Preview Questions

Preview Questions

1. Describe a typical prokaryote cell.2. Describe a typical eukaryote cell.3. Explain the differences between a prokaryote

and eukaryote cell.4. How has the simplicity of prokaryotes affected

their ability to adapt and survive / thrive?5. How has the complexity of eukaryotes affected

their ability to adapt and survive / thrive?

Cell theory1. All living things are made of cells2. Cell can only come from other

cells3. All functions of a living thing are

carried out in cells • Reminder: the functions of living things are:

respiration, metabolism, growth, adaptations to the environment, reproduction, homeostasis and interdependence

Different Types of Cells An overview

There are two main groups of cells, prokaryotic and eukaryotic cells.

Similarities: all are alive, all belong to one of the five life kingdoms.

Differences: appearance, structure, reproduction, and metabolism. – biggest differences are between cells of different

kingdoms

. 

Where to begin?

• Prokaryotes are simpler, so we will start with them.

VS

Diagrams courtesy - http://www.cod.edu/people/faculty/fancher/ProkEuk.htm

Prokaryotes were formed about 3.5 billion years ago,

or 3,500,000,000 years

Prokaryotesfrom the Greek meaning “before nuclei”

Why “before nuclei?”

• Prokaryotic cells have no nucleus. – Prokaryote’s DNA is circular (it has no

ends).– Small circlets of DNA are called

Plamids. • Prokaryotic DNA is “naked” – it has no

histones associated with it and does NOT form chromosomes

All Prokaryotes are in the monera kingdom

domains Bacteria and Archaea – bacteria – Cyanobacteria

• also known as blue-green algae

Prokaryote Characteristics1. Simplest organisms: Very small size.

2. Lack membrane-bound organelles inside the cell

3. have few internal structures that are distinguishable under a microscope.

4. genetic information is in a circular loop called a plasmid (instead of having chromosomal DNA)

5. Strong cell walls: resistant to environmental changes

1. Size• Bacterial cells are very small, • about 1-2µm in diameter and 10 µm long

– One micrometer = 1/1000 mm.• Imagine looking at a dime from its thinnest side

and trying to slice it into a thousand pieces; that is the same as 1 µm.

2. Lack membrane-bound organelles inside the cell

3. have few internal structures that are distinguishable under a

microscope.

http://www.umanitoba.ca/science/biological_sciences/lab3/biolab3_2.html#Examine

4. genetic information is in a circular loop called a plasmid

• E. coli cell dividing.

• E. Coli Grows in human intestine; – Has a single, circular

chromosome– contains DNA as

plasmids • Plasmids are extra-

chromosomal DNA

http://www.bio.mtu.edu/campbell/prokaryo.htm

5. Strong cell walls: resistant to environmental changes

Bacterial Structure

Shapes3 basic shapes Cocci - sphere

Bacilli - rodsSpirilla – spirals

2 basic groupingsStaph - in clusters

Strep - in chains

Spiral

Rod shaped

SphericalStreptococcus sp. Chains of nearly-spherical bacteria.From The Rockefeller University.

This spiral shaped bacteria is the causitive agent of syphilis Treponema pallidum

Replication• Binary fission

– one cell splits into two cells, see diagram• offspring are genetically identical to parent

Bacterial conjugation– a form of sexual

reproduction where bacteria exchange genetic information before dividing

• offspring have new genes (and new traits)

Figure 1. Schematic drawing of bacterial conjugation. 1- Donor cell produces pilus; 2- Pilus attaches to recipient cell, brings the two cells together; 3- The mobile plasmid is nicked and a single strand of DNA is then transferred to the recipent cell; 4- Both cells recircularize their plasmids, synthesize second strands, and reproduce pili. Both cells are now viable donors.

http://parts.mit.edu/igem07/index.php/Boston_University/Conjugation

• Transformation – bacteria incorporate genes from dead

bacteria

• Transduction – viruses insert new genes into bacterial cells. – This method is used in biotechnology to

create bacteria that produce valuable products such as insulin

MovementSome prokaryotes

can't move, while others have long threadlike flagella.

