Active Transport Flashcards
- A cell uses the bond energy of ATP to move solutes across the plasma membrane.
- Requires input of energy
- Not dependent of the concentration gradient
- Key component: ATP
- requires carrier proteins that combine specifically and reversibily with the transported substances
- transporters or solute pumps move solutes, most importantly ions, “uphill” against a concentration gradient
Active Transport
If the carrier transports two substances simultaneously in the same direction
symport
If the carrier transports two different substances in opposite directions, the system is called ___
antiport
- Concentration is high in the extracellular fluid and low in the cytoplasm.
- Slowly diffuse into the cell
Sodium ion
- Concentration is low in the extracellular fluids and high in the cytoplasm.
- diffuse out of the cell
Potassium ion
- The carrier or “pump” is an enzyme called Na+ -K+ ATPase
- Mosy investigated example of primary active transport
Sodium-potassium pump
- The energy to do work comes directly from hydrolysis of ATP
- Hydrolysis of ATP results in the phosphorlyation of the transport protein.
- Causes the protein to change its conformation in such a manner that it “pumps” the solute across the membrane
Primary Active Transport
- A single ion pump creates a concentration gradient, the pump stores energy in the ion gradient
- This drives the transport of another substance that “hitches a ride”
- couple reactions: antiport and symport
Secondary Active Transport
- The concentration gradient of sodium provides the main driving force for secondary active transport.
- A carrier protein will co-transport gucose into a cell, but only after it first binds to sodium.
- Both sodium and glucose are transported into the cell
sodium-dependent glucose transport
- Always Active
- materials are moved into and out of the cell via membrane bound sacs called vesicles
- is used by the cell when bulk transport of large volumes of fluid and solutes are needed, or to transport specifif types of large molecules.
- endocytosis and exocytosis
Vesicular Transport
Moving substances into, across, and then out of the cell
transcytosis
Moving substances from one area (or membranous organelle) into the cell to another
vesicular trafficking
- The process by which materials are brought into the cell
- pinocytosis, phagocytosis, receptor-mediated__
Endocytosis
- Out of the cell
- secretion of cellular products such as digestive enzymes, and excretion or the elimination of degraded or indigestible material
Exocytosis
- Brings extracellular fluid into the cell
- “cell drinking”
- The plasma membrane forms a groove or pocket called a caveola, which surrounds a large volume of fluid.
- Eventually, the vesicle pinches off the plasma membrane forming an internal vesicle called endosome, aka pinosome.
Pinocytosis
When the plama membrane forms a groove or pocket
Caveola
When the vesicle pinches off the plasma membrane forming an internal vesicle
endosome/pinosome
- “cell eating”
- The cell engulfs some relatively large or solid material, such as a clump of bacteria, cell debris, or inanimate particles.
- A mechanism by which cells can bring in large amounts of solid material.
- Many types of single-celled organisms use this to ingest other smaller organisms, such as bacteria, that they need for their energy requirements.
- Some of the cells in our body are specialized in ____; their job is to ingest and destroy foreign material be it organic or inorganic debris.
Phagocytosis
- “False feet”
- cytoplasmic extensions
- forms when a particle binds to receptors on the cell’s surface and flow around the particle
- surround object being engulfed
pseudopodia
- The material that is surrounded by a vesicle made of plasma membrane
- endocytotic vesicle
- fuses with a lysosome and its contense are digested
- “Eating body”
phagosome
Cells that help protect the body by ingesting and disposing of bacteria, other foreign substances, and dead tissue cells.
phagocytes
“big eaters”
macrophages
- A selective process by which materials to be transported into the cell bind to plasma membrane receptors specific for that material.
- Receptors are localized to a small area of the plasma membrane
- The main mechanism for the specific endocytosis and transcytosis of mos macromolecules by body cells
- Allows cells to concentrate material that is present only in small amounts in the extracellular fluid
Receptor-mediated endocytosis
- The specific or “target” molecules are referred to as ___
- RME can transport these into the cell against steep concentration gradients
ligands
The receptors bound to their ligands form clusters on the plasma membrane in specific areas that have a “coating” of specialized proteins such as ____
clathrin
When material is engulfed, the endosomes are referred to as ___
coated vesicles
- The process by which material is transported out of the cell.
- Vesicular transport processes that eject substances from the cell interior into the extracellular fluid
- accounts for hormone secretion, neurotransmitter relaease, muscus secretion, and ejection of wastes
excocytosis
- Special type of exocytosis
- proteins such as mucous, horomones, or digestive enzymes that are synthesized by the cell are moved to the plama membrane in secretory vesicle
Secretion
The substance to be removed from the cell is first enclosed in a protein-coated membranous sac called ___
secretory vesicle
- Voltage across the membrane
- The potential difference represents stored energy which can be used for the cell to do work and is called ___
transmembrane potential
In their resting state, all body plasma membranes exhibit a ____ that typically ranges from -50 to -100 millivolts, depending on the cell type
resting membrane potential
When the resting membrane potential of cells ranges from -50 to -100 milivolts
polarized
