Transcript the cell - Learning Central

Introduction to the Cell
Copyright CSAN (2012), Images used with permission
The Cell
Outcomes
You should be able to:
• Briefly discuss the importance of understanding cell
structure and function in terms of health, illness and
nursing
• Give definitions for organism, organ, tissue, cell
• Describe the basic difference between Prokaryotic &
Eukaryotic cells
Outcomes
• Describe the basic structure of a Eukaryotic cell
– Briefly describe the cytoplasm
– Describe the structure of the cell membrane & briefly
explain its functions
– Describe Endocytosis and Exocytosis
– Describe the structure & function of the following
organelles/ cell structures:
• Lysosomes
● Nucleolus
• Mitochondria
● Chromatin
• Centrioles
● Endoplasmic
reticulum
• Nucleus
● Golgi apparatus
Levels of organisation
Think about your body:
What are its levels of organisation?
1.Chemical
2.Cellular
3.Tissue
4.Organ
5.System
6.Organism
CELL THEORY
1. All living things are made up of cells & the
products of those cells
2. All cells carry out their own life functions
3. New cells come from other living cells
Cell Theory is based on over 300 years of scientific
investigations, beginning with Hooke in 1665
Exceptions to Cell Theory
Viruses.
Cell Theory suggests
that we have to say they are not alive.
This is because a virus is not a cell.
Viruses are made protein & nucleic acid.
They have no membranes, nucleus, or protoplasm. They
only appear to be alive when they reproduce after infecting
a host cell. (This will be discussed in later sessions)
Mitochondria. Cell organelles that have their own
genetic material & reproduce independently from the rest
of the cell (This does not fit with cell theory).
Cell Basics
All cells have:
– a cell membrane,
– cytoplasm,
– genetic material (DNA).
There is a stark difference between cells i.e. are they
Prokaryotic or Eukaryotic
• Prokaryotic cells – no nucleus (e.g. bacteria)
• Eukaryotic cells - have nucleus (e.g.neutrophil)
Other variances:
– number and type of Organelles within the cell
– Shape of the cell
– function of the cell.
The Cell
Organelles
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Secretory vesicle
plasma membrane
Golgi complex
nuclear envelope
Nuclear envelope
Mitochondria
Cytoplasm
Nucleus
Nucleolus
Centriole
Granular endoplasmic reticulum
Agranular endoplasmic reticulum
Ribosome
Microtubule
Lysosome
The Cell
Cell components 1: Cytoplasm
Cytoplasm/Cytosol- This fluid like matter surrounds
the organelles
• This supports numerous microtubules that act like an
internal skeleton, forming ‘motorway’ routes for substances,
organelles and vesicles to travel
This allows for:
- communication between components of the cell
- communication between the cell and the external
environment
- microtubules form spindle apparatus involved in cell
division
Cytoskeleton
Cell Components 2: Plasma
membrane
The cell ‘plasma’ membrane
maintains the boundaries of the
cell
The Cell ‘Plasma’ Membrane
• An essential communication link between the cell and its
surrounding environment.
• Largely made up of phospholipid molecules
• Provides specific gateways for substances to pass through,
controlling the internal environment & the outflow of
substances manufactured in the cell
• Contains ‘markers’ that others cells can recognize
• Proteins within the phospholipid cell wall are essential; for
acceptance of water-soluble substances.
Detail of the Cell Membrane
Cell membrane proteins =special
• Part of them is Lipophilic (fat loving) which means that
they can interact with lipids. These proteins can act as:
• Transporters to carry substances through the cell wall
• Channels that allow substances though the cell
membrane
• Receptors that detect hormones and transmitter
substances
• Enzymes that catalyze specific reactions and
– Markers give the cell and identity.
