1
Q
2 main compartments of body
A
- anatomical - body cavities
- functional - body fluid compartments
2
Q
3 body cavities
A
- cranial cavity - brain & spinal cord
- thoracic cavity - lungs & heart
- abdominopelvic cavity - GI tract & reprod. organs
3
Q
2 categories of functional (body fluid compartments)
A
- ECF (extracellular fluid) - plasma & interstitial fluid (surrounds most cells)
- Cells (ICF)
4
Q
compartments are seperated by what?
A
membranes
5
Q
original cell membrane theory
A
single layer of lipids
6
Q
membrane consists of ?
A
phospholipid bilayer
7
Q
functions of cell membrane
A
- physical isolate (isolate ICF & ECF)
- regulation of exchange w environ. (movement across membrane)
- communication between cell & its enviro (respond & interact w external environ)
- structural support (proteins in CM)
8
Q
actual composition of CM
A
lipids, proteins & small amount of carbs
- more metabolically active the membrane, the more proteins it contains
9
Q
are all CM created equally?
A
no - ex: RBC membrane (49%) has more protein than myelin membrane around nerve cells (18%)
10
Q
3 types of lipids found in CM
A
- phospholipid - main type of CM
- sphingolipids - larger than phospho.
- cholesterol
11
Q
phospholipid structure
A
- polar head (hydrophilic)
- non polar fatty acid tail (hydrophobic)
- amphipathic
12
Q
phospholipids form/arrange themselves how ?
A
1.bilayer - sheet
2. micelles - droplets (lipid digestion)
3. liposomes - aqueous center
13
Q
phospholipid chemical structure
A
- glycerol backbone
- phosphate polar head
- hydrophobic fatty acid tail
14
Q
sphingolipid structure
A
- lipid rafts (longer than phospho)
- lipid anchor proteins
- sphingosine backbone
- phosphate grp. or sugar (
15
Q
cholesterol functions
A
- increases viscosity of CM - choles. thickens/stiffens CM & makes it flexible r
- decreases permeability
16
Q
current model of CM is known as what
A
fluid mosaic model
- CM is fluid/moveable
- proteins dispersed throughout
- extracell. surface contains glycoproteins & glycolipids
17
Q
CM proteins categories
A
- integral proteins - integrated into CM
- perishable proteins - not integrated into CM (can be chemically removed w/o disrupting CM)
18
Q
each cell has how many diff. types of proteins inserted into the CM
A
10-50 diff. types of proteins in CM
19
Q
integral proteins include:
A
- transmembrane proteins - spans entire protein
- lipid anchored proteins - integrated into lipid (typically into FA tails or linked thru sugar anchor)
20
Q
roles of integral proteins
A
- membrane receptors
- cell adhesion molecules
- transmembrane movement (channels, carriers pores, pumps etc)
- enzymes
- mediators of intracell. signalling
21
Q
peripheral proteins can be attached to
A
- integral proteins
- loosely attached to phospho. head
22
Q
peri. proteins roles
A
- participate in intracell. signalling
- form inner cytoskeleton
23
Q
lipid anchored proteins are associated with what kind of lipid
A
sphingolipid
- attach to FA tails
- high cholesterol content 3-5x
24
Q
lipid anchored proteins can be in what kind of region
A
more viscous regions - higher cholesterol content
25
2 types of lipid rafts
1. planer - lots of integral proteins (channels etc), important for cell signal transduction
2. caveolae - “little caves”, form indentations, important for cell signal transduction also
26
2 categories of CM carbs
1. glycoproteins - protein w carb attached
2. glycolipids - lipid w carb attached
27
functions of 2 diff. CM carbs (glycoprotein & glycolipid)
1. glycoprotein
- form glycocalyx (protective coat)
- cell to cell recognition/interaction
2. glycolipid
- cell to cell recognition/interaction
28
what is considered solvent of life
water
- most important molecule in body (~60% of body)
29
how much of the body’s water is found in cells vs out of cells?
in cells: ICF - 65%
out of cells (ECF): 35% - plasma (25%), interstitial fluid (75%)
30
in general who has more water (males or females)
males
- women have more adipose tissue
31
EC & IC compartments are in a ??
osmotic equilibrium
- fluid concentration is equal: the amount of solute per volume solution
32
osmosis definiton
movement of water across a membrane in response to a solute concentration gradient
33
T/F: water cannot move freely between IC & EC spaces
false
34
what structure allows water to move between IC & EC spaces?
