Metabolic+Processes

Cellular Respiration Practice Test   Photosynthesis Practice Questions   ** Cellular Respiration ** ** Ryan Smith ** ** April 27, 2011 **

The goal of cellular respiration is to produce energy. There are a series of steps involved, whether you are anaerobic or aerobic.

__Photoautotroph__ – An organism that makes its own food using light (e.g. plants).

__Heterotroph__ – An organism that relies on another organism for energy (e.g. humans must eat other organisms).

__Chemoautotroph__ – An organism that makes its own food using chemicals. These organisms are found in extreme environments, such as volcanoes and hot springs, and do not use glucose as energy.

__Obligate Anaerobe__ – An organism that must live in the absence of oxygen.

__Obligate Aerobe__ – An organism that must live in aerobic conditions.

__Facultative Anaerobes__ – Organisms that can tolerate aerobic conditions, but prefer anaerobic conditions.

**Cellular Respiration Equation:**

 C6H12O6(aq) + 6O2(g) à 6CO2 + 6 H2O + energy via heat + ATP <span style="display: block; font-family: 'Times New Roman'; margin-bottom: 0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 0cm; text-align: left;"> <span style="display: block; font-family: 'Times New Roman'; margin-bottom: 0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 0cm; text-align: left;">Each of the steps in the second graph is catalyzed by an enzyme, reducing the activation energy.

<span style="display: block; margin-bottom: 0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 0cm; text-align: left;">**[]**


 * Emily Brant **
 * April/2011 **

· All organisms do this · Anaerobic · Happens in the cytoplasm · Start with ** 1 glucose ** · End with ** 2 pyruvates ** · ** Net 2 ATP ** made (2 in; 4 made) · Make ** 2 NADH ** · In the cytoplasm · Anaerobic · *To regenerate NAD+ (needed for glycolysis to continue) __Lacticacid(Lactate)__ · Humans and bacteria do this · Start with ** 2 pyruvate **(3 carbon) · Make ** 2 lactate and 2 NAD+ **and CO2 waste __Alcohol__ · Yeast · Start with ** 2 pyruvate ** · Goes to acetaldehyde – CO2 waste · End with ** 2 alcohol and 2 NAD+ **
 * __Glycolysis__ **
 * __Fermentation__ **

· In the mitochondrial matrix · Not all do this, only aerobic · Start with ** 2 pyruvate (3 carbon) ** · End with ** acetyl-coA (2 carbon) ** · With reduction it makes CO2 waste · Make ** 2 NADH ** · To enter Krebs cycle need 2 carbon atom
 * __Pyruvate Oxidation__ **

· Aerobic · In the mitochondrial matrix · Start with ** acetyl-coA (2 carbon) ** · Acetyl-coA joins with ** oxaloacetate (4 carbon) **to make ** citrate (6 carbon) ** · Makes o ** ATP (1/turn) ** o ** FADH2 (1/turn) ** o ** 3 NADH (3/turn) ** o ** CO2 waste ** · ** This happens twice to make ** o ** 2 ATP ** o ** 6 NADH ** o ** 2FADH2 **
 * __Krebs Cycle__ **

· Innermitochondrial membrane matrix/innermembrane space · ** 3 ATP ** made from ** NADH in Krebs cycle ** · ** 2 ATP **made from ** FADH2 ** · ** 2 ATP ** made from ** NADH in Glycolysis ** · ** 2 ATP ** made from ** Glycolysis ** · Therefore resulting in: o ** 18 ATP ** from NADH in Kreb’s cycle o ** 4 ATP ** from FADH2 in Kreb’s cycle o ** 2 ATP **from Kreb’s cycle o ** 4 ATP ** from NADH in Glycolysis o ** 2 ATP ** from Glycolysis · This all reults in** 36 ATP: 32 ATP ** from NADH and FADH2 in Kreb’s, and ** 2 ATP ** from glycolysis and ** 2 ATP ** from Kreb’s cycle. (produce from ADP)
 * __Electron Transport Chain__ **

Gurpriya Kaberwal April 29, 2011


 * __ KREBS CYCLE __**

Following glycolysis, the mechanism of cellular respiration involves another multistep process—the Krebs cycle, which is also called the citric acid cycle or the tricarboxylic acid cycle. The **Krebs cycle** uses the two molecules of pyruvic acid formed in glycolysis and yields high-energy molecules of NADH and flavin adenine dinucleotide (FADH), as well as some ATP.

