Chap004_PPT (2) physiology

Metabolism Overview

  • Metabolism: Total of all chemical reactions in the body.

  • Cellular Metabolism: Refers specifically to all chemical reactions within a cell, typically occurring in pathways or cycles.

    • Types of Metabolic Reactions:

      • Anabolism: Process where small molecules are combined into larger molecules, requiring energy (ATP).

      • Catabolism: Process where larger molecules are broken down into smaller molecules, releasing energy.

Anabolism and Catabolism

  • Anabolism Functions:

    • Provides materials for maintenance and growth.

    • Requires ATP produced during catabolic processes.

    • Example - Dehydration Synthesis:

      • Smaller molecules bonded to form larger molecules;

      • Water (H2O) is produced.

      • Important for producing polysaccharides, proteins, and triglycerides.

  • Catabolism Functions:

    • Breaks down larger molecules, producing ATP.

    • Example - Hydrolysis:

      • Used to decompose carbohydrates, proteins, and lipids;

      • Water is utilized to split substances;

      • Opposite of dehydration synthesis.

Control of Metabolic Reactions

  • All cells perform both anabolic and catabolic reactions.

  • Balance of catabolism and anabolism is crucial.

  • Enzymes:

    • Regulate rates of both catabolic and anabolic reactions;

    • Significantly increase reaction rates.

Metabolic Pathways

  • Definition: Series of enzyme-controlled reactions leading to product formation.

  • Each substrate is a product of the previous reaction.

  • Each step is catalyzed by different enzymes.

  • Rate-limiting Enzyme:

    • Regulatory enzyme that determines the rate of the entire pathway;

    • Usually the initial enzyme in the sequence.

    • Can be inhibited by the end product as a form of negative feedback.

Energy for Metabolic Reactions

  • Energy: Capacity to modify something or perform work.

  • Forms of Energy Include: Heat, light, sound, electrical energy, mechanical energy, chemical energy.

  • Principle of Energy: Energy cannot be created or destroyed, only transformed.

  • Cellular Respiration: Transfers energy from molecules for cellular use.

Release of Chemical Energy

  • Many metabolic processes utilize chemical energy stored in ATP.

  • Energy is released when chemical bonds are broken.

  • Oxidation: Releases energy from glucose through loss of hydrogen atoms and electrons.

  • Enzymes reduce activation energy required for oxidation in cellular respiration.

ATP Molecules Overview

  • ATP (Adenosine Triphosphate): Main energy-carrying molecule in cells.

    • Structure: Contains adenine, ribose (sugar), and three phosphate groups.

    • High-energy bonds exist between second and third phosphates; energy can be funneled into other chemical reactions.

  • ATP to ADP Conversion:

    • When ATP loses its terminal phosphate, it converts to ADP (Adenosine Diphosphate).

    • ADP can return to ATP through phosphorylation, which requires energy from cellular respiration.

Cellular Respiration

  • Processes Involved:

    • Glycolysis (anaerobic)

    • Citric Acid Cycle (aerobic)

    • Electron Transport Chain (aerobic)

  • Glycolysis and the Electron Transport Chain are sequential, while the Citric Acid Cycle is a metabolic cycle.

  • Final Products:

    • Carbon dioxide and water produced during respiration alongside 40% ATP and 60% heat.

  • Distinction between:

    • Anaerobic reactions: No O2, produce less ATP.

    • Aerobic reactions: Require O2, yield higher ATP.

Glycolysis

  • First step in glucose breakdown, occurring in the cytosol.

  • Process:

    • Consists of 10 reactions splitting glucose (6-carbon) into two 3-carbon pyruvic acid.

    • Generates 2 ATP molecules per glucose.

  • Phases of glycolysis:

    1. Phosphorylation of glucose.

    2. Splitting into two 3-carbon molecules.

    3. Production of NADH, ATP, and pyruvic acid.

Anaerobic and Aerobic Reactions

  • In the presence of O2, NADH delivers electrons to the Electron Transport Chain (ETC).

  • In absence of O2, lactate forms, inhibiting glycolysis and reducing ATP production.

  • Aerobic Pathways:

    • Begin with pyruvic acid entering mitochondria to form Acetyl CoA and proceed to produce more ATP.

  • End Products of Aerobic Processes: CO2, H2O, up to 36 ATP per glucose.

Citric Acid Cycle

  • Initiated when Acetyl CoA combines with oxaloacetic acid.

  • Continues producing ATP, hydrogen atoms, and CO2.

  • Each cycle returns to oxaloacetic acid enabling repetition as long as substrates are present.

Electron Transport Chain

  • NADH and FADH2 carry hydrogen and high-energy electrons to ETC in the inner mitochondrial membrane.

