lesson 5 part 1.

• Cellular Respiration is the process that all living things use to convert glucose into energy.
• Two ATP molecules were used in the first half of the pathway to prepare the six-carbon ring for cleavage, resulting in a net gain of two ATP molecules and two NADH molecules for the cell's use.
• Cellular respiration extracts the energy from the bonds in glucose and converts it into a form that all living things can use.
• Glycolysis, the first step in cellular respiration, takes place in the cytoplasm of both prokaryotic and eukaryotic cells.
• Glucose enters heterotrophic cells in two ways: through secondary active transport in which the transport takes place against the glucose concentration gradient and through a group of integral proteins called GLUT proteins, also known as glucose transporter proteins.
• These transporters assist in the facilitated diffusion of glucose.
• Glycolysis consists of ten steps divided into two distinct halves: energy-requiring steps, which trap the glucose molecule in the cell and use energy to modify it so that the six-carbon sugar molecule can be split evenly into the two three-carbon molecules, and energy-releasing steps, which extract energy from the molecules and store it in the form of ATP and NADH.
• The first half of glycolysis, the energy-requiring steps, includes Hexokinase phosphorylating glucose using ATP as the source of the phosphate, producing glucose-6-phosphate, a more reactive form of glucose.
• In the second step of glycolysis, an isomerase converts glucose-6-phosphate into one of its isomers, fructose-6-phosphate.
• The sixth step in glycolysis oxidizes the sugar (glyceraldehyde - 3 - phosphate), extracting high-energy electrons, which are picked up by the electron carrier NAD+, producing NADH.
• The first step in glycolysis is the conversion of glucose to fructose, catalyzed by the enzyme glucokinase.
• In the eighth step, the remaining phosphate group in 3 - phosphoglycerate moves from the third carbon to the second carbon, producing 2 - phosphoglycerate (an isomer of 3 - phosphoglycerate).
• This enzyme causes 2 - phosphoglycerate to lose water from its structure; this is a dehydration reaction, resulting in the formation of a double bond that increases the potential energy in the remaining phosphate bond and produces phosphoenolpyruvate (PEP).
• The last step in glycolysis is catalyzed by the enzyme pyruvate kinase and results in the production of a second ATP molecule by substrate-level phosphorylation and the compound pyruvic acid (or its salt form, pyruvate).
• Enolase catalyzes the ninth step.
• Glycolysis starts with glucose and ends with two pyruvate molecules, a total of four ATP molecules and two molecules of NADH.
• In the fifth step, an isomerase transforms the dihydroxyacetone - phosphate into its isomer, glyceraldehyde - 3 - phosphate.
• The fourth step in glycolysis employs an enzyme, aldolase, to cleave 1,6 - bisphosphate into two three - carbon isomers: dihydroxyacetone - phosphate and glyceraldehyde - 3 - phosphate.
• The second step in glycolysis is the phosphorylation of fructose - 6 - phosphate, catalyzed by the enzyme phosphofructokinase.
• In the seventh step, catalyzed by phosphoglycerate kinase (an enzyme named for the reverse reaction), 1,3 - bisphosphoglycerate donates a high-energy phosphate to ADP, forming one molecule of ATP.