Cellular membranes are fluid mosaics of phospholipids and proteins that allow selective permeability. The fluid mosaic model proposes that membranes are composed of a phospholipid bilayer with integral and peripheral proteins embedded within. Membrane proteins carry out critical functions like transport, signaling, and cell recognition through mechanisms like passive diffusion, facilitated diffusion, active transport, and cotransport.
My 2nd lecture about biological membranes, especially focusing on cell membrane. Lecture delivered on 19-Jan-2018 to First year MBBS students at Bannu Medical College.
My 2nd lecture about biological membranes, especially focusing on cell membrane. Lecture delivered on 19-Jan-2018 to First year MBBS students at Bannu Medical College.
IT IS PPT ABOUT CELL MEMBRANE AFSHADFBHJADFKJDFBHJADFBHJDAFJHDFBVHCDBHJDJHDFSBHDFSJDFSHBJDFABHJDFSHJHDFSBJDFSBJDFSHJKDSFHJDFASKHFDSHJDFSKHKHKHFDSKHDFSKHDFSKHKDFHSKHDFSKHFSKHDFSKH
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
1. Chapter 7
Membrane Structure and Function
In 1972, Singer and Nicolson proposed that the membrane is a
mosaic of proteins dispersed within a phospholipid bilayer, with only the
hydrophilic regions exposed to water. The fluid mosaic model states
that a membrane is a fluid structure with a “mosaic” of various proteins
embedded in it.
Function: The plasma
membrane exhibits selective
permeability, allowing some
substances to cross it more
easily than others
2. Cellular membranes are fluid
mosaics of lipids and proteins
• Membranes have two asymmetric leaflets
• Each leaflet has lateral fluidity
• Phospholipids are the most abundant lipid in the
plasma membrane (sphingolipids, glycolipids,
cholesterol also)—note: cholesterol only in animals &
some bacteria, not in plants
• Phospholipids are amphipathic molecules, containing
hydrophobic and hydrophilic regions
• The fluid mosaic model states that a membrane is a
fluid structure with a “mosaic” of various globular
proteins embedded in it—both integral and peripheral
4. Figure 7.3
Glyco-
protein Carbohydrate Glycolipid
EXTRACELLULAR
SIDE OF
MEMBRANE
Microfilaments
of cytoskeleton
Fibers of extra-
cellular matrix (ECM)
Cholesterol
Peripheral
proteins Integral
protein CYTOPLASMIC
SIDE OF
MEMBRANE
•Peripheral proteins usually on inner side of membrane & held their by ionic (with
charged lipid head) or hydrophobic (with a second hydrophobic protein) interaction
•Hydrophobic & hydrophilic regions of integral proteins
•Sugars usually on exterior leaflet; proteoglycans too
5. • Freeze-fracture studies of the plasma
membrane supported the fluid mosaic model
• Freeze-facture is a specialized preparation
technique that splits a membrane along the
middle of the phospholipid bilayer
7. Lateral movement
(~107
times per second)
Flip-flop
(~ once per month)
Movement of phospholipids
Rarely does a molecule flip-flop transversely across the membrane
8. LE 7-5b
ViscousFluid
Unsaturated hydrocarbon
tails with kinks
Saturated hydro-
carbon tails
•As temperatures cool, membranes switch from a fluid state to a
solid state
•The temperature at which a membrane solidifies depends on the
types of lipids
•Membranes rich in unsaturated fatty acids are more fluid than
those rich in saturated fatty acids
•Membranes must be fluid to work properly; they are usually
about as fluid as salad oil
9. Cholesterol
•The steroid cholesterol has different effects on
membrane fluidity at different temperatures
•At warm temperatures (such as 37°C), cholesterol
restrains movement of phospholipids
•At cool temperatures, it maintains fluidity by
preventing tight packing
11. • Six major functions of membrane proteins
– Transport
– Enzymatic activity
– Signal transduction
– Cell-cell recognition
– Intercellular joining
– Attachment to the cytoskeleton and
extracellular matrix (ECM)
12. Figure 7.7
(a) Transport (b) Enzymatic
activity
(c) Signal
transduction
(d) Cell-cell
recognition
(e) Intercellular
joining
(f) Attachment to
the cytoskeleton
and extracellular
matrix (ECM)
Enzymes
ATP
Signaling
molecule
Receptor
Signal transduction
Glyco-
protein
13. 1. Which of the following best describes the structure of a
biological membrane?
