Bioc lecture 2

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  • Lecture slides, booklets, and learning resources contain material used under copyright licenses for teaching.
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What is Biochemistry?

  • Biochemistry sits at the interface of chemistry and biology; it explains how biological molecules carry out life processes. The course emphasizes how biochemistry underpins biology, cell biology, chemistry, and physics.
  • References for context include textbooks such as Campbell et al. and Papachristodoulou et al., and the Lecture Booklet Part 1 – Proteins (pages 2–4). These sources frame the concepts rather than requiring memorization of all principles in those chapters.
  • The central idea is to focus on how biomolecules interact to regulate cellular function, not just on isolated scientific principles.

The Big Picture: Structure, Function, and Regulation

  • The structure and function of biological molecules are closely connected; changes in structure affect function.
  • Regulation of cellular function depends on interactions among biomolecules.
  • Biochemical principles underpin enzyme function in metabolism and other cellular processes.
  • Real-world relevance includes understanding how drugs work by manipulating molecular interactions.

The Molecules of Life: A Hierarchy (Slide overview)

  • Biochemistry spans from atoms and sub-atomic particles (physics) to small molecules (chemistry) to large biomolecules (biochemistry) to organelles (anatomy) to tissues and organs (physiology).
  • This hierarchical view helps explain how molecular interactions drive cellular and organismal function.

How Do Cells Accomplish Core Tasks? (Biochemistry as the enabler)

  • Sense and respond to their environment.
  • Make and break molecules.
  • Access and use the energy in food.
  • All of these depend on biochemistry and the interactions of biomolecules.

A Real-World Example: Lactation in Mammals

  • Mammals produce milk for infants as a key biological function; this can be used to illustrate how biochemistry enables complex physiological traits.
  • A lighthearted slide emphasizes lactation physiology: "MILK? GET LOST! IT'S FOR MY KIDS." (example of the real-world relevance and social context of biology).

A Foundational Example: Lactase Persistence (Genetics & Evolution)

  • A notable mutation related to lactase persistence shows convergent adaptation in Africa and Europe, illustrating how biochemistry intersects with genetics and evolution.
  • Reference: Tishkoff et al., Nature Genetics, 2007 (lactase persistence mutation and its evolutionary significance).
  • This example underscores how biochemical traits arise from genetic variation and environmental pressures.

Central Dogma: Flow of Genetic Information

  • Core concept: information flows from DNA to functional molecules via transcription and translation (DNA replication is the basis for genetic inheritance).
  • Diagrammatic representation:
    \text{DNA} \xrightarrow{\text{replication}} \text{DNA}
    \text{DNA} \xrightarrow{\text{transcription}} \text{RNA} \xrightarrow{\text{translation}} \text{Protein}
  • Summary: DNA is replicated; transcription converts DNA to RNA; translation converts RNA to protein, which are the functional molecules in cells.

Protein Structure and Function: A Key Concept

  • The sequence of amino acids determines how a protein folds; this folding defines the protein’s 3D structure and, therefore, its function.
  • Analogy: a long polypeptide chain can be pictured as a reed that can be woven into a basket; folding organizes the chain into a functional form.
  • The tertiary structure (the overall 3D shape) is crucial for activity and specificity.
  • Example mentioned: lactase (an enzyme) has a defined tertiary structure that enables lactose hydrolysis.
  • Supporting concept: local interactions such as ionic bonds (e.g., Asp, Glu with Lys or Arg) contribute to shape complementarity and stability.

From Gene to Protein: Transcription and Translation (More detail)

  • Transcription: DNA sequence is copied into RNA sequence.
  • Translation: RNA sequence is used to synthesize a protein on ribosomes.
  • Diagrammatic flow:
    \text{Gene}1 \to \text{mRNA}1 \quad (\text{transcription})
    \text{Gene}2 \to \text{mRNA}2 \quad (\text{transcription})
  • This flow links genotype to phenotype: gene sequences determine the amino acid sequence of proteins, which then fold into functional structures.

Making and Isolating Proteins: A Practical Biochemistry Pipeline

  • Protein expression in a host cell is used to produce proteins of interest.
  • Steps include:
    • Insert the genes of interest into a plasmid.
    • Transfect the plasmid into the host cell.
    • Expand the host organism in a bioreactor to yield biomass.
    • Purify the expressed protein (protein purification).
  • Outcomes include soluble protein that can be studied or used in applications.

Proteins as Interaction Machines: Solubility and Function

  • Biochemists study how molecules and molecular interactions allow cells to solve problems.
  • A key practical application is manipulating biomolecular interactions to influence drug action and effectiveness.

Structural Insights: How Molecules Interact

  • Solved structures reveal how molecules interact, including active sites and binding pockets.
  • Example of interactions:
    • Shape complementarity between ligand and receptor.
    • Ionic bonds between amino acid side chains (e.g., Aspartate, Glutamate with Lysine or Arginine).
  • Such interactions underpin enzyme specificity and catalysis.

Cellular Sensing and Signaling: The Signal Transduction Pathway (Slide 17)

  • Cells sense extracellular signals via receptors in the plasma membrane.
  • Signal transduction involves relay molecules to propagate the signal inside the cytoplasm.
  • Outcome: Activation of a cellular response.
  • Core components: extracellular signaling molecule, plasma membrane receptor, transduction pathway, intracellular relay molecules, and cellular response.

Making and Breaking Molecules: Enzymatic Roles in Metabolism (Slide 18)

  • Example: Lactase enzyme catalyzes hydrolysis of lactose, converting lactose into its monosaccharide components D-galactose and D-glucose.
  • Chemical transformation illustrated by structure changes in lactose as it is split into monosaccharides.
  • The lactase-lactose example demonstrates how specific enzymes enable metabolic steps.

