Lecture 2: Membranes and Transport Flashcards Preview

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Flashcards in Lecture 2: Membranes and Transport Deck (93):
1

Describe the role of membranes

-Physical protective barrier
-Gives cell shape
-Separates intracellular environment from external medium
-Selective permeability
-Transport
-Maintain electrochemical potential

2

What are membranes composed of?

-Lipids, proteins and carbohydrates

3

What are the primary components of membranes?

-Phospholipids (PL)

-Amphipathic; hydrophilic head group, hydrophobic tail

4

What is the arrangement of phospholipids in the membrane?

-Hydrophilic head groups face the aqueous environment outside
-Hydrophobic tails face the interior and form the hydrophobic core of the membrane

5

What are the 3 types of membrane lipids?

1. Phospholipids (PLs)
2. Glycolipids
3. Cholesterol

6

Phospholipids | What are the two different types based on backbone?

1. Glycerophospholipids; glycerol backbone
2. Sphingolipids (SL); sphingosine backbone

7

Describe Glycolipids

Sphingosine backbone with carbohydrate (oligosaccharide) residues, found in outer leaflet of the lipid bilayer

8

Describe Cholesterol

Embedded in lipid bilayer, steroid nucleus with a hydroxyl group and hydrocarbon-side-chain

9

CORRELATION BOX: Phosphatidylserine

-Marker for apoptosis
-Healthy cells, PS found in inner leaflet of bilayer
-During apoptosis-PS displayed on outer leaflet of bilayer
-Serves as tag/layer

10

CORRELATION BOX: Niemann-Pick Disease

-Caused by deficiency in activity of Acid Sphingomyelinase (A-S Mase)
-A-SMase breaks down sphingomyelin
-Leads to enlargement of liver and spleen and neurological damage
-Hallmark "cherry red spot" in eye

11

What are the 3 types of membrane proteins?

1. Integral membrane proteins
2. Peripheral proteins
3. Lipid-anchored proteins

12

Describe how the three types of membrane proteins are attached.

1. Integral membrane proteins: embedded in membrane, stabilized by hydrophobic interactions with lipids

2. Peripheral proteins; loosely bound to membrane through

13

Describe how the three types of membrane proteins are attached.

1. Integral membrane proteins: embedded

2. Peripheral proteins; attached

3. Lipid-anchored proteins; tethered

14

Describe Carbohydrates in relation to the membrane

-Covalently attached to some membrane lipids and proteins that face extracellular space
-Creates carbohydrate shell called GLYCOCALYX

15

What is the function of the GLYCOCALYX?

1. Protection
2. Cell adhesion
3. Cell identification

16

The ABO Blood System:
Describe

-Red blood cells have antigens on their surface

17

ABO Blood System:

Universal Donor? Universal acceptor?

Donor: Type O

Acceptor: Type AB

18

What factors influence membrane fluidity?

A. Temperature
B. Lipid composition
C. Cholesterol

19

Describe the effects of high and low temp on membrane fluidity

High temp=more fluid
Low temp=more rigid

20

Describe the effects of lipid composition on membrane fluidity

Saturated fatty acids=decrease membrane fluidity

Unsaturated fatty acids=increase membrane fluidity

21

Describe the effects of cholesterol on membrane fluidity

Cholesterol in rigid membrane=increase fluidity

Cholesterol in fluid membrane=decrease fluidity

22

CORRELATION BOX: Spur cell anemia

-Type of hemolytic anemia
-Elevated levels of cholesterol in rbc membrane
-Decreases fluidity and flexibility of membrane
-Cause rbcs to break their membranes as they pass through capillaries of spleen

23

Membrane is permeable to...

Lipophilic molecules;

*move easily via diffusion, e.g. steroid hormones

24

Membrane is impermeable to...

Hydrophilic/polar molecules: need specific transport mechanism

25

Ion gradients:

Na+, K+, Cl-, Ca2+

Which have higher concentrations extracellularly?

Na+, Cl-, Ca2+

26

Ion gradients:

Na+, K+, Cl-, Ca2+

Which have higher concentrations intracellularly?

K+

27

Describe Passive vs. Active transport

Passive: energy independent mechanism, molecules move DOWN their concentration gradient

Active: energy dependent, molecules move AGAINST their concentration gradient

28

What are the two types of Passive transport?

