Chapter 3 Flashcards
1
Q
what are lipids
A
Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix
poorly, if at all, with water.
2
Q
fatty acids are made of what components?
A
carboxylic acid,
long carbon chain
3
Q
if a fatty acid link a glycerol it forms what molecule
A
triglyceride
4
Q
2 types of fat and what distingues them?
A
saturated
unsaturated
unsaturated has double bonds
5
Q
the main component of phospholipids is
A
fatty acids
6
Q
the double bond has an impact on
A
fluidity of the plasma membrane
7
Q
higher levels of unsaturation leads to
A
lower melting point
less viscous(oil)
8
Q
est-ce que toutes les espèces ont le meme niveau d’insaturation?
A
non, their variations are due to the adaptations to specific environment conditions
9
Q
is it possible to change the lipid composition of the plasma membrane depending on the temperature for some species?
A
yes
10
Q
what is the fundamental role of the membrane?
A
to act as a selective permeable barrier, regulating the cell’s chemical composition
11
Q
what is the main component of the plasma membrane?
A
phospholipids
it is a bilayer of phospholipids
12
Q
what are the roles of the plasma membrane?
A
compartmentalization
site for biochemical activities
providing a selectively permeable barrier
transporting solutes
responding to external stimuli
intercellular interaction
energy transduction
13
Q
phospholipid is made of what
A
lipid made up of glycerol joined to 2 fatty acids and a phosphate groupe and choline
14
Q
which part of phospholipid is hydrophobic and hydrophilic?
A
head-hydrophilic
tail = hydrophobilc
15
Q
if it has parts that are hydrophobic and hydrophilic then it is named as
A
amphipathic
(with both a hydrophilic
region and a hydrophobic region).
16
Q
because of their amphipathic nature, the phospholipids do what when they assemble?
A
this causes phospholipids to assemble
into bilayers, exposing their hydrophilic
(polar) head to the polar water molecules.
17
Q
can polar molecules cross the
bilayers membrane?
A
non
18
Q
what means that amolecule is hydrophobic?
A
it means that it can not interact with water
19
Q
phospholipids can differ based on what?
A
Phospholipids can differ based on the fatty acid chains (length, number and position of double bond),
the fatty acid linkage (ester versus ether)
the head group (Phosphatidyl choline, Phosphatidyl
ethanolamine, Phosphatidyl serine, Phosphatidyl inositol…)
20
Q
if the fluidity is increased for the plasma memebrane
explain the impact on the permeability and protein functions?
A
it increases the membrane permeability and proteins functions
21
Q
name the 3 possible movements of phospholipids?
A
lateral shift
transverse diffusion
flex
22
Q
permeability of the membrane is higher for
A
• smaller molecules • less polar (charged) molecules • more hydrophobic molecules • highly lipid soluble substances • gas (ex: O 2 , CO 2
23
Q
what means when a barrier is efficent?
A
it maintains the concentration of all the molecules inside the cell
24
Q
what are transport proteins?
A
are transmembrane proteins that can modify temporarily the permeability
of the membrane by allowing only specific molecules to cross (enter or leave the cell).
25
explain the fick's law of diffusion
The flux of molecules goes from regions of high concentration to
regions of low concentration
. The magnitude of this diffusion is proportional to the concentration gradient
between the two compartment (ex: across the plasma membrane).
26
the flux of molecules going from high to low concentration is du to
stochastic(random) movement of each molecule in all direction
27
net movement of a population of molecules towards............(
lower concentrations (chemical gradient)
28
if the molecule is polar or charged, its net movement also depends on both
the chemical gradient
and
the electric gradient across the plasma membrane
29
what is an electric gradient?
it is a difference in the charges across the membrane(intern and extern) of the cell
30
passive (simple) diffusion across the phospholipids double layer, requiers energy(hydrolysis of ATP)?
NON
it does not require the energy(hydrolysis of ATP
it is a passive diffusion
31
c'est que les regles à suivre pour savoir quels molecules vont passer par simple diffusion(passive diffusion)
Substances follow their own concentration gradient (from high concentration to low concentration)
Gas follow their own partial pressure gradient (from high partial pressure to low partial pressure) CO2 and O2
At equilibrium there is an equal number of molecules passing in each direction
32
Note that diffusion can be facilitated by membrane transport proteins (channels) that are .............
and give examples
highly selective and
let specific molecules go through
(ex: aquaporins in the kidney ducts)
33
what are aquaporins?
they are proteins that let molecules of water to pass through by simple diffusion(passive)
34
why there are transport proteins that can do passive diffusion?
because there are molecules who have difficulty to pass through the plasma membrane like sucrose, ions(Ca2+)
35
transport proteins are embedded where?
in the plasma membrane
36
The cell is able to modify (regulate) the entry/exit of molecules through…
the expression of genes that code for transport proteins (which are then inserted in the membrane)
•
the temporary opening and closing of some of these transport proteins (depending on a stimulus)
37
by regulating the entry/exit of molecules, the cell can maintain
•
a specific cellular concentration of each solute (ions, molecules)
•
a specific electric potential across the membrane (by keeping some ions outside and others inside)
38
what is the charge inside the cell normally and is due to what?
