Cell theory – types of cells CELLS – the basic unit of life!

I. Basic HISTORY: Every living thing-from the tiniest bacterium to the largest whale-are made of one or more cells! Before the seventeenth century, no one knew that CELLS existed.

I. Basic HISTORY: Most cells are too small to be seen with the unaided eye. Not discovered until after the invention of the microscope in the early 17th century.

II. IMPORTANT SCIENTISTS: A Dutch drapery storeowner Anton von Leewenhoek, became the FIRST person to OBSERVE and DESCRIBE MICROSCOPIC ORGANISMS and LIVING CELLS.

II. IMPORTANT SCIENTISTS: 1665: the English Scientist Robert Hooke used a microscope to examine a thin slice of cork and described it as consisting of "a great many little boxes".  It was after his observation that Hooke called what he saw "cells". They looked like "little boxes" and reminded him of the small rooms in which monks lived. So he called them "cells".

Illustration of cork drawn by Robert Hooke:

III. The Cell Theory Consists of 3 Principles: All living things are composed of one or more cells. Cells are the basic units of structure and function in an organism. Cells come only from the reproduction of existing cells.

IV. TWO TYPES of CELLS: 1. EUKARYOTES = cell that contain a nucleus and other membrane- bound organelles ~Ex: plants, fish, mammals, insects and humans

IV. TWO TYPES of CELLS: 2. PROKARYOTES = cell that lacks a nucleus and other membrane- bound organelles. ~Ex: unicellular organisms such as bacteria and their relatives

V. CELL DIVERSITY: Not all cells are alike. Cells within the same organism show enormous diversity in size, shape, and internal organization.  Your body contains at least 200 different cell types!

VI. CELL SIZE: A few types of cells are large enough to be seen by the unaided eye.  Female egg is the largest cell in the body, and can be seen without the aid of a microscope. Most cells are visible only with a microscope.

VI. CELL SIZE: Most cells are small for 2 reasons: 1. Cells are limited in size by the RATIO between their outer surface area and their volume.  As a cell’s size increases, its volume increases much faster than its surface area.  (see picture on the next slide!)

VI. CELL SIZE: 2. The cell’s nucleus (the brain) can only control a certain amount of living, active cytoplasm.

VII. CELL SHAPE: Variety of shapes. The shape of the cell depends on its function

VII. CELL SHAPE: Ex: Nerve cells that carry information from your toes to your brain are long and threadlike. Ex: Blood cells are shaped like round disk that can squeeze through tiny blood vessels

VIII. CELLULAR ORGANIZATION: Multicellular organisms are made up of many cells, each of which is specialized to perform a distinct function. Digestion, movement, respiration, filtering, etc… Individual cells DO NOT carry out ALL life functions, but rather depend on each other

Study the organelles!