Cellular Basis of Life Quiz

Cell Structure and Function

• The average-sized cell is one-fifth the size of the smallest dot made on a sheet of paper with a sharp pencil.
• Cells contain 60% of all water in the body.
• The cell is the fundamental unit of structure and function in living things.
• All organisms are made up of one or more cells.
• Cells arise from other cells through cellular division.

Cell Types

• Caulerpa taxifolia is the largest biological cell.
• Eukaryotes are characterized by having a true nucleus.
• Prokaryotic cells are smaller and simpler than eukaryotic cells, lacking membrane-bound organelles like a nucleus.

Cell Theory

• The cell theory was developed by Theodor Schwann, Matthias Schleiden, and Rudolf Virchow.
• Expanded cell theory includes:
  • Cells carry genetic material passed to daughter cells during cellular division.
  • All cells are essentially the same in chemical composition.
  • Energy flow (metabolism and biochemistry) occurs within cells.

Cell Functions

• Communication: Cells produce and receive chemical and electrical signals to communicate with each other.
• Reproduction and Inheritance:
  • Each cell contains a copy of the genetic information of the individual.
  • Specialized cells (sperm and oocytes) transmit genetic information to the next generation.
• Cell Metabolism and Energy Use:
  • Chemical reactions occur within cells, releasing energy used for cell activities.
  • Energy is used for heat production, synthesis of new molecules, and muscle contraction.
• Synthesis of Molecules:
  • Cells synthesize various molecules, including proteins, nucleic acids, and lipids.
  • Different cells produce different molecules, determining their structural and functional characteristics.

Eukaryotic Cell Structures

• Nucleus:
  • A spherical double membrane-bound organelle containing the genetic material.
  • Largest and most prominent cell organelle.
  • Composed of:
    • Nuclear membrane or Nuclear envelope
    • Chromatin threads or Chromosomes
    • Nuclear sap or Nucleoplasm
    • Nucleolus
• Centrioles:
  • Paired tube-like organelles composed of tubulin.
  • Found close to the nucleus and help in cell division.
  • Also found in cilia and flagella.
• Centrosomes:
  • Microtubule-organizing center of animal cells.
  • Composed of two centrioles linked together by interconnecting fibers.

Cell Organelles and Their Functions

• Lysosomes:
  • Small membrane-bound organelles filled with hydrolytic enzymes.
  • Break down biomolecules like carbohydrates, fats, and proteins.
• Peroxisomes:
  • Single membrane-bound cell organelle with digestive and oxidative enzymes.
  • Break down fatty acids to provide energy, perform lipid synthesis, and detoxify alcohol and other toxic compounds.
• Ribosome:
  • Minute particles present in large numbers, either attached to the endoplasmic reticulum or free in the cytosol.
  • Involved in protein synthesis.
• Cilia and Flagella:
  • Fine, hair-like projections that extend from the body of many cells.
  • Made of microtubules and vary in length and number based on cell type and function.
• Cell Membrane or Plasma Membrane:
  • Outermost membrane of an animal cell, separating the interior from outside.
  • Selectively permeable, consisting of a lipid bilayer with proteins, glycolipids, and cholesterol attached.
  • Materials are transported within vesicles to different locations in the cell.

Prokaryotic Cell Structure

• Capsule:
  • Outer protective covering found in bacterial cells.
  • Helps in moisture retention, protects the cell when engulfed, and aids in attachment to nutrients and surfaces.
• Cell Wall:
  • Outermost layer giving shape to the cell.
• Cytoplasm:
  • Gel-like component composed of enzymes, salts, and cell organelles.
• Cell Membrane:
  • Regulates the entry and exit of substances in the cells.
• Pili:
  • Hair-like outgrowths that attach to the surface of other bacterial cells.
• Flagella:
  • Long structures that help in locomotion.
• Ribosomes:
  • Involved in protein synthesis.
• Plasmids:
  • Non-chromosomal DNA structures.

Test your knowledge on the cellular basis of life including cell size, water content, cell types, cell theory, and modern cell theory. Learn about key concepts from famous scientists like Schwann, Schleiden, and Virchow.