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.