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Tissues > 1. Epithelial cells > Flashcards

1. Epithelial cells Flashcards

1
Q

Where are ribosomes found and what do they do there?

A

Free in cytoplasm: synthesise cytoplasmic proteins
OR
Attached to outer membrane of nuclear envelope and ER: make membrane proteins and proteins to be packaged in membranous organelles.

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2
Q

What is the function of nuclear pores?

A

control import and export of macromolecules into and out of nucleus

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3
Q

What is the relationship between nuclear envelope and endoplasmic reticulum?

A

There is physical continuity between nuclear envelope and ER

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4
Q

Describe the rough endoplasmic reticulum

A

Stacks of flattened membrane leaflets (cisternae), studded on outer face with ribosomes

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5
Q

What is the RER the site of?

A

protein synthesis and packaging in membrane-bound structures, e.g. secretory vesicles, lysosomes

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6
Q

What is the function of the smooth endoplasmic reticulum?

A

Detoxification
Lipid metabolism
Enzymes involved are typically associated with the membranes.
Site of Ca2+ storage in cells (important in cell-signalling)

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7
Q

What is the Golgi apparatus and what does it do?

A

System of stacked, membrane bound, flattened sacs

Modifies, sorts and packages macromolecules for secretion/ delivery to other organelles

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8
Q

How is are the faces of the Golgi apparatus aligned?

A

Cis: to ER
Trans: to cell periphery

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9
Q

What are peroxisomes?

A

Single membrane bound organelles

Contain enzymes involved in lipid and oxygen metabolism, e.g. oxidases, catalases, peroxidases

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10
Q

What is the cytoskeleton?

A

A system of filaments formed by the polymerisation of protein monomers

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11
Q

What 3 types of filament constitute the cytoskeleton?

A

Microtubules
Intermediate Filaments
Microfilaments

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12
Q

What are microtubules made of and what is the diameter of a microtubule?

A

Polymers of alpha and beta tubulin heterodimers

20nm thick

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13
Q

What are microtubules used for?

A

Movement of organelles through the cell
Involve motor proteins
Involved in spindle fibre formation

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14
Q

What are microtubules major components of?

A

Cilia and flagellae
Form 9 + 2 arrangement in the core
(9 doublets + 2 central singlets)

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15
Q

Describe the organisation of microtubules in cells.

A

Originate from a point within the cell called the microtubule organising centre (MTOC)

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16
Q

Describe structure of intermediate filaments

A

Group of polymers of filamentous proteins
Form rope-like filaments
10-15nm diameter

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17
Q

Which component of the cytoskeleton distinguishes different cell types?

A

Intermediate Filaments are different for different cell types

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18
Q

What is the function of intermediate filaments?

A

Give mechanical strength to cells

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19
Q

What are desmosome cell-cell adhesions connected by?

A

Intermediate Filaments

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20
Q

Where else are intermediate filaments found other than in the cytoplasm?

A

Nuclear lamins are IF’s found on the internal surface of the nuclear envelope
Provide support

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21
Q

What are microfilaments made of and what is their diameter?

A

Polymers of Actin (filamentous actin, F-actin)

5-9nm diameter

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22
Q

What do microfilaments associate with?

A

Adhesion belts in epithelia and endothelia

23
Q

What are microfilaments involved in?

A

cell shape and movement

major component of contractile apparatus of muscle and involved in contraction of non muscle cells

24
Q

What is the monomer of microfilaments?

A

G-actin (globular actin)

25
Q

How is the cytoskeleton dynamic?

A

Various elements are subject to rapid re-modelling, stimulated by biochemical and bio-mechanical signals.

26
Q

What are the 5 major groups of cell type?

A 
Connective tissue
Contractile tissue
Haematopoietic 
Neural
Epithelial
27
Q

Give 3 examples of connective tissue cells

A

Fibroblasts
Chrondocytes
Osteocytes

28
Q

Give 3 examples of contractile tissue cells

A

Skeletal muscle
Cardiac muscle
Smooth muscle

29
Q

Give 3 examples of haematopoietic cells

A

Blood cells
Tissue-resident immune cells
Cells of the bone marrow from which they’re derived

30
Q

Give 2 examples of neural cells

A

Neurones

Glial cells

31
Q

What are epithelial cells?

A

Cells forming continuous layers, these layers line surfaces and separate tissue compartments and have various other functions

32
Q

What do tumours retain?

A

Characteristics of the cell type from which they originate
e.g.
epithelial cancers= carcinomas
neural cell cancers= neuroblastomas

33
Q

What is a tissue?

A 
A group(s) of cells whose type, organisation and architecture are integral to its function
Composed of cells, extracellular matrix and fluid
34
Q

Define ‘Extracellular Matrix’.

A

The insoluble material deposited by cells found extracellularly.
Composed of fibrillar/ reticular proteins embedded in hydrated gel

35
Q

Epithelial organisation

A

Epithelial cells make organised, stable cell-cell junctions to form continuous, cohesive layers
Epithelial layers line internal and external body surfaces

36
Q

List 4 functions of epithelial layers

A

Transport
Absorption
Secretion
Protection

37
Q

What are key to the formation and maintenance of epithelial layers and why?

A

Cell-cell junctions

Give epithelia mechanical integrity and act to seal intercellular pathway of layer

38
Q

What are the 2 forms cell-cell junctions generally found in?

A

Zonulae (Belts)

Maculae (Spots)

39
Q

How are cell-cell junctions typically arranged in epithelia?

A

Apical junctional complex containing a tight junction nearest the apex
Then an adhesion belt
Then scattered throughout the lateral membrane, desmosomes (spot adhering junctions)

40
Q

What are the 4 main types of cell-cell junctions (in order of apical to basal)?

A

Tight
Adhesion belt
Desmosomes/Gap Junctions

41
Q

What is the role of tight junctions?

A

Seals off the paracellular pathways
Allows polarity
Stops proteins that diffuse through membranes.

42
Q

Describe tight junctions

A 
Zonula occludens (Belt)
Points on adjacent membranes form close contacts at apical lateral membranes
The more elaborate the network of contacts the tighter the seal
43
Q

Describe the structure and function of the adhesion belt.

A

Zonula adherens (belt)
Usually formed just basal to apical TJ
Controls assembly of other junctions

44
Q

What are transmembrane adhesion molecules?

A

Cadherins

Family of Ca 2+ dependent cell adhesion molecule s

45
Q

What do cadherins associate with?

A

Actin

46
Q

Describe the structure and function of desmosomes.

A 
Macula adherens (spot)
Found at multiple spots between adjacent cell membranes
Involves cadherins interacting to maintain adhesion.
Provide good mechanical continuity between cells
47
Q

What are desmosomes linked to?

A

Intermediate filament cytoskeleton

48
Q

Describe the structure of gap junctions

A 
Macula communicans (spot)
Made of clusters of pores formed from 6 identical subunits in the membrane (pores continuous with pores in adjacent cell membrane)
49
Q

What is the role of Gap junctions?

A

Allows transport of ions and small molecules between cells

50
Q

What can open/ close pores in gap junctions thereby controlling intercellular communication?

A

pH
Ca 2+ conc
Voltage
Some signalling molecules

51
Q

What are gap junctions also known as?

A

Electrical synapse

Important in passage of electrical signals in some tissues

52
Q

Chemical synapse

A

Communicating junction
Mainly in neural tissue
Information passed 1-way via chemical signalling

53
Q

Why are cell-cel junctions described as labile?

A

They’re capable of changing their assembly and organisation

Tissues (11 decks)

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