Osmosis and Diffusion Flashcards
What is the cell membrane made of?
A phospholipid bilayer that is fluid.
Fluid mosaic model
The phospholipids and all the other proteins in, around, on top of, and underneath the membrane.
Why is the word “mosaic” significant?
It refers to the membrane being a mixture of proteins in the bilayer functioning in transport, cell recognition, and binding.
Semi-permeable membrane
Molecules like O2 and CO2 can move through, others require transport proteins, and others cannot move through at all.
Define diffusion.
The movement of molecules from an area of high concentration to an area of low concentration until equilibrium is reached.
What does the rate of diffusion depend on?
The medium (solid, liquid, or gas), temperature, and concentration.
If temperature increases, the rate of diffusion…
Increases.
Equililbrium
An equal amount is dispersed throughout.
Concentration gradient
The direction of the flow (high to low).
Facilitated diffusion
Diffusion with help. Help=proteins moving molecules into the cell.
Osmosis
Diffusion of water from high to low concentration until equilibrium is reached.
Osmotic pressure
The force of osmosis.
Isotonic medium
There is an equal number of solutes inside and outside the cell. Water moves in and out.
“Iso” means
Balanced.
Hypertonic medium
There are more solutes outside the cell than inside the cell. Water moves out of cell (high to low concentration). Cell volume shrinks.
Hypotonic medium
There are more solutes inside the cell than outside the cell. Water moves into the cell. Cell can balloon up and possibly burst.
Isotonic medium 2
Concentration is equal on both sides of the membrane, no net movement. Water moves in and out of animal cells; not plant cells because of cell wall.
In which medium do cells function best?
Isotonic.
Hypotonic medium 2
High concentration of water OUTSIDE the cell, cell gains water.
How does a cell wall help a plant cell in a hypotonic medium?
A cell wall keeps the plant cell from bursting due to the growing vacuole and (?) membrane.
Hypertonic medium 2
More water inside the cell, more solute outside. Cells lose water.
Turgor/osmotic pressure
The pressure building in the cell as it continually takes in water. Can lead to eventual bursting in animal cells.
What can a hypertonic medium do to an animal cell?
It can dehydrate it.
What can a hypertonic medium do to a plant cell?
Plagmolysis: Membrane and organelles in plants shrink because of water loss. Cell wall stays the same.
Active transport
Movement of molecules from low to high concentration, requiring energy (ATP) and membrane proteins.
Examples of active transport?
Liver and intestines absorbing nutrients/sugar in digestion, root cell absorbing minerals, kidney absorbing ucrea from blood, plant spending energy taking minerals into cells from dirt.
Endocytosis
Engulfing molecules too big for diffusion. Producing a vesicle to bring the particles into the cell.
What is one kind of endocytosis?
Phagocytosis, in which large, solid molecules are transported into the cell.
An example of phagocytosis?
An amoeba eats a protist that is about its size by oozing its cell membrane around the protist and digesting it.
Exocytosis
Releasing the food waste particle after digestion.
How might a substance such as a digestive enzyme be produced, stored, and then secreted from the cell?
The DNA in the nucleus has directions for ribosomes to make proteins. The ribosomes are made in the nucleolus. (Digestive enzymes are a type of protein.) The proteins are transported through the rough ER and then collected and stored in the Golgi body. They are then transported from the Golgi body when the ends of the Golgi body pinch off to form a vesicle around the protein. Mitochondria are needed to produce energy for the exocytosis of the protein, which means that the protein leaves the cell in the vesicle which becomes a part of the cell membrane once it pushes the protein out after traveling through the cytoplasm.