If bacteria doesn’t move, how does it get from person to person?

E.Coli flagella

Prokaryote Functions• decomposers• agents of fermentation• play important roles in digestive systems • involved in many nutrient cycles

– ex: the nitrogen cycle, which restores nitrate into the soil for plants.

• diverse array of metabolic functions. – For example, some bacteria use sulfur instead of oxygen in their

metabolism.

Bacteria images / resources

• http://www.ulb.ac.be/sciences/biodic/ImBacterie2.html

• http://www.buckman.com/eng/micro101/bacteria.htm

• Discovery school video: Understanding Bacteria

EukaryotesFrom the Greek for “true nucleus”

Example cells from the plantae and animalia kingdoms

Plant (elodea)

animal cells (blood vessel lining)

Eukaryote characteristics

All eukaryotes have …

1) A Cell membrane 2) A Central nucleus 3) Organelles in cytoplasm (like

ER, vacuoles, mitochondria, etc.)

Theories of the Origin or organelles• Symbiosis: two organisms live closely together • Endosymbiosis: one organism lives inside another (bacteria in

us)

Theory explaining why mitochondria and chloroplasts are found in cells:

• It's thought that mitochondria (m) and chloroplasts (c) were types of prokaryotic cells that lived inside other cells. The m & c helped keep the cell alive and so were retained.

• Evidence on relationship of mitochondria and chloroplasts to prokaryote cells:– a. mitochondria and chloroplasts are both surrounded by double

membranes (like bacteria are). – b. mitochondria and bacteria have similar size. – c. mitochondrial ribosomes resemble bacterial ribosomes. – d. mirochondria and chloroplast DNA is circular like bacteria.

size and shape are related to cell function. For Example:

1. birds’ eggs are large because they contain all the nutrient material that the developing bird embryo will need during its growth to a young chick.

2. Muscle cells are long, so that they can contract and shorten up, thereby moving body parts.

3. Nerve cells are also long — they need to transmit nerve signals to different parts of the body

4. epithelial cells are broad and flat

5. red blood cells are especially small because they need to get through the smallest capillaries of the circulatory system.

1.

2.

3.

4.5.

Structure – animal cell

Structure – plant cell

reproduction*Mitosis – body cells

*Meiosis – gametes (egg &

sperm)

Movement Internal1. The centriole 2. The cytoskeleton 3. Actin and tubulin

proteins

External4. Flagella 5. cilia

1.

3.

2.

4.5.

images

• http://web.jjay.cuny.edu/~acarpi/NSC/13-cells.htm

• http://www.cellbio.com/images.html

Review

Prokaryote & Eukaryote similarities

Both have1. DNA 2. A cell membrane3. Ribosomes4. Diverse forms (meaning a lot of shapes

and sizes)

Prokaryotes & Eukaryotes differences

Prokaryotes Eukaryotes•Plasmid DNA•No membrane-bound organelles•Few things inside (are simple)

•Nuclear bound DNA•Has membrane bound organelles•Many things inside (Are complex)

**Organelles are tiny structures inside cells that do a certain job.

Complete this Vinn Diagram worksheet and turn it in

Prokaryote Eukaryote

Write the things that are Different here

Write things that are the Same here

Write the things that are Different here

Characteristic Prokaryote EukaryoteSize 1-10um 10-100um

Nuclear Envelope Absent present

Chromosomes Single, circular, no nucleus

Multiple, linear, wound on nucleosomes

Golgi apparatus Absent Present

ER, Lysosomes Absent Present

Mitochondria Absent Present

Chlorophyll Not in chloroplasts Present in chloroplasts

Ribosomes Relatively small Relatively large

Microtubules, filaments, microfilaments

Absent Present

Flagella Lack microtubules Contain microtubules

Review Questions

1. Describe a typical prokaryote cell.2. Describe a typical eukaryote cell.3. Explain the differences between a prokaryote

and eukaryote cell.4. How has the simplicity of prokaryotes affected

their ability to adapt and survive / thrive?5. How has the complexity of eukaryotes affected

their ability to adapt and survive / thrive?