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The Dynamic Cell > ECM/epithelium/membrane transport > Flashcards

ECM/epithelium/membrane transport Flashcards

1
Q

What is the ECM

A

which assemble into a 3 dimensional extracellular structure with structural, and often other, functions

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2
Q

How is the ECM structurally complex

A

fibrous framework embedded in a gel-like background matrix

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3
Q

Structure of the plant ECM

A

Polysaccharide fibres (cellulose, hemicellulose + proteins) embedded in a gel of highly negative charged pectin polymers. Cellulose cross linked by thin hemicellulose fibres.

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4
Q

Structure of the animal ECM

A

fibrous protein fibres (e.g. collagens) embedded in matrix of highly charged glycosaminoglycans

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5
Q

Specialised ECM example in plants

A

cell wall

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6
Q

What does the cell wall prvide

A

ridgity and strength

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7
Q

What does the cell wall work in association with

A

turgor pressure from it’s cell osmosis draws water in; cell wall resists this and becomes stretched in the process –has high tensile strength Analogy with tyre – useless without pressure from inside

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8
Q

Cell wall 3 structures

A

middle lamella, primary cell wall, secondary cell wall

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9
Q

Middle lamella

A

first component secreted after cell division, glues cell together, allows plasmodesmata to form

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10
Q

when is the primary and secondary cell wall synthesised

A

primary - synthesised second
secondary - last but only after cell wall no longer divide

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11
Q

ECM composition - what is the middle lamella

A

uniform and continuous layer between adjacent cell walls

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12
Q

ECM composition - what is the middle lamella made from

A

Mostly pectcic acid, some pectin: polysaccharides (polymer of about 100 galactouronic acid molecules. Highly charged and hydrated, forms gel with Ca2+ and Mg2+

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13
Q

First cell wall effect on the middle lamella

A

pushes the middle lamella away from the plasma membrane

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14
Q

Properties of the primary cell wall

A

expandable, to allow for cell growth and semi permeable; nutrition and respiration

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15
Q

components of the cell wall

A

cellulose, hemicellulose and pectin

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16
Q

cellulose in the primary cell wall

A

straight chain glucose polymer; polymer chains held together with hydrogen bonds to form larger assemblies, fibrils and fibres. Form on the outside of the plasma membrane and arranged in to highly ordered structure

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17
Q

Hemicellulose in the primary cell wall

A

made of many different sugar monomers, branching chains. Cross-link cellulose fibrils together, increasing tensile strength of the wall

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18
Q

Pectin in the primary cell wall

A

gel contains fibres and gives compression resistance to wall

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19
Q

Small quantity proteins in the cell wall

A

some alter mechanical properties of wall structure e.g. stretching in cell growt. Other enzymes – formation, remodelling, breakdown of wall components – fruit ripening, leaf fall etc…

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20
Q

Where does the secondary cell wall form

A

between plasma membrane and primary cell wall

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21
Q

What is the secondary cell wall made from

A

Mostly fibres – cellulose, lignin (wood), pectins not always present, no proteins

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22
Q

Thickness of the secondary cell wall

A

very thick - gives the region of the plant very high tensile and compressive strength

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23
Q

Animal ECM - fibrous component

A

collagen and/or elastic fibres

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24
Q

Ground substances of the animal ECM

A

glycosaminoglycans (polysaccharides), proetoglycans, glycoproteins

Fibres: stretch resistance and elastic recoil

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25
Q

Function of the ground substance

A

hold water, jelly

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26
Q

what does the ECM do the job of

A

connective tissue

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27
Q

What can prevent spread of infection

A

compression resistance

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28
Q

type 1 collagen

A

the single most common protein in the body – most connective tissues

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29
Q

Type II collagen

A

cartilage

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30
Q

Type III collagen

A

prominent in embryonic tissues. Also repairs tissues, some specific distributions in adults as well

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31
Q

Type IV collagen

A

basal lamina

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32
Q

What do the individual gene products (alpha chain) form - collagen

A

assemble in threes to form tropocollagen

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33
Q

What does tropocollagen assemble into

A

fibrils – laterally but in quarter – stagger arrangement to make long structures, with a clear banding pattern

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34
Q

What do fibrils form

A

Fibrils associate to form fibres – typical of types 1,2 and 3 collagens

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35
Q

How is type 4 collagen formed

A

subunits assemble into planar sheets sit beneath epithelia, endothelia and on muscle cell surfaces

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36
Q

properties of collagen

A

Has high tensile strength and little stretch

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37
Q

Gene products that from collagen

A

Gene product: alpha chains (x3) -> tropocollagen -> fibril formation -> banding pattern

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38
Q

What does type 4 collagen form that the others don’t

A

Type IV collagen forms mats, not fibres. All basement membranes.

