SM01 Mini1 Flashcards
Prokaryote
no nuclear membrane
no organelles
has cell wall b/c no cytoskeleton
Eukaryote
no cell wall
Organelles: membraneous nucleus, mitochondira, endoplasmic reticulum (rough & smooth), Golgi body, Ribosomes, Lysosomes, Peroxisomes, cytoskeleton (plants only: chloroplasts & rigid cell wall)
Nuclear Envelope
2 membranes surrounding eukaryotic cell nucleus
continuous at nuclear pore complexes (3000 on average)
Plasma Membrane
phospholipid bilayer surrounding cell
selective barrier for protection
also contains proteins & cholesterol
all membranes 7.5-10nm thick
Cytoplasm
everything inside the plasma membrane except nucleus
Cytosol
intracellular gelatinous fluid
everything outside organelles, but inside the cell
cytoskeleton, free protein, organic molecules, fatty acids, sugars, amino acids, salts & H2O
contains non-membrane bound organelles (ribosomes, proteosomes)
70% cell volume
Organelle
intracellular membrane bound body with a specific task
distinct structure, macromolecular composition, & function
Extracellular Fluid
fluid of the environment
outside of cell
composition: [Na+]0=145mM, [K+]0=4.5mM,
[Ca2+]0=10-3M, [Cl-]0=102mM, [protein]= 1mM
pH=7.4
Phosopholipid
outer & inner leaflets create plasma membrane
Parts: polar head group, glycerol, fatty acid chain (saturated or unsaturated)
types: 1. phosphatidylethanolamine (ethanolamine + phosphate), 2. phosphatidylcholine, 3. sphingomyelin (has choline), 4. phosphatidylserine, 5. phosphotidylinositol
free lateral & rotational movement, VERY RARE flipping
Antibiotic
water soluble substance derived from a mold or bacterium that inhibits the growth of other microorganisms
Either attack cell wall biosynthesis enzymes or enzymes whose bacterial counterparts are vastly different than our own
Functions of Plasma Membrane
- Physical barrier
- Selective permeability
- Electrochemical gradient
- Communication: molecular signaling
Cholesterol
steroid, lipid soluble, amphiphilic -OH head group
readily flips sides of membrane (smaller head group)
synthesized in ER
precursor to ALL steroids
function: immobilize first few hydrocarbons of phospholipids (decreases membrane permeability) & prevents crystallization of hydrocarbons at low T (only applicable to cold-blooded animals)
Membrane Fluidity
viscosity of lipid bilayer of membrane
influence by: T (increase with T), lipid composition (unsaturated, more fluid), cholesterol composition (more cholesterol, less fluid [except at very low T])
Purpose: change shape for bud off and fusing w/vesicle
Endocytosis
import material from outside to inside by surrounding and pinching off membrane around said material
creation of vesicle
*membranes retain orientation during transfer between cellular components
Exocytosis
exportation of material by surrounding and pinching off of membrane around said material
releasing of vesicle
*membranes retain orientation during transfer between cellular components
Membrane Proteins
types: transmembrane, monolayer associated, lipid-linked, & protein attached (peripheral- removed w/high salt)
all others removed with organic detergent
mobile & fluid throughout membrane, restricted by tethers intra- or extracellularrly or binding to protein on another cell surface (desmosome)
Transmembrane Protein
can work on both sides of membrane
approximately 20aa alpha helix to cross once
removed by organic detergent
Monolayer-associated Proteins
anchored to cytosolic leaflet by amphipathic alpha helix
removed by organic detergent
Lipid-linked Protein
attached to either leaflet by a lipid
cytosolic- fatty acid chain or prenyl group
extracellular- GPI anchor on phosphotidylinositol
removed by organic detergent
Protein-attached Proteins
don’t penetrate membrane, but on both sides
not covalently linked to any membrane components
ionic interactions with membrane components
removed with high salt concentration, doesn’t disrupt membrane integrity
Microscopy visualization
minimum naked eye= 0.2mm= 2000nm
light microscope= 200nm-2000nm
electron microsope=0.2nm-200nm
mitochondria=2000nm=2 micrometers
average human single cell= 10-20 micrometeres
Lipid Raft
lipid domains with different composition that bind or travel together trough membrane
interaction/aggregation of sphingomyelin, glycolipids, & cholesterol (proteins with longer transmembrane domains & GPI-linked)
more ordered & tightly packed that bilayer
compartmentilize cellular processes, some form caveolae
Glycosylation
addition of carbohydrate to protein or lipid
occurs in lumen of ER & Golgi
if membrame destined, carbohydrate always found on outer leaflet
Permeability of Membrane
synthetic model
all hydrophobic molecules: O2, N2, CO2, benzene
some small uncharged polar: H2O, urea, glycerol
few large uncharge polar molecules: glucose, sucrose
NO ions!
