Cell Membrane 1 Flashcards
-No biological membranes = ?
-Functions? (3)
-External boundaries? (3)
-Central to both what? (2)
-Can Break and re-seal for ? or ?
-Serve as attachment surface for ?
-No biological membranes = No life!
-Functions:
* movement of material into and out cell.
* electrical signaling between cells.
* defines the boundaries of organelles & separates complex chemical reactions.
-External boundaries:
flexible for growth and movement, self-sealing and selectively permeable to polar solutes.
-Are central to both biological energy conservation and cell-to-cell communication.
-Can break and re-seal for fusion or fission.
-Serve as attachment surface for cytoskeleton
-Cellular compartmentalization:
Functional ? within the cell
-Examples? (6)
-Cellular compartmentalization:
Functional separation within the cell.
-EX: Plasma membrane, Nuclear membrane (inner and outer), ER membrane, Golgi apparatus, Mitochondrial membrane (inner and outer), Peroxisomes and Lysosomes-
COMPARTMENILIZATION PT 2
1.Separation of antiparallel processes?
- Separation of similar reactions serving different
purposes?- Coordination of different reactions which are involved in the same pathway (energy efficiency)?
COMPARTMENILIZATION PT 2
1.Separation of antiparallel processes.
* i.e. anabolic and catabolic processes can be held in separated compartments avoiding competition for the substrate or interference in the reactions.
Example: Fatty acid synthesis in cytosol and fatty acid oxidation in mitochondria.
- Separation of similar reactions serving different
purposes.
* i.e. similar reactions for different purposes and must therefore be held in independent compartments.
Example: fatty acid oxidation.
* in mitochondria for energy production * in peroxisomes for heat production.- Coordination of different reactions which are involved in the same pathway (energy efficiency).
Example: TCA and electron transport chain are the central point of energy metabolism in cells and located in the mitochondria.
- Coordination of different reactions which are involved in the same pathway (energy efficiency).
Properties
* ? the cellular interior from the exterior
* ? ? with the ? in a controlled manner
* Membranes are extremely ?
* Membranes get information from the cell about ? ?
* Membranes are ? barriers, allow ? transport of molecules into and out of the cell
* Membranes contain ?, ?, ? and other proteins
- Separates the cellular interior from the exterior
- Exchanges information with the environment in a controlled manner
- Membranes are extremely dynamic
- Membranes get information from the cell about metabolic status* Membranes are selective barriers, allow selective transport of molecules into and out of the cell
- Membranes contain enzymes, transporters, receptors and other proteins
Membrane Fusion:
?????
Membrane Fission:
?????
Membrane Fusion:
-2 separate lipid bilayers merge to become 1.
*Example: Transport vesicles from the ER fusing with
Golgi membranes.
-Membrane Fission:
Involves splitting of a membrane into 2 parts
* Example: formation of vesicles by ER/Golgi apparatus to transport lipids and proteins to other organelles and
to cell membrane.
Cell Membrane Components? (5)
-Lipids - phospholipids, sterol, glycolipids
(about 50% of the mass of most animal cell membranes)
-Proteins (transmembrane, peripheral)
-Carbohydrates (glycan groups)
-Water
-Divalent cations (Ca2+, Mg2+)
Proteins that are ? of or ? with biological membranes
- Most membrane ? are transmembrane and mediate many functions such as ? and ? ? ? (enzymes)
- Some transmembrane proteins serve as ? ? connecting the cytoskeleton through the lipid bilayer to either the ? ? or to an ? cell
- Others serve as ? to detect and transduce signals
Proteins that are part of or interact with biological membranes
- Most membrane proteins are transmembrane and mediate many functions such as transport and catalysis of reactions (enzymes)
- Some transmembrane proteins serve as structural links connecting the cytoskeleton through the lipid bilayer to either the extracellular matrix or to an adjacent cell
- Others serve as receptors to detect and transduce signals
LIPIDS
-Composed of what? (3)
-All lipid molecules in cell membranes are ?
- Three main lipids:
-Phospholipids (phosphoglycerides and sphingolipids)
-Sterols (cholesterol in eukaryotic cells)
-Glycolipids
-All lipid molecules in cell membranes are amphipathic
LIPID BILAYER
-The ? structure results from special properties of ? molecules that cause their spontaneous assemblage into bilayers.
-Common general structure: very ? film of ? and ? molecules, held together mainly by ? interactions
-Fluid, dynamic structures -> ???
-The bilayer structure results from special properties of lipid molecules that cause their spontaneous assemblage into bilayers.
-Common general structure: very thin film of lipid and protein molecules, held together mainly by non covalent interactions.
-Fluid, dynamic structures –> FLUID MOSAIC MODEL
Prokaryotic plasma membrane
-#? main type of ?
-Contain no ?
Eukaryotes Cells
-mixtures of ? ?
-large amounts of ?
Prokaryotic plasma membranes are often composed:
one main type of phospholipid
contain no cholesterol (with some rare exceptions)
Eukaryotes cells
-mixtures of different phospholipids
-large amounts of cholesterol
Lipids spontaneously form ? or ? in an ? environment
* Cone-shaped amphipathic molecules (Fatty Acids) form ?
* Cylinder-shaped molecules form ?
This provides the bilayer‘s ? property
Lipids spontaneously form micelles or bilayers in an aqueous environment
* Cone-shaped amphipathic molecules (Fatty Acids) form micelles,
*Cylinder-shaped molecules (phospholipids) form bilayers
-This provides the bilayer‘s self-healing property: all free edges are avoided by closing in on itself.
- Scanning electron microscope (SEM): ?
- Transmission electron microscope (TEM): ?
- Freeze-fracture and freeze-etch electron microscopy: ?
- Scanning electron microscope (SEM): directly produces an image
of the three-dimensional structure of the surface of a specimen - Transmission electron microscope (TEM): a beam of electrons is transmitted through a specimen to form an image, capturing fine detail
- Freeze-fracture and freeze-etch electron microscopy: provide views of surfaces inside the cell
-? head group and two ? hydrocarbon tails (fatty acids)
-One tail usually contains one or more ?-double bonds
(?), while other does not (?)
-Polar head group and two hydrophobic hydrocarbon tails (fatty acids)
-One tail usually contains one or more cis-double bonds
(unsaturated), while other does not (saturated)
4 MAJOR PHOSPHOLIPIDS PREDOMINATE
1. ?
2. ?
3. ?
4. ?
? carries a net negative charge
-The bilayer is ? with unequal distribution of phospholipids
4 MAJOR PHOSPHOLIPIDS PREDOMINATE
1. Phosphatidylcholine
2. Phosphatidylethanolamine
3. Phosphatidylserine*
4. Sphingomyelin*
- phosphatidylserine carries a net negative charge
-The bilayer is asymmetric with unequal distribution of phospholipids