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39
Q

What is elastin made from

A

Made from tropoelastin protein subunits, and the glycoprotein fibrillin.

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40
Q

What is ehler danloss syndrome

A

mutation in type I collagen. Elastin works but collagen doesn’t causing hyper elasticity of skin ligaments etc - considerable variation in extent of condition person to person.

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41
Q

What are glycosaminoglycans

A

Long unbranched polysaccharide chains.

Repeating disaccharide, some with sulphate groups: Hyaluronan, chondroitin sulphate, dermatan sulphate, keratan sulphate, heparan sulphate (sulphated GAGs)

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42
Q

What do sulphated GAGs assemble into

A

arger structures: proteoglycans

43
Q

What does hyaluronan function with

A

proteoglycans or on its own

44
Q

important characteristics of sulphated GAGs and hyaluronan

A

highly polar (charged) attract water into their molecular structure.

45
Q

Function of sulpahted GAGs and hyaluronan

A

Compression resistance and lubrication

46
Q

what does hyaluronan do which GAGs don’t

A

Gel formation, lubrication

47
Q

What do GAGs do to proteoglycans

A

draw water into structure due to charge: generate ‘swelling pressure’

48
Q

What does lots of aggrecan (GAG side chain) in cartilage do

A

provides stiffness and compression resistance

49
Q

What may be the function of the proteoglycan

A

Others may only have a dew, or indeed just one, GAG chain: may be involved in water uptake but also in interactions with collagen, cells, signalling molecules etc: e.g. decorin, biglycan, fibromodulin

50
Q

What can aggrecan associate with

A

hyaluronan to form huge macromolecular aggregates – megadaltons

51
Q

What diseases can the degradation of proteoglycans lead to

A

arthritis, intervertebral disc degeneration

52
Q

What are glycoproteins

A

Proteins with glycosilations, but not as extensive as the proteoglycans

53
Q

What is fibronectin

A

Multidomain glycoprotein: domains bind to different substrates

54
Q

Fibronectin function

A

Link cell surfaces to a wide range of other molecules and molecules to each other. Cell adhesion, migration and signalling

55
Q

Laminin structure

A

3 chains, form a cross shape binding regions to: one another, Other ECM molecules e.g. type IV collagen, proteoglycans to form planar. And to other cells (anchors cells to basal lamina)

56
Q

What is the epithelial layer

A

: completely cellular layer, avascular, sits on top of a basement membrane, usually over a vascular connective tissue

57
Q

What do epithelia control

A

the entry and exit of all materials to and from the body tissues

58
Q

Classification of epithelia - number of layers

A

1 layer - simple
more than 1 - stratified

59
Q

classification of epithelia - shape of top layer

A

squamos, cuboidal, columnar

60
Q

Structure of epithelial cell

A

cilia, basal body, columnar cell, basal cell, basement membrane

61
Q

how may epithelia not fit the classification

A

if its transitional causing it to be stretched/collapsed e.g., epithelium that lines the bladder shifts between collapsed and stretched as the bladder empties and fills

62
Q

Features of epithelium - cellularity

A

entirely cellular - separate internal and external environments. Cellular monitoring of transfer

63
Q

Features of epithelium - specialised intercellular contact

A

desmosomes, adherens junctions, tight junctions, gap junctions

64
Q

Features of epithelium - polarity

A

top surface is different to bottom surface. Top contacts external environment, whereas the bottom contacts the basement membrane and the body. May be modified – cilia, microvilli; basal striations

65
Q

Features of epithelium - basement membrane

A

2 parts. Basal lamina – form epithelium. Reticular fibres (= collagen) - from connective tissue

66
Q

Stratified epithelium function

A

Provide protection from damage, the surface cells can be lost and replaced from underneath

67
Q

Stratified squamos keratinised epithelium

A

toughest. The surface cells are filled up with keratin, lose nuclei. Tough, dead, waterproof covering.

68
Q

Stratified squamos non-keratinised epithelium

A

Second toughest. These cells are alive all the way to the surface. Inner body surfaces: oral cavity, oesophagus, vagina. Kept moist by glandular secretions.

