The purpose of this Biology Discussion is to help each other understand the main concepts presented in the chapters covered this week. General Biology, the required readings are Chapters 4 -7.
*One of the entries MUST ask a question about a concept/idea presented in the required readings in the textbook from the chapters covered this week. This should be a question pertaining to material that you personally do not understand or need clarification on and should be at least 40-50 words in length. Question topics cannot be claimed, and it is one question topic per student. This will aid in diversifying the discussion. Broad categories are posted already in the discussion board. Post your question under the category to which it best applies. State your question in the subject line of the post. This will create a list of questions and that everyone will be able to see.
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2BiologyDiscussion.docx
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Mader_Essentials_7e_LecturePPT_Ch07_ACCESS.pptx
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Mader_Essentials_7e_LecturePPT_Ch05_ACCESS.pptx
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Mader_Essentials_7e_LecturePPT_Ch06_ACCESS.pptx
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Mader_Essentials_7e_LecturePPT_Ch04_ACCESS.pptx
2 Biology Discussion
The purpose of this Biology Discussion is to help each other understand the main concepts presented in the chapters covered this week. General Biology, the required readings are Chapters 4 -7.
Each student must make at least three (3) entries during the week. *One of the entries MUST ask a question about a concept/idea presented in the required readings in the textbook from the chapters covered this week . This should be a question pertaining to material that you personally do not understand or need clarification on and should be at least 40-50 words in length. Question topics cannot be claimed, and it is one question topic per student. This will aid in diversifying the discussion. Broad categories are posted already in the discussion board. Post your question under the category to which it best applies. State your question in the subject line of the post. This will create a list of questions and that everyone will be able to see. *The two remaining entries must offer an explanation in answer to a classmate’s question. Your responses must be researched, and the content of your response must be supported by reliable and credible resources. These two response posts must be a minimum of 200 words each. *Ground rules for the Biology Discussion: Each post must be in your own words. Do NOT copy and paste from the Internet. [Review the Plagiarism presentation in the Student Resource Center.] It is better to paraphrase content/information (putting the content/information in your own words) from a resource. Paraphrased information from resource is required to be properly cited per APA requirements*, with it-text citations immediately following the information and a full reference citation at the end of the discussion board posting. [*Refer to the Getting Started area of the class for ‘Helpful Resources & Websites on Referencing Sources per APA’ and to the Student Resources tab on the left-hand side of the classroom.]
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Chapter 7
Energy for Cells
Essentials of Biology
SEVENTH EDITION
Sylvia S. Mader Michael Windelspecht
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7.1 Cellular Respiration
Produces ATP molecules for energy
Requires oxygen and glucose; produces carbon dioxide and water
Reason you breathe
Essentially the reverse of photosynthesis
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Figure 7.1 Cellular Respiration
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(photo): Juice Dash/Shutterstock
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Glucose Is Broken Down in Steps
Phases of complete glucose breakdown
Glucose broken down slowly in steps
Allows energy to be captured and used to make ATP
Coenzymes (nonprotein helpers) join with hydrogen
N A D⁺ → NADH
F A D⁺→ FADH2
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Cellular Respiration Involves Redox Reactions
Oxidation = removal of hydrogen atoms
Hydrogens removed from glucose
Gives waste product carbon dioxide
Reduction = addition of hydrogen atoms
Oxygen accepts hydrogens
Become waste product water
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Figure 7.3 The Four Phases of Complete Glucose Breakdown
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7.2 Outside the Mitochondria: Glycolysis
Glycolysis
In eukaryotes, takes place in the cytoplasm
Glucose (six carbons) broken down into two molecules of pyruvate (three carbons)
Divided into:
Energy-investment steps
Energy-harvesting steps
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Figure 7.4 Glycolysis, Energy-Investment Step
The following content is arranged like a table.
| 3PG 3-phosphoglycerate |
| BPG 1,3-bisphosphoglycerate |
| G3P glyceraldehyde 3-phosphate |
Energy-investment steps
Two ATP transfer phosphates to glucose
Activates them for next steps
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Figure 7.4 Glycolysis, Energy-Harvesting Steps
Energy-harvesting steps
Substrate-level ATP synthesis produces four ATP
Net gain of two ATP
Two NADH made
The following content is arranged like a table.
| 3PG 3-phosphoglycerate |
| BPG 1,3-bisphosphoglycerate |
| G3P glyceraldehyde 3-phosphate |
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Figure 7.6 Glycolysis Totals
Next step depends on oxygen availability.
With oxygen, pyruvate enters mitochondria.
Without oxygen, pyruvate undergoes reduction.
