Review - Important Concepts for Lectures over Metabolism Show I assume that you have had an introduction to the basics of metabolism in an introductory biology course. The metabolism you learned was probably entirely focused on the types of metabolism that animal (maybe plant) cells carry out --aerobic respiration; perhaps you were exposed to lactic acid fermentation (When muscles are working very hard, they may be temporarily depleted of oxygen, muscle cells can perform lactic acid fermentation for a short period of time. The lactic acid end products are secreted by the muscle cells into your tissues, and you feel the lactic acid as muscle soreness).� The microorganisms are tremendously more diverse and complex in metabolic patterns than are Eucarya and I want to spend our time emphasizing what microbes can do, not just covering what you have already had in other courses. So, if you do not remember the basics of metabolism you will need to review. The following pages should serve as a reminder. If it doesn�t all come back to you then read Chapter 5 in the text.� If you have not had chemistry you will also need to read Chapter 2. Review of oxygen tolerance: � Obligate anaerobe � does not require O2. � Aerotolerant anaerobe � does not require O2 for . � Microaerophile � needs a little O2 for metabolism, but less than amount present in the atmosphere. � Facultative anaerobe � can switch its metabolism based on whether or not O2 is present. � Aerobe (obligate aerobe) � requires O2 for metabolism. Review of nutritional patterns: Source of energy������������ Source of carbon Chemicals���������������������� CO2 (used by autotrophs) organic������������������������ Organic molecules (-C-C-C-) (used by heterotrophs) inorganic Light Most common combinations of Energy gaining strategy plus Carbon gaining strategy Chemoorgano heterotrophs Chemolitho autotrophs Photo autotrophs Photo heterotrophs You should also know Definitions of metabolism, anabolism, and catabolism That ATP (Adenosine Tri Phosphate) is made to store energy and used to release energy � it is the energy �currency� for the cell. Pyruvate is a key intermediate molecule in many catabolic pathways. Should understand basics of oxidations - reductions Remember - A loss of an electron is called an oxidation; a gain of an electron is called a reduction (remember as: LEO the lion says GER). In biological molecules it is usually the entire H atom (electron and proton) that is lost or gained, but not always. Sometimes the electrons are separated from the proton and only the electrons are lost or gained; and sometimes it may be one H atom + 1 electron (from a second H atom) that are lost or gained. In any pair of molecules you can distinguish which is the oxidized and which is the reduced: Oxidized state��������������������������������������������� Reduced state: Contains more oxygen atoms OR���������������� Contains fewer oxygen atoms OR fewer hydrogen atoms AND��������������� ��������� more hydrogen atoms AND therefore has fewer electrons and is�������������� therefore has more electrons and is less negative or more positive������������� ��������� more negative or less positive Example pairs: Glucose������ ������������������ ������������������ ��������� Pyruvate C6H12O6��������������� ������������������ ������������������ C3H4O3 NAD+��������������������������������������������������������� NADH Sulfate�������������������������������������������������������� Hydrogen sulfide SO4������������������������������������������������������������ H2S All cells need: 1. A source of carbon for making cellular molecules. There are two strategies for obtaining carbon: a. Recycle the C already present in some organic (-C-C-) molecule b. Use CO2 from the atmosphere 2. A source of energy for performing all cellular work (building molecules, transport across the plasma membrane, locomotion, etc.) Energy is created by harvesting the electrons present in:
Note � fermentation is NOT anaerobic respiration. By definition respiration requires both an electron transport chain and an inorganic terminal electron acceptor. Fermentation does not employ an electron transport chain and the terminal electron acceptor is an organic molecule. Fermentation takes place in the absence of oxygen, it can occur in anoxic and anaerobic environments, but it is not respiration! Comparison of Respiration vs Fermentation in Chemoorganotrophs
Comparison of Respiration in Chemoorganotrophs vs Chemolithotrophs
Which of the following can be used as terminal electron acceptors?Respiration always uses oxygen as a terminal electron acceptor.
Which of these are the most common energy sources used by Chemolithotrophic microbes?Inorganic Energy Sources. Chemolithotrophs use a variety of inorganic compounds as electron donors, with the most common substances being hydrogen gas, sulphur compounds (such as sulphide and sulphur), nitrogen compounds (such as ammonium and nitrite), and ferrous iron.
What is the terminal electron acceptor quizlet?At the end of the chain, the electrons join with protons and oxygen in the matrix fluid to form water. Thus oxygen is the final electron acceptor.
What compounds could be used as terminal electron acceptors in anaerobic respiration?Anaerobic respiration is the formation of ATP without oxygen. This method still incorporates the respiratory electron transport chain, but without using oxygen as the terminal electron acceptor. Instead, molecules such as sulfate (SO42-), nitrate (NO3–), or sulfur (S) are used as electron acceptors.
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