4.2 Cell transport mechanisms Flashcards
What does a glycoprotein do?
often acts as antigens that are important for cell recognition or as receptors for hormones / neurotransmitters
this sets up a cascade of reactions within the cell
What are peripheral proteins?
may be enzymes - can be involved in regulating transport e.g. by cell signaling
What are integral proteins?
the main transport system of the membrane forming either hydrophilic channels (permanent pores) or other transport mechanisms
What is diffusion?
movement of particles in a liquid or gas down a concentration gradient through random movements
What can diffuse through a cell membrane?
small particles e.g. oxygen and carbon dioxide
What is facilitated diffusion?
diffusion that takes place through carrier proteins or protein channels
only possible because of the protein lined pores of the cell membrane
What is osmosis?
the movement of particles in a liquid (usually water) from an area of high concentration to an area of low concentration, down a concentration gradient, through a partially permeable membrane
What is endocytosis?
movement of large molecules into the cell through vesicle formation
What is exocytosis?
movement of large molecules out of the cell through vesicle formation
What is active transport?
the movement of substances across a cell membrane, against a concentration gradient, using ATP
How does the solubility of a molecule affect the way its transported?
substances that dissolve in lipids can easily pass through cell membranes
and water acts as a solvent for ionic species
How does the size of a molecule affect the way its transported?
small molecules can freely diffuse across cell membrane
large molecules require facilitated diffusion - channel proteins and carrier proteins
How does the charge of a molecule affect the way its transported?
charged particles require specific channel proteins e.g. sodium ion channel
some channels are only open if a specific molecule/electric charge is present
What is osmotic concentration?
a measure of the concentration of the solutes in a solution that have an osmotic effect
What is pressure potential?
a measure of the inward pressure exerted by the plant cell wall on the protoplasm of a cell, opposing entry of water by osmosis - usually a positive value
What does isotonic mean?
a solution where the concentration of the solutes is the same as that in cells
What does hypotonic mean?
a solution where the concentration of the solutes is lower than that in cells
What does hypertonic mean?
a solution where the concentration of the solutes is higher than that in cells
What does it mean if a plant is turgid (turgor)?
state of a plant cell wall when the solute potential causing water to be moved into the cell by osmosis is balanced by the force of the cell wall pressing on the protoplasm
What is turgor pressure?
unit (P)
a measure of the inward pressure exerted by the plant cell wall on the protoplasm of the cell as the cell contents expands and press outwards, a force opposing the entry of water by osmosis
What is incipient plasmolysis?
a point when so much water has moved out of the cell by osmosis that turgor is lost and the cell membrane begins to pull away from the cell wall as the protoplasm shrinks
What is plasmolysis?
situation when a plant cell is places in hypertonic solution and so much water leaves the cell by osmosis that the vacuole is reduced and the protoplasm is concentrated and shrinks away from the cell wall
What is water potential?
unit (Ψ)
a measure of the potential for water to move out of a solution by osmosis
What is osmotic potential?
unit (π)
a measure of the potential for a solution to cause water to move into the cell across a partially permeable membrane as a result of dissolved solutes
What is the equation for water potential?
water potential (Ψ) = turgor pressure (P) + osmotic potential (π)
Describe the role of ATP in active transport?
the enzyme ATPase catalyzes the hydrolysis of ATP into ADP and a phosphate to provide energy
How are large molecules transported through vesicle formation?
a form of endocytosis could have occurred:
- phagocytosis - when a cell engulfs something large and encloses it into a vesicle
- pinocytosis - when cells take in tiny amounts of extracellular fluid into vesicles
- exocytosis
How does the hydrolysis of ATP provide an accessible energy supply for biological processes?
ATPase catalyzes hydrolysis of ATP
- breaking 1 bond and forming 2 more to provide energy needed to move carrier systems in the membrane or release transported substances
What does the phosphorylation of ADP to _ _ _ require?
energy
to form ATP
