Ch 4-BIOL201- Organization of the cell

Chapter 4: Organization of the Cell

A. Introduction

  • Cell Theory:

    • All organisms are made up of cells.

    • A cell is the smallest unit of living matter.

    • Organisms can be unicellular or multicellular.

    • Cells are the structural and functional units of all organisms.

B. Viruses

  • Characteristics of Viruses:

    • Not alive, not classified as cells.

    • Depend on cells for existence.

    • Composed of a protein capsid containing nucleic acid (DNA or RNA).

C. Cell Size

  • Nutrient and waste exchange is through the cell surface.

  • Large cells demand more nutrients and produce greater waste, limiting their size.

  • Extensions on the cell surface can increase absorption capacity.

D. General Components of Cells

  1. Cell Membrane

  2. Nucleus (or Nucleoid in Prokaryotes)

  3. Cytoplasm:

  • Cytosol: Semi-liquid medium.

  • Inclusions: Organelles in eukaryotic cells.

E. Types of Cells

  • Prokaryotic Cells:

    • Lack a membrane-bounded nucleus and organelles.

    • Bacteria belong to the kingdom Prokaryotae.

  • Eukaryotic Cells:

    • Have a membrane-bounded nucleus and organelles.

F. Cell Structure Reflects Function

  • Cellular structures are adapted for specific functions:

    • Neurons have axons for information transfer.

    • Sperm have tails for swimming.

    • Eggs possess nutrients for early development.

G. Prokaryotic Cells

  • Characteristics:

    • Size: 1-10 µm.

    • Structure: Peptidoglycan cell wall, plasmids, and nucleoid region.

    • Motility: Flagella and fimbria (pili) for attachment.

H. Distinguishing Features of Cell Types

  • Prokaryotes vs. Eukaryotes:

    • No nucleus vs. true nucleus.

    • Smaller size vs. larger size.

    • Few internal membranes vs. many.

    • Different types of ribosomes (70S vs. 80S).

I. Eukaryotic Cells

  • Size: 10-100 times larger than prokaryotes.

  • Contains membrane-bounded organelles and a nucleus.

  • Plants have a cell wall made of cellulose.

J. Organelles in Eukaryotic Cells

  1. Nucleus:

  • Stores genetic information as DNA.

  • Contains nucleoli which form ribosomes.

  1. Ribosomes:

  • RNA and protein complexes involved in protein synthesis.

  • Found in prokaryotes and eukaryotes.

  1. Endoplasmic Reticulum (ER):

  • Complicated network of membranous channels.

  • Types:

    • Rough ER: Synthesizes and processes proteins.

    • Smooth ER: Lipid synthesis, detoxification, storage.

  1. Golgi Apparatus:

  • Modifies and packages proteins; forms vesicles.

  1. Lysosomes:

  • Contain digestive enzymes; formed by Golgi.

  1. Microbodies:

  • Includes peroxisomes and glyoxysomes for metabolism.

  1. Vacuoles:

  • Storage structures, larger in plant cells.

  1. Energy-Related Organelles:

  • Chloroplasts: Photosynthesis.

  • Mitochondria: ATP production through cellular respiration.

K. The Cytoskeleton

  • A network of filaments providing structure and transport within the cell.

  • Components:

    • Microfilaments (Actin), Microtubules (Tubulin), Intermediate filaments.

L. Extracellular Matrix (ECM)

  • Comprises proteins and carbohydrates outside of the cell.

  • In animal cells, consists of collagen and fibronectin.

  • Plant cells have a cellulose cell wall.

M. How to Study Cells

  1. Microscopy:

  • Early microscopes introduced by Hooke and van Leeuwenhoek.

  1. Types of Microscopes:

  • Stereo, Brightfield, Phase Contrast, Fluorescence, Electron Microscopes.

  1. Biochemical Tools:

  • Centrifugation techniques for separating cellular components.