Cells - Study Guide

Chapter 3: Cells - Study Guide

1. The 3 Major Parts of a Cell

• Plasma (Cell) Membrane

  • Function: Surrounds the cell, controls what enters and leaves.

• Cytoplasm

  • Description: Jelly-like fluid inside the cell.
  • Function: Holds organelles and is the site for many biochemical reactions.

• Nucleus

  • Function: Acts as the control center of the cell; houses the DNA.

2. Cell Membrane & Phospholipid Bilayer

• Description: Composed of two layers of phospholipids.
  • Phosphate Heads:
  • Characteristic: Hydrophilic (water-loving).
  • Fatty Acid Tails:
  • Characteristic: Hydrophobic (water-fearing).
• Importance: Functions as a selective barrier, maintains homeostasis within the cell.

3. Semipermeable (Selectively Permeable)

• Definition: The cell membrane allows some substances to pass while blocking others.
• Characteristics:
  • Small/nonpolar molecules can pass easily through the membrane.
  • Large or charged molecules require assistance to move across the membrane.

4. Organelles - Structure & Function

• Nucleus:

  • Function: Stores DNA and controls cell activities.

• Mitochondria:

  • Function: Produces ATP (energy currency of the cell).

• Ribosomes:

  • Function: Site of protein synthesis.

• Rough Endoplasmic Reticulum (Rough ER):

  • Function: Primarily involved in making proteins.

• Smooth Endoplasmic Reticulum (Smooth ER):

  • Function: Synthesizes lipids and detoxifies harmful substances.

• Golgi Apparatus:

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

• Lysosomes:

  • Function: Contains digestive enzymes for digestion and waste removal.

• Cytoskeleton:

  • Function: Provides structural support and is involved in cellular movement.

• Centrioles:

  • Function: Plays a crucial role in cell division, specifically in animal cells.

5. Nucleus: Structure & Function

• Nuclear Envelope:

  • Description: A double membrane that surrounds the nucleus; contains pores for transport.

• Nucleolus:

  • Function: Site for ribosome synthesis.

• Chromatin:

  • Description: Made up of DNA and proteins; organizes genetic material.

• Function of the Nucleus:

  • Directs protein synthesis and controls cell activities.

6. Transport Across the Cell Membrane

• Passive Transport (Does NOT require ATP; moves from high to low concentration):

  • Diffusion: Movement of molecules from an area of higher concentration to an area of lower concentration.
  • Facilitated Diffusion: Process where molecules pass across the membrane through cell membrane channels.
  • Osmosis: The diffusion of water across a selectively permeable membrane.

• Active Transport (Requires ATP; moves from low to high concentration):

  • Protein Pumps: Example includes the sodium-potassium pump, which moves sodium ions out of and potassium ions into the cell.
  • Endocytosis:
  • Sub-types:
    • Phagocytosis: Ingests solids.
    • Pinocytosis: Ingests liquids.
  • Exocytosis: Process where materials are released from the cell.

7. Mitosis

• Definition: The process of nuclear division that results in two identical nuclei.

• Purpose: Essential for growth, repair, and asexual reproduction.

• Interphase:

  • Description: The cell grows and prepares to divide.
  • Characteristics: DNA is replicated (copied); this is the longest phase of the cell cycle.

• Stages of Mitosis (PMAT):

  • Prophase: Chromosomes condense and become visible.
  • Metaphase: Chromosomes line up along the middle of the cell.
  • Anaphase: Separates sister chromatids towards the poles.
  • Telophase: Nuclei reform around the separated chromosomes.

• Cytokinesis: The division of the cytoplasm, resulting in two daughter cells.

Quick Study Tips

• Memorization:
  • Remember the acronym PMAT for the stages of mitosis.
• Categorization:
  • Group transport methods into active vs passive transport for easier understanding.
• Key Concepts:
  • Remember that mitochondria function as the powerhouse of the cell.
  • The Golgi apparatus is critical in shipping proteins.