Please enable JavaScript.
Coggle requires JavaScript to display documents.
Membrane Structure And Function - Coggle Diagram
Membrane Structure And Function
Fluid mosaic model: is the cell membrane described as a fluid mosaic where phospholipids and unanchored proteins can move laterally and its composed of various components.
Amphipathic nature: phospholipids and integral membrane proteins are amphipathic, possessing both hydrophilic and hydrophobic regions.
Membrane fluidity regulation: cholesterol plays a crucial role in buffering membrane fluidity in animal cells, preventing it from becoming too rigid at low temperature or too fluid at high temperatures, plants use different steroid lipids for this purpose.
Selective permeability: the plasma membrane controls the passage of substances, allowing small non polar molecules to pass freely, while polar molecules and ions require transport proteins.
membrane transport
selective permeability: the membranes ability to control what enters and exist the cell
easily permeable: small, non-polar/hydrophobic molecules (O2, CO2, hydrocarbons)
impermeable (without assistance): polar molecules (water, glucose) ions (charged)
passive transport (no ATP required)
diffusion: movement of substances from high to low concentration
simple diffusion: direct passage through the lipid bilayer (for small, non-polar molecules)
facilitated diffusion: movement helped by transport proteins (channels or carriers) for polar molecules and ions
channel proteins: form hydrophilic pores
carrier proteins: blind to solutes and change shape
Osmosis: diffusion of water across a selectively preamble membrane.
Tonicity: effect of external solution on cell volume
Isotonic solution: solute concentration equal inside and outside, nonet water movement
animal cells: normal
plant cells: flaccid ( not ideal)
-hypotonic solution: lower solute concentration outside, water enters the cell
animals: lyse (burst)
plant cells: turgid (ideal, due to cell wall)
Osmoregulation: control o water balance in organisms without cell walla( paramecium with contractile vacuole)
active transport (energy required)
moves substances against their concentration gradient (low to high)
requires ATP
performed by carrier proteins
sodium potassium pump: pumps 3 Na+ out and K+ in, against gradients, using ATP
proton pump: actively transport protons (H+) out of cell, creating an electrochemical gradient
-membrane potential: voltage differences across the membrane due to unequal distribution of ions
co-transport: active transport of one solute indirectly drives the transport of another solute (proton-sucrose co-transporter
bulk transport ( large molecules/particles)
involves vesicles and requires energy
excoyttosis: export of substances from the cell. vesicles fuse with the plasma membrane to release contents
endocytosis: import of substances into the cell. plasma membrane forms a pocket that pinches off to form a vesicles
phagocytosis: cellular eating- engulfment of solid particles
pinocytosis: cellular drinking- uptake of extracecullar fluid and dissolved
receptor-mediated endocytosis: specific uptake triggered by ligand binding to surface receptors
Passive vs. active transport: the passive transport (diffusion, facilitated diffusion, osmosis) does not require energy, moving substances down the concentration gradient. Active transport requires energy (ATP) to move substances against their concentration gradient.
Bulk transport: large molecules and particles are transported via vesicles through exocytosis (export) and endocytosis (import) , which include phagocytosis ( cellular eating), pinocytosis (cellular drinking), and receptor mediated endocytosis.
Tonicity and osmosis: explains how water moves across semipermeable membranes in response to solute concentration differences, leading to isotonic, hypotonic, and hypertonic environments, and their effects on animals/plant cells
membrane structure
Phospholipid bilayer: composed of phospholipids with hydrophilic heads and hydrophobic tails
amphipathic molecules
forms bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward
fluidity: phospholipids are not covalently linked and can move laterally, making the membrane fluid.
membrane proteins
integral proteins, embedded within the hydrophobic core, often spanning the whole membrane( transmembrane proteins) amphipathic.
peripheral proteins: associated with the membrane surface
functions" transport, enzymatic activity, signal transduction, cell to cell recognition, intercellular joining, attachment to cytoskeleton and ECM
cholesterol
steroid fluid found in animal cell membranes
acts as a "fluidity buffer" regulating membrane fluidity across temperature changes
absent in plant cell membranes
glycolipids & glycoproteins:
sugars attached to lipids or proteins, involved in cell-cell recognition
membrane sidedness: membranes have distinct inner and outer faces, established during synthesis in the ER and Golgi apparatus
temperature regulation
warm temp: restrains phospholipids movement, keeping the membrane more solid
cold temp: increases flexibility, preventing the membrane form freezing
buffer analogy: compares cholesterol function to that of a pH buffer, maintaining membrane stability
Importance of homeostasis
to little cholesterol: increases cell membrane susceptibility to temperature changes, risking cell damage or loss
too much cholesterol: associated with cardiovascular disease
cholesterol regulates phospholipids movement in cell membranes
it prevents membrane from freezing at cold temp and becoming too liquid at warm temps
cholestrol acts as a "buffer" for cell membrane fluidity, similar to how chemcial buffers maintain pH
a healthy range of cholesterol is essential for cellular function and overall health
the composition of cell membrane, (saturated vs. unsaturated fatty acids, cholesterol content) varies by cell type, location, and function.
proteins are key components of cell membranes, categorized by their location (peripheral proteins)
cell-specific needs: composition depends on the cells location and job
ex: skin cells need more resistance to temp changes, while gastrointestinal tract cells need more resistance to acid
cells with more saturated fatty acids may sometimes have more cholesterol