Download Cell Structure - Action Duchenne

Cell Structure
Karl A. Bettelheim
Cell Structure
Some statistics about cells.
Estimated number of cells in the human body:
35 Trillion.
Estimated number of different types of cells in
the human body:
200.
But this estimate is considered much to low.
Cell Structure
Definition of a Cell.
A cell is a group of self sustaining
biochemical reactions, that are isolated from
the environment by a selectively permeable lipid
membrane. Among the key reactions are those t
hat maintain a stable intracellular concentration
of ions.
Cell Structure
Sizes of Cells.
Most plant and animal cells are visible only
under a microscope, with dimensions
between 1 and 100 micrometers
They contain many organelles, which are
distinct units of function.
Cell Structure
Contents of Cells.
Water
80%
Proteins
15%
Structural Proteins
Globular Proteins
Remainder
Lipids : Cellular membrane
Energy source
Carbohydrates
Energy source
Ions :potassium, magnesium, phosphate,
sulphate & bicarbonate.
Cell Structure
Organelles.
Within the cell are highly organized physical
structures – organelles- which carry out
specific functions.
Cell Structure
Organelles.
The Cell Nucleus.
Generally cells contain one nucleus, which
contains the DNA, which carries the code of
the proteins to be made by the cells. The DNA
code is read and exits the nucleus as
messenger RNA. Muscle cells have many
nuclei.
Cell Structure
Organelles.
The Nuclear Membrane/envelope.
These two membranes surround the nucleus.
They contain pores that regulate the entry and
exit of molecules.
Cell Structure
Organelles.
The Nucleolus .
The nucleoli are not surrounded by a nuclear
membrane. They contain RNA and protein
components.
Cell Structure
Organelles.
The Ribosomes(1).
There are many ribosomes in the cell. They
process the information in the messenger RNA
and thus produce the encoded protein, which
is then edited as required. The amount of a
given protein to be made is regulated. Only
proteins specifically required are made.
Cell Structure
Organelles.
The Ribosomes(2).
The ribosomes are large particles composed of
about 70 proteins arranged in two subunits.
They combine the amino acids into the
proteins as required by the cell.
Cell Structure
Organelles.
The Endoplasmic Reticulum (ER).
The ER forms a network of membranes within
the cell. There are two types:
1) The rough ER.
2) The smooth ER.
Cell Structure
Organelles.
The Rough ER (1).
The rough ER carries surface ribosomes.
On these proteins are synthesized and they
enter the lumen of the ER and they are either
distributed within the cell or secreted to other
cells.
Cell Structure
Organelles.
The Smooth ER (2).
The smooth ER does not carry ribosomes.
On these fatty acids are synthesized and they
regulate the cellular levels of Calcium ions,
whi h i tur regulate a y of the ell’s
activities.
Cell Structure
Organelles.
The Golgi apparatus.
These membranous sacs sort and modify
proteins arriving from the granular ER,
packaging them into vesicles before sending
them to other organelles or secreting them.
Cell Structure
Organelles.
The Mitochondria.
These are double-membraned elongated
ovoid elongated structures. The outer
membrane is smooth and the inner is folded
into tubes to increase surface area. Inside is
DNA for mitochondrial protein synthesis. They
make energy available to the cell.
Cell Structure
Organelles.
The Lysosomes.
These single-membraned oval organelles
contain highly acidic digestive enzymes that
break down bacteria, cell debris and dead
organelles.
Cell Structure
Organelles.
The Peroxysomes.
These single-membraned oval organelles
destroy the highly toxic compound hydrogen
peroxide (H2O2), which is a by-product of
some cellular activities. In the liver and kidney
cells manufacture H2O2 and use it to destroy
various ingested molecules.
Cell Structure
Organelles.
The Filaments.
The cytoplasm of most cells contains filaments
–the cytoskeleton-, whi h ai tai the ell’s
shape and produce cell movement.
Cell Structure
Cell Structure
Cell Structure
Similar to a
bacterium.
Muscle Cell Structure
Muscle Cell Structure
Nerve-fibre
connection
Muscle Cell Structure
Muscle Cells.
The basis of muscle movement is the
interaction of two entities:
Actin
Myosin
These operate within
a structure called the
Sarcomere.
Muscle Cells.
Nomenclature
Muscle Cell
Other Organismal Cells
Sarcoplasm
Cytoplasm
Sarcoplasmic Reticulum
Smooth Endoplasmic Reticulum
Sarcosome
Mitochondrion
Sarcolemma
Cell Membrane
Muscle Cells.
A sarcomere is the basic unit of striated
muscle tissue. Skeletal muscles are
composed of tubular muscle cells
(myocytes called muscle fibers) which are
formed in a process known as myogenesis.
Muscle fibers are composed of tubular
myofibrils.
Muscle Cells.
Muscle Cells.
Muscle contraction based on sliding filament hypothesis.
Muscle Cells.
The Actin filament.
Tropomysin and troponin are part of the actin filament.
Muscle Cells.
The Actin filament.
The binding of the myosin heads to the muscle actin is a highly regulated process.
The thin filament is made of actin, tropomyosin, and troponin. The contraction of
skeletal muscle is triggered by nerve impulses that in turn stimulate the release of Ca2+
Troponin is attached to the protein tropomyosin and lies within the groove,
between actin filaments in muscle tissue. In a relaxed muscle, tropomyosin
blocks the attachment site for the myosin crossbridge, thus preventing contraction.
Muscle Cells.
Dystrophin
a-DG Dystroglycan b-SG Sarcoglycan
N Nitric oxide synthase
ST Syntrophin
a-, b- DG & SG:
Dystroglycans & Sarcoglycan are glycosilated proteins in the surface membrane.
NOS: Nitric oxide synthase synthesizes nitric oxide.
ST: Syntrophin binds signalling molecules, such as NOS to dystrophin and dystrobrevin.
Muscle Cells.
Muscle Cells (1)
Dystrophin is a protein located between the
sarcolemma and the outermost layer of
myofilaments in the muscle fiber (myofiber). It is
a cohesive protein, linking actin filaments to
another support protein that resides on the
inside surface of each muscle fi er’s plasma
membrane (sarcolemma). This support protein
on the inside surface of the sarcolemma in turn
links to two other consecutive proteins for a total
of three linking proteins. The final linking protein
is attached to the fibrous endomysium of the
entire muscle fiber.
Muscle Cells (2)
Dystrophin supports muscle fiber strength, and the
absence of dystrophin reduces muscle stiffness,
increases sarcolemmal deformability, and compromises
the mechanical stability of costameres and their
connections to nearby myofibrils; as shown in recent
studies where biomechanical properties of the
sarcolemma and its links through costameres to the
contractile apparatus were measured, and helps to
prevent muscle fiber injury. Movement of thin
filaments (actin) creates a pulling force on the
extracellular connective tissue that eventually becomes
the tendon of the muscle.
Muscle Cells
Thank
you
for
your
Attention.