An Overview of Cellsand Cell Research

1 An Overview of Cells and Cell Research

Chapter OutlineModel Species and Cell types

Cell components

Tools of Cell Biology

Model Species

E. Coli: simplest organism

Yeast: simplest single-cell Eukaryotic organism

Drosophila melanogaster: multi-cell organism

C. Elegans: multi-cell organism

Zebrafish: Vertebrates

Xenopus laevis: Vertebrates

Arabidopsis: model plant species

Mouse:

Human: human genetics

Figure 1.13 Bacterial colonies

Cells as Experimental Models

E. coliThe genome consists of approximately 4.6

million base pairs and contains about 4300 genes.

E. coli divide every 20 minutes.

Useful for bioengineering (producing proteins and drugs)

Figure 1.14 Electron micrograph of Saccharomyces cerevisiae

Cells as Experimental Models

Yeasts

The genome of Saccharomycescerevisiae consists of 12 million base pairs of DNA and contains about 6000 genes.

Good for genetics manipulation

Useful for gene-gene interaction and chemical genetics

Figure 1.15 Caenorhabditis elegans

Cells as Experimental Models

The genome of C. elegans contains approximately 19,000 genes

C. elegans has only 959 somatic cells. The embryonic origin and lineage of all the cells has been traced.

Great model for developmental biology

Figure 1.16 Drosophila melanogaster

Cells as Experimental Models

The fruit fly Drosophila melanogaster has been a crucial model organism in developmental biology.

Drosophila is easy to grow

Reproduce in about 2 weeks

Figure 1.17 Arabidopsis thaliana

Cells as Experimental Models

A model for plant molecular biology and development is the small mouse-ear cress, Arabidopsis thaliana.

It has a small genome and is easily grown in the lab.

Studies of Arabidopsis have led to the identification of genes involved in aspects of plant development, such as the development of flowers.

Figure 1.18 Eggs of the frog Xenopus laevis

Figure 1.19 Zebrafish

Cells as Experimental Models

Vertebrates are the most complex animals, and the most difficult to study from the standpoint of cell and molecular biology.

One approach is to use isolated cells in culture.

Xenopus produces large eggs in large numbers, facilitating laboratory study and biochemical analysis. Good for developmental biology

Zebrafish bridge the gap between humans and simpler invertebrate systems, like C. elegans and Drosophila.

Figure 1.20 The mouse as a model for human development

Figure 1.7 Evolution of cells

Tools of Cell Biology

The cell theory:

All living systems are made of cells

All cells come from pre-existing cells

All of life’s functions are cellular

The Origin and Evolution of Cells

Two types of cells:Prokaryotic (bacteria) lack a nuclear envelope.Eukaryotic have a nucleus that separates genetic material from cytoplasm.

Cell types

Animals have five main tissue types:

Epithelial cells form sheets that cover the surface of the body and line internal organs.

Skin, intestine surface

Fibroblasts cells form connective such as

bone, cartilage, and adipose tissue.

The Origin and Evolution of Cells

Blood contains several different types of cells:

Red blood cells (erythrocytes) function in oxygen transport.White blood cells (granulocytes, monocytes, macrophages, and lymphocytes) function in inflammatory reactions and the immune response.

The Origin and Evolution of Cells

Nervous tissue is composed of supporting cells and nerve cells, or neurons, and various types of sensory cells.

Muscle cells are responsible for the production of force and movement.

Figure 1.12 Light micrographs of representative animal cells (Part 1)

Figure 1.12 Light micrographs of representative animal cells (Part 2)

Figure 1.6 Structures of animal and plant cells (1)

Figure 1.6 Structures of animal and plant cells (2)

The Origin and Evolution of Cells

Mitochondria: site of oxidative metabolism.

Chloroplasts: site of photosynthesis.

Lysosomes and peroxisomes: specialized metabolic compartments for the digestion of macromolecules and for various oxidative reactions.

The cytoskeleton is a network of protein filaments extending throughout the cytoplasm.

The Origin and Evolution of Cells

The endoplasmic reticulum is a network of intracellular membranes, extending from the nuclear membrane throughout the cytoplasm. It functions in the processing and transport of proteins and the synthesis of lipids.

In the Golgi apparatus, proteins are further processed and sorted for transport to their final destinations

Tools of Cell Biology

The discovery of cells arose from the development of the light microscope.

Robert Hooke coined the term “cell”following his observations of a piece of cork in 1665.

In the 1670s Antony van Leeuwenhoek was able to observe a variety of cells, including sperm, red blood cells, and bacteria.

Figure 1.22 Numerical aperture

Figure 1.24 Microscopic observation of living cells

Figure 1.25 Video-enhanced differential interference-contrast microscopy

Figure 1.26 Fluorescence microscopy (Part 1)

Figure 1.26 Fluorescence microscopy (Part 2)

Figure 1.30 Confocal microscopy

Figure 1.31 Confocal micrograph of human cells

Figure 1.33 Positive staining

Figure 1.34 Negative staining

Figure 1.37 Scanning electron microscopy

Tools in Cell Biology

Subcellular fractionation with centrifugation

Cell culture

Use virus to change the genes in cultured cell

Figure 1.38 Subcellular fractionation (Part 1)

Figure 1.38 Subcellular fractionation (Part 2)

Tools of Cell Biology

In vitro culture systems of plant and animal cells enable scientists to study cell growth and differentiation, and perform genetic manipulations.

Most animal cell types attach and grow on the plastic surface of dishes used for cell culture.

Tools of Cell Biology

Embryonic stem cells can be established in culture and maintain their ability to differentiate into all of the cell types of adult organisms.

Embryonic stem cells have played an important role in studying gene function in mouse development, and offer the possibility of treating many human diseases by transplantation therapies.

Figure 1.41 Culture of animal cells

Figure 1.42 Plant cells in culture