Breathing and Cellular Respiration

INTRO

• Fast and slow twitch muscles

What kind of runner are you?

• LONG DISTANCE RUNNING

• Slow-twitch fibers

• for repeated long contractions

• SPRINTING or WEIGHT LIFTING

• Fast-twitch fibers

• Contract more quickly and powerfully

What makes these muscle fibers so different?

• SLOW TWITCH

• breaks down glucose to get ATP AEROBICALLY (using oxygen)

• FAST TWITCH

• breaks down glucose to get ATP ANAEROBICALLY(not using oxygen)

SLOW MUSCLES

• 1. Thin fibers

• 2. have many mitochondria

• Many myoglobin

FAST MUSCLES

• Thicker fibers

• Fewer mitochondria

• Less myoglobin

• (“white meat)

What happens if not enough oxygen is available?

• Glucose is not completely broken down and lactic acid is formed (a larger molecule) that makes muscles ache

Big Question for Chapter 6

• How do our cells obtain O2 for cellular respiration and dispose of CO2?

6.1 Breathing

• Isn’t that how we obtain oxygen?

• Breathing = taking in oxygen in our lungs and removing carbon dioxide as we exhale

Respiration Really is...

• Cellular respiration = breakdown of organic molecules (for energy) in the presence of oxygen (in mitochondrion)

6.2 Cellular Respiration

• C6H12O6 + 6O2 > 6CO2 + 6H2O + ATP

Glucose Bank

• Break glucose bonds

• Stored in ATP

glucose

ATP

Glucose contains Energy:

• 1 gram glucose = 4 kcal of energy

• What are kcal? Kilocalories

• 1 kilocalorie = 1000 calories

6.3 Need heat to stay alive

• 75% of energy of daily food just to maintain

• 2,200 kcal of energy per day needed for average adult

Calculate• Walking at 3

mph, how far would you have to travel to “burn off” the equivalent of an extra slice of pizza, which has about 475 kcal?

• HINT: (p. 91) Walking 3 mph consumes per hour 158 kcal

• 475/158 = 3 hrs.

• 3 mph X 3 = 9mi

6.4 Just how DO our cells extract energy from organic fuel

molecules?

• The glucose is dismantled and the energy stored in the bonds is carried by electrons.

We don’t see e-, but we see H atoms.

• C6H12O6 + 6O2 > 6CO2 + 6H2O + ATP

• (hydrogen atom = • one proton and one electron)

What drives this to happen?

• OXYGEN

• A strong tendency to pull electrons from other atoms

6.5 Redox Reaction

•Movement of electrons from one molecule to another is an oxidation-reduction reaction

Redox reaction

• Oxidation

• loss of electrons from one substance

• Loss of H

• Reduction

• addition of electrons to another substance

• Gain of H

• "Leo goes Ger”

• Loss of electrons = oxidation

• Gain of electrons = reduction

Key Players of Redox Reactions

• Dehydrogenase

• Enzyme

• Remove H atoms

• NAD+• nicotinamide

adenine dinucleotide

• coenzyme• used to shuttle

electrons

How NADH becomes a “Hydrogen Carrier”

• NAD+ + 2H dehydrogenase NADH2

• picks up 2 e- and

• e- 2H+ and 2e-

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

• Empty With e-/H

e-

NADH

NAD+ NADH

p. 93

• C4H6O5 C4H2O5

• Oxidized

• NAD+ NADH

• Reduced

How do we get energy?• Big molecules in food

break apart• Released electrons

carried to NADH• Energy to ATP’s

• You can now use ATP energy

6.6

• Which has more energy?

NAD+ NADH

Why?

NADH has picked up an e-

6.6 ETC• Electron

Transport Chain

• Pass e- from higher energy to lower energy state

NADH brings e-

NAD+

So…

•NAD+ can be recycled over and over

ETC

• ETC Animation (click)

• Note each carrier molecule has a greater affinity for e- than its uphill neighbor

Where is the ETC?

• Inner membrane of the Mitochondrion

Sing the ETC Song

• To the tune of “Buffalo Gals Won’t you Come Out Tonight”?

6.7 Chemiosmosis• Movement of solutes across a

membrane from where they are MORE concentrated to where they are LESS concentrated.

• Movement of H+ ions (click here to see the proton H+ pumps)

“Down the Gradient”Note more H+ ions on one side of the membrane

Went “against the gradient” and see energy was used to do this

Chemiosmosis• Diffusion of

excess H+ ions across a membrane from high to low concentration

• ADP + Pi = ATP

ATP Synthase• ATP Synthase

Animation (click here to see the ATP synthase move H+ ions “against the gradient”)

• ATP Synthase Animation (click here)

Makes ATP

• Energy is generated from the movement of H+ ions …enough to cause a phosphate to join ADP to form ATP

Chemiosmosis and ETC working together on inner membrane

• ETC and Chemiosmosis Together

NADH and FADH2 carry protons (H+) and electrons (e-) to

the electron transport chain

Mitochondrion: Site of Cellular Respiration

• Mitochondrion Cellular Respiration (be sure to see the cool rotating ATP Synthase and the end of the program)

• Peter Mitchell (1920 - 1992)

