The plasma membrane separates the cell from its surroundings and is composed predominantly of phospholipids arranged in a bilayer. Cholesterol is also present in the membrane and helps maintain fluidity. Integral and peripheral proteins are embedded in the membrane. The fluid mosaic model describes the membrane as a fluid bilayer with embedded proteins that can diffuse laterally. The membrane regulates transport into and out of the cell and has various functions including acting as a selective barrier and providing anchoring sites.
Polysaccharide introduction, example, structure, starch, cellulose, chitin those structure and important functions and their presence in plants and animals, polysaccharide types based on functions and their composition , functions of polysaccharides , important images for relevant polysaccharides types, polysaccharide role in plants and animal cells. Starch - structure and functions, cellulose structure and functions, chitin - structure and functions
Polysaccharide introduction, example, structure, starch, cellulose, chitin those structure and important functions and their presence in plants and animals, polysaccharide types based on functions and their composition , functions of polysaccharides , important images for relevant polysaccharides types, polysaccharide role in plants and animal cells. Starch - structure and functions, cellulose structure and functions, chitin - structure and functions
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
SDS-Polyacrylamide Gel Electrophoresis
What is SDS?
Preparation of Gel
Process of SDS-PAGE
Visualization of protein bands
SDS-PAGE is differentiated into two systems.
*continuous sds-page
*discontinuous sds-page.
Polyacrylamide is used to form a gel, a matrix of a pores which allow the molecules migrate at different rates.
Negatively charged detergent sodium dodecyl sulfate.
Used to denature and linearize the proteins
Coated the proteins with negatively charged.
SDS-page is a technique that used to separate proteins according to their molecular size through the gel.
Proteins are unfolded and migrate from cathode to anode terminal at different rates.
Molecular weight is determined by compare the result with a standard curve of relative motility of standard proteins.
Visualizes the band under UV light.
Types of stains;
Coomassie Blue;
* Coomassie Brilliant Blue staining The Coomassie dyes R-250 and G-250 bind to proteins stoichiometrically through their sulfonic acid groups.
* . The interactions between dye and protein are Van der Waals and ionic. The sulfonic acid groups interact with positive amine groups. Therefore coomassie dye binds to wide range of proteins.
* Limited to ~100ng of protein.
Silver stain;
*most sensitive test
*detection limit 0.1-1.0ng of protein
The size of pores is determined by the concentration of acrylamide.
The higher the concentration, the smaller the size of pores.
Discontinuos sds-page consist of two different gels.
*stacking gel -4%of acrylamide
*separating gel-range from 5-15% of acrylamide.
Sugar derivatives and reactions of monosaccharidesNamrata Chhabra
Reactions of monosaccharides, osazone formation, reduction, oxidation, reaction with acids and alkalies, ester formation and formation of amino sugars, amino sugar acids and deoxy sugars.
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
SDS-Polyacrylamide Gel Electrophoresis
What is SDS?
Preparation of Gel
Process of SDS-PAGE
Visualization of protein bands
SDS-PAGE is differentiated into two systems.
*continuous sds-page
*discontinuous sds-page.
Polyacrylamide is used to form a gel, a matrix of a pores which allow the molecules migrate at different rates.
Negatively charged detergent sodium dodecyl sulfate.
Used to denature and linearize the proteins
Coated the proteins with negatively charged.
SDS-page is a technique that used to separate proteins according to their molecular size through the gel.
Proteins are unfolded and migrate from cathode to anode terminal at different rates.
Molecular weight is determined by compare the result with a standard curve of relative motility of standard proteins.
Visualizes the band under UV light.
Types of stains;
Coomassie Blue;
* Coomassie Brilliant Blue staining The Coomassie dyes R-250 and G-250 bind to proteins stoichiometrically through their sulfonic acid groups.
* . The interactions between dye and protein are Van der Waals and ionic. The sulfonic acid groups interact with positive amine groups. Therefore coomassie dye binds to wide range of proteins.
* Limited to ~100ng of protein.
Silver stain;
*most sensitive test
*detection limit 0.1-1.0ng of protein
The size of pores is determined by the concentration of acrylamide.
The higher the concentration, the smaller the size of pores.
Discontinuos sds-page consist of two different gels.
*stacking gel -4%of acrylamide
*separating gel-range from 5-15% of acrylamide.
Sugar derivatives and reactions of monosaccharidesNamrata Chhabra
Reactions of monosaccharides, osazone formation, reduction, oxidation, reaction with acids and alkalies, ester formation and formation of amino sugars, amino sugar acids and deoxy sugars.
Structure and functions of cell, transport across cell membrane, cell
division, cell junctions. General principles of cell communication,
the smallest unit that can live on its own and that makes up all living organisms and the tissues of the body
The basic tenets of the cell theory are as follows:
All living things are made up of one or more cells.
