Chapter 4 Flashcards
(105 cards)
1
Q
Define diffusion
A
Movement of particles from one location to another
2
Q
Define flux
A
Amount of material crossing a surface in a unit of time
3
Q
Net flux is greater on the side of the membrane
A
with higher concentration of solute
4
Q
4 factors that influence net flux magnitude
A
Temperature, surface area, mass of molecule, medium
5
Q
Define simple diffusion
A
Movement of solutes from one location to another due to their random thermal motion
6
Q
Simple diffusion occurs through a medium such as
A
Air, water
7
Q
Diffusion equilibrium means
A
Over time, solute will become evenly distributed
8
Q
At diffusion equilibrium, net flux equals
A
Zero
9
Q
For diffusion through the lipid bilayer, the hydrophobic interior
A
Limits diffusion rate
10
Q
Diffusion through the lipid bilayer means
A
Passing through the membrane without any channels
11
Q
Lipid soluble molecules diffuse through lipid bilayer
A
Rapidly and readily
12
Q
Examples of molecules that diffuse readily
A
O2, CO2, N2, urea, fatty acids, steroids, alcohol
13
Q
Polar and large molecules diffuse
A
Slowly and can be retained within the cell
14
Q
Rate of movement depends upon
A
Permeability coefficients
15
Q
Membranes effect on the rate of diffusion
A
1K to 1 M times slower than through the same layer of water
16
Q
Ions that diffuse through channels
A
Na+, K+, Cl-, Ca2+
17
Q
Exocrine glands release secretions into
A
Ducts
18
Q
endocrine glands release secretions into
A
Blood capillaries into ISF
19
Q
Merocrine, apocrine, and holocrine secretions are types of
A
Exocytosis via exocrine glands
20
Q
Glands are
A
Groups of secretion-forming cells actively engaged in trans cellular movement of materials
21
Q
Holocrine secretion
A
Entire cell becomes secretion (sebaceous glands) ex egg release
22
Q
Merocrine secretion
A
Secretion released from vesicles (salivary glands)
23
Q
Apocrine Secretion
A
Tip of cell becomes secretion
In groin/inguinal regions, not active until puberty
24
Q
Apical
A
Luminal
25
Basolateral
Serosal
26
Basolateral membrane is near ____ and rests upon ____
Blood vessel network, basement membrane
27
Epithelial paracellular transport is limited by
Tight junctions, narrow passageway, and permeability varies
28
In Athsma and allergies
Damage to junctions and epithelial barrier allows pathogens access to restricted areas, sets off toxic cascade
29
Epithelial paracellular transport
Diffusion of substances between adjacent epithelial cells
30
Epithelial trans cellular transport
Substances move through apical or basal surface of cell, through cytosol, and exit on opposite surface
31
Opposite surfaces of epithelial cells have
Different concentration gradients
32
Na+ transport
Epithelial transcellular: active transport via Na+/K- ATPase pump on basal surface
Passive diffusion into cell on apical surface
33
Transepithelial osmosis
Movement of water can occur via osmosis as a result of solute concentration changes
34
When possible, water follows ___ which can cause _________________
Na+, large shifts of water in fluid compartments
35
Transcellular pathway of water diffusion
Aquaporins in the membrane
36
Paracellular pathway of water diffusion
Tight junctions between epithelial cells
37
Ion channels are
Integral membrane proteins (span membrane, simple donut ring or more complex structure)
38
Specificity is determined by
Pore size of the channel (small diameter blocks large molecules), charge (charged and polar surfaces of channel walls), and binding sites (# H2O molecules associated with diffusing ion)
39
Diffusion time increases in proportion to
Distance squared (D^2) that molecules diffuse
40
Diffusion is limited by
Distance
41
If a substance has to diffuse a long distance
It is very slow. Ineffective way to move solutes
42
Pneumonia
Lung inflammation/swelling means takes longer for gas to diffuse between alveolus and capillary
43
All cells have
Membrane potential/polarity difference
44
Membrane potential is
Separation of electrical charges across membrane of all cells
+ external
- internal
Tends to drive + in cell and - out of cell
45
Ionic movement (influx/efflux) is influenced by
Membrane potential and total concentration of charges (electrochemical gradient)
46
Diffusion or movement of charges is a voltage (or EMF) measure in mV using
The Nernst Equation
47
How is movement of ions across the PM regulated
Channel gating
48
Conformational change via
Ligand voltage or mechanically regulated ion gates
49
Permeability of the membrane directly related to
# channels available per unit area membrane
Temperature
50
Permeability of the membrane inversely related to
resistance of each channel
Mass of diffusing substance
51
Increase in surface area means
Increase in diffusional rate and flux
52
Passive transport
