Overview of Cellular Respiration and Metabolism
Overview of Enzymes
Enzymes are primarily composed of proteins and may require nonprotein cofactors.
They act as organic catalysts that speed up cellular reactions.
They lower the activation energy required for chemical reactions, enabling metabolic reactions to occur at rates compatible with life.
Key Characteristics of Enzymes
Unique features:
Shape
Specificity
Function
Provide an active site for substrates (target molecules).
Enzymes are larger in size compared to their substrates.
They closely associate with substrates but are not integrated into the reaction products.
Enzymes are not consumed or permanently altered during reactions, enabling recycling and functioning in low concentrations.
Activity can be affected by temperature and pH.
Regulation can occur at multiple levels:
Feedback mechanisms
Genetic control mechanisms
Factors Affecting Enzyme Activity
Substrate Concentration: Increasing concentration can enhance reaction rates until saturation is reached.
Environmental Conditions: Deviations in temperature and pH can denature enzymes, affecting function.
Direct Regulation:
Competitive Inhibition: Another molecule competes for the substrate site.
Non-competitive Inhibition: Inhibitor binds elsewhere, reducing activity regardless of substrate concentration.
Allosteric Regulation: Molecules bind at sites other than active sites to activate/inhibit enzyme activity.
Feedback Inhibition: Metabolic pathways are regulated by final products inhibiting earlier steps.
Binding of Cofactors: Non-protein molecules that assist enzyme function (e.g., metal ions, vitamins).
Genetic Level Regulation: Induced or repressed transcription based on cellular needs.
Cellular Respiration Overview
Definition: Cellular respiration is the metabolic pathway for breaking down organic molecules to produce ATP for energy.
Key Learning Objectives:
Explain the role of redox reactions in cellular respiration.
Describe the three phases:
Glycolysis
Citric Acid Cycle (Krebs Cycle)
Oxidative Phosphorylation
Identify inputs and outputs of each stage and their cellular locations.
Discuss energy coupling and ATP synthesis from the electron transport chain.
Understand the number of ATP produced.
Define fermentation and metabolization of fats and proteins.
Explain regulation by allosteric activation and feedback inhibition.
Importance of Cellular Respiration
Essential for energy production in animals, plants, fungi, and protists.
Related to over 100 known mitochondrial disorders.
Defective mitochondria link to age-related issues (e.g., Alzheimer’s disease).
Metabolism Basics
Metabolism: The sum of all chemical and physical processes in a cell, including:
Catabolism: Breakdown of molecules releasing energy (e.g., cellular respiration).
Anabolism: Synthesis of compounds requiring energy (e.g., protein synthesis).
Nutritional Types
Carbon Source:
Heterotrophs: Organisms obtain organic forms of carbon (from other living organisms).
Autotrophs: Organisms use CO₂ as a carbon source, not dependent on other living organisms.
Energy Source:
Chemotrophs: Obtain energy from chemical compounds.
Phototrophs: Obtain energy through photosynthesis.
Mitochondria and ATP Production
ATP synthesizes in mitochondria as part of cellular respiration reactions.
Two Types of Respiration:
Aerobic Respiration: Requires oxygen as a reactant.
Anaerobic Respiration: Uses molecules other than oxygen (e.g., sulfate, nitrate).
Fermentation: Occurs when oxygen is limited, utilizing the electrons from NADH produced in glycolysis.
Overview of Enzymes
Enzymes are primarily composed of proteins and may require nonprotein cofactors.
They act as organic catalysts that speed up cellular reactions.
They lower the activation energy required for chemical reactions, enabling metabolic reactions to occur at rates compatible with life.
Key Characteristics of Enzymes
Unique features:
Shape
Specificity
Function
Provide an active site for substrates (target molecules).
Enzymes are larger in size compared to their substrates.
They closely associate with substrates but are not integrated into the reaction products.
Enzymes are not consumed or permanently altered during reactions, enabling recycling and functioning in low concentrations.
