The document summarizes key aspects of the cytoskeleton, focusing on actin filaments. It describes how actin filaments: 1) maintain cell shape and generate force for cell movements through polymerization and depolymerization; 2) integrate cells through attachments to cell adhesions; and 3) produce movements within cells and at the cell membrane through interactions with myosin motor proteins. Accessory proteins regulate actin dynamics by capping, bundling, severing, and crosslinking filaments.
Cytoskeleton - microtubules ,microfilaments and intermediate filamentsBIOTECH SIMPLIFIED
The cytoskeleton is a structure that helps cells maintain their shape and internal organization, and it also provides mechanical support that enables cells to carry out essential functions like division and movement. There is no single cytoskeletal component. Rather, several different components work together to form the cytoskeleton.
Cytoskeleton - microtubules ,microfilaments and intermediate filamentsBIOTECH SIMPLIFIED
The cytoskeleton is a structure that helps cells maintain their shape and internal organization, and it also provides mechanical support that enables cells to carry out essential functions like division and movement. There is no single cytoskeletal component. Rather, several different components work together to form the cytoskeleton.
Structure and functions of endoplasmic reticulumICHHA PURAK
The presentation consists of 57 slides,describes following heads
• DISCOVERY
• INTRODUCTION
• BIOGENESIS OF ER
• ISOLATION OF MICROSOMES FROM E R
• STRUCTURE
• COMPONENTS OF ER
CISTERNAE
VESICLES
TUBULES
• MAIN FUNCTION OF ER
• TYPES OF ENDOPLASMIC RETICULUM
• SMOOTH ENDOPLASMIC RETICULUM (SER)
• FUNCTIONS OF SER
• ROUGH ENDOPLASMIC RETICULUM (RER)
• FUNCTIONS OF RER
• SUMMARY
• REFERENCES
• QUESTIONS
Nucleus: Structure and function
nuclear membrane
nuclear lamins
Nuclear pore complexe
nuclear matrix, composition and its role
cajal bodies
SFCs
nuclear speckles
PML bodies
Nucleolus
Actin filaments, usually in association with myosin, are responsible for many types of cell movements. Myosin is the prototype of a molecular motor—a protein that converts chemical energy in the form of ATP to mechanical energy, thus generating force and movement. The most striking variety of such movement is muscle contraction, which has provided the model for understanding actin-myosin interactions and the motor activity of myosin molecules. However, interactions of actin and myosin are responsible not only for muscle contraction but also for a variety of movements of nonmuscle cells, including cell division, so these interactions play a central role in cell biology. Moreover, the actin cytoskeleton is responsible for the crawling movements of cells across a surface, which appear to be driven directly by actin polymerization as well as actin-myosin interactions.
Describes the plasma membrane in detail, explains the each major component with its functions.
Transport mechanism across the cell is covered with detailed explanation with examples.
by Dr. N.Sivaranjani, MD
Details of cytoskeleton element-microtubule. The Microtubule associated protein-type and function, Treadmilling and dynamic instability, Structure of cilia and flagella
Structure and function of plasma membrane 2ICHHA PURAK
The presentation consists of 72 slides,describes following heads
DEFINITION : STRUCTURE OF PLASMA MEMBRANE
COMPONENTS OF PLASMA MEMBRANE ( (BIOCHEMICAL PROPERTIES)
LIPID BILAYER
PROTEINS
CARBOHYDRATES
CHOLESTEROL
MODELS EXPLAINING STRUCTURE OF BIO MEMBRANE
FLUID MOSAIC MODEL
MOBILITY OF MEMBRANE
GLYCOCALYX : GLYCOPROTEINS AND GLYCOLIPIDS
TRANSPORT OF IONS AND MOLECULES ACROSS PLASMA MEMBRANE
FUNCTIONS OF PLASMA MEMBRANE
DIVERSITY OF CELL MEMBRANES
SITE OF ATPASE ION CARRIER CHANNELS AND PUMPS-RECEPTORS
Structure and functions of endoplasmic reticulumICHHA PURAK
The presentation consists of 57 slides,describes following heads
• DISCOVERY
• INTRODUCTION
• BIOGENESIS OF ER
• ISOLATION OF MICROSOMES FROM E R
• STRUCTURE
• COMPONENTS OF ER
CISTERNAE
VESICLES
TUBULES
• MAIN FUNCTION OF ER
• TYPES OF ENDOPLASMIC RETICULUM
• SMOOTH ENDOPLASMIC RETICULUM (SER)
• FUNCTIONS OF SER
• ROUGH ENDOPLASMIC RETICULUM (RER)
• FUNCTIONS OF RER
• SUMMARY
• REFERENCES
• QUESTIONS
Nucleus: Structure and function
nuclear membrane
nuclear lamins
Nuclear pore complexe
nuclear matrix, composition and its role
cajal bodies
SFCs
nuclear speckles
PML bodies
Nucleolus
Actin filaments, usually in association with myosin, are responsible for many types of cell movements. Myosin is the prototype of a molecular motor—a protein that converts chemical energy in the form of ATP to mechanical energy, thus generating force and movement. The most striking variety of such movement is muscle contraction, which has provided the model for understanding actin-myosin interactions and the motor activity of myosin molecules. However, interactions of actin and myosin are responsible not only for muscle contraction but also for a variety of movements of nonmuscle cells, including cell division, so these interactions play a central role in cell biology. Moreover, the actin cytoskeleton is responsible for the crawling movements of cells across a surface, which appear to be driven directly by actin polymerization as well as actin-myosin interactions.
