cell ultrastructure and cytoskeleton Flashcards
2 major classes of organisms
prokaryotes (bacteria / archea)
eukaryotes
Prokaryotes
NO nucleus with nuclear envelopme membrane or bound organelles or histones
circular DNA
Flagella lack axoneme
cell wall
Eukaryotes
CONTAINS nucleus with nuclear envelope and membrane bound organelles
histones complexed with DNA (DNA wraps around to form packed histones)
DNA organized into chromosomes
Flagella axoneme present
Cell wall absent in animals present in plants and fungi
Protoplasm
70-85% water ; electrolytes proteins lipids carbohydrates
Cytoplasm
semi liquid contents between cell membrane and nuclear membrane surround organelles
Nucleoplasm
within the nucleus
Nucleus
Contains DNA
20% of nuclear mass
Nuclear envelope
separates nucleoplasm from cytoplasm
highly regulated membrane barrier
Contains: DNA nucleoproteins ribonucleic acid (RNA)
Nuclear envelope has how many layers
2
inner and outer nuclear membrane
separated by perinucler cistern
Outer membrane of nuclear envelope
double layered lipid membrane studded with ribosomes participating in protein synthesis
tends to be continuous with rER in many places
Inner membrane of nuclear envelope
lipid bilayer that separates the perinuclear space from nucleoplasm
connect to outer membrane by pores
associated with network of lamin filaments for support called nuclear lamina
Lamins
major architectural proteins of the animal cell nucleus
Nuclear pore complex
inner and outer nuclear membranes connected by nuclear pore complex 70-80 nm in diameter
mediated transport of all macromolecules between the nucleus and the cytoplasm
Nucleoproteins (3)
Histones
Nucleosomes
non-histones
Histones
most of DNA associated protein in eukaryotes
organizing and packaging DNA of a cell nucleus into structural units known as nucelosomes
nucleosomes
segments of DNA wrap around several histones
regulate DNA activity
NON histones
additional category of nucleoproteins PROTAMINE
could also be involved in gene activity
Nucleolus
site of ribosomal RNA synthesis and ribosomal assembly
nucleolus forms around
specific chromosomal regions called nucleolar organizing regions
Chromosomes
DNA complexed with nucleoproteins to form chromatin
chromatin packaged into chromosomes
gene
individual chromosomes contain genes or segments of DNA coding for particular traits
Alleles
different forms for the same gene
in most eurkaryotic cells chromosomes
exist as homologous pairs
diploid
2n = 46
haploid
n = 23 found in eggs and sperm
Karyotyping
sorting of chromosome pairs according to size and shape
Mosaicism
cells within one individual have different genetic makeup
Chimeras
multiple cell lines (geneotypes) with different set of chromosomes in a single individual
Heterochromatin
electron dense darkly staining inactive DNA and nucleoproteins
Barr body
permanently inactive DNA
represents degenerate X chromosome only 1 of the pair is active
Euchromatin
dispersed DNA active in transcription (RNA synthesis)
most chromatin in nucleus is
inactive heterochromatin
lamp brush chromosomes
active portions of unraveled chromosomes
Ribosomes
2 subunits 40S and 60S
synthesized and assembled in nucleolus
Ribosomes are found in
free in cytoplasm
attached to rER
nuclear membrane
polyribosomes or polysomes
aggregates of ribosomes and mRNA
frequently attach to ER -> rER
Endoplasmic Reticulum
network or reticulum of tiny tubular structure scattered in the cytoplasm
ER divides intracellularspace into
2 distinct compartments
luminal = inside ER
extra luminal = cytoplasm outside compartments
Rough ER
is frequently observed in the cells actively involved in protein synthesis and secretion
smooth ER
is the major site for synthesis of lipid
in animal cells lipid like steroidal hormones are synthesized in sER
functions in synthesis of cholesterol and steroid hormones and is principle organelle involved in detoxification and conjugation of drugs and toxins
Coated vesicles (COPI/II)
surround and coat proteins for transport bud off sER transport proteins between sER and Golgi and between golgi and cell surface
Golgi Apparatus
functions in post translational modification packaging and sorting of proteins synthesized in rER
ex. sulfation phosphorylation glycosylation
Faces of the Golgi Apparatus
Cis (convex) golgi network = forming face -> proteins arrive from rER coated in transfer vesicles
Trans (concave) Golgi network = maturing face -> proteins packaged into clathrin coated vesicle for secretion
Cis face is
closest to the rER ; convex
Trans face is
were things leave the golgi ; concave
Fates of things leaving the golgi apparatus
condensing vacuoles - vesicles bud off trans face
secretory vesicles - for extracellular export via exocytosis
membrane bound vesicles - for intracellular use
secretory granules - long term storage
Membrane trafficking
during exocytosis and secretion large amounts of intracellular membrane incorporated into outer cell membrane recycled by golgi
Lysosomes
breaks things down
membrane bound vesicles containing hydrolytic enzymes
ex. acid phosphatase
responsible for digestion of macromolecules old cell parts and microorganisms
1’ lysosomes
newly formed lysosomes produced by rER and golgi
inactive
2’ lysosome
secondary lysosomes -> 1’ lysosomes fuse with phagocytic vesicles or phagosomes and become active
function in intracellular digestion
3’ lysosome
hydrolytic breakdown results in production of 3’ lysosomes AKA residual body
may be excreted or remain in cells for life ex. lipfuscin pigment granules in neurons
what are lysosomes also used for?
to degrade organelles and cells with finite life spans during apoptosis
Apoptosis / autophagy
programmed cell death
Endosomes
primarily intracellular sorting organelles
regulate trafficking of proteins and lipids among other subcellular compartments of the secretory and endocytic pathway
peroxisomes
membrane bound organelles containing oxidative enzymes
resemble lysosomes and contain catalase and peroxidase
catalase and peroxidase
carry out oxidation reactions that break down fatty acids and amino acids
what do peroxisomes use to oxidize toxic metabolites
enzymes
free radicals
hydrogen peroxide
*alcohol is detoxified by peroxisomes in liver cells
mitochondria
produce energy via Kreb’s cycle and oxidative phosphorylation
vary greatly in size / shape / and amount within cell
move freely in cytosol
present in all cells EXCEPT red blood cells and keratinocytes
keratinocyte
outer layer of skin
Mitochondrial matrix
inner cavity filled with amorphous matrix material
contains dense granules thought to be storage sites for Ca2+
Mitochondrial DNA
circular DNA
self replicating - reproduce by binary fission
maternally inherited
mitochondrial eve
most recent common ancestor (MRCA) of all living humans
cells depend on energy derived from
cellular respiration
cellular respiration begins in
cytosol
where glucose converted to pyruvic acid
anaerobic glycolysis occurs in
cytoplasm
pyruvic acid diffused into
mitochondria
site of aerobic respiration
*mitochondrial matrix contains enzymes of krebs cycle
How is the most ATP produced
oxidative phosphorylation by cytochromes of electron transport system
where are cytochromes located
they are enzymes on inner membrane of cristae
aerobic respiration (krebs cycle and oxidative phosphorylation) occur where
within mitochondria
requires O2
anaerobic respiration occurs
in cytoplasm
NO O2
inclusions
various nutrients or pigments that can be found within the cells but DO NOT have activity like other organelles
ex. glycogen
lipids
pigments -> melanin lipofucin
intracytoplasmic pigments
lipofuscin - gold brown granules ; seen in neurons ; “old age” pigment
melanin - black brown granular pigment ; produced by melanocytes and transported to other cells
what protein is most commonly associated with the inner nuclear membrane?
lamina