69
Q

Stratified cuboidal columnar

A

uncommon – ducts of sweat glands lachrymal glands (same functional principle)net

70
Q

Where is simple epithelia found

A

Occur where substances must be transported across the epithelium

71
Q

Squamos cell function

A

very thin – act as filters. Lets water and ions through, hold back bigger molecules

72
Q

Columnar and cuboidal cell function

A

ole in active transport and modification of materials that pass through them – e.g. gut cells. Plenty of cell ‘machinery’ - mitochondria, lysosomes and golgi etc.

73
Q

Where are goblet cells found

A

in simple columnar pseudostratified columnar

74
Q

What is gating of ion channels

A

fluctuation between open and closed.

75
Q

How do ion channels work out what to transport

A

by measuring the intracellular and extracellular fluid

76
Q

What does the single-channel conductance of a typical ion channels range from

A

0.1 to 100 pS

77
Q

What factors control gating

A

Membrane voltage (e.g., depolaristaion), Extracellular agonists or antagonists (e.g., ligand gated), Intracellular messengers (e.g., Ca2+), Mechanical stretch of the plasma membrane (physical mechanisms)

78
Q

What are ligand-gated ion channels made from

A

3,4 or 5 protein subunits that together form an ion-conducting pore in the center of the receptor (multiple subunits)

79
Q

What does activation of receptor on ion channel cause

A

a pore to open through which ions can pass (conformational change)

80
Q

What does metabotropic receptor activation initiate

A

an intracellular signaling mechanism (ions do not pass through the receptor protein) - allows another channel to open

81
Q

Example of metabotropic receptor

A

adrenergic receptors of the autonomic nervous system (e.g., beta-adrenergic receptors in heart)

82
Q

Speed of response from metabotropic receptor

A

a slower prolonged response compared to a metabotropic receptor

83
Q

What type of receptor is a metabotropic receptor

A

A G-protein coupled receptor

84
Q

Metabotropic receptor response to signals

A

Can amplify or dampen signals: Gs – stimulatory. Gi – inhibitory

85
Q

Intracellular and extracellular fluids of the cell membrane

A

primarily water (in which solutes such as ions, glucose and amino acids are dissolved).

86
Q

Which substances can diffuse across the bilayer

A

Gases (e.g., O2 and CO2) and ethanol

87
Q

What are water channels called

A

aquaporins

87
Q

What are water channels called

A

aquaporins

87
Q

What are water channels called

A

aquaporins

88
Q

Where are there large number of aquapor5ins

A

in the kidney - to regulate how dilute the urine is

89
Q

How is water influx/efflux regulated

A

by altering number of AQPs in the membrane (membrane protein trafficking) - changing their permeability

90
Q

What do uniporters do

A

transport one substance

91
Q

what do symporters do

A

transport more than one substance in the same direction (co-transpor)

92
Q

What do antiporters do

A

transport substances in different directions

93
Q

Uniporters example

A

GLUT2 (brings glucose into the cell0. Mutation can cause diabetes as ability to transport glucose is affected.

94
Q

Symporter example

A

NKCC2 found in the kidneys. 1Na+, 1K+, 2Cl- symporter. Critically important for diluting and concentrating urine.

95
Q

Antiporter example

A

Na+, H+ antiporter. Found in all cells. Important in regulating intracellular pH

96
Q

ATP dependent ion transporter example

A

Na+, K+ ATPase (also called the Na+K+ pump)

97
Q

ATP dependent ion transporter structure

A

Three subunits (alpha, beta and gamma). Alpha subunit has binding sites for: NA+, K+, ATP and Ouabain (inhibitory – used to treat hypotension)

98
Q

Where is vacuolar H+-ATPase found

A

in membranes of many intracellular organelles (e.g., lysosomes)

99
Q

Plasma membrane H+-ATPase importance

A

has a role in urinary acidification

100
Q

Example of ATP-binding cassette (ABC) transporters

A

e.g., cystic fibrosis transmembrane regulator (CFTR) - affects Cl- transporting

101
Q

What is primary active transport

A

transport is directly couples to ATP hydrolysis (to move substances against their concentration gradient)

102
Q

What is secondary active transport

A

energy for the transport comes from the electrochemical gradient. The energy from one molecule is used to move another molecule(s) against its electrochemical gradient e.g., 3NA+-Ca2+ antiporter.

The Dynamic Cell (8 decks)

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