RESPIRATION AND

FERMENTATION: AEROBIC

AND ANAEROBIC OXIDATION

OF ORGANIC MOLECULES

Bio 107 – Week 6

Procedure 7.2

Label test tubes well, including group name

1) Add solutions listed to small test tubes

2) Fill remaining volume with yeast suspension

3) Slide larger test tube over the smaller tubes; hold smaller tube against the bottom of the larger tube and invert. There should be no air trapped at the top of the tube. Practice this first with just water.

4) Incubate tubes at 37˚C for 30 minutes.

5) After 30 minutes, measure the height (in millimeters) of the bubble of accumulated CO2. Record results in table 7.2

Tips and Tricks

Shake yeast bottles before using

Clean benches immediately when done (this stuff

gets sticky)

Rinse test tubes well and put upside-down in rack at

table.

Cellular Respiration

Cellular Respiration: oxidation of organic molecules

into energy in the form of ATP

ATP = Adenosine Triphosphate: organic molecule

containing high-energy phosphate bonds

Cellular Respiration - Summary

C6H

12O

6 + 6O

2 6CO

2+ 6H

20 + e- + 36-38ATP

Glucose is oxidized [removes electrons], O2 is reduced (oxidation-reduction reaction or REDOX)

Remember OIL RIG – Oxidized Is Loss (of electrons) and Reduction Is Gain)

Remember that adding/removing a hydrogen is a way of adding/removing an electron

One glucose yields 36-38 ATP

Electrons (as H) moved by coenzymes NAD+ and NADH2

Steps of Cellular Respiration

Glycolysis

Prep Reactions

Krebs Cycle

Electron Transport

Chain

Respiration: Glycolysis

Energy Investment Step

Two ATP used to split glucose into two 3-carbon molecules

Energy-Harvesting Step

1) 3-carbon molecules oxidized by NAD+, resulting in two NADHs

2) Phosphate group added to each.

3) Substrate-level ATP synthesis or substrate-level phosphorylation: enzyme passes high-energy phosphate to ADP, and ATP results (adenosine diphosphate triphosphate (+2 ATP, 3PG (3-phosphoglycerate))

4) 3PG is oxidized by the removal of water (+2H2O, 2 PEP)

5) Substrate-level ATP synthesis again. (+2 more ATP, 2 pyruvate)

NET GAIN: 2 ATP, (because we used two in energy investment) + 2 pyruvate.

Respiration: Glycolysis

Glycolysis: “Sugar-splitting” or “Energy investing” step

Occurs in cytoplasm

Requires 2ATP

Glucose split into 2 Pyruvate

Respiration: First Set of Reactions

Glycolysis: “Sugar-splitting” or “Energy investing” step

Occurs in cytoplasm

Requires 2ATP

Glucose split into 2 Pyruvate

Final Products:

2 NET ATP (4 produced, but 2 were used)

2 NADH

2 Pyruvate

If Oxygen is Present…

Prep Reactions

Pyruvate oxidation into acetyl-CoA

One NADH produced

Citric Acid Cycle

Occurs in matrix of mitochondria

Acetyl-CoA oxidized into two CO2

Produces 1 ATP per turn

Store energy in electron carries such as NAD+ and FAD+

Electron Transport Chain

Electrons from NADH and FADH2 move through a series of proteins called the ETC

Potential energy released during these redox reactions creates proton gradient across a membrane; flow of protons across the membrane generates ATP

If No Oxygen is Present…

NADH reduces Pyruvate

C6H12O6 2CO2 + 2C2H5OH + ATP

C6H12O6 2CH3CHOHOCOOH + ATP

Occurs in anaerobic organisms (anaerobes)

Occurs temporarily in plants and animals

Roots in anaerobic soils

In muscles for rapid bursts of energy

Glucose

Glycolysis

Pyruvate

Animals, some

microbes

Plants, some

microbes

CO2

Lactate Ethanol

NADH

NAD+

NADH

NAD+

Yeast – our organism

Unicellular sac fungi –

eukaryotes, kingdom Fungi,

phylum Ascomycota

Obtain food from organic matter

In the wild – found in soil, water,

surface of animals and plants

Many species/strains used to

make bread, beer, whiskey and

more!

Also can cause disease

(Candida, opportunistic)

What undergoes Fermentation?

Anaerobes – organisms that live without oxygen

Some use nitrate, sulfate or other inorganic compounds

as electron acceptors instead of oxygen

Some use glycolysis reduce the pyruvate

Other organisms can undergo fermentation when

their cells are depleted of oxygen (such as during

exercise)

Advantages/Disadvantages?

Disadvantages:

Less ATP produced (2 VS 36/38 in aerobic respiration)

Produces toxins (lactic acid or ethanol)

Advantages:

Can produce ATP without oxygen – survival!

Byproducts used in many foods (economic value, not a

biological advantage)

Lab Results

Table 7.2 – Fermentation By Yeast

Tube Sugar Initial Gas

Height

Final Gas

Height

Net Change Ease of

Fermentation

(Rank)

1 Water/None

2 Glucose

3 Fructose

4 Sucrose

Glucose Sucrose

Procedure 7.2

Label test tubes well, including group name

1) Add solutions listed to small test tubes

2) Fill remaining volume with yeast suspension

3) Slide larger test tube over the smaller tubes; hold smaller tube against the bottom of the larger tube and invert. There should be no air trapped at the top of the tube. Practice this first with just water.

4) Incubate tubes at 37˚C for 30 minutes.

5) After 30 minutes, measure the height (in millimeters) of the bubble of accumulated CO2. Record results in table 7.2

Tips and Tricks

Shake yeast bottles before using

Clean benches immediately when done (this stuff

gets sticky)

Rinse test tubes well and put upside-down in rack

by the sink.