Biology 211: Biomolecules and Cellular Systems - Unit 1: Membranes

Flashcards covering key vocabulary terms related to cellular membranes, lipids, transport mechanisms, and related concepts from Biology 211 lecture notes.

Lipids

Water insoluble (hydrophobic) molecules composed mostly of carbon and hydrogen atoms (hydrocarbons).

Triglycerides

A type of biological lipid that serves as an energy storage molecule, composed of 3 fatty acid 'tails' bound to a glycerol 'anchor'.

Phospholipids

Amphipathic biological lipids composed of an organic molecule, a phosphate, glycerol, and 2 fatty acid 'tails', forming charged/polar heads and uncharged/non-polar tails.

Cholesterol

A type of biological lipid (sterol) that regulates membrane fluidity in animal cells by preventing excess viscosity and excess fluidity.

Fatty Acids

Hydrocarbons with a carboxyl group at one end, varying in the number of carbon atoms (chain length) and the presence of C=C double bonds.

Saturated Fatty Acids

Fatty acids that have no carbon-carbon double bonds (C=C bonds).

Unsaturated Fatty Acids

Fatty acids that have one or more carbon-carbon double bonds (C=C bonds).

Amphipathic

A molecule possessing both hydrophilic (water-soluble) and hydrophobic (water-insoluble) properties, such as a phospholipid.

Biological Membranes

Structures that compartmentalize the cell, act as selectively permeable barriers, and provide scaffolds for communication and chemical reactions.

Fluid Mosaic Model

A model describing membrane structure as a mosaic of lipids, proteins, and sugars arranged around and within a bilayer, where most phospholipids are free to move along the plane of the membrane.

Integral Proteins

Proteins that integrate themselves through the membrane in the fluid mosaic model.

Peripheral Proteins

Proteins located on the edge of the membrane, on either side of the bilayer, in the fluid mosaic model.

Membrane Fluidity

A property of the lipid bilayer that is increased by high temperature, unsaturated fatty acid tails, and short fatty acid tails, and regulated by sterols like cholesterol.

Membrane Permeability

The ability of solutes to pass across the membrane, affected by membrane fluidity (fluid membranes are 'leaky' and viscous membranes are better barriers).

Selective Permeability

A characteristic of lipid bilayers allowing some molecules (e.g., small hydrophobic, small polar like H2O slowly) to pass directly, while restricting others (e.g., large/charged molecules).

Aquaporins

Specific protein channels that allow water to cross membranes rapidly.

Diffusion

The tendency of dissolved molecules to evenly distribute themselves in a solution, moving from areas of high concentration to areas of low concentration until equilibrium is reached.

Osmosis

The diffusion of water across a lipid bilayer, occurring when the solute cannot cross the membrane, causing water to move to ensure equilibrium is reached.

Tonicity

The relative solute concentration difference across a lipid bilayer, affecting diffusion and osmosis across the membrane.

Isotonic Solution

A solution where there is no difference in solute concentration between the inside and outside of the cell.

Hypertonic Solution

A solution that has a higher solute concentration compared to another reference point (e.g., the cell).

Hypotonic Solution

A solution that has a lower solute concentration compared to another reference point (e.g., the cell).

Passive Transport

Movement of molecules across a membrane that does not require cellular energy, occurring down a concentration gradient.

Simple Diffusion

A type of passive transport where small hydrophobic and small polar solutes diffuse directly across phospholipid bilayers down their concentration gradient without cellular energy and is reversible.

Facilitated Diffusion

A type of passive transport where integral membrane proteins (channels or carriers) facilitate the diffusion of large, charged, or polar molecules down their concentration gradient, which is substrate-specific and reversible.

Channel Proteins

Integral membrane proteins that form hydrophilic channels in the membrane through which water and ions can move during facilitated diffusion.

Carrier Proteins

Integral membrane proteins that transport large solutes (not water or ions) by binding to them and changing conformation, facilitating their diffusion across the membrane.

Active Transport

Movement of solutes across a membrane against their concentration gradient, requiring input of cellular energy to maintain concentration gradients.

Primary Active Transport

Active transport carried out by substrate-specific protein 'pumps' that directly use ATP to power the transporter, moving solutes up or against the concentration gradient and generating electrochemical gradients.

Secondary Active Transport

Active transport driven by the energy released as a different solute moves down its concentration gradient, where substrate-specific protein pumps move a solute against its gradient indirectly.

Symporters

A type of secondary active transport pump where the transported solute moves in the same direction as the driving ion.

Antiporters

A type of secondary active transport pump where the transported solute moves in the direction opposite from the driving ion.