Chapter 9: Cellular Respiration and Fermentation

Essential Knowledge 2.a.1 – All living systems require constant input of free energy (9.1-9.5). 2.a.2 – Organisms capture and store free energy for use in biological processes (9.1-9.5).

Cellular Respiration - Preview Def - The process of releasing energy/ATP from food Food - Stored energy in chemical bonds (provides fuel) ATP - Useable energy for cellular processes Wastes – CO2 and H2O Mitochondrion store most of equipment needed for rxn

Respiration (Rs) - Equation C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy (ATP or heat) Rxn is spontaneous (-∆G) The energy is released (exergonic) from the bonds in the org molecules Remember: Org molecules store energy in their arrangement of atoms Org molecules can be carbs, proteins or fats/lipids

Focus of Chapter Cellular Rs Other Purpose - what is the reaction suppose to do for the cell? Location - where does it occur? Requirements - what is needed to make it run? Products - what does it produce? Other Fermentation, Redox

Fuel? What is used? Organic molecules with a large amt of hydrogen make great fuel! Why? H becomes oxidized (only has one e-) very easily and energy is released Remember: Carbs, fats, proteins are storage bins for e- associated with hydrogen

Oxidation - definitions Loss of electrons Loss of energy Loss of hydrogens from carbons Ex: Na+ (of NaCl)

Food and Oxidation Food (organic molecules) contain a lot of H atoms These serve as great long-term fuels Why? Because H becomes easily oxidized (releases energy frequently)

Reduction - definitions Gain of electrons (REDUCING + charge) Gain of energy Gain of hydrogens to carbons Ex: O is often reduced! Why? Because electrons are pulled closer to O

Redox reactions

Equation for Rs Oxidized Reduced C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy (ATP/heat) General Redox Equation: Xe- + Y  X + Ye- Reduced

Redox reactions Involves transfer of e- and energy release Sometimes doesn’t involve complete transfer Red and Oxd reactions are usually paired or linked together. Why?Because e- transfer requires donor and acceptor Many of the reactions will be done by phosphorylation Redox video

Phosphorylation Adding a phosphate group to a molecule Two types: Ex: ATP cycle (add P to ADP = ATP) Two types: Oxidative AND substrate-level The phosphate group adds “energy” to the molecule for chemical reactions (think ATP cycle) Endergonic rxn

Phosphorylation

Cell Respiration – 3 parts 1. Glycolysis 2. Krebs Cycle 3. Electron Transport Chain **Use page 167 as a starting point: Cellular Respiration - A Preview

STEP 1 Glycolysis Glyco- glucose -lysis: to split Formula for glucose: C6H12O6 Universal step in all Rs types. Likely the earliest type of cell energy processes Overview: Glucose splits into 2 3-C sugars (then oxidizes to form pyruvate)

Glycolysis Function - To split glucose and produce NADH and ATP ATP made by substrate-level phosphorylation Enzyme transfers phosphate group from substrate/reactant to ADP to make ATP Location – Cytoplasm of the cell

Electron Carrier Compounds Molecules that transport or shuttle electrons within the cell Exist in two forms: Oxidized (ox) Reduced (red) Ex: NAD and FAD

NAD Nicotinamide Adenine Dinucleotide NAD+ + 2 e- NADH NAD+ = oxidized form NADH = reduced form* *Reduced by e- from food oxidation

Glycolysis Requirements Glucose 2 ATP 4 ADP 2 NAD+ Can occur with or without O2

Notice: No CO2 made during this step! Glycolysis Intro Glycolysis - Products 2 Pyruvic Acids (a 3-Carbon acid) 2 ADP, 4 ATP, 2 NADH NET RESULT: 2 ATP per glucose 2 NADH 2 pyruvate H2O Notice: No CO2 made during this step!

STEP 2 Krebs Cycle Oxidizes fuel from pyruvate molecules Also called: Remember? Pyruvate formed during glycolysis Also called: Citric Acid Cycle Tricarboxylic Acid Cycle

Krebs Cycle Function: Oxidize pyruvic acid (to make CO2 ) Produces: NADH and FADH2 Location: Mitochondria matrix Before Krebs: Acetyl CoA must be formed Acetyl CoA is needed to actually start Krebs

Pyruvate moved into mito? Why? How? Pyruvate is moved into mitochondria (from cytoplasm) Why? This is where the 2nd step occurs (specific enzymes are in mito) Serves as a checkpoint Uses active transport and transport proteins. Why? Pyruvate is a charged molecule!

Formation of Acetyl CoA

Krebs Cycle Requirements Pyruvic acid (3C acid) Acetyl coenzyme A 4 NAD+ 1 ADP 1 FAD Double this list for each glucose

LOADS of energy stored in these molecules Krebs Cycle Intro Krebs Cycle Products 3 CO2 Acetyl CoA 4 NADH 1 FADH2 1 ATP Double this list for each glucose Made from pyruvate LOADS of energy stored in these molecules

Krebs Cycle notes Notice: Does NOT require O2 Only 1 ATP made per cycle Produces most of the cell's energy in the form of NADH and FADH2 Does NOT require O2

Comment about ATP The ATPs produced directly in Krebs Cycle and Glycolysis are by: Substrate-level phosphorylation The P group is transferred from a substrate to ADP Making ATP

