Chapter 5 Flashcards
(93 cards)
1
Q
What are artificial membranes?
A
Artificial membranes are a simple mixture of amphipathic lipid molecules that form structures to minimize potential energy
2
Q
What are the two types of amphipathic molecules?
A
Hydrophobic & Hydrophilic
3
Q
Hydrophobic
A
- Will not try to interact with the water
- Non polar parts
4
Q
Hydrophilic
A
- Will interact with the water
- Polar parts
5
Q
What are the 3 types of membranes?
A
1) Micelle = soap, single phospholipid layer
- Sphere
2) Liposome = Fat molecule, phospholipid bilayer
- Sphere with halo middle
3) Phospholipid bilayer
- Straight line with tails facing in
6
Q
What are membranes?
A
In reality they are much more complex, and contain many different types of molecules
7
Q
What did we use to think about membranes? What was in conflict of this theory?
A
- That they were made of proteins (supported by TEM photographs)
- The mathematical calculations of the relative lipid and protein contents of the red blood cells were in conflict
8
Q
Using geometric formulae, what were we able to conclude about the original theory of membranes?
A
The surface area of a red blood cell was too great to be covered by the amount of protein that it contains
9
Q
What did researchers do to look at the membranes in great detail? Explain it
A
They developed a TEM technique called Freeze Fracture
- Cells were frozen in liquid nitrogen (-196 degrees) then ‘cracked’ with a knife blade
10
Q
In the Freeze Fracture experiments, where were the cells split open?
A
Split along the weakest point which is often between the layers of the membranes
11
Q
What did the researches of the Freeze Fracture experiment observe?
A
There were dark spots in the membranes and they realized they were proteins in the lipid matrix
12
Q
- Freeze fractured ________________
- White dots are what?
- How can we find out how big proteins and protein complexes are?
A
- Freeze fractured thylakoid membranes
- White dots are protein complexes that are embedded in the membrane
- By using the Freeze Fracture experiment
13
Q
What is the Fluid Mosaic Model
A
It is a model that describes the structural features of biological membranes
14
Q
Fluid Mosaic Model:
The membranes behave like a gel or a solid
A
A gel membrane, not a solid membrane
15
Q
Fluid Mosaic Model:
What does the fluidity do?
A
It keeps the membranes intact and functioning, and allows the cells to change shape.
- The proteins move around
16
Q
Could transport vesicles form without a flexible membrane system?
A
No, need a gel membrane
17
Q
How is the fluidity of a membrane altered?
A
It is altered by lipid type and length, and also by other components such as cholesterol
18
Q
Phospholipid bilayer of a solid is _____ with _________ hydrocarbon tails
A
Phospholipid bilayer of a solid is viscous with saturated hydrocarbon tails
19
Q
Phospholipid bilayer of a liquid is ______ with _________ hydrocarbon tails
A
Phospholipid bilayer of a liquid is fluid with unsaturated hydrocarbon tails with kinks
20
Q
Longer lipids give the _____________ more interactions and will make the membrane more/less _________
A
Longer lipids give the nonpolar tails (hydrophobic) more interactions and will make the membrane more viscous
21
Q
More _________ in the fatty acids will introduce ______ order, and make the membranes more/less ______
A
More double bonds in the fatty acids will introduce less order, and make the membranes more fluid
22
Q
Organisms living in cold areas will have more ______________ and ______________ in their membranes
A
Organisms living in cold areas will have more unsaturated fatty acids and shorter fatty acids in their membranes
23
Q
What are the two layers of a phospholipid bilayer? Are they symmetrical?
A
NOT SYMETRICAL!!!
1) Extracellular leaflet
2) Cytosolic leaflet
24
Q
What are membranes made up of?
A
A phospholipids, glycoproteins, glycolipids, and proteins
25
In which dimension do lipids move in the membrane?
They move in lateral & rotational movement
| - Random movement of lipids
26
How can the lipids inside the cell be transported to the outer leaf of the plasma membrane?
Lipids move across the membrane using a transport protein called Flippase
-It turns ATP into ADP +Pi
27
Proteins in the membrane:
| ______ or ________ proteins cross the membrane and are embedded in the lipid bilayer
Intrinsic Proteins or Transmembrane proteins cross the membrane and are embedded in the lipid bilayer
28
What are the functions of transmembrane proteins in the plasma membrane?
1) They can aid transport of ions & polar molecules
2) They can help communicate signals (nerurotransmitter) from one side to the other (Signal transduction)
3) Enzymatic activity
4) Attachment/ recognition
29
Proteins in the membrane:
| ______ proteins are more loosely associated with the membrane
Extrinsic proteins
30
Where are the extrinsic proteins attached?
They can be attached to transmembrane proteins or with the lipids on one side of the membrane
31
Can membrane proteins move? At what speed and why? What is in their way?
Membrane proteins can also move, but much more slowly due to their size.
