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LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

Lectures by Erin Barley Kathleen Fitzpatrick

Cellular Respiration and Fermentation

Chapter 9

Life Is Work

Living cells require energy from outside sources; require transformations of energy

Animals or Consumers (chimpanzee) obtain energy by eating plants or other organisms that eat plants or other animals (or puffins (sea birds) obtain energy from eels and other aquatic organisms that obtain their energy from photosynthetic organisms)

Plants or Producers obtain energy from sunlight producing food (sugars) for themselves and Consumers

As mentioned earlier chapters –

Animals or Consumers (chimpanzee) are heterotrophs that obtain energy by eating plants or other organisms that eat plants or other animals (ex. puffins (sea birds) obtain energy from consuming eels and other aquatic organisms which obtain their energy from photosynthetic organisms (algae))

Plants or Producers are autotrophs that obtain energy from sunlight producing food (sugars) for themselves and Consumers.

Light
energy

ECOSYSTEM

Photosynthesis
in chloroplasts

Cellular respiration
in mitochondria

CO2  H2O

ATP powers
most cellular work

ATP

Heat
energy

 O2

Organic
molecules

Energy flow and chemical recycling in ecosystems.

Light energy is absorbed by chloroplasts for photosynthesis (releases organic molecules (sugars) and oxygen) – these molecules are used in cellular respiration (aerobic respiration which occurs in the mitochondria) to produce ATP for cellular work – (which produces carbon dioxide and water) – needed for photosynthesis – and the cycle continues photosynthesis – respiration – photosynthesis, etc.

Cellular Respiration

Several processes are central to Cellular Respiration and related pathways
Breakdown of organic molecules is a Catabolic Pathway and is Exergonic

Fermentation:
Partial degradation of sugars that occurs without the use of oxygen but survives in oxygen
Does not require oxygen and can occur in an aerobic or anaerobic environment; oxygen will not kill it
Final acceptor of electrons is an organic molecular

Aerobic Respiration:
Consumes organic molecules and oxygen and yields ATP
Requires oxygen
Final acceptor of electrons will be oxygen

Anaerobic Respiration:
Requires an anaerobic environment – oxygen can (WILL) kill the organism
Final acceptor is an inorganic compound other than O2
Similar to Aerobic Respiration but consumes compounds other than O2

Ultimate Goal of Cellular Respiration Is ATP Formation.

Ultimate Goal of Cellular Respiration Is ATP Formation.

Cellular Respiration is the Breakdown of organic molecules (glucose is the major molecule), is a Catabolic Pathway and is Exergonic (releases energy)

Fermentation:

Partial degradation of sugars that occurs without the use of oxygen but can survive in oxygen

Does not require oxygen and can occur in an aerobic or anaerobic environment; oxygen will not kill it

Aerobic Respiration (major form of respiration):

Consumes organic molecules and oxygen and yields ATP

Requires oxygen (areobic respiration)

Lack of oxygen will kill the organism

Anaerobic Respiration:

Requires an anaerobic environment – oxygen can (WILL) kill the organism

Cellular Respiration

Cellular Respiration:
Includes Aerobic, Anaerobic Respiration and/or Fermentation
Often used to refer to Aerobic Respiration (requires a mitochondria (Eukaryotic cells)
Although carbohydrates, fats, and proteins are all consumed as fuel, Aerobic Respiration begins with the sugar Glucose

C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy (ATP + heat)

Aerobic Respiration, Fermentation and Anaerobic Respiration:
All begin with Glycolysis, which converts one molecule of glucose into two molecules of Pyruvate

Fermentation and Anaerobic Respiration:
Completed in the cytoplasm, yielding 2 ATP per glucose molecule
Aerobic Respiration:
Completed in mitochondria, yielding 30-36 ATP per glucose molecule

Cellular Respiration:

Includes Aerobic Respiration, Anaerobic Respiration and/or Fermentation

Often used to refer to Aerobic Respiration (requires a mitochondria (found only in Eukaryotic cells)

