Unit 3

Cells and their Structure

Levels of Organization

Diversity of Cellular Life

Cell Specialization – when a group of cells work together to perform a specific job

The Cell Theory

• All living things are composed of cells

• Basic units of structure and function in living things

• Cells are produced from existing cells

Categories of CellsType 1 Prokaryotes

• Unicellular – one cell• No Nucleus – DNA

free floating• Example – Bacteria• Used in technique

called Recombinant DNA

Shapes of Prokaryotes• Cocci =

spherical (round)

• Bacillus = (rod shaped)

• Spirilla = helical (spiral)

These are prokaryote E. coli bacteria on the head of a steel pin.

What the heck is RecombinantDNA?

Recombinant DNA is what you get whenyou combine DNA from two different

sources.For example:

Mouse + Human DNAHuman + Bacterial DNAViral + Bacterial DNA

Human + (other) Human DNA

Why Make Recombinant DNA?Recombinant DNA Technology May

Allow Us To:• Cure or treat disease• Genetically modify our foods to increaseflavor, yield, nutritional value or shelf-life• Better understand human genetics• Clone cells or organs

Molecular Biology’s Best Friends: Bacteria

Why use bacteria?• They’re relatively simple organisms.• They reproduce very quickly and asexually (this means that the “daughter” cells will contain the exact same DNA as the “parent” cell).• It’s pretty easy to get DNA back into the bacteria after you’ve changed it.

Recombinant DNAThe foreign DNA is first joined to a small,

circular DNA molecule found in bacteria known as a plasmid.

Restriction enzymes

• A restriction enzyme (RE) is a specialized protein that cuts DNA in a very specific place.

• Molecular scissors

Step to Recombinant DNA

Steps to Recombinant DNAStep 1:

•Isolate (find) the human gene responsible for producing insulin and decide where you want to put it.•In this case, we decide to put our human DNA into the plasmid of E. coli, a very common bacterium.

Step 2:•Get the bacterial (plasmid) DNA out of the E. coli. We do this by basicallyexploding them.

Step 3:•Cut your human DNA and bacterial DNA with the same restriction enzyme

Step 4:•Mix the cut human DNA, which contains the insulin gene, with the cut bacterial DNA.•They’ll stick together because they were cut with the same restriction enzyme.

Step 5:Get your new recombinantplasmid back into the bacteria.This is easy because bacteria will take in DNA that’s floating around near them. We call this “transformation”.

Voila!!Now your E. coli will use its new DNAto make human insulin!Because they reproduce so quickly, you’ll soonhave thousands, millions, or billions of humaninsulin making machines.By filtering out the bacteria after they’ve madeinsulin, you’ve got clean human insulin that canbe packaged and given to diabetic patients.

Virus?

A virus is an infectious agent made up of nucleic acid (DNA or RNA) wrapped in a

protein coat called a capsid.

Viruses have no nucleus, no organelles, no cytoplasm or cell membrane—Non-cellular

vs

This is why it does NOT belong to any kingdom.

Replication is how a virus spreads.A virus CANNOT reproduce by itself—it must invade a host cell and take over the cell activities, eventually causing destruction of the cell and killing it. (The virus enters a cell, makes copies of itself and causes the cell to burst releasing more viruses.) DNA/RNA is

copied.DNA/RNA injected

into cell.Virus attaches to cell.

Virus copies itself.

Cell bursts (lyses) and releases new viruses.

Step 1

Step 2 Step 3

Step 4

Step 5

Viruses have either DNA or RNA but NOT both.

Viruses with RNA that transcribe into DNA are called

retroviruses.

HIV Cell

A flea is a parasite to a dog and is harmful to the dog.

Viruses are parasites—an organism that depends entirely upon another living organism (a host) for its existence in such a

way that it harms that organism.

(This is the reason why HIV is so incurable.)

Categories of Cells Type 2 Eukaryotes

• Unicellular or Multicellular

• Has a Nucleus• Example – Plant,

Animal, fungi

How are Eukaryotes Different from Prokaryotes

Eukaryotes have a nucleus that contains DNA and Prokaryotes do not

Types of Cells in the Human Body

• •

• •

Two Types of Eukaryotes – Animal and Plant Cell

Let’s take a good look at these eukaryotes!

Cell Structures in common

Cell Membrane Nucleus Ribosome

Endoplasmic

Reticulum

Vacuoles Mitochondria

Nucleus

• Controls most of cells processes

• Contains genetic information-DNA

• Chromosomes inside nucleus are the threadlike structures containing genetic information

Nucleolus• Found inside nucleus

• Produces ribosomes

Nuclear Envelope (membrane)

• Surrounds genetic material

Ribosomes

• Makes proteins for cell

• Instructions come from the nucleus

Endoplasmic Reticulum

• Synthesizing, packaging and transporting of proteins

• Two types – rough ER and smooth ER

• Network of membranes

Golgi Apparatus

• Packaging system• Takes small molecules

and makes larger ones then stores them

• Proteins

Vacuoles

• Storage areas for water, salt, proteins, carbohydrates

Mitochondria

• Synthesis and release of energy

• Powerhouse of cell

Cell Membrane

• Allows movement of materials in and out of cell

Cell Membrane

• Regulates what enters and exits the cell

• Provides protection and support

• Semi-permeable – allows small substances through and keeps larger substances out

• Made of lipids and proteins

Cell Membrane

Cell Wall (Plant Only)

• Provides support, protection and structure for plant cell

Chloroplast (Plant Only)

• Site of photosynthesis