The Krebs cycle occurs in the mitochondrion of a cell. This sausage-shaped organelle possesses inner and outer membranes and, therefore, an inner and outer compartment. The inner membrane is folded over itself many times; the folds are called //cristae//. Located along the cristae are the important enzymes necessary for the proton pump and for ATP production.

Prior to entering the Krebs cycle, the pyruvic acid molecules are altered. Each three-carbon pyruvic acid molecule undergoes conversion to a substance called acetyl-coenzyme A, or acetyl-CoA. During the process, the pyruvic acid molecule is broken down by an enzyme, one carbon atom is released in the form of carbon dioxide, and the remaining two carbon atoms are combined with a coenzyme called coenzyme A. This combination forms acetyl-CoA. In the process, electrons and a hydrogen ion are transferred to NAD to form high-energy NADH.

Acetyl-CoA now enters the Krebs cycle by combining with a four-carbon acid called oxaloacetic acid. The combination forms the six-carbon acid called citric acid. Citric acid undergoes a series of enzyme-catalyzed conversions. The conversions, which involve up to ten chemical reactions, are all brought about by enzymes. In many of the steps, high-energy electrons are released to NAD. The NAD molecule also acquires a hydrogen ion and becomes NADH. In one of the steps, FAD serves as the electron acceptor, and it acquires two hydrogen ions to become FADH2. Also, in one of the reactions, enough energy is released to synthesize a molecule of ATP. Because for each glucose molecule there are two pyruvic acid molecules entering the system, two ATP molecules are formed.

Also during the Krebs cycle, the two carbon atoms of acetyl-CoA are released, and each forms a carbon dioxide molecule. Thus, for each acetyl-CoA entering the cycle, two carbon dioxide molecules are formed. Two acetyl-CoA molecules enter the cycle, and each has two carbon atoms, so four carbon dioxide molecules will form. Add these four molecules to the two carbon dioxide molecules formed in the conversion of pyruvic acid to acetyl-CoA, and it adds up to six carbon dioxide molecules. These six C02 molecules are given off as waste gas in the Krebs cycle. They represent the six carbons of glucose that originally entered the process of glycolysis. At the end of the Krebs cycle, the final product is oxaloacetic acid. This is identical to the oxaloacetic acid that begins the cycle. Now the molecule is ready to accept another acetyl-CoA molecule to begin another turn of the cycle. All told, the Krebs cycle forms (per two molecules of pyruvic acid) two ATP molecules, ten NADH molecules, and two FADH2 molecules. The NADH and the FADH2 will be used in the electron transport system. Image from: []

The electron transport system occurs in the cristae of the mitochondria, where a series of cytochromes (cell pigments) and coenzymes exist. These cytochromes and coenzymes act as carrier molecules and transfer molecules. They accept high-energy electrons and pass the electrons to the next molecule in the system. At key proton-pumping sites, the energy of the electrons transports protons across the membrane into the outer compartment of the mitochondrion.
 * __ ELECTRON TRANSPORT CHAIN __**

Each NADH molecule is highly energetic, which accounts for the transfer of six protons into the outer compartment of the mitochondrion. Each FADH2 molecule accounts for the transfer of four protons. Electrons pass from NAD to FAD, to other cytochromes and coenzymes, and eventually they lose much of their energy. In cellular respiration, the final electron acceptor is an oxygen atom. In their energy-depleted condition, the electrons unite with an oxygen atom. The electron–oxygen combination then reacts with two hydrogen ions (protons) to form a water molecule (H2O) The role of oxygen in cellular respiration is substantial. As a final electron receptor, it is responsible for removing electrons from the system. If oxygen were not available, electrons could not be passed among the coenzymes, the energy in electrons could not be released, the proton pump could not be established, and ATP could not be produced. In humans, breathing is the essential process that brings oxygen into the body for delivery to the cells to participate in cellular respiration. Image from: [] __** Photosynthesis **__
 * Ali Sharif - I have attached the notes here as a PDF. Good luck on the test tomorrow! **


 * NOTES: ** [[file:Photosynthesis.pdf]]

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