Intercellular Transport (1.4) Flashcards
Membranes control the composition of cells by ____
Active and Passive transport
Passive transport includes what type of movements?
Simple diffusion, Facilitated diffusion, and Osmosis
What makes active transport different from passive transport?
It requires the utilization of energy, is an energy-demanding process, and can occur via a pump protein, or may involve bulk transport by endocytosis and exocytosis.
Why do cell transport substances in and out of the cell?
Cells need to both import and export material for their survival. Materials essential for cell metabolism, including glucose, hormones, and ions, are imported. Waste products that are toxic to the cell, as well as useful substances that need to be secreted, such as enzymes and hormones, are exported.
Other reasons for transporting substances across the cell membrane include cell defense (for example, phagocytosis by white blood cells kills pathogens) and cellular homeostasis (for example, maintaining the osmotic pressure in a cell).
What is diffusion?
Diffusion is the movement of particles from a region of high concentration to a region of low concentration and is the result of the random motion of particles.
What factors alter the rate of diffusion and how?
Temperature – molecules diffuse faster if the temperature is higher.
Surface area of membrane – an increase in surface area allows more molecules to diffuse.
Size of particles – smaller molecules diffuse faster than larger ones.
Concentration gradient of diffusing particles – the bigger the gradient the faster the diffusion.
How does simple diffusion happen?
Simple diffusion occurs in a gas or liquid medium and only requires a concentration gradient. It occurs in both living and non-living systems.
(e.g. if ammonia gas is released at one end of the laboratory, it quickly diffuses through the whole room and can soon be detected by all students in the room. The molecules of ammonia have simply diffused by random movement until the gas was uniformly distributed in the laboratory, in which case a state of equilibrium has been reached.)
What limits simple difussion?
Large particles, if a particle is too big, it cannot pass through the phospholipid bilayer of the membrane.
(e.g. charged particles (ions) are repelled by hydrophobic tails in the membrane. When simple diffusion fails, facilitated diffusion can transfer the particle across the membrane.)
What is facilitated diffusion reliant on?
It requires channel proteins or carrier proteins, which are specific to the molecules being transported across the plasma membrane. The size and shape of protein carriers and channels determine what substance can cross the membrane.
(e.g. An example is chloride ion channels that only allow the facilitated transport of chloride ions and potassium ion channels that will only allow the passage of potassium ions.
How does movement work in diffusion?
All forms of diffusion require a substance to move from a higher concentration to a lower concentration.
Define Osmosis
Osmosis is the passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration across a partially permeable membrane.
What’s so special about solutes in osmosis?
They do not move, thus, only water molecules will have to balance the environment.
What is a hypertonic environment?
The solution with the higher concentration of solutes
What is a hypotonic environment?
The solution with the lower concentration of solutes
How is the water movement in Osmosis?
Water always moves by osmosis from the hypotonic solution to the hypertonic solution.
What is the difference between flaccid, turgid, and plasmolyzed?
Flaccid:-
A flaccid plant cell is not swollen and the cell membrane does not press against the cell wall tightly. This occurs when a plant cell is placed in an isotonic solution. Flaccidity refers to the state between turgidity and plasmolysis in which the plasma membrane is not pushed against the cell wall.
turgid:-
A turgid cell is a cell that has turgor pressure. The plant that looks healthy (i.e. not wilted) has cells that are turgid. Turgidity refers to the state of being turgid or swollen due to high fluid content inside the cell.
plasmolyzed:-
shrinking of the cytoplasm away from the wall of a living cell due to the outward osmotic flow of water. Plasmolysis is a typical response of plant cells exposed to hyperosmotic stress. The loss of turgor causes the violent detachment of the living protoplast from the cell wall.
Show how active transport involves protein carriers in the movement of a substance from the outside to the inside of a cell. Include location, molecule concentration, type of protein involved, role, and effects of ATP.
What’s the difference between Phagocytosis and Pinocytosis?