Although carbohydrates, fats, and proteins are all consumed as fuel, Aerobic Respiration begins with the sugar Glucose

C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy (ATP + heat)

Aerobic Respiration, Fermentation and Anaerobic Respiration (Fully discussed in following slides):

All begin with Glycolysis, which converts one molecule of glucose into two molecules of Pyruvate

Fermentation and Anaerobic Respiration:

Completed in the cytoplasm, yielding 2 ATP per glucose molecule

Aerobic Respiration:

Completed in mitochondria, yielding 30-36 ATP per glucose molecule

Comparison of the Main Respiratory Pathways

FYI - Playing football needs aerobic respiration for making energy; muscles may use fermentation for energy which also producing lactic acid (muscles ache); birds have specialized red muscles and respiration for migration; plants also undergo respiration for energy (produce own sugars).

Panel on right – carbs entering glycolysis can enter the anaerobic or fermentation pathway (left) or in eukaryotic cells the mitochondria (aerobic respiration (right).

Combustion versus Aerobic Respiration

Explosions! Not good for the cell. Aerobic Respiration in principle is similar to Combustion; energy is released; 686 kcal/mol; same energy whether it be the burning of wood or broken down by the cell.

Glucose and oxygen react in flame to produce crème bulee, energy is released at once; glucose broken down in respiration produces a controlled reaction, no flames and lots of ATP to run cell.

Aerobic Respiration

Harvesting of Energy from Glucose has 3 Stages:

Glycolysis:
Occurs in the Cytoplasm
Breaks down Glucose into two molecules of Pyruvate
Produces ATP by Substrate Level Phosphorylation

Citric Acid Cycle or Krebs Cycle:
Occurs in the Mitochondria Matrix or Inner Compartment
Completes the breakdown of glucose; releases Carbon Dioxide
Produces ATP by Substrate Level Phosphorylation

Oxidative Phosphorylation:
Occurs on the Inner Mitochondria Membrane
Oxygen is required – final electron acceptor for the Electron Transport Chain
Accounts for most of the ATP synthesis by Oxidative Phosphorylation

Harvesting of Energy from Glucose in Aerobic Respiration has 3 Stages (which will be discussed fully) (great introductory slide):

Glycolysis:

Occurs in the Cytoplasm

Produces ATP by Substrate Level Phosphorylation

Citric Acid Cycle or Krebs Cycle:

Occurs in the Mitochondria Matrix or Inner Compartment

Completes the breakdown of glucose; releases Carbon Dioxide

Produces ATP by Substrate Level Phosphorylation

Oxidative Phosphorylation:

Occurs on the Inner Mitochondria Membrane

Oxygen is required for the Electron Transport Chain

Accounts for most of the ATP synthesis in Aerobic Respiration

Figure 9.6-3

Electrons
carried
via NADH

Electrons carried
via NADH and
FADH2

Citric
acid
cycle

Pyruvate
oxidation

Acetyl CoA

Glycolysis

Glucose

Pyruvate

Oxidative
phosphorylation:
electron transport
and
chemiosmosis

CYTOSOL

MITOCHONDRION

ATP

Substrate-level
phosphorylation

Oxidative
phosphorylation

Highlights of Aerobic Respiration – good review slide (fully discuss later in this chapter)

Formation of ATP (Ultimate Goal) by the Cell

Oxidative Phosphorylation:
Electron Transport Chain – Final Step in Aerobic Respiration
Process that generates most of the ATP
Electrons are then donated to Oxygen – final electron acceptor
Accounts for almost 90% of the ATP generated by Aerobic Respiration

Substrate-Level Phosphorylation:
Smaller amounts of ATP are formed in Glycolysis and the Citric Acid Cycle
ATP is formed directly by transferring a phosphate group (Enzymatically) directly to ADP from a phosphate bearing intermediate or substrate
Only ATP produced in Anaerobic Respiration and Fermentation

For each molecule of Glucose degraded to CO2 and Water by Cellular Respiration, the cell makes up to 32 (36) molecules of ATP

Formation of ATP (Ultimate Goal) in cells:

