RL3 20241121

Page 1: Introduction

  • Title: Budding Biologists of FNDN Biology 2024, Standard C Revision Lecture #3

  • Date: Term 1, Week 2, 21/11/24 Thursday

  • Lecturer: Dr. Manisha Sharma

Page 2: Learning Outcomes

  • Cell Differentiation

  • Organic Macromolecules

  • Proteins

  • Enzymes

    • Definition

    • Function

    • Active Site Specificity

    • Factors Affecting Enzyme Activity

Page 3: Thought Provocation

  • Are all cells in the body the same?

  • Do cells perform identical functions throughout the body?

  • How do flower cells differ from root cells?

    • Differences arise from Cell Differentiation.

Page 4: Cell Differentiation

  • Definition: Process where stem cells or groups of cells become specialized.

  • Examples of differentiated cells:

    • Intestinal Cells

    • Muscle Cells

    • Blood Cells

    • Liver Cells

    • Neuron Cells

    • Cardiac Cells

  • Cells organized into tissues and organs, forming a specific 3-D structure.

Page 5: Regulatory Mechanisms in Cell Differentiation

  • Highly regulated processes include:

    • Cytoplasmic Determinants: Influences from egg cytoplasm.

    • Inductive Signals: Molecular cues from neighboring cells guide differentiation:

      • Molecules and signals from lower-tier cells shape gene expression in surrounding cells.

      • Fertilization leads to distinct cell fates based on cytoplasmic determinant distribution.

Page 6: Molecular Basis of Differentiation

  • Pluripotent Cells: Can become multiple cell types.

    • In plants: Meristematic Tissues

    • In animals: Embryonic Stem Cells

  • Differentiation involves controlled gene expression:

    • Neurons express neuronal proteins, muscle cells express myosin and actin, heart cells express cardiac-specific proteins.

Page 7: Summary of Learning Outcomes

  • Focus continues on:

    • Cell Differentiation

    • Organic Macromolecules: Proteins

    • Enzymes: Definitions, structures, and functions.

Page 8: Organic Macromolecules

  • Definition: Macromolecules are polymers made from monomers linked by covalent bonds.

    • Proteins are the most abundant macromolecules in cells.

    • Analogy: Think of it as a long train, where each car represents a monomer.

Page 9: Diversity of Proteins

  • Enzymes are the most prevalent type of protein.

  • The study will focus on enzymes and their functionalities.

Page 10: Learning Outcomes Reiterated

  • Concentration on:

    • Cell Differentiation

    • Organic Macromolecules

    • Protein structure and enzyme functions.

Page 11: Proteins

  • Definition: Proteins are polymers made of amino acids.

  • Monomer unit: Amino acids with:

    • Side chain (R group)

    • Backbone containing Carbon, Hydrogen, Oxygen, and Nitrogen.

Page 12: Polymerization

  • Polymerization is the joining of monomers to form large polymers.

  • Peptide Bond Formation:

    • Occurs via dehydration reaction, resulting in the formation of polypeptides from amino acids.

    • The bond linking amino acids is called a peptide bond.

Page 13: Protein Folding

  • Functional proteins are formed by folding polypeptide chains.

  • Folding determines structure and thus function:

    • Enzymes must fold accurately to recognize substrates.

    • Antibodies fold to recognize specific antigens.

Page 14: Four Levels of Protein Structure

  • Primary Structure: Linear sequence of amino acids.

  • Secondary Structure: Stabilized by bonds between chains (e.g., alpha helices).

  • Tertiary Structure: 3-D shape stabilized by interactions between R groups.

  • Quaternary Structure: Association of multiple polypeptide chains.

Page 15: Complexity of Protein Structures

  • Complexity is determined by:

    • Size of polypeptide chains.

    • Number of chains.

    • Arrangement and folding of chains.

  • Secondary structures result from repeated atoms causing intermolecular forces.

Page 16: Learning Outcomes Summary

  • Continued focus on:

    • Cell Differentiation

    • Organic Macromolecules

    • Proteins and their specific structures and functions.

Page 17: Enzymes as Important Proteins

  • Enzyme folding creates an active site:

    • Composed of a few amino acids, essential for function.

    • Overall structure supports the active site’s function.

Page 18: Enzyme Function Overview

  • Enzymes speed up biological reactions.

  • Process:

    • E + S → ES → E + P

    • Enzymes are crucial because they facilitate metabolic reactions that would otherwise occur slowly.

Page 19: Mechanism of Enzyme Action

  • Lock and Key Model: Substrate fits precisely into the enzyme's active site.

  • The enzyme remains unchanged during the reaction.

Page 20: Induced Fit Model

  • The active site of the enzyme changes shape to accommodate the substrate.

  • After product formation, the enzyme returns to its original shape.

Page 21: Factors Affecting Enzyme Activity

  1. Substrate concentration

  2. Temperature of the environment

  3. pH of the environment

  4. Presence of inhibitors

  • Each enzyme has optimal conditions for maximum activity.

Page 22: Substrate Concentration Impact

  • Higher substrate concentration increases enzyme activity until saturation point:

    • Low concentration = low activity.

    • High concentration = optimal activity until all enzymes are occupied.

Page 23: Temperature Impact on Enzyme Activity

  • Enzymes have different optimal temperatures:

    • Low temperatures = low activity.

    • High temperatures can lead to denaturation, rendering the enzyme inactive.

Page 24: pH Effects on Enzyme Activity

  • pH is a measure of H+ ions:

    • Affects charge of functional groups within the active site.

    • Changes in charge can reduce substrate binding affinity, impacting enzyme efficacy.

Page 25: Inhibitors and Activators

  • Inhibitors: Chemicals that prevent enzyme functions.

    • Result: No product formation.

  • Activators: Enhance enzyme functions.

    • Result: Increased product formation.

Page 26: Types of Inhibition

  • Reversible Inhibition: Weak bonds with enzyme; reversible upon removal.

  • Irreversible Inhibition: Permanent bond with enzyme; cannot revert.

    • Example: Poisons or toxins.

Page 27: Mechanisms of Inhibition

  • Normal Binding: Enzyme works as intended.

  • Competitive Binding: Inhibitor mimics substrate and binds active site.

  • Non-Competitive Binding: Inhibitor binds elsewhere, altering enzyme's shape.

Page 28: Activator Functionality

  • Activators enhance enzyme activity, allowing substrates to bind,

    • Triggered by low product concentration or high substrate concentration.

Page 29: Importance of Enzyme Regulation

  • Regulation via inhibitors and activators ensures enzymes function when needed:

    • Example: Digestive enzymes active when food is present to conserve energy.

Page 30: Questions to Reflect On

  • What, Who, Where, When, How, Why?