Transcript the cell - Learning Central

Introduction to the Cell
Copyright CSAN (2005), Images used with permission
The Cell
Objectives
• 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
Objectives
• Describe the basic structure of a Eukaryotic cell
– Briefly describe the cytoplasm
– Describe 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 the Cell Theory
• Viruses.
According to the Cell Theory we have to say
they are not alive because a virus is not a cell.
Viruses are made protein & nucleic acid, but
have no membranes, nucleus, or protoplasm.
They appear to be alive when they reproduce
after infecting a host cell. (This will be
discussed in later sessions)
• Mitochondria. These cell organelles (small
structures inside the cell) have their own
genetic material & reproduce independently
from the rest of the cell
Cell Basics
• The Prokaryotic-Eukaryotic difference
• Prokaryotic cells - no nucleus (e.g. bacteria)
• Eukaryotic cells - have nucleus (e.g.
neutrophil)
• All cells have
– a cell membrane,
– cytoplasm,
– genetic material (DNA).
• Other variances– Organelles present in the cell, the shape of the cell, or
the function of the cell.
The Cell
organelles
•
•
•
•
•
•
•
•
•
•
•
•
•
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
• Cytoplasm- a jelly like matrix within the cell
– Includes structures called organelles (little
organs)
– Fluid like cytosol surrounds the organelles
Numerous microtubules within the cytosol act like a sort of
internal skeleton, forming ‘motorway’ routes for substances,
organelles and vesicles to travel
Allows for:
- communication between components of the cell
- communication between the cell and the external
environment
- microtubules form spindle apparatus involved in cell
division
The cytoskeleton
cell wall
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 are 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 that 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 can ‘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).
ORGANELLES & THEIR
FUNCTIONS
• Organelles within the cell have specific
functions.
-They support the cell and as a whole,
maintain its function
-The distribution of organelles varies between
cell, 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
that form a part of cell structures and tissues,
enzymes, hormones, nucleic acids
Genetic codes - contained within the nucleus of the
cell 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 to be
discussed during Module 2
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
(protein synthesis
is covered in module 2)
They are tiny, and can be
found free in the cytoplasm
or attached to endoplasmic
reticulum
This diagram shows a model of the
two subunits that make up a
ribosome
The Golgi apparatus
A stack of
membranous sacs,
associated with the ER
It takes up the products
made by the ER and may
modify them a little Essentially packages the
products in transport
vesicles to transport to
somewhere inside or
outside the cell.
Mitochondria
Originated from bacteriacontain their own DNA and
self replicate.
Essential for effective
energy production.
They convert substances
like glucose and fats to a
form of energy that can be
used by the cells (i.e. ATPthis will be discussed later)
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
module 2)
• 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
• Peroxisomes are membrane enclosed
spherical vesicles that contain several
specific enzymes
• Peroxisomes- present in most cells
– particularly large and active in the liver (think of a
substance detoxified by the liver……)
• Peroxisomes ‘oxidize’ toxic molecules,
removing hydrogen and transferring it to
oxygen to form hydrogen peroxide
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
•
1.
2.
3.
4.
In this session we reviewed:
Levels of organisation
Cell Theory
Cell structure
Organelles and their functions