– Cells of the same identity group together to form tissues types (to
discussed later)
Clinical relevance point
– Think about absorption of medicines into
cells-– Liposoluble drugs ‘diffuse’ though the
membrane very quickly because lipids are
attracted to a cell wall
Endocytosis and Exocytosis
Endocytosis
Exocytosis
Exocytosis
Transport through the cell wall
• ENDOCYTOSIS –A small part of the cell membrane
is drawn into the cell and the cell membrane then
joins with a vesicle from the outside to reform the
external boundaries of the cell. This tiny droplet
from the outside is then a part of the cell wall and
can be released into the cell
• EXOCYTOSIS -Little sacs of substances called
‘vesicles’ join with the cell wall. For this to happen,
the cell needs to take away the adjacent
phospholipid layer (by endocytosis) to make room
for the new part (the vesicle).
Cell Components 3:
Organelles & their functions
Organelles have specific functions;
-supporting the cell and as a whole, maintaining
its function
-distribution of organelles varies between cells,
depending on their function.
Nucleus
A double layer membrane containing DNA and RNA
- genetic codes.
Replication of parts of the body = depends on genetic coding
Codes = blueprint for the manufacture of proteins
These proteins form a part of cell structures and
tissues, enzymes, hormones, nucleic acids
Genetic codes - within the nucleus of the cell are
embedded within the DNA and RNA complexes
Protein synthesis occurs within the cell cytoplasm - you need to
understand this process and this is a part of your study.
The nucleus
Endoplasmic Reticulum ERConsists of membranes that
enclose amino acids and
enzymes.
Enzymes bring about
chemical reactions,
producing proteins and
lipids.
ER is where cellular waste
is broken down & converted
for re-use or excretion.
Rough ER has ribosomes
inserted into its membrane
Smooth ER does not have
ribosomes.
Ribosomes
Ribosomes are often called
the protein factories of the
cell
Ribosomes are tiny.
-found free in the cytoplasm or
attached to endoplasmic reticulum
a model of the two subunits that
make up a ribosome
The Golgi apparatus
A stack of membranous
sacs, associated with the
ER
Takes up products made
by the ER and may modify
them a little Packages products in
transport vesicles –
Packages are transported
inside or outside the cell.
Mitochondria
Originated from bacteriaContain their own DNA and self
replicate.
Essential for effective
energy production.
Convert substances like
glucose and fats to energy
that can be used by the
cells
(i.e. ATP)
Clinical Relevance point
If we fail to feed cells with e.g. glucose, then
energy will not be produced
• Imagine what would happen to our skin – as
these cells need energy to constantly make new
cells (to be discussed in future sessions)
• Without adequate feeding- would wounds heal?
Lysosomes
Digest materials:
Contain Enzymes (acid hydrolases)
that digest large molecules like
bacteria
Breakdown cell materials
Sometimes, things have to be
broken down and removed to
enhance the operating environment
of the cell.
'Pinocytosis' - cell drinking,
effectively breaking down the
bacteria
'Phagocytosis' cell eating
Peroxisomes
• Spherical vesicles enclosed is a membrane
• They contain several specific enzymes
• They are present in most cells
– particularly large active cells in the liver (think of a
substance detoxified by the liver……)
• They ‘oxidize’ toxic molecules, removing hydrogen
and transferring this to oxygen to form hydrogen
peroxide.
Examples of cells
Cell Specialisation
Cells become specialized to perform a
particular function within an organism, usually
as part of a tissue, e.g.:
Nerve cells to operate as part of the nervous
system
Skin cells for waterproof protection and protection
against
pathogens
Cells combine efforts in these tissue types to perform
a common cause.
Specialized cells
The task of the specialized cell will determine in
what way it is going to be specialized. e.g.
 Muscle cells are long and smooth in structure
 White Blood Cells contain powerful digestive
enzymes
 Specialized cells to detect light at the back of
the eye
In summary….
• The structural and functional and functional unit of living
material is the………..
• It contains functional subunits called………….
• Cell function depends on the presence of specific…………..
• Groups of similar cells that perform a similar function
are……………
• Structures that contain different tissues organised to
perform a general function are………………..
• Groups of organs that work together to carry out a general
function are…………….
Summary
In this session we reviewed:
1. Levels of organisation
2. Cell Theory
3. Cell structure
4. Organelles and their functions