BIOCHEM_S1T4_MEMBRANES-STRUCTURE-AND-FUNCTIONS

1. Overall structures, 2. Rapid ion conduction, 3. Selectivity, 4. Gating properties.

An integral membrane protein composed of four identical subunits with two trans-membrane segments, creating an inverted 'V' structure.

They likely play a role in endocytosis (cellular uptake of various components).

Molecules that act as membrane shuttles for various ions, such as valinomycin for K+.

They prevent the diffusion of macromolecules between cells.

Fat maldigestion, infertility in males due to abnormal development of the vas deferens, and elevated levels of chloride in sweat (>60 mmol/L).

It pumps three Na+ out and two K+ into cells.

They have selective permeabilities, act as barriers, and facilitate exchanges with the extracellular environment through exocytosis and endocytosis.

They span as a bundle of α-helical transmembrane segments, are amphipathic and globular, and are asymmetrically distributed in the membrane bilayer.

They form water channels that facilitate the movement of water across certain membranes.

Simple diffusion and facilitated diffusion.

By maintaining an asymmetry of inside-outside voltage and using voltage-gated channels.

Fat maldigestion.

They contain gap junctions that allow adjacent cells to communicate by exchanging materials.

1/3, distributed between plasma and interstitial compartment.

Peripheral proteins do not interact directly with the hydrophobic cores of phospholipids and are bound to the hydrophilic regions of integral proteins and phospholipid head groups.

Approximately 30%.

The passive flow of a solute from a higher to a lower concentration due to random thermal movement.

An electrochemical disturbance propagates in a wave-like form, generating a nerve impulse.

They compartmentalize the body's internal water and regulate ionic compositions of fluids.

2/3.

Infertility due to abnormal development of the vas deferens.

Vesicles surrounded by a lipid bilayer with an aqueous interior, formed through mild sonication.

Micelles, where hydrophobic regions are shielded from water and hydrophilic polar groups are immersed in the aqueous environment.

It regulates intracellular concentrations of Na+ and K+, maintaining low Na+ and high K+ concentrations.

The passive transport of a solute from a higher to a lower concentration mediated by a specific protein transporter.

Phospholipids, glycosphingolipids, and cholesterol.

They provide electrical insulation and speed up the propagation of the nerve impulse.

Elevated levels of chloride in sweat (>60 mmol/L).

Bidirectional delivery system, brings nutrients, O2, ions, hormones, and removes waste products.

They allow for variation in lipid content, incorporation of purified membrane proteins, controlled environments, and entrapment of compounds like drugs and genes.

The hydrophobic effect, which describes the tendency of nonpolar molecules to self-associate in an aqueous environment.

It is crucial for maintaining a net negative electrical potential inside the cell.

Vectorial movement of a solute across a membrane against a concentration gradient, requiring energy.

It describes membranes as dynamic structures with lipid rafts, caveolae, and tight junctions.

Through the GLUT4 transporter, which is enhanced by insulin.

Na+, Ca2+, Cl−, K+, Mg2+, and phosphate.

A model proposed by Singer and Nicolson in 1972, describing membranes as having phospholipids that undergo rapid lateral diffusion and are influenced by lipid composition.

They readily diffuse through the hydrophobic regions of the membrane due to their small size and low interaction with solvents.

Thermal agitation of the molecule, concentration gradient, and solubility of the solute.

Lipids, proteins, and carbohydrate-containing molecules.

They allow the selective entry of various ions across the membrane.

It allows glucose to enter cells by binding with Na+, which moves down its electrochemical gradient.

Energy (usually from ATP hydrolysis), Ca2+, and cytoskeletal elements.

The temperature at which membrane structure transitions from an ordered to a disordered state.

They function as enzymes, pumps, transporters, channels, structural components, antigens, and receptors.

Concentration gradient, electrical potential, permeability coefficient, hydrostatic pressure gradient, and temperature.

Asymmetric with distinct inner and outer surfaces or leaflets.

It regulates intracellular concentrations of sodium and potassium, requiring energy for active transport.

The process by which cells take up large molecules.

Ingestion of large particles such as viruses, bacteria, or cellular debris, occurring in specialized cells like macrophages.

Cholesterol buffers membrane fluidity by increasing fluidity below Tm and limiting disorder above Tm.

It minimizes the hydrophilic character of peptide bonds, allowing them to be amphipathic and form integral parts of the membrane.

Phosphatidylcholine.

ATP hydrolysis.

Through endocytosis and exocytosis mechanisms.

They fuse with primary lysosomes to form secondary lysosomes for intracellular disposal.

A process of cellular uptake of fluid and its contents, also known as 'cell drinking'.

Specialized areas of the exoplasmic leaflet of the lipid bilayer enriched in cholesterol, sphingolipids, and certain proteins.

The movement of proteins within the membrane; many nonmobile proteins do not exhibit this due to being anchored to the cytoskeleton.

Cholesterol.

A phospholipid formed from sphingosine and a fatty acid, esterified to phosphorylcholine.

Proteins that form water channels in certain membranes.

Fluid-phase pinocytosis (nonselective) and absorptive pinocytosis (receptor-mediated).

Caveolae derive from lipid rafts and contain the protein caveolin-1, which may be involved in their formation.

They transfer certain phospholipids from the inner to the outer leaflet of the membrane.

In the cell membrane.

Sugar-containing lipids built on a ceramide backbone.

Cystic fibrosis.

Viruses like hepatitis, poliomyelitis, AIDS, and COVID-19 can enter cells via this mechanism.

Through transport from the ER in vesicles, direct contact between membranes, or via phospholipid exchange proteins.

Specific proteins involved in facilitated diffusion and active transport.

No, it is absent in plant cells.

The process of releasing macromolecules to the exterior of the cell.

Integral proteins interact extensively with phospholipids and require detergents for solubilization, while peripheral proteins do not.

A transport system that moves one type of molecule bidirectionally.

They contain both hydrophobic and hydrophilic regions.

They can remain as membrane proteins, become part of the extracellular matrix, or enter extracellular fluid to signal other cells.

The transfer of one solute depends on the simultaneous or sequential transfer of another solute.

They face the aqueous environment.

The process involved in generating second messenger signaling molecules like cyclic nucleotides and calcium.

Symport moves two solutes in the same direction, while antiport moves two molecules in opposite directions.

Saturated fatty acids form straight tails, while unsaturated fatty acids form kinked tails.

Structures that allow direct transfer of small molecules between neighboring cells, composed of connexins.

By facilitated diffusion or active transport.

They increase the number of kinks, making the membrane more fluid.

Lipid bilayer-enclosed structures that can include exosomes and microvesicles, delivering distinct 'payloads' to target cells.

The transmembrane gradient of the substrate.

They solubilize and purify membrane proteins.

A recessive genetic disorder caused by mutations in the CFTR gene, leading to chronic bacterial infections.

Energy, usually in the form of ATP, as it occurs against an electrical or chemical gradient.

The hydrophobic end binds to hydrophobic regions, displacing bound lipids.

They can lead to diseases by altering the function of receptors, transporters, ion channels, and enzymes.

They use the gradient of one substrate created by active transport to drive the movement of another substrate.

Micelles.

Facilitated diffusion can be saturated and involves specific transporters.

Transmembrane proteins that allow the selective entry of various ions.

Size, extent of hydration, and charge density of the ion.

Channels that open in response to a specific molecule binding to a receptor.

Changes in membrane potential.

Mechanical stimuli such as pressure and touch.