CH 5 — membrane dynamics

Question 1

What are the 4 types of membrane proteins based on function?

Answer 1

1. membrane transport
2. structural proteins
3. membrane enzymes
4. membrane receptors

Question 2

What are the 2 types of membrane transport?

Answer 2

1. carrier proteins: active (primary/secondary), or passive
2. channel proteins (open/leaky, or gated —> mechanically, voltage, chemically/ligand)

Question 3

What types of membrane transport uses ATP?

Answer 3

active carrier proteins (primary uses ATP directly, secondary not directly)

Question 4

What types of membrane transport does not use ATP?

Answer 4

• passive carrier proteins
• facilitated diffusion
• open/leaky channel proteins
• gated channel proteins

Question 5

What are structural proteins used for?

Answer 5

used to anchor cell junctions and cytoskeleton

Question 6

What are membrane enzymes used for?

Answer 6

metabolism and signal transfer

Question 7

What are membrane receptors used for?

Answer 7

1. receptor mediated endocytosis
2. signal transfer
3. open and close chemically gated channels

Question 8

What fills channel proteins?

Answer 8

they have a water-filed pore in the center

Question 9

What determines what ions pass through a channel protein?

Answer 9

the structure (they are made of multiple protein subunits that assemble in the membrane

Question 10

What part of the channel allows ions to pass through?

Answer 10

the hydrophilic amino acids that line the channel

Question 11

What are the types of carrier proteins that regulate the number of molecules transported?

Answer 11

• unimportant carriers: move 1 molecule
• cotransporters: move more than one type of molecule (at different times) (can NOT move more than 3)

Question 12

What are symport carriers?

Answer 12

• carrier proteins
• all the things it moves go in the same direction

Question 13

What are antiport carriers?

Answer 13

• carrier proteins
• things go in opposite direction (one molecule to ECF, other to ICF)

Question 14

What are GLUT transporters?

Answer 14

• helps with passive transport (does NOT use ATP)
• always goes down concentration gradient
• facilitates the transport of glucose across the cell membrane

Question 15

How are carrier proteins (protein-mediated transport) DIFFERENT than channel proteins?

Answer 15

• never open to ICF and ECF at the same time
• does not actually “carry” because they stay in the membrane —> just changes shape

Question 16

What is primary (direct) active transport?

Answer 16

• a type of protein mediated transport from carrier proteins
• uses ATP directly
• ATP hydrolysis changes shape of the protein

Question 17

What is secondary (indirect) active transport?

Answer 17

• a type of protein mediated transport from carrier proteins
• uses potential energy stored in concentration gradients of one molecule to push another molecule against its gradient

Question 18

What is an example of using a carrier protein? Is it active or passive?

Answer 18

• Na K ATPase (sodium potassium pump)
• moves Na into the cell, and K out of the cell
• uses energy from ATP (hydrolyzes it)

Question 19

Slide 38 has sodium potassium pump

Question 20

What is an example of secondary active transport?

Answer 20

• SGLT (sodium-glucose cotransport)
• sodium and glucose transported into the ICF together
• the Na binds to create a high affinity for glucose
• No ATP used, just concentration gradient driving it

Question 21

What type of membrane protein exhibits specificity, competition, and saturation? What do they mean?

Answer 21

• carrier-mediated transport
  1. Specificity: moving only one molecule or group of related molecules
  2. Competition: transporter ay move related substrates, but those substrates compete with one another for binding sites (competitive inhibitor)
  3. Saturation: the rate of substrate transport depends on the substrate concentration and the number of carrier molecules

Question 22

What is phagocytosis?

Answer 22

the process by which a cell engulfs a particle into a vesicle by using the cytoskeleton to push the membrane around the particle
- actin mediated process
- the membrane surface pushes out
- is triggered by the presence of a substance to be ingested

Question 23

What is endocytosis?

Answer 23

• the membrane surface indents
• forms small vesicles
• constitutive: an essential function always taking place
• active: requires energy from ATP
• can be non selective (allowing extracellular fluid to enter the cell) or can be selective
• can be receptor-mediated endocytosis

Question 24

What is exocytosis?

Answer 24

• intracellular vesicles move to the cell membrane and fuse with it
• they then release their contents to the extracellular fluid
• cells use exocytosis to export large lipophobic molecules, get rid of wastes left in the lysosomes from intracellular digestion

Question 25

What is a phagosome?

Answer 25

the vesicle formed around ingested material during phagocytosis - site of digestion

Question 26

What is receptor-mediated endocytosis?

Answer 26

- takes place in regions of the cell known as “coated pits” (indentations where cytoplasmic side of the membrane has high concentrations of protein) - Most common protein found is Clathrin

Question 27

What is transcellular transport?

Answer 27

- transport through the epithelial cells themselves - crosses 2 membranes - uses combo of active and passive transport

Question 28

What is paracellular transport?

Answer 28

- transport thorugh the junctions between adjacent cells - very little in in “tight” epithelia (cell-cell junctions are like barriers)

Question 29

What is transcytosis?

Answer 29

- a combination of endocytosis, vesicular transport across the cell, and exocytosis - used to move macromolecules across an epithelium - makes it possible for large proteins to move across an epithelium and remain intact

Question 30

What is absorption?

Answer 30

transfer of substance from the lumen of the kidney or GI tract to the extracellular space

Question 31

What is secretion?

Answer 31

- when materials move from the ECF to the lumen - EX: salivary glands secret saliva - can also just mean the release of a substance from a cell

Question 32

What is the net charge of the ICF?

Answer 32

negative (compartments are in disequilibrium)

Question 33

What is the net charge between the ECF?

Answer 33

positive (compartments are in disequilibrium)

Question 34

What is the law of conservation of electrical charge?

Answer 34

the net amount of electrical charge produced in any process is zero - for every positive charge ion there is an electron on another ion - overall body is electrically neutral

Question 35

Which ion is the main regulator of membrane potential?

Answer 35

potassium (K+ leak channels) (most cells about 40x more permeable to K+ than Na+

Question 36

What does the nernst equation tell us?

Answer 36

- used for a cell that is freely permeable to only one ion at a time - equation used to calculate equilibrium potential for any concentration gradient - is not used to calculate the actual membrane potential of the cells

Question 37

What is depolarization, repolarization, and hyperpolarization?

Answer 37

1. depolarization: increase in RMP charge (more positive 2. repolarization: decrease in RMP charge (more negative) 3. hyperpolarization: happens after repolarization when the membrane becomes more negative

Question 38

What is the NA K ATPase used for in membrane potential?

Answer 38

helps maintain the resting membrane potential by removing Na+ that leaks into the cell and returning K+ that has leaked out

Question 39

Study the integrated membrane processes: insulin secretion (last couple of slides)