Passive yransporttt Flashcards
Types of Passive Transport
Simple
Facilitated
Osmosis
Simple
= Diffusion through the phospholipid bilayer
Facilitated Diffusion
= Diffusion with the help of transport proteins
Osmosis
Diffusion of water
passive Transport definitions
SOLUTE: Substances dissolved in solvent
SOLVENT: A liquid in which a substance a substance ( solute) is dissolved in
CONCENTRATION GRADIENT: Difference in concentration between two areas
OSMOSIS: The movement of water molecules across a membrane
Passive Transport Characteristics
- cells use NO ENERGY
- Molecules move randomly down a concentration gradient
- HIGH solute to LOW ( permeable)
What is diffusion
The RANDOM movement of molecules/solutes from high solute to low
- continues with ( equilibrium) due to kinetic energy
SIMPLE Diffusion
molecules such as:
- Oxygen, Carbon, fat solute, water
can move DOWN the concentration gradient
- Directly through phospholipid bilayer
- because they are small, hydrophobic non-polar
FACILITADED Diffusion
- Polar Hydrophilic substnaces such as
- Amino acids, glucose, charged molecules or ions—-> move into the cell
( down) gradient
BUT must be assisted by Channel protein or carrier protein
OSMOSIS (diffusion of water)
Osmosis: movement of water through a selectively permeable membrane. (*not solutes)
Water moves from a low solute to a high solute concentration.
Water moves through the lipid bilayer as it is small or through protein pores called AQUAPORINS
Water moves as the solute cannot move ( it is impermeable)
Tonicity
The osmosis of water is another way for cells to maintain homeostasis. When the membrane is impermeable to the solute, water can enter or exit the cell to dilute or concentrate the amount of solute.
Hypotonic Solution
Hypotonic: The solution has a LOWER concentration of solutes and a higher concentration of water than inside the cell.
(Low solute; High water = Dilute solution)
- A hypotonic solution has more water and fewer dissolved substances (solutes) compared to the inside of a cell.
Think of it like this:
Imagine a cell sitting in freshwater (which has very few solutes).
Since water moves from where there’s more of it to where there’s less, water will rush into the cell.
This can make the cell swell up and even burst like an overfilled balloon.
Hypertonic Solution
: The solution has a HIGHER concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water = concentrated solution))
he’s skinny because he has no water in him
A hypertonic solution has less water and more dissolved substances (solutes) compared to the inside of a cell.
Think of it like this:
Imagine a cell sitting in saltwater (which has a lot of solutes).
Since water moves from where there’s more of it to where there’s less, water will leave the cell.
This can make the cell shrink and shrivel up,
Isotonic Solution
Isotonic: The concentration of solutes in the solution is EQUAL to the concentration of solutes inside the cell.
How Organisms Deal with Osmotic Pressure
Bacteria and plants have cell walls that prevent excessive expansion. In plants, the pressure against the cell wall is called turgor pressure, making the cell turgid. Protists like Paramecium have contractile vacuoles that collect and expel excess water to prevent over-expansion and bursting.
