Cellular Basis of Life

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What is Life? This perennial question the answer to
which has somehow eluded the most brilliant minds. For while scientists have identified many years ago the right mix of the atoms and molecules that constitute cellular material, they
have not succeeded in ‘switching it on’ to make it alive, or ‘breathing life’ into it (Rabago et.al,2006)

In this module you will:
a. Explain the concepts of the cell theory
b. Identify the parts of a cell
c. Describe the function of each cell part
d. Differentiate prokaryotic from eukaryotic
cells
e. Compare plant and animal cells

A. The Cell Theory
-

structurally made up of

1. What are living things made
of?

cells.
-

2. What can cells do?
3. Where do cells come from?

All living things are

The cell is the fundamental
unit of life.

-

Cells come from the
division of pre-existing
cells.

B. Cell Structure and Composition

CELL MEMBRANE
-Serves as the outer boundary of the
cell. It is a selective permeable
membrane which permits the
entrance of substances throughout
the cell.

CYTOPLASM
-Serves as the reservoir of the
organelles as it contain all the lifesustaining components. It is a jellylike structure.

NUCLEUS
-Usually located at the center and
known as the control center of the
cell. It regulates and coordinates all
the activities of the cell.

C. Organelles in the Cytoplasm

ORGANELLES

STRUCTURE
Membrane

Components

Module 8
A. 1. smooth endoplasmic reticulum – usually the site for fat metabolism; forms vesicles for transporting large molecules to other cell parts 2. mitochondria – sites of cellular respiration
3. Golgi apparatus – involved in modifying, sorting and packaging macromolecules for secretion or for delivery to other organelles 4. nuclear membrane – a double membrane which separates the nucleoplasm from the cytoplasm

5. nucleolus – the site where subunits of ribosomes are formed 6. nuclear pore – serves as pathway for the exchange of materials between the nucleus and the cytoplasm
7. rough endoplasmic reticulum – studded on its outer surface with ribosomes for the synthesis of protein

FUNCTION

D. Variations in Cell Structure and Function

d.1 Prokaryotic Cell vs. Eukaryotic Cell

A typical Prokaryotic Cell

A typical Eukaryotic Cell

Prokaryotic Cells

Eukaryotic Cells

Pro = “before”, karyon = “nucleus”

Eu = “true”, karyon = “nucleus”

Prokaryotes are evolutionarily
ancient. They were here first and for
billions of years were the only form of
life. And even with the evolution of
more complex eukaryotic cells,
prokaryotes are supremely
successful. All bacteria and bacterialike Archaea are prokaryotic organisms.

Eukaryotic cells are more complex,
evolving from a prokaryote-like
predecessor. Most of the living things
that we are typically familiar with are
composed of eukaryotic cells;
animals, plants, fungi and protists.
Eukaryotic organisms can either be
single-celled or multi-celled.

PROKAYOTIC

EUKARYOTIC

Nucleus:

Present

Number of chromosomes:

More than one

Cell Type:
True Membrane bound
Nucleus:
Example:

Multicellular

Absent
One--but not true
chromosome: Plasmids
Unicellular

Present

Absent

Animals and Plants

Telomeres:

Present (Linear DNA)

Genetic Recombination:

Mitosis and fusion of gametes

Lysosomes and peroxisomes:
Microtubules:
Endoplasmic reticulum:
Mitochondria:
Cytoskeleton:
DNA wrapping on proteins.:
Ribosomes:
Vesicles:
Golgi apparatus:
Mitosis:

Present
Present
Present
Present
Present
Yes
larger
Present
Present
Yes

Chloroplasts:

Present (in plants)

Bacteria and Archaea
Circular DNA doesn't need
telemeres
Partial, undirectional transfers
DNA
Absent
Absent or rare
Absent
Absent
May be absent
No
smaller
Present
Absent
No---but has binary fission
Absent; chlorophyll scattered
in the cytoplasm

Flagella:

Microscopic in size;
membrane bound;...
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