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Physio 504 > Lecture 1- Cell Organization > Flashcards

Lecture 1- Cell Organization Flashcards

1
Q

What molecules are selectively permeable to the cell surface membrane?

A

Small molecules

  • ions
  • metabolites
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2
Q

What kind of transport moves molecules against its concentration gradient?

A

Active transport (requires energy)

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3
Q

What is the surface of the cell membrane impermeable to?

A

Large molecules

  • Nucleic acids
  • Proteins
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4
Q

What are the 3 predominant phospholipids that compose the membrane?

A

phosphatidylethanolamine
phosphatidylcholine
phosphatidylserine

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5
Q

Are phospholipids amphipathic or amphoteric?

A

amphipathic

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6
Q

Key points about detergents

A
  • Can dissolve phospholipid membranes because they are amphipathic
  • They are also water soluble at much higher concentrations than phospholipids
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7
Q

What do detergent molecules form in order to remove oily stains?

A

They form micelles; encompassing the oily hydrophobic portion on its interior

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8
Q

sol state vs. gel state

A

Sol state tends to be at higher temperatures, and lateral diffusion can proceed rapidly
Gel state is at lower temperatures and PLs diffuse slowly

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9
Q

What is the temperature called at which a bilayer converts from the sol state to the gel state or vice versa?

A

Transition Temperature (TT)

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10
Q

Bilayers with PLs containing long saturated FA chains have what Transition Temperatures relative to bilayers with PLs containing shorter FA chains or double bonds?

A

Long saturated FA chains have relatively high TTs

Short FA chains or double bonds (generates kinks) do not interact well and therefore have lower TTs

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11
Q

What type of bases to membrane phospholipids typically have?

A

Glycerol or sphingosine bases

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12
Q

What is more common in membrane lipids, glycerol or sphingosine based?

A

glycerol

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13
Q

What part of the cholesterol molecule is the “head” in the membrane?

A

The hydroxyl group

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14
Q

Describe cholesterol and its relationship with membrane fluidity

A

Cholesterol reduces the fluidity, unless excessive; then become more fluid because falling apart

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15
Q

Explain phospholipids and cholesterol in relation to “flipping”

A

phospholipids rarely flip

cholesterol can flip easily

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16
Q

what is permeable to the phospholipid bilayer

A

small uncharged polar molecules

-O2, CO2, NH3 and water

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17
Q

Where are phosphatidylethanolamine, phosphatidylserine and phosphatidylcholine in relation to which side of the bilayer they are on

A 
Surface facing cytoplasm
-phosphatidylethanolamine
-phosphatidylserine
Outward facing surface
-phosphatidylcholine
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18
Q

What does Annexin V bind, and what does it detect?

A

It binds phosphatidylserine (PS)
Detects one of the earliest events in apoptosis- the externalization of PS in living cells
(soon after apoptosis is induced, PS is translocated from the inner leaflet to the outer leaflet of the plasma membrane)

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19
Q

What type of membrane proteins are bound the tightest? and what type of bond?

A

Integral proteins

Covalent bonds

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20
Q

What are proteins called that span the membrane once or more times?

A

Transmembrane proteins

21
Q

What type of structure do transmembrane proteins typically have?

A

hydrophobic a-helices

22
Q

Can transmembrane proteins move laterally?

A

Yes, as long as they are not bound to another protein

23
Q

Which molecule moves faster through the plane of the membrane, transmembrane proteins or lipids?

A

lipids;

transmembrane proteins are large molecules and therefore move slower

24
Q

What are some functions of integral proteins?

A 
receptors (transmit signals between the cell and its environment)
adhesion molecules
transporters
enzymes
signal transduction components
(form part of cytoskeleton)
25
Q

do steroid hormones utilize membrane proteins?

A

NO. they are lipid soluble molecules that do not utilize the membrane proteins

26
Q

T/F. All communication functions served by the plasma membrane occur through membrane proteins.

