BSCI 170 - Intro to Cellular Respiration & Fermentation, Aerobic Respiration, and Oxidative Phosphorylation

Oxidation of Cellular Fuel

• Each electron transfer reaction is __________

  • Electrons ____ energy with each transfer

  • Electrons in H2O have ____ (potential) energy than they did in glucose

• Released free energy drives ___ ________

exergonic, lose, less, ATP synthesis

Stepwise Energy Harvest

• Is energy from glucose released at once?

• How is glucose combusted?

• Electrons (and protons) are ________ ____ and _________ to another molecule (electron carrier).

• no

• in a series of small, enzyme-catalyzed steps

• stripped away, transferred

Nicotinamide Adenine Dinucleotide

• Derivative of Niacin

• Oxidized form, ____, serves as an important ________ ________ during cellular respiration

• What is the reduced form?

• NAD+, electron acceptor

• NADH

Cellular Respiration

• Respiration is the cumulative effect of 4 separate events. What are they?

• Glycolysis (lysis of glucose)

• Pyruvate Oxidation and Citric Acid Cycle (oxidation of carbon and salvaging of high-energy electrons)

• Electron Transport (stripping energy from the electrons)

• Oxidative Phosphorylation (using the energy from the electrons to synthesis ATP)

Without the process of cellular respiration, the addition of oxygen to H₂ would result in an _________ _______.

explosive release

Oxidation of Glucose

• C6H12O6 + 6O2 —> 6CO2 + 6H2O + Energy

• Oxidation of glucose means electrons (and protons) are removed from _______ and transferred to ______.

• The first step in this complex, multistep process is ________.

glucose, oxygen, glycolysis

Glycolysis

• Glycolysis means _____ _________

  • glyco = ________ __ _____ & lysis = __ ______

  • occurs in the _______ of __________

  • one six-carbon sugar (_______) is ________ to ___, _____-______ __________ (________)

sugar splitting, relating to sugar, to unbind, cytosol, eukaryotes, glucose, oxidized, two, three carbon molecules, pyruvate

Fermentation

There are many different fermentation pathways

• All have two common purposes. What are they?

• What is reduced in fermentation?

• Oxidize NADH to regenerate NAD+

• Allow glycolysis to continue

• Pyruvate (or a derivative of pyruvate) is reduced

Lactate Fermentation

• In fermentation, ________ is reduced and ____ is oxidized

  • Pyruvate + NADH + H⁺

pyruvate, NADH

What is pictured in this image?

lactate fermentation

Lactate Fermentation

• No release of ___

• No consumption of __

• No consumption of ___

• Occurs in vertebrate skeletal muscles during __________ _______

  • Lactate build-up contributes to the burning feeling of ______ _______

CO2, O2, ATP, anaerobic workout, active muscles

Lactate Fermentation in Food

• Use bacteria to perform desirable lactic acid (lactate) fermentation (undesirable = ________)

• Important for production of yogurt, pickles, sauerkraut, kimchi, sour cream, sourdough bread, kombucha, etc..

• Kombucha SCOBY (Symbiotic Culture of Bacteria and Yeast (kombucha = lactate and alcohol fermentation)

spoilage

Alcoholic Fermentation

• Pyruvate is converted into ____________ and ______ _______

• Acetaldehyde is _______ to ________

• Common process in microorganisms such as Brewer’s Yeast

acetaldehyde, carbon dioxide, reduced, ethanol

Alcoholic Fermentation with Yeast

• In alcohol fermentation, pyruvate is converted to ethanol in two steps

  • The first step _________ ___

  • The second step ________ _______

• Alcohol fermentation by yeast is used in brewing, winemaking, and baking

releases CO2, produces ethanol

Ethanol Toxicity

• Everyone knows that ethanol is toxic.

  • Too much of a good thing can have lots of negative consequences

    • Reason: Think _________ __________

reversible reactions

Ethanol Toxicity

• Too much ethanol leads to ___________ of _____

• Too much acetaldehyde is _____

  • metabolic breakdown leads to ________, etc.

dehydration, cells, toxic, headaches

Alcohol Toxicity

• Drinking bad moonshine can be highly dangerous because of production of methanol

• Methanol (CH3OH) is more toxic than _______ (CH3CH2OH)

  • Why?

ethanol, due to reversible reactions

Moonshine Toxicity

• Methanol and ethanol are substrates for the same enzyme: _______ ______________

  • Ethanol (2C alcohol) ←→ Acetaldehyde (2C aldehyde)

  • Methanol (1C alcohol) ←→ Methaldehyde (1C aldehyde)

alcohol dehydrogenase

Methanol Toxicity

• Another name for methaldehyde: ____________

• Formaldehyde = ________ _____

formaldehyde, embalmer’s fluid

Formaldehyde Toxicity

• Formaldehyde converts to ______ ____

• In humans, ______ ____ leads to __________ _________ at low concentrations

formic acid, formic acid, permanent blindness

Problem at the End of Glycolysis

• Glycolysis is ____ but is not an efficient use of the _________ ________.