Energy in Cells: Metabolism Overview (Slide 19)

  • Cellular energy comes from catabolic and anabolic processes:
    • Catabolism: Oxidative, exergonic reactions that break nutrients down to produce energy.
    • Anabolism: Reductive, endergonic reactions that build biomolecules from precursors.
  • Nutrients (e.g., glucose, fats, protein) plus O2 yield CO2 and H2O, releasing energy that is captured as ATP.
  • Basic overall reaction (conceptual):
    \text{Nutrients} + \text{O}2 \rightarrow \text{CO}2 + \text{H}_2\text{O}
  • ATP: The energy currency of the cell; ATP synthesis can be summarized as
    \text{ADP} + \text{P}_i \rightarrow \text{ATP}
  • This energy is used to power anabolic processes and cellular work.

The Electron Transport Chain and ATP Synthesis (Slides 20–21)

  • The Electron Transport Chain (ETC) consists of multiple components (e.g., NADH, FADH2, UQ, cytochromes like cyt c, cytochrome b, and complex IV with Cyt a3) embedded in the mitochondrial inner membrane.
  • Reducing equivalents (NADH, FADH2) donate electrons to the chain, which are transferred through carriers (e.g., UQ, cyt c1, Fe-S clusters, Cyt b, Cyt c, etc.).
  • Proton pumping across the inner mitochondrial membrane creates a proton gradient (proton motive force).
  • The gradient drives ATP synthesis via ATP synthase, ultimately producing ATP from ADP and Pi.
  • Final electron acceptor is O2, which forms water:
    \text{O}2 + 4\text{e}^- + 4\text{H}^+ \rightarrow 2\text{H}2\text{O}
  • The slides show a schematic of the chain with entries like NADH, NAD^+, FAD, FADH2, UQ, Cyt c1, Fe-S clusters, Cyt b, Cyt c, Cyt a, Cyt a3, etc.

ATP Synthase and Energy Conversion (Slide 21)

  • ATP synthase uses the proton motive force to synthesize ATP from ADP and Pi.
  • This enzyme complex is essential for converting the energy stored in the proton gradient into usable chemical energy in ATP.

Resources and Further Reading (Slide 22)

  • PDB-101: ENZYMES resource for structural biology and enzyme information.
  • Professors and scholars referenced for more depth:
    • Prof. Peter Mace on enzymes
    • Assoc Prof. Lynette Brownfield on ETC and mitochondria
    • Prof. Debbie Hay on signaling pathways
    • Dr. Nicole Power on protein expression and purification

Careers for Biochemists (Slide 23)

  • Medicine: Analyze patient samples or train as a physician/ dentist.
  • Research Science: Direct or participate in research on gene therapy, cancer treatments, etc.
  • Food & Cosmetic Industries: Develop safe and effective products.
  • Agriculture: Create crops with better yield or drought resistance.
  • Patent Law: Interpret scientific documents for biotech patenting.
  • Pharmaceuticals: Develop vaccines, drugs, and diagnostic tools.
  • Publishing: Write/review scientific or medical articles.
  • Education: Teach biology or chemistry; prepare museum exhibits.
  • Forensic Science: Investigate crimes using biological samples.

Objective-based Self-Assessment Questions (OBSA) — Lecture 2

  • 1) What is the central dogma of molecular biology?
  • 2) Why is the tertiary structure of a protein important?
  • 3) The sequence of determines how a protein folds.
  • 4) What type of interaction in a molecule is key to cellular function?
  • 5) What are some key questions biochemists ask?
    -Note: OBSA questions are designed to help you engage with the lecture style and prepare for future assessments; they reflect the approach used from Lecture 3 onward.

Connections: Foundational Principles and Real-World Relevance

  • The central dogma links genetic information with functional molecules, explaining how genotype leads to phenotype.
  • Protein structure-function relationships underpin enzyme catalysis, binding specificity, and metabolic control.
  • Cellular signaling demonstrates how information is conveyed and acted upon inside cells, enabling coordinated responses.
  • Energy metabolism (catabolism and anabolism) explains how cells harvest energy and use it to synthesize complex biomolecules.
  • The lactase/lactose example highlights how genetic variation can affect enzyme function and metabolic capabilities, illustrating evolution and personalized biology.
  • The integration of structural biology (PDB resources) with functional biochemistry (enzymes) shows how understanding structure informs drug design and therapeutic strategies.

Ethical and Practical Implications

  • Educational materials are copyrighted; use is limited to private study or university-approved activities.
  • The manipulation of molecular interactions (e.g., drug design) has ethical and societal implications, including safety, accessibility, and regulatory considerations.
  • Understanding genetics and metabolism has implications for personalized medicine, public health, and bioethics.

Quick Recap: Key Takeaways

  • Biochemistry explains how structure and interactions of biomolecules drive all cellular processes.
  • The central dogma describes information flow: DNA replication, transcription to RNA, and translation to protein.
  • Protein sequence determines folding; folding determines function; structure underpins activity and specificity.
  • Cells regulate function through signaling pathways and biomolecular interactions.
  • Metabolism encompasses catabolic energy-releasing pathways and anabolic energy-consuming pathways, with ATP as the energy currency.
  • The ETC and ATP synthase convert energy stored in electrochemical gradients into ATP.
  • Real-world examples (lactase, milk production, lactase persistence) illustrate genetics, evolution, and biochemistry in action.
  • Careers in biochemistry span medicine, research, industry, law, education, and forensics.