The cell is the structural and functional unit of all living things.
Cells come from pre-existing cells through the process of division.
All cells are the same in regard to chemical composition.
Cells also communicate with each other. Whether in plants, humans, or animals, they connect to create a solid, well formed organism. In humans, cells build tissues, tissues form organs, and organs work together to keep the body alive.
Experts estimate that there are around 200Trusted Source cell types in the human body.
KEY CONCEPTS
7.1 Cellular membranes are fluid mosaics of lipids and proteins
7.2 Membrane structure results in selective permeability
7.3 Passive transport is diffusion of a substance across a
membrane with no energy investment
7.4 Active transport uses energy to move solutes against their gradients
7.5 Bulk transport across the plasma membrane occurs by exocytosis and endocytosis
Transcriptomics is the study of RNA, single-stranded nucleic acid, which was not separated from the DNA world until the central dogma was formulated by Francis Crick in 1958, i.e., the idea that genetic information is transcribed from DNA to RNA and then translated from RNA into protein.
Immunoglobulins are glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies. The immunoglobulins derive their name from the finding that they migrate with globular proteins when antibody-containing serum is placed in an electrical field.
A biosensor is a compact analytical device incorporating a biological or biologically derived sensing element either associated or integrated within a physicochemical transducer
Here are some slides to discuss about biosensors and their application which we prepared in graduation.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
5. Hydrocarbon ring structure of cholesterol plays a distinct
role in determining membrane fluidity
Membrane sterols
Sterols=Steroid ring + Alcohol group
6. Cholesterol molecules insert into
the bilayer with their polar hydroxyl
groups close to the hydrophilic head
groups of the phospholipids.
The rigid hydrocarbon rings of
cholesterol therefore interact with the
regions of the fatty acid chains that
are adjacent to the phospholipid
head groups.
This interaction decreases the
mobility of the outer portions of the
fatty acid chains, making this part of
the membrane more rigid.
Insertion of cholesterol interferes with interactions between
fatty acid chains, thereby maintaining membrane fluidity at
lower temperatures.
7. • The hydrophobic regions of an integral protein consist of
one or more stretches of nonpolar amino acids, often coiled
into alpha helices
• Peripheral proteins
are bound to the
surface of the
membrane
• Integral proteins
penetrate the
hydrophobic core
• Integral proteins that
span the membrane
are called
transmembrane
proteins
8. Membrane organization and properties described by:
Sandwitch model proposed by Danielli‐Davson
Unit membranes model of Robertson
Fluid Mosaic Model by Singer and Nicolson 1972
9. *
● FLUID- because individual phospholipids and
proteins can move side-to-side within the
layer, like it’s a liquid.
● MOSAIC- because of the pattern produced by
the scattered protein molecules when the
membrane is viewed from above
FLUID MOSAIC MODEL
10. *
Functions of Plasma
Membrane
● Protective barrier
● Regulate transport in & out of cell
( a selective barrier to the passage of molecules
selectively permeable)
● Allow cell recognition
● Provide anchoring sites for filaments
of cytoskeleton
11. *
Functions of Plasma
Membrane
● Provide a binding site for enzymes
● Interlocking surfaces bind cells
together (junctions)
●Contains the cytoplasm (fluid in cell)
12. Properties of the plasma
membrane
1.Dynamic
2.Fluid
3.Asymmetric
4.Semipermeable
13. 1. Dynamic
Lateral movement occurs
107 times per second.
Flip-flopping across the membrane
is rare ( once per month).
These studies have also shown that individual lipid molecules
rotate very rapidly about their long axis and that their
hydrocarbon chains are flexible.
14. The fluidity of a lipid bilayer depends on -composition and
temperature.
A synthetic bilayer made from a single type of phospholipid
changes from a liquid state to a two-dimensional rigid
crystalline (or gel) state at a characteristic freezing point. This
change of state is called a phase transition.
2. Fluid
Membranes must be fluid to work properly;
they are usually about as fluid as salad oil
15. The temperature at which it occurs is lower (that is, the membrane
becomes more difficult to freeze) if the hydrocarbon chains are short or
have double bonds.
A shorter chain length reduces the tendency of the hydrocarbon tails to
interact with one another, and cis-double bonds produce kinks in the
hydrocarbon chains that make them more difficult to pack together, so that
the membrane remains fluid at lower temperatures.
Bacteria, yeasts, and other organisms whose temperature fluctuates with
that of their environment adjust the fatty acid composition of their
membrane lipids to maintain a relatively constant fluidity. As the
temperature falls, for instance, fatty acids with more cis-double bonds are
synthesized, so the decrease in bilayer fluidity that would otherwise result
from the drop in temperature is avoided.