aquaporin channels
- 13 diff. types
- allows for short & longterm water regulation/balance
35
T/F: osmotic equilibrium equals chemical/electrical equilibrium
False: many solutes are ions w/an electrical charge —> electrical disequilibrium
- thus body compartments are in a state of chemical disequilibrium
36
osmotic pressure definition
the pressure that would have to be applied to oppose & prevent osmosis
37
osmolarity describes what
the number of particles in solution
- helps to predict the movement of water by knowing the concentrations of each solution
38
how is osmolarity different from molarity
osmolarity looks at the osmotically active particles vs entire molecules
39
osmolarity formula
molarity (mol/L) x particles/molecules (osmol/mol) {dissociation constant} = osmolarity (osmol/L)
ex: 1M glucose x 1 osmole/mole glucose = 1 OsM glucose
40
what is the normal osmolarity in the human body
280-296 mOsm (milli-osmoles)
41
3 ways to describe osmolarity solutions
1. isosmotic (equal) - solutions have identical osmolarities
2. hyperosmotic (greater than): describes the solution w the hugger osmolarity
3. hyposmotic (less than): describes the solution w the lower osmolarity
42
tonicity describes what
cell volume changes (qualitative description)
43
tonicity definition
describes a solution & how that solution would affect cell volume if a cell were place in that solution & allowed to come to equilibrium
44
3 categories of tonicity
1. hypotonic - cell swells (solution is hypotonic)
2. isotonic - cell stays the same (solution is isotonic)
3. hypertonic - cell shrinks (solution is hypertonic)
45
tonicity vs osmolarity
tonicity: no units, not measurable
- compares a solution & a cell
- tells u ab cell volume in a solution
- depends on the concentration of non-penetrating solutes
osmolarity: has a unit, measurable
- used to compare 2 solutions
- doesn’t tell u ab a cell placed a solution
- depends on the nature of solutes (whether or not they can cross the CM)
46
between the extracellular & intracellular compartments, what is in equilibrium?
fluid concentration
47
T/F: water can move freely between the ECF & ICF
True
48
cell membranes are ____ ______
selectively permeable
49
2 kinds of CM transport
1. passive - no energy needed
2. active - energy needed
50
what crosses the CM is depend on what
1. properties of CM (lipid & protein composition)
2. the substance itself (size & lipid solubility)
51
simple diffusion definition
movement of molecules from an area of higher concentration to an area of lower concentration
52
7 properties/rules of simple diffusion
1. no energy needed
2. high conc. to low conc.
3. continues until equilibrium is reached
4. diffusion occurs faster when
- higher conc. gradients
- over shorter distances
- at higher temp
- smaller molecules
5. in an open system or across a partition that separates 2 diff. systems
6. larger membrane surface area = faster diffusion
7. membrane permeability to a molecule depends on
- the molecule’s lipid solubility
- molecule size
- lipid comp. of the membrane
53
how does membrane size affect simple diffusion
larger surface area of membrane allows for a faster rate of diffusion
54
5 factors that influence simple diffusion across a CM
1. concentration gradient
2. membrane surface area
3. lipid solubility
4. molecular size
5. composition of lipid layer
55
simple diffusion can occur what kind of molecules
small uncharged, lipophilic molecules
- O2, CO2, NH3 etc
- lipids
- steroids
56
ficks law of diffusion
rate of diffusion is proportional to surface area x concentration gradient x membrane permeability
57
membrane permeability equation
membrane permeability = lipid solubility / molecular size
- changing comp. of lipid layer can increase/decrease permeability
58
mediated transport
CM proteins help w the movement of substances
59
2 types of mediated transport
1. facilitated diffusion
2. active transport
60
2 types of membrane transport
1. carrier proteins
2. channel proteins
61
channel protein definition
made of membrane spanning protein subunits that create a cluster w cylinders w a pore in the centre
- named after the substance that passes thru
62
what determines what can pass thru a channel protein
1. size of pore
2. charge within centre of pore (amino acids lining pore determine the charge)
63
2 types of channel proteins
1. open channels “leak channels” - channels are open 24/7 (ex: aquaporins)
2. gated channels - typically closed, gate or ball & chain model
- chemically gated (ligand, confirmation change)
- voltage gated
- mechanically gated (sensitive to CM deformation)
64
channel proteins allow what kinda diffusion
facilitated diffusion
65
carrier protein definition
large complex protein
- change conformation to move molecules
- slow
- 3 kinds
66
types of carrier proteins
1. uniport carriers - only moves 1 kind of substrate
2. cotransporters
- symport (move 2+ substrates in same direction)
- antiport (move substrates in opposite directions)
67
steps of carrier proteins
1. passage open to one side
2. transition state/conformation w both gates open
3. passage open to other side
68
carrier proteins can move what molecules
small organic molecules that can’t move thru channels
69
facilitated diffusion uses ….
channels or carrier proteins
70
facilitated diffusion characteristics
1. move down their conc. gradient
2. no energy needed (passive)
3. stops once equilibrium is reached
71
active transport definition
moving a molecule against its concentration gradient: typically low conc. to high conc.
