Chapter 7, Problem 8A

Summary Introduction

To compare and contrast:

Prokaryotic and eukaryotic cells

Introduction : Robert Hooke was the first one to use the term ‘cell’. A cell is the structural and functional unit of all living organisms. Cells exist in all shapes and sizes. They differ in the kind of function they perform for the organism.

Answer to Problem 8A

The following table summarizes the differences between a prokaryotic cell and a eukaryotic cell.

Prokaryotic cell	Eukaryotic cell
It does not have a well- defined nucleus.	It has a well- defined nucleus.
It has a thick cell wall.	Only plant cells have cell walls. Animal cells do not have cell wall.
Membrane bound cell organelles are absent.	Membrane bound cell organelles are present.
DNA is circular.	DNA is thread like and linear.
Very small in size.	Much larger in size.
Cytoskeleton absent	Cytoskeleton present
Example: bacteria	Example: humans

Explanation of Solution

There are two categories of cells; those that have membrane- bound organelles like mitochondria, chloroplast, Golgi bodies and those without membrane- bound organelles. Cells with membrane -bound organelles are called eukaryotes and those without membrane- bound organelles are called prokaryotes.

Prokaryotes do not have a nucleus. The nuclear material is called nucleoid. It is not surrounded by a nuclear membrane and does not contain nucleolus. Eukaryotes have a well- defined nucleus with nucleolus. The DNA is circular in prokaryotes and linear in eukaryotes.

Cell wall is prominent in prokaryotes. Among eukaryotes, only plant cells have cell wall. Animal cells are without cell walls. However, plasma membrane is present in both prokaryotes and eukaryotes.

Prokaryotes are very minute in size. Eukaryotic cells are one to one hundred times larger than prokaryotes.

Most cells are eukaryotes. E.g multicellular organisms have eukaryotic cells. Unicellular organisms like bacteria are prokaryotes.

Prokaryotes are believed to be the first organisms on Earth. Eukaryotic cells might have evolved from prokaryotic cells millions of years ago. This has led to cell diversity and thus more diverse group of organisms have evolved over time.