a. two layers of phospholipids with proteins embedded
between the two layers
b. a mixture of covalently linked phospholipids and proteins
that determines which solutes can cross the membrane
and which cannot
c. two layers of phospholipids with proteins either spanning
the layers or on the surface of the layers
d. a fluid structure in which phospholipids and proteins move
freely between sides of the membrane
e. two layers of phospholipids (with opposite orientations of
the phospholipids in each layer) with each layer covered
on the outside with proteins
14. 1. Which of the following best describes the structure of a
biological membrane?
a. two layers of phospholipids with proteins embedded
between the two layers
b. a mixture of covalently linked phospholipids and proteins
that determines which solutes can cross the membrane
and which cannot
c. two layers of phospholipids with proteins either spanning
the layers or on the surface of the layers
d. a fluid structure in which phospholipids and proteins move
freely between sides of the membrane
e. two layers of phospholipids (with opposite orientations of
the phospholipids in each layer) with each layer covered
on the outside with proteins
15. Sidedness of
Membranes
•Membranes have distinct
inside and outside faces
•The asymmetrical
distribution of proteins,
lipids and associated
carbohydrates in the
plasma membrane is
determined when the
membrane is built by the
ER and Golgi apparatus
Transmembrane
glycoproteins Secretory
protein
Golgi
apparatus
Vesicle
Attached
carbohydrate
ER
lumen
Glycolipid
Transmembrane
glycoprotein
Plasma membrane:
Cytoplasmic face
Extracellular face
Membrane
glycolipid
Secreted
protein
16. The Permeability of the Lipid
Bilayer
• Hydrophobic (nonpolar) molecules, such as
hydrocarbons, can dissolve in the lipid bilayer
and pass through the membrane rapidly
• Polar molecules, such as sugars, do not
cross the membrane easily
View Membrane Transport Video
17. Transport Proteins
• Transport proteins allow passage of hydrophilic
substances across the membrane
• Some transport proteins, called channel proteins, have
a hydrophilic channel that certain molecules or ions
can use as a tunnel
• Channel proteins called aquaporins facilitate the
passage of water
• Other transport proteins, called carrier proteins, bind
to molecules and change shape to shuttle them
across the membrane
• A transport protein is specific for the substance it
moves
18. Passive transport is diffusion of a
substance across a membrane with
no energy investment
• Diffusion is the tendency for molecules to
spread out evenly into the available space
• Although each molecule moves randomly,
diffusion of a population of molecules may
exhibit a net movement in one direction
• At dynamic equilibrium, as many molecules
cross one way as cross in the other direction
19. Figure 7.10
Molecules of dye Membrane (cross section)
WATER
(a) Diffusion of one solute
(b) Diffusion of two solutes
Net diffusion Net diffusion
Net diffusionNet diffusion
Net diffusion Net diffusion
Equilibrium
Equilibrium
Equilibrium
20. Effects of Osmosis on Water
Balance
• Osmosis is the diffusion of water across a
selectively permeable membrane
• The direction of osmosis is determined by a
difference in total solute concentration (but
pressure, gravity, matrix can influence)
• Water diffuses across a membrane from the
region of lower solute concentration (higher
water potential) to the region of higher solute
concentration (lower water potential)
21. Figure 7.11
Lower concentration
of solute (sugar)
Higher concentration
of solute
More similar
concentrations of solute
Sugar
molecule
H2O
Selectively
permeable
membrane
Osmosis
Selectively permeable
membrane: sugar
molecules cannot pass
through pores, but
water molecules can
22. Water Balance of Cells Without
Walls
• Tonicity is the ability of a solution to cause a
cell to gain or lose water
• Isotonic solution: solute concentration is the
same as that inside the cell; no net water
movement across the plasma membrane
• Hypertonic solution: solute concentration is
greater than that inside the cell; cell loses
water
• Hypotonic solution: solute concentration is less
than that inside the cell; cell gains water
24. Water Balance of Cells with
Walls
• Cell walls help maintain water balance
• A plant cell in a hypotonic solution swells until the
wall opposes uptake; the cell is now turgid (firm)
• If a plant cell and its surroundings are isotonic,
there is no net movement of water into the cell; the
cell becomes flaccid (limp), and the plant may wilt
• In a hypertonic environment, plant cells lose water;
eventually, the membrane pulls away from the
wall, a usually lethal effect called plasmolysis
Video: PlasmolysisVideo: Plasmolysis
25. LE 7-14
Filling vacuole
50 µm
50 µm
Contracting vacuole
The protist Paramecium, which is hypertonic to its pond water environment, has a
contractile vacuole that acts as a pump
26. 2. Which of the following statements about osmosis is
correct?
