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.