cellular respiration are the reactants in photosynthesis and conversely, the products of photosynthesis are the reactants of cellular respiration CELLULAR RESPIRATION BY AUTOTROPHS AND HETEROTROP OHS PHOTOSYNT HESIS BY AUTOTROPH S ORGANIC COMPOUNDS & OXYGEN CARBON DIOXIDE & WATER

Cellular respiration can be divided into 2 stages: Glycolysis  Stage in which organic compounds are converted into 3 carbon molecules of pyruvic acid, producing a small amount of ATP and NADH (an electron carrier molecule). This is an anaerobic process because it does not require the presence of oxygen. Aerobic respiration  If oxygen is present in the cell’s environment, pyruvic acid is broken down and NADH is used to make a large amount of ATP through the process known as aerobic respiration

Pyruvic acid can enter other pathways if there is not oxygen present in the cell’s environment. The combination of glycolysis and these anaerobic pathways is called fermentation. Many of the reactions in cellular respiration are redox reactions. In redox reactions one reactant is oxidized (loses electrons) while another is reduced (gains electrons).

 Glcolysis is a biochemical pathway in which one six-carbon molecule of glucose is oxidized to produce 2 three carbon molecules of pyruvic acid.  Series of chemical reactions catalyzed by specific enzymes.

 All reactions take place in the cytosol and occur in 4 main steps:  Step 1 2 phosphate groups are attached to one molecule of glucose. The phosphate groups are supplied by two molecules of ATP, which are converted into 2 molecules of ADP in the process.  Step 2 The six-carbon compound formed in step 1 is split into 2 three-carbon molecules of glyceraldehydes 3- phosphate (G3P). (also produced by the Calvin cycle in photosynthesis.

 Step 3  2 G3P molecules are oxidized, and each receives a phosphate group.  The product of this step is 2 molecules of a new 3-carbon compound.  The oxidation of G3P is accompanied by the reduction of 2 molecules of Nicotinamide Adenine dinucleotide (NAD + ) to NADH. NAD+ is similar to NADP+ a compound involved in the light reactions of photosynthesis. Like NADP+, NAD+ is an organic molecule that accepts electrons during redox reactions.  Step 4  The phosphate groups are added in steps 1 and 3 are removed from the 3-carbon compounds formed in step 3.  This reaction produces 2 molecules of pyruvic acid.  Each phosphate group s combined with a molecule of ADP to make a molecule of ATP. Because a total of 4 phosphate groups are added in step 1 and 3, 4 molecules of ATP are produced.  2 ATP molecules were used in step 1, but 4 were produced in step 4. Therefore, the process of glyolysis has a net yield of 2 ATP molecules for every glucose molecule converted into pyruvic acid.