what is the function of organelles?
preform metabolic and synthetic, energy requiring and generating, functions in a cell
what are inclusions?
products of organelles
have no active role in metabolism
what is the cytoplasmic matrix made up of?
soluble proteins and enzymes involved in glycolysis
what are the membranous organelles of the cell?
Rough and smooth ER
golgi apparatus
lysosomes
peroxisomes
mitochondria
what are the non-membranous organelles of the cell?
ribosomes
microtubules
actin filaments
intermediate filaments
centrioles
basal bodies
what are the inclusions of the cell?
secretory vesicles
pigment granules
neutral fat
lipid droplets
glycogen
stored waste product
what do ribosomes look like under light microscope?
not visible
basophilic appearance (dark blue/purple) due to the phosphate groups in RNA
what do ribosomes look like under transmission electron microscope?
visible
appear electron dense because they absorb electrons
what are polyribosomes?
ribosomes clumped together with mRNA and attached to the ER
what produces ribosomes?
rough ER and nucleolus
what are ribosomes composed of?
2 subunits with 4 types of rRNA in the nucleus and 80 proteins in the cytoplasm
where is RNA synthesized?
in the nucleus
where do synthesized proteins go?
proteins go from the place of synthesis, cytoplasm, to the nucleus to be attached to rRNA
how do subunits go to cytoplasm?
through nuclear pores
what is the function of ribosomes?
they are the site where amino acid molecules are incorporated into protein molecules
what is the rough endoplasmic reticulum?
a network of channels formed by continuous membranes extending to nuclear envelope
where is the rough ER abundant?
in cells specialized with protein secretion (basophilic cells)
explain this picture
proteins are made by the ribosomes on the surface of ER
they are then transported into the interior to be modified
proteins accumulate in vesicles
vesicles bud off the surface of ER and are transported to GA
what is the smooth endoplasmic reticulum?
extension of the rough ER which forms networks if membranous tubules
what is the function of smooth endoplasmic reticulum?
transfer proteins to golgi
what is the smooth ER abundant?
liver cells (detoxifying enzymes)
muscle cells (break down glycogen)
cells that produce glycogen, lipids or steroids
explain this picture
plasma cells which have a lot of rough ER
explain this picture
leydig cells found in the reproductive system and have a lot of smooth ER
what is the golgi apparatus?
3 - 20 flattened polarized cisternae (membrane sacs)
which face of GA is mature?
the trans face which is concave
which face of GA is immature?
the cis face which is convex
label the picture
1- vesicles that have bud off 2- trans golgi 3- mid golgi 4- cis golgi 5- smooth ER 6- rough ER 7- nucleus
in what direction do proteins travel through the GA?
from cis to trans
functions of GA
modify proteins by cutting or adding
removal of amino acids
glycosylation, sulfating and phosphorylations
packing vesicles
sorting and distributing proteins
repair cell membrane
formation of lysosomes
what are lysosomes?
intracellular digestive organelles
DOUBLE membrane
surround hydrolytic enzymes formed in GA
what do lysosomes look like under EM?
electron dense granules
take on basophilic colour because lysosomal enzymes work under an acidic environment
what are the functions of lysosomes?
autophagy (digestion of old organelles)
autolysis (destruction of own cell)
digesting materials taken by endocytosis
explain this picture
lysosomal enzymes are secreted in the rough ER and transported to golgi
in the golgi these enzymes are modified (attaching mannose-6-phosphate) and packaged
lysosome is then formed in the golgi and contains all the hydrolytic enzymes
a primary lysosome is released
what is on the surface of lysosomal enzymes?
mannose-6-phosphate
what is a primary lysosome?
pure lysosome freshly bud off of GA
contains inactive digestive enzymes
cannot undergo digestion
can't eliminate content
what is a secondary lysosome?
fusion of primary lysosome and endosome
contains active digestive enzymes
undergoes digestion
can eliminate content
what are indigestible materials known as?
residual bodies
where do residual bodies accumulate?
heart cells, muscle cells and neurons
form intracellular pigments such as lipofuscin or age pigment
where are peroxisomes found?
liver
what are peroxisomes?
single membrane-bound
self-replicating
formed in the ER
associated with free ribosomes
function of peroxisomes
detoxification of H2O2 to produce water and oxygen
structure of mitochondria
outer membrane (limits organelles)
inner membrane (folded to form cristae)
matrix
how does the outer membrane prevent diffusion of contents of the mitochondrial matrix?
passive diffusion
how does the inner membrane prevent diffusion of contents of the mitochondrial matrix?
active transport
what does the mitochondrial matrix consist of?
electron dense granules which represent the binding sites of calcium ions and krebs cycle enzymes
why is the mitochondria self-replicating?
the matrix contains DNA, RNA and ribosomes
what is the cytoskeleton?
dynamic 3D structure that fills the the cytoplasm
cytoskeleton function
important for movement and stability of the cell
what are the primary fibers of the cytoskeleton
microfilaments
microtubules
intermediate filaments
what are microfilaments?
fine filled protein fibers
composed predominantly of f-actin (thin)
contains myosin
what are microtubules?
cylindrical hollow tubes
composed of 13 subunits of tubulin arranged in a polarized ring
subunits are termed alpha and beta
how do microtubules grow?
via subunit polymerization
grow from the +ve end
under control of Ca2+ and MAP
how do microtubules help build other organelles?
they act as scaffolding by providing tracks for them to move on
what organelles do microtubules help build?
cilia
flagella
centrioles (used in cell division)
spindle fibers
transport by microtubules
motor proteins like kinesin move along microtubules
powered by ATP
transports cellular cargo
transport is from the center of the cell to the periphery
what are intermediate filaments?
provide tensile strength
present in keratins (epithelium), desmin (muscle) and neurofilaments (neurons)
where are all 3 fibers found?
cytoskeleton of epithelial cells in the intestine
what are centrioles?
rod organelles
found in pairs
9 sets of 3 microtubules
what is this?
inclusions of glycogen in liver cells
what is this?
inclusions of secretory vesicles in pancreatic cells
how do lipid droplets look like under LM?
do not stain
extracted by organic solvents
appear to by empty
how do lipid droplets look like under EM?
stain electron dense by osmium tetroxide
not delaminated by phospholipid monolayer