Histology Flashcards
describe the structure of the plasmalemma
bimolecular layer of amphipathic phospholipid molecules with hydrophilic heads and hydrophobic tails.
what substances can diffuse across the plasmalemma
small, hydrophobic, uncharged molecules
what cannot diffuse across the plasmalemma
charged molecules
define inclusions
components synthesised by the cell itself
role of the cytoskeleton
provide structural support
three classes of filaments in the cytoskeleton
- microfilaments
- intermediate filaments
- microtubules
describe the structure of microtubules
made up of two subunits- alpha and beta tubulin
two proteins involved in microtubules
kinesin is an ATPase that moves to the cell periphery
dyne is an ATPase that moves towards the cell centre
describe the structure of the nucleus
nuclear envelope comprises of an inner and outer membrane with a perinuclear cistern. It contains chromosomes.
two types of DNA in the nucleus
- euchromatin- dispersed DNA actively undergoing transcription
- heterochromatin- condensed DNA not undergoing transcription
structure of a ribosome
small subunit (binds RNA) and large subunit (forms peptide bonds)
define polysome
cluster of ribosomes held together by RNA. Makes unpackaged proteins.
describe how ER is involved in protein synthesis
free ribosomes attach to mRNA. If ER signal peptide is present the growing peptide is inserted into the pore of ER.
functions of SER
stores, synthesises proteins and lipids
describe the structure of the Golgi apparatus
flattened, membrane-bound cisternae with vesicles.
function of the Golgi apparatus
adds sugars and sorts
structure of mitochondria
double membrane that is extensively folded to form cristae. It contains its own DNA
function of mitochondria
produce ATP
three types of intercellular junctions
- occluding (tight)
- desmosomes (anchoring)
- communicating (gap)
function of tight junctions
diffusion barrier
function of desmosomes
strength
function of gap junctions
allows movement between cells
define a junctional complex
close association of several types of junctions
three ways material can cross the cell membrane
- diffusion
- transport proteins (pumps/ channels)
- vesicular transport (endocytosis and phagocytosis)
describe endocytosis
membrane fuses to form an endocytotic vesicle
describe phagocytosis
engulfed to form a phagosome, lysosomes release lysozyme to form a phagolysosome.