HONORS BIOLOGY CHAPTER 6 Breaking Down Glucose. 6.1 Ultimate source of energy Photosynthesis and Cellular Respiration-how related?

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HONORS BIOLOGY CHAPTER 6 Breaking Down Glucose

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

Fill in the Blanks

6.4 Energy Units Kilocalories (kcal) = Calories = 1000 calories = quantity of heat needed to raise 1 kg of water by 1 o C

Daily Human Needs 2,200 kcal of energy per day Walking at 3 mph (burn 245 kcal/hour), how far would you have to travel to “burn off” the equivalent of a slice of pizza of about 475 kcal?

Daily Human Needs 2,200 kcal of energy per day Walking at 3 mph (burn 245 kcal/hour), how far would you have to travel to “burn off” the equivalent of a slice of pizza of about 475 kcal? ~2 hours

6.5 Where does the energy come from? The bonds (electrons) with more energy (C 6 H 12 O 6 )and forming bonds with less energy (CO 2 and H 2 O).

6.3 Burn 1 glucose molecule with fire ~ 100 ATP molecules 100% energy released BUT, in cells only about 34% goes to use in ATP molecules The rest is lost as heat

6.5 Cell’s Slow Burn Cells tap energy from electrons “falling” gradually from organic fuels to oxygen. This is slower and more controlled than just burning it with fire.

What drives this to happen? OXYGEN A strong tendency to pull electrons from other atoms Oxygen is the “ultimate electron acceptor”

REVIEW: Catabolic Pathways Metabolic pathways that release stored energy by breaking down complex molecules

To what molecule is the energy shuttled? ATP ADP to ATP anim anim ation ADP to ATP anim ation

“Redox reaction” Oxidation – Reduction Reaction Oxidation loss of electrons from one substance Loss of H NADH NAD+ Reduction addition of electrons to another substance Gain of H NAD+ NADH

We don’t see e-, but we see H atoms. C 6 H 12 O 6 + 6O 2 6CO 2 +6H 2 O+ATP (hydrogen atom = one proton and one electron)

We don’t see e-, but we see H atoms. C 6 H 12 O 6 + 6O 2 6CO 2 +6H 2 O+ATP (hydrogen atom = one proton and one electron) LEO = loss of electrons = reduction

How to remember… "Leo goes Ger” Loss of electrons = oxidation Gain of electrons = reduction

Fill in the Blanks: H+ 2H reduction NAD+ NADH oxidation becomes oxidized becomes reduced carries 2 e- b

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)

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 B. Energy Payoff Phase – 2 G3P break down to 2 pyruvates – Two NAD+ add 2 electrons 2 NADH + 2H+ -4 ATP form, net gain of 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?

Pyruvate Oxidation or “Cut and Groom”

“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

Pyruvate Oxidation: “Cut and Groom”

Krebs Cycle Only 2-C of acetyl enters (Coenzyme A is recycled) Occurs in mitochondrial matrix

Krebs Cycle Occurs in the Matrix This one

OAA = 4-C (recycled) + 2-c acetyl 6-C citric acid (temporary)

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

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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)

COUNT THE TOTAL ATP’s

“Down the Gradient” Note more H+ ions on intermembrane side of the membrane The movement “down the gradient” produces energy MATRIX INNER MEMBRANE

Chemiosmosis and ETC H+ ions can only pass through a special port ATP synthase (see knobs on cristae)

Chemiosmosis Diffusion of excess H+ ions across a membrane from high to low concentration Generates energy to cause ADP + Pi = ATP

Where does chemiosmosis occur? In Protein Complexes called ATP Synthase in inner membrane World’s smallest rotary motor

Chemiosmosis Powers Most of ATP Produced in the breakdown of glucose Glycolysis -2 ATP Krebs Cycle - 2 ATP Chemiosmosis/ ETC - 34 ATP

Cellular Respiration Equation C 6 H 12 O 6 + 6O 2 > 6CO 2 + 6H 2 O + ATP

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

NOT JUST FOR GLUCOSE

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)

Lactic Acid Foods Yogurt kimchee sauerkraut soy sauce sourdough bread

Alcoholic Fermentation: In yeast, bacteria Forms ethanol and CO 2 Also, NADH regenerated back to NAD+ Grapes fermenting

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.

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