Chapter 6

Question 1

 Phospholipid bilayer

Answer 1

Hydrophilic phospholipid head regions with hydrophobic tails; Intracellular environment; Extracellular environment

Question 2

Transmembrane proteins(cross or anchor, embedded into membrane)

Answer 2

Form pores, channels; Anchor points for other things to attach

Question 3

Interior protein network

Answer 3

• Peripheral protein
• “twizzlers” can tie into them

Question 4

Cell surface markers

Answer 4

Anchors to extracellular matrix(ECM)
o Helps hold things in place, provides structure and stability
o Manipulated based on tissues it is supporting
o Two important things: important for immune system and how cells recognize each other!

Glycoprotein: has carbohydrate rings that form strings

Glycolipid: *if arrangement found, leaves alone; if arrangement not found, white blood cell will get rid of “invaders”

Question 5

Imaging the plasma membrane

Answer 5

Both transmission electron microscope(TEM) and scanning(SEM) used to study membranes
o Not the microscopes in lab, not able to reach that level
* One method to embed specimen in epoxy
o 1 micrometer shavings(imagine meat slicer at the deli)
o TEM shows layers

VIEW IMAGES

Question 6

Freeze Fracture

Answer 6

• Take tissue with cells
• Use glorified deli slicer to separate layers
• Reveals fluid of mosaic model of plasma membranes

Question 7

Disproving the fluid mosaic model

Answer 7

• If cut, will not be smooth like sandwich model, which was disproved
• As the name suggests, fluid moving layer(not a lot, but enough to bob around like a boat in a lake)

Question 8

Ways to alter membrane fluidity:

Answer 8

o Increase amount of saturated fatty acids DECREASES fluidity
o Increase of cholesterol DECREASES fluidity
o Increase of temperature INCREASES fluidity

Question 9

The many uses of membrane proteins

Answer 9

transporter, enzyme, cell surface receptor, cell surface identity marker, cell-to-cell adhesion, attachment to the cytoplasm

Question 10

Passive diffusion

Answer 10

motion of molecules drives the spread
* Concentration gradients are followed
* No energy needed, just the random motion of molecules
* Small, uncharged molecules go through membrane
* Small, polar molecules may diffuse too, just more slowly
o Even though tails are hydrophobic, water is so small that it passes through easily
* Some things diffuse readily through a cell membrane

Question 11

Facilitated diffusion

Answer 11

some molecules diffuse with “help” from a special carrier proteins; some things too big/too polar to go through plasma membrane

Has special protein channels that can work both ways; can open and close to one side or the other

protein channel facilitated motion of molecules across the membrane

No energy required; concentration gradients are followed, still a form of diffusion

Temporary ionic bond to go in one side and out the other
* Example: Glucose(charged stuff like ions)

Question 12

Osmosis

Answer 12

• Semipermeable membrane: solutes stay in place, water diffuses through the membrane
  o Water is polar, but is very small so it can sneak through
  o Cells may also have special channels called aquaporins also assist water by moving it faster/in large amounts
• Special case of diffusion

IMAGE PG 30

Question 13

Tonicity

Answer 13

• Hypotonic: low solute concentration
• Hypertonic: high solute concentration
• Isotonic: equivalent
• **Comparison with solution and cell environment; always discuss the extracellular solution relative to the intracellular environment!

Question 14

Secondary Active Transport/Couple transport

Answer 14

• energy not directly consumed, but a concentration gradient is need to drive it!
• One molecule moves down concentration gradient, other moves against
• Co vs. Counter-transport

Question 15

Permeability

Answer 15

o Small, uncharged polar molecules
 Need a bit of help, not tons, just a bit
o Large uncharged polar molecules
 Facilitated diffusion
o Small ions
 Facilitated diffusion (or active transport?)

IMAGE VIEW

Question 16

Endocytosis

Answer 16

bulk transport

three types: phagocytosis, pinocytosis, and recepter mediated endocytosis

Question 17

Endocytosis

Answer 17

bulk transport

three types: phagocytosis, pinocytosis, and receptor mediated endocytosus

Question 18

Endocytosis

Answer 18

bulk transport

three types: phagocytosis, pinocytosis, and receptor mediated endocytosis

Question 19

Phagocytosis

Answer 19

Pinched off vesicle to hold one big bacterial cell to be digested

VIEW IMAGE PAGE 31

Question 20

Pinocytosis

Answer 20

 Small solute particles outside cell
 Pinch of vesicle with intent to house multiple small solute particles

VIEW IMAGE PAGE 31

Question 21

receptor mediated endocytosis

Answer 21

 Want to grab a molecule and only one type of that molecule
 Has various protein receptors to get target molecule
 Clathrin pinches off into vesicle with multiple coated pits and receptor proteins

VIEW IMAGE PAGE 32

 Example: LDL receptors of hypercholesterolemia
* In this human genetic disease, receptors lack tails so they are never fastened in the clathrin coated pits
* This means they will not trigger vesicle formation
* It accumulates inside ateries as plaque and can lead to heart attacks

Question 22

Exocytosis

Answer 22

discharge of materials out of the cell
* Used in plants to export cell wall material
* Used in animals to secrete hormones, neurotransmitters, digestive enzymes