1.4 Membrane Transport

Membranes control the composition of cells by passive and active transport

The net movement of particles from an area of high to low concentration facilitated by kinetic energy of particles

The difference in concentration between two locations

• temperature (high = fast) • length of diffusion path (short = fast) • surface area (more = fast) • particle size (small = fast) • concentration gradient (bigger = fast)

Movement of substances across selectively permeable membrane that involves the use of energy (ATP)

The movement of particles through a semi-permeable membrane that does not require energy (e.g diffusion or facilitated diffusion)

The movement of water through a semi-permeable membrane from low solute concentration to high solute concentration

Water cannot diffuse through the cell membrane due to it’s size and the presence of the hydrophobic lipid center, instead water travels through the membrane via the integral protein channel aquaporin

A state of osmolarity wherein a cell is plasmalysed due to a high solute concentration and a low water concentration. When cells are hyper-tonic water flows into them

State of osmolarity wherein the concentration of a solute is lower inside the cell than outside the cell, leading the cell to become turgid

State of osmolarity wherein the cell is in equilibrium and its solute concentration is balanced in and out of the cell, in this state cells are flaccid

Referring to the concentration of a solution and the number of solute particles per liter of solvent

The movement of large or polar models that can’t pass through the cell membrane via protein channels. The direction of facilitated diffusion depends on the concentration gradient

The movement of large and polar molecules against a concentration gradient that requires the use of carrier proteins and energy

Transport of molecules using energy derived from primary active transport against concentration gradient

The process by which a cell taken in an external substances by an inward pouching of the membrane to form a vesicle

Small spherical packages often found near the RER and Golgi apparatus that carry substances in, out and around the cell

The secretion of a substance from a cell when a vesicle joins with the plasma membrane

Secretion that occurs continually to maintain homeostasis

Secretion of substances that occurs in response to a specific trigger

Variation of endocytosis where cell takes in solid particles (cell eating)

Variation of endocytosis wherein a cell takes in extra cellular fluid (cell drinking)

• vesicle approaches membrane, the membranes of both are phospholipid bilayers meaning they share the same proteins • membrane fluidity facilitates the fusion of the cell and vesicle membranes • a temporary intermediate structure is formed when there is a point of contact consisting of a single phospholipid bilayer • membrane pores opens, allowing the contents of the vesicle to pass through • vesicle membrane then joins cell membrane • at no point is either membrane broken

• take in molecules like glucose • expel waste • cell defense • cellular homeostasis