Describes the plasma membrane in detail, explains the each major component with its functions.
Transport mechanism across the cell is covered with detailed explanation with examples.
by Dr. N.Sivaranjani, MD
Details of cytoskeleton element-microtubule. The Microtubule associated protein-type and function, Treadmilling and dynamic instability, Structure of cilia and flagella
Structure and function of plasma membrane 2ICHHA PURAK
The presentation consists of 72 slides,describes following heads
DEFINITION : STRUCTURE OF PLASMA MEMBRANE
COMPONENTS OF PLASMA MEMBRANE ( (BIOCHEMICAL PROPERTIES)
LIPID BILAYER
PROTEINS
CARBOHYDRATES
CHOLESTEROL
MODELS EXPLAINING STRUCTURE OF BIO MEMBRANE
FLUID MOSAIC MODEL
MOBILITY OF MEMBRANE
GLYCOCALYX : GLYCOPROTEINS AND GLYCOLIPIDS
TRANSPORT OF IONS AND MOLECULES ACROSS PLASMA MEMBRANE
FUNCTIONS OF PLASMA MEMBRANE
DIVERSITY OF CELL MEMBRANES
SITE OF ATPASE ION CARRIER CHANNELS AND PUMPS-RECEPTORS
Check out overview of dental implants and Understand the facts about dental implants treatment. How successful are dental implants? Identify the approximated costs of dental implants in various countries.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
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• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
DevOps and Testing slides at DASA ConnectKari Kakkonen
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- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
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Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
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All of this illustrated with link prediction over knowledge graphs, but the argument is general.
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The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
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Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
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https://arxiv.org/abs/2306.08302
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1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
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Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
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Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
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💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
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👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
2. CYTOSKELETON
The cytoskeleton is a network of connected
filaments and tubules extending from the
nucleus to the plasma membrane.
Dynamic: dismantles in one spot and
reassembles in another to change cell shape
It maintains the shape of the cell- fibers act
like a geodesic dome to stabilize and balance
opposing forces.
Anchor organelles
Move the cell and control internal movement
of structures.
3. Motility of cells is determined by special
organelles for locomotion.
Internal movements
(cytoplasmic
streaming or cyclosis)
by cytoskeleton
components.
4.
5. The ACTIN cytoskeletal
machinery (red) is
responsible for maintaining
cell shape and generating
force for movements.
Polymerization and
depolymerization of actin
filaments (1) drives the
membrane forward,
whereas actin cross-linking
proteins organize bundles
and networks of filaments
(2) that support overall cell
shape. Movements within
the cell and contractions at
the cell membrane (3) are
produced by myosin motor
proteins. The actin (red) and
intermediate filament
(purple) cytoskeletons
integrate a cell and its
contents with other cells in
tissues (4) through
attachments to cell
adhesions. Another type of
intermediate filament, the
nuclear lamins (5) are
responsible for maintaining
the structure of the nucleus.
6. Mechanical properties of Networks composed of
actin, tubulin, and microtubules, actin filaments, or an
intermediate filament called
intermediate vimentin, all at equal concentration,
filament polymers. were exposed to a shear force in a
viscometer, & the resulting degree
of stretch was measured. The
results show that microtubule
networks are strong, rigid hollow
tubes that are easily deformed but
rupture (red starburst) and begin to
flow without limit when stretched
beyond 150% of their original
length. Actin filament networks are
much more rigid, but they also
rupture easily. Intermediate filament
networks, by contrast, are not only
easily deformed, but they withstand
large stresses and strains without
rupture; they are thereby well suited
to maintain cell integrity.
7. Actin is encoded by a large, highly conserved
gene family. Humans have 6 actin genes, which
encode isoforms of the protein.
