Download Lactic Acid Fermentation - Advanced

Lactic Acid Fermentation Advanced
Douglas Wilkin, Ph.D.
Barbara Akre
Say Thanks to the Authors
Click http://www.ck12.org/saythanks
(No sign in required)
To access a customizable version of this book, as well as other
interactive content, visit www.ck12.org
CK-12 Foundation is a non-profit organization with a mission to
reduce the cost of textbook materials for the K-12 market both in
the U.S. and worldwide. Using an open-source, collaborative, and
web-based compilation model, CK-12 pioneers and promotes the
creation and distribution of high-quality, adaptive online textbooks
that can be mixed, modified and printed (i.e., the FlexBook®
textbooks).
Copyright © 2015 CK-12 Foundation, www.ck12.org
The names “CK-12” and “CK12” and associated logos and the
terms “FlexBook®” and “FlexBook Platform®” (collectively
“CK-12 Marks”) are trademarks and service marks of CK-12
Foundation and are protected by federal, state, and international
laws.
Any form of reproduction of this book in any format or medium,
in whole or in sections must include the referral attribution link
http://www.ck12.org/saythanks (placed in a visible location) in
addition to the following terms.
Except as otherwise noted, all CK-12 Content (including CK-12
Curriculum Material) is made available to Users in accordance
with the Creative Commons Attribution-Non-Commercial 3.0
Unported (CC BY-NC 3.0) License (http://creativecommons.org/
licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated
herein by this reference.
Complete terms can be found at http://www.ck12.org/about/
terms-of-use.
Printed: December 21, 2015
AUTHORS
Douglas Wilkin, Ph.D.
Barbara Akre
www.ck12.org
C HAPTER
Chapter 1. Lactic Acid Fermentation - Advanced
1
Lactic Acid Fermentation Advanced
• Describe lactic acid fermentation.
• Describe how bacteria, including those we employ to make yogurt, make ATP in the absence of oxygen.
• Discuss how your muscles continue to work for you even when your respiratory and cardiovascular system
can no longer keep up a continuous supply of oxygen.
Is there enough ATP?
Yes. But not to keep this effort up for a long time. Short spurts of sprinting are sustained by fermentation in muscle
cells. This produces just enough ATP to allow these short bursts of increased activity.
Lactic Acid Fermentation: Muscle Cells and Yogurt
For chicken or turkey dinners, do you prefer light meat or dark? Do you consider yourself a sprinter or a long
distance runner? What is the biological difference between light meat or dark meat? Or between the two types of
runners? Would you believe it has something to do with muscle color?
FIGURE 1.1
Light meat or dark?
Sprinting or en-
durance? Muscle cells know two ways
of making ATP –aerobic and anaerobic
respiration.
1
www.ck12.org
Are Drumsticks and Athletic Prowess Related?
Muscle color reflects its specialization for aerobic or anaerobic metabolism. Although humans are obligate aerobes,
our muscle cells have not given up on ancient pathways which allow them to keep producing ATP quickly when
oxygen runs low. The difference is more pronounced in chickens and grouse ( Figure 1.2), which stand around all
day on their legs. For long periods of time, they carry out aerobic respiration in their “specialized-for-endurance”
red muscles. If you are familiar with grouse, you know that these birds “flush” with great speed over short distances.
Such “sprinting” flight depends on anaerobic respiration in the white cells of breast and wing muscle, allowing rapid
production of ATP in low oxygen situations.
No human muscle is all red or all white, but chances are, if you excel at sprinting short distances or at a sport such
as weight lifting, you have more white glycolytic fibers in your leg muscles, allowing anaerobic respiration. If you
run marathons, you probably have more red oxidative fibers, performing aerobic respiration.
FIGURE 1.2
Ruffed grouse use anaerobic respiration
(lactic acid fermentation) in wing and
breast muscles for quick bursts of speed
to escape from predators.
Lactic Acid Fermentation
You may have not been aware that your muscle cells can ferment. Fermentation is the process of producing ATP in
the absence of oxygen, through glycolysis alone. Recall that glycolysis breaks a glucose molecule into two pyruvate
molecules, producing a net gain of two ATP and two NADH molecules. Lactic acid fermentation is the type of
anaerobic respiration carried out by yogurt bacteria (Lactobacillus and others) and by your own muscle cells when
you work them hard and fast.
