Cellular Processes BIOSCI 107

The University of Auckland BIOSCI 107 flashcards relating to cellular processes topic.

Cell membrane

A biological membrane that separates and protects the interior of a cell from the external environment; it regulates the movement of substances in and out of the cell. Primary is composed of a phospholipids bilayer embedded with proteins.

Membrane structure

Thin 8nm, flexible and sturdy barrier that surrounds cytoplasm of the cell.

Lipid Bilayer

Selectively permeable that acts barrier to entry or exit of polar substances, contains embedded proteins that regulate traffic.

Fluid mosaic model

“Sea of lipids in which proteins float like icebergs.” The membrane is 50% lipid and 50% proteins.

Amphipathic

Molecules that have both polar and nonpolar parts

Hydrophilic

“Water loving” molecules or parts of molecules that are attracted to water and can interact with it, often through hydrogen bonding.

Hydrophobic

“Water fearing” molecules or parts of molecules that repel water and do not easily mix with it, often due to it being nonpolar.

Polar

Refers to a molecule or part of a molecule that has an uneven distribution of electrical charge, creating partial positive and negative regions.

Non Polar

Refers to molecules or parts of molecules that have an even distribution of electrical charge, with no distinct positive or negative regions. These molecules are typically hydrophobic and don't mix well with water (e.g. oils).

Hypertonic

A solution that has a higher concentration of solutes compared to another solution (like inside the cell). Water moves out of the cell into a hypertonic solution, causes the cell to shrink.

Hypotonic

Solution has a lower concentration of solutes compared to another solution (like inside the cell). Water moves into the cell causing it to swell or even burst.

Isotonic

Two solutions have the same concentration of solutes. In an isotonic environment, water moves in and out of the cell at equal rates, so the cell maintains its normal shape and volume.

Phospolipids

Type of lipid with a hydrophilic "head" and two hydrophobic "tails.” Are amphipathic.

Membrane fluidity

How freely the lipids and proteins in the cell membrane move within the bilayer. Is determined by lipid tail length (longer tail, less fluid the membrane), number of double bond (more double bonds increase fluidity), and amount of cholesterol (more decreases fluidity).

Integral protein

Extend into or completely across the cell membrane (transmembrane protein). Are amphipathic and have hydrophobic regions that span the hydrophobic core of the lipid bilayer.

Peripheral protein

Attached to either the inner or outer surface of cell membrane and are easily removed from it.

Selective permeability

Cell membrane allows some substances to pass through while blocking others.

Diffusion

Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration, until equilibrium is reached.

Concentration gradient

Non charged molecules will diffuse down their concentration gradients. Occurs when solutes are concentrated on one side.

Electrochemical gradient

Ions will be influenced by membrane potential in addition to their concentration gradient. Combines concentration and charge differences.

Osmosis

Net diffusion of water across a semi permeable membrane from an area of lower solute concentration to an area of higher solute concentration, aiming to balance solute concentrations.

Tonicity

Measure of a solution's ability to change the volume of cells by altering their water content.

Osmolarity

Osmolarity is the total concentration of solute particles in a solution, expressed as osmoles per liter (Osm/L).

Transmembrane transport

Refers to the movement of molecules or ions across a cell membrane.

Non mediated transport

Does not directly use a transport protein.

Mediated transport

Moves materials with the help of a transport protein.

Channels (transport protein)

Ion channels are water filled pores that span the hydrophobic core of the lipid bilayer and allow passage of ions across cell membrane. Do not bind to solute, can be rapid, exhibit ion selectivity, and can also be gated.

Carriers (transport protein)

Bind to specific solute and undergo a confirmation change in order to transfer the solute across membrane. Is slower than channels, can be passive or active transport.

Facilitated Diffusion

Type of passive transport where molecules move down their concentration gradient across a membrane, but with the help of transport proteins, like channels or carriers. It doesn’t require energy.

Active transport

Movement of molecules or ions against their concentration gradient, requiring energy, typically in the form of ATP. This process uses carrier proteins like pumps (e.g., the Na⁺/K⁺ pump).

Sodium-Potassium Pump (Na/K ATPase)

Type of primary active transport protein that moves 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell, against their concentration gradients, using ATP.

Passive transport

Passive transport is the movement of molecules across a membrane down their concentration gradient, without requiring energy.

Secondary Active transport

Uses the energy stored in an ion gradient (created by primary active transport) to move another molecule against its concentration gradient.