1. Simple diffusion
2. Facilitated diffusion

29

Describe Simple Diffusion

-Occurs unaided
-molecules that are small, non-polar and uncharged polar diffuse freely across membrane

30

Describe facilitated diffusion

-Needs assistance of transmembrane proteins
-Molecules that are large and charged are unable to cross the membrane
-Need a facilitator

31

Give an example of passive transport: simple diffusion

Small nonpolar molecules: O2, N2, ethanol, diethylether, benzene

Small polar uncharged molecules: H2O, CO2, NH3, Urea

32

Give an example of passive transport: facilitated diffusion

-Voltage gated Na+ channel
-Glucose transporter (GLUT1)

33

What is an Ion Channel?

pores in membrane which allow charged and polar molecules to move across membranes down their concentration gradient

***Transport million of molecules per second

34

Describe active transport

Energy dependent, protein-assisted movement of molecules against their concentration gadient

35

What is the difference b/w primary and secondary active transport?

Primary: Use ATP directly

Secondary: Use energy stored in a concentration gradient; coupled to primary transport system

36

What is P type ATPase?

Use energy from ATP hydrolysis to drive transport against gradient;

Transporter forms a COVALENT BOND with the phosphate to form an enzyme-phosphate intermediate (ON ASPARTATE)

37

Special fact about ABC transporters?

ATP HYDROLYZED BUT DOES NOT PHOSPHORYLATE THE PROTEIN

38

Describe Secondary Active Transport:

-Moves molecules against their concentration gradient in an energy dependent protein-assisted manner

39

What are the most abundant lipids found in biological membranes?

Phospholipids (PLs)

40

What is a glycerophospholipid?

Glycerol backbone w/ phosphate and two fatty acids esterified to a backbone

41

What are examples of glycerophospholipids?

-Phosphatidylcholine
-Phosphatidylserine
-Phosphatidylinositol

42

What is a Sphingolipid?

Sphingosine backbone with a long chain fatty acid and phosphorylcholine

43

What are some examples of sphingolipids?

-Sphingomyelin

***Most common SL present in OUTER leaflet

44

Where is sphingomyelin present?

OUTER LEAFLET of lipid bilayer

45

What is a Glycolipid?

Sphingosine backbone w/ carbohydrate residues

46

Where are Glycolipids found?

OUTER leaflet of lipid bilayer

47

What is Cholesterol?

Steroid nucleus w/ hydroxyl group and hydrocarbon side-chain

48

Cholesterol form ______ concentrated in PM compartments that are important for cell signaling

Lipid rafts

49

Where is Phosphatidylserine?

Inner leaflet of bilayer

50

CORRELATION BOX: What is a marker for apoptosis?

Phosphatidylserine on outer leaflet

51

CORRELATION BOX: Describe where phosphatidylserine is located in healthy cells

Inner leaflet of bilayer

52

CORRELATION BOX: Niemann-Pick Disease

What is it caused by?

Deficiency in activity of ACID SPHINGOMYELINASE (A-SMase)

53

CORRELATION BOX: Niemann-Pick Disease

What is the function of Acid Sphinomyelinase (A-SMase)?

Lysosomal enzyme that breaks down sphingomyelin (SM)

54

CORRELATION BOX: Niemann-Pick Disease

Describe what occurs in clinical manifestation:

-SM accumulates in lysosomes of liver, spleen, CNS and bone marrow

-Leads to enlargement of liver and spleen and neurological damage

55

CORRELATION BOX: Niemann-Pick Disease

Hallmark identifier of disease?

"Cherry red spot" in the eye

56

What are the three types of membrane proteins?

1. Integral membrane proteins
2. Peripheral proteins
3.Lipid-anchored proteins

57

Functions of glycocalyx?

1. Protection
2. Cell adhesion
3. Cell identification

58

CORRELATION BOX: Rh factor and hemolytic disease of a newborn

Define: Erythroblastosis fetalis

Disease in which incompatibility between blood and mother of fetus

-When mom is Rh- and fetus is Rh+, mom produces antibodies during pregnancy. These cross placenta and attack the fetus. Risk is greater in subsequent pregnancies

59

CORRELATION BOX: Rh factor and hemolytic disease of a newborn

Rh+ individuals...

express the D antigen

60

CORRELATION BOX: Rh factor and hemolytic disease of a newborn

Rh- individuals...

do no express the D antigen

61

CORRELATION BOX: Ligand gated ion channels

Name an example:

