OTA

1. OTA • Describe what ‘respect for others’ means to you.

2. OTA • List the two types of metabolic processes that we went over yesterday. Also give a short description.

3. OTA • Write a paragraph describing what has been covered up to today, that will be on your next test.

4. OTA 2-4-08 • Write a paragraph describing why respect for others is an important part of character and how you show respect for others.

5. Cellular Metabolism Chapter 4

6. Metabolic Processes • In every cell, thousands of reactions occur daily; these constitute metabolism. • Each reaction has an enzyme that controls the speed of the reaction. • Two types of metabolic pathways • Anabolic pathways- larger molecules are constructed from smaller ones; energy required • Catabolic pathways- larger molecules are broken down; energy is released

7. Anabolism • Provides the substances needed for cellular growth and repair.

8. Anabolism • Example: Dehydration synthesis • Allows monomers to form polymers by removal of H2O. • Used to make polysaccharides, triglycerides, and proteins • Peptide bond- formed when amino acids link up; dipeptides & polypeptides • Proteins are very large and consist of about 100 or more polypeptides

9. Anabolism dehydration synthesis- triglyceride

10. Anabolism dehydration synthesis- protein

11. Catabolism • Physiological process that breaks down larger molecules into smaller ones

12. Catabolism • Example: Hydrolysis • Addition of water molecules to decompose carbohydrates, lipids, proteins, and nucleic acids into their building blocks • Reverse of dehydration synthesis

13. Anabolism & Catabolism • All cells perform certain basic reactions such as the buildup & breakdown of macromolecules. These include 100s of very specific changes that must occur in a particular sequence. • Require the help of specific enzymes • Theses enzymes control the rate of all the metabolic reactions of the cell.

14. Control of Metabolic Reactions: Enzymes • Lower the activation energy- the energy required to start metabolic reactions. • Globular proteins- enzymes with specific shapes. • not consumed in chemical reactions. • Substrate specificity- will only act on a specific substrate • Shape of active site determines substrate • Enzyme names are derived from their substrate’s name with a suffix “ase”

16. Control of Metabolic Reactions • Sequences of enzyme–controlled reactions that lead to the synthesis or hydrolysis of biochemicals. • Each enzyme must be able to recognize its substrate • Each enzyme’s polypeptide chain conforms to the special shape of its substrate molecule. • Active sites- regions of the enzyme that combine with the substrate= enzyme-substrate complex. • Speed of an enzyme-catalyzed reaction depends partly on the # of enzyme & substrate molecules in the cell.

17. Control of Metabolic Reactions • each new substrate is the product of the previous reaction

19. Control of Metabolic Reaction: Cofactors & Coenzymes • Cofactor • Make some enzymes active by allowing the active site to bind the enzyme to the substrate. • Ions or coenzymes • Coenzymes • Small organic molecle that act as cofactors • Will activate a specific enzyme • Found in vitamins • Organic compounds needed by the cell that the body cannot synthesize in adequate amounts.

20. Factors that Alter Enzymes • Proteins (enzymes) can be denatured by exposure to heat, radiation, electricity, & chemicals with extreme pH levels. • Example: • 45 degrees C = inactive • 55 degrees C= denatured • Cyanide can destroy enzymes

21. Energy for Metabolic Reactions • Energy is the ability to do work or change something. • Heat, light, sound, electricity, mechanical energy, and chemical energy. • Changed from one form to another • Involved in ALL metabolic reactions.

22. Energy for Metabolic Reactions: Release of chemical energy • Most metabolic processes depend on chemical energy. • This energy is contained in the chemical bonds that build macromolecules • The energy is released when these bonds are broken.

23. Energy for Metabolic Reactions: Release of chemical energy • Oxidation is the process of burning glucose to release energy therefore oxidation of glucose generates chemical energy • Cellular respiration releases chemical energy from molecules and makes it available for cellular use.

24. Cellular Respiration • Occurs in three series of reactions • Glycolysis • Citric acid cycle • Electron transport chain • The end-products of these reactions are heat, carbon dioxide, water, & energy stored in ATP. Some of the energy is lost as heat, but half is used to produce ATP.

