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 1oC

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 (C6H12O6)and forming bonds with less energy (CO2 and H2O).

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

animation

“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.

C6H12O6+ 6O2 6CO2+6H2O+ATP

• (hydrogen atom = one proton and one electron)

We don’t see e-, but we see H atoms.

C6H12O6+ 6O2 6CO2+6H2O+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

What is NAD+?

• nicotinamide adenine dinucleotide• Coenzyme from vitamin niacin• used to shuttle electrons in redox

reactions• Turns NAD+ into NADH

NAD+ to NADH

Electron Carrier

• A.k.a. “hydrogen carrier”• Electron taxi

cab NADH

(full with e-)

NAD+(empty)

e-

Lose electrons

•C4H6O5 C4H2O5

•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

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• 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)

• Krebstca (animation)

Where are ETC’s found?• In membranes of: –Mitochondria–Chloroplasts

Everything you wanted to know about the Mitochondrion

• Mitochondrion Animation

• Note many folds (cristae) of inner membrane

• This increases surface area

MitochondrionMatrix 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• Pyruvate Acetyl CoA CO2 + 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 GAIN2 ATP’s

• 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

CO2)

“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 CycleMcGraw-Hill ATP synthesis and ETC animation

1 ATP = 23 NADH2 = 6

1 FADH2 = 2

McGraw-Hill How the Krebs Cycle Works Animation

2 pyruvates

Chemiosmosis and ETC

• Flow of e- from NADH + FADH2 shuttle down the ETC to a final electron acceptor (oxygen)• Each of the O2 combines with 2 e- and 2

H+ to form H2O• Energy from e- transports H+ ions across

the inner membrane so ADP + P forms ATP

ETC and CHEMIOSMOSISMost 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+• FADH2 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

• 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 O2) 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+)

• Student Recommended Cell Resp Animation• ETC (VCAC) NDSU Virtual Cell Animations 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 calledATP Synthasein inner membrane

World’s smallest rotary motor

ChemiosmosisPowers Most of ATP Produced in the breakdown of glucose

• Glycolysis -2 ATP• Krebs Cycle - 2 ATP• Chemiosmosis/ ETC - 34 ATP

Cellular Respiration Equation

C6H12O6 + 6O2 > 6CO2 + 6H2O + ATP

Where does all the ATP come from?

•1 NADH = 3 ATP•1 FADH2 = 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’sGlycolysis

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 FADH2 (= 4 ATP)

2 ATPTotal YieldGlycolysis produces 2 ATPaerobic 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 CO2 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 CO2

• 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 O2 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.