Lactic acid fermentation converts the 3-carbon pyruvate to the 3-carbon lactic acid (C3 H6 O3 ) (see Figure 1.3) and
regenerates NAD+ in the process, allowing glycolysis to continue to make ATP in low-oxygen conditions. Since there
is a limited supply of NAD+ available in any given cell, this electron acceptor must be regenerated to allow ATP
production to continue. To achieve this, NADH donates its extra electrons to the pyruvate molecules, regenerating
NAD+ . Lactic acid is formed by the reduction of pyruvate.
Lactic acid fermentation converts pyruvate to lactic acid, and regenerates NAD+ from NADH:
C3 H3 O3 (pyruvate) + NADH → C3 H6 O3 (lactic acid) + NAD+
For Lactobacillus bacteria, the acid resulting from fermentation kills bacterial competitors in buttermilk, yogurt, and
some cottage cheese. The benefits extend to humans who enjoy these foods, as well ( Figure 1.5).
You may have noticed this type of fermentation in your own muscles, because muscle fatigue and pain are associated
2
www.ck12.org
Chapter 1. Lactic Acid Fermentation - Advanced
FIGURE 1.3
Lactic acid, C3 H6 O3 .
FIGURE 1.4
Lactic acid fermentation makes ATP in the
absence of oxygen by converting glucose
to lactic acid (through a pyruvate intermediate). Making lactic acid from pyruvate
oxidizes NADH, regenerating NAD+ so
that glycolysis can continue to make more
ATP rapidly.
Each circle represents a
carbon atom.
FIGURE 1.5
Lactobacillus bacteria use the same type
of anaerobic respiration as our muscle
cells.
Lactic acid reduces competition
from other bacteria and flavors yogurt.
3
www.ck12.org
with lactic acid. Lactic acid accumulates in your muscle cells as fermentation proceeds during times of strenuous
exercise. During these times, your respiratory and cardiovascular system cannot transport oxygen to your muscle
cells, especially those in your legs, fast enough to maintain aerobic respiration. To allow the continuous production
of some ATP, your muscle cells use lactic acid fermentation.
Vocabulary
• fermentation: Type of anaerobic respiration that includes glycolysis followed by the conversion of pyruvic
acid to one or more other compounds and the formation of NAD+ ; the process of producing ATP in the
absence of oxygen through glycolysis.
• lactic acid fermentation: The process for making ATP in the absence of oxygen by converting glucose to
lactic acid.
• obligate aerobe: An organism which requires oxygen for cellular respiration.
Summary
• Some bacteria, including those we employ to make yogurt, make ATP using lactic acid fermentation.
• Muscle cells can continue to produce ATP when oxygen runs low using lactic acid fermentation, but muscle
fatigue and pain may result.
Explore More
Use the resources below to answer the questions that follow.
• Fermentation at http://www.tempeh.info/fermentation/fermentation.php
1. What is fermentation?
2. What are the fermentation end products of the following:
a. Lactobacillus.
b. Saccharomyces (yeast).
• Lactic Acid Fermentation at http://www.tempeh.info/fermentation/lactic-acid-fermentation.php
1. What is the most important lactic acid producing bacteria?
2. List 5 foods produced by lactic acid fermentation.
3. Describe the fermentation process in yogurt production.
Review
1. Define lactic acid fermentation.
2. Identify yourself as a “sprinter” or an “endurance runner” and predict the type of muscle fiber (red or white)
which predominates in your body. Explain your reasoning.
3. What is the chemical equation of lactic acid fermentation?
4
www.ck12.org
Chapter 1. Lactic Acid Fermentation - Advanced
References
1. Left: Bonnie Bogle; Right: Flickr:davidd. Left: http://www.flickr.com/photos/bonniebogle/2064488794/;
Right: http://www.flickr.com/photos/puuikibeach/7721993052/ . CC BY 2.0
2. Flickr:Seabamirum. http://www.flickr.com/photos/seabamirum/3447982213/ . CC BY 2.0
3. CK-12 Foundation. CK-12 Foundation . CC BY-NC 3.0
4. Hana Zavadska. CK-12 Foundation . CC BY-NC 3.0
5. Flickr:Mom the Barbarian. http://www.flickr.com/photos/momthebarbarian/2441500/ . CC BY 2.0
5