Unit 1 Cell Structure Flashcards
3 basic parts of human cells
plasma membrane
cytoplasm
nucleus
cytoplasm
made up of cytosol and cytoskeleton
plasma membrane
dynamic barrier
maintains gradients
phospholipid bilayer
plasma membrane proteins
integral
extrinsic (peripheral)
glycoproteins
integral proteins
extend through entire membrane
transmembrane proteins
extrinsic proteins
associated with cytoplasmic or extracellular region
glycoproteins
covalently linked sugar residues outside the cell
act as recognition sites
self determinant for immune system
functions of membrane proteins
transport enzymic activity receptors intercellular joining cell-cell recognition attachment
organelles
nucleus endoplasmic reticulum Golgi complex (apparatus) lysosomes mitochondrion peroxisomes ribosomes
nucleus function
- partitioning of DNA
- replication of DNA
- transcription of DNA to RNA
- ribosome assembly
nuclear envelope
double membrane, continuous with ER
nuclear pores
DNA
double helix, stabilized by H-bonding between bases
chromatin
most highly condensed during mitosis
chromatin
DNA packaged with histone proteins
heterochromatin
densely coiled, less active
euchromatin
less dense, transcriptionally active
nucleolus
site of synthesis/organization of ribosomes
nucleolus organization
- nucleolar organizer, encodes DNA
- pars fibrosa - rRNA
- pars granulosa - maturing ribosomes (RNA + proteins)
endoplasmic reticulum (ER)
interconnected network of tubular membranes and flattened sacs; continuous with outer membrane of nuclear envelope
rough ER
surface has many ribosomes; cisterna
site of protein synthesis
growing polypeptide chain glycosylated and released in lumen
proteins packaged and released
smooth ER
no ribosomes or protein synthesis
synthesis of lipids and steroids
glycogen metabolism
detoxification, xenobiotics
sarcoplasmic reticulum
sequesters and releases calcium ions in muscle
Golgi complex (apparatus)
continuation of ER; stacks of flattened sacs; cisternae
processing and packaging of proteins
completes glycosylation
carries out other protein modifications
Golgi complex polarity
cis face - receiving side - fuses with vesicles released from RER
trans face - shipping side - proteins secreted bound for cell membrane
lysosomes
form by budding off Golgi
contains hydrolytic enzymes (lipases, proteases, nucleases, and carbohydrases)
acidic environment (H+ pump)
lysosome function
immunological defense
cellular recycling
apoptosis
mitochondrion
double membrane
enzymes of TCA cycle and beta-oxidation of fatty acids
semi-autonomous (contains its own DNA
cristae
folded inner membrane of mitochondrion
contains carrier proteins of electron transport system and ATP synthase
peroxisome function
contain enzymes for detox:
oxidases - free radicals, etc release H2O2
catalases - converts H2O2 to water and oxygen
oxidize long chain fatty acids
peroxisome structure
resemble lysosomes
may stain darker due to enzymes
ribosomes
protein synthesis
free polyribosomes
proteins for cytoplasm
bound polyribosomes
proteins for outside cell
cytoskeleton functions
cell shape and framework
binding sites for organelles
cellular movement
cellular specializations
cytoskeleton composition
microtubules (largest)
microfilaments (smallest)
intermediate filaments
microtubules composition
tubulin
heterodimers
protofilaments
may form as singlets, doublets, or triplets
tubulin
globular proteins
heterodimers
alpha and beta tubulin
protofilaments
assembly of heterodimers
centrioles
structures composed of 9 triplets crosslinked
centrosome
2 centrioles perpendicular to each other
axoneme
9 doublets + 2 singlets
form cilia and flagella
microtubule function
cellular trafficking
movement of chromosomes
movement of extracellular materials (cilia)
movement of sperm (flagella)
microfilament composition
g actin
f actin
g actin
unpolymerized globular actin proteins
f actin
filamentous actin formed by polymerization of g actin
microfilament funciton
structural support cleavage furrow structural basis of microvilli muscle contraction amoeboid movement cytoplasmic streaming
intermediated filaments
fibrous; more stable
provide structural strength, most diverse
cellular respiration
aerobic - TCA cycle, mitochondrion
anaerobic - glycolysis, cytoplasm