Chapter 9 - Cellular Respiration and Fermentation

How does photosynthesis make organic molecules and O2?

How does photosynthesis make organic molecules and O2?

By using CO2 and H2O

How does cellular respiration create ATP?

By using O2 and organic molecules

Catabolic Pathways

Release stored energy by breaking down complex molecules, which is essential to cellular respiration.

Fermentation

A partial degradation of sugars that occurs without oxygen.

Oxidizes NADH by transferring electrons to pyruvate; is a type of glycolysis.

Aerobic Respiration

Respiration that requires oxygen - consumes organic molecules and yields ATP.

Anaerobic Respiration

Respiration that does not require oxygen - consumes compounds other than oxygen - produces lactic acid (fermentation)

Cellular Respiration

The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen includes aerobic and anaerobic respiration.

Taking electrons from food and giving them to oxygen to make water, using the energy released to drive ATP formation.

Redox Reactions (Oxidation-Reductions)

When there is a transfer of one or more electrons from one reactant to another.

Reducing Agent

The electron donor, it reduces the electron acceptor.

Oxidizing Agent

Electron acceptor, it oxidizes the electron donor.

Dehydrogenases

Enzymes that remove a pair of hydrogen atoms (2 electrons and 2 protons) from the substrate.

How is NAD+ formed to make NADH?

The 2 electrons and 1 proton from dehydrogenases creates NADH, while the other proton is released as a hydrogen ion (H+) into the surroundings.

Electron Transport Chain

Consists of a series of molecules built into the inner membrane of the mitochondria (or plasma membrane of prokaryotes)

Glycolysis

The breakdown of glucose by enzymes, releasing energy and pyruvic acid.

Citric Acid Cycle (Krebs Cycle)

- 2 Pyruvates enter the mitochondrion

- releases 2 ATP, 6NADH, and 2 FADH2 for each glucose

The breakdown of glucose to O2

oxidative phosphorylation

The production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration.

Chemiosmosis

A process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme.

Creates almost 90% of ATP, powered by redox reactions.

substrate-level phosphorylation

The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.

Creates some ATP formed by glycolysis and the citric acid cycle.

For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to _____ molecules of ATP

32 molecules of ATP

Where does glycolysis occur?

In the cytosol of the cell

How many stages does glycolysis have? What are they?

2 major stages

Energy Investment Stage, and Energy Payoff Stage

Energy Investment Stage

2 ATP are used to split glucose into 2 three-carbon sugar molecules

Energy Payoff Stage

4 ATP synthesized, 2 NAD+ reduced to NADH, and small sugars are oxidized to form 2 pyruvate and 2 H2O.

How much ATP is produced by substrate-level phosphorylation?

2 ATP

Glycolysis releases CO2: T or F?

False, glycolysis does not release any CO2, and occurs whether or not O2 is present.

What is pyruvate converted to before entering the krebs cycle?

Pyruvate is converted to acetyl coenzyme A (acetyl CoA)

What three reactions does pyruvate catalyze?

Oxidation of pyruvates group, releasing the first CO2 of cellular respiration.

Reduction of NAD+ to NADH

Combination of the remaining two-carbon fragment with co-enzyme A to form Acetyl CoA.

When the Citric Acid Cycle oxidizes organic fuel derived from pyruvate, what is generated per turn?

1 ATP

3 NADH

1 FADH2

What are pyruvates?

3 carbon molecules

The end product of glycolysis

How many steps does the Citric Acid Cycle have?

8 steps, each catalyzed by a specific enzyme

What is the first step of the krebs cycle?

The acetyl group of acetyl co-enzyme A joins the cycle by combining with oxaloacetate, forming citrate.

What are the last 7 steps of the krebs cycle?

Decomposing the citrate back to oxaloacetate, making the process a full cycle.

How does NADH and FADH2 powers ATP synthesis in eukaryotic cells?

By donating electrons to the electron transport chain

Where are molecules of the electron transport chain found?

Embedded in the inner mitochondrial membrane in eukaryotic cells.

What are cytochromes?

Proteins with heme groups containing an iron atom

ATP synthase

enzyme that catalyzes the reaction that adds a high-energy phosphate group to ADP to form ATP

Proton-Motive Force

The potential energy stored in the form of an electrochemical gradient, generated by the pumping of hydrogen ions across biological membranes during chemiosmosis.

What is the flow of energy in cellular respiration?

Glucose --> NADH --> Electron Transport Chain --> Proton-Motive Force --> ATP

How much energy in a glucose molecule is transferred to ATP?

34%, making 32 ATP -- rest of the energy is lost as heat

What are the three reasons as to why the exact number of ATP produced in cellular respiration is not known?

1). Photophosphorylation and the redox reactions are not directly coupled; ratio of NADH to ATP molecules is not a whole number.

2). ATP yield varies depending on whether electrons are passed to NAD+ or FAD.