Activity can be affected by temperature and pH.
Regulation can occur at multiple levels:
Feedback mechanisms
Genetic control mechanisms
Factors Affecting Enzyme Activity
Substrate Concentration: Increasing concentration can enhance reaction rates until saturation is reached.
Environmental Conditions: Deviations in temperature and pH can denature enzymes, affecting function.
Direct Regulation:
Competitive Inhibition: Another molecule competes for the substrate site.
Non-competitive Inhibition: Inhibitor binds elsewhere, reducing activity regardless of substrate concentration.
Allosteric Regulation: Molecules bind at sites other than active sites to activate/inhibit enzyme activity.
Feedback Inhibition: Metabolic pathways are regulated by final products inhibiting earlier steps.
Binding of Cofactors: Non-protein molecules that assist enzyme function (e.g., metal ions, vitamins).
Genetic Level Regulation: Induced or repressed transcription based on cellular needs.
Cellular Respiration Overview
Definition: Cellular respiration is the metabolic pathway for breaking down organic molecules to produce ATP for energy.
Key Learning Objectives:
Explain the role of redox reactions in cellular respiration.
Describe the three phases:
Glycolysis
Start: Glucose (a 6-carbon sugar) as the initial input. Happens in the cytoplasm.
End: Produces two molecules of pyruvate (a 3-carbon compound), 2 ATP (net), and two molecules of NADH. No oxygen is required.
Citric Acid Cycle (Krebs Cycle)
Start (Transition Step): Pyruvate from glycolysis is first converted into Acetyl-CoA (a 2-carbon molecule) in the mitochondrial matrix, releasing CO₂ and producing NADH. Acetyl-CoA then enters the cycle.
End: For each Acetyl-CoA, the cycle produces 2 CO₂, 3 NADH, 1 FADH₂, and 1 ATP (or GTP). The cycle regenerates its starting molecule, oxaloacetate. Takes place in the mitochondrial matrix.
Oxidative Phosphorylation
Start: The high-energy electron carriers, NADH and FADH₂, generated from glycolysis and the Citric Acid Cycle, donate their electrons to the electron transport chain (ETC) in the inner mitochondrial membrane.
End: Electrons are passed down the ETC to the final electron acceptor, oxygen, forming water. The energy released pumps protons, creating a gradient used by ATP synthase to produce a large amount of ATP. This phase occurs in the inner mitochondrial membrane.
Identify inputs and outputs of each stage and their cellular locations.
Discuss energy coupling and ATP synthesis from the electron transport chain.
Understand the number of ATP produced.
Define fermentation and metabolization of fats and proteins.
Explain regulation by allosteric activation and feedback inhibition.
Importance of Cellular Respiration
Essential for energy production in animals, plants, fungi, and protists.
Related to over 100 known mitochondrial disorders.
Defective mitochondria link to age-related issues (e.g., Alzheimer’s disease).
Metabolism Basics
Metabolism: The sum of all chemical and physical processes in a cell, including:
Catabolism: Breakdown of molecules releasing energy (e.g., cellular respiration).
Anabolism: Synthesis of compounds requiring energy (e.g., protein synthesis).
Nutritional Types
Carbon Source:
Heterotrophs: Organisms obtain organic forms of carbon (from other living organisms).
Autotrophs: Organisms use CO₂ as a carbon source, not dependent on other living organisms.
Energy Source:
Chemotrophs: Obtain energy from chemical compounds.
Phototrophs: Obtain energy through photosynthesis.
Mitochondria and ATP Production
ATP synthesizes in mitochondria as part of cellular respiration reactions.
Two Types of Respiration:
Aerobic Respiration: Requires oxygen as a reactant.
Anaerobic Respiration: Uses molecules other than oxygen (e.g., sulfate, nitrate).
Fermentation: Occurs when oxygen is limited, utilizing the electrons from NADH produced in glycolysis.