Chapter 5 Membrane Transport & Cell Signaling

Selective permeability

A property of cell membrane: substances are filtered and let through via proteins spanned throughout the membrane

amphipathic

Pertains to a molecule containing both hydrophilic polar (water-soluble) and hydrophobic nonpolar (not water-soluble) portions in its structure

fluid mosaic model

A model conceived by S.J. Singer and Garth Nicolson in 1972 to describe the structural features of biological membranes

integral proteins

A protein molecule or protein assembly permanently attached in biological membrane

peripheral proteins

Membrane proteins that are bound to the surface of the membrane and not integrated into the hydrophobic region

glycoproteins

Proteins that have sugars in them (?)

glycolipids

Lipids that have carbohydrates attached to it; found in the fluid mosaic model.

transport proteins

A type of protein located in the membrane and specifically allow some particles to get through.

aquaporins

integral membrane proteins from a larger family of major intrinsic proteins (MIP) that form pores in the membrane of biological cells

diffusion

The passive movement of molecules or particles along a concentration gradient, or from regions of higher to regions of lower concentration

concentration gradient

a gradual change in the concentration of solutes in a solution as a function of distance through a solution

passive transport

The movement of a chemical substance across the cell membrane without using any energy; diffusion

tonicity

The ability of a surrounding solution to cause a cell to gain or lose water.

isotonic

A solution having the same osmotic pressure as some other solution, especially one in a cell or a body fluid.

hypertonic

A solution having a higer osmotic pressure than a particular fluid, (hyper means "more").

hypotonic

A solution having a lower osmotic pressure than a particular fluid (hypo means "lower").

osmoregulation,

the process which cells and single celluar organisms use to maintain fluid and control their water balance with the enviornment

turgid

The state when a cell is very firm because the cell wall is experiencing a back pressure to stop further water taking

flaccid

The state when a cell is very flat because it is surrounded by an isotonic environment and therefore can not take water in

plasmolysis

When plants are surrouned by isotonic environment, their cells shivels with its plasma membrane pulled away from the wall

facilitated diffusion

mechanism in which a transport protein speeds up the diffusion in accordance to the concentration gradient

ion channels

channel proteins that transport ion

gated channels

ion channels that open or close in response to a stimulus (ref.42. ion-gated ion channel)

active transport

The transportation of molecules following or against the concentration gradient, requires energy.

membrane potential

Range of voltage in and around membrane

electrochemical gradient

The interaction of chemical force(ion concentration) and electrical force(membrane potential) with cell membrane.

electrogenic pump

a transport protein that generates voltage across a membrane

proton pump

a protein embedded in a biological membrane that moves protons (H+) across the membrane, creating a proton gradient. These pumps are crucial for various cellular processes, including energy production, pH regulation, and nutrient transport.

cotransport

the mechanism in which a ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes.

exocytosis

The process of transport vesicles migrate to and fuse with membrane, then releasing their contents

endocytosis

The intake of molecules by forming new vesicles from the plasma membrane

phagocytosis

cellular "eating"

pinocytosis

cellular "drinking"

local regulators

messenger molecules secreted by signaling cell

hormones

The chemical signal the endocrine system send to the rest of body; could be steroids or proteins. | discovered by Earl W. Sutherland who later suggested the 3 processes of signaling

reception

receptor triggers changes when signal molecule ( ligand) binds to it

transduction

step of series of steps that converts the signal to a form that can bring about a cellular response

signal transduction pathway

a sequence of changes in a series of molecules during transduction

response

any cellular activities

ligand

a signal molecule that specifically binds to another molecule

G protein-couples receptor (GPCR)

receptors that work with help of G proteins which bind to energy-rich molecules GTP

ligand-gated ion channel

a membrane receptor that acts as a gate, allowing ions to pass through when a specific molecule (ligand) binds to it and causes a conformational change. This change opens the channel, enabling ions to flow across the cell membrane