BackAnatomy & Physiology: Cell Structure and Membrane Transport
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Terms in this set (20)
The three basic parts are: plasma membrane (flexible outer boundary), cytoplasm (intracellular fluid with organelles), and nucleus (DNA-containing control center).
The plasma membrane is a bilayer of phospholipids with embedded proteins, cholesterol, and surface sugars forming the glycocalyx, allowing dynamic movement and specialized functions.
Phospholipids have polar hydrophilic phosphate heads facing water and nonpolar hydrophobic fatty acid tails facing inward, forming a bilayer that acts as a selective barrier.
Integral proteins span the membrane and function as transporters, enzymes, or receptors. Peripheral proteins attach loosely and act as enzymes, motor proteins, or in cell-to-cell connections.
Functions include: transport, receptors for signal transduction, enzymatic activity, cell-cell recognition, cell-to-cell joining, and attachment to cytoskeleton and extracellular matrix.
The glycocalyx is a carbohydrate-rich coating on the cell surface made of glycoproteins and glycolipids, serving as biological markers for cell recognition and immune system identification.
Tight junctions form impermeable seals; desmosomes are anchoring junctions that prevent tearing; gap junctions allow communication via tunnels for small molecules and ions.
Passive transport requires no energy and moves substances down their concentration gradient. Active transport requires ATP to move substances against their gradient.
Simple diffusion, facilitated diffusion, and osmosis—all involve movement from high to low concentration without energy input.
Facilitated diffusion requires carrier or channel proteins to transport hydrophilic or large molecules down their concentration gradient, unlike simple diffusion which occurs directly through the lipid bilayer.
Osmosis is the diffusion of water across a selectively permeable membrane, occurring through the lipid bilayer or specialized water channels called aquaporins.
Osmolarity is the total solute concentration in a solution; water moves by osmosis from areas of low solute (high water) concentration to high solute (low water) concentration.
Tonicity describes a solution's effect on cell volume: isotonic causes no change, hypertonic causes cell shrinkage, and hypotonic causes cell swelling and possible lysis.
The Na+-K+ pump uses ATP to pump 3 Na+ out and 2 K+ into the cell, maintaining electrochemical gradients essential for nerve and muscle function.
Secondary active transport uses energy stored in ion gradients created by primary active transport to move other substances via cotransport proteins, either symporters or antiporters.
Phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis (selective uptake via receptors).
Exocytosis ejects materials enclosed in secretory vesicles by fusion with the plasma membrane, releasing substances like hormones and neurotransmitters outside the cell.
RMP is the voltage across the plasma membrane at rest, typically between -50 to -90 mV, with the inside of the cell more negative than outside.
K+ diffuses out through leakage channels down its concentration gradient, creating a negative charge inside the cell balanced by electrical attraction, making K+ the primary determinant of RMP.
CAMs anchor cells to each other and the extracellular matrix, assist in cell movement, and signal intracellular changes. Membrane receptors bind ligands to trigger cellular responses like signal transduction.