A

False. all except for lipid soluble signaling molecules (cholesterol)

27
Q

What physically happens to the protein when it binds a hormone (ligand) outside of the cell?

A

Causes a conformational change that is transmitted through the membrane-spanning region to the interior of the cell.

28
Q

What are the two types of adhesion molecules and examples for each

A
  • Cell-matrix adhesion molecules; integrins (links cells to components of extracellular matrix)
  • Cell-cell adhesion molecules (CAM); Cadhedrins (Ca-dependent), N-CAM (Ca-independent neural)
29
Q

What is a regulator for N-CAM?

A

polysialic acid

30
Q

Compare pores, channels, carriers and pumps

A

-Pore- always open, passive flow
-Channel- 1 gate, passive flow
-Carrier- 2 gates (1 open at a time), allows a specific molecule to pass or couples it with another solute
Pump- requires energy, move particle across membrane against concentration gradient

31
Q

Are ion pumps enzymes?

A

YES, since they catalyze ATP hydrolysis and use the released energy to drive the transport

32
Q

The nucleus and its organelles

A
  • Nucleolus- transcription of rRNA and assembly of ribosomal subunits (no membrane, just concentrated)
  • Chromatin- complex of DNA and numerous DNA binding proteins
  • Nuclear pore- pathway between nucleoplasm and cytoplasm
  • Nuclear lamina- fibrillar protein skeleton that provides structural support to the nuclear envelope (these proteins known as LAMINS)
33
Q

What happens in the Rough ER?

A
  • Synthesis of secretory and membrane proteins
  • These newly synthesized proteins undergo post-translational modification and folding in the lumen of the rER; (helps protein acquire mature conformation) Ex. glycosylation, hydroxylation, intramolecular disulfide bonds, tertiary structure formation
  • *misfolded proteins are tagged with ubiquitin to be degraded in the proteasome
34
Q

Explain secretory pathway and the two types

A

Secretory pathway; secretion of proteins

  • Constitutive pathway- secretion is continuous and unregulated
  • Regulated pathway- secretion is directed by hormonal or neural signal (a stimulus)
35
Q

Function of Smooth ER

A

Participates in lipid synthesis

Also stores Ca

36
Q

Function of the Golgi complex

A

-Station for further processing of proteins and targets newly formed proteins to the appropriate subcellular area

37
Q

Function of Lysosome

A
  • Digestive organelle of the cell that breaks down cellular debris
  • also contain degradative enzymes
  • Membrane contains proton pumps to ensure an acidic environment within itself
38
Q

What determines the cell shape? and what composed of?

A

Cytoskeleton, composed of protein filaments

39
Q

Order protein filaments in size, smallest to largest

A

Thin filaments- 5-8 nm
Intermediate filaments- 8-10 nm
Thick filaments- 10 nm
Microtubules- 25 nm

40
Q

What do epithelial cells separate?

A

the external milieu from the internal milieu

41
Q

What direction do apical membranes of epithelial cells face?

A

They face the lumen of a compartment that is often topologically continuous with the outside world

42
Q

What direction do the basolateral membranes of epithelial cells face?

A

They face the extracellular fluid compartment- which indirectly makes contact with the blood- and rest on a basement membrane

43
Q

What is the basement membrane in epithelial cells composed of and where do its materials come from?

A

Composed of extracellular matrix proteins secreted by the epithelial cells themselves.

  • collagen
  • lamin
  • proteoglycans
44
Q

What is it called where epithelial cells connect to each other?

A

Junctional complexes

45
Q

Function of tight junctions

A

to prevent the passage of molecules and ions between cells.

Ex. blood brain barrier

46
Q

Function of adhering junctions

A

Allows cell to recognize orientation relative to surrounding cells
(cadherins must be close enough in proximity)

47
Q

What are, and what is the function of Gap junctions?

A

Channels that interconnect the cytosols of neighboring cells.
-Use channels to communicate via the passage of inorganic or small molecules

48
Q

Function of Desmosomes

A

holds adjacent cells together at a single, round spot

Physio 504 (2 decks)

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