  • Electrons are used to create a proton gradient, driving ATP synthase for ATP production.

  • Summary:

    • Glycolysis: 2 ATP.

    • Citric Acid Cycle: 2 ATP.

    • Electron Transport Chain: 28 ATP.

Carbohydrate Storage

  • Carbohydrates can enter pathways for energy or be stored.

  • Excess glucose converts to:

    • Glycogen: Stored primarily in liver and muscle.

    • Fat: Stored in adipose tissue.

DNA Overview

  • Deoxyribonucleic Acid (DNA): Stores genetic information within nucleotide sequences directing protein synthesis.

  • Codes for various proteins including enzymes, structural proteins, antibodies, and membrane components.

Genetic Information Management

  • DNA Sequences: Encode instructions for constructing proteins.

    • Gene: Single DNA segment coding for one protein.

    • Genome: Complete genetic information in a cell.

    • Exome: Protein-coding portion of the genome.

    • Gene Expression: Regulation of protein production.

Structure of DNA

  • DNA forms a double helix structure, comprising two nucleotide chains with specific base pair connections (A-T, C-G).

    • Contains deoxyribose sugar, phosphate group, and nitrogenous bases.

  • Antiparallel Structure: Chains run in opposite directions, maintaining the double helix integrity.

DNA Replication

  • Necessary for cell division, ensuring daughter cells receive identical DNA.

  • Replication Process:

    1. Hydrogen bonds break, separating strands.

    2. New nucleotides pair through DNA polymerase activity.

    3. New sugar-phosphate backbones unite; resulting in two identical DNA strands.

Protein Synthesis Overview

  • Involves two key processes:

    • Transcription: Transfer of genetic information from DNA to mRNA.

    • Translation: Conversion of mRNA sequence into polypeptide chains.

  • A sequence of three nucleotides (codon) determines each amino acid's representation.

RNA Molecule Characteristics

  • Differs from DNA in structure and types:

    • Structure: Single-stranded, contains ribose, includes uracil in place of thymine.

  • Types of RNA: mRNA, tRNA, and rRNA, each playing distinct functional roles in synthesis.

Transcription Process

  • Occurs in the nucleus where DNA remains.

  • RNA polymerase facilitates complementary mRNA formation from the DNA strand.

  • The mRNA exits the nucleus, carrying the genetic information.

Translation Process

  • Synthesizes proteins in the cytoplasm via ribosomes:

    • tRNA conveys amino acids to ribosomes, supporting polypeptide formation.

    • Peptide bonds join amino acids until a stop codon is reached, releasing the completed protein.

Changes in Genetic Information

  • Variations among human genomes play significant roles in health and appearance.

  • DNA repair mechanisms exist for correcting mismatches and mitigating mutation effects.

Protections Against Mutations

  • Repair Enzymes: Correct nucleotide mismatches; genetic code redundancies often protect against mutations affecting proteins.

Practice Test: Metabolism and DNA Overview

1. Define metabolism and its types.

  • Metabolism: Total of all chemical reactions in the body.

    • Cellular Metabolism: All chemical reactions within a cell, typically occurring in pathways or cycles.

2. Differentiate between anabolism and catabolism.

  • Anabolism: Builds larger molecules from smaller ones, requiring energy (ATP).

  • Catabolism: Breaks down larger molecules into smaller ones, releasing energy.

3. What is the importance of enzymes in metabolic reactions?

  • Enzymes regulate the rates of anabolic and catabolic reactions and significantly increase reaction rates.

4. Explain the concept of metabolic pathways.

  • Series of enzyme-controlled reactions leading to product formation, where each substrate is a product of the previous reaction.

5. What are the end products of cellular respiration?

  • Carbon dioxide, water, ATP (40%), and heat (60%).

6. Describe the process of glycolysis.

  • Occurs in the cytosol; glucose (6-carbon) is split into two 3-carbon pyruvic acid, producing 2 ATP.

7. Differentiate between aerobic and anaerobic reactions.

  • Aerobic: Requires oxygen and yields higher ATP; Anaerobic: Does not require oxygen and produces less ATP.

8. Summarize the transcription and translation processes in protein synthesis.

  • Transcription: Converts DNA information to mRNA in the nucleus.

  • Translation: Synthesizes proteins in the cytoplasm via ribosomes where tRNA conveys amino acids.

9. What is the structure of DNA?

  • DNA forms a double helix with two nucleotide chains running antiparallel, contains deoxyribose sugar, phosphate group, and nitrogenous bases (A-T, C-G).

10. How do DNA repair mechanisms protect against mutations?

  • Repair enzymes correct mismatches, and genetic code redundancies protect against mutations affecting proteins.

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