6.1 Ultimate source of energy Photosynthesis and Cellular Respiration-how related?
Breathing and Cellular Respiration Breathing: how our body inhales and exhales to take in oxygen and release carbon dioxide Cellular Respiration: how our cells break down food sources (ie., glucose) to produce energy (ATP).
Respiration Really is... Cellular respiration = breakdown of organic molecules (for energy) in the presence of oxygen (in mitochondrion)
6.3 Cellular Respiration Equation Is this endergonic or exergonic?
Cellular Respiration Equation Is this endergonic or exergonic? Glucose breaks bonds and gives off energy (as seen on right side of the equation). ATP
Electron Carrier A.k.a. “hydrogen carrier” Electron taxi cab NADH (full with e-) NAD+ (empty) e-
Lose electrons C 4 H 6 O 5 C 4 H 2 O 5 Oxidized Lose e- (H) NAD+ NADH Reduced Gain e- (H)
Which has more energy? NAD+ or NADH? Answer: NADH What would the enzyme dehydrogenase do? Strips two H from NADH
NAD + NADH Can NAD + be recycled? Yes McGraw-Hill NAD+ Animation McGraw-Hill NAD+ Animation
Electron Transport Chain Organic molecules with an abundance of C-H bonds are a source of e- with a potential to fall closer and closer to oxygen. An e- loses its potential when it shifts from a less electronegative atom (doesn’t attract e- as much) to a more electronegative atom (attracts e- more).
ETC Animation of Energy Release from an Electron Transport System Animation of Energy Release from an Electron Transport System Electron Transport Chain Electrons are passed from the hydrogen carrier NADH to oxygen from one molecule to another
What keeps… The electrons moving down the chain? Each e- carrier molecule has greater affinity for e- than its uphill neighbor Electron Transport System and ATP Synthesis (little movie) Electron Transport System and ATP Synthesis Krebstca (animation) Krebstca
Where are ETC’s found? In membranes of: – Mitochondria – Chloroplasts
Everything you wanted to know about the Mitochondrion Mitochondrion Animation Mitochondrion Animation Note many folds (cristae) of inner membrane This increases surface area
Mitochondrion Matrix contains mDNA (mitochondrial), enzymes, and ribosomes-site of Krebs cycle
6.6 3 Stages of Cellular Respiration: 1. Glycolysis- occurs in cytoplasm Glucose 2 mols. of pyruvate 2. Pyruvate oxidation and citric acid cycle - occurs in mitochondrion PyruvateAcetyl CoA CO 2 + NADH 3. Oxidative phosphorylation-in mitochondrion uses ETC and chemiosmosis in mitochondrion to make lots of ATP
Cellular Respiration Cellular respiration converts the potential energy of glucose into usable energy of ATP. THERE ARE 2 WAYS THE ATP IS GENERATED.
2 Ways to Make ATP Substrate-Level Phosphorylation (without a membrane; it occurs in the cytoplasm or matrix of mitochondrion with help of an enzyme) Oxidative Phosphorylation diffusion of particles through a membrane produces ATP
Substrate-Level Phosphorylation Use of enzymes (not membranes) to join P to ADP to make ATP
Oxidative Phosphorylation Uses a membrane (of mitochondrion or chloroplast) to pass electrons down the electron transport train to a final electron acceptor.
6.7 GLYCOLYSIS A. Energy Investment Phase – Glucose is phosphorylated into 2 molecules of G3P – Uses 2 ATP
Glycolysis Start with 6-carbon glucose and breaks into two 3-carbon pyruvic acid molecules (or pyruvate) glucose + 2 NAD+ + 2 ADP + 2 Pi 2 pyruvate + 2 NADH + 2 ATP
Glycolysis actually has 9 steps…but you only need to learn that these molecules formed between glucose and pyruvic acid are called intermediates
One Intermediate G3P = PGAL = Glyceraldehyde 3-phosphate =Phosphoglyceraldehyde
Glycolysis: What do I need to know? Needs 2 ATP to get started Makes 4 ATP Net Gain of 2 ATP Splits glucose into 2 pyruvates Makes NADH NET GAIN 2 ATP’s Glycolysis Animation Glycolysis Animation (nice big carbons)
But... Pyruvic acid itself does not enter the Krebs cycle Say What?
