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Cell Bio > Cell membranes > Flashcards

Cell membranes Flashcards

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Biology 101 flashcards
1
Q

Functions of cell membranes

A 
Barriers
Transport 
Receptors
Adhesion: cells joined into tissues, cells interacting with different types of cells
Movement
Localization of functions of organelles
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2
Q

Fluid mosaic model

A

Eukaryotic cells: 40% lipid, 50% protein, 10% carbohydrates

Bacterial cells: more proteins-greater ability for transportation

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3
Q

Amphipathic molecule

A

Having both polar and non-polar portions

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4
Q

Bilayer formation

A

Hydrophilic heads want to be near water and each other

Hydrophobic tails want to be away from water

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5
Q

Liposome

A

Sealed compartment formed by phospholipid bilayer

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6
Q

Movement of phospholipids in membrane

A

Lateral diffusion (movement right and left)
Flexion of tails
Rotation of phospholipid
Flip-flop (rarely occurs)

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7
Q

Phospholipids

A

Phosphoglycerides: glycol base
Phosphatidyl choline: most common phospholipid
Phosphatidylserine

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8
Q

Glycolipids

A

Lipids with sugar attached
No phosphate: sugar instead
Sugar is polar

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9
Q

Sterol

A

Ring structure: hydrophilic and hydrophobic sections
Fills in gaps in membrane: makes less fluid
-OH groups
Cholesterol: animals
Phytosterol: plants
Hopanoid: prokaryotes

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10
Q

Fatty acid chains

A

Length of chain is variable (typical: 18-20 hydrocarbons)
Number of saturations is variable (usually 1 or 2 double bonds)
Increase in double bonds: increase in fluidity
Decrease in chain length: decrease in melting point

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11
Q

Asymmetry of plasma membrane

A

Cell positions different molecules on different sides of membrane

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12
Q

Flipase

A

Enzyme that transfers phospholipid from cytosolic face of membrane to the other side
Lipids made on ER

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13
Q

Homeoviscous adaptation

A

Alteration of lipid composition to alter membrane fluidity
Some organisms can shorten chain length or add double bonds in response to cooling
Organisms who do so: bacteria, poikilotherms (organisms whose internal temps vary greatly)

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14
Q

Lipid rafts

A

Membrane regions with more sterols and longer chain length (more saturation)
Less fluidity
Involved in:
Detection of signals and response (ex- T-cell signals in immunity)
Entry sites of pathogens

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15
Q

Types of proteins in plasma membrane

A

Transporters (in: sugars, ions, water, peptides; out: waste, manufactured products)
Anchors
Receptors
Enzymes

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16
Q

Protein connection to plasma membrane

A

Transmembrane: all the way through membrane, alpha helices, 23-30 amino acids to span membrane
Membrane-associated: top part non-polar, bottom part polar
Lipid-linked
Protein-attached: quaternary structure (2 proteins attached), bonds (H-bonds, disulfide, non-polar, etc.)

17
Q

Transmembrane proteins

A

Alpha helices and beta barrels: H-bonding covers up polar parts, exposed R-groups are non-polar
Beta barrel: found in outer membranes of mitochondria and bacteria

18
Q

Glycosylation

A

Covalent addition of sugars to proteins outside of plasma membrane
Typically mannose, sialic acid, or galactose
Varies in terms of which sugars, number of sugars, and linkage of sugars

19
Q

Glycoprotein

A

Protein with a few sugars covalently bonded to it

20
Q

Proteoglycan

A

Protein with long sugar chains covalently bonded to it

21
Q

N-linked glycosylation

A

Carbohydrate group linked to amino group of asparagine

22
Q

O-linked glycosylation

A

Carbohydrate group linked to hydroxyl group of serine or threonine

23
Q

Roles of glycoproteins

A

Recognition by other cells (bind to protein that recognizes)
Hydration: sugars are polar- attract water
Tissue formation: getting like cells to associate
Recognition by pathogens

24
Q

Glycocalyx

A

Glycoproteins on outside of epithelial cells

Purpose: water absorption, protection, identification

25
Q

Determine fluidity of proteins in membrane

A

Label membrane proteins (fluorescence, etc.)
Fuse cell with labeled proteins with cell with differently labeled proteins
Track movement of proteins using microscopy

26
Q

Cortex

A

Protein structure
Location of anchorage of other proteins
Spectrin: linking protein

27
Q

Detergents

A

Remove lipids from proteins: non-polar parts compete with lipids
Sodium dodecyl sulfate (SDS): give proteins negative charge
Triton X-100

28
Q

Detergent mechanism

A

Membrane protein in lipid bilayer + detergent micelles -> water-soluble complexes of transmembrane proteins and detergent molecules + water-soluble mixed lipid-detergent micelles

Cell Bio (15 decks)

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