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Cell Structure & Function
History of the cell
Antonie van Leeuwenhoek (1673) – constructed a crude microscope to analyze
“animalcules” in pond water & other “tiny things”
Robert Hooke (1665) – coined the word “cellulae” (small roon) to describe the boxlike
cavities he saw when viewing cork slices under a microscope
Both of these individuals observations were discarded for nearly 200 years, due to
social standing
Development of the CELL THEORY
Matthias Schleiden (1838) – using a microscope proposed that all plants are composed
of cells
Theodor Schwann (1839) – using a microscope proposed that all animals are composed
of cells
Together they stated:
1. Cells are the elementary particle of all living organisms
2. All cells are alive – independent to the organisms to which they belong
Chapter 3 – Cell Structure & Function
Development of the CELL THEORY
Rudolf Virchow (1858) – stated
1.
Cells never arise from noncellular material
2.
Diseases result from changes in specific kinds of cells
CELL THEORY
1.
All organisms are composed of one or more cells
2.
Cells are the basic living unit of organization of all organisms capable of
independent existence
3.
All cells come from other cells
Chapter 3 – Cell Structure & Function
What are cells composed of?
All cells are composed of a boundary, a cell body, & a set of genes
The plasma membrane is a boundary that separates the contents of the cell from the
surrounding environment
It is composed of a phospholipid bilayer in which protein molecules are embedded
It serves to regulate the passage of materials into & out of the cell, thus maintaining a
homeostatic environment for the cell’ life processes
Cell Structure & Function
Cells also contain a set of genes, which are composed of DNA
Genes contain all of the necessary information for the growth, development, &
maintenance of an organism throughout its life cycle
In our cells, along with those of plants, fungi (mushrooms), & protists (amoeba), the
genes are contained within a membrane bound structure called a nucleus. The presence
of this nucleus defines a category of cells called eukaryotic cells
Prokaryotic cells (bacteria) do not possess a gene containing nucleus. Its genes occupy
a region called the nucleoid. It is not protected by a membrane barrier.
The cell body is defined as the area between the nucleus & the plasma membrane
It is filled with a semi-fluid substance called cytoplasm
Cytoplasm is 90% water & contains dissolved molecules as well as the organelles of the
cell
Chapter 3 – Cell Structure & Function
Cell Structure & Function
What kind of functions does a cell have to accomplish in order to survive?
Organelles & their functions
Nucleus – Stores genetic information for the cell. It is surrounded by a double
membrane called the nuclear envelope.
The nuclear envelope contains nuclear pores to allow the passage of materials between
the nucleus & the cytoplasm
The nucleus also contains
nucleoli which synthesize
ribosomes necessary for protein
synthesis
Chapter 3 – Cell Structure & Function
Cell Structure & Function
The endomembrane system – is composed of the nuclear envelope, endoplasmic
reticulum, golgi apparatus, & vesicles
Endoplasmic reticulum (ER) – a series of flattened stacks of vesicles (saccules) which
are continuous with the outer membrane of the nuclear envelope
ER exists as either Smooth ER (SER) or Rough ER (RER)
RER is studded with ribosomes,
giving the ER its “rough”
appearance. It is involved in
protein synthesis, packaging the
newly synthesized proteins for
further modification
SER does not have attached
ribosomes, hence smooth
appearance. It is involved in lipid
metabolism, hormone production,
detoxification, vesicle formation,
& other processes
Chapter 3 – Cell Structure & Function
Cell Structure & Function
Cell Structure & Function
Golgi apparatus – a stack of 3 to 20 saccules which are involved in modifying &
packaging proteins & lipids delivered to it from the ER
Once the molecules have been modified, they exit the Golgi via vesicles which will
then migrate to the plasma membrane to secrete the molecule or have them embedded
in the plasma membrane
Other vesicles will remain in
the cytoplasm, becoming
organelles like lysosomes &
peroxisomes
Chapter 3 – Cell Structure & Function
Lysosomes – contain digestive enzymes
What kind substances do you think lysosomes digest?
Autophagy – digestion of organelles
Autolysis – digestion of their host cell
Vacuoles – large membranous sacs for storing substances
Cell Structure & Function
Mitochondria structure
It is a double membrane organelle enclosing a fluid-filled space called the matrix.
The inner membrane contains the key enzyme ATP synthase which is used to
synthesize ATP from the breakdown of energy rich molecules like carbohydrates
Cell Structure & Function
Cytoskeleton
It is a network of interconnected filaments & tubules that extends from the nucleus to
the plasma membrane
It determines cellular shape & movement
Composed of microtubules, microfilaments, & intermediate filaments
1) Microtubules are composed of the globular protein tubulin. They are important for
maintaining asymmetrical cell shape (neurons) & complex cell movements: A)
transportation of secretory vesicles within the cell, B) movement of flagella & cilia, &
C) distribution of chromosomes during cell division
2) Microfilaments which are composed of the proteins actin (globular) & myosin (golfclub shaped). They are involved in contractile mechanisms (muscle & cytokinesis)
contraction & as mechanical stiffeners for several cellular projections (microvilli)
3) Intermediate filaments are highly stable polymers. They primarily support the
nuclear envelope & the plasma membrane
Cell Structure & Function
Cell Structure & Function
Centrioles – Form the microtubule organizing centers in cell reproduction / division
(mitosis). Involved in assembling & disassembling microtubules necessary for mitosis
Cell Structure & Function
Cilia & Flagella – cell movement or the movement of substances along the cell surface
Which of your cells contain cilia or flagella?