72
active transport characteristics
- supports a state of disequilibrium (ex: certain ions)
- needs energy (ATP)
- uses carrier proteins
73
2 types of active transport
1. primary active transport - energy to move molecule comes directly from hydrolyzing ATP (ATPase)
2. secondary active transport - uses potential energy stored in conc. gradient of 1 molecule to push another molecule against their conc. gradient
74
primary active transport example
sodium potassium pump (antiport)
- moves Na out of cell & K into cell
- 3 Na out, 2 K in
75
secondary active transport
- can move in the same direction (symport) or opposite (antiport)
76
secondary active transport example
sodium glucose transporter (SGLT)
- Na follows gradient
- Na binds to site, conform change
- High affinity site for Na & Glu
- Na release, conform change
- Low affinity site for Na
- Glucose releases
77
3 properties of both active & passive carrier mediated transport
1. Specificity
2. Competition
3. Saturation
78
Specificity define
the ability of a transporter to move 1 molecule or closely related grp. of molecule
- ex: GLUT transporters moves only naturally occurring 6 carbon sugars
79
competition define
a carrier may move several members of a related grp. of substances but these substances compete w 1 another
80
saturation define
rate of transport reaching a max point
- depends on conc. & # of transporters
- transport normally increases w increasing conc. until transport max. is reached (all transporters are in used)
81
if a channel gate opens in response to the binding of a ligand, it is said to be:
chemically gated
82
vesicular transport definition
using bubble like vesicles to move macromolecules
83
3 kinds of vesicular transport
1. phagocytosis
- vesicles using cytoskeleton (ex: WBC)
- active transport
2. endocytosis
- transport into cell
- membrane indents (smaller vesicles)
- active transport
3. exocytosis
84
endocytosis 2 kinds
1. non-selective
- pinocytosis: allows ECF to enter
2. selective
- receptor mediated transport
85
what is clathrin
“coated pits” - endocytosis
86
what would move through endocytosis
protein hormones
growth factors
antibodies
plasma proteins
- large protein based molecules, lipophobic
87
exocytosis define & characteristics
transport out of the cell
- vesicles filled w large lipophonic molecules or waste left behind by lysosomes
- can occur continuously or intermittently
- needs ATP
- regulated by calcium
88
epithelial transport definition
substances entering or exiting often have to cross a layer of epi. cells (line lumen, surface of organs)
89
absorption
epithelial transport from lumen of an organ to ECF
90
secretion
from ECF to lumen of an organ
91
epithelial transport examples
- digestive tract
- airways
- kidneys
92
3 mechanisms of epithelial transport
1. transcellular: across/through epi. cells - ions
2. paracellular: between tight junctions - ions
3. transcytosis: larger substances (combination of endocytosis, vesicular transport & exocytosis)
93
what 2 membranes must be crossed in transcellular transport
into body:
1. apical membrane
2. basolateral membrane (faces ECF)
94
transporting epithelia polarized
polarized distribution of membrane transporters ensures one-way movement
- typically 1 is active transport & the other is facilitated transport
95
example of transcellular transport
epithelial glucose transport
96
compare epithelial transport energy needs
1. paracellular (no ATP)
2. transcellular (ATP)
3. transcytosis (ATP)
97
major cations & anions in body
cations -
intracellular: K+
extracellular: Na+
anions -
intracell.: phosphate ions, proteins
extracellular: Cl-
98
overall body charge
electrical neutral
- even tho there is still an electrical disequilibrium
99
ECF & ICF charges
ECF = slight excess of cations (+ charge)
ICF = slight excess of anions (- charge)
100
2 factors that influence membrane potential
1. uneven distribution of ion across CM (concentration gradients)
2. membrane permeability to those ions
101
nernst equation describes what
the membrane potential that would result if the membrane were completely permeable to only 1 ion
- equilibrium potential for that ion
102
how to calculate resting membrane potential
GHK equation: predicts membrane potential that results from contribution of all ions that cross the membrane
- takes into account all ions & their permeabilities
103
resting membrane potential in most neurons
70 mV
- mainly due to K+
- Na+ contributes l slightly (v few Na+ leak channels)
- Cl- minimally (since equilibrium potential is close to resting membrane potential)
bmsc 207
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