1. Epithelial cells Flashcards by Georgia Leggett

Where are ribosomes found and what do they do there?

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.

How well did you know this?

Not at all

Perfectly

What is the function of nuclear pores?

control import and export of macromolecules into and out of nucleus

How well did you know this?

Not at all

Perfectly

What is the relationship between nuclear envelope and endoplasmic reticulum?

There is physical continuity between nuclear envelope and ER

How well did you know this?

Not at all

Perfectly

Describe the rough endoplasmic reticulum

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

How well did you know this?

Not at all

Perfectly

What is the RER the site of?

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

How well did you know this?

Not at all

Perfectly

What is the function of the smooth endoplasmic reticulum?

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

How well did you know this?

Not at all

Perfectly

What is the Golgi apparatus and what does it do?

System of stacked, membrane bound, flattened sacs

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

How well did you know this?

Not at all

Perfectly

How is are the faces of the Golgi apparatus aligned?

Cis: to ER
Trans: to cell periphery

How well did you know this?

Not at all

Perfectly

What are peroxisomes?

Single membrane bound organelles

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

How well did you know this?

Not at all

Perfectly

What is the cytoskeleton?

A system of filaments formed by the polymerisation of protein monomers

How well did you know this?

Not at all

Perfectly

What 3 types of filament constitute the cytoskeleton?

Microtubules
Intermediate Filaments
Microfilaments

How well did you know this?

Not at all

Perfectly

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

Polymers of alpha and beta tubulin heterodimers

20nm thick

How well did you know this?

Not at all

Perfectly

What are microtubules used for?

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

How well did you know this?

Not at all

Perfectly

What are microtubules major components of?

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

How well did you know this?

Not at all

Perfectly

Describe the organisation of microtubules in cells.

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

How well did you know this?

Not at all

Perfectly

Describe structure of intermediate filaments

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

How well did you know this?

Not at all

Perfectly

Which component of the cytoskeleton distinguishes different cell types?

Intermediate Filaments are different for different cell types

How well did you know this?

Not at all

Perfectly

What is the function of intermediate filaments?

Give mechanical strength to cells

How well did you know this?

Not at all

Perfectly

What are desmosome cell-cell adhesions connected by?

Intermediate Filaments

How well did you know this?

Not at all

Perfectly

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

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

How well did you know this?

Not at all

Perfectly

What are microfilaments made of and what is their diameter?

Polymers of Actin (filamentous actin, F-actin)

5-9nm diameter

How well did you know this?

Not at all

Perfectly

What do microfilaments associate with?

Adhesion belts in epithelia and endothelia

What are microfilaments involved in?

cell shape and movement

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

What is the monomer of microfilaments?

G-actin (globular actin)

How is the cytoskeleton dynamic?

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

What are the 5 major groups of cell type?

``` Connective tissue Contractile tissue Haematopoietic Neural Epithelial ```

Give 3 examples of connective tissue cells

Fibroblasts Chrondocytes Osteocytes

Give 3 examples of contractile tissue cells

Skeletal muscle Cardiac muscle Smooth muscle

Give 3 examples of haematopoietic cells

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

Give 2 examples of neural cells

Neurones | Glial cells

What are epithelial cells?

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

What do tumours retain?

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

What is a tissue?

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

Define 'Extracellular Matrix'.

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

Epithelial organisation

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

List 4 functions of epithelial layers

Transport Absorption Secretion Protection

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

Cell-cell junctions | Give epithelia mechanical integrity and act to seal intercellular pathway of layer

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

Zonulae (Belts) | Maculae (Spots)

How are cell-cell junctions typically arranged in epithelia?

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

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

Tight Adhesion belt Desmosomes/Gap Junctions

What is the role of tight junctions?

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

Describe tight junctions

``` 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 ```

Describe the structure and function of the adhesion belt.

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

What are transmembrane adhesion molecules?

Cadherins | Family of Ca 2+ dependent cell adhesion molecule s

What do cadherins associate with?

Actin

Describe the structure and function of desmosomes.

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

What are desmosomes linked to?

Intermediate filament cytoskeleton

Describe the structure of gap junctions

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

What is the role of Gap junctions?

Allows transport of ions and small molecules between cells

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

pH Ca 2+ conc Voltage Some signalling molecules

What are gap junctions also known as?

Electrical synapse | Important in passage of electrical signals in some tissues

Chemical synapse

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

Why are cell-cel junctions described as labile?

They're capable of changing their assembly and organisation