At this point… After the Krebs and glycolysis cycles, the cell has made a total of 4 ATP. Remember: some ATP had to be used to power the cycles. Most energy (at this point) comes from NADH and FADH2

Electron Transport System STEP 3 ETC/S or Electron Transport Chain This is a collection of proteins that are structurally linked Located in inner membrane of mito Folding of mito (cristae) allows for lots of places (large surface area!) for ETC to occur

ETC/S Uses sets of Cytochromes Fe (Iron)-containing proteins to pass electrons The Cytochromes alternate between Red and Ox forms and pass electrons down to O2 Remember: LEO, GER; LEO the lion goes GER Losing Electrons is Oxidation; Gaining Electrons is Reduction

As e- moves down the ETC, free energy decreases

ETC/S Function: Convert NADH and FADH2 into ATP Location: Mitochondria cristae/folds

ETC Requirements NADH or FADH2 ADP O2 We finally see the need/requirement of Oxygen

ETC Products NAD+ and FAD ATP (LOTS!!!) H2O Remember: Water was also produced during glycolysis ETC explanation

ETC - ATP Yields Each NADH  3 ATP Each FADH2  2 ATP TOTAL: 34 ATP

Chemiosmotic Hypothesis ETC energy is used to move H+ (protons) across the mito/cristae membrane ATP is generated as the H+ diffuse back into the matrix

ATP Synthase Enzyme An enzyme that uses the flow of H+ to make ATP Works like an ion pump in reverse, or like a waterwheel under the flow of H+ “water” Power source: H+ concentration difference on opposite sides of mitochondrial membrane

Oxidative Phosphorylation ATP synthase uses oxidative phosphorylation to make ATP during ETC Uses H ions to make ATP and water (using Oxygen)

ATP Synthase

Alcoholic Fermentation Done by yeast A kind of fungus Used in brewing beer, winemaking, and baking CO2 bubbles generated give: Bread a rising effect Wine/Beer the carbonated effect

Alcoholic Fermentation Uses only Glycolysis An incomplete oxidation - energy is still left in the products (alcohol) Does NOT require O2 Produces ATP (when O2 is not available)

Alcohol

Lactic Acid Fermentation Uses only Glycolysis An incomplete oxidation - energy is still left in the products (lactic acid) Does NOT require O2 Produces ATP (when O2 is not available)

Lactic acid

Lactic Acid Fermentation Done by human muscle cells under oxygen debt Lactic Acid is a toxin and can cause soreness and stiffness in muscles Oxygen intake can’t keep up with sugar breakdown Used in dairy industry (yogurt/cheese) Also used to produce methanol and acetone

Fermentation - Summary Way of using up NADH so Glycolysis can still run Provides ATP to a cell even when O2 is absent

Fermentation *Alcoholic OR *Lactic acid

Aerobic vs Anaerobic Aerobic - Rs with O2 Anaerobic - Rs without O2 Aerobic - All three Rs steps Anaerobic - Glycolysis only

Strict vs. Facultative Strict - can only do Rs this one way Either aerobic OR anaerobic-NOT both! Facultative - can switch types depending on O2 availability Ex - yeast

Question?? Since yeast can do both aerobic and anaerobic Rs, which is the better process if given a choice? Hint: Check the ATP yields from both processes.

ATP yields by Rs type Anaerobic - Glycolysis only gets 2 ATPs per glucose Aerobic - Glycolysis, Krebs, and ETC. Generates many more ATPs per glucose.

Aerobic ATP yield Glycolysis - 2 ATPS, 2 NADHs Krebs - 2 ATPS, 8 NADHs, 2 FADH2 Each NADH = 3 ATP Each FADH2 = 2 ATP

Aerobic ATP Sum Max = 38 ATPs per glucose 10 NADH x 3 = 30 ATPs 2 FADH2 x 2 = 4 ATPs 2 ATPs (Gly) = 2 ATPs 2 ATPs (Krebs) = 2 ATPs Max = 38 ATPs per glucose

However... Some energy (2 ATP) is used in shuttling the NADH and pyruvate from Glycolysis into the mitochondria Actual ATP yield ~ 36/glucose

Yeast Would rather do aerobic Rs; This has 18x more energy per glucose than anaerobic But, anaerobic will keep you alive if oxygen is not present.

Importance of Rs Convert food to ATP Living orgs use ATP to fuel body processes Ex: reproduction, cell division Provides materials for use in other cellular pathways

Other Respiration Items of Importance Alcohol Industry - almost every society has a fermented beverage Baking Industry - many breads use yeast to provide bubbles to raise the dough

Alcohol Matching Game! Sugar Cane Gin Barley Rum Grapes Wine Juniper Cones Vodka Agave Leaves Beer Rice Tequila Potatoes Saki

Summary Identify the basic chemical equation for cellular respiration. Identify the main reaction sequences of cellular respiration. Recognize the location, function, requirements, and products, for each cellular respiration reaction. Recognize and be able to discuss the chemiosmotic model for ATP generation. Recognize the reactions and importance of fermentation. Contrast and compare aerobic and anaerobic respiration. Identify the biological and commercial importances of respiration.

Exclusion Statements You do NOT need to memorize the steps in glycolysis and the Krebs cycle, the structures of the molecules, or the names of the enzymes that are involved. You do NOT need to memorize the names of the specific electron carriers in the electron transport chain (ETC).