Oxidative Phosphorylation:

Electron Transport Chain – Final Step in Aerobic Respiration (need mitochondria only in eukaryotic cells)

Process that generates most of the ATP

Requires oxygen

Accounts for almost 90% of the ATP generated by Aerobic Respiration

Substrate-Level Phosphorylation:

Smaller amounts of ATP are formed in Glycolysis and the Citric Acid Cycle

ATP is formed directly by transferring a phosphate group (Enzymatically) directly to ADP from a phosphate bearing intermediate or substrate which contains a phosphate (next slide)

Only ATP produced in Anaerobic Respiration and Fermentation

Figure 9.7

Substrate

Product

ADP

ATP

Enzyme

Substrate-level phosphorylation – enzymatic – phosphate attached to a substrate is transferred to ADP forming ATP – method for formation is responsible for the only ATP formed in Glycolysis and Citric Acid Cycle

Please Don’t Get Nervous

We are doing an overview only of the different respiration pathways – you will need to know cellular location, what compound enters, leaves (exits) , amount of ATP produced, which method of production (substrate level or oxidative).

Glycolysis – Overview

Glycolysis or “Splitting of Sugar”:
Breaks down Glucose (Enters the Pathway) into 2 molecules of Pyruvate (product)
Forms 2 net ATP for each glucose molecule that enters
Produces 2 molecules of NADH
Occurs in the Cytoplasm
Occurs whether or not O2 is present (doesn’t require Oxygen)

Two Major Phases:
Energy Investment Phase:
1st 5 steps converts glucose into glyceraldehyde 3-phosphate (G3P)
Requires 2 ATP
Endergonic Reaction

Energy Payoff Phase:
ATP is synthesized by Substrate-Level Phosphorylation produces 2 ATP molecules per G3P molecule or 4 total ATP
NADH is formed by electron transfer

Glycolysis has 2 major phases –

1.) Energy investment or Requiring Phase – 2 ATP are needed to start the pathway

2.) Energy Payoff or Synthesizing Phase – 4 ATP’s are formed by substrate level phosphorylation

Glycolysis – occurs in the cytoplasm

glucose enters the pathway

pyruvate is the product

forms 2 net (total) ATP by substrate level phsphorylation

doesn’t require oxygen

All organisms (prokaryotes, eukaryotes) use glycolysis as respiratory pathway.

Figure 9.9-4

Glycolysis: Energy Investment Phase

ATP

Glucose

Glucose 6-phosphate

Fructose 6-phosphate

Fructose 1,6-bisphosphate

Dihydroxyacetone
phosphate

Glyceraldehyde
3-phosphate

To
step 6

ADP

Hexokinase

Phosphogluco-
isomerase

Phospho-
fructokinase

Aldolase

Isomerase

A closer look at glycolysis. Not responsible for pathway.

Energy Investment or Requiring Pathway - Know - Requires 2 ATP. Know - Enzyme phosphofructokinase – (later we will learn that it is a major control point in respiration – discussed later)

Figure 9.9-9

Glycolysis: Energy Payoff Phase

2 ATP

2 NADH

2 NAD

+ 2 H

2 P i

2 ADP

1,3-Bisphospho-
glycerate

3-Phospho-
glycerate

2-Phospho-
glycerate

Phosphoenol-
pyruvate (PEP)

Pyruvate

2 ADP

2 H2O

Phospho-
glycerokinase

Phospho-
glyceromutase

Enolase

Pyruvate
kinase

Triose
phosphate
dehydrogenase

A closer look at glycolysis. Not responsible for pathway.

Energy payoff or releasing phase - Know - form 4 molecules of ATP by substrate level phosphorylation.

