Biol 103: Introductory Biology I - Lecture 3 Cells
Cell Biology Introduction - Biol 103: Introductory Biology I, Lecture 3 Cells.
Learning Objectives
Describe cell observation methods.
Identify basic cell function and structure.
Explain why cells are small.
List differences between eukaryotes and prokaryotes.
Describe organelle functions.
History of Cell Observation
Robert Hooke (1635-1703): First observed and named cells in 1665 after looking at cork tissue under a microscope. He called them "cells" because they reminded him of the small rooms monks lived in.
Antonie van Leeuwenhoek (1632-1723): Developed more powerful microscopes and was the first to observe live cells, including bacteria and protists, which he called "animalcules" (little animals).
Cell Theory
All living organisms are composed of one or more cells.
The cell is the basic unit of structure and organization in organisms.
All cells arise from pre-existing cells.
Cell Observation Methods
Light Microscopy: Uses visible light to magnify samples. Can observe living cells and general cell structures.
Electron Microscopy: Uses beams of electrons to achieve much higher magnification and resolution. Provides detailed views of organelles and cellular ultrastructure. Cells must be non-living and specially prepared.
Transmission Electron Microscope (TEM): Used to view internal structures of cells.
Scanning Electron Microscope (SEM): Used to view the surface topography of cells and tissues.
Basic Cell Functions and Structure
Cells are the fundamental units of life, carrying out all necessary biological processes.
All cells share common features:
Plasma Membrane: Outer boundary, controls passage of substances.
Cytoplasm: Jelly-like substance filling the cell, where organelles are suspended.
Genetic Material: DNA which contains instructions for cell function.
Ribosomes: Structures responsible for protein synthesis.
Why Cells Are Small
Cells remain small to maintain an efficient surface area to volume ratio.
As a cell grows, its volume increases faster than its surface area. (Volume \propto r^3, Surface \ Area \propto r^2)
A larger surface area allows for efficient exchange of nutrients and waste products with the environment.
If cells were too large, the surface area would not be sufficient to meet the metabolic demands of the increased volume, leading to inefficient transport and cellular processes.