- There are many small lipids in their way
32
What else is located in the membrane? Animal and plant membranes
- Animal cells: Cholesterol
| - Plant membranes: Other steroids
33
What is the role of the Cholesterol and Steroids in the membranes?
They fill spaces between the fatty acid tails, and help regulate the fluidity of the membrane
34
What is located in the Extracellular matrix? In the Cytosol?
Extracellular matrix = Fiber
| Cytosol = Linker protein
35
Some membranes proteins are ________ as part of the cytoskeleton or extracellular matrix
Fixed in place
36
What was the Frye and Edidin Cell Fusion Experiment? 1970s
1) They added agents that caused a mouse and human cell to fuse
2) Temp= 0C; added a fluorescently labelled antibody to the mouse (H-2) protein -the proteins were unable to move laterally = remained on one side of the cell
3) Temp = 37C then cool to 0C; added a fluorescently labelled antibody to the mouse (H-2) protein - with a fluorescence microscope seen the proteins mixed due to the lateral movement at 37C
37
__________ are proteins produced by the immune system that recognize specific ______ structures called _________
Antibodies are proteins produced by the immune system that recognize specific 'foreign' structures called antigens
38
Where do the antigens bind?
They bind at specific antigen-binding sites on the antibody
39
For research purposes, what can antibodies be used for?
Antibodies can be raised against specific proteins and isolated for specificity
40
What is the optimal temperature for lipid dispersion? What happens if the temperature is too high?
```
#7 degrees C
Too high of a temperature will cause the proteins to unfold (dissolve)
```
41
What does the FRAP experiment utilize?
FRAP can utilize Green Fluorescent Proteins (GFP) fusions
42
What are the 3 steps to FRAP?
1) Add fluorescent molecule, which labels cell surface membrane proteins
2) Expose cell to laser beam, which bleaches a small region on the cell surface
3) Incubate at 37 degrees. Due to lateral movement, bleached and unbleached molecules will intermix with each other
43
Which type of experiment uses living organisms? Which one used not living, but not dead organisms?
FRAP - uses living organisms
| Frye and Edidin - used not living, but not dead organisms
44
Are plasma membranes uniform?
No
45
___________ and ___________ are important for cellular interactions and shape
Micro-domains and lipid rafts are important for cellular interactions and shape
46
__________ also allow membrane curvature like that we see in ___________ and __________
Micro-domains also allow membrane curvature like that we see in chloroplasts and mitochondria
47
Membrane Curvature:
| What are the 3 parts?
- Cylinder = equal head group & tail cross-sectional areas
- Inverted cone = larger head group than tail cross sectional area (+ curvature)
- Cone = larger tail than head group cross-sectional area (- curvature) (Cholesterol)
48
Plasma membrane
The structure of the plasma membrane gives it semi-permeable properties (Selective barrier)
49
What can pass through the plasma membrane?
- Nonpolar molecules (O2, CO2, N2)
| - Small, uncharged polar molecules (H2O, indole, glycerol)
50
What is excluded by the plasma membrane?
- Large, uncharged polar molecules (Glucose, Sucrose)
| - Ions = charged atoms or molecules ( Cl-, K+, Na+)
51
Chemical Potential
When molecules on one side of the membrane try to move apart
- it is a form of potential energy
- Low entropy
52
Electro-chemical Potential
When the molecules on one side of the membrane are ions
- Their charge forces them apart
- Entropy is even lower
53
Passive Diffusion
The movement of a solute down a gradient.
- does NOT need a transport protein to cross the membrane
- Random movement of molecules to where there are less molecules
54
Facilitated Diffusion
The movements down a gradient with the aid of a transport protein
- Random movement of molecules
- Pass through where protein pores exist
55
Channel proteins
Channel proteins form openings in the plasma membrane but are specific for what they transport
56
Complex (gated) Channel proteins
Complex Channel proteins are regulated so that they only open at specific times
57
Nerve impulses work because of which type of channel proteins?
Complex (gated) Channel proteins
58
What does the channel protein (aquaporin) do?
Transports H2O molecules from outside the cell, through a channel protein (Aquaporin), into the cytosol
59
What does the channel protein (K+ voltage-gated channel) do?
- With normal voltage across the membrane, the activation gate of the K+ channel is closed and K+ cannot move across the membrane.
- When the voltage changes, the activation gate of the K+ channel opens, and moves with its concentration gradient from the cytoplasm to outside the cell.
60
What are the 4 steps of the carrier protein process?
1) Carrier protein is in conformation so that binding site is exposed toward region of higher concentration
2) Solute molecule binds to carrier protein
3) In response to binding, carrier protein changes conformation so that binding site is exposed to region of lower concentration
4) Transported solute is released and carrier protein returns to conformation in step 1
61
What forces the protein to move this way?
The potential energy of the chemical potential forces the protein to move this way
62
What happens if the cell is 2M sucrose solution...
1) The solution is distilled water?
2) The solution is 10M sucrose?
3) The solution is 2M sucrose solution?
