Cellular Respiration The Energy in Food

Cellular Respiration Cellular Respiration – A chemical process that uses oxygen to convert the chemical energy stored in foods (organic molecules) into another form of chemical energy. ATPATP – Adenosine Triphosphate –Cells in plants and animals use ATP as their main energy supply

The Energy in Food Rapid Oxidation Rapid Oxidation – the release of chemical energy by burning This reaction is not controlled by enzymes –Results consist of an uncontrolled energy release

The Energy in Food Slow Oxidation Slow Oxidation – the release of energy in a controlled fashion. Enzymes catalyze a sequence of events that cause covalent bonds to break one at a time. MetabolismThis is Metabolism !

Photosynthesis / Cellular Respiration Recycle a common set of chemicals: Water Carbon Dioxide Oxygen Glucose (Organic Compounds)

ATP Phosphate part is most important Because of the negative charge on all the attached oxygens, there is a lot of potential energy in these bonds Removing the last phosphate group makes the molecule much “happier” (chemically stable)

ATP to ADP “renewable” molecule;ATPADP, energy to do this comes from food you eat

Respiration Organic compounds contained stored (potential) chemical energy in their bonds When that energy is released, cells can use it for metabolism Glucose (from glycogen stores) typically used first as the source of energy No glucose? Lipids next then amino acids/proteins (only in extreme cases- i.e. starvation)

Respiration Controlled release of energy from organic compounds in cells to form: Adenosine Triphosphate (ATP) Glycolysis is the first step in respiration Two types of respiration: Aerobic (uses oxygen) Anaerobic (without oxygen) 2 types of anaerobic respiration: Lactic Acid Fermentation Lactic Acid Fermentation (Humans / Mammals) Alcoholic Fermentation (yeast)

Anaerobic Respiration 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 When O 2 becomes available, lactate converted back to pyruvate and then pushed through the aerobic pathway Pyruvate converted to lactate (3-C), no CO 2 produced, no ATP produced

Anaerobic Respiration Lactic Acid Fermentation DOES NOT MAKE YOU SORE NO ATP IS MADE SO IT DOES CAUSE FATIGUE

Anaerobic Respiration Alcoholic Fermentation Occurs in yeast cells This is a “normal” situation for the yeast Pyruvate converted to ethanol (2-C) and CO 2 is released…both waste products for the organism Bakers’ and brewers’ yeast allows bread to rise and beer to be carbonated (most commercial beer is forcibly carbonated as well)

Fermentation in Microorganisms

Oxygen and Cellular Respiration Breathing and Cellular Respiration Aerobic Process Aerobic Process – means it requires oxygen Cells Exchange: –Oxygen into the cell –Carbon Dioxide out of the cell Body: In your lungs – Blood Exchange: – Oxygen (in) – Carbon Dioxide (out)

Cellular Respiration Chemical Formula: 38 ATPEach glucose molecule yields 38 ATP molecules

Reviewing the Mitochondria Found in almost all Eukaryotic Cells –The Mitochondria structure is key to its role in cellular respiration –Have their own DNA –Have their own ribosomes

Mitochondria Structure: Made – up of two membranes – There is a space between the inner and the outer membrane Matrix – the highly folded inner membrane enclosing a thick fluid Inside the inner membrane you find many of the enzymes involved in cellular respiration – folds of the membrane allows a Large Surface Area for reactions to occur. –MAXIMIZES the area for ATP production

Cellular Respiration First: Metabolism – all chemical processes in a cell Metabolic Pathways – Term given to cellular respiration; because it is made up of a series of reactions (thus the term pathways) Specific enzymes catalyzes each reactions in a pathways

The Metabolic Pathways 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. Investment Stage Electrons are then transferred to a carrier molecule called NAD NAD then turn into NADH At this point 4 ATP are produced Now your up by 2 ATP

The Metabolic Pathways 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

The Metabolic Pathways Stage 2: The Kreb Cycle Named after biologist Hans Krebs Blame this guy

The Metabolic Pathways The Kreb Cycle Finishes the breakdown of Pyruvic Acid molecules to CO ₂ - releasing more energy. –Pyruvate loses a C as CO2, becomes acetyl- CoA Enzymes are dissolved in the Matrix inside the Matrix –Called the Fluid Matrix

The Metabolic Pathways Acetyl Co A joins a 4 Carbon Acceptor molecule Produces 2 CO ₂ + 1 ATP per Acetyl CoA –NADH and FADH ₂ (another electron carrier) trap most of the energy –At the end you are left with a 4 carbon acceptor molecule So the cycle can continue The Kreb Cycle

The Metabolic Pathways

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 CO ₂ + 2ATP’s

The Metabolic Pathways Electron Transport Chain & ATP Synthase Action 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 –Finally being pulled by oxygen at the end of the chain. –2 H ⁺ combines with oxygen forming H ₂ O

The Metabolic Pathways 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

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 O ₂ )

Aerobic respiration

Types of Respiration Occurs in the absence of Oxygen Aerobic Respiration Occurs in presence of Oxygen Occurs in the cells’ cytoplasm Occurs in the cells’ mitochondria Yields small amount of ATP (2 molecules) per molecule of glucose Yields large amount of ATP (38 molecules) per molecule of glucose Does not involve fermentation Involves fermentation of pyruvate to lactate in muscles/CO2 & ethanol in plant & yeast Anaerobic Respiration

Comparison between Aerobic & Anaerobic Respiration -Animals