transport mechanism

plasma membrane

• serves as the boundary between the cell’s internal and external environments. Regulates all substances that enter and exits the cell

• exhibits selective permeability, which is why it is referred to as a semi-permeable membrane

phospholipid

the main body of the plasma membrane is composed of an amphipathic molecule known as

water-loving

what does hydrophilic means

water-fearing

what does hydrophobic means

transmembraneproteins

• these are proteins that regulate the movement of molecules across the membrane

• these proteins form the transport mechanisms of the cell

• channels, barriers, and receptor proteins

interior protein network

• determines and maintains the structure and form of the plasma membrane

cell-surface markers

• responsible for the recognition of foreign and local (self) cells and tissues

• also responsible for glycoproteins and glycolipids

protein and protein complexes

responsible for the majority of internal and external interactions

transporters

• channels/ carriers

• responsible for the movement of molecules/solute across the membrane

enzymes

• a specialized protein that is required for the cells metabolic functions

cell-surface receptors

• detects chemical messages from the environment to elicit reactions

• the signaling molecule may cause the protein receptor to change shape in order to relay the message inside the cell

cell-surface identity markers

• are combinations of surface proteins and protein complexes that specify the type and origin of the cell

cell to cell adhesion proteins

• bonds and junctions between cells

• these bonds may be permanent or temporary depending on the location, function, and type of cells being connected

attachment to the cytoskeleton

• responsible for anchoring other surface proteins to the cytoskeleton and extracellular matrix

• proteins attach to microfilaments non-covalently to maintain shape, stability, and coordinate chemical/mechanical changes.

• oxygen

• carbon dioxide

Molecules and solutes constantly pass through the cell as chemical reactions occur respiration requires _______ to enter cells and _______ ________ to move out.

transport mechanism

allows the cell to regulate what solutes enter/exit the cell and the quantity being transported

passive transport

• relies on the concentration gradient of solutes to move them across the plasma membrane

• no energy will be spent

diffusion

movement of ions and molecules from high to low concentration

simple diffusion

• lipid soluble molecules and ions that can pass freely through the membrane

• no proteins or energy involved

facilitated diffusion

• small molecules may still be unable to pass due to their charge

• proteins manage and assist the movement of solutes across the membrane

channel proteins

• provide a small, hydrophilic passageway for specific molecules and ions

• remains open most of the time

latter

referred to as gated channels and can react to a chemical or electrical stimulus

carrier proteins

• requires the molecule being transported to attach itself to the carrier protein

osmosis

• movement of water from high concentration of solutes to low concentration across membranes

• semipermeable membrane

osmotic balance

causes water to move in the direction of the solutes until the number of free water molecules is equal

tonicity

the difference in osmotic concentration which leads to the movement of water

hypertonic

higher concentration of solutes

hypotonic

low concentration of solutes

isotonic

no difference in osmotic concentration

hypotonicity

• the concentration gradient formed by the solutes inside the cell would cause water from the environment to rush inside

• causes the cell to swell and eventually burst or lyse

hypertonicity

• the water inside the cell would rush out to try and balance the concentration gradient

• causes the cells to shrivel and dry

aquaporins

these channels allow water molecules to move across the membrane in large quantities

active transport

• this type of transport mechanism relies on the expense of cell energy, adenosine triphosphate (ATP)

• makes use of protein transporters similar to facilitated diffusion in the sense that the molecule needs to bind with the protein receptor via the active site

primary activity transport

is an intentional and uphill mode of transport where a transport protein directly uses energy from ATP phosphorylation

secondary active transport

• usually seen as the aftermath of primary active transport

• a molecule is transported due to the difference in energy from the phosphorylation of energy—does not use the energy directly

coupled / co-transport

this method of transport happens when one protein shuttles two different molecules across the membrane in the same direction

uniport

one way transport

• symport (both up)

• antiport (up and down)

2 types of co-transport