negative normally
due to the presence of phosphate groups and proteins that are both -ve charged and to the movements of ions in/out of the cell
39
what is a membrane potential?
also called
The charge difference (voltage) across the plasma membrane---. The attraction of opposite charges across the plasma membrane is a
source of potential energy.
electrical potential
40
the resting membrane potential has a value of
70 mV
41
If a molecule is not charged (or large), its diffusion across the membrane
only
depends on
depends on the chemical gradient concentration gradient
42
If a molecule is charged (and small), its diffusion across the membrane
depends on
If a molecule is charged (and small), its diffusion across the membrane
depends on
both
43
if we have to take in account the chemical gradient and electrical gradient then this combination is called
electrochemical gradient
44
Ions are charged and their facilitated diffusion therefore depends on the
electrochemical gradient
45
true or false
Its diffusion does not depend on the concentration gradients of other
true
46
Each ion has its own
| equilibrium potential which is
: the difference in charges across the membrane due to the
| difference in its concentration (so it results from both the chemical and the electrical gradient).
47
what is a non-penetrating molecule?
is a substance that can not cross the membrane because of the selective permeability
48
what is osmosis
it is a net movement of water towards the compartment with higher concentration of non-penetrating solutes across a selectively permeable membrane
49
what is osmolarity
: concentration of all solutes in a solution both penetrating and non penetrating osmole/L)
50
if it has a higher concentration of solutes than the cell (penetrating and non penetrating).
the solution has what type of osmolarity?
hyperosmotic
51
if it has a lower concentration of solutes than the cell (penetrating and non penetrating).
the solution has what type of osmolarity?
hypoosmotic
52
if it has the same concentration of solutes as the cell (penetrating and non penetrating).
the solution has what type of osmolarity?
isoosmotic
53
give the 3 types of osmolarity
hyperosmotic
hypoosmotic
isoosmotic
54
what is tonicity?
: ability of a solution to create a net movement of water inside or outside of a cell. It is calculated as
the concentration of non penetrating solutes only , those that can exert an effective
Tonicity is therefore the effective osmolarity
with
regards to the osmotic pressure and is expressed
as “
effective os mole/L
55
give the 3 types of tonicity
hypertonic
hypotonic
isotonic
56
if a solution has if it has a higher concentration of non penetrating solutes than the cell.
it has what type of tonicity?
hypertonic
57
if a solution has if it has a lower concentration of non penetrating solutes than the cell.
then it has what type of tonicity?
hypotonic
58
if a solution has if it has the same concentration of non penetrating solutes as the cell. it has what kind of tonicity?
isotonic
59
what is osmotic pressure?
is the minimum pressure required so there is no movement of water across a
semi permeable membrane.
```
The
osmotic pressure is a
function of the difference in
the concentration of non
penetrating molecules!Page 33
```
60
the osmolarity depends on what pour avoir lieu?
Osmosis depends on the concentration of non penetrating molecules inside and outside the cell
61
if an ionic compound like NaCl, KCl, HCl dissociate in water , what happens to the osmolarity and tonicity?
Th e osmolarity (and tonicity) of these molecules is therefore
doubled when in solution or inside the cell.
62
Movements of water inside and outside the cell through osmosis
can create an
osmotic pressure and
| change the volume of a cell
63
Higher tonicity inside the
cell..............(decreases/increases)the osmotic
pressure inside the cell
increases
64
what structure helps in plant cells to resist the increased osmotic pressure?
the cell wall
65
what is osmoregulation?
Osmoregulation, the control of solute concentrations and water balance, is a necessary adaptation for life in various environments.
66
what are transport proteins?
are membrane proteins that can modify the permeability of the membrane by allowing
only specific molecules to cross (enter or exit the cell).
67
the regulation of permeability by transport proteins through
… expression of genes that code for or these transport proteins
(which are then inserted in the membrane
… temporary activation/deactivation (opening/closing) of these transport proteins following a stimulus
68
passive transport requiers energy, ATP?
NON
69
types of transport proteins that can do passive diffusion
uniporter
ion channel
carrier
70
explain the uniporter
et comment on peut l'activer?
(transports a single
Activation: ligand (molecule that binds specifically to another), stress (physical deformation), change in voltage
membrane potential ) or always “
71
explain the ion channel?
(simply letting ions pass in either direction
72
what is a carrier and in which transport it is present?
passive transport
(change in shape to let the molecule pass in a either
it is a proteine that has a specific shape to a very specific molecule and it can change its shape to let this molecule to go
through the plasma membrane. it facilitates the diffusion of the molecule through the membrane
73
an example of a carrier in all tissues?
