Plasma Membrane Flashcards
1
Q
Changes in cells micro environments under normal and pathological conditions can cause….
A
The same cell type to have variable features and activities
2
Q
Cells that appear similar in structure often have different families of receptors for signaling molecules such as….
A
Hormones and extra cellular matrix (ECM) components, causing them to behave differently
3
Q
Breast Fibroblasts and uterine muscle cells
A
-Diverse arrays of receptors
-Exceptionally sensitive to female sex hormones
-most other fibroblasts and smooth muscle cells are insensitive
4
Q
Specialized cells: don’t memorize table but…
A
All cells can do all sorts of different basic functions, but some specialize and look different (morphology)
5
Q
Basic structural and functional units of multicellular organisms
A
A. Plasma membrane/ Plasma Lemma/ Cell Membrane
B. Cytoplasm
C. Nucleus
6
Q
Functions of Plasma Membrane (6)
A
- Envelope cell— maintain structure and function
- Act as semipermeable membrane — only allow certain things to pass
- Place for membrane receptors — recognize macromolecules or other cells, or to be recognized by other cells
- Signal transduction into intracellular environment— downstream response within cell (from surface to cytoplasm of nucleus)
- Cell to cell interaction
- Maintain electrical gradient btwn intra & extra cellular — capacitance (difference of charges on inside of cell to outside of cell)
7
Q
Her notes on functions of Plasma Membrane
A
- selective barrier regulating passage of materials in and out
- facilitating transport of specific molecules
- keep constant the ion content of cytoplasm (different than ion content of extra cellular fluid)
- membrane proteins perform recognition and signaling functions (key role in interactions of cell with environment)
8
Q
Plasma membrane components (4)
A
- Phospholipids
- Cholesterol
- Proteins
- Oligosaccharide chains linked (covalently) to phospholipids and proteins
- is a bilayer —> 7.5-10nm thick
9
Q
Phospholipid-bilayer structure
A
Inner layer and outer layer
10
Q
P face
A
Facing cytoplasm —> Inner layer
11
Q
E face
A
Facing extracellular components —> outer layer
12
Q
Parts of phospholipid
A
- Polar, hydrophilic globular head
- nonpolar, hydrophobic long chain fatty acid (LCFA)
13
Q
Saturated fatty acid
A
Straight, no dbl bond
14
Q
Unsaturated fatty acid
A
Bent, has double bond
15
Q
Why polar head on outside?
A
Attracted to water on outside- turns and chains automatically face inside- same with phospholipids on inner layer
16
Q
Why bilayer?
A
Phospholipids are most stable when organized in double layer.
Hydrophobic chains in middle away from water, hydrophilic heads contacting the water.
17
Q
Amphipathic
A
2 parts
1. Hydrophilic polar head that bears a phosphate group
2. Hydrophobic (2 nonpolar LCFA)
18
Q
Phospholipid names
A
Phosphatidylcholine
Sphingomyelin
Phosphatidylserine
Phsohatidylethanolamine
(Found in eukaryotic cells)
19
Q
Fluidity is crucial for
A
Exocytosis
Endocytosis
Membrane trafficking
Membrane biogenesis
20
Q
Fluidity increases when
A
- Increase temp (related to melting points)
- Increase in # of unsaturated bonds of fatty acyl tails
21
Q
Fluidity decreases when
A
decrease in temp
22
Q
Cholesterol location
A
Embedded in LCFA (in between)
23
Q
Role of cholesterol
A
Buffering fluidity of membrane with changes in temp
24
Q
Cholesterol in cold temps
A
Prevents membrane from becoming very ridged— keeps fluid
25
Cholesterol in hot temps
Lowers fluidity so phospholipids don’t arrange too loosely and become too fluid
26
Proteins of plasma membrane
Integral and peripheral
27
Integral proteins
Transmembrane proteins and multi pass proteins
- firmly embedded
- nonpolar AA interact w/ hydrophobic fatty acid chains
28
Transmembrane proteins
Pass all the way through PM from E to P face
29
Multi pass proteins
Passes through membrane multiple times
30
Peripheral proteins
Can be on E or P face, do not go inside membrane
Assists integral proteins
31
Membrane protein movement
Either move laterally or held in place by part of cytoskeleton
32
Oligosaccharide chains
Short chain of saccharides
Attached to phosphohead of proteins and/or lipids
Externally exposed (E Face)
33
Integral protein categories(6)
1. Pumps
2. Channels
3. Receptors
4. Linkers
5. Enzymes
6. Structural proteins
34
Pumps
To transport certain ions (such as Na+, amino acids, sugars)
Ex: sodium/potassium pump
35
Channels
Allowing passive diffusion of small ions, molecules, and water
Ex: aquaporin— channel for water molecules
36
Receptors (receptor proteins)
Allow ligands to bind, such as hormones, antibodies, coated vesicle endocytosis
Bind to ligands/external signals (something that the cell needs to respond to)
37
Linkers (linker proteins)
Anchor intracellular cytoskeleton to extracellular matrix
Keep things in place
Ex: integrin family that links cytoplasmic actin filaments to an extracellular matrix protein (fibronectin)
38
Structural proteins
Form junction w/ neighboring cells
Ex: epithelial cells, role is to create border and hang onto eachother
39
Peripheral proteins info….
- Bound to one of the 2 phospholipid layers (there is more on the P face)
- bind to phospholipid group or integral proteins (non-covalent bond)
Ex: spectrin
40
Spectrin does what?
