Unit: Cell Structure & Function

Lecture #1 Life is Cellular & Common Features of cells

Why study Cells?

All Critical processes which take place in Living organisms take place in cells.

In the human body, cells are responsible for manythings including sight, hearing, smell, memory,pain and pleasure

In order to understand how living things performlife’s activities, it is essential to understand howthe cell functions.  

Question How did we first learn about cells?

Answer

Microscopes!

Early Microscopy

– It was not until the mid-1600s that scientists began to use microscopes to observe living things.

– Robert Hooke (1665) was n English scientist who used a crude microscope to look at a nonliving thin slice of cork, a plant material.

– Under the microscope, cork seemed to be made of thousands of tiny, empty chambers that Hooke called “cells”. The term cell is used in biology to this day.

– Today we know that living cells are not empty chambers, but contain a huge array of working parts, each with its own function.

Cork Cells

Anton van Leeuwenhoek - 1675

• Dutch scientist who used a microscope to view living organisms found in pond water.

• We know now that these are actually single celled organisms.

• He also looked at a sample taken from a human mouth.

• He drew the organisms he saw in the mouth—which today we call bacteria

It took scientists 150 years to fully appreciate the discoveries of Hooke and Leeuwenhoek.

Take two minutes to summarize what you havelearned about the history of cell discovery aswell as the importance of cell biology.

Discuss with your shoulder partner- • What do you understand well? • What is a little confusing?

Cell - The smallest unit that can perform all the life processes.  • It is the basic structural, functional, and

developmental unit of life.  • There are different types of cells within

an organism due to the fact that they are specialized for specific functions.

Example - We have about 250 different types of cells in our body; such as blood cells, muscle cells, epithelial (skin) cells, etc.

Types of Cells

The Cell Theory

Work contributions from other scientists eventually led to the Cell Theory.  The theory states:

1) All living things are made of one or more cells

2) Cells are the basic units of structure and function in organisms.

3) All cells arise from preexisting cells.

Cell Size

All cells need to take in substances such asnutrients, ions & oxygen & they need toRemove waste that builds up within the

cell.

The only way in or out is for substances toPass through the cells surface (cellmembrane).

Question: Cells are SMALL. Why is thisimportant?

Answer• Small cells exchange substances must

more rapidly because substances do not need to travel as far to reach the center of a smaller cell.

 • Small cells have a surface-area to

volume ratio that is HIGHER than large cells.

•  This is why it is better for us to have so many tiny cells instead of a few large ones.

Take two minutes to summarize what you havelearned about cell theory, and the reasons why SMALL SIZE such an important feature of cells.

Discuss with your shoulder partner- • What do you understand well? • What is a little confusing?

Types of Cells

– Cells fall into two broad categories, depending on whether they contain a nucleus.

– The nucleus is a large membrane-enclosed structure that contains the cell’s genetic material in the form of DNA.

• Function- the nucleus controls many of the cell’s activities.

Prokaryotes and Eukaryotes

– Eukaryotes are cells that enclose their DNA in nuclei. * Plural for nucleus

– Prokaryotes are cells that do not enclose DNA in nuclei.

Prokaryotic Cells

– Prokaryotic cells are generally smaller and simpler than eukaryotic cells.

– Because they are such simple cells, they cannot carry out many specialized functions.

Prokaryotes were the first life form on earth.

• They lived at least 3.5 billion years ago.  • For nearly 2 billion years, prokaryotes

were the only organisms on Earth! – Single celled organisms. The organisms

we call bacteria are modern day prokaryotes

Eukaryotes

– Eukaryotic cells are generally larger and more complex than prokaryotic cells.

– Most eukaryotic cells contain dozens of structures and internal membranes. Many eukaryotes are highly specialized.

– There are many types of eukaryotes: plants, animals, fungi, and organisms commonly called “protists.”

Take two minutes to summarize what you havelearned about the two categories of cells as wellas their characteristics.

Discuss with your shoulder partner- • What do you understand well? • What is a little confusing?