Although differences among isoforms seem
minor, the isoforms have different functions: α-
actin is associated with contractile structures;
γ-actin accounts for filaments in stress fibers;
and ß-actin is at the front, or leading edge, of
moving cells where actin filaments polymerize.
Sequencing of actins from different sources
has revealed that they are among the most
conserved proteins in a cell, comparable with
histones, the structural proteins of chromatin.
8. They form a dense complex web under the cell membrane. In
intestinal cell microvilli, they act to shorten the cell
In plant cells, actin filaments form tracts along which
chloroplasts circulate.
Involved in cell rigidity, tensile strength and resilience,
cellular movement (pseudopodia and mesenchyme cell
migration, platelet activation)
Pseudopodia are associated with actin near the moving edge
of the cell. Actin filaments move by interacting with myosin
changing the configuration to pull the actin filament forward.
Similar action accounts for pinching off cells during cell
division and for amoeboid movement.
Other arrangements of microfilaments in association with
accessory proteins are possible. Ex: contractile rings of cell
division; parallel bundles are found in stress fibers of
fibroblasts, filopodia and other cell projections; gels of short
randomly oriented filaments are found in egg cortical
regions.
10. All cytoskeleton types
form as helical
assemblies of subunits
that self-associate using
a combination of end-to-
end and side-to-side
protein contacts.
They grow fastest from
the plus end than the
minus end of the
assembly.
F-actin is polymerized
through addition of
globular actin or G-actin
monomers at the
growing (+) end, bearing
a stabilizing ATP cap.
11. Nucleation of new actin
filaments (red) is mediated
by ARP complexes (orange)
at the front of the web.
Newly formed filaments are
thereby attached to the
sides of preexisting
filaments. As these
elongate, they push the
plasma membrane forward.
The actin filament plus ends
will become protected by
capping proteins (blue),
preventing further assembly
or disassembly from the old
plus ends at the front of the
array. Hydrolysis of ATP
bound to the polymerized
actin subunits promotes
depolymerization at the rear
end of the actin complex by
a depolymerizing protein
(green). The spatial
separation of assembly and
disassembly allows the
network as a whole to move
forward at a steady rate.
12. Treadmilling. Actin subunits can flow through the filaments by
attaching preferentially to the (+) end and dissociating
preferentially from the (-) end of the filament. Removal of
monomers at the (–) end and addition of monomers at the (+)
end leaves the filaments at the same overall length. The oldest
subunits in a treadmilling filament lie at the (-) end. Treadmilling
occurs at intermediate concentrations of free subunits.
13. Microfilaments in a cell. A crawling cell with 3 areas showing the
arrangement of actin filaments. The actin filaments are shown in red,
with arrowheads pointing toward the plus end. Stress fibers are
contractile and exert tension. Filopodia are spike-like projections of the
plasma membrane that allow a cell to explore its environments. The
cortex underlies the plasma membrane.
14. A model of how forces generated in
the actin-rich cortex move a cell
forward.
The actin-polymerization-
dependent protrusion and firm
attachment of a lamellipodium at
the leading edge of the cell moves
the edge forward (green arrows at
front) and stretches the actin
cortex. Contraction at the rear of
the cell propels the body of the cell
forward (green arrow at back) to
relax some of the tension (traction).
New focal contacts are made at the
front, and old ones are
disassembled at the back as the cell
crawls forward. The same cycle can
be repeated, moving the cell
forward in a stepwise fashion.
Alternatively, all steps can be tightly
coordinated, moving the cell
forward smoothly. The newly
polymerized cortical actin is shown
in red.
15. Platelet activation. (A) Platelet activation is a controlled sequence of actin
filament severing, uncapping, elongation, recapping, and cross-linking that creates
a dramatic shape change in the platelet. (B) SEM of platelets prior to activation. (C)
An activated platelet with its large spread lamellipodium. (D) An activated platelet
at a later stage than the one shown in C, after myosin II-mediated contraction.
16. Several actin-binding proteins influence deployment of
filaments in the cytoplasm:
Profilin binds to G-actin
monomers to regulate
polymerization
Capping protein limits
length increase by binding
to the end of actin filament
Fimbrin binds adjacent actin
filaments to form bundles
Filamin stabilizes filament 3-D network by
intersecting with microfilaments
Gelsolin breaks filament into shorter segments by
inserting between subunits
Vinculin & actinin mediate binding of actin to cell
membrane at intercellular junctions and cell base.
17.
