transport In Cells Flashcards
What is passive transport
Substances move according to their own natural tendency without an input of energy from the cell
Describe simple diffusion
Net movement of a substance from an area of higher concentration to an area of lower concentration Down its concentration gradient until equilibrium is reached
Caused by the constant and random motion of all atoms and molecules which is caused by kinetic energy of the molecules
Diffusion results in equilibrium
Factors affecting rate of diffusion
Concentration gradient- the steeper the concentration gradient, greater rate of diffusion. For rapid diffusion, a constant supply of substance for diffusion needs to reach the cell surface and substances which have crossed the cell membrane need to be transported away
Distance over which diffusion occurs- shorter the distance over which diffusion occurs, greater the rate of diffusion across it
Surface area to volume ratio over which diffusion occurs- larger surface area to volume ratio, greater rate of diffusion
What is facilitated diffusion
Diffusion of ions and water soluble molecules across the cell membrane using two types of transport proteins, channel proteins and carrier proteins down a concentration gradient
It is a passive process and no energy is required
Once all transport proteins are used, rate of diffusion cannot be increased further
What are channel proteins
Provides a hydrophilic channel across the membrane for ions or hydrophilic molecules to enter or leave the cell
It is specific for the molecules that can move across the membrane
Carrier proteins
Diffusing substances bind temporarily to the carrier protein causing it to change shape to transport substances across the membrane
What is osmosis
Net movement of water molecules from a solution of higher water potential to a solution of lower water potential through a partially permeable membrane down a water potential gradient
More concentrated the solution is, lower its water potential
what is active transport
active transport is the movement of molecules or ions from a region of lower concentration to a region of higher concentration down its concentration gradient with the expenditure of energy from ATP molecules by the cell
important of active transport
allows cells to take up nutrients even when concentration outside is lower than inside of the cell
enables cells to get rid of waste products when their concentrations outside the cell is higher than inside the cell
the sodium potassium pump
an animal cell needs to maintain a much higher concentration of potassium ions and much lower concentration of sodium ions. the cell maintains this using active transport, pumping out sodium ions and potassium ions into the cell
the carrier protein used is sodium potassium pump
ATP is required for carrier protein to change its shape
three sodium ions are exchanged for two potassium ions
describe bulk transport across the cell
it is the transport of materials into and out of the cell by enclosing it within a vesicle. it allows large molecules like proteins and polysaccharides or large quantities of molecules leave and enter the cell without pass through the cell membrane. it is an active process which requires expenditure of energy by the cell
what is endocytosis
occurs when substances enter the cell by the inward folding of the cell membrane to form vesicles which seperates from the cell membrane. ATP is used to provide energy during this process. one example of endocytosis is the phagocytosis which is the process of engulfing/ ingesting foreign particles or food into the food vacuoles by amoeba. a key feature of phagocytosis is the formation of pseudopodia which are temporary protrusions of the cytoplasm. the vesicles formed after phagocytosis fuses with the lysosome and breaks down foreign particles.
excocytosis
substances from the secretory vesicles move towards and fuse with the cell membrane, contents in the vesicle are released into the fluid around the cell. ATP is used to provide energy during this process
important of cell transport
to absorb important nutrients
to expel metabolic waste to maintain homestasis
