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Flashcards in CELL PHYSIOLOGY Deck (128)
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1

Composition of Cell membranes

Phosphlipids and proteins

2

Lipid Bilayer

  • Phopholipids
    • glycerol backbobe (hydrophilic)
    • Fatty acid tails (hydrophobic)

3

Lipid-soluble subtances

can cross the cell membrane

  • O2
  • CO2
  • steroid hormones

4

Water soluble substances

Cannot dissole in the lipid membranes

  • water filled channels
  • pores
  • carriers
  • Na, Cl, glucose, H20

5

Types of Proteins in the Cell membrane

  • Integral proteins
    • anchored, imbedded through  hydrophobic interactions
    • span the cell membrane
    • ion channels, transport proteins, receptors, and GTP binding proteins
  • Peripheral proteins
    • not imbedded
    • not cobalently bound
    • loosely attached via ELECTROSTATIC interactions

6

Intercellular junstions in the Cell Membrane

  • Tight junctions (zonula occludens)
    • between cells (epithelial)
    • intercellular pathway
    • may be permeable (DCT) or impermeable (PCT)
  • Gap junctions
    • permit intercellular communication
    • current flow and elctrical coupling between myocardial cells

7

Characteristics of Different Types of Transport across cell membranes

  • Simple diffusion
  • Facilitated Diffusion
  • Primary active
  • Co transport
  • Countertransport

8

Only form of tansport that is not carrier mdiated

occurs down an electrochemical gradient

does not require metabolic energy and therefore is passive

Simple Diffusion

9

Formula for Diffusion

J = -PA (C1-C2)

  • J = flux (flow) mmol/sec
  • P = permeability (cm/sec)
  • A = Area (cm2)
  • C1= concentration (mmol/L)
  • C2 = concentraition (mmol/L)

10

Describes the ease with which a solute diffuses through a membrane

Depends on the characteristics of the solute and the membrane

Permeability

11

Facors that increases permeablility

  • Increase oil/water coefficient of the solute increases solubility in the lipid of the membrane
  • Decrease radius of the solute increases the diffusion coefficient and speed of diffusion
  • Decrease membrane thickness decreases the diffusion distance

12

Includes facilitated diffusion and primary and secondary active  transport

Carrier mediated transport

13

Characteristics of Carrier mediated transport

  • Stereospecificity
  • Satutration
    • the transport maximum (Tm) is analogous to the the maximum velocity (Vmax) in enzyme kinetics
  • Competition

14

  • Occurs down an electrochemical gradient ("downhill")
  • Does nt require metabolic energy
  • more RAPID than simple diffusion
  • carrier mediated

Facilitated diffusion

15

Occurs against an electrochemical gradient 

requires direct inut of metabolic energy in the form of ATP

carrier mediated

Primary active transport

16

Examples of Primary active transport

  • Na, K, ATPase (or Na-K pump)
    • 3 Na 2 K
    • specific inhibitors:
      • cardiac glycosides
      • ouabain
      • digitalis
  • Ca-ATPase (or calcium pump)
    • Sarcoplasmic and endoplasmic reticulum
    • SERCA
  • H, K ATPase (or proton pump)
    • gastric parietal cells
    • Renal alpha intercalated cells
    • Inhibited by PPI
      • Omeprazole

17

Concentraion of smotically active particles in a solution

Colligative propert that can bemeasured by freezing point depression

 

Osmolarity

18

The transport of two or more solutes is coupled

One of the solutee (usually Na) is transported downhill and provides energy for the uphill tansport

Metabolic energy is provided INDIRECTLY from the sodium gradient

 

Secondary active transport

  • Cotransport/symport = same direction
    • Na-glucose cotransport
    • Na-K-2Cl
  • Countertransport/exchange/antiport = opposite direction
    • Na-Ca exchange
    • Na-H exchange

19

Flow of water across a semipermeable membrane from a solution with low solute concentrationto a solution with high solute concentration

Osmosis 

20

OSmotic pressure can be calculated by __________

states that osmotic pressure depends on the concentration of osmotically active particles.

van't Hoff's law

  • g X C X RT

 

21

The Osmotic Pressure ________ when the solute concentration increses.

Increases

  • The higher the osmotic pressure of a soultion, the greater the water flow into it

22

The osmotic pressure created by proteins

Colloid osmotic pressure or oncotic pressure

23

Number between zero and one that describes the ease with which a solute permeates a membrane

Reflection coeficient

  • if the reflection coefficient is one, the soulte is impermeable. It creates an osmoti prssure
    • albumin
  • If the reflection coefficient is zero, the solutie is completely permeable. therefore it will not exert any osmotic effect
    • urea

24

osmotic pressure (calculated by van't Hoff's law) multiplies by the reflection coefficient

Effective osmotic pressure

25

Integral proteins that span the membrane and, when openm permit the passage of certain ions

Ion channels

26

Characteristics of Ion channels

  • Selective
    • based on the size and the distribution of charges 
  • May be open or closed
  • The conductance of a channel depends on the probability that the channel is open
    • the higher the probability that a channel is open the higher the conductance

27

_______ channels are opened or closed by changes in membrane potntial

Voltage gated channels

28

_____________channels areopened or closed by hormones, second messengersm or neurotransmitters

Ligand gated channels

  • Nicotinic receptors for ACh
    • when open ot is permeable tto Na and K, causeing motor end plates to depolarize

29

the potential difference generated across a membrane because of a concentraion difference of an ion

created by the diffusion of very few ions and therefore, do not result in changes in concentration of the diffusion ions

Diffusion potential

  • Size of the diffusion potential
    • depends on the size of the concentration gradient
    • whether the diffusing ion is positively or negatively charged

30

the potential differencethat woul exactly balance (oppose) the tendency for diffusion down a concentration difference

Equilibrium Potential