GLUT1
glucose transporter
74
explain the active transport and what it requires energy from what(2)
Membrane protein can transport
molecules against their concentration gradient (from low to high)
This requires energy from either the :
•
The hydrolysis of ATP ( ATPase ) primary active transport
•
The potential energy stored in ionic gradients maintained by the cell secondary active transport
75
These active transport proteins are all
..........
and it does what?
carriers, also called pump
helps maintain specific
intracellular concentration gradients (ex: Na
++, Cl --, K ++, H ++…) by carrying molecules in only one direction
(against their concentration
76
Transport proteins that move a single molecule with active transport are
uniporter
77
how we name the transport protein that can carry 2 or more molecules at a time with active transport?
cotransporter
78
explain how it works for a cotransporter
. One ion provides the energy (down its concentration gradient),
while the other molecule is carried against its concentration gradient.
79
give examples of cotransporter
symporter and antiporter
80
proteins are made of
polumer of amino acids
81
amino acid are bound by what bond
peptide bond between the carboxyl group and an amino group of two amino acids
82
the properties of amino acids are given based on their
their side chain (R)
83
explain the primary structure
: linear sequence of amino acids of a protein.
The order of amino acids is determined by the DNA sequence of the gene
that codes for this protein.
84
The sequence of amino acids is specific to
| ............
the function of the protein, its localization,
| and its interaction with other molecules.
85
explain the secondary structure
and name the types
```
structure of the protein made of
segments that are
coiled or folded
determines the protein’s shape
```
alpha helices
beta pleated sheets
86
the secondary structure results from
```
The secondary structure results from
hydrogen bonds between
the hydrogens and oxygen atoms of the amide groups found along
the backbone (not the amino acid side chains R groups).
```
87
the tertiary structure is a
Three
dimensional shape stabilized by interactions
between side chains (R groups of the amino acids).
88
The tertiary structure is determined (stabilized)by…
```
•
Hydrophobic interaction: hydrophobic (nonpolar) amino acids
cluster together at the core of the protein (away from ambient
water molecules).
•
Covalent bonds (disulfide bridge)
•
van der Waals interactions
•
Hydrogen bonds
•
Ionic bonds
52
```
89
explain the quaternary structure:
Association of two or more polypeptides (in some proteins only)
It is the overall protein structure that results from the aggregation of polypeptide subunits.
Each subunit is coded by a single gene!
90
c'est quoi le classement of membrane protein
integral proteins
peripheral proteins
lipid-anchored proteins
91
explain the integral proteins
: penetrate the hydrophobic core, and are embedded in the membrane. Typically contain
one or more transmembrane helices (e.g. ion channels, transporters, receptors).`
92
explain the peripheral proteins
: sit on the membrane surface. Noncovalently bonded to the polar head groups of the lipid
bilayer and/or to an integral membrane protein (e.g. proteins involved in the membrane sugar, lipid and protein
metabolism: oxidase, oxygenase, lipase…).
93
explain the lipid-anchored proteins
```
covalently
bonded
to a lipid group that resides within
the membrane. The lipid can be
phosphatidylinositol, a fatty acid, or a
glycosylphosphatidylinositol (GPI)
(e.g. hydrolytic enzymes, adhesion
molecule, receptors).
```
94
true or false
Integral can pass multiple times through
the
hydrophobic part of the plasma
membrane
true
95
what is exocytosis
: secretion of molecules outside the cell by the fusion of vesicles with the plasma
96
what is endocytosis?
: cellular uptake of molecules via the formation of vesicles from the plasma
97
There are three types of endocytosis:
```
•
Phagocytosis (“cellular eating”)
•
Pinocytosis (“cellular drinking”)
•
Receptor mediated endocytosis
```
98
Both endocytosis and exocytosis can.............
by doing:
rejuvenate or remodel the plasma membrane continuously:
•
formation of new vesicles (from the Golgi apparatus) that fuse with the membrane (added by exocytosis)
•
recycling of parts of the membrane (removed by endocytosis)
99
what is phagocytosis
: when a cell engulfs a large particle or a small organism e.g. a prey) by
extending pseudopodia around it and packaging it within a membranous sac called a food vacuole.
The particle is then digested after the food vacuole
fuses with a lysosome containing hydrolytic enzymes.
100
what is pinocytosis
A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.
Cell continually “gulps” droplets of extracellular fluid into small vesicles, formed by infoldings of the plasma
membrane. Coat proteins help form those “pits” (coated pits).
101
pinocytosis is specific or non-specific
and why?
phase endocytosis”) is nonspecific:
many substances can be transported inside the cell at the same time
102
what is receptor-mediated endocytosis
specialized type of pinocytosis that enables the cell to acquire bulk
quantities of specific substances.
103
what are the steps of receptor-mediated endocytosis
This is done through membrane proteins that act as receptor exposed to the extracellular fluid:
1.
Specific solute binds to the receptor proteins
2.
These receptors cluster in coated pits which invaginate
3.
The plasma membrane pinches off to form vesicles containing the bound molecules
4.
The substance is liberated from the vesicle inside the cell
5.
The emptied receptors are recycled to the plasma membrane by the same vesicle
