Metabolism & Cellular Respiration
Metabolism The sum of all the chemical reactions that occur within you as a living organism. Anabolism – the type of reaction that uses energy to build complex organic molecules from simpler ones. Catabolism – the type of reaction that breaks down complex organic molecules with the release of energy
Metabolism Anabolic Reactions Catabolic Reactions Build complex molecules Brea down complex molecules Are Endergonic Are Exergonic Are Biosynthetic Are Degradative Example: Photosynthesis Example: Cellular Respiration
Metabolism Almost all metabolic reactions in organisms are catalyzed by enzymes Many of these reactions occur in specific sequences and are called metabolic or biochemical pathways. Metabolic pathways consist of chains and cycles of enzyme-catalyzed reactions
Metabolism Activation Energy – the energy necessary to destabilize the existing chemical bonds in the substrate of an enzyme-substrate catalyzed reaction Enzymes lower the activation energy of a chemical reaction that they catalyze Make reactions go faster During the process of the reaction, energy is given out as new bonds are made. Most biological reactions are exothermic
Metabolism Competitive Inhibition (CI) – a molecule, competitive inhibitor, competes directly with the usual substrate for the active site of an enzyme. The substrate will then have fewer encounters with the active site and rate of the chemical reaction will be decreases The competitive inhibitor must have a structure similar to the substrate to function in this way. CI may be reversible or irreversible Reversible may be overcome by increasing the substrate concentration
Metabolism Many enzymes inhibitors have been used in medicine Ethanol has been used to act as a competitive inhibitor for antifreeze poisoning Fomepizole, which is an inhibitor of alcohol dehydrogenase has also been used for antifreeze poisoning
Metabolism Non-competitive Inhibition – an inhibitor that does not compete for the enzyme’s active site. The inhibitor interacts with another site on the enzyme This causes a change in the shape of the enzyme’s activity site, making it non-functional Example is mercury binding to the sulfur group of the component amino acid of many enzymes Changes the shape of the enzyme which causes the inhibition of this enzyme
End Product Inhibition Metabolism End Product Inhibition Prevents the cell from wasting chemical resources and energy by making more of a substance than it needs. Metabolic pathways can be controlled by end product inhibition Metabolic reaction occur in an assembly line pattern The end product the assembly line shuts down This is done by inhibiting the action of the first enzyme
Inhibitor in Plasmodium The malarial parasite (Plasmodium) has developed resistance to most anti-malarial drugs Huge data bases are held in computers called bioinformatics Recent study found 5,655 chemicals that might act as an enzyme inhibitor in Plasmodium These were tested with nine Plasmodium enzymes and 6 inhibitors were found and are now being researched as anti-malarial drugs
The Energy in Food ATP – Adenosine Triphosphate Cellular Respiration – A chemical process that uses oxygen to convert the chemical energy stored in foods (organic molecules) into another form of chemical energy. Each covalent bond in a glucose, amino acid, or fatty acid represent stored chemical energy ATP – Adenosine Triphosphate Cells in plants and animals use ATP as their main energy supply
Oxidation & Reduction Oxidation Reactions Reduction Reactions Addition of oxygen atoms to a substance Removal of hydrogen atoms from a substance Loss of electrons from a substance Removal of oxygen atoms to a substance Addition of hydrogen atoms to a substance Additions of electrons to a substance In respiration, the oxidation is carried out by removing pairs of H atoms, plus their electrons. The H atoms are accepted by a carrier (NAD) therefore reduced.
