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M1 > Membrane Structure and Function > Flashcards

Membrane Structure and Function Flashcards

1
Q

Membranes grow through

A

enlargement of preexistant membranes

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2
Q

The ER incorporates membranes:

A
  1. lipid from the cytosol
  2. proteins through addition or synthesis
  3. carbohydrate addition occurs in Golgi
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3
Q

Double line at high magnifications

A

Cell membrane (7.5 nm thick)

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4
Q

The two sides (leaflets) of all membranes

A

C = cytoplasmic/nucleoplasmic side

E= exoplasmic side

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5
Q

term to describe a membrane meaning that they have a hydrophobic part and hydrophilic part

A

amiphillic

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6
Q

Aliphatic, nonpolar chains of fatty acids

A

hydrophobic

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7
Q

Carboxyl groups that make up the head group of the fatty acids

A

hydrophillic part that faces externally

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8
Q

structure with fatty acid tail and contains carboxyl groups studded on the head group

A

glycolipid

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9
Q

contains a phosphate with a type of polar group attached

A

phospholipid

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10
Q

Some PLs and all GLs are _______

A

sphingolipids

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11
Q

GLs which contain sialic acids

A

gangliosides

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12
Q

In cellular membranes, the bilayer is __________

A

asymmetric

Mixture of PLs and GLs spontaneously form a bilayer membrane in an aqueos solution

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13
Q

Membrane asymmetry

C leaflet:

E leaflet:

A
  • C leaflet: most phoshatidyl serine (PS) and phosphatidyl ethanolamine (PE)
    • lipid-linked protein
  • E leaflet: most phosphatidyl choline (PC) and sphingomyelin (SM) and ALL glycolipids (GL)
    • CHO groups on membrane proteins
    • GPI-linked proteins
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14
Q

enzyme that causes the lost of asymmetry in some cell membranes

A

scramblases

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15
Q

The presence of PS on the outer surface (E leaflet) triggers _________ of aged cells by _________

A

phagocytosis, macrophages

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16
Q

Makes up about 20% of plasma membrane lipid

A

cholesterol

it can move in the plane of the membrane and between leaflets (“flip-flop”)

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17
Q

Cholesterol decreases the membrane ____________ to small molecules

A

permeability

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18
Q

Membrane proteins and glycoproteins help with:

A
  • signaling
  • transport across the membrane
  • cell adhesion
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19
Q

In single pass transmembrane proteins, CHO is always on the _____ side of the cell membrane

Functions:

A

E side

function: receptors

cell recognition

cell attachment

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20
Q

Epidermal growth factor (EGF) receptor

-tyrosine kinase signaling steps:

A
  1. Ligands (EGF) bind to receptors
  2. Receptors form dimers
  3. Dimers cross-phosphorylate their cytoplasmic tails
  4. Tyrosine kinase domains activated
  5. Other proteins phosphorylated
  6. Cell proliferation stimulated
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21
Q

Large multipass transmembrane proteins functions:

A
  • receptors(G protein coupled receptor)
  • transport proteins ion channels (connexin)
    • ion pumps
    • glucose transporters

etc.

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22
Q

Acetylcholine receptors (nicotinic) in the membranes of skeletal muscle cells are _________ membrane proteins.

A

multipass

A group of five receptors make one ion channel in the membrane.

  1. Ion channel is blocked
  2. Two AChs bind to receptors
  3. Channel opens
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23
Q

Anchored proteins (glycosyl-phosphatidylinositol (GPI)) do not _____

functions:

A

cross the bilayer

  • receptors
  • enzymes

located on the E side

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24
Q

Alkaline phosphate is a

A

GPI-linked protein

–In osteoblast membranes (bone forming cells)

–Increases the local concentration of free phosphate

→ calcium phosphate in bone

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25
Q

What is the function of proteins covalently bound to lipid

A

receptor-related signaling

ex. , G-coupled receptor protein and its GTP coupled binding protein receptor is always on the C side

