Lecture 17 - Plasma Membrane & Transport in and out of Cells

Question 1

plasma membrane primary function:

Answer 1

to separate the internal and external environments of the cell

Question 2

plasma membrane other functions:

Answer 2

(1) receiving information

(2) capacity for movement and expansion

(3) import and export of small molecules

Question 3

as well as phospholipids in the bilayer there are also…

Answer 3

… steroids (e.g: cholesterol) and glycolipids that make up the membrane

Question 4

most common name for the “head” of the phospholipid:

Answer 4

phospatidylcholine

Question 5

what does the phospholipid bilayers form in water:

Answer 5

phospholipids form vesicles in water, they are very useful in research for drug transport due to our ability to add markers for specific cell types

Question 6

anchors work to either:

Answer 6

can either work by interacting with external materials to hold the cells in place or interact with cytoskeletal molecules and allow the cell to maintain its shape

Question 7

what could/couldn’t pass through a phospholipid bilayer that is purely lipids with no proteins?

Answer 7

small non polar molecules (e.g: O2, CO2, N2 & steroid hormones) pass right through, small & large uncharged polar molecules can pass through to a certain extent depending on the concentration gradient and ions cannot move at all without the aid of proteins

Question 8

simple diffusion:

Answer 8

reliant on concentration gradient with particles moving from a high to low concentration
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anything that passes through it is either hydrophilic or not affected by water loving/hating properties

Question 9

anything with a pump =

Answer 9

ATP

Question 10

facilitated diffusion:

Answer 10

moves particles from an area of high concentration to an area of low concentration

moving chemicals across the membrane requires an integral bridge

Question 11

channel proteins:

Answer 11

channel proteins create a middle channel that is hydrophilic and allows particles that cannot simply diffuse across

usually the channel needs a stimulus to open (ie: ligand interacting with binding site) which causes conformational change in the protein shape so it can function

Question 12

aquaporins:

Answer 12

highly specialised channel proteins that enable water to move very quickly across the membrane

Question 13

main example of glucose transporters and function:

Answer 13

GLUT4

(1) insulin binds to receptor

(2) signal cascade

(3) exocytosis of GLUT4 containing vesicles

(4) glucose entry permitted

Question 14

types or active transporters:

Answer 14

uniporters (one substance one direction), symporters (two different substances but same direction) & antiporters (two different substances different directions

Question 15

how doles the intestinal and renal proximal tubule transport sodium and glucose?

Answer 15

via secondary co-transport where the Na+/glucose co-transporter (SGLT1) simultaneously transports two Na+ ions and one glucose molecule across the plasma membrane