Cell Theory and Cell Structures Study Guide

The Cell Theory

Three Parts of the Cell Theory

1. All living things are made of cells.

   • This establishes that every organism, whether unicellular or multicellular, consists of cells which serve as the foundational building blocks of life.

2. Cells are the basic unit of structure and function.

   • Cells not only provide structure to the organisms but also facilitate functions that are vital for life, such as metabolism, energy production, and reproduction.

3. All cells come from other cells.

   • This principle emphasizes the continuity of life, indicating that new cells arise from the division of pre-existing cells rather than spontaneously arising.

Structures in All Cells

Four Structures Found in All Cells

1. Cell Membrane

   • Function: Regulates the passage of substances in and out of the cell, providing a barrier between the cell’s interior and exterior environment.

2. Ribosomes

   • Function: Synthesizes proteins by translating messenger RNA.

3. DNA

   • Function: Contains the genetic instructions that direct cell growth, development, and function.

4. Cytoplasm

   • Function: The jelly-like fluid that fills the cell, allowing for the movement of materials and hosting organelles.

Comparing and Contrasting Types of Cells

Table of Cell Structures by Cell Type

Classification of Organisms based on Cell Type

Prokaryotic Organisms

• Examples:

  • Bacteria

  • Archaea

Eukaryotic Organisms

• Examples:

  • Animalia (Animals)

  • Plantae (Plants)

  • Protista (Protists)

  • Fungi

Bacteria: Good and Bad Aspects

1. Good

   • Function: Aids in digestion.

   • Example: Certain bacteria can efficiently break down carbohydrates in food, enhancing nutrient absorption.

2. Bad

   • Function: Produce toxic substances that can lead to illness.

   • Example: Lyme disease is caused by bacteria that can result in serious health complications.

Types of Cells and Their Structures

A) Prokaryotic Cell (Bacteria)

• Structures:

  1. Flagella

  2. Pili

  3. DNA

  4. Cell Membrane

  5. Ribosomes

  6. Cytoplasm

  7. Capsule

  8. Cell Wall

B) Animal Cell (Eukaryotic)

• Structures:

  • Ribosomes

  • Lysosomes

  • Golgi Apparatus

  • Nucleus

  • Cell Membrane

  • Endoplasmic Reticulum (ER) (Rough with ribosomes)

  • Mitochondria

  • Cytoplasm

C) Plant Cell (Eukaryotic)

• Structures:

  • Ribosomes

  • Chloroplast

  • Golgi Apparatus

  • Nucleus

  • Cell Membrane

  • Endoplasmic Reticulum (ER) (Rough with ribosomes)

  • Mitochondria

  • Cytoplasm

  • Cell Wall

  • Vacuole

Energy Production in Prokaryotic Organisms

1. Autotrophs

   • Function: Produce their own food through processes like photosynthesis or chemosynthesis.

2. Heterotrophs

   • Function: Obtain energy by consuming other organisms, as they cannot synthesize their own food.

Asexual Reproduction in Prokaryotic Cells

• Mode of Reproduction: Binary fission

  • Description: A fast and efficient process where a single cell divides into two identical daughter cells, each making a copy of the original cell's genetic material.

Structure and Function of Organelles

1. Cell Membrane

   • Function: Selectively permeable barrier that monitors and controls the internal environment of the cell.

2. Ribosome

   • Function: Site of protein synthesis, translating messenger RNA into polypeptides.

3. Cytoplasm

   • Function: A viscous fluid that contains organic and inorganic substances that are vital for cellular activities.

4. Mitochondria

   • Function: Site of cellular respiration where ATP (adenosine triphosphate), the energy currency of the cell, is produced.

5. Lysosome

   • Function: Contains digestive enzymes to break down waste materials and cellular debris for recycling.

6. Nucleus

   • Function: Acts as the control center of the cell, containing the majority of the cell's genetic material.

7. Cell Wall

   • Function: Provides shape, support, and protection to the cell.

8. Chloroplast

   • Function: Conducts photosynthesis, converting sunlight into glucose and oxygen.

9. Golgi Apparatus

   • Function: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

10. Rough Endoplasmic Reticulum (ER)

    • Function: Studded with ribosomes, it synthesizes proteins and processes them for secretion.

11. Smooth Endoplasmic Reticulum (ER)

    • Function: Synthesizes lipids and detoxifies substances.

The Endomembrane System

1. Definition:

   • A group of organelles that work collaboratively to produce and transport proteins and lipids out of the cell.

2. Organelle Involvement in Endomembrane System:

   • The sequence is as follows:

     • Nucleus → Rough ER → Golgi Apparatus → Transport Vesicle → Cell Membrane or Lysosome.

Viruses

Evidence that Viruses are NOT Considered Living

1. Not a Cell:

   • Viruses do not possess the cellular structure characteristic of living organisms.

2. Cannot Reproduce Independently:

   • Viruses require a host cell to reproduce and cannot proliferate on their own.

3. Do Not Maintain Homeostasis:

   • Viruses lack the ability to internally regulate their environment, which is a hallmark of living entities.