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26
Q

____ and ____ are lipid-linked signalling proteins that stimulate cell proliferation

A

Src and Ras

–Ras is a GTP-binding protein

–Src is a tyrosine kinase

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27
Q

Function of proteins bound to the membrane by ionic bonds (peripheral membrane proteins)

A

bind other structures to the cell membrane on both E and C sides

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28
Q

anchors actin filaments in skeletal muscle cells to a complex of proteins in the muscle cell membrane

A

Dystrophin

This protein is defective in Duchenne’s Muscular Dystrophy

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29
Q

prevent movement between adjacent cells forcing apical to basal membrane diffusion

A

tight junctions

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30
Q

the CHO layer on the outer surface of the plasma membrane

A

the glycocalyx

Attached to lipids and proteins

Always on the E side

Glycocalyx is on the outer surface gives cells a fuzzy appearance

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31
Q

Membrane carbohydrate occurs as glycolipid or glycoprotein and functions include:

A

–protects proteins from proteolysis

–cell adhesion

–cell recognition (ABO blood groups are GLs)

Cholera toxin and HIV -1 both recognize and bind to specific glycolipids on intestinal epithelial cells. This facilitates their entry into the cells

32
Q

Plasma membranes (are/are not) homogeneous

A

not homogeneous

33
Q

Some rafts are invaginated to form ______

A

caveolae

The protein caveolin help them form their characteristic flask-like shape

34
Q

Many signaling molecules and receptors are concentrated in

Selective affinity for:

A

lipid rafts and caveolae

Selective affinity for:

  • Ras and Src proteins
  • GPI anchored proteins

Insulin receptors are localized to lipid rafts and caveolae

35
Q

Membrane Transport: Passive Processes

A
  • Simple diffusion
  • Carrier-mediated facilitated diffusion
  • Channel-mediated facilitated diffusion
  • Osmosis
36
Q

movement of solute particles “down” its concentration gradient (High to Low)

A

simple diffusion

37
Q

movement of H2O “down” its concentration gradient (from high water concentration to low water concentration area).

Water diffuses through plasma membranes two ways:

A

Osmosis

  1. Through the lipid bilayer
  2. Through water channels called aquaporins (AQPs)
38
Q

Fick’s Law of Diffusion

A

Rate of diffusion ~ surface area x concentration gradient x membrane permeability/ membrane thickness

membrane permeability~ lipid solubility/molecular size

39
Q

Facilitated Diffusion Using Channel Proteins

Two types:

A

​Aqueous channels formed by transmembrane proteins selectively transport ions or water

  • Leakage channels
    • Always open
  • Gated channels
    • Controlled by chemical or electrical signals

selected on basis of size and charge

40
Q

The measure of total concentration of solute particles

A

osmolarity

•When solutions of different osmolarity are separated by a membrane, osmosis occurs until equilibrium is reached

41
Q

The ability of a solution to cause a cell to shrink or swell

A

tonicity

42
Q

A solution with the same solute concentration as that of the cytosol

A

Isotonic

43
Q

A solution having greater solute concentration than that of the cytosol

A

hypertonic

44
Q

A solution having lesser solute concentration than that of the cytosol

A

hypotonic

45
Q

Examples of Isotonic Solutions:

A

0.9% Saline (0.9 g NaCl/100mL H20 solution) and 5% Glucose (5g glucose/100mL H20 solution)

46
Q

Requires carrier proteins (solute pumps) and moves solutes against concentration gradient

A

Active transport

•Types of active transport:

–Primary active transport

–Secondary active transport

47
Q

Energy from hydrolysis of ATP causes shape change in transport protein so that bound solutes (ions) are “pumped” across the membrane

A

Primary Active Transport

48
Q
A
49
Q
  • Depends on an ion gradient created by primary active transport
  • Energy stored in ionic gradients is used indirectly to drive transport of other solutes
A

Secondary Active Transport

cotransport: uses symport and antiport systems

50
Q

Mitochondria Membrane Structure

A
51
Q

Membrane

A
52
Q

E-face:

P-face:

