exam 2 module 5 Membrane Transport Flashcards
concentration gradient
a solute is more concentrated in one region than in a neighboring region.
- the image below, the tea is more highly concentrated near the tea bag than in the rest of the cup, forming a concentration gradient.
passive transport (Does Not Require Energy Input)
a) diffusion- All forms of passive transport involve diffusion. the movement of a substance from a region where it is highly concentrated to an area where it is less concentrated.
simple diffusion( No Protein Required)
a) example: O2 and CO2
-oxygen (O2) and carbon dioxide (CO2) can easily pass through the hydrophobic regions of the membrane. This is impossible for large polar molecules, such as glucose.
osmosis
a) red blood cells (demonstrates the effect of osmosis)
i) isotonic solution(iso- equal)- the plasma’s solute concentration is the same as the inside of the cell. Therefore, water moves into and out of the cell at equal rates
ii) hypotonic solution(hypo-means under)- water moves inside the cell because the cell has more solutes. Since animal cells lack a cell wall, the membrane may even burst.
iii) hypertonic solution(hyper-means over)- it will lose water. A cell placed in a hypertonic environment loses water, shrivels, and may die.
osmosis definition
simple diffusion of water across a selectively permeable membrane.
passive transport definition
substance moves across a membrane without the use of energy
plant cell
i) turgor pressure
ii) hypotonic solution( pic of healthy flowers)
iii) hypertonic solution- water leaves the cell, so turgor pressure is low. The plant wilts.(pic of wilting flowers)
turgor pressure
force of water pressing on the plant cell wall
facilitated diffusion
membrane protein assists the movement of a polar solute down its concentration gradient
facilitated diffusion example
a) examples: ions (H+) and polar molecules (glucose)
-Ions (ex., H+) and polar molecules (ex., glucose) cannot pass through the hydrophobic layer of the cell membrane. Instead, transport proteins help these solutes cross
Facilitated diffusion occurs
in either direction depending on the concentration gradient of the molecules.
active transport defintion
moves a substance across a membrane against its concentration gradient, from where it is less concentrated to where it is more concentrated
active transport
a) example: sodium-potassium (Na+/K+) pump
-Cells must contain high levels of potassium (K+) and low concentrations of sodium (Na+) to perform many functions.
- For example, essential for nerve and muscle function.
sodium-potassium pump
used to create the needed gradient. The pump uses ATP as an energy source to move 3 Na+ outside the cell for every 2 K+ it admits inside the cell (figure 4.19).
The sodium-potassium pump function is to pump
sodium ions out of the cell and potassium ions into the cell.
Endocytosis and Exocytosis Use transport in vesicles
a) endocytosis- a cell membrane engulfs fluids and large molecules to bring them into the cell. A small portion of the membrane goes inward and traps the particles.
(The two main forms of endocytosis are pinocytosis and phagocytosis.)
i) pinocytosis- cell engulfs small amounts of fluid and dissolved substances
ii) phagocytosis- cell captures and engulfs large particles, such as debris and even another cell
iii) receptor-mediated endocytosis- form of endocytosis in which receptor proteins on the cell surface are used to capture specific target molecules that are engulfed into the cell.
Endocytosis and Exocytosis Use transport in vesicles
a) endocytosis- a cell membrane engulfs fluids and large molecules to bring them into the cell. A small portion of the membrane goes inward and traps the particles.
(The two main forms of endocytosis are pinocytosis and phagocytosis.)
i) pinocytosis- cell engulfs small amounts of fluid and dissolved substances
ii) phagocytosis- cell captures and engulfs large particles, such as debris and even another cell
iii) receptor-mediated endocytosis- a form of endocytosis in which receptor proteins on the cell surface are used to capture specific target molecules that are engulfed into the cell.
Endocytosis and Exocytosis Use transport in vesicles part 2
b) exocytosis
- the opposite of endocytosis. The process uses vesicles to transport fluids and large particles out of cells
Which of the following are examples of exocytosis?
a. The release of antibodies from white blood cells
b. A macrophage engulfing a pathogen to destroy it
c. The transport of chemical messengers (or neurotransmitters) out of nerve cells
d. The absorption of water by a red blood cell
the answer is a and c,
a.
During exocytosis, materials are transported from the inside to the outside of the cell in membrane-bound vesicles that fuse with the plasma membrane. The release of antibodies from white blood cells is a form of this process.
c.
During exocytosis, materials are transported from the inside to the outside of the cell in membrane-bound vesicles that fuse with the plasma membrane. The outward transport of neurotransmitter is a form of this process.