1) Water is hypotonic so the water will move into the cell (cell swells)
2) 10M sucrose is Hypertonic to the 2M sucrose will out of the cell, into the surrounding (cell shrinks)
3) Isotonic conditions; equal movement into and out of the cell
63
Cells normally have more solutes __________, therefore water will move ____ the cell
Cells normally have more solutes inside than out, therefore water will move into the cell
64
What prevents a plant cell from exploding due to solute changes?
The cell wall
65
Hypotonic solution
Solute concentration is lower outside the cell
| - water enters cell
66
Hypertonic solution
Solute concentration is higher outside the cell
| - Volume inside the plasma membrane shrinks, and the membrane pulls away from the cell wall
67
What did experiments demonstrate about the movement of water across cell membranes?
That water could not diffuse across membranes at the speeds cells were shown to expand or contract
68
What are the fastest water transporters?
Red blood cells & Kidney cells
69
Which type of water transport protein was found in Red blood cells & Kidney cells?
A protein called CHIP28
70
What was done to determine if CHIP28 was really a water transport protein?
1) The gene for CHIP28 was cloned and mRNA encoding the gene was made in vitro (with RNA polymerase enzyme and nucleotides)
71
What was another way to determine if CHIP28 was really a water transport protein?
2) The CHIP28 mRNA was injected into Frog eggs, where it was translated in vivo (use the whole organism), and inserted into the plasma membrane of the egg (oocytes)
72
What was the 3rd thing done to determine if CHIP28 was really a water transport protein?
3) Place the egg (oocytes) into a hypotonic medium and observe under a light microscope. If the egg with CHIP28 changes size fater then it could be concluded that it transports water molecules
73
Does CHIP28 make the cell more sensitive to rapid water transport?
Yes
74
What was CHIP28 renamed to?
Aquaporin
75
Aquaporin
Allows the facilitated diffusion of water molecules across the membrane
- They move in a single file through the channel
76
Pic with channel and aquaporin:
| Does the protein structure match the protein function?
Yes
77
Who discovered Aquaporins?
Peter Agre - won 1/2 noble prize in 2003
78
What are the 3 classes of transporters?
Simple Uniporters, Symporters, and Antiporters
79
Uniporters
Uniporters bind a single solute on one side of the membrane, and move them to the other (in one direction)
80
Symporters
Symporters bind two solutes and move them both across the membrane in the same direction
- used for active transport
- A driving ion in high concentration & A Transported solute in low concentration
81
Active transport
Active transport moves solutes from low to high concentrations (against its concentration gradient)
- This takes energy because due to random movement, solutes do NOT like to be concentrated
82
Antiporters
Antiporters bind two solutes but move them in opposite directions across the membrane
- used for active transport
- Driving ion in high concentration & A Transported solute in low concentration
83
What type of Transport is crucial to living cells to accumulate nutrients and essential factors?
Active Transport
84
What happens when Ca2+ ions are pumped against the concentration gradient?
A Ca2+ pump uses ATP to transport Ca2+ from the cytosol to the ER Lumen, against the gradient
-
85
When Ca2+ ions are pumped against the concentration gradient, what is ATP used for?
ATP is used and an energy source to change the shape of the transporter protein
- ATP is like loading a spring
86
In a Primary Active Transport, how is the solute moved?
The solute is moved using energy from ATP
- Uniporter (moves 1 thing at a time)
- against a gradient
87
What does a Secondary Active Transport use to transport?
It uses the energy available due to a second, favourable concentration gradient
88
How does the Secondary Active Transport work with the H+ ions/ sucrose symporter?
The H+ ions force a change in the protein shape which moves the sucrose molecules
- against a concentration gradient into the cell
89
Active transport by the Na+/K+ - ATPase
Active transport keeps _____ cells ready to transmit information by pumping more _____ out, than ___ in, the outside of the cell becomes more _______ charged.
____________ gradient forms
What type of enzyme is used?
Active transport keeps nerve cells ready to transmit information by pumping more Na+ out, than K+ in, the outside of the cell becomes more positively charged.
An electrochemical gradient forms
ATPase
90
What is the 4 step process that uses ATP and pumps both Na+ and K+ across the membrane?
1) 3Na+ bind from cytosol. ATP is hydrolyzed. ADP is release and Pi covalently attached to the pump switching it to the E2 conformation
2) 3Na+ are released outside the cell
3) 2K+ bind from outside of the cell
4) Phosphate is released and the pump switches to the E1 conformation. 2K+ are released into the cytosol. Then the process repeats
91
Nerve impulses travel along the _____ by _________
Nerve impulses travel along the Axon by depolarization
92
Myelinated neuron:
| A single ____ cell wraps itself around an axon to form a segment of the ________
glial cell
| Myelin sheath
93
During a nerve impulse, channels open allowing ____ to re-enter the cell by _______. This collapses the _____________, which must be re-established by ___________________
During a nerve impulse, channels open allowing Na+ to re-enter the cell by diffusion. This collapses the electrochemical gradient, which must be re-established by active transport processes