• After glycolysis and fermentation, more than 90 percent of the energy is still trapped in ______ _______ __________.

  • ________

  • _______

  • ________

  • Etc.

fast, starting material, reduced organic molecules, pyruvate, lactate, ethanol

Aerobic Respiration

• So far no ______ has been used

• In the presence of ______, the _______ organics can be completely ________.

• This is Solution 2 for regenerating ____

oxygen, oxygen, reduced, oxidized, NAD+

After Glycolysis

• Most of the energy (90 percent) in glucose is still ________.

• In the absence of O2: ____________

  • allows regeneration of ____

  • allows __________ to continue

untapped, fermentation, NAD+, glycolysis

In the Presence of Oxygen

• Another fate: ________ __________

  • occurs in the ______ __ ___ ____________

complete oxidation, matrix of the mitochondria

Step 1: Getting Pyruvate into the Mitochondrial Matrix

• Pyruvate must pass through both the outer and inner ______________ _________ to get into the ______

• Pyruvate moves passively across the outer membrane via _____ (membrane protein)

• Pyruvate is actively transported across the inner membrane into the matrix via a ___-________ _____________

mitochondrial membranes, matrix, porin, H+ pyruvate cotransporter

Once in the Matrix, Pyruvate is Decarboxylated

For your reference

N/A

Acetyl-CoA is an important coenzyme in ____________ and _____ ____ ___________

carbohydrate, fatty acid metabolism

Acetyl-CoA

• Acetyl-CoA is a ________ in the ______ ____ _____

• We tend to think of metabolic pathways as being linear, but a cycle occurs when the product of the final reaction is also a _________ in the first reaction

reactant, citric acid cycle, reactant

Biochemical Cycles

• There is no ________ point or ______ point to a metabolic cycle

• Intermediates can enter the cycle at any point.

starting, ending

Citric Acid Cycle

• Biochemical cycles often named for the first ____________ product

  • Citric acid (or citrate)

    • 6-Carbon organic acid

    • 3 Carboxyl groups (COOH)

recognizable

Citric Acid Cycle

• Also known as the Tricarboxylic Acid (TCA) Cycle, the Citrate Cycle, and the Krebs Cycle (after Hans Krebs)

  • For your reference

N/A

Is pyruvate decarboxylation a part of the citric acid cycle?

no

Summary of the Citric Acid Cycle

N/A

Summary of the Citric Acid Cycle

• During the next 7 reactions there are:

  • 2 _____________ (removal of 2 ___)

  • 4 _________ (along with 4 ________)

    • 3 ____ —> 3 ____ + 3 __ (6 ________)

    • 1 ___ —> 1 _____ (2 ________)

  • 1 _________-______ _______________ (___)

• All to regenerate the starting material: ____________ (__)

• Remember: ___________ produces 2 _________ for each molecule of ________.

  • Oxidizing both pyruvates from glycolysis requires progression through __________ _________ and the _____ ____ _____ ___ _______

decarboxylations, CO2, oxidations, reducations, NAD+, NADH, H+, electrons, FAD, FADH, electrons, substrate-level phosphorylation, ATP, oxaloacetate, 4C, glycolysis, pyruvates, glucose, pyruvate oxidation, citric acid cycle, 2 times

Coenzyme and CO2 Accounting in the Matrix

• For each entering glucose molecule:

  • __ carbons generating __ pyruvates

• __ pyruvate oxidations (w/ decarboxylation)

  • __ CO2

  • __ NADH

• __ turns through the ______ ____ _____

  • __ CO2

  • __ NADH

  • __ FADH2

6, 2, 2, 2, 2, 2, citric acid cycle, 4, 6, 2

What has been achieved by the end of the citric acid cycle?

• All __ carbons in glucose have been fully _________ to ___

• __ ATPs generated by _________-_____ _______________

  • __ from __________

  • __ from ___ turns of the ______ ____ _____

• >90% of remaining energy is in the form of “high-energy” electrons stored in ________ __________

  • ____ & _____

6, oxidized, CO2, 4, substrate-level phosphorylation, 2, glycolysis, 2, 2, citric acid cycle, reduced coenzymes, NADH, FADH2

Electron Transport

• High-energy electrons are removed from the _______ __________

• Their energy is slowly extracted through a stepwise series of _________ ___________ and __________ ______.

  • electron transport chain (ETC)

reduced coenzymes, exergonic oxidation, reduction steps

Respiratory Complexes

• __ large multiprotein complexes embedded in the ____ ____________ ________ comprise the ___

  • Respiratory complexes I-IV

  • Also __ small, mobile ________ _________

    • Coenzyme Q and Cytochrome C ____ _________ between complexes

4, inner mitochondrial membrane, ETC, 2, electron carriers, move electrons

Electron Transfer

• Each electron transfer represents an __________-__________ reaction

• Each electron transfer is _________

  • Each successive carrier binds electrons with a ______ affinity than the previous one

    • each successive carrier is more ___________ than the previous one

  • Electrons ____ energy as they move away from ____ or _____.

oxidation reduction, exergonic, higher, electronegative, lose, NADH, FADH2

Oxidation of NADH and FADH2

For your reference

N/A

What is coenzyme Q (CoQ)?