Glutamate receptor

62

CORRELATION BOX: Ligand gated ion channels

describe what a ligand -gated ion channel does

Responsive to ligands;

binding of ligand (e.g., neurotransmitter or hormone) to ion channel causes conformational changes in the protein

63

CORRELATION BOX: Voltage-gated ion channels

Describe what is occurring in closed, open and inactivated periods;

Closed: At resting potential, channel closed

Open: In response to a nerve impulse, gate opens and Na+ enters the cell

Inactivated: Channel does not open in response to new signal for brief period of time

64

What is the toxin derived from puffer fish that blocks voltage gated ion channels?

tetrodotoxin

65

What are examples of SECONDARY TRANSPORTERS:

Antiporters

-Sodium Calcium Exchanger

66

What are examples of SECONDARY TRANSPORTERS:

Symporter

Lactose permease

67

What are examples of SECONDARY TRANSPORTERS:

Uniporter

Mitochondrial calcium transporter

68

Where is the sodium glucose transporter (SGLT1) located? secondary transporter

epithelial cells that line small intestine and renal tubules

69

What is the function of sodium glucose transporter (SGLT1)? secondary transporter

Controls UNIDIRECTIONAL movement of Na+ and glucose across small intestine and renal tubules,

movement DOWN it's gradient

70

How is the SGLT1 Na+ gradient reset?

Na+/K+-ATPase

71

What kind of transporter is Na+-Ca2+ (NCX)?

Antiporter

72

What is the function of Na+-Ca2+ exchanger?

Maintain low levels of intracellular calcium in cells

73

What is the mechanism of Na+-Ca2+ (NCX) exchanger?

Imports 3Na+ down their concentration gradient and exports 1 Ca2+ against it's gradient


***uses the energy stored in the Na+ gradient

74

What is the mechanism of NCX?

Uses the energy of the Na+ gradient to transport Ca2+ against it's gradient

75

What is the basolateral side of a cell?

Faces the bloodstream

76

What uptakes D-glucose and D-galactose into the cells?

secondary active transport via SGLT1

77

How is glucose and galactose transported into the blood stream?

facilitated diffusion with glucose transporter (GLUT2)

78

CLINICAL CORRELATION: What leads to cystic fibrosis?

Defective chloride transport

79

CLINICAL CORRELATION: What type of genetic disorder is cystic fibrosis?

autosomal recessive

80

CLINICAL CORRELATION: What mutation causes cystic fibrosis?

Mutation in cystic fibrosis transmembrane conductance regulator (CFTR gene)

81

CLINICAL CORRELATION: what is CFTR? cystic fibrosis

A chloride channel that mediates the active transport if Cl- from inside cells to the outside in airways and sweat ducts

82

CLINICAL CORRELATION: What does a defective CFTR cause

Buildup of Cl- inside the airway epithelial cells...

Thicker mucous and leaves the airways susceptible to bacterial infections

83

CLINICAL CORRELATION: What leads to Cystinuria?

Defective amino acid transporter

84

CLINICAL CORRELATION: What type of genetic inheritance does cystinuria have?

autosomal recessive

85

CLINICAL CORRELATION: What is Cystinuria caused by?

Defect in the transport responsibile for the uptake of dimeric amino acid CYSTINE and... arginine, lysine and ornithine

86

CLINICAL CORRELATION: What is the result of Cysinuria:

Formation of CYSTINE CRYSTALS or STONES in the kidney....

pts present with RENAL CHOLIC (abdominal pain that comes in waves and is linked to kidney stones)

87

CLINICAL CORRELATION: What leads to HARTNUP disease?

Defective amino acid transporter

88

CLINICAL CORRELATION: What type of genetic inheritance does HARTNUP disease have?

autosomal recessive

89

CLINICAL CORRELATION: What is the specific defect in amino acid transporter?

Defect in a transporter for non-polar or neutral amino acids

90

CLINICAL CORRELATION: What are the clinical findings for HARTNUP disease?

Cerebellar ataxia, nystagmus, photodermatitis and photosensitivity

91

Name a cardiac glycoside/cardiotonic drug

Ouabain, Digoxin

92

What do cardiotonic drugs do?

Inhibit the Na+/K+ ATPase on cardiac myocytes...

Leads to increase in intracellular Na+ and secondary increase in Ca2+ due to slowing of NCX

93

Describe the mechanism of how cardiotonic drugs, Ouabain and Digoxin work

Increase sarcoplasmic Ca2+ results in stronger excitation contraction of heart muscle with each action potential