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SFM DSA’s 7/27-7/31 > Membranes and Transport > Flashcards

Membranes and Transport Flashcards

1
Q

Physiological Role of Membranes

  • physical ______ _______ around cells and organelles
  • gives cell its _______ ______
  • separates the _______ environment from the ______ medium
  • ____________ of organelles
  • aids in _____ recognition
  • provides _________ site for cytoskeletal elements
  • ________ site for hormones and enzymes
  • maintain ________ potential (membrane excitability)
  • interlocking surfaces _____ cell together (tissue structure/gap junctions)
    • _______ permeability of metabolites
    • ______: exchange of material (nutrition, oxygen, waste, ions)
A
  • protective barrier
  • characteristic shape
  • intracellular, external
  • compartmentalization
  • cell
  • anchoring
  • binding
  • electrochemical
  • binds
  • selective
  • transport
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2
Q

General Structure and Composition

  • membranes are composed of ____, _____, and __________
  • arranged in ______ bilayer
  • ____ permeable (allows small molecules and lipid soluble molecules to diffuse through)
  • primary components of membranes are ________
A
  • lipids, proteins, carbohydrates
  • asymmetric
  • semi
  • phospholipids
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3
Q
  • main component of membranes

- amphiphatic: contain a hydrophilic head group and a hydrophobic tail group

A

phospholipids

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4
Q

Membrane Composition

  • lipid bilayer serves are the _______ in which a variety of lipids and proteins are embedded, attached, or anchored
  • carbohydrate molecules are ________ attached to some membrane lipids or proteins
A
  • foundation

- covalently

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5
Q

What are the two types of phospholipids?

A

glycerophospholipids and sphingolipids

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6
Q
  • phospholipid
  • glycerol backbone with a phosphate and two fatty acids esterfied to backbone
  • e.g. phosphatidylcholine, phosphatidylserine, phosphatidylinositol
A

glycerophospholipids

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7
Q
  • phospholipid
  • sphingosine backbone with a long chain fatty acid and phosphorylcholine
  • sphingomyelin (most common SL present in outer leaflet)
A

sphingolipids

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8
Q

What are the 3 types of membrane lipids?

A

phospholipids, glycolipids, cholesterol

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9
Q
  • membrane lipid
  • sphingosine backbone with carbohydrate (oligosaccharide) residue(s)
  • found in outer leaflet of lipid bilayer
A

glycolipids

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10
Q
  • membrane lipid
  • embedded in lipid bilayer
  • steroid nucleus with hydroxyl group and hydrocarbon side chain
  • the hydrocarbon chain interacts with hydrophobic tails of membrane lipids
A

cholesterol

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11
Q

What are the 3 types of membrane proteins?

A

intergral, peripheral, and lipid-anchored

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12
Q
  • membrane protein
  • firmly embedded in the membrane and stabilized by hydrophobic interactions with lipids
  • polytopic membrane proteins (includes transporters, ion channels, and receptors
A

integral membrane proteins

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13
Q
  • integral membrane proteins that span the entire lipid bilayer, weave in and out of the membrane several times and interact with both the internal and external environment
  • include transporters, ion channels, and receptors that regulate the movement of molecules across membrane and receive and transmit signals from external environment of the cell
A

polytopic transmembrane proteins

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14
Q
  • membrane protein

- loosely bound to membrane through electrostatic interactions with lipids or proteins

A

peripheral proteins

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15
Q
  • membrane protein

- tethered to membranes via covalent attachment to a lipid

A

lipid-anchored proteins

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16
Q
  • carbohydrate molecules are ______ attached to specific membrane lipids and proteins that face extracellular space
  • outer sheet of some membranes covered with a carbohydrate shell called ______ due to presence of glycolipids and glycosylated proteins
A

covalently, glycocalyx

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17
Q

What are the 3 key functions of glycocalyx?