2. Fluid
Role of phospholipids
16. Cholesterol tends to make lipid bilayers less fluid, at
the high concentrations found in most eucaryotic
plasma membranes
It also prevents the hydrocarbon chains from coming
together and crystallizing.
In this way, it inhibits possible phase transitions
2. Fluid
Role of Cholesterol
17. 3. Asymmetry
The Plasma Membrane Contains Lipid Rafts That Are
Enriched in Sphingolipids, Cholesterol, and Some
Membrane Proteins
For some lipid molecules, such as the sphingolipids which tend to
have long and saturated fatty hydrocarbon chains, the attractive
forces can be just strong enough to hold the adjacent molecules
together transiently in small microdomains. Such microdomains,
or lipid rafts, can be thought of as transient phase separations in
the fluid lipid bilayer where sphingolipids become concentrated.
18. 3. Asymmetry
Lipid asymmetry is functionally important. Many cytosolic
proteins bind to specific lipid head groups found in the cytosolic
monolayer of the lipid bilayer.
The enzyme protein kinase C (PKC), for example, is activated in
response to various extracellular signals.
It binds to the cytosolic face of the plasma membrane, where
phosphatidylserine is concentrated, and requires this negatively
charged phospholipid for its activity.
20. Small molecules and larger hydrophobic
molecules move through easily.
e.g. O2, CO2, H2O
4.Semipermeable Membrane
21. Synthesis and 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
22. New phospholipid molecules are synthesized in the ER by membrane-bound enzymes which use
substrates (fatty acids) available only on one side of the bilayer.
Flipases transfer specific phospholipid molecules selectively so that different types become
concentrated in the two halves. One sided insertion and selective flippases create an
asymmetrical membrane
Plasma Membrane Biosynthesis
23. The Permeability of the Lipid Bilayer
-Transport across membrane
• 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
24. 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
25. • 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
• Some diseases are caused by malfunctions in specific
transport systems, for example the kidney disease
cystinuria
26. Transport
Can be active (energy
requiring) or passive
Three general
classes of
transport
systems.
Transporters
differ in the
number of
solutes
(substrates)
transported and
the direction in
which each
solute moves.
27. 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 be directional
• At dynamic equilibrium, as many molecules cross the
membrane in one direction as in the other
29. • Substances diffuse down their concentration
gradient, the region along which the density of a
chemical substance increases or decreases
• No work must be done to move substances down
the concentration gradient
• The diffusion of a substance across a biological
membrane is passive transport because no energy is
expended by the cell to make it happen
30. Effects of Osmosis on Water Balance
• Osmosis is the diffusion of water across a selectively
permeable membrane
• Water diffuses across a membrane from the region
of lower solute concentration to the region of higher
solute concentration until the solute concentration
is equal on both sides
31. Figure 7.14
Lower
concentration
of solute (sugar)
Higher
concentration
of solute
Sugar
molecule
H2O
Same concentration
of solute
Selectively
permeable
membrane
Osmosis
32. Water Balance of Cells Without Walls
• Tonicity is the ability of a surrounding 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
34. • Hypertonic or hypotonic environments create osmotic
problems for organisms
• Osmoregulation, the control of solute concentrations
and water balance, is a necessary adaptation for life in
such environments
• The protist Paramecium, which is hypertonic to its
pond water environment, has a contractile vacuole
that acts as a pump
36. 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
37. • In a hypertonic environment, plant cells lose water;
eventually, the membrane pulls away from the wall, a
usually lethal effect called plasmolysis
38. Facilitated Diffusion: Passive Transport
Aided by Proteins
• In facilitated diffusion, transport proteins speed the
passive movement of molecules across the plasma
membrane
• Channel proteins provide corridors that allow a
specific molecule or ion to cross the membrane
• Channel proteins include
– Aquaporins, for facilitated diffusion of water
– Ion channels that open or close in response to a
stimulus (gated channels)
39. Active transport uses energy to move
solutes against their gradients
• Facilitated diffusion is still passive because the solute
moves down its concentration gradient, and the
transport requires no energy
• Some transport proteins, however, can move solutes
against their concentration gradients
40. The Need for Energy in Active
Transport
• Active transport moves substances against their
concentration gradients
• Active transport requires energy, usually in the form
of ATP
• Active transport is performed by specific proteins
embedded in the membranes
41. • Active transport allows cells to maintain concentration
gradients that differ from their surroundings
• The sodium-potassium pump is one type of active
transport system
49. Cotransport: Coupled Transport by a
Membrane Protein
• Cotransport occurs when active transport of a
solute indirectly drives transport of other solutes
• Plants commonly use the gradient of hydrogen
ions generated by proton pumps to drive active
transport of nutrients into the cell