Biochemistry Cell History Discussion

History of Cell Discovery

• Cells are fundamental units of life, discovered by Robert Hooke in 1665.
• Hooke observed cork under a microscope and identified small structures he named "cells."
• Due to limited magnification, Hooke believed these structures were non-living.
• Anton Van Leeuwenhoek later observed motility in cells, concluding they were alive and called them "animalcules."
• Robert Brown identified the nucleus in orchid cells in 1883, enhancing understanding of cell structure.

Cell Theory

• Proposed by Theodor Schwann, Matthias Schleiden, and Rudolf Virchow.
• States:
  • All living organisms are composed of cells.
  • The cell is the basic unit of life.
  • All cells arise from pre-existing cells.
• Modern cell theory includes:
  • Energy flows within cells.
  • Genetic information is transferred between cells.
  • All cells share a similar chemical composition.

Functions of Cells

• Cells provide support and structure, forming the basis of all organisms.
• Components like cell walls and membranes maintain this support.
• Hereditary material in cells can be DNA or RNA.
• Prokaryotic cells reproduce via binary fission and conjugation.
• Eukaryotic cells have a true nucleus and can reproduce sexually and asexually.

Prokaryotic vs Eukaryotic Cells

• Prokaryotic cells:
  • Lack a true nucleus.
  • Size: 0.1 to 0.5 µm.
  • Include archaea, bacteria, and cyanobacteria.
• Eukaryotic cells:
  • Contain a true nucleus, size ranging from 10 to 100 µm.
  • Include plants, fungi, protozoans, and animals.
  • Plasma membrane regulates nutrient transport and cell communication.

Cell Structure

• Comprised of components with specific functions essential for life processes:
  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Nucleus
  • Cell organelles

Cell Membrane

• Serves as the outer covering of the cell, supporting and protecting it.
• Controls movement of substances in and out, maintaining internal environment.
• Also referred to as the plasma membrane.

Cell Wall

• Not present in animal cells; found exclusively in plant cells.
• Composed of cellulose, hemicellulose, and pectin.
• Provides rigidity, shape, and mechanical protection to plant cells.

Cytoplasm

• Thick, clear, jelly-like substance where most chemical reactions occur.
• Contains organelles such as endoplasmic reticulum, vacuoles, and ribosomes.

Nucleus

• Contains hereditary material (DNA); sends signals for cell growth and division.
• Surrounded by the nuclear envelope, separating it from the cytoplasm.

Cell Organelles

• Golgi Bodies: Involved in the transportation of materials within the cell, often called the "post office" of the cell.
• Ribosomes: Synthesizers of proteins, crucial for cell function.
• Mitochondria: Known as the “powerhouse of the cell,” responsible for producing ATP, the cell's energy currency.
• Lysosomes: Protect the cell by digesting foreign bodies; often referred to as the cell’s "suicide bags."
• Chloroplasts: Involved in photosynthesis and contain chlorophyll, the pigment essential for capturing light energy.
• Vacuoles: Store food, water, and waste materials, playing a role in cell renewal.