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Foundations Exam 1 > Intro to the Cell and Cell Membrane > Flashcards

Intro to the Cell and Cell Membrane Flashcards

1
Q

more integral membrane proteins are associated with the E or P face?

A

E = external face
P = protoplasmic/cytoplasmic face

more integral membrane proteins associated with P face, stabilized by cytoskeleton

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2
Q

hereditary spherocytosis

A

mutations in spectrins - cytoskeleton proteins that associate with membrane proteins to stabilize biconcave shape of erythrocytes

characterized by spherical RBCs, more susceptible to destruction in spleen

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3
Q

how is the plasma membrane of enterocytes in the brush border modified

A

tall, columnar - to increase surface area for nutrient absorption

micorvilli increase absorption as well (extend from apical surface)

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4
Q

glycocalyx

A

carbohydrate layer of eukaryotic cells

contains transmembrane glycoproteins, membrane glycolipids, proteoglycans

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5
Q

the main structural protein in microvilli is ____, which extends downward to terminate at _____ at apical surface of cell

A

actin, terminates at terminal web

[microvilli also contain myosin motor protein to move material along actin filament]

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6
Q

what are the 4 types of specializations of junctional complexes

A
  1. tight/occluding junctions (zonula occludens)
  2. belt desmosomes (zonula adherens)
  3. spot desmosomes (macula adherens)
  4. gap (communicating) junctions
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7
Q

what are microtubules composed of and how does this contribute to how they work

A

alpha-beta diametric tubulin molecules that assemble/disassemble into cylindrical structures

[form centrioles, cilia, mitotic spindle, cytoskeleton]

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8
Q

site of protein and lipid synthesis and calcium storage in cell

A

endoplasmic reticulum:
-SER (agranular): lipid and steroid biosynthesis, calcium storage, detoxification
-RER (granular): ribosomes for protein synthesis (secretory)

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9
Q

where are secretory proteins sent after they are made in RER

A

golgi apparatus for sorting

vesicles are usually used to transport material between Golgi cisternae (flattened sacs of membrane)

cis golgi is directed towards RER (proteins enter here)
trans golgi is directed towards secretory granules and peripheral cytoplasm (proteins leave here)

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10
Q

constitutive vs regulated secretion (all together makes exocitosis)

A

constitutive secretion: continual secretion of proteins that are not stored

regulated secretion: initiated by external stimulus, fusion of granules with cell surface to release contents

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11
Q

internalized vesicles fuse with the ____

A

early endosome - receptors and ligands are separated, receptors recycled to the surface

nutrients are routed to the lysosome and released from carrier proteins to become available

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12
Q

inner membrane of mitochondria is folded into ___

A

cristae

more cristae = higher energy need

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13
Q

most mitochondrial proteins are encoded by ___

A

nuclear DNA

enter from cytosol, not RER/golgi

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14
Q

site of intracelular digestion

A

lysosomes: contain hydrolytic enzymes that become active at acidic pH

ATP-driven proton pump in lysosomal membrane maintains pH

degrade external molecules, worn-out organelles, entire cells following phagocytosis

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15
Q

hydrogen peroxide metabolism and fatty acid metabolism occurs in what part of the cell

A

peroxisome

have high enzyme concentrations, so have dense material in matrix that forms crystalline core

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16
Q

what are the 4 classes of membrane lipids

A
  1. phosphoglycerides: derived from 3C glycerol and 2 fatty acid chains attached (3 subtypes)
  2. sphingolipids
  3. glycolipids: sphingosine backbone with carbohydrate
  4. sterols (primarily cholesterol)
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17
Q

basic structure of phosphoglycerides

A

2 or 3C of glycerol backbone + fatty acid chains

one chain usually non-saturated —> has kink that inhibits dense packaging (—> increases fluidity)

remaining hydroxyl attached to phosphate and one of 3 major head groups (at head of structure)

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18
Q

what are 3 major phosphoglyceride subtypes

A
  1. phosphatidyl-ethanolamine
  2. phoshatidyl-serine (NEG charge)
  3. phosphatidyl-choline
19
Q

structure of sphingomyelin (major sphingolipid of PM)

A

sphingosine with fatty acid tail and phosphotidylcholine attached

20
Q

structure of cholesterol

A

polar sterol, contains:
-polar OH near membrane surface in both leaflets
-rigid sterol ring (stiffens membrane)
-aliphatic region keeps FA chains of phospholipids apart

21
Q

what type of glycolipid is charged

A

ganglioside

(GM1 ganglioside mediates entry of cholera toxin)

22
Q

structure of glycolipids

A

sphingosine + sugar (instead of phosphate)

asymmetric - sugar on external PM surface only

ganglioside class is charged

23
Q

why is cholesterol absent from bacteria and plants?