A
  • protection: protects membrane components from mechanical injury or premature enzymatic degradation
  • cell adhesion: makes more stable contacts with other cells, important during tissue formation and fertilization
  • cell identification: allows body to differentiate between its own healthy cells from forge in, very important in red blood cells
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18
Q 
Membrane Fluidity
- proteins and lipids \_\_\_\_\_ and move \_\_\_\_\_\_ in membranes
- gives it a fluid like quality
- crucial for \_\_\_\_\_\_
allows proteins and lipids to undergo \_\_\_\_\_\_\_\_\_\_ changes and/or to move to specific areas within membrane to carry out \_\_\_\_\_\_
- factors that influence fluidity:
     A. temperature
     B. lipid composition
     C. cholesterol
A
  • rotate, laterally
  • function
  • conformational, function
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19
Q

What are the 3 factors that influence membrane fluidity?

A

temperature, lipid composition, cholesterol

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20
Q

What is the temp at which membranes switch from fluid to rigid state?

A

melting temp (Tm)

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21
Q

Temperature

  • below Tm membrane lipid molecules show ordered packing which makes membranes _____
  • above Tm membranes are more _____
  • Temp > Tm is optimal fluidity
A
  • rigid

- fluid

22
Q

Lipid Composition

  • lipids that contain long, saturated fatty acids ______ membrane fluidity due to tight packing which reduces their mobility
  • lipid with short, unsaturated fatty acid chains ______ membrane fluidity because the kinks in their fatty acid chains do not allow tight packing
A
  • decrease

- increase

23
Q

saturated lipids = ______ fluidity

unsaturated lipids = _______ fluidity

A

decrease, increase

24
Q

Cholesterol in Membrane

  • can either increase or decrease fluidity
  • if membrane is too rigid (high sat fats or temp below Tm), cholesterol intercalates into membrane and _______ fluidity by preventing close packing of the lipids
  • if membrane is fluid (high unsat fats), cholesterol ______ fluidity by fitting in gaps created by kinks in the tail lipids
  • ______ large changes in fluidity caused by temperature
A
  • increases
  • stabilizes
  • reduces
25
Q

cholesterol in rigid membrane = ______ fluidity

cholesterol in fluid membrane = ______ fluidity

A

increase, decrease

26
Q

Membrane Transport

  • plasma membrane is ____-_______
  • permeable to ______ molecules, move easily via diffusion (e.g. steroids)
  • impermeable to ________ molecules, need a specific transport mechanism
  • integral membrane proteins embedded in membrane function as ______ proteins
  • membranes ______ the flow of biomolecules into and out of cells
  • control biochemical properties of cell
A
  • semi-permeable
  • lipophilic
  • hydrophilic/polar
  • transporter
  • regulate
27
Q

In terms of Na+, K+, and Cl-, what are the conc intra and extracellularly

A

Na+ and Cl- higher extracellularly,

K+ higher intracellularly

28
Q
  • energy-independent movement of molecules down a gradient (higher conc to lower conc)
  • two types: simple diffusion and facilitated diffusion
A

passive transport

29
Q
  • passive transport
  • occurs unaided
  • molecules that are small, non-polar and uncharged polar diffuse freely across the membrane
  • steeper the gradient, faster the diffusion
A

simple diffusion

30
Q
  • passive transport
  • needs the assistance of transmembrane proteins
  • molecules that are large and charged are unable to cross the membrane
  • need a facilitator (proteins that help movement)
  • proteins function as ion channels or transporters
  • greatly increase rate of transport
A

facilitated diffusion

31
Q
  • pores or gates in membrane which allow charged and polar molecules (e.g. ions and water) to move across membranes down their concentration gradient
  • open/close in response to stimuli
  • channels high throughout (transport millions of molecules per second)
A

ion channels

32
Q
  • ion channel
  • binding of ligand (e.g. neurotransmitter or hormone) to ion channel causes conformation changes in the protein
  • facilitate opening of the channel, allowing rapid transport of ions across membrane
  • ions move down concentration gradient
  • dissociation of ligand closes the channel
  • example: glutamate receptor: antagonist of glutamate receptor used to treat Alzheimer’s disease (Mimantine/Namenda)
A