Figure 9.8

Energy Investment Phase

Glucose

2 ADP  2 P

4 ADP  4 P

Energy Payoff Phase

2 NAD+  4 e  4 H+

2 Pyruvate  2 H2O

2 ATP used

4 ATP formed

2 NADH  2 H+

Net

Glucose

2 Pyruvate  2 H2O

2 ATP

2 NADH  2 H+

2 NAD+  4 e  4 H+

4 ATP formed  2 ATP used

Calculation – How many ATPs are formed in glycolysis:

2 ATPs are needed to start the pathway (Energy Investment Phase)

4 ATPs are formed by substrate level phosphorylation (Energy Payoff Phase)

Total - 2 ATPs total (4-2=2 ATP total or net).

Do not worry about NADH (discussed later)

Mitochondria

Aerobic respiration occurs in the mitochondria. Requires eukaryotic cell. Aerobic respiration does not occur in prokaryotic cells.

Pyruvate Oxidation

In the presence of O2, Pyruvate enters the Mitochondria Matrix (Inner Compartment) in eukaryotic cells where the oxidation of Glucose is completed in the Citric Acid or Krebs Cycle

Pyruvate Oxidation:
Occurs before the Citric Acid Cycle and links Glycolysis with the Citric Acid Cycle
Pyruvate (enters) is converted to Acetyl Coenzyme A (Acetyl CoA)(product)
Releases CO2; forms 2 NADH

Pyruvate is the product from glycolysis (cytoplasm). Pyuvate enters the mitochondria matrix or inner compartment.

Pyruvate enters the mitochondria and is converted to Acetyl CoA with release of carbon dioxide. NADH will be discussed later.

Figure 9.10

Pyruvate

Transport protein

CYTOSOL

MITOCHONDRION

CO2

Coenzyme A

NAD

+ H

NADH

Acetyl CoA

Oxidation of pyruvate to acetyl CoA, is the step before the citric acid cycle known as Pyruvate Oxidation.

Starts in the cytoplasm and then enters the mitochondria matrix (inner compartment). Pyruvate enters and is converted to Acetyl CoA with release of carbon dioxide.

Citric Acid Cycle or Krebs Cycle

Citric Acid Cycle or Krebs Cycle (occurs in the Mitochondria Matrix or Inner Compartment):
Completes the break down of Pyruvate to CO2
Total = 1 molecule of Glucose yields 2 ATP, 6 NADH, and 2 FADH2
ATP is formed by Substrate-Level Phosphorylation

8 steps, each catalyzed by a specific enzyme
Acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate
Next seven steps decompose the citrate back to oxaloacetate, making the process a cycle
NADH and FADH2 that are produced send their electrons to the Electron Transport Chain

The Glucose that enters aerobic respiration through glycolysis is totally converted to Carbon dioxide in the Citric Acid Cycle. All carbon dioxide formed in respiration comes from pyruvate oxidation and the Citric Acid Cycle (also known as the Krebs Cycle).

Acetyl Co-A enters; carbon dioxide is the product.

Occurs in the mitochondria matrix or inner compartment.

Yields 2 ATP by substrate levels phosphorylation. NADH and FADH will be discussed later.

Figure 9.11

Pyruvate

NAD

NADH

+ H

Acetyl CoA

CO2

CoA

2 CO2

ADP + P i

FADH2

FAD

ATP

3 NADH

3 NAD

Citric
acid
cycle

+ 3 H

An overview of pyruvate oxidation and the citric acid cycle. Do not need to know actually pathway – just components mentioned in test review (handout).

Electron Transport Chain

Following Glycolysis and the Citric Acid Cycle:
NADH and FADH2 account for most of the energy extracted from food
NADH and FADH2 donate electrons to the Electron Transport Chain, which powers ATP synthesis via Oxidative Phosphorylation

Electron Transport Chain:
Inner Membrane (Cristae) of the Mitochondria
Most of the chain’s components are proteins (carriers accept then donate electrons)
Electrons lose their energy as they go down the chain and are passed to O2, forming H2O

Electrons are transferred from NADH or FADH2 to the Electron Transport Chain and are passed through a number of proteins to O2, the final electron acceptor, producing ATP
Electron Transport Chain generates no ATP directly
Electron transfer causes proteins to pump H+ from the matrix to the intermembrane space
ATP Synthase uses the flow of H+ to produce ATP by Oxidative Phosporylation

Electron Chain

Occurs on the Inner Membrane of mitochondria

NADH and FADH enter

Requires oxygen

Produces ATP by oxidative phosphorylation (electron transport chain).

