BIOLO

GY 11 IB

2.1: C

ELL T

HEORY

DEFINE: CELL

The smallest functional unit of an organism

Cells contain organelles (discreet units that carry out a specific function) that carry out the processes that classify the cell as being “alive”. All unicellular organisms are able to carry out these life processes.

Human Nerve Cell

How are these cells essential to our lives?

2.1.1 OUTLINE THE CELL THEORY

1. All organisms are composed of cells

2.Cells are the smallest units of life

3. All cells come form preexisting cells

EXCEPTIONS TO CELL PATTERN

Muscle Cells

• Multiple nuclei

Fungal Hyphae

• Consist of multiple cells the share a continuous cytoplasm

2.1.2DISCUSS THE EVIDENCE FOR THE CELL THEORYListen to: Cell Theory Rap

Complete Cell Theory Timeline Worksheet

2.1.2DISCUSS THE EVIDENCE FOR THE CELL THEORY

Light Microscope:

• Light microscopy has a resolution of about 200 nm, which is good enough to see cells, but not the details of cell organelles.

• Specimens can be seen in actual color or through staining

• There is a wide view to observe the tissue structure (2mm)

• Living specimens can be observed and therefore their movement can be studied

TWO TYPES OF ELECTRON MICROSCOPESScanning Electron Microscope:

• Passes a beam of electrons over the surface of the specimen in the form of a scanning beam

• Electrons are reflected off the surface of the specimen as it has previously been coated in heavy metals

• Allows thicker structures to be seen that the transmission electron microscope but has a lower resolution

Transmission Electron Microscope:

• Passes a beam of electrons through the specimen

• The electrons are detected on a fluorescent screen where the image is displayed

• Thin sections of specimen are needed as electrons have to pass through for an image to be displayed

MICROSCOPE ADVANTAGES

Light MicroscopeColor images

Large field of view

Easily prepared sample material

Possibility of examining living material and observing movement

Electron MicroscopeGreater resolution: the ability to distinguish between two points on an image (like pixels in a digital camera)

Greater magnification: how much bigger a sample appears to be under the microscope that it is in real life

2.1.4 COMPARE THE RELATIVE SIZES USING APPROPRIATE SI UNITS

A 100 µm cell is 10x larger than a. . .

10 µm organelle which is 10x larger than a. . .

1 µm bacteria which is 10x larger than a. . .

100 nm virus which is 10x larger than a. . .

10 nm membrane which is 10x larger than a. . .

1 nm molecule

2.1.5 CALCULATE THE LINEAR MAGNIFICATION OF DRAWINGS AND THE ACTUAL SIZE OF SPECIMENS IN IMAGES OF KNOWN MAGNIFICATIONTo calculate the linear magnification of a drawing the following equation

should be used:

Magnification = Size of image (with ruler)________

Actual size of object (according to scale bar)

To calculate the actual size of a magnified specimen the equation is simply re-arranged:

Actual size = Size of image (with ruler)

Magnification

2.1.6 EXPLAIN THE IMPORTANCE OF THE SURFACE AREA TO VOLUME RATIO AS A FACTOR OF LIMITING CELL SIZE

All organisms need to exchange substances such as food, waste, gases and heat with their surroundings. This is true for organelles, cells, tissues, organs, and organisms

The rate of exchange of substances therefore depends on the organism’s surface area that is in contact with its surroundings. It also depends on the volume of the organism.

The ability to meet the requirements of life depends on the surface area to volume ratio.

2.1.6 EXPLAIN THE IMPORTANCE OF THE SURFACE AREA TO VOLUME RATIO AS A FACTOR OF LIMITING CELL SIZE

As organism get bigger their volume and surface area both get bigger, BUT not by the same amount!

This can be seen by performing some simple calculations concerning different-sized organisms.

(Complete last page of workbook from yesterday)

HOW TO ORGANISMS MAXIMIZE THE SURFACE AREA TO VOLUME RATIO?

As organisms grow cells divide because two small cells are more efficient than one large cell. This also allows for cell differentiation, specialized functions, and more complex multicellular life.

Cells use membranes to carry out metabolic processes.

Organelles, like the mitochondria, are also made up of membranes – maximizing the surface area of reactions.

Organs do it too! Example: the intestine, and the lungs (through alveoli)

Metabolism

Reproduction

Growth

Response

Homeostasis

Nutrition

In your own words describe how these functions tie together to produce a functioning living unit (Hint: refer to page 13 in your textbook)

2.1.3STATE THAT UNICELLULAR ORGANISMS CARRY OUT ALL THE FUNCTIONS OF LIFE

Viruses are composed of a protein coat containing either nucleic acid DNA or RNA

They are a-cellular (not made of cells) and since they cannot reproduce (or do any of the six characteristics of life) on their own they are considered non-living

A VIRUS IS A NON-CELLULAR STRUCTURE!

2.1.7 STATE THAT MULTICELLULAR ORGANISMS SHOW EMERGENT PROPERTIESCells combines to form tissues• a group of similar cells performing a specific function. Simple tissues

are composed of one type of cell, compound tissues are composed of more than one type of cell. Examples: epithelium, connective/skeletal, nerve, muscle, blood)

Tissues combine to form organs • a group of physically linked different tissues working together as a

functional unit. Example: Stomach composed of epithelium, muscle, and blood tissues)

Multiple organs form organ systems, and multiple organ systems form an organism

2.1.8 EXPLAIN THAT CELLS IN MULTICELLULAR ORGANISMS DIFFERENTIATE TO CARRY OUT SPECIALIZED FUNCTIONS BY EXPRESSING SOME OF THEIR GENES BUT NOT OTHERS

Multicellular organisms are large and have to specialize parts of their structure to complete the six characteristics of life

This leads to cells within multicellular organisms specializing in function

Specialized cells express particular genes that correlate to these specialist functions. This could produce specific shapes, functions, and adaptations within a cell.

Therefore muscle cell will express muscle genes but not those genes which are for nerve cells

CELL DIFFERENTIATION – THE RESULT OF GENE EXPRESSION

Totipotent: Can become any cell type

Pluripotent: can become any type except embryonic membrane

Multipotent: can become a number of different cell types (EXAMPLE: stem cells)

Unipotent: Can only become one cell type (EXAMPLE: muscle cells)

Nullpotent: Cannot divide (EXAMPLE: red blood cells)

2.1.9 STATE THAT STEM CELLS RETAIN THE CAPACITY TO DIVIDE AND HAVE THE ABILITY TO DIFFERENTIATE ALONG DIFFERENT PATHWAYSIn the meristematic (root and stem tips) area of plants

When stem cells divide to form a specific type of tissue, they also produce some cells that remain as stem cells.

2.1.10 OUTLINE ONE THERAPEUTIC USE OF STEM CELLS

In partners research one therapeutic use of stem cells.

You can use your book, your smart phone, or the classroom computer.

Be prepared to share what you found with the class.

THERAPEUTIC CLONING OF STEM CELLS

Therapeutic cloning involves the in-vitro culturing of tissues using patient or donor stem cells. It can be used to replace tissues lost in disease, burned skin or even nerve cells.

STEM CELL USE

In the treatment for lymphoma, bone marrow is destroyed in chemo or radio therapy. Before this aggressive treatment takes place, stem cells are harvested from the bone marrow and stored.

These harvested cells can be used to replace damaged bone marrow, producing healthy blood cells in the recovering patient.