ligand-gated ion channels

33
Q
  • ion channel
  • open/close in response to changes in membrane potential
  • electrical voltage across the lipid bilayer created by large excess of negative charge inside the cell
  • depolarization (increase in membrane potential due to influx of positively charged ions) triggers the opening of these channels permitting specific ions to cross the bilayer down their conc gradient
  • found in excitable cells, such as neurons
  • example: sodium channel
A

voltage-gated ion channels

34
Q
  • puffer fish example: has toxin called tetradotoxin which binds to sodium channel and inhibits neurotransmission
  • topical anesthetics: block sodium channel, inhibit nt, used in clinic to block pain
A

consequences of blocking ion channels

35
Q
  • membrane transport
  • energy-dependent, protein-assisted movement of molecules against their concentration gradient
  • mediated by integral membrane proteins (polytopic transmembrane protein transporters)
  • bind to a specific molecule on one side of membrane and release it on the other side
  • 2 types: primary (uses ATP directly) and secondary (coupled to primary transport)
A

active transport

36
Q
  • active membrane transport
  • uses ATP directly
  • P type ATPases: ATP hydrolyzed, protein gets phosphorylated
  • ABC transporters: ATP hydrolyzed, protein not phosphorylated
A

primary active transport

37
Q
  • active membrane transport
  • does not use ATP, uses energy stored in concentration gradient
  • thermodynamically unfavorable flow of one species of ion against a gradient coupled to a favorable flow of another species down a gradient
A

secondary active transport

38
Q
  • monosaccharides derived from digestion need to be transported from intestinal ____, across the ______ into the _____ ______
  • this transport process is facilitated by ______ diffusion (passive) and ______ transport
A
  • lumen, enterocyte, blood stream

- facilitated, active

39
Q

Transport Mechanisms in Uptake of Dietary Monosaccharides

  • D-_____ and D-______ enter intestinal ________ cells from lumen along with ___ by _______ active transport mediated by sodium-glucose transporter 1 (_____) in apical surface
  • ______ transported only by ______ diffusion down its concentration gradient using GLUT5 transporter on _____ side and _____ transporters on _____ side of enterocyte
  • ___ transported in by SGLT1 is delivered to the blood stream using a ______ active transport process mediated by _________ in the basolateral membrane
A
  • glucose, galactose, epithelial, Na+, secondary, SGLT1
  • fructose, facilitated, apical, GLUT2, basal
  • Na+, primary, Na+/K+-ATPase
40
Q
  • caused by deficiency in the activity of an enzyme called acid sphingomyelinase (A-SMase)
  • A-SMase is a lysosomal enzyme which breaks down sphingomyelin (SM) into ceramide and phosphorylcholine
  • defective A-SMase leads to accumulation of SM in lysosomes of liver, spleen, CNS, and bone marrow
  • leads to: enlargement of liver and spleen
  • causes neurological damage
  • hallmark “cherry red spot” in the eye
  • fatality: type A is 85% by 18 months of age
A

Niemann-Pick disease

41
Q
  • in healthy cells, phosphatidylserine (PS) found in inner leaflet of bilayer
  • during apoptosis, PS is transferred to outer leaflet of bilayer
  • serves as tag/label for dying cells to be recognized and removed by phagocytes
A

phosphatidylserine as a marker for apotosis

42
Q
  • type of hemolytic anemia
  • associated w/ beta lipoproteinemia and advanced alcoholic cirrhosis
  • chronic liver dysfunction impairs cholesterol metabolism in liver, results in excess free cholesterol
  • elevated levels of cholesterol bound to RBC membrane
  • decrease fluidity and flexibility of membrane
  • creates rough, thorny projections on RBC’s, acanthocytes
  • cause RBC’s to lyse as they pass through capillaries of spleen = reduced RBC survival
  • prognosis is poor, median survival is a few months
  • liver transplantation represents the only potentially curative option
A

