Chapter 1 Introduction to cell biology
1.1 What is cell biology
Cell biology is the application of molecular biological approaches to an
understanding of life at the cellular level. Knowledge of the molecular
basis of cell structure, cell function and cell interactions is fundamental to
an understanding of whole organisms.
What?
Cell
biology
is
the
application
of
molecular
biological approaches to an understanding of life at the cellular level
For why? Knowledge of the molecular basis of cell structure, cell
function and cell interactions is the fundamental to an understanding of
whole organisms
How to study? Grasp the fundamental concepts; the composition of cells
and how cells works; appreciating the similarities and differences
between cell types; genomics and proteomics
1.1.1 Cell biology is the basis of modern biology
Study the molecules within cells: cell biology concentrations on:
macromolecules and reactions, investigated by biochemists; the process
described by cell biologists; the gene control pathways identified by
molecular biologists and geneticists.
Study the molecular similarities and differences between cell types:
understanding the composition of cells and how cell works is
fundamental to all of the biological sciences.
1.1.2 Cell biology is in progress
All the concepts of cell biology continue to be derived from
computational
experiments
and
laboratory
experiments.
millennium, two gathering forces will reshape cell biology:
The genomics, the complete DNA sequence of many organisms
In
this
The proteomics, the knowledge of all the possible shapes and functions
that proteins employ.
1.2 The cell theory
The cell theory is the basis of molecular cell biology, and this theory is
known as one of the three indispensable theories upon which the science
of biology is built. These theories are: 1. The theory of evolution; 2. The
cell theory; 3. The theory of equilibrium thermodynamics. The cell theory,
or cell doctrine, states that all organisms are composed of similar units of
organization, called cells.
1.2.1 Formation of the cell theory
In 1663 Robert Hook, an English scientist, discovered cells in a piece of
cork. He drew the cells he saw and also coined the word ‘cell’. The word
cell is derived from the Latin word ‘cellulae’ which means small
compartment. Ten years later, Anton van Leeuwenhoek, a Dutch
businessman, was the first person to observe bacteria and prozotoa.
Between 1680 and the early 1800’s, due to the lack of quality lens for
microscopes and the dedication to spend long hours of detailed
observation, the new discovery in cell biology field is less.
Schleiden brought nucleus to popular attention and to assert its allimportance in the function of a cell. In 1939, Schwann propounded what
he saw and became famous as the cell theory. In 1838, Dr. Schleiden, a
German professor of botany, concluded that despite differences in the
structure id various tissues, plants were made of cells and that the plant
embryo arose from a single cell. In 1839, Schwann summarized his
observations in animal life into three conclusions:
Schwann summarized his observation into three conclusions about cells:
1. The cell is the unit of structure, physiology, and organization in living
things;
2. The cell retains a dual existence as a distinct entity and a building
block in the construction of organisms
3. Cells form by free-cell formation, similar to the formation of crystals.
1.2.2 Modern tenets of cell theory
The modern tenets of the cell theory include:
1.All known living things are made up of cells;
2.The cell is the structural and functional unit of all living things;
3.All cells come from pre-existing cells by division;
4.Cells contains hereditary information which is passed from cell to cell
during cell division;
5.All cells are basically the same in chemical composition;
6.All energy flow of life occurs within cells.
1.3 Consider the basic properties of cells
1. Cells are highly complex and organized, capable of self-regulation.
2. All cells share similar.
3 Cells can capable of producing more of themselves, even grow and
reproduce in culture for extended periods。
4 Cells are able to respond to stimuli via surface receptors that sense。 1.4 The concept of cell
Cell is the basic unit of life
Cell is the basic unit of organism
Cell is the basic unit of metabolism and function
Cell is the basic unit of development
Cell is the basic unit of heredity
1.5 The common feature of cell
Cell is the basic unit of life
New insight of cell concept
The common feature of the cell
The similarity of chemical component：Biomembrane system； The
carrier of hereditary information: DNA and RNA； Ribosome； Cell
division
1.5.1 Plasma membrane:
All cells have a ‘skin’, called the plasma membrane, protecting them
from the outside environment.
1.5.2 Nucleus:
At the center of the cell is the cell nucleus. The cell nucleus contains the
cell’s DNA, the genetic code that coordinates protein synthesis.
1.5.3 Organelles:
There are many organelles inside of the cell. One important cellular
organelle is the ribosome, which participate in protein synthesis. Another
important cellular organelle is the mitochondrion, which is often referred
to as the power plants of the cell because many of the reactions that
produce energy take place in it.
1.6 Virus
Viruses are pathogens first described in the late 1800s. Studies of tobacco
mosaic disease in tobacco plants and hoof-and-mouth disease in cattle
pointed to the existence of another type of infectious agent
Three types of virus:
plant virus; animal virus; bacterial virus
1.6.1 Viral structure:
a) The genetic material:
Single- or double- stranded DNA or RNA
b) Obligatory intracellular parasites：
They cannot reproduce unless present within a host cell, which depending
on the specific virus may be a plant, animal or bacterial cell
c) Virion is surrounded by a protein capsule, or capsid, which is generally
made up of specific number of subunits.
The most advantages is an economy of genetic information. Many viruses
have a capsid Whose subunits are organized into a polyhedron, a structure
having planar faces. A particular common polyhedral shape of virus the
20-sided icosabedron. In many animal virus, including HIV, the protein
capsid is surrounded by a lipid-containing outer envelope that is derived
from the modified plasma membrane of the host cell as the virus buds
from the host cell surface.