Oxidation & Reduction Remember NAD!!!! FYI nicotinamide adenine dinucleotide
Phosphorylation Makes an organic molecule less stable More likely to react Usually ATP
Respiration Rapid Oxidation – rapid release of energy; wood burning Slow Oxidation – cells break down in a step by step process (metabolism) Cell Respiration involves the oxidation and reduction of electron carriers Oxidative phosphorylation - the culmination of a series of energy transformations that are called cellular respiration or simply respiration Phosphorylation of molecules makes them less stable (adding P from ATP)
Respiration Glucose (from glycogen stores) typically used first as the source of energy Glucose is acted on by a series of enzymes These enzymes catalyze a sequence of reactions in which covalent bonds are broken (oxidized) on at a time Each time a covalent bond is broken a small amount of energy is released. The goal is to trap that energy in a controlled way and form ATP molecules
Respiration No glucose? Lipids next Then amino acids/proteins (only in extreme cases- i.e. starvation)
Glycolysis Three Steps or Stages Stage 1: Glycolysis = “Splitting Sugar” First stage in breaking down glucose molecule Takes PLACE outside the mitochondria in the cytoplasm 2 ATP molecules are actually used to get things started. 2 ATP’s split the glucose molecule in half. (What do you call this???) Glucose enters the cell through the plasma membrane An enzyme modifies the molecule slightly, then another enzyme modifies the molecule more
Glycolysis A series of reactions that ultimately cleaves the 6 carbon glucose into 2 3-carbon molecules called pyruvate. Called an investment stage because two ATP’s are used up in the process 4 ATP molecules are produced at the end Net gain of 2 ATP Electrons are transferred to electron carries called NAD NADH is formed
Stages of Glycolysis 2 phosphate groups (from ATP) are added to glucose Adding a phosphate group is called Phosphorylation The hexose bisphosphate (the end product of stage 1) is split two form 2 molecules called tiose phosphate. 2 atoms of hydrogen are removed from each triose phosphate molecules. This is an oxidation. The energy released from oxidation is used to convert ADP to ATC,
Glycolysis Glycolysis (Payback Stage) Remember you used 2 ATP’s to start Gained 4 (net gain) End Result are: Two Pyruvic Acid Molecules Glucose + 2ATP 2 Pyruvic Acid molecules + 4ATP Pyruvic Acid Molecules still hold most of the energy of the original glucose molecules
Anaerobic Respiration All organisms start the pathway of breaking down glucose the same way Glycolysis (small net gain of energy no O₂ Anaerobic (without oxygen) Some derive their ATP completely without the use of oxygen and are referred to as anaerobic AKA – Fermentation 2 types of fermentation: Lactic Acid Fermentation (Humans / Mammals) Alcoholic Fermentation (yeast)
Alcoholic Fermentation Occurs in yeast cells A common single – cell fungus Uses alcoholic fermentation when oxygen is not present Begins with glycolysis Pyruvate converted to ethanol (2-C) and CO2 is released…both waste products for the organism Ethanol and CO₂ are produced as waste products Bakers’ and brewers’ yeast allows bread to rise and beer to be carbonated (most commercial beer is forcibly carbonated as well) as well as the alcohol.
Lactic Acid Fermentation Normally in aerobic organisms that find themselves in a situation where oxygen is no longer available—why you breather harder when you work out If a person’s exercise rate then exceeds his/her body’s capacity to supply oxygen some of the glucose will follow the anaerobic pathway called lactic acid fermentation Begins with glycolysis Pyruvate converted to lactate (3-C), no CO2 produced, no ATP produced Lactic acid fermentation allows glycolysis to continue with small gains of ATP in addition to ATP produced thorough the aerobic pathway
Lactic Acid Fermentation When O2 becomes available, lactate converted back to pyruvate and then pushed through the aerobic pathway
Anaerobic Respiration Lactic Acid Fermentation DOES NOT MAKE YOU SORE NO ATP IS MADE SO IT DOES CAUSE FATIGUE Anaerobic respiration produces less ATP but produces ATP at a rapid rate
