3. Plasma Membrane

Question 1

Normal Saline

• -___mEq
• -9% NaCl = ___g/100ml

Answer 1

300 mEq
9g/100ml
=154mmol/L = 0.308mEq

Question 2

Small cells are necessary for ___ chemical concentrations and ____ rates; This high concentration causes osmotic potentials.

Answer 2

high

reaction

Question 3

Adaptations for water management;
Plant cells –> walls
Animal cells –> ??

Answer 3

pump

Question 4

Sodium Potassium pump

Answer 4

Designed to counter osmolarity, eventually led to rapid action potentials

Question 5

Differences in solution composition ______

Answer 5

do not affect osmolarity

Question 6

Assisted Membrane Transport.

Transport Attributes:

Answer 6

Specificity
Saturation
Competitiveness

Question 7

Specificity

Answer 7

each receptor only responds to specific molecules

Question 8

Saturation

Answer 8

If all receptors are used, rate of transfer cannot increase, regardless of concentration

Question 9

Competitiveness

Answer 9

If two chemicals use, bind or block the same carrier, the transport of both may decrease

Question 10

Carrier Mediated Transport is either

Answer 10

active or passive

Question 11

Passive

Answer 11

Energy comes from concentration gradient (higher to lower); no ATP required

Question 12

Facilitated Passive Diffusion
-protein assisted passive diffusion
Requires a ___ in ____ state (often results in conformational change)

Answer 12

change

affinity

Question 13

Active Carrier Mediated Transport

Answer 13

Uses ATP and a carrier molecule to move a substance against the concentration gradient (lower to higher)

Question 14

Vesicular active transport

Answer 14

uses a lot of energy to move a lot of stuff (involves membrane structural changes)

Question 15

Pinocytosis - non-clathrin mediated fluid intake

Receptor Mediated Endocytosis - clathrin mediated pinching of substances bound to membrane

Answer 15

Examples of vesicular transport

Question 16

Primary active transport

Answer 16

Direct use of ATP to move molecule

Proteins cannot be made to move faster

Question 17

Secondary Active Transport

Answer 17

Transports two materials at the same time on a single transporter

Question 18

Antiporter

Symporter

Answer 18

Examples of secondary active transport

Question 19

antiporter

Answer 19

moves two molecules in opposite directions (one w/gradient and the other against)

Question 20

symporter

Answer 20

moves two molecules in the same direction

Question 21

Glucose symporter used in the ___.

Sodium moves down concentration gradient, and glucose moves with it through same ____.

Answer 21

intestine

carrier

Question 22

Glucose-Na symporter uses ____ at the sodium extrusion point (where Na+ is pumped back out to maintain ____)

Answer 22

ATP

osmolarity

Question 23

Membrane Proteins

Answer 23

Functions:
 Form channels across membrane, Carrier molecules, Docking-marker acceptors, Membrane-bound enzymes, Receptor sites, Cell adhesion molecules (CAMs), Cell recognition

Question 24

Membrane Carbohydrates

Answer 24

• glycolysis of Erythrocytic membrane groups plays large part in determining blood groups

Question 25

Cell-Cell Adhesions: 3 means

Answer 25

Extracellular Matrix: biological “glue”, has numerous protein fibers within matrix
o Collagen - multiple forms of connective protein
o Elastin - thin, shimmery membrane
o Fibronectin
Cell adhesion molecules in plasma membranes
 Specialized cell junctions
o Desmosomes
o Tight Junctions
o Gap Junctions

Question 26

Desmosomes
 Made of keratin intermediate filaments which are very flexible and stretchy in the extracellular state (over the intracellular state)

Answer 26

 Anchors close, non-touching cells in stretchy tissues

Question 27

Tight Junctions

Answer 27

 Used to separate compartments
 Prevent movement of substances between cells by firmly bonding cells together
 This forces substances through the cells, which is more selective
 Esp. important in digestive tract

Question 28

Gap Junctions

Answer 28

 Small connecting tunnels made of connexon proteins
 Very common in cardiac and smooth muscle (large groups of highly excitable cells)
 Allows free passage of very small ions and/or membrane potentials to pass between cells w/o an action potential
 Each cell assembles half of a channel

Question 29

Membrane Transport

 Membrane is selectively permeable

Answer 29

Both particle size and particle solubility in lipids influence whether they can permeate cell membrane w/o assistance

Question 30

Unassisted Membrane Transport

o Diffusion

Answer 30

 Uniform spreading out of molecules
 Dependent on Brownian motion and conc. gradients
 Critical for muscle contractions, nervous signaling, exchange of O2 and CO2, and movement of substances across kidney tubules

Question 31

Fick’s Law of Diffusion:
 > conc. grad. inc. diff.
 ECF is large, so conc. changes very slowly
 Substances move freely between blood and ECF, but not ECF and ICF

Answer 31

 > permeability inc. diff.
 > S.A. inc. diff.
 > Mol. Weight dec. diff.
 > distance of diff. dec. diff.

Question 32

Osmosis: Net diffusion of water down its conc. gradient
 Hydrostatic pressure ??
 Tonicity: ??

Answer 32

• prevents infinite movement to side with higher conc. gradient
• osmolarity of solution in comparison to the cell

Question 33

Tonicity

Answer 33

Tonicity: osmolarity of solution in comparison to the cell
 Isotonic solution: Cell stays the same size
 Hypotonic solution: cell will swell (> water conc.)
 Hypertonic solution: cell will shrink (< water conc.)
 This generally initiates apoptosis