Figure 9.15

Protein
complex
of electron
carriers

(carrying electrons
from food)

Electron transport chain

Oxidative phosphorylation

Chemiosmosis

ATP
synth-
ase

III

Cyt c

FAD

FADH2

NADH

ADP  P i

NAD

H

2 H + 1/2O2

H

H2O

ATP

Diagram of electron transport chain to ATP synthesis. Do not need to know pathway except major components we have gone over.

Summary of ATP Formed

How much ATP does a cell gain from 1 molecule of glucose?

2 ATP Glycolysis 2 NADH

Pyruvate oxidation 2 NADH

2 ATP Krebs 6 NADH 2 FADH2

30 ATP 10 NADH

4 ATP 2 FADH2

34 ATP Electron Transport

Total 38 ATP (34 Electron Transport; 4 Substrate Level Phosporylation)

Only 36 ATPs are formed in eukaryotic cells as the NADH formed in the cytoplasm during Glycolysis must be actively transported in requiring 1 ATP for each NADH (Total 2 ATP)

Yield is actually lower as the membrane is “leaky” to protons allowing some to cross without forming ATP and the actually proton gradient may be used for other purposes such as transporting pyruvate – Actual Yield is 30 – 32 ATPs per molecule of glucose

High yield of energy is one of the factors that allowed eukaryotic cells to evolve as they could produce more energy.

How much ATP produced? Electron transport 36 theoritical (actual yield 30-32). High energy from aerobic respiration allowed eukaryotic cells to grow into multi-celled organisms.

Figure 9.16

Electron shuttles
span membrane

MITOCHONDRION

2 NADH

6 NADH

2 FADH2

 2 ATP

 about 26 or 28 ATP

Glycolysis

Glucose

2 Pyruvate

Pyruvate oxidation

2 Acetyl CoA

Citric
acid
cycle

Oxidative
phosphorylation:
electron transport
and
chemiosmosis

CYTOSOL

Maximum per glucose:

About
30 or 32 ATP

Good review slide. Know the info on cellular location of pathway (what enters, leaves), how many ATP produced. How is the ATP produced. Don’t worry about NADP and FAD.

Regulation of Cellular Metabolism

When cells have plentiful amounts of energy, key reactions of Glycolysis and Citric Acid Cycle slowed by ATP; when levels are low, AMP activate key enzymes.

Phosphofructose Kinase:
Converts fructose phosphate to fructose bisphosphate
Not readily reversible and committing step in Glycolysis – major regulatory enzyme
ATP, AMP or Citrate are Allosteric Activators or Inhibitors

Pyruvate Dehydragenase:
Oxidation of pyruvate to Acetyl C-A: committing step to the Citric Acid Cycle
Inhibited by citrate and ATP

Citrate Synthetase:
Converts oxalacetate and acetyl-CoA to citrate
Inhibited by ATP

The enzyme phosphofructose kinase:

Major or committing step in glycolysis.

Major regulatory enzyme in Cellular respiration.

Pyruvate Dehydragenase:

Committing step to the Citric Acid Cycle

Citrate Synthetase:

Also in the Critic Acid Cycle

Know the enzyme only; not the reaction.

Figure 9.20

Phosphofructokinase

Glucose

Glycolysis

AMP

Stimulates





Fructose 6-phosphate

Fructose 1,6-bisphosphate

Pyruvate

Inhibits

ATP

Citrate

Citric
acid
cycle

Oxidative
phosphorylation

Acetyl CoA

The control of cellular respiration (see previous slide). Know the info previously mentioned.