a. If a cell is placed in an isotonic solution, more water will
enter the cell than leaves the cell.
b. Osmotic movement of water into a cell would likely occur
if the cell accumulates water from its environment.
c. The presence of aquaporins (proteins that form water
channels in the membrane) should speed up the process
of osmosis.
d. If a solution outside the cell is hypertonic compared to the
cytoplasm, water will move into the cell by osmosis.
e. Osmosis is the diffusion of water from a region of lower water
concentration to a region of higher water concentration.
27. 2. Which of the following statements about osmosis is
correct?
a. If a cell is placed in an isotonic solution, more water will
enter the cell than leaves the cell.
b. Osmotic movement of water into a cell would likely occur
if the cell accumulates water from its environment.
c. The presence of aquaporins (proteins that form water
channels in the membrane) should speed up the process
of osmosis.
d. If a solution outside the cell is hypertonic compared to the
cytoplasm, water will move into the cell by osmosis.
e. Osmosis is the diffusion of water from a region of lower water
concentration to a region of higher water concentration.
28. Facilitated Diffusion: Passive
Transport Aided by Proteins
• In facilitated diffusion, transport proteins speed
movement of molecules across the plasma
membrane
• Channel proteins provide corridors that allow a
specific molecule or ion to cross the membrane
• Carrier proteins undergo a subtle change in
shape that translocates the solute-binding site
across the membrane
29. Figure 7.14
(a) A channel
protein
(b) A carrier protein
Carrier protein
Channel protein Solute
Solute
EXTRACELLULAR
FLUID
CYTOPLASM
30. Active transport uses energy to
move solutes against their gradients
• Facilitated diffusion is still passive because
the solute moves down its concentration
gradient
• Some transport proteins, however, can move
solutes against their concentration gradients
31. The Need for Energy in Active
Transport
• Active transport moves substances against
their concentration gradient
• Active transport requires energy, usually in the
form of ATP
• Active transport is performed by specific
proteins embedded in the membranes
• Active transport allows cells to maintain
concentration gradients that differ from their
surroundings
• The sodium-potassium pump is one type of
active transport system
32. Figure 7.15
EXTRACELLULAR
FLUID
CYTOPLASM
1 2
5
6
4
3
[Na+
] low
[K+
] high
[Na+
] high
[K+
] low
Na+
K+
K+
K+
K+
K+
K+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
ATP
ADP
P
P
P
i
P
Cytoplasmic Na+
bonds to
the sodium-potassium pump
Na+
binding stimulates
phosphorylation by ATP.
Phosphorylation causes
the protein to change its
conformation, expelling Na+
to the outside.
Extracellular K+
binds
to the protein, triggering
release of the phosphate
group.
Loss of the phosphate
restores the protein’s
original conformation.
K+
is released and Na+
sites are receptive again;
the cycle repeats.
