movement of molecules across membranes-plasma membranes

Question 1

diffusion

Answer 1

• movement of molecules from a region of (THEIR) high concentration to a region of (THEIR) lower concentration, without the use of energy.

Question 2

what determines the rate of diffusion

Answer 2

concentration gradient.
Temperature.
Surface area.
Distance.
Mass of molecule

Question 3

what is facilitated diffusion

Answer 3

-molecules diffuse across the plasma membrane with assistance from transmembrane proteins in order to cross it’s hydrophobic core, such as channels and carriers

Question 4

when does diffusion need to be facilitated

Answer 4

• when a particular molecule cannot fit through the membrane due to their polarity or charge. Because they are charged or polar, they can’t cross the phospholipid part of the membrane without help
• Facilitated transport proteins shield these molecules from the hydrophobic core of the membrane, providing a route by which they can cross

Question 5

role of channel proteins

Answer 5

• Channel proteins (a type of transmembrane proteins) span the membrane and make hydrophilic tunnels across it, allowing their target molecules to pass through by diffusion
• Passage through a channel protein allows polar and charged compounds to avoid the hydrophobic core of the plasma membrane, which would otherwise slow or block their entry into the cell

Question 6

example of channel protein

Answer 6

channel proteins that allow water to cross the membrane very quickly, and they play important roles in plant cells, red blood cells, and certain parts of the kidney (where they minimize the amount of water lost as urine)

Question 7

role of carrier proteins in facilitated diffusion

Answer 7

-Carrier proteins are able to change their shape to allow a molecule to diffuse across the cell membrane
Like channel proteins, carrier proteins are typically selective for one or a few substances. Often, they will change shape in response to binding of their target molecule, with the shape change moving the molecule to the opposite side of the membrane
The carrier proteins involved in facilitated diffusion simply provide hydrophilic molecules with a way to move down an existing concentration gradient

Question 8

active transport

Answer 8

movement of molecules and ions across plasma membranes, against a concentration gradient. non passive process (requires energy)

Question 9

examples of active transport

Answer 9

glucose in blood

calcium/ other vitamins

Question 10

endocytosis

Answer 10

the process of a cell surrounding a substance with its plasma membrane and pinching off to form a vesicle. ( used when the molecule is too large to be taken into cell by carrier proteins)
-requires energy

Question 11

example of endocytosis

Answer 11

phagocytes use endocytosis to take in microorganisms and dead cells to be destroyed

Question 12

exocytosis

Answer 12

the process of releasing substances via vesicles pinching off from the sacs of the golgi apparatus and moving towards the plasma membrane

• they then fuse with the membrane and release their contents outside the cell
• requires energy

Question 13

hypotonic solution

Answer 13

solution with higher water potential than the cell

Question 14

hypertonic solution

Answer 14

solution with lower water potential than the cell

Question 15

isotonic solution

Answer 15

solution with the same water potential as the cell

Question 16

plasmolysis

Answer 16

cell becomes flaccid in a hypertonic solution + (membrane and cytoplasm pull away from cell wall)