Fermentation and Anaerobic Respiration

Most Cellular Respiration requires O2 to produce ATP; Glycolysis couples with Fermentation or Anaerobic Respiration to produce ATP without O2

Anaerobic Respiration: oxygen can kill the organism uses a final electron acceptor other than O2 (Sulfur bacteria use sulfate)

Fermentation:
Uses Substrate-Level Phosphorylation to generate ATP – 2 net ATP
Occurs in the cytoplasm
Consists of Glycolysis plus reactions that regenerate NAD+

Alcohol Fermentation:
Pyruvate is converted to Ethanol in two steps, with the first releasing CO2
Used in brewing, winemaking, and baking

Lactic Acid Fermentation:
Pyruvate is reduced to NADH, forming Lactate with no release of CO2
Used by some fungi and bacteria make cheese and yogurt
Muscle cells use this generate ATP when O2 is scarce (lactic acid is why muscles ache)

Know

Glycolysis couples with Fermentation or Anaerobic Respiration to produce ATP without O2 or a mitochondria.

Anaerobic Respiration:

oxygen can kill the organism

Reactions on the next page:

Fermentation:

Uses Substrate-Level Phosphorylation to generate ATP – 2 net ATP

Occurs in the cytoplasm

Consists of Glycolysis

Only respiration in prokaryotes which do not contain a mitochondria.

Alcoholic Fermentation:

Pyruvate is converted to Ethanol in two steps, with the first releasing CO2

Lactic Acid Fermentation:

Pyruvate produces lactic acid and no release of carbon dioxide.

Figure 9.17

2 ADP

2 ATP

Glucose

Glycolysis

2 Pyruvate

2 CO2



2 NADH

2 Ethanol

2 Acetaldehyde

(a) Alcohol fermentation

(b) Lactic acid fermentation

2 Lactate

2 Pyruvate

2 NADH

Glucose

Glycolysis

2 ATP

2 ADP



NAD

2 H



NAD



2 H

Fermentation pathways.

Alcoholic Fermentation:

Produces carbon dioxide and ethanol

Lactic Acid Fermentation:

Produces lactic acid and no carbon dioxide

Both occur in the cytoplasm (glycolysis and glucose enters the pathway) and produce 2 ATP; neither require oxygen

Fermentation

FYI - Our wine and bread making yeasts (bottom panel – budding yeasts are reproducing) are using alcoholic fermentation and runners (panel are muscle cells) are using lactic acid fermentation.

Comparison of Respiratory Pathways

Respiratory Pathways:

Aerobic Respiration produces 32 – 36 ATP per glucose molecule
Fermentation and Anaerobic Respiration produce 2 ATP per glucose molecule

Obligate Anaerobes carry out Fermentation or Anaerobic Respiration and cannot survive (killed)in the presence of O2

Yeast and many bacteria are Facultative Anaerobes, meaning that they can survive in either oxygen (or no oxygen) using either Fermentation or Cellular Aerobic Respiration

Obligate Aerobes can only survive in oxygen and use Aerobic Respiration

Obligate Anaerobes

Carry out Fermentation or Anaerobic Respiration and cannot survive (killed) in the presence of O2

Facultative Anaerobes (yeast and many bacteria)

Meaning that they can survive in either oxygen (or no oxygen) using either Fermentation or Cellular Aerobic Respiration

Obligate Aerobes

can only survive in oxygen and use Aerobic Respiration

Evolution of Metabolism (Not on Test)

Evolution of Metabolism – Natural Selection favored organisms with more efficient methods of obtaining energy from organic molecules; Photosynthesis changed life on Earth forever!

Earliest Life degraded organic molecules present in the environment for their energy; these molecules were produced Abiotically by inorganic processes on Earth; “Primoidal Soup”

Glycolysis: occurred early; proteins through a series of reactions (pathway) were able to harvest the chemical bond energy in glucose (or other molecules) to produce ATP

Anoxygenic Photosynthesis: energy of light to produce ATP, not oxygen

Photosynthesis: energy of light to produce ATP but with production of oxygen; Cyanobacteria – life was changed forever on Earth!

Aerobic Respiration: leads to eukaryotic cells and multi-celled organisms

Your info – evolution of respiration from the primoidal soup billions of years ago to today.

To be continue in photosynthesis (Chapter 10), which we already discussed