• a lipid-soluble, mobile electron carrier

• CoQ accepts electrons from Complex I & Complex II and delivers them to Complex III

  • Also used as a nutritional supplement

Reduction of Oxygen

• The reduction of O2 to ___ in the final step of electron transport is the entire reason we need to breathe oxygen to survive

H2O

Accounting Time: End of ETC

• All of the carbons in glucose have been oxidized to ___

  • By the end of ______ ____ _____

• All of the electrons have been _______ to the energy level of _____

CO2, citric acid cycle, reduced, water

Coupling of ATP Synthesis and the ETC

• By the 1960s, the basic functions of mitochondria were well established. What are they?

• What was not known about the functions of mitochondria?

• primary oxidation center of eukaryotic cells

• oxidation of carbohydrates and fatty acids

• electron transport chain (ETC)

• ATP synthesis

• What wasn’t known: How these were connected

ATP Synthase Complex

• Another large, multiprotein complex embedded in the _____ _________ ________

inner mitochondrial membrane

Coupling Factor F₀F₁

• What is F₀?

• What is F₁?

• H+ channel

• ATPase

ATP Synthase Complex

• Functions like an active H⁺ transport protein __ _______

in reverse

Active Transport Refresher

• ATP is hydrolyzed to ___ and __, and ____ ______ used to pump ___ from [___] to [____]

• Remember that reactions are ___________.

ADP, P_i, free energy, H+, low, high, reversible

Reversal of this Transport

• H+ moving across membrane from [____] to [___], release free energy that can be used to drive ___ _________

high, low, ATP synthesis

Where does the H+ gradient come from?

• Some respiratory complexes can actively transport H+ across the inner membrane.

  • Use free energy released by transported electrons

  • Complexes I, III, and IV transport H+

  • No evidence that Complex II transports H+

• Directional H+ transport, together with an impermeable inner membrane, means a substantial gradient can form

• Remember that cells store energy in gradients

• A H+ gradient is an electrochemical gradient

  • The total amount of stored energy results from the combined concentration and electrical differences across the membrane

• _______ is a passive movement of water across a membrane

• ____________ is passive movement of ions (H+ in this case) across a membrane

• More specifically, chemiosmosis refers to the process of ATP synthesis driven by the movement of ___ across a _________

osmosis, chemiosmosis, H+, membrane

The Chemiosmotic Model for ATP Synthesis

• Exergonic transfer of electrons through the _____ ________drives active H+ transport across the ______ _________ and ___ __ ________

• When the H+ cross the membrane back into the matrix, ____ ______ is released by spinning ___ ________

• The energy is used to synthesize ___ from ___ and __

inner membrane, inner membrane, out of matrix, free energy, ATP synthase, ATP, ADP, P_i

Putting It Together

For your reference

N/A

Oxidative Phosphorylation

• The phosphorylation of ___ during _______ __________ is associated with the ______-__________ transport of electrons in the ____________.

• This is called __________ ______________ to distinguish it from substrate-level phosphorylation

ADP, aerobic metabolism, oxygen dependent, mitochondria, oxidative phosphorylation

How much energy do the electrons have?

• How much energy do electrons in NADH have?

• How much energy do electrons in FADH2 have?

**Remember that Complex II does not transport __

• enough energy to make between 2 and 3 ATPs

• enough energy to make between 1 and 2 ATPs

• H+

Final Cost Accounting

How many ATP produced after each step?

• 2

• 5

• 5

• 2

• 15

• 3

• Total: 32

For your reference

N/A

The Versatility of Cellular Respiration

• Catabolic pathways funnel electrons from many kinds of _______ ________ into cellular respiration

• Glycolysis accepts a wide range of ___________

• ________ must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle

organic molecules, carbohydrates, proteins

The Versatility of Cellular Respiration

• Fats are digested to ________ (used in glycolysis) and fatty acids (used in generating _____ ___)

• Fatty acids are broken down by ___ _________ and yield _____ ___

• An oxidized gram of fat produces more than ______ as much ___ as an oxidized gram of ___________

glycerol, acetyl CoA, beta oxidation, acetyl CoA, twice, ATP, carbohydrate

For your reference

N/A

Regulation of Cellular Respiration via Feedback Mechanisms

• ______ _________ is the most common mechanism for metabolic control

• If ATP concentration begins to drop, respiration ______ __; when there is plenty of ___, respiration _____ _______

• Control of catabolism is based mainly on __________ ___ ________ __ _________ at strategic points in the catabolic pathway

feedback inhibition, speeds up, ATP, slows down, regulating the activity of enzymes