Cell biology (pt.2) Flashcards
define active transport
Active transport is a process where substances are transported across the cell membrane up their concentration gradient.
what does it enable
This process enables cells to absorb substances that are already more concentrated in the cytoplasm than the extracellular
fluid.
how does active transport work
Active transport usually involves pumps and carrier proteins, which combine specifically and reversibly with the
transported substances. Active transport requires the use of energy in the form of ATP.
which three substances are transported via active transport
sugars (glucose)
amino acids
what moves via carrier proteins
sugars (glucose)
amino acids
define vesicular transport (4) (last part)
Vesicular transport is a process whereby large particles and macromolecules are transported through the cell membrane in
bubblelike vesicles. This process requires the use of energy in the form of ATP.
derfine exocytosis (4)
Exocytosis is the process of transporting particles from the cell interior into the extracellular space. Cells that secrete materials
in this manner include nerve cells, goblet cells, pancreatic cells and exocrine cells.
define endocytosis (4)
Endocytosis is the process of transporting particles into the cell’s interior from the extracellular space.
The electron micrograph below shows a cell undergoing exocytosis.
what moves via exocytosis (4)
macromolecules
what are the types of endocytosis (4)
There are three forms of endocytosis: phagocytosis, pinocytosis and receptor-mediated endocytosis.
what is phagocytosis
Phagocytosis (cell eating) is the process where a cell engulfs large particles by surrounding the substance with footlike
extensions of the cell membrane (pseudopods) and trapping the substance into a vesicle (phagosome) in the cytoplasm
where it then merges with a lysosome (containing enzymes) forming a phagolysosome. Enzymes contained in the
phagolysosome then digest the substance.
what is pinocytosis (4)
Fluid phase pinocytosis (cell drinking) is the vesicular intake of droplets of extracellular fluid into the cell. The plasma
membrane sinks in at points forming pits which separate from the surface membrane forming membrane-bound pinocytotic
vesicles in the cytoplasm.
what is receptor-mediated endocytosis (4)
Receptor-mediated endocytosis enables a cell to selectively take in specific molecules from the extracellular fluid with a
minimum of associated fluid. Specific solute particles bind to receptors on the plasma membrane and are then taken into the
cell in clathrin-coated vesicles.
membrainous organelles (4)
These organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi complex (apparatus), Golgi vesicle and
lysosomes.
what is diffusion
Diffusion is the net movement of molecules from an area of high concentration to an area of low concentration.
what is passive diffusion
Passive
diffusion is a process that does not require the expenditure of energy.
what factors affect diffusion rates (4)
Diffusion rates through a membrane can depend upon
many factors including temperature, molecular weight, concentration gradient, membrane surface area and membrane
permeability.
two substances that move through simple diffusion
Simple diffusion is a passive transport process which does not require a membrane transport protein.
what is osmosis
Osmosis is a special case of passive diffusion involving movement of water molecules across a semi-permeable membrane
from an area of high water concentration to an area of low water concentration.
what is osmotic pressure
Osmotic pressure is a measure of the driving force for diffusion of water molecules across a semi-permeable membrane. In the animation, the membrane was permeable to the solvent, H»O, but not to the solute, urea.
what is osmotic pressure proportional to
Osmotic pressure is proportional to the concentration of the non-permeating
÷
solute
÷
I particles.
what is tonicity (4)
membranes. The ability of a solution to change the water content of a cell is called tonicity. Solutions which do not change the cell water content are called isotonic solutions.
what is channel diffusion
CHANNEL DIFFUSION - SMALL POLAR OR IONISED SUBSTANCES. Proteins in the membrane form channels or pores
- water
- ions
what is facilitated diffusion
Facilitated diffusion is the carrier-mediated transport of a solute (that would otherwise be unable to pass through the membrane unaided through a membrane down its concentration gradient.