3). The proton-motive force is also used to drive other kinds of work.

Alcohol Fermentation

Pyruvate is converted to ethanol in 2 steps;

- CO2 is released from pyruvate

- NAD+ and ethanol is produced

Used in brewing, winemaking, and baking (yeast)

Lactic Acid Fermentation

Pyruvate is reduced directly by NADH to form lactate and NAD+.

No release of CO2, used to make cheese and yougurt (fungi and bacteria)

What is the major difference between fermentation and anaerobic/aerobic respiration?

The mechanisms used to oxidize NADH to NAD+

- Fermentation: pyruvate acts as final electron acceptor

- Cellular Respiration: electrons transfer to the electron transport chain

Obligate Anaerobes

Carry out fermentation or anaerobic respiration, and cannot survive in the presence of O2

Facultative Anaerobes

Yeast and bacteria; can survive using either fermentation or cellular respiration.

What are 2 major intersections to various catabolic and anabolic pathways?

Glycolysis and the Citric Acid Cycle

Anabolic pathways

Metabolic pathways that consume energy to build complicated molecules from simpler ones.

Deamination

the removal of an amino group from an amino acid

The process of proteins being digested into amino acids.

What are fats digested to in catabolism?

Glycerol

Glycerol

Combines with fatty acids to make lipids; used to produce compounds needed for glycolysis

Catabolism

Metabolic pathways that break down molecules, releasing energy.

BREAKING DOWN

Anabolism

Metabolic pathways that construct molecules, requiring energy.

BUILDING UP

Beta Oxidation

A metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA.

Biosynthesis

The process by which living organisms produce larger molecules from smaller ones.

feedback mechanism

The most common mechanism for metabolic control, because it prevents wasteful production.

How is catabolism controlled?

Regulating activity of enzymes at strategic points in the pathway.

How does the Citric Acid Cycle make ATP?

via substrate-level phosphorylation

What do cells require to sustain high rates of glycolysis under anaerobic conditions?

NAD+

What will happen to ATP synthesis and oxygen consumption of the rates of glycolysis and the citric acid cycle stay the same?

ATP synthesis will decrease

Oxygen consumption will stay roughly the same

The hydrogens taken from glucose or a breakdown product of glucose are added to oxygen, releasing energy to:

actively transport hydrogen ions (H+) into the intermembrane space

ATP synthase at the inner mitochondrial membrane makes ATP and water from ADP and phosphate by coupling this to which other process?

Allowing hydrogen ions to move down its electrochemical gradient

Newborn mammals have a specialized tissue called brown fat, where cells burn fat to CO2 without capturing the energy to reduce electron carriers or drive ATP formation. How might this energy be used instead?

To create heat

What is the purpose of fermentation reactions?

To regenerate NAD+ so that glycolysis can continue

During intense exercise, muscles lack sufficient oxygen, so which process will these muscles mainly use?

- Alcoholic Fermentation

- Citric Acid Cycle

- Lactic Acid Fermentation

- Chemiosmosis

Lactic Acid Fermentation

Compared to the carbons in glyceraldehyde 3-phosphate, the carbons in 1,3-biphosphoglycerate have _________, so these carbons are more _________.

Fewer bonds with hydrogen and more bonds with oxygen; oxidized.

The production of ethanol by fermentation pairs with location?

- Cytosol of the cell

- Mitochondria

Cytosol of the cell

Which of the following is not an immediate net product of the typical mitochondrial electron transport chain?

- Water

- ATP

- NAD+

- FAD

- proton electrochemical gradient

ATP

Through beta oxidation, fats are converted to acetyl CoAs --- the further respiration of these acetyl CoAs typically bypasses which parts of normal aerobic respiration?

Glycolysis and pyruvate oxidation

You removed the inner membrane of the mitochondrion, could the cell produce any ATP from glucose?

- Yes, by glycolysis and fermentation

- Yes, by the citric acid cycle

- Yes, using ATP synthase

- Yes, by electron transport

Yes, by glycolysis and fermentation

You are handed a biochemical extract from cells that were performing cellular respiration. You detect cytochromes in one fraction, so it was probably used for the study of;

- glycolysis

- fermentation

- atp synthase

- electron transport

- beta-oxidation

Electron transport

Your cells were in need of ATP, what could help you?

- substrate-level phosphorylation

- ATP synthase

- Glycolysis

- Fermentation

- All of the above

All of the above

Shape changes are important in the working of enzymes and other parts of biochemistry. In ATP production, what changes shape?

- Stator

- Protons

- Rotor

- ADP

- Membrane lipids

Rotor

Why does glucose and oxygen have more free energy than carbon dioxide and water?

Because glucose and oxygen have not yet reacted

What is free energy?

the amount of energy that is free to do work after a chemical reaction.

How are photosynthesis and cellular respiration connected?

The first produces glucose, full of energy, and the second extracts that energy.