25. Cellular Respiration • Produces • Carbon dioxide • Water • ATP (chemical energy) • Heat

26. Cellular Respiration • Includes • Anaerobic reactions • Without O2 • Produces little ATP • Aerobic Reactions • Requires O2 • Produces most ATP

27. ATP Molecule • Each ATP molecule has three parts: • An adenine molecule • A ribose molecule • Three phosphate molecules in a chain

29. ATP Molecule • The 3rd phosphate is attached by a high energy bond • when the bond is broken, energy is transferred to other molecules (ATP becomes ADP) • When energy is released it is used when cells have to do work • Energy from breakdown of ATP powers cellular work • ATP  ADP  ATP (reversible)

30. Phosphorylation • Phosphorylation- process in which a 3rd phosphate is attached to ADP and creates ATP • Requires energy released from cellular respiration • Without ATP cells would die • Oxidative phosphorylation • Glucose can be oxidized and yield 38 ATP molecules

31. Glycolysis • “Breaking of Glucose” -Breaks down glucose into 2 pyruvic acids • Series of ten reactions • Occurs in cell’s cytosol • An anaerobic phase of cellular respiration • Yields two ATP molecules per glucose • Summarized by three main events • Phosphorylation/Priming • Splitting/Cleavage • Production of NADH and ATP

32. Glycolysis • Event 1:Phosphorylation • Glucose is phosphorylated (2 phosphates added to glucose) • Requires energy • Event 2: Splitting/Cleavage • Glucose (6-carbon) is split into two 3 carbon molecules.

33. Glycolysis • Event 3: Production of NADH and ATP • Hydrogen atoms are released • Hydrogen atoms bind to NAD+ to produce NADH • NADH delivers hydrogen atoms to the electron transport chain if oxygen is available. • ADP is phosphorylated to become ATP • Two molecules of pryruvic acid are produced.

35. Anaerobic Reactions • Oxygen is the final electron acceptor in the glycolysis (aerobic reactions). If oxygen is not available the electrons will attach to the pyruvic acid molecules, to form lactic acid. • So if oxygen is not available- • Electron transport chain cannot accept NADH • Pyruvic acid is converted to lactic acid • ATP production declines. • *When O2 is present again liver cells convert lactic acid to pyruvic acid.

36. Aerobic Reactions • If oxygen is available- • Pyruvic acid is used to produce acetyl CoA • Citric acid cycle begins • Electron transport chain functions • Carbon dioxide and water are formed • 36 molecules of ATP produced per glucose molecule • Aerobic Respiration (Krebs cycle or citric acid cycle & oxidative phosphorylation or electron transport chain) • Begins with pyruvic acid moving into the mitochondria

38. Citric Acid Cycle • Begins when acetyl CoA combines with oxaloacetic acid to form the 6-carbon citric acid & CoA • Cycle repeats as long as pyruvic acid is supplied to the mitochondria and oxygen is available • For each citric acid molecule: • 1 ATP is produced • 8 hydrogen atoms are transferred to NAD+ and FAD • 2 CO2 produced

40. Electron Transport Chain • NADH and FADH2 carry electrons to the ETC • ETC series of electron carriers located in the cristae of mitochondria • High energy electrons are handed off to the ETC w/the help of enzymes that use the energy to phosphorylate ADP to form ATP • Water is formed

43. Summary of Catabolism of Proteins, Carbohydrates, & Fats

44. Carbohydrate Storage • Excess glucose is stored as • Glycogen (primarily by liver and muscle cells) • Fat • Converted to amino acids

46. Regulation of Metabolic Pathways • Influenced by enzymes that are responsible for a certain step in a pathway. • The rate-limiting enzyme- 1st enzyme in a series that can regulate metabolic pathways • Negative feedback *remember the ex. of a thermostat inside a house

47. Nucleic Acids & Protein Synthesis • Deoxyribonucleic acid (DNA) contains the information needed for the synthesis of each protein (enzyme) required by the cell. • Genetic Information- instructs the cells how to construct proteins; stored in DNA

48. Genetic Information • Gene- segment of DNA that codes for one protein • Sequence of nucleotides- in DNA molecules it dictates the sequence of amino acids in a protein and how to start/stop the protein’s synthesis; DNA is double-stranded

49. Genetic Information – cont. • Genetic Code- method used to translate a sequence of nucleotides of DNA into a sequence of amino acids • DNA- located in the nucleus • Protein synthesis- in the cytoplasm • RNA- helps get the information to the cytoplasm

50. Structure of DNA • Two polynucleotide chains • Hydrogen bonds hold nitrogenous bases together • Bases pair specifically (AT and CG) • Forms a helix • DNA wrapped about histones.