Transmembrane Transport PDF

Pumping 3 Na⁺ out and 2 K⁺ in (both against the gradiant) Allows Essential molecules like...

Pumping 3 Na⁺ out and 2 K⁺ in (both against the gradiant) Allows Essential molecules like nutrients can enter the cell for every ATP hydrolyzed ** It is Semi-permeable (selectively allows certain **Na⁺-K⁺ Pump** Plasma Membrane molecules to pass through while keeping others Keeps intermediate metabolites inside the cell Maintains membrane potential, regulates cell volume (high out)** Na⁺ concentration outside the cell and high K⁺ inside) Excretes waste products for cell health Maintains low intracellular Ca²⁺ concentration **Calcium Pump** **Primary Active Transport**: Regulates acidity in stomach cells and follows the concentration gradient, meaning molecules move **Proton Pump** from areas of high concentration to low concentration organelles like lysosomes Largest family of ATP hydrolysis-coupled Small or hydrophobic molecules move through transporters Simple Diffusion the lipid bilayer without assistance (O₂, CO₂, **Passive Transport (movement without energy steroids) input)** Import nutrients (amino acids, peptides) Importers & Exporters: Larger or charged molecules use transport proteins Facilitated Diffusion Export toxins, drugs, antibiotics (channels or carriers) (glucose, amino acids) **ABC Transporters** (ATP-binding cassette) Active Transport - Key Concepts Overexpressed in tumor cells Osmosis The movement of water through the membrane Example: **MDR transporter** (multidrug Types of Transport resistance) This process requires energy (usually ATP) to move Pumps drugs out → **Drug resistance** molecules against their concentration gradient Example: **CFTR** (Cystic Fibrosis Na⁺-K⁺ pump Transmembrane Conductance Regulator) **Active Transport** **Primary Active Transport**: Direct use of **Symporters**: Molecules move in same direction Calcium pump energy (ATP) (eg; Na⁺/glucose co-transporters in the intestines) But then Na+ accumulates in the cell and their is no more to realise secondary transport. We then need atp to pump na+ out of the cell. SO the movement of one solute drives the movement of another. There are two types: **Coupled Transport (Secondary Active Transport)**: Transmembrane Types: Proton pump undirectly secondary transport use ATP **Antiporters**: Molecules move in opposite directions (e.g., Na⁺/Ca²⁺ exchanger in cardiac Transport of Small **Secondary Active Transport** (Coupled Transport) (Uses the energy from the movement Symporters (Na⁺/glucose co-transporter) cells) Molecules and Ions of one molecule down its gradient to move another molecule up its gradient) Antiporters (Na⁺/Ca²⁺ exchanger, Na⁺/H⁺ exchanger) Hydrophobic molecules pass easily This selectivity is achieved through narrow pores Smaller molecules diffuse faster **Simple Diffusion**(O₂, CO₂, steroids) that act as size filters, and by interactions between the ion and specific components of the The larger the gradient, the faster the diffusion channel, such as carbonyl oxygens Ion channels and carrier proteins **They are Selective**:based on size and charge **Na⁺ channels**: More selective for Na⁺ over K⁺ Passive Transport - Key Concepts Example: **GLUT-1** glucose transporter **K⁺ channels**: More selective for K⁺ over Na⁺ Allow specific ions to pass rapidly through the Ion Channels Open in response to changes in membrane Voltage-gated membrane potential **Facilitated Diffusion** Voltage-gated, ligand-gated, mechanosensitive Channels: Eg: the acetylcholine receptor at neuromuscular **Types of ion channels**: Ligand-gated Open when a specific molecule (ligand) binds junction with na+ **Na⁺ and K⁺ channels**: Ion selectivity Mechanosensitive Respond to mechanical forces (e.g., stretching) Bind to the molecule and undergo conformational changes Carriers to transport it across the membrane the movement of water across a membrane down its osmotic gradient Osmosis and Aquaporins **Osmosis**: Have narrow pores that allow water to pass in single file moves through specialized channels called aquaporins, which: Completely block ions