Cell Biology Overview

Cell Composition

• Cells are primarily composed of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).
• Cells are the fundamental units of life.

Cell Theory

• Robert Hooke first observed cells in 1665.
• The cell theory proposes that all living things are made of cells and that cells originate from prior existing cells.

Cell Size and Shape

• Cell size is limited by its membrane.
• Cell shape reflects its function.
• Cells are categorized as prokaryotic (lack a nucleus) or eukaryotic (have a nucleus).

Cell Organelles

• Organelles vary in their structure and function depending on the cell's role.
• Cells have membranes to regulate what enters and exits.

Cell Membrane

• Cell membranes are composed of a phospholipid bilayer.
• The hydrophilic heads of the phospholipids face outward, and the hydrophobic tails face inward.
• Integral and peripheral proteins are embedded within the membrane.
• Cholesterol is a steroid also found within the bilayer.
• The membrane's protein patterns are dynamic, known as the fluid-mosaic model.

Microscopes

• Light microscopes magnify objects up to 1000x, requiring that the object be thin or cut thin enough for light to pass through.
• Electron microscopes use beams of electrons to magnify objects more greatly. Transmission electron microscopes (TEM) examine thin sections of the object while scanning electron microscopes (SEM) examine the surface of a specimen. False color is often added to improve visibility.

Cellular Homeostasis

• Single-celled organisms maintain stable internal conditions (homeostasis).
• Multicellular organisms divide labor among cells through specialization.

Cellular Communication

• Cells in multicellular organisms communicate using receptors.

Cell Transport

• Passive transport moves substances across the membrane with no energy input, down a concentration gradient. Examples are diffusion, osmosis, and facilitated diffusion.
• Active transport moves substances against their concentration gradient requiring energy. Examples are the sodium-potassium pump and bulk transport (endocytosis and exocytosis).

Osmosis and Solutions

• Cells respond to different solutions (hypertonic, hypotonic, and isotonic).
• Hypertonic solutions cause water to leave the cell, potentially shrinking it or leading to plasmolysis.
• Hypotonic solutions cause water to enter the cell, potentially causing it to swell or resulting in cytolysis.
• Isotonic solutions maintain equilibrium.

Discover the fundamental aspects of cell biology through this quiz. Explore cell composition, the cell theory, various organelles, and the structure of cell membranes. Test your understanding and learn about the essential units of life.