BIO190: The Class: Cells: Lesson 4

The Cell as the Unit of Life

The Department of Biological Sciences offers several different courses in cell biology. Contact the Biology Advisement Office for details at (520) 523-9304.

Life is composed of cells. Some organisms have only one cell, while others have billions. Despite this disparity in cell numbers, cellular processes have great similarities. The cell is the fundamental "building block" of living organisms. The study of cells is cytology.

For additional information, explore these web sites:

The Concept of the Cell

All animals and plants are composed of cells and cell products. Thus the cell theory is another of the great unifying concepts of biology. Listed below are some of the pioneers of cell biology.

R. Hooke

van Leeuwenhoek

Schleiden

Schwann

Purkinje

Cells are Studied with Microscopes

Biologists study cells using different kinds of instruments, principally microscopes. The light microscope and electron microscopes are the predominant instruments for studying cells.

Light microscopes (fig. 4-2)

Open the sites below to find out about light microscopes and their history.

Electron microscopes (EM) (fig. 4-2)

Open the site below for a look at electron microscopy.

1. SEM
2. TEM

X-ray crystallography

Nuclear magnetic resonance (NSR)

prokaryotic vs eukaryotic cells (tab. 4-10)

Organization of Cells

For information on cell organization browse these sites:

Look at the following figures in your book for information on cell structure, cell components and the functions of cells.

Plasma membrane (fig. 4-4)

Microvilli (fig. 4-6)

Nuclear membrane (fig. 4-4)

Nucleus (fig. 4-4 & 4-7)

Nucleolus (fig, 4-4 & 4-7)

Ribosomes (fig. 4-8A)

Endoplasmic reticulum=ER (fig. 4-8A & B)

1. RER
2. SER

Golgi complex (fig. 4-9)

Lysosomes

Mitochondria (fig. 4-11)

Cytoskeleton

1. microfilaments (fig. 4-12)
2. microtubules (fig. 4-13 & 4-14)

Open the link below for more information.

The Cytoskelton

Cell Surfaces

The following terms are important in understanding the surfaces of cells and their specialized functions.

Cilia

Flagella

Pseudopodia

Junction complexes (fig. 4-15)

1. tight
2. desmosomes
3. gap

Membrane Structure

The thin plasma membrane that encloses every cell is important in maintaining cellular integrity.

Fluid-mosaic model (fig. 4-16)

Membrane Function

The plasma membrane acts as a gatekeeper for the entrance and exit of the many substances involved in cell metabolism. Biologists recognize three ways that a substance may pass through the cell membrane.

Open the link below on cellular transport Cellular Transport

1. Diffusion

(concentration gradient)

Most cell membranes are selectively permeable: permeable to water, but may be permeable or impermeable to solutes.

Osmosis (fig. 4-17)

2. Mediated transport

1. facilitated diffusion (fig. 4-18)
2. active transport

3. Endocytosis (fig. 4-20)

1. phagocytosis
2. photocytosis
3. receptor-mediated (fig. 4-20)

Exocytosis – process of extruding contents into the surrounding medium.

Cell Cycle (fig. 4-21)

Cells undergo cycles of growth and replication as they repeatedly divide. Somatic cells (body cells, not related to reproduction) divide by mitosis.

Mitosis (nuclear division) (figs. 4-24 & 4-25)

The Stages of Interphase

G1

S

G2

1. prophase
1. spindle
2. aster
2. metaphase
3. anaphase
4. telophase

Open this link to learn more about mitosis.

(cytoplasmic division)

(cleavage furrow-during the final stages of cell division, encircles the midline of the spindle of the dividing cell. ( fig. 4-25))

Once you have completed the lesson, you should go to Assignment 4-1.

E-mail Sylvester Allred at Syl.Allred@nau.edu

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