1.6.2.Viral infection types:
a) Lytic infection: the virus arrest the normal synthetic activities of the
host and redirects the cell to use its available materials to manufacture
viral nucleic acids and proteins, which assemble into new virions.
Ultimately, the infected cell ruptures and releases a new generation of
viral particles capable of infecting neighboring cells.
b) Integrated infection: the infecting virus does not lead to the death of
the host cell, but instead inserts its DNA into the DNA of the host cell’s
chromosome. The integrated viral DNA is called a provirus. Bacterial cell
containing provirus leads to the lysis of the cell and release of viral
progeny unless respond to the stimulus, such as radiation. Some animal
cells containing provirus produce new progeny that bud at the cell surface
without lysing the infected cell, which remain alive for period acting as a
factory for the production of new virions. Tumor virus is the cause of host
cell growth retarded and unable to division, eventually leading to
malignant.
1.6.3 Viral origins:
a) Viruses had to arise after their hosts evolved.
Once you consider that virus are totally dependent on the living cells they
invade, it becomes evident that virus could not have arrived on the scene
before their hosts: the same genetic language;
b)Viruses probably arose as fragments of host chromosomes.
Virus heave presumably evolved from small fragments of cellular
chromosomes that were able to maintain some type of autonomous
existence within the cell.
1.7 Prion
In 1982, S.B. Prusiner discoverded prion, which is composed of only
infectious protein.
• PrPc——PrPSc
• Proliferation: PrPc turned into PrPSc (dimer)
1.8 viriods:
The smallest infectious agent, a naked RNA containing 240-600
nucleotides, a tenth the size of the smaller virus.
1.9 Diversity of cells
1.9.1 Diversity of prokaryotic cell
The cyanobacteria. formerly known as the blue-green algae, are the
largest of the prokaryotes cells.
Bacteria are the most abundant of all organisms
Features:
minute: 0.5-5.0 µm in size
cell wall: peptidoglycan
nucleoid:
cell membrane:
mesosome: The start point of DNA replication
ribosome:
1.9.1.1 Bacteria are the most abundant of all organisms
They are ubiquitous in soil, water, and symbionts of other organisms.
Many pathogens are bacteria. Most are minute, usually only 0.5-5.0 μm
in size. They generally have cell walls, like plant and fungal.
1.9.2 Diversity of eukaryotic cell
The diversity derived from both cariety in gene expression and from the
patterns of cellular control for gene product behavior. One can understand
complex developmental processes only by considering them in the
context of the cells that comprise the objects being formed.
1.9.2.1 Alga
A variety of thallus formats characterize algae. It can consist of a single
cell, or many cells in varying arrangement. Four types of algae are
recognized, based on the following body structures: unicellular, colonial,
filamentous, and multicellular.
1.9.2.2 Protists
The forst protist fossils occur in rocks approximately 1.2-1.4 billion years
old from the Bitter Springs Formation. Due to this tremendous diversity,
classification of the protista is difficult.
1.9.2.3 Fungi
Fungi are almost entirely multicellular, heterotrophic, and usually having
some cells with two nuclei per cell.
1.10 The prokaryotic cell
1.10.1 Common features of prokaryotic cells
They have genetic materials but that material is not enclosed within a
membrane.
1. All have a plasma memmbrane
2. All have al region called the nucleoid where the DNA is concentrated.
3. The cytoplasm consists of the nucleoid, ribosomes and a liquid portion
called the cytosol.
1.11 The eukaryotic cell
1.11.1 Common features of eukaryotic cell.
Animals, plant, fungi, and protist have a membrane-bounded nucleus in
each of their cells and are clarified as eukaryotes.
1.Eukaryotic cells tend to be large than that of prokaryotic cells.
2.Each of eukaryotic cells has a membrane-bounded nucleus
3.Eularyotic cells have a variety of membrane-bounded compartments
cell organelles
4.Eukaryotic cells have protein scaffolding called cytoskeleton, which
provides shape and structure to cells, among other functions.
5.Biomembrane system 8-10nm
6.Hereditary information storage system
7.Chromosome: DNA+proteins nucleosome
8.Nucleolus: RNA+proteins DNA+proteins
9.Cytoskeleton system
1.12 The difference between prokaryotic and eukaryotic cell
A. Prokaryotic and eukaryotic cells are distinguished by the size and the
types of internal structures, or organelles, especially if there is nuclear
envelope.
B. Characteristics that distinguish prokaryotic and eukaryotic cells
1.Complexity: Prokaryotes are relatively simple,
eukaryotes are more
complex in structure and function
2.Genetic material:
a: All Cells Store Their Hereditary Information in the Same Liner
Chemical Code (DNA) Packaging: Prokaryotes have a nucleoid region,
whereas eukaryote have a true, membrane-bound nucleus.
b: Amount: Eukaryotes have several orders of magnitude more genetic
material than prokaryotes.
c: Form: Eukaryotes have many chromosomes that are made of both
DNA and protein whereas prokaryotes have a single DNA chromosome
3.Cytoplasma: Eukaryotes have membrane-bound organelles and
cytoskeleton proteins; prokaryotes have neither. Both have ribosome,
although they differ in size.
4.Cellular reproduction: Eukaryotes divide by mitosis; prokaryotes divide
by simple fission.
5.Locomotion: Eukaryotes use both cytoplasmic movement, and cilia and
flagella; prokaryotes have flagella, but they differ in both form and
mechanism from eukaryotic flagella.