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7.3 Outside the Mitochondria: Fermentation 1
Oxygen is required for the complete breakdown of glucose in aerobic respiration.
Fermentation—anaerobic breakdown of glucose
Generates only two ATP total
Animal cells
Pyruvate reduced to lactate
Brief burst of energy for muscle cells
Recovery from oxygen deficit complete when enough oxygen is present to completely break down glucose
Lactate converted back to pyruvate or glucose
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Outside the Mitochondria: Fermentation 2
Microorganisms and fermentation
Bacteria use fermentation to produce:
Lactate or other organic acids
Alcohol and carbon dioxide
Yeast—carbon dioxide makes bread rise, ethanol made into wine and beer
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Figure 7.7 The Anaerobic Pathways, Glycolysis 1
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Figure 7.7 The Anaerobic Pathways 2
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(runner): Michael Svoboda/iStockphoto/Getty Images; (wine): C Squared Studios/Photodisc/Getty Images
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Figure 7.7 The Anaerobic Pathways 3
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(runner): Michael Svoboda/iStockphoto/Getty Images; (wine): C Squared Studios/Photodisc/Getty Images
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7.4 Inside the Mitochondria
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Keith R. Porter/Science Source
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Inside the Mitochondria, Preparatory Reaction
Preparatory reaction
Occurs in mitochondrial matrix
Produces a substrate that enters the citric acid cycle
Occurs twice per glucose molecule
Pyruvate oxidized, C O2 molecule given off
N A D⁺ →NADH
2-carbon acetyl group attached to CoA to form acetyl-CoA
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Inside the Mitochondria, Citric Acid Cycle
Citric Acid Cycle
Occurs in matrix of mitochondria
Acetyl CoA transfer acetyl group to C4 molecule—produces citric acid (six carbons)
CoA returns to preparatory reaction for reuse
Acetyl group oxidized to carbon dioxide
N A D⁺ →NADH and F A D →FADH2
Substrate-level ATP synthesis produces ATP
Two cycles for each glucose molecule
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The Preparatory Reaction
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The Citric Acid Cycle
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Figure 7.11 Inputs and Outputs of the Citric Acid Cycle
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Electron Transport Chain 1
Electron transport chain location
Located in cristae of mitochondria
Series of carriers pass electrons from one to the other
NADH and FADH2 deliver electrons
Hydrogen atoms attached consist of e⁻ and H²
Carriers accept only e⁻ not H²
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Electron Transport Chain 2
High-energy electrons enter/low-energy electrons leave
As pair of electrons passed from one carrier to the next, energy is released.
Will be captured for ATP production
Final electron acceptor is oxygen—forms water.
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Figure 7.13a The Electron Transport Chain
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ATP Synthase
ATP synthesis carried out by ATP synthase in inner mitochondrial membrane
Carriers of electron transport system pass electrons
Energy used to pump H⁺ from matrix into intermembrane space—creates H⁺ gradient
ATP synthase uses energy to make ATP.
Figure 7.13b
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Figure 7.13 The Organization of Cristae
Orange arrow indicates flow of electrons through carriers in ETC
H⁺ ions accumulate in intermembrane space and are then used to in the ATP synthase complex to form ATP.
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7.5 Metabolic Fate of Food
Energy yield from glucose metabolism
Maximum of 38 ATP made
Some cells make only 36 ATPs or less.
36–38 ATP about 40% of available energy in a glucose molecule
Rest is lost as heat.
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Alternative Metabolic Pathways, Fats and Proteins
Cells use other energy sources such as proteins and fats.
Fatty acids have longer carbon chains—yields more ATP.
Intermediates can also be used to make other products.
Extra food made into fat for storage.
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(photo): C Squared Studios/Photodisc/Getty Images
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End of Main Content
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Figure 7.1 Cellular Respiration – Text Alternative
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The respiration process involves intake of oxygen and glucose and the release of carbon dioxide and water which takes place in the mitochondrion. The mitochondrion has a double membrane (inner and outer membranes), matrix, cristae, and intermembrane space.
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Cellular Respiration Involves Redox Reactions – Text Alternative
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In the reaction, glucose combines with six molecules of oxygen giving six molecules of carbon dioxide, six molecules of water, and energy. Both oxidation and reduction occur during cellular respiration. The glucose molecule is oxidized to produce carbon dioxide and oxygen molecules are reduced to generate water molecules.