Stabilizes cell membrane of erythrocytes (RBCs)
41
Spectrin mutations
Hereditary elliptocytes
Hereditary spherocytosis
42
Hereditary elliptocytosis
RBCs misshaped- not biconcave - elliptical shaped
43
Hereditary spherocytosis
RBCs spherically shaped
Lose flexibility
44
Affect of elliptocytosis and spherocytosis
Enlarged spleen
- pain or fullness in left upper abdomen, may spread to left shoulder
- Full w/o eating
- Pressing on stomach
- anemia
- fatigue
- frequent infections
- easy bleeding
45
Glycocalyx
- Saccharides (sugar molecules)
- Branched
- Bind to polar head of phospholipid
** only on E face
On TEM image—> fuzzy layer
46
Glycolipids
Outer layer phospholipids and membrane proteins with Oligosaccharide chains attached
** Oligosaccharide chains constitute the glycocalyx
47
Movement of material across PM, in or out can be done by
Passive transport
Active transport
Vesicular transport
48
Passive transport
No energy required
Move from high to low concentration= down concentration gradient or electrochemical gradient
49
Types of passive transport(2)
1. Simple diffusion
2. Facilitated diffusion
50
Simple diffusion
Small molecules
Diffuse easily
Water goes slowly
Exchange of oxygen and CO2 through the lung blood air barrier
51
Facilitated diffusion
Channel, carrier/pump
Sodium potassium channels —> porins/ multipass proteins, water —> comes in through protein channel called aquaporin
Carrier —> proteins bind to the molecule —> can transport them by undergoing serious of conformational changes, then released on other side
52
Active transport (2)
Energy required (ATP) —> transport molecules against electrochemical gradient via carrier proteins
1. Primary
2. secondary
53
Primary active transport
Using ATP
54
Secondary active transport (2)
Harnessing energy while moving substance up conc gradient while pushing sodium down the gradient
1. Symporter
2. Antiporter
55
Symporter
Moving in same direction
56
Antiporter
Opposite direction
57
Vesicular transport (2)
1. Endocytosis
2. Exocytosis
58
Endocytosis (3)
“ Take something in”
1. Phagocytosis
2. Pinocytosis
3. Receptor mediated Endocytosis
59
Phagocytosis
“Cell eating”
Engulfing something solid such as bacteria or dead cell remnants
60
Cells specialized to do phagocytosis
Blood derived cells such as…
Macrophages and neutrophils
Bacteria bind to surface of neutrophil—> surrounded by extensions of plasma Lemma and cytoplasm —> enclosed bacterium in intracellular vacuole (phagosome) —> merges with lysosome to degrade its components
61
Pinocytosis
“ cell drinking ”
- small invaginations of cell membrane fuse and entrap extracellular fluid and it’s dissolved contents
62
Receptor mediated Endocytosis
Receptors (membrane proteins) aggregate in a membrane region —> invaginates and pinches off —> creates vesicle (endosome)
63
Example of receptor mediated Endocytosis
Developing RBCs in bone marrow
- to synthesize hemoglobin, RBCs need iron (Fe)
- plasma has Fe bound to transferrin (glycoprotein)
- Fe- transferrin is Endocytosed via receptor mediated endocytosis by the developing RBC
- RBC breaks down and extracts Fe from it to use it
64
Exocytosis
“Throw things out!”
Movement of large molecules from inside to outside of cell by vesicular transport
65
Secretory vesicles/ secretory granules
Contains the enzymes accumulated in the apical portion of cells that are ready to be released into the lumen
66
Membrane trafficking
Membrane movement and recycling
- portions of cell membrane become part of endocytotic vesicles or vacuoles during endocytosis
- in exocytosis membrane is returned to cell surface
- endo is on one side of cell, exo on other
- maintains equilibrium
67
Cells involved in endocytosis/ absorption in GI tract
Simple columnar epithelia
- small intestine: absorb nutrients from gut lumen
68
Cells involved in exocytosis/ secretion
Glandular epithelium
- serous
- mucus
69
Optimization of endo and exocytosis
Increasing surface area available
70
Microvilli
- Increase surface area
- “brush border”
- # can change —> if you fast # goes down, when you eat again # goes back up
71
Common glands
1. Serous
2. Mucus
3. Demilune
72
Serous gland
Secreting mainly proteins/ enzymes
73
Mucus gland
Secreting mucous
74
Demilune
Secretes serous and mucus products
75
Why do cells communicate with eachother?
1. Regulate tissue and organ development
2. Control their growth and division
3. Coordinate their functions
76
Types of signaling (5)
1. Endocrine
2. Paracrine
3. Synaptic
4. Autocrine
5. Juxtacrine
77
Endocrine signaling
Signal molecule = hormones—> carried into blood from their sources to target cells through the body
** blood acts as medium
78
Paracrine signaling
- localized
Chemical ligand diffuses into extracellular fluid but is rapidly metabolized so that it’s effect is only local on target cells near it’s source
Cell produce signal—> to other nearby cells
79
Synaptic signaling
Neurons
Neurotransmitters act on adjacent cells through special contact areas call synapses
80
Autocrine signaling
Self signaling
Signals bind receptors on the same cells that produced the messenger molecule
81
Juxtacrine signaling
Two cells signal eachother through direct physical contact
Important in early embryonic tissue interactions
Signaling molecules are cell membrane-bound proteins which bind surface receptors if the target cell when two cells make direct physical contact.
82
Pseudohypothyroidism
Caused by no functioning parathyroid hormone (PTH)
Gland produces PTH but the receptors cannot respond
Short stature, round face, short metacarpals, seizures in childhood, muscle spasms, high phosphate levels in blood, low calcium, fast ossification of bones — less time for bones to grow sufficient (dwarfism)
