Cell and Tissue Structure 3 Flashcards
what is the cytoskeleton?
what does the cytoskeleton mean regarding how rigid the cell is?
def: the network of protein structures that maintains the physical integrity of the cell and allow for transport of organelles and vesicles throughout cell.
rigidity - allows to be flexible whilst maintaining mech. support
which protein fibres is cytoskeleton made from?
- microfilaments (made from actin)
- intermediate filaments
- microtubules
describe the structure and function (3) of microfilaments
structure: made of helical structures of actin
function: - mechanical support
- allows for movement of organelles along the actin filaments
- in muscles, allow contraction together with myosin
-
give an example of disease arising from actin not being produced correctly
‘floppy babies’ - babies luck muscle strength
what are intermediate filaments used for?
function: tensile strength whilst maintain flexibilty
made from: different cell types are made from different intermediate filaments:
- e.g. skin’s intermediate filament = keratin.
what is a disease associated with keratin?
epidermolysis bulbosa - easy blistering of skin (skin cells dont have support structure of intermediate filaments)
describe structure and function (4) of microtubules :)
structure:
- large tubular structure
- hollow
- made from tubulin
Functions:
- prevent the cells from being compressed
- scaffolding on which organelles and vesicles move
- form the framework of the mitotic spindle required for cell division
- act as flagella or cilia
why can make phospholipd bilayer structure complex?
due to the various proteins that attach either to the membrane or span all / part of the membrane
what are the functions of the plasma membrane?
- protection
- communcation
- permeability
- identification
- cell adhesion
- anchor cytoskeleton
- interaction with ECM
what is the basal membrane / basal lamina?
how many layers / what layers name?
what is the basal membrane / basal lamina made from?
a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits.
separated into two layers: (collagen lies in different direction for them)
1. Lucida
2. Densa
made from type IV Collagen, Laminin and a Heparin Sulfate
what is the function of the basal lamina / basement membrane? (4)
- provides structural support for epithelia to stay on it. therefore give tissue and organ their shape
- relays functional messages through epithelia, to cells within organ
- as a messenger for growth factors
- physical barrier
- provides anchorage to the epithelia
REALLY IMPORTANT IN GIVING ORGANS AND TISSUES THEIR BASIC STRUCTURE AND INTENSITY
describe two diseases of the basal membrane
- epidermolysis bulbosa - mutations in laminin -> easily peals off and so does the skin above it
- cancer - (usually cant cross into organs because the basal membrane divides the organ from the rest of the body. but epithelial - mesenychymal transition - where does cross and becomes metastatic)
what connects cells ? (some but not all)
inter-cellular junctions
name the types of inter-cellular junctions
- tight junction
- adherens junction
- desmosome
- gap junction
- hemidesmosomes
describe the function of tight junctions
where are tight junctions usually found?
- hold cells together
- provide a physical barrier between outer and inner side of cells -> prevent bacteria, ion and molecules from crossing
found: on luminal side side of cells
which diseases result in disruption of tight junctions?
AD, Parkinsons, MS, Stroke
describe the function of adheren junctions
where are adheren junctions usually found?
what is their core made from?
explain how connect adheren junction conncet from one cell to another
function: hold tightly one cell to next. BUT: linked to actin cytoskeleton of adjacent cells. crosses membrane of both cells. also: wound healing
location: epithelia and endothelial cells. located basally than tight junctions
core: cadherin molecules, adhere tightly (w/ calcuium) and bind catenin to cytoplasm of one cell to cytoskeleton of other cell
connection: cadherin (cell 1) -> catenin (intracellular space) -> actin filamet (cell 2)
describe the function of desmosomes
where usually found?
function: attach adjacent cells together. BUT: instead of connecting actin filaments, have a plaque that connects to intermediate filaments. strong attachment.
location: tissues that are in high mechanical stress (they reduce stress on the cells). e.g cardiac cells
give a disease associated with desmosomes?
- arrhythomogenic right ventricular cardiomyopathy: (mutation in desmogelin gene) defective desmosomes -> sudden death due to hearts bursting
- Pemphigus vulgaris - autoimmune disease that attacks desmosomes -> blisters
describe function of gap junctions
what are gap junctions made from?
what is bystander effect?
junction: allow movement of substances between cytoplasm of adjecent cells. regulated passage. can make chemical and electric gradients.
made from: protein connexin - 6 connexin molecules one side connect to 6 connexin molecules on other side.
bystander effect: one cell signals apoptosis in adjacent cell without generating own signals themselves
what are pseudopodia?
how occur?
function: temporary cytoplasm-filled projection of cell membrane for movement and ingestion
movement: rearrangement of cytoskeleton (extesnion of actin, contraction of myosin)