Particles diffuse from high to low concentration
53
Net rate of diffusion proportional to
ECF concentration (Co) +/- ICF (Ci)
54
Fick’s diffusion equation
F(J) = PA (Co +/- Ci)
F(J) = net flux
P = diffusion coefficient of substance moving through membrane
A = area
Co= ECF concentration
Ci = ICF
55
Electrical potential difference
Electrical charge difference between ECF and ICF
56
Mediated-transporter systems are mechanisms for
Solutes that are too large, too charged, or both (glucose)
57
Protein transporters/carriers may be
Passive or active
58
Tmax
Maximum flux, transporters saturated
59
Transporters participate in
Facilitated diffusion, primary and secondary active
60
Magnitude of flux determined by
Solute concentration
Affinity of transporter for solute
#transporters available
Rate of conformational change
61
Affinity increased by
Increased specificity and increased electrical attraction
62
Describe carrier mediated / facilitated diffusion
Ligand specific protein escorts substance through membrane
Substance binds to channel protein, conformation change
63
Sweet smelling urine in diabetes because
Glucose exceeds Tmax, no more transport proteins available, excess glucose in blood stream and not enough in cells
64
Simple diffusion flux determined by
Concentration gradient
65
Facilitated diffusion maximal flux determined by
# available transporters
66
GLUTs (glucose transporter proteins) function
Uptake of insulin into insulin dependent tissues such as skeletal and cardiac muscle and adipose tissue
67
GLUT1
Insulin independent
68
GLUT4
Insulin dependent
69
Secondary active transport indirectly uses ATP by
Using the energy created from an ion (electrochemical) gradient established by pumps
70
Transporters are ATPases that
Break down ATP, self-phosphorylate, enable binding of solute
71
Sodium pump is catalyzed by
Na+/K-ATPase
72
Na/K pump moves
3 Na out
2 K in
73
Movement of ions through pump fueled by
Hydrolysis of ATP
74
Ca2+ ATPase function
Removes cytosolic calcium to maintain low intracellular Ca vs high Ca in ECF
75
Ca homeostasis important to
Neurotransmitter release, skeletal muscle
76
Secondary transporters have
Two or more binding sites
77
Na concentrations extra and intra cellular
145 mM extra, 15 mM intra
78
K concentrations
5 mM extra, 150 mM intra
79
Osmosis driven by
Change in solute concentration on one side of membrane
80
Where solute concentration is greatest, water concentration is
Less
81
Addition of solute molecules to pure water
Lowers water concentration in solution
82
Osmolarity
Total concentration of a solution
83
Higher osmolarity
Lower water concentration
84
Water moves into area with
Highest osmolarity / least number of water molecules
85
Serum osmolarity
300 +/- 10 mOsm/L
86
Osmolarity directly related to
Osmotic pressure
^ osmolarity ^ osmotic pressure ^ rate of osmosis
87
Volume at equilibrium
Veq = Vor (Osm or / Osm eq)
88
Tonicity refers to
Concentration of non penetrating solutes that must be assisted across the PM (trapped in ECF) such as Na and Cl
89
Ionic composition of ICF and ECF
Na ECF 134-136 mmol/L
ICF 20 mmol/L
+53 mV
K ECF 3.8-5.4 mmol/L
ICF 150 mmol/L
-97 mV
90
What determines movement of water across a cell membrane
Tonicity
91
Isotonic
#nonpen solutes in ECF = ICF
300 mOsm/L nonpen
92
Hypotonic
Water influx into cell (cell expands)
Less nonpen solutes in ECF than ICF
<300 mOsm/L nonpen
93
Hypertonic
water efflux out of cell (cell shrinks)
More nonpen solutes in ECF than ICF
>300 mOsm/L nonpen
94
Osmolarity measures
Total solutes present (both pen and nonpen)
95
Isosmotic
300 mOsm/L solute
96
Hyperosmotic
>300 mOsm/L
97
Hypoosmostic
<300 mOsm/L
98
Blood volume restored by
Infusing isotonic NaCl
More effective than isosmotic soln of pen solute bc would only partially restore blood volume as some solute enters cells so would water, increasing ICF of TBW
99
Endocytosis ____ PM
Exocytosis ____ PM
Endocytosis removes PM
Exocytosis replenishes PM
100
Endocytosis
Mvmt of molecules into cell via vesicles
101
Pinocytosis
Fluid Endocytosis
PM invaginates and captures water + nonspecific dissolved substances into a vesicle
102
Phagocytosis
Immune cell mediated specific Endocytosis where particles are engulfed by pseudopodia (cytoplasmic projections) with formation of phagosomes that fuse with lysosomes for enzymatic destruction
103
Receptor mediated Endocytosis
Most specific mechanism
Ligands bind to membrane receptors at clathrin coated pits
Invaginates forming clathrin coated vesicles that move intracellularly
Ex. Cholesterol is removed from blood stream
104
Potocytosis
Less specific than receptor-mediated
Modified Endocytosis
No fusing with lysosomes
No clathrin
Form caveolus
105
Exocytosis
Replenishes membrane
Mechanism to secrete large substances from cell
Usually triggered due to calcium influx
