Cytology Study Notes

Cytology Overview

  • All living things are composed of cells.

Brief History of Cells and Microscopy

  • 17th century: Anton van Leeuwenhoek invented microscopy.

  • Robert Hooke observed cork and named "cells" after monk's rooms.

  • 1830s: Schleiden & Schwann established the cell theory:

    1. All organisms are made of cells.

    2. The cell is the basic unit of life.

    3. All cells arise from pre-existing cells.

Cell Types

  • Prokaryotic Cells: No nucleus, unbound DNA (nucleoid), no membrane-bound organelles.

  • Eukaryotic Cells: DNA in a membrane-bound nucleus, membrane-bound organelles, generally larger.

Cell Structures

  • Basic features of all cells:

    • Plasma membrane

    • Cytoplasm

    • Chromosomes

    • Ribosomes

Eukaryotic Cell Types

  • Animal cells

  • Plant cells

Plasma Membrane

  • Selective barrier for substances like oxygen and nutrients; composed of lipids and proteins.

Cytoplasm/Cytosol

  • Jelly-like interior of cells; distinguishes between cytosol (fluid) and cytoplasm (fluid + organelles).

Nucleus

  • Contains DNA; double membrane with pores regulating molecular entry/exit, housing chromatin and nucleolus.

Ribosomes

  • Sites of protein synthesis; exist in cytosol (free) or attached to endoplasmic reticulum (bound).

Endomembrane System

  • Regulates protein traffic; includes:

    • Nuclear envelope

    • Endoplasmic reticulum

    • Golgi apparatus

    • Lysosomes

    • Vacuoles

    • Plasma membrane

Mitochondria and Chloroplasts

  • Mitochondria: Cellular respiration, producing ATP.

  • Chloroplasts: Photosynthesis; contain chlorophyll.

  • Both have double membranes, contain DNA, and are not part of the endomembrane system (supports Endosymbiotic Theory).

Cellular Reproduction

  • Unicellular organisms (bacteria, protists) reproduce via binary fission, budding, likeness.

  • Multicellular organisms undergo mitosis and meiosis for growth and reproduction, allowing for genetic diversity.

Energy Acquisition

  • Autotrophic: Self-feeding organisms (photosynthesis).

  • Heterotrophic: Consume other living things for nutrients.

Response to Environment

  • Homeostasis maintains stable internal conditions.

  • Organisms respond to stimuli to keep life-sustaining conditions.

Organelles Overview

  • Nucleus

    • Contains DNA; double membrane with pores regulating the entry/exit of molecules; houses chromatin (DNA and proteins) and the nucleolus.

  • Ribosomes

    • Sites of protein synthesis; they exist in two forms: free ribosomes in the cytosol and bound ribosomes attached to the endoplasmic reticulum.

  • Endoplasmic Reticulum (ER)

    • Composed of rough ER (with ribosomes for protein synthesis) and smooth ER (involved in lipid synthesis and detoxification).

  • Golgi Apparatus

    • Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.

  • Lysosomes

    • Contains enzymes for digestion; breaks down waste materials and cellular debris.

  • Vacuoles

    • Storage organelles; larger in plant cells, they store nutrients, waste products, and help maintain turgor pressure.

  • Mitochondria

    • Sites of cellular respiration; they produce ATP. They have double membranes and their own DNA.

  • Chloroplasts

    • Organelles for photosynthesis, containing chlorophyll. They also have double membranes and their own DNA.

  • Plasma Membrane

    • Selective barrier for substances like oxygen and nutrients; composed of lipids and proteins.

Additional Context

Mitochondria and chloroplasts are not part of the endomembrane system and support the Endosymbiotic Theory, which suggests they originated from free-living bacteria. They both contain their own DNA and have double membranes, demonstrating a unique evolutionary path.