Biology Chapter 1: Cell Characteristics

Basic Characteristics of Cells

• Cells store hereditary information, reproduce, acquire and utilize energy, and are sites for various biochemical reactions.
• They are capable of responding to stimuli.

Cell Discovery

• Robert Hooke examined cork and identified "cells," which are dead plant cells.
• Anton Van Leeuwenhoek improved microscope design and observed the first living cells, termed "animalcules."

Cell Theory

• Formulated by Schleiden and Schwann, modified by Rudolf Virchow, stating:
  • All living organisms are made up of one or more cells.
  • The cell is the basic structural and functional unit of life.
  • All cells arise from pre-existing cells.

Microscopes

• Instruments designed to magnify small objects, revealing details invisible to the naked eye.

Simple Microscope

• Consists of a single lens with magnification limited to one lens.

Compound Microscope

• Utilizes multiple lenses; total magnification is the product of objective and eyepiece lenses.

Types of Cells

• Cells are categorized into two main groups based on complexity.

Components of a Eukaryotic Cell

• Nucleus: Contains DNA organized into chromosomes; controls growth and metabolism; surrounded by a nuclear envelope.
• Cytoplasm: Jelly-like substance within the cell membrane, mainly comprised of water, salts, proteins, and organelles; site of most biochemical reactions.
• Cell Membrane: Flexible and selectively permeable; outermost layer enclosing the cell.

Cell Membrane

• Composed of phospholipid bilayer and embedded proteins.
• Functions include enclosing cell components and regulating substance passage.

Permeability

• Types of membranes:
  • Impermeable: No particles pass.
  • Selectively permeable: Specific molecules can cross.
  • Freely permeable: All molecules can cross without resistance.

Types of Transport

• Active Transport: Movement against the concentration gradient using cellular energy (ATP).
• Passive Transport: Movement down the concentration gradient without energy expenditure.

Cell Wall

• Plant Cells: Outermost layer providing rigidity, composed of cellulose.
• Other Organisms:
  • Fungi: Made of chitin.
  • Algae: Consist of cellulose.
  • Bacteria: Comprised of peptidoglycan.

Cells in Different Solutions

• Hypotonic Solution: Higher water concentration outside; cells gain water.
• Hypertonic Solution: Lower water concentration outside; cells lose water.
• Isotonic Solution: Equal water concentration; no net movement of water.

Cell Organelles

• Organelles: Subcellular structures with specific functions.

Endoplasmic Reticulum (ER)

• Rough ER: Ribosomes attached; synthesizes proteins and enzymes.
• Smooth ER: No ribosomes; synthesizes lipids and steroids.

Golgi Body

• Composed of membrane-bound sacs (cisternae); packages and transports materials synthesized in the cell.

Mitochondria

• Double-membrane organelle with its own DNA; site of ATP production.

Chloroplasts

• Present in higher plants; contains thylakoids and stroma for photosynthesis.

Cell Division

Mitosis

• Occurs in somatic cells; results in two diploid daughter cells; chromosome number remains the same.

Meiosis

• Occurs in germ cells; results in four haploid daughter cells; chromosome number is halved after two nuclear divisions.

Explore the fundamental characteristics of cells in this quiz. Learn about the functions and roles of a typical animal cell, including energy acquisition, reproduction, and response to stimuli. Test your understanding of cell discovery and its importance in biology.