spur cell anemia

43
Q
  • autosomal recessive disorder
  • caused by defect in transporter responsible for uptake of dimeric amino acid, Cystine, and dibasic amino acids such as Arginine, Lysine, and Ornithine
  • results in formation of cystine stones in kidney
  • patients present with renal cholic (abd pain that comes in waves and is linked to kidney stones)
A

cystinuria

44
Q
  • autosomal recessive disorder
  • caused by defect in a transporter for non-polar or neutral amino acids (e.g. alanine, valine, threonine, leucine, tryptophan, etc.)
  • primary in kidneys and intestine
  • deficiency in tryptophan (precursor for serotonin, melatonin, and niacin) affects health
  • manifests in infancy as failure to thrive
  • clinical findings: intermittent cerebellar ataxia (lack of muscle coordination), nystagmus (rapid and repetitive eye movement), tremor, photo dermatitis, and photosensitivity
  • triggered by sunlight, fever, drugs, or stress
  • period of poor nutrition almost always precedes and attack
A

Hartnup disease (pellagra-like dermatosis)

45
Q

Cardiotonic Drugs

  • cardiac _____ such as ouabain and ______ act as potent cardio tonic (contraction-inducing) drugs
  • _____ the Na+/K+-ATPase in cardiac myocytes
  • leads to ______ in intracellular Na+
  • this impairs activity of the secondary transporter _____ ______ ______ (NCX) which is coupled to the Na/K-ATPase
  • impairment of NCX leads to secondary _______ in ___ in sarco-endoplasmic reticulum, which in turn ______ the ________ force of cardiac ______
  • therapeutic use: congestive heart failure, atrial fibrillation, dysrhythmias
  • historically: plant extracts containing cardiac glycosides (foxglove, oleander, lily of the valley) have been used as arrow coatings, homicidal/suicidal aids, rat poisons, diuretics, and emetics
  • purified extracts/synthetic analogues now used for tx of CHF and arrhythmias
A
  • glycosides, digoxin
  • inhibits
  • increase
  • sodium calcium exchanger
  • increase, Ca+, increases, contractile, myocytes
46
Q
  • autosomal recessive disorder
  • mutation in _____ ______ transmembrane conductance regulator (CFTR) gene
  • defective CFTR protein is misfiled and does not leave ER after translation
  • CFTR protein is a chloride ion channel that mediates active transport of Cl- from inside to outside cells in airways and sweat ducts
  • uses energy of ATP hydrolysis
  • defective CFTR causes buildup of Cl- inside airway epithelial cells
  • compensated by increase in Na+, which makes NaCl (salt)
  • water flows into airway cells to compensate for increased salinity, decreasing the water content of surface mucous layer
  • this leads to thicker mucous and leaves airways susceptible to bacterial infections
A

cystic fibrosis

47
Q

red blood cells have _____ on their surface, which are different ________ attached to proteins (______) and lipids (________) on RBC membrane

A

antigens, carbohydrates, glycoproteins, glycolipids

48
Q

Why is important to cross-match blood types when performing a blood transfusion?

A

Because plasma of recipient may contain antibodies to one or more of the ABO and Rh antigens. Incompatible transfusion could result in acute hemolysis, renal failure, and shock.

49
Q
  • RBC antigens that are applied to D antigen
  • inherited in an autosomal dominant fashion
  • (+) individuals express D antigen, (-) individuals do not
A

Rh factor

50
Q
  • disease in which there is incompatibility between blood of mother and fetus
  • when mom is Rh- and fetus is Rh+, the mom produces antibodies during pregnancy which can cross the placenta and attack fetus
  • risk is greater in subsequent pregnancies
A

hemolytic disease in newborns (erythroblastosis fetalis)

SFM DSA’s 7/27-7/31 (6 decks)

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