Unit: Cell Structure & Function Lecture #1 Life is Cellular

Why study Cells? All Critical processes which take place in Living organisms take place in cells. In the human body, cells are responsible for many things including sight, hearing, smell, memory, pain and pleasure In order to understand how living things perform life’s activities, it is essential to understand how the 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 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.

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 as nutrients, ions & oxygen & they need to Remove waste that builds up within the cell. The only way in or out is for substances to Pass through the cells surface (cell membrane). Question: Cells are SMALL. Why is this important?

Answer Small cells exchange substances much 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 have learned 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 have learned about the two categories of cells as well as their characteristics. Discuss with your shoulder partner- What do you understand well? What is a little confusing?

Unit 2: Cell Structure & Function Lecture #2 5 Common features of ALL Cells

1. Cell Membrane (plasma membrane) What is it? A semipermeable barrier that encloses the cell and separates the cell interior from its surroundings. It also regulates what enters and leaves a cell ( gases, nutrients, wastes, etc)

2. Cytoplasm What is it? Semitransparent fluid (mostly water) that provides a liquid environment for cell activities. Many structures necessary for cell function are found suspended in the cells cytoplasm.

3. Cytoskeleton What is it? A system ( web) of microscopic protein fibers found inside cytoplasm. This is what suspends the structures of the cell found within the cytoplasm. This holds the cell together and prevents it from collapsing or folding.

Two types of fibers make up the cytoskeleton 1.Microtubules - long hollow tubes that extend throughout the cytoplasm, supporting the cell. 2. Microfilaments - extremely thin protein strands that also support cell shape and structure. They may also help in moving organelles around the cell.

4. Ribosomes What is it? Cellular structures on which proteins are made. AKA the ‘protein factory’

Tying it all together……. Remember from Unit 1 DNA is like a cookbook, with 30,000 recipes. Each recipe is a gene. Each gene codes for the production of a particular protein. The recipe is delivered to the ribosome by DNA’s helper, RNA. The proteins is then built on the ribosome.

5. DNA All cells have DNA. Remember, this is one of the 8 characteristics of life that we learned about last unit. DNA serves three important functions 1.It provides instructions for making proteins 2.Regulates cellular activities 3.Enables cells to reproduce