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Figure 7.3 The Four Phases of Complete Glucose Breakdown – Text Alternative
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The first stage of cellular respiration is glycolysis in which a glucose molecule breaks down into pyruvate. Glycolysis occurs in the cytoplasm of the cell. The net gain of ATP in glycolysis is 2ATP. The pyruvate enters into mitochondria and undergoes a preparatory reaction. C O2 is produced in the reaction. Further, the products of the preparatory phase undergo a citric acid cycle reaction during which 2ATP and C O2 are produced. The last step is the electron transport chain. During the process, the carrier molecule NADH transfers electrons from the original glucose molecule to an electron transport chain. In this way, the electrons move within the inner membrane of the mitochondria by NADH and FADH2, ultimately being pulled to oxygen found at the end of the chain. The oxygen and electrons combine with hydrogen ions to form water. This step generates 34 ATP molecules.
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7.2 Outside the Mitochondria: Glycolysis – Text Alternative
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The first stage of cellular respiration is glycolysis in which a glucose molecule breaks down into pyruvate. Glycolysis occurs in the cytoplasm of the cell. The net gain of ATP in glycolysis is 2ATP. The pyruvate enters into mitochondria and undergoes a preparatory reaction. Further, the products of the preparatory phase undergo citric acid reaction during which 2ATP are produced. The last step of cellular respiration is the electron transport chain. During the process, the carrier molecule NADH transfers electrons from the original glucose molecule to an electron transport chain. In this way, the electrons move within the inner membrane of the mitochondria by NADH and FADH2. This step generates 34 ATP molecules.
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Figure 7.4 Glycolysis, Energy-Investment Step – Text Alternative
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Energy-investment step:
Six carbon glucose on the conversion of two ATP molecules into two ADP molecules forms a chain of two 3-carbon glyceraldehyde 3-phosphate (G3P) molecules linked together. Further, the chain of two glyceraldehyde 3-phosphate molecules bifurcates into two molecules of glyceraldehyde 3-phosphate.
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Figure 7.4 Glycolysis, Energy-Harvesting Steps – Text Alternative
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Right Top: Step 1: energy investment step: glucose is broken down to ADP and P which is converted to G3P and P. Step 2: energy-harvesting steps: G3P is converted to BPG, while N A D superscript positive is converted to NADH in the presence of P. BPG is converted to 3PG, while ADP is converted to ATP. 3PG is converted to water and P which is converted to pyruvate. Net gain: 2 ATP.
Left Bottom: In the reaction, the reactant shows a chain of three spheres having first and third spheres linked with two phosphate groups each. The bond of the first phosphate group is marked as substrate. The phosphate group attached to the third sphere binds to an enzyme and on the conversion of ADP into ATP gives the product as a chain of three spheres with the first sphere linked to a phosphate group. A dotted curvy arrow shows the linking of the phosphate group to the ADP molecule.
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Figure 7.6 Glycolysis Totals – Text Alternative
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The inputs of glycolysis include glucose, two molecules of N A D plus, two molecules of ATP, four molecules of ADP, and two Phosphates. The outputs include two molecules of pyruvate, two molecules of NADH, two molecules of ADP, and four molecules of ATP. The net gain is shown as two molecules of ATP.
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Outside the Mitochondria: Fermentation 2 – Text Alternative
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The inputs of fermentation include glucose, two molecules of NADH, two molecules of ATP, four molecules of ADP, and four Phosphates. The outputs include two molecules of lactate or two molecules of alcohol and two molecules of carbon dioxide, two molecules of N A D plus, two molecules of ADP, and four molecules of ATP. The process of fermentation shows a net gain of two molecules of ATP.
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Figure 7.7 The Anaerobic Pathways, Glycolysis 1 – Text Alternative
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The steps are as follows:
1. A 6-carbon glucose molecule converts into two molecules of a 3-carbon compound attached with a phosphate group at one end. Two molecules of ATP break into ADP with a net loss of two molecules of ATP.
2. Two molecules of a 3-carbon compound on the addition of two molecules of phosphate and conversion of two N A D positive into two NADH forms two molecules of another 3-carbon compound attached with phosphate groups at both ends.
3. Further, the 3-carbon compound on the conversion of four molecules of ADP into four molecules of ATP forms two molecules of pyruvate.
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Figure 7.7 The Anaerobic Pathways 2 – Text Alternative
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In fermentation, two molecules of pyruvate form either two molecules of lactate or two molecules of alcohol. The formation of lactate during fermentation is called lactic acid fermentation (exemplified by a photo of a woman in activewear bent down with her hands on her knees). The formation of alcohol during fermentation is called alcohol fermentation (exemplified by a photo of an alcohol bottle). If alcohol is formed, then the conversion of two NADH taken from glycolysis converts into two N A D positive, and two molecules of carbon dioxide are given out. The net gain of the process is 2 ATP.
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Figure 7.7 The Anaerobic Pathways 3 – Text Alternative
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