18. The modular structures of four actin-cross-linking proteins
Each of the proteins shown has two actin-binding sites (red) that are
related in sequence. Fimbrin has two directly adjacent actin-binding sites,
so that it holds its two actin filaments very close together (14 nm apart),
aligned with the same polarity. The two actin-binding sites in α-actinin are
separated by a spacer around 30 nm long, so that it forms more loosely
packed actin bundles. Filamin has two actin-binding sites with a Vshaped
linkage between them, so that it cross-links actin filaments into a network
with the filaments oriented almost at right angles to one another. Spectrin
is a tetramer of two α and two ß subunits, and the tetramer has two actin-
binding sites spaced about 200 nm apart
19. Twisting of an actin filament induced by cofilin.
(A) Three dimensional reconstruction from cryo-EM of filaments made of
pure actin. The bracket shows the span of two turns of the actin helix.
(B) Reconstruction of an actin filament coated with cofilin, which binds in
a 1:1stoichiometry to actin subunits all along the filament. Cofilin is a
small protein (14 kilodaltons) compared to actin (43 kilodaltons), and so
the filament appears only slightly thicker. The energy of cofilin binding
serves to deform the actin filament lattice, twisting it more tightly so that
the distance spanned by two turns of the helix is reduced.
20. Filamin cross-links actin filaments into a three-dimensional
network with the physical properties of a gel
(A) Each filamin homodimer is about 160 nm long when fully
extended and forms a flexible, high-angle link between two
adjacent actin filaments. (B) A set of actin filaments cross-linked
by filamin forms a mechanically strong web or gel.
21. INTERMEDIATE FILAMENTS
Are structurally similar but biochemically distinct,
with diameters intermediate between microtubules
and microfilaments (about 10 nm).
They associate with polypeptides fillagrin (binds to
keratin), plectin (links vimentin), and synamin (also
links vimentin, but found in muscle).
5 types are:
1. Glial filaments – found in non-neural cells of the
CNS: astrocytes, oligodendrocytes, microglia.
2. Keratin filaments – characteristic of epithelial
cells; called tonofilaments are often associated
with desmosomes at the cell surface. They
participate in the formation of keratin in
keratinizing epithelia.
22. 3.Desmin – characteristic of smooth, striated & cardiac
muscle; keep sarcomeres of neighboring myofibrils in
register across the width of the fiber; link Z-bands of
peripheral myofibrils to the sarcolemma; ensures uniform
distribution of tensile strength throughout the muscle cell.
4.Vimentin – abundant in fibroblasts and mesenchymal
derivatives, in bundles or randomly oriented in a network
throughout the cytoplasm.
5.Neurofilaments – present in nerve cell processes with a
cytoskeletal function; helps to maintain the gel state of the
axoplasm; involved in intracellular metabolite transport.
23. A model of intermediate
filament construction
The monomer shown in (A)
pairs with an identical
monomer to form a dimer (B)
in which the conserved
central rod domains are
aligned in parallel and
wound together into a coiled
coil. (C) Two dimers then line
up side by side to form the
tetramer soluble subunit of
intermediate filaments. (D)
Within each tetramer, the 2
dimers are offset with
respect to one another, thereby allowing it to associate with
another tetramer. (E) In the final 10-nm rope-like filament,
tetramers are packed together in a helical array, which has 16
dimers in cross-section. Half of these dimers are pointing in each
direction.
24. Keratin filaments in
epithelial cells
• Immunofluorescence
micrograph of the network
of keratin filaments (green)
in a sheet of epithelial
cells in culture.
• The filaments in each cell
are indirectly connected to
those of its neighbors by
desmosomes.
• A 2nd protein (blue) has
been stained to reveal the
location of the cell
boundaries.
25. Blistering of the skin caused by a mutant keratin gene.
A mutant gene encoding a keratin protein was expressed in a transgenic
mouse. The defective protein assembles with the normal keratins and
thereby disrupts the keratin filament network in the basal cells of the
skin. LM of cross sections of normal (A) and mutant (B) skin show that
the blistering results from the rupturing of cells in the basal layer of the
mutant epidermis (small red arrows). (C) Cells in the basal layer of the
mutant epidermis, as observed by EM. As indicated by the red arrow, the
cells rupture between the nucleus & the hemidesmosomes, which
connect the keratin filaments to the underlying basal lamina.
26. Two types of intermediate filaments in cells of the nervous system.
(A) Freeze-etch EM image of neurofilaments in a nerve cell axon, showing
the extensive cross-linking through protein cross-bridges an arrangement
believed to give this long cell process great tensile strength. The cross-
bridges are formed by the long, nonhelical extensions at the C-terminus of
the largest neurofilament protein (NF-H). (B) Freeze-etch image of glial
filaments in glial cells, showing that these intermediate filaments are
smooth and have few cross-bridges. (C) Conventional EM of a cross
section of an axon showing the regular side-to-side spacing of the
neurofilaments, which greatly outnumber the microtubules.