A

bacteria and plants have cell walls - don’t need it

cholesterol takes on the role of cell wall in eukaryotes in a way by providing structural rigidity around it

(note that cholesterol doesn’t show leaflet asymmetry - evenly distributed)

24
Q

these areas of non-random lipid distribution can occur within inner or outer PM leaflet. They have a thicker structure (longer hydrophobic chains) and can sequester subsets of membrane proteins to segregate function. what are?

A

lipid raft

25
Q

phosphatidyl serine imparts a __ charge to internal face of PM

A

negative

26
Q

describe the ability of each of these to pass through PM:
a. hydrophobic molecules
b. small uncharged polar
c. large uncharged polar
d. ions

A

a. hydrophobic (O2, CO2, N2, steroids) —> YES
b. small uncharged polar (H2O, urea, glycerol) —> some
c. large uncharged polar (glucose, sucrose) —> less
d. ions —> NO

27
Q

what are the 3 types of ion transporters and their characteristics

A
  1. pump: specific enzymes, against gradient (ATP required)
  2. carrier: downhill gradient, passive transports, conformational change
  3. channel: ion specific pore, downhill gradient, open/close in regulated manner

very important in intestinal epithelial, kidney epithelial, nerve

28
Q

what do tetrodotoxin and lidocaine both do

A

sodium channel blockers

tetrodotoxin (puffer fish) - causes paralysis
lidocaine - anesthetic to treat tachycardia

29
Q

what does curare do

A

blocks Na/K ion channel by competitively antagonizing nicotinic Ach receptors at neuromuscular junction

causes paralysis

30
Q

Glut1 glucose transporter is an example of:
a. uniporter
b. symporter
c. antiporter

A

Glut1 is uniporter - transport rate depends on concentration gradient, binding affinity (Km), flipping rate (Vmax)

conformational change dumps glucose to other side quicker than diffusion

(transporters follow enzyme kinetics)

31
Q

in the Na+/glucose symporter, which molecule is moving against its concentration gradient

A

binding of Na+ increases affinity of symporter for glucose. Both Na+ and glucose sites need to be occupied for conformational change

glucose moves against gradient without direct energy expenditure

32
Q

glucose transport from digestive system through epithelial cells uses 2 glucose transporters:

A

first step: symporter with Na+ (sodium moving down gradient, glucose against) - at lumen of GI tract (apical surface)

second step: uniporter (glucose goes down gradient) - at basal domain of cell
-Na+/K+ pump compensates for increased sodium that is not leaving with glucose this side

key here is there is high glucose concentration in the brush border cells

33
Q

two types of transporter pumps (active transport)

A
  1. P-type pump: auto-phosphorylation using ATP, conformational change follows
  2. ABC transporter - pump small molecules (not ions, usually), also use ATP
34
Q

what kind of transporter pump is Ca2+ ATPase

A

P (phosphorylation) type pump:

  1. Ca2+ concentration in ER needs to be re-established after muscle contraction
  2. Ca2+ binds non-phosphorylated pump
  3. ATP binds and auto-phosphorylation occurs
  4. conformational change opens channel to lumen of SR (muscle’s ER)
35
Q

what kind of pump transporter is Na+/K+ ATPase

A

P-type (phosphorylation)

both Na+ and K+ go against concentration gradient

  1. THREE Na+ binds inside cell
  2. auto phosphorylation and conformational change
  3. Na+ released outside
  4. dephosphorylation and another conformational change
  5. TWO K+ released into cell
36
Q

mechanism of ABC transport pumps

A

ATP Binding Cassettes:

  1. two ATPase domains on each protein, small molecules bind to non-ATP bound state
  2. ATP binds, dimerization
  3. confirmation change and release
  4. ATP hydrolysis for another round

bacterial ABC import, eukaryotic ABC export (euk = export)

37
Q

multiple drug resistance (MDR) in tumor cells arises from high levels of one type of ____ transporter

A

ABC

consequence is more hydrophobic drug is cleared from cytoplasm

38
Q

how does malaria develop chloroquine resistance

A

amplified levels of ABC transporter pump drug out

39
Q

what kind of pump transporter is CFTR

A

ABC transporter - exception example when ABC transports ion, not small molecules

40
Q

where in the plasma membrane are spingolipids and phosphotidyl choline found

A

glycolipids found in outer leaflet

41
Q

what is the most specific transporter, and what is the most rapid?

A

most specific - pump
most rapid - channel

(carriers are intermediate in both categories)

42
Q

lipid rafts are composed mostly of ____

A

cholesterol and sphingomyelin

43
Q

major digestive organelle

A

lysosome

Foundations Exam 1 (33 decks)

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