Cellular organelles

Cellular Organelles - Dr. Lucia Celkova

Page 2: Teaching Objectives

• Explain what a cell is

  • Historical perspective

  • Common features of cells

  • Main cell types

• Describe structure and function of the plasma membrane

• Detail structure and function of key cellular organelles

  • Organelles and their dysfunction

Page 3: Definition of a Cell

• Basic Unit of Life

  • Simplest collection of matter that can live

  • Hierarchical organization: Cells → Tissues → Organs

• Examples

  • Amoeba: a single-celled organism

  • A single human cell

Page 4: Discovery of Cells

• Robert Hooke (1665)

  • Used a compound microscope to observe cork

  • Discovered box-like structures he termed "cells"

• Significance

  • First observation of microscopic pores

Page 5: Antonie van Leeuwenhoek

• Contributions

  • Master microscope maker with 200-300x magnification

  • Discovered bacteria, protozoa, and other cells

  • Coined the term "animalcules" for small living organisms

Page 6: Cell Theory

• Theorists

  • Theodore Schwann and Matthias Schleiden

  • Rudolf Virchow (Robert Remak)

• Key Principles

  1. All living organisms are composed of one or more cells.

  2. The cell is the basic unit of structure and organization in organisms.

  3. Cells arise from pre-existing cells.

Page 7: Cell Diversity

• Examples of Cell Types

  • Gallbladder epithelial cells

  • Fat cells

  • Nerve cells

  • Macrophages

  • Skin cells

  • Red and white blood cells

Page 8: Common Features of Cells

• Shared Characteristics

  • Bound by a plasma membrane

  • Contain chromosomes made from DNA

  • Have ribosomes for protein synthesis

Page 9: Cytoplasm

• Definition

  • Region between the cell membrane and nucleus

  • Contains cytosol and organelles

• Plasma Membrane

  • Separates living cell from non-living surroundings

Page 10: Types of Cells

• Prokaryotic Cells

  • Unicellular, less organized, no membrane-bound DNA

• Eukaryotic Cells

  • Multicellular, more organized, internal membranes

Page 11: Plasma Membrane

• Functions

  • Keeps the cell intact

  • Exhibits selective permeability for nutrients and waste

Page 12: Membrane Structure

• Phospholipid Bilayer

  • Asymmetric structure with embedded proteins and carbohydrates

Page 13: Phospholipids

• Characteristics

  • Amphipathic molecules with hydrophilic heads and hydrophobic tails

Page 14: Phospholipid Bilayer

• Structure

  • Two layers of phospholipids providing separation and interaction with environments

Page 15: Membrane Fluidity

• Asymmetry and Movement

  • Different lipid types in membrane regions

  • Rapid lateral movement, slow flip-flop

Page 16: Lipid Composition

• Fluidity Factors

  • Saturated vs. Unsaturated fatty acids affect membrane fluidity

Page 17: Cholesterol and Other Lipids

• Cholesterol

  • Reduces fluidity at high temperatures, hinders solidification at low temperatures

• Sphingolipids and Ceramides

  • Important in neural tissues

Page 18: Membrane Proteins

• Types

  1. Integral proteins: penetrate the membrane

  2. Peripheral proteins: loosely attached to the membrane surface

Page 19: Organelles Overview

• Definition

  • Intracellular compartments performing specific functions

Page 20: Origin of Organelles

• Maternal Contribution

  • All organelles derived from the mother during zygote formation

Page 21: Types of Organelles

• Membranous Organelles

  • Nucleus, ER, mitochondria, Golgi apparatus, lysosomes, peroxisomes

• Non-Membranous Organelles

  • Ribosomes, cytoskeletal structures

Page 22: Nucleus

• Main Function

  • Storage of genetic information (DNA) and gene expression

Page 23: Nuclear Envelope

• Structure

  • Double lipid bilayer protecting DNA with nuclear pores for material exchange

Page 24: Chromosomes

• Composition

  • Dynamic assemblies of DNA and proteins (chromatin)

Page 25: DNA Packing

• Nucleosomes

  • Basic structural unit of chromatin, tightly bound to histones

Page 26: Chromatin Structure

• Condensation

  • Coiling into fibers for efficient DNA packing

Page 27: Nucleolus

• Function

  • Ribosomal RNA gene transcription and ribosome assembly

Page 28: Endoplasmic Reticulum

• Structure

  • Network of membrane-enclosed sacs (cisternae)

• Types

  • Rough ER (rER) and Smooth ER (sER)

Page 29: Rough Endoplasmic Reticulum

• Function

  • Major site for protein synthesis and trafficking

Page 30: Smooth Endoplasmic Reticulum

• Functions

  • Lipid synthesis, carbohydrate metabolism, calcium storage

Page 31: Golgi Apparatus

• Structure

  • Stacked, membrane-bound sacs for processing and packaging macromolecules

Page 32: Mitochondria

• Structure

  • Double membrane-bound organelles with specialized compartments

Page 33: Mitochondrial Genome

• Composition

  • Circular DNA with genes for mitochondrial function

Page 34: Mitochondrial Function

• Roles

  • Energy production, calcium storage, apoptosis regulation

Page 35: Lysosomes

• Function

  • Waste disposal system with digestive enzymes

Page 36: Peroxisomes

• Function

  • Recycling and detoxification with oxidative enzymes

Page 37: Lysosomal Dysfunction

• Lysosomal Storage Diseases

  • Rare inherited disorders due to enzyme mutations, leading to substrate accumulation

Page 38: Mitochondrial Dysfunction

• Mitochondrial Diseases

  • Genetic defects affecting energy production and linked to aging

Page 39: Summary of Learning

• Key Takeaways

  • Cells as basic units of life

  • Structure of plasma membrane

  • Functions of cellular organelles

• Further Reading

  • Campbell and Reece: Biology

  • Alberts et al.: Molecular Biology of the Cell

• Contact

  • Email: celkoval@tcd.ie for questions