“Grooming” Pyruvic Acid Haircut and Conditioning “HAIRCUT” As NADH is reduced to NAD+…pyruvic acid is oxidized (carbon atom removed as CO 2 ) “CONDITIONING” Coenzyme A (from B vitamin) joins the 2-c fragment MAKES-Acetyl Coenzyme A or CoA
Ready to GO The Acetyl-CoA is now ready to enter the Krebs cycle Hans Krebs (1900-1981) Yeah, he got a Nobel Prize, too
Krebs Cycle McGraw-Hill ATP synthesis and ETC animation McGraw-Hill ATP synthesis and ETC animation 1 ATP = 2 3 NADH 2 = 6 1 FADH 2 = 2 McGraw-Hill How the Krebs Cycle Works Animation 2 pyruvates
Chemiosmosis and ETC Flow of e- from NADH + FADH 2 shuttle down the ETC to a final electron acceptor (oxygen) Each of the O 2 combines with 2 e- and 2 H+ to form H 2 O Energy from e- transports H+ ions across the inner membrane so ADP + P forms ATP
ETC and CHEMIOSMOSIS Most ATP production occurs by oxidative phosphorylation Occurs along the inner membrane of the mitochondrion
The electron carriers bring e- and H+ FORMED IN THE KREBS CYCLE NADH brings 2 e- and H+ FADH 2 brings 2 e- and 2H+
Why do the electron carriers unload their electrons? Oxygen is the final electron acceptor because it has a high electronegativity (attractions to electrons). Electron Transport -Electron Carriers – Animation (3:33) –nice explanation of all parts of ETC Electron Transport -Electron Carriers – Animation Another ETC Chemiosmosis Animation
Electron Carriers Transfer of Energy of Electron Carriers Animation What are the two electron carriers? What do they drop off in the inner membrane? What do they drop off that diffuses through the inner membrane?
Where do all the H+ ions that collected in the intermembrane space move through, down the gradient?
ETC Electron transfers (redox) between an electron donor (such as NADH) and an electron acceptor (such as O 2 ) with the transfer of H+ ions (protons) across a membrane. ETC animation (Zoom in on nice animation as the electron carriers drop off their e- and H+) ETC animation Student Recommended Cell Resp Animation ETC (VCAC) NDSU Virtual Cell Animations ATP Synthase (VCAC) ETC (VCAC)ATP Synthase (VCAC)
Where does all the ATP come from? 1 NADH = 3 ATP 1 FADH 2 = 2 ATP
Review of ATP YIELD (Ideally) Need 4 ATP to start glycolysis Glycolysis makes 2 ATP Krebs Cycle makes 2 ATP ETC/Chemiosmosis makes 34 ATP TOTAL about 38/molecule of glucose
TOTAL ATP’s Glycolysis 2 ATP (borrowed 2 to start, made 4 ATP, net of 2 ATP) *2 NADH (= 4 ATP; 6 ATP made but 2 ATP used to move across the membrane) Formation of Acetyl CoA *2 NADH (= 6 ATP) *sent to ETC Krebs Cycle *6 NADH (= 18 ATP) *2 FADH 2 (= 4 ATP) 2 ATP Total Yield Glycolysis produces 2 ATP aerobic respiration produces 34 more ATP
POISONS Rotenone-binds to first ETC protein to prevent e- passing on Cyanide-bind to fourth protein in ETC (was in famous Tylenol tampering in 1982)
POISONS Oligomycin -blocks H+ through ATP synthase DNP- enormous increase in metabolic rate – all energy lost as heat (once given as a weight loss pill)
Lactic Acid Fermentation In animals (muscles) if lack of oxygen Note: no CO 2 formed
The lactic acid causes stiffness that goes away after a few days. This is due to the stopping of strenuous activity to allow aerobic conditions to return to the muscle. The lactic acid can be converted into ATP via the normal aerobic respiration pathways.
Fermentation regenerates NAD+ (so it can be used to pick up H+ and e- again)
TYPES OF ANAEROBES OBLIGATE ANAEROBES –require anaerobic conditions FACULTATIVE ANAEROBES – can use either oxygen or not, but will use aerobic conditions if O 2 first is present Bacillis anthracis Clostridium difficile
Tube 1: Obligate Anaerobe -- note the absence of growth in the top portion of the broth where oxygen is present. Tube 2: Obligate Aerobe -- note the growth is only in the top portion of the tube where oxygen is present. Tube 3: Aerotolerant -- note the uniform growth from top to bottom. Tube 4: Facultative -- note the uneven distribution of growth from top to bottom (more growth at the top). Tube 5: Obligate Aerobe -- note the growth is only in the top portion of the tube where oxygen is present.