Cell Ultrastructure Flashcards
what are the 2 major categories of organisms?
prokaryotes and eukaryotes
Examples of prokaryotes
Monera, cyanobacteria
examples of eukaryotes
single-celled protists, protozoa and multicelled metazoans
Protoplasm
contained in cells, (~70-85% water; electrolytes, proteins, lipids, carbohydrates)
cytoplasm
semi-liquid contents between cell membrane & nuclear membrane, surrounds organelles
nucleoplasm
within nucleus
Chromosomes
DNA complexed with nucleoproteins to form chromatin
alleles
different forms of same gene
Hererochromatin
electron-dense, darkly-staining, inactive DNA & nucleoproteins
•In females, permanently inactive DNA aka Barr bod
•Represents degenerate X chromosome; only 1 of pair active, other degenerates
Euchromatin
dispersed DNA activein transcription (RNA synthesis)
Cells active in translation—within (protein synthesis in cytoplasm) will have prominent nucleolus& abundant euchromatin
RNA provides “working copies” of DNA
what is the most chromatin in nucleus?
inactive heterochromatin
lamp brush chromosomes
Active portions of chromosomes unravel to become visible
Histones
most of DNA-associated protein in eukaryotesAssist with DNA folding => chromatin organization into chromosomes
nucleosomes
segments of DNA wrap around several histones; regulate DNA activity
non-histones
may also be involved in regulation of gene activity
what separates the inner and outer nuclear membrane?
perinuclear cisterna
how is the inner and outer nuclear membrane connected
nuclear pore complex surrounded by nucleoporins
inner nuclear membrane
associated with network of lamin filaments for support called nuclear lamina
outer nuclear membrane
studded with ribosomes, continuous with rER
ribosomes
bipartite, proteinaceous structures (contain rRNA), synthesized & assembled in nucleolus, site of protein synthesis
what are the mitochondria NOT present in?
RBC and keratinocytes
within the mitochondria, the inner membrane has cristae which is lined with what?
elementary particles that contain enzymes for oxidative phosphorylation
what does the mitochondria matrix contain?
dense granules thought to be binding/ storage sites for Ca
how does the cell depend on energy and where does it begin?
cellular respiration; in the cytosol where glucose converted to pyruvic acid
where does anaerobic glycolysis occur
cytoplasm
where does aerobic respiration occur
mitochondria; where the the matrix contains Kreb cycle
where is the most ATP produced?
oxidative phosphorylation by cytochromes of electron transport system (ETS)
Cytochromes
enzymes on inner membrane of cristae
Endoplasmic reticulum
series of membranous sheets and tubules throughout cytoplasm
rER
surface receptor molecules for ribosomal attachment, protein synthesis
sER
lipid synthesis, transport proteins from rER to golgi, membrane formation and recycling
coated vesicles in ER
surround and coat proteins for transport, bud off sER, transport proteins between sER & Golgi & between golgi & cell surface
Golgi apparatus
post-translational modification, packaging & sorting of proteins synthesized in rER
what Golgi network is convex?
cis= forming face; proteins arrive from rER in coated transfer vesicles
what golgi network is concave?
trans= maturing face; proteins packaged into clathrin-coated vesicles for secretion
how do vesicles bud off maturing face?
condensing vacuoles, sorted into secretory vesicles for extracellular export via exocytosis or membrane-bound vesicles for intracellular use, or as secretory granules for long term storage
membrane trafficking
during exocytosis & secretion, large amounts of intracellular membrane incorporated into outer cell membrane– recycled by golgi
types of membrane- bound vesicles
lysosomes, endosomes, peroxisomes
lysosomes
contain hydrolytic enzymes
1’ lysosomes
inactive, newly formed produced by rER and golgi
what happenes when 1’ lysosomes fuse with phagocytic vesicles (or phagosomes)?
become phagolysosomes= 2’ lysosomes
3’ lysosome
residual body, hydrolytic breakdown results in production; excreted or remain in cells for life
autophagy
programmed cell death
endosomes
type of endocytic vesicle with acid pH in lumen
example of endosomes
proton pumps, which pump H+ into interior, acidifying contents
peroxisomes
microbodies, membrane-bound organelles containing oxidative enzymes (oxidases); resemble lysosomes—also contain catalase and peroxidase
how do peroxisomes oxidize toxic metabolites
use enzymes, free radicals, and hydrogen peroxide
inclusions
- non-living components of cell
- neutral fat droplets, lipids, glycogen, secretory & pigment granules
viral inculsions
intracytoplasmic or intranuclear
types of intracytoplasmic pigments?
melanin and lipofuscin
melanin
black, brown, granular pigment; produced by melanocytes, transported to other cells
lipofuscin
gold-brown granules; frequently seen in neurons; sometimes called “old age pigment”