• Developed the theory of chemiosmosis

• Nobel Prize 1978

2 Ways to Make ATP

• Substrate-level phosphorylation

• does not involve a membrane

• makes only small amounts of ATP

• Chemiosmosis• diffusion

through a membrane of particles produces more ATP

6.8 3 Stages of Cellular Respiration

1. Glycolysis

2. Krebs Cycle

3. ETC/Chemiosmosis

Glycolysis

-Breaks down glucose into pyruvic acid-Occurs in cytoplasm-means “splitting of sugar”

Glycolysis

• Start with 6-carbon glucose and breaks into two 3-carbon pyruvic acid molecules (or pyruvate)

Glycolysis Animation

• Glycolysis actually has 9 steps…but you only need to learn that these molecules formed between glucose and pyruvic acid are called

• intermediates

Glycolysis: What do I need to know?

• Needs 2 ATP to get started

• Makes 4 ATP

• Splits glucose into two pyruvates

• Makes NADH (an e- carrier)

• NET GAIN2 ATP’s

But...

•Pyruvic acid itself does not enter the Krebs cycle

6.10 “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 fragmen

MAKES-Acetyl Coenzyme A or

CoA

6.11 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

• Only 2-C of acetyl participates

• (Coenzyme A is recycled)

• Occurs in mitochondrial matrix

Also Called TCA cycle

tricarboxylic acidwhich is also citric acid (the other 4-C)…so also called citric acid cycle

Krebs cycle (cont.)

• strips off a carbon as CO2

• makes 4 ATP

• makes 10 NADH

• makes 2 FADH2

One cycle

6.12 MitochondrionNote many folds (cristae) of inner membrane

This increases surface area

Electron Transport Chain in inner membrane of the Mitochondrion

Electron Carriers

• In Glycolysis

• NAD+

• In Cellular Respiration

• NAD+

• FAD

Final Electron Acceptor

•Oxygen• It is what drives the reaction

and pulls the electrons away from their bonds.

Final Products

• Water (from oxygen and hydrogens)

• CO2 when it was pulled out of Krebs

cycle

• ATP formed mostly from chemiosmosis/ETC

6.12 Chemiosmosis/ETCPowers Most of ATP Produced

• Glycolysis -2 ATP

• Krebs Cycle - 2 ATP

• Chemiosmosis/ ETC - 34 ATP

• NET TOTAL = 38 ATP

Chemiosmosis and ETC

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

ATP synthase

• As H+ ions move through the ATP synthase port it powers the formation of ADP + Pi to ATP

• Animation of ATP

• synthesis in Mitochondria

OVERALL ANIMATION

• Cellular Respiration Animation and Explanation

Burn 1 glucose molecule

• ~ 100 ATP molecules

• 100% energy released

Glucose in the body

• Only about 40% goes to use in ATP molecules

• Rest lost as heat

6.15 YEAST FERMENTATION

• In yeast, can they make enough energy without oxygen?

• YES

• Is this aerobic or anaerobic?

• anaerobic

Remember the Yeast Lab?

• Put glucose with yeast and what were the two by-products?

• Carbon dioxide and ethyl alcohol

What was the side step?• NAD+ was replenished

• The taxi cab loses its e- and is now available to pick up more electrons. If all the taxi cabs are full, the reaction would stop.

NAD+

Alcoholic Fermentation

• Is using yeast or bacteria to convert glucose to alcohol.

Ethanol is Toxic to Yeast

• So what do they do with it?

• Yeast release the waste to the surroundings.

What happens if …

• The yeast makes too much ethanol?

• They die

X X

X X

Lactic Acid Fermentation

• In your muscles

• As you exercise, lactic acid is formed.

• You also breath out carbon dioxide.

Where does the lactic acid go?

• Carried to liver

• Here lactic acid is converted back to pyruvic acid.

Where is lactic acid used?

• Commercially:

• Lactic acid fermentation is used by bacteria in the dairy industry to produce:

Cheese and yogurt

Strict Anaerobes

• Require anaerobic conditions and are poisoned by oxygen

• Methanogens are strict anaerobes that release methane as a waste product of cellular metabolism. Many live in mud at the bottom of lakes and swamps because it lacks oxygen, and some (enteric bacteria) live in the intestinal tracts of animals

Facultative Anaerobes

• Can make ATP either by fermentation or by chemiosmosis, depending on whether oxygen is available or not

Facultative Example

• Vibrio parahaemolyticus - halophilic, facultative anerobic, rod bacterium that causes a foodborne illness known as seafood poisoning.

Making Beer

• Large fermentation tanks to make beer and wine have a one-way valve so no oxygen gets in…only the carbon dioxide out.

6.13 ROTENONE POISON

• Binds with first of the proteins of the ETC

• used to kill insects and fish pests

• Cyanide and carbon monoxide bind with third protein of ETC

• Antibiotic oligomycain blocks H+ ions through ATP synthase channel

• Used to combat fungal infections on the skin

Uncouplers

• Make the membrane of the mitochondrion

leaky to H+ ions

• So…can’t make ATP• DNP prescribed as weight-loss

pills, but banned

6.14 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

Where does it all come from?

•1 NADH = 3 ATP

•1 FADH2 = 2 ATP