Anaerobic & Aerobic Respiration Pyruvate produced in glycolysis can only be oxidized further with the release of more energy from it if oxygen is available Occurs in the mitochondria First stage is called link reaction Enzymes in the matrix of the mitochondria then catalyze a cycle of reactions called the Kreb cycle
Link Reaction Pyruvate from glycolysis is absorbed by the mitochondria. Enzymes in the matrix of the mitochondria remove hydrogen and carbon dioxide from pyruvate The hydrogen is accepted by NAD Removal of hydrogen is oxidation Removal of carbon dioxide is decarboxylation. Oxidative Decarboxylation The product of oxidative decarboxylation of pyruvate is an acetyl group, which is attached to coenzyme A to acetyl coenzyme A
Link Reaction
Aerobic Cell Respiration Aerobic Process – means it requires oxygen Cells that have mitochondria use aerobic pathway Cells Exchange: Oxygen into the cell Carbon Dioxide out of the cell Body: In your lungs – Blood Exchange: Oxygen (in) Carbon Dioxide (out)
Aerobic Cell Respiration Reviewing the Mitochondria Found in almost all Eukaryotic Cells The Mitochondria structure is key to its role in cellular respiration An example of form and function
Aerobic Cell Respiration Stage 2: The Kreb Cycle Named after biologist Hans Krebs Blame this guy
Aerobic Cell Respiration The Kreb Cycle Finishes the breakdown of Pyruvic Acid molecules to CO₂ - releasing more energy. Pyruvate loses a C as CO2, converted acetyl compound Said to be decarboxylated and oxidized Acetyl compound is attached to coenzyme A to form Acetyl Coenzyme A Enzymes are dissolved in the Matrix inside the Matrix Called the Fluid Matrix
Aerobic Cell Respiration The Kreb Cycle Acetyl Co A joins a 4 Carbon Acceptor molecule It is oxidized (removal of H)and coupled to the reduction of hydrogen carriers releasing CO₂ (Decarboxylation) Produces 2 CO₂ + 1 ATP per Acetyl CoA NADH and FADH₂ (another electron carrier) trap most of the energy and carry it to the cristae. At the end you are left with a 4 carbon acceptor molecule So the cycle can continue
Aerobic Cell Respiration Substrate – level phosphorylation – ATP produced
Aerobic Cell Respiration The Kreb Cycle Results: Glycolysis produces 2 Pyruvic Acid molecules from 1 glucose molecule Each Pyruvic Acid molecule makes 1 Acetyl CoA Cycle turns 2 TIMES Producing: 4 CO₂ + 2ATP’s
Aerobic Cell Respiration Electron Transport Chain & Chemiosmosis Occurs on the inner mitochondrial membrane and on the membranes of the cristae. First: (carrier molecules) NADH transfers electrons from the original glucose molecule to an electron transport chain. Remember: eˉ move to carriers that attract them more strongly This is why they move from carrier to carrier One carrier attracts them more than the one carrying; moving the eˉ to the inner mitochondria Some electron carriers act as proton pumps and use this energy to pump protons (H⁺) against the concentration gradient FAD comes in a little later (only 2 stages)
Aerobic Cell Respiration
Aerobic Cell Respiration Finally being pulled by oxygen at the end of the chain. 2 H⁺ combines with oxygen forming H₂O The transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping Chemiosmosis involves the movement of proton (hydrogen ions) to provide energy so that phosphorylation can occur Protons diffuse through ATP synthase to generate ATP O₂ is needed to bind with free protons to maintain H gradient forming water. Terminal e⁻ acceptor
Aerobic Cell Respiration Electron Transport Chain & ATP Synthase Action Chemiosmosis – the generation of ATP using energy released by the movement of hydrogen ions across the membrane
Aerobic Cell Respiration Electron Transport Chain & ATP Synthase Action ATP Synthase – Protein structures inside the mitochondria that receives the H⁺ uses that flow to convert ADP into ATP. Can make up to 34 ATP’s http://ib.bioninja.com.au/higher-level/topic-8-metabolism-cell/untitled/electron-transport-chain.html
Electron Transport Chain 34 ATP The Final Count Glycolysis 2 ATP Kreb Cycle 2 ATP Electron Transport Chain 34 ATP Maximum ATP for 1 Glucose Molecule = 38 Notice most ATP is made after Glycolysis and Kreb Cycle – which are anaerobic (without O₂)
Cellular Respiration Chemical Formula: Each glucose molecule yields 38 ATP molecules
Aerobic respiration