A

E-face: backed by extracellular space

P-face: backed by protoplasm

53
Q

Mobility of membrane lipids

A

PLs and GLs can move in the plane of the membrane, but “flip-flops” are rare

(unless scramblases are present)

54
Q

Notch

A
  • Notch and its ligand both are single pass transmembrane proteins
  • Notch is on cell 1—external part is cleaved and bound to notch ligand
  • Ligand is on cell 2– Bound Notch is internalized
55
Q
A
56
Q

Glycocalyx Functions:

A
  • Cell recognition
  • Enzymatic activity
  • Contain receptors for antibodies, hormones, bacteria, and viruses
57
Q

are microdomains within the plasma membrane enriched (2X) in cholesterol and sphingolipids. These may be flat or form pockets (caveolae)

A

Lipid rafts

Membrane proteins involved in signal transduction into the cell concentrate in these rafts

58
Q

Methods of Membrane Transport

A
  1. Simple Diffusion
    1. Through Lipid Bilayer
    2. Osmosis
  2. Carrier-Mediated Transport
    1. Facilitated Diffusion
    2. Primany Active Transport
    3. Seconday Active Transport
  3. Vesicular Transport
    1. Endocytosis
    2. Exocytosis
59
Q

Membrane Transport

A
60
Q

Acts as a selectivly permeable barrier. Substances move across it by passive processes, which depend on the kinetic energy of molecules, and by active processes, which depend on the use of cellular energy (ATP)

A

The plasma membrane

61
Q
A
62
Q

Factors affecting rate of diffusion through a cell membrane:

A
  • Lipid solubility
  • Molecular size
  • Cell membrane thickness
  • Concentration gradient
  • Membrane surface area
  • Composition of lipid layer
63
Q
A
64
Q

Passive Membrane Transport: Facilitated Diffusion

Certain lipophobic molecules (e.g., glucose, amino acids, and ions) use carrier proteins or channel proteins, both of which:

A
  • exhibit specificity (selectivity)
  • are saturable, i.e., rate is determined by number of carriers or channels
  • can be regulated in terms of activity and quantity
65
Q

Facilitated Diffusion Using Carrier Proteins:

A
  • Transmembrane integral proteins transport specific polar molecules (e.g., sugars and amino acids)
  • Binding of substrate causes shape change in carrier
66
Q

Glucose diffusion

A
67
Q
A
68
Q

Tonicity

A
69
Q

Hypertonic solutions are sometimes infused intravenously into the bloodstream of _________ patients to draw excess water our of the extracellular space and move it into the bloodstream so that it can be eliminated by the kidneys

Hypotonic solutions may be used to _________tissues of patients.

A

edematous; rehydrate

70
Q

Active Transport

A
71
Q

Operational Model of Ca+ ATPase

A
72
Q

Sodium-potassium pump (Na+ -K+ ATPase)

A

Primary Active Transport

  • Located in all plasma membranes
  • Involved in primary and secondary active transport of nutrients and ions
  • Maintains electrochemical gradients essential for functions of muscle and nerve tissues
73
Q

Operatinal Model of the Na/K ATPase in the Plasma Membrane

A
74
Q

Examples of Secondary Active Transporters

A
75
Q

Operational Model of the Na<span>+</span> / Glucose Symporter

A
76
Q

Epithelial Transport

A

A. A cotransport carrier at the luminal border simultaneously transfers glucose against a concentration gradient and Na down a concentration gradient from the lumen into the cell.

B. No energy is directly used by the cotransport carrier to move glucose uphill. Instead, operation of the cotransport carrier is driven by the Na concentration gradient (low Na in ICF compared to lumen) established by the energy-using Na-K pump.

C. The Na-K pump actively transports Na out of the cell at the basolateral border, keeping the ICF Na concentration lower than the luminal concentration.

D. After entering the cell by secondary active transport, glucose is transported down its concentration gradient from the cell into the blood by facilitated diffusion, mediated by a passive glucose carrier at the basal border.

E. The Na-K pump also actively transports K into the cell, maintaining a high intracellular K concentration, but this action has no influence on secondary active transport.

M1 (48 decks)

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