34. Maintenance of Membrane
Potential by Ion Pumps
• Membrane potential is the voltage difference
across a membrane (differences in the
distribution of positive and negative ions across a
membrane)
• Two combined forces, collectively called the
electrochemical gradient, drive the diffusion of
ions across a membrane:
– A chemical force (the ion’s concentration
gradient)
– An electrical force (the effect of the membrane
potential on the ion’s movement)
36. Cotransport: Coupled Transport by
a Membrane Protein
• Cotransport occurs when active transport of a
solute indirectly drives transport of another
solute
• Plants commonly use the gradient of hydrogen
ions generated by proton pumps to drive active
transport of nutrients into the cell
38. 3. Which of the following amino acids would most
likely be present in the outer side (facing the lipid
tails) of a transmembrane domain of an integral
membrane protein?
a. a charged amino acid like lysine
b. a polar amino acid like serine
c. a special amino acid like glycine or
proline
d. a hydrophobic amino acid like valine
e. any of the above, with no preference
39. 3. Which of the following amino acids would most
likely be present in the outer side of a
transmembrane domain of an integral membrane
protein?
a. a charged amino acid like lysine
b. a polar amino acid like serine
c. a special amino acid like glycine or
proline
d. a hydrophobic amino acid like valine
e. any of the above, with no preference
40. 4. Assume that each of the following items experiences a
similar magnitude of energy difference driving their diffusion
across a pure lipid bilayer. If ranked in order from fastest to
slowest, which of the following items would likely be second in
terms of how much of it crosses the bilayer in a given time?
a. molecular oxygen
b. sucrose
c. insulin
d. glucose
e. water
41. 4. Assume that each of the following items experiences a
similar magnitude of energy difference driving their diffusion
across a pure lipid bilayer. If ranked in order from fastest to
slowest, which of the following items would likely be second in
terms of how much of it crosses the bilayer in a given time?
a. molecular oxygen (first because a gas)
b. Sucrose (needs active transport)
c. Insulin (ligand for receptor signaling)
d. Glucose (needs active transport)
e. Water (second from channels & size)
42. 5. Consider various transport systems in a hypothetical cell
(see figure). Which one of these systems would both be a
passive system and not alter the membrane potential through
its operation?
43. 5. Consider various transport systems in a hypothetical cell
(see figure). Which one of these systems would both be a
passive system and not alter the membrane potential through
its operation?
A
B
C
D
E
44. Bulk Transport: Exocytosis
• In exocytosis, transport vesicles migrate to the
membrane, fuse with it, and release their contents
• Many secretory cells use exocytosis to export their
products
Bulk Transport: Endocytosis
• In endocytosis, the cell takes in macromolecules by
forming vesicles from the plasma membrane
• Endocytosis is a reversal of exocytosis, involving
different proteins
• Small molecules and water enter or leave the cell through the
lipid bilayer or by transport proteins
• Large molecules, such as polysaccharides and proteins, cross
the membrane via vesicles (bulk transport)
46. LE 7-20c
Receptor
RECEPTOR-MEDIATED ENDOCYTOSIS
Ligand
Coated
pit
Coated
vesicle
Coat protein
Coat
protein
Plasma
membrane
0.25 µm
A coated pit
and a coated
vesicle formed
during
receptor-
mediated
endocytosis
(TEMs).
•Three types of endocytosis:
–Phagocytosis (“cellular
eating”): Cell engulfs
particle in a vacuole
–Pinocytosis (“cellular
drinking”): Cell creates
vesicle around fluid
–Receptor-mediated
endocytosis: Binding of
ligands to receptors
triggers vesicle formation
Editor's Notes
Figure 7.2 Phospholipid bilayer (cross section)
Figure 7.3 Updated model of an animal cell’s plasma membrane (cutaway view)
Figure 7.6 The structure of a transmembrane protein
Figure 7.7 Some functions of membrane proteins
Answer: C
Figure 7.10 The diffusion of solutes across a synthetic membrane
Figure 7.11 Osmosis
Figure 7.12 The water balance of living cells
Answer: C
Answer: C
Figure 7.14 Two types of transport proteins that carry out facilitated diffusion
Figure 7.15 The sodium-potassium pump: a specific case of active transport
Figure 7.16 Review: passive and active transport
Figure 7.18 Cotransport: active transport driven by a concentration gradient
Answer: D
Transmembrane domains primarily consist of helices of hydrophobic amino acids.
Answer: D
Transmembrane domains primarily consist of helices of hydrophobic amino acids.