Intracellular Fluid
aka cytosolic fluid
composition: [Na+]0=15mM, [K+]0=120mM,
[Ca2+]0=10-7M, [Cl-]0=20mM, [Protein]= 4mM
pH=7.2
Plasma Membrane Protein Function
- transport
- anchor
- receptor (communication)
- enzyme
Ribosome
large & small subunits made of protein & RNA
perform RNA translation to protein (1º structure)
found in the cytosol & on ER
Cytoplasmic Inclusions
nonmolite
no membrane
composed of accumulated metabolites
mainly: fat droplets, glycogen granules, & lipfuscin granules
Fat Droplet
no membrane, spheroid
type of cytoplasmic inclusion
accumulation of lipid molecules
mostly found in adipocytes, adrenal cortex cells, liver
often in association with smooth ER (where lipids are made)
clear in EM picture
Gylcogen Granules
aka rosettes
type of cytoplasmic inclusion
stored energy source
no membrane
aggregates of glycogen
mostly in liver & skeletal muscle
dense, dark no clear shape in EM picture
Lipfuscin Granules
type of cytoplasmic inclusion, but sometimes has membrane
small, pigmented golden-brown in LM
accumulated waste product
occur with age in stable non-dividing cells ie. neurons & muscle
Cytoskeleton
network of protein filaments criss-crossing the cell
constantly assembling & disassembling
cell shape, movement of intracellular material, motility of cell
Microtubules
Subunit: Tubulin (alpha & beta heterodimers)
functions: intracellular organelle transport, form cilia & flagella, form mitotic spindle
beta points to + end; alpha to - end
grows & shrinks at + end
bound to GTP, conversion to GDP signals tubulin breakdown
13 protofilaments form hollow tube
Microfilaments
aka Actin (after subunit)
function: shape at cell’s surface, rearranging powers locomotion, form contractile ring during mitosis
2 standed helix add at + end
G actin: free globular actin monomers
F actin: assembled in filaments
treadmilling: subunit travels through filament & falls off - end, occurs when rate of addition= rate of falling off
Intermediate Filaments
Subunit: several proteins
function: provide mechanical strength & form nuclear lamina
monomer → dimer (coiled together) → staggered tetramer → 8 tetramers twisted into ropelike filament
very tough, survive cell death
ex. hair, nails, outer layer of skin
Dyenin
protein motor on microtubules
transports material to - end (nucleus)
uses ATP
slides microtubule doublet past another to bend cilia or flagella
Kinesin
protein motor on microtubules
transports material to + end (cell periphery)
uses ATP
Myosin
motor protein on actin that slides one filament across another
uses ATP
basis of contraction
Cilia
beat back & forth to moe material past
short & numerous
made of microtubules (9+2 formation of doublets)
use of basal bodies instead of centrosome for nucleation
ex. respiratory tract
Flagella
beat back & forth to move cell
long & few
made of microtubules (9+2 formation doublets)
use of basal bodies instead of centrosome for nucleation
ex. sperm tail
Lamellipodia
thin foot
leading edge of cell during cell motility driven by actin polymerization
Fillopodia
thread foot
slender cytoplasmic projections that extend beyond lamellipodia in migrating cells
form adhesions with substratum
sense cheomtropic cues & change direction
Microvilli
formed by dense bundle of cross-linked actin filaments that are linked to terminal web
increase cell surace area for absorption, secretion, cellular adhesion, & mechanotransduction
Desmosomes
link intermediate filament networks of adjoining cells to hold tissue together
Types of Intermediate Filaments
Cytoplasmic: keratins (epithelia), vimemtin & related (connective tissue, muscle, & glial cells), neurofilaments (nerve cells)
Nuclear: nuclear lamins
Nuclear Lamins
intermediate filament inside of nuclear envelope of all cells
control assembly of nuclear envelope & organization of perinuclear chromatin
Centrosome
microtubule organizing center
1 in interphase, 2 in mitosis
anchors - end (alpha side) near nucleus in interphase or spindle poles in mitosis
2 centrioles at 90º from each other
Centriole
nine triplets of microtubule with protein links between them
two together at 90º make up a centrosome
Pericentriolar Matrix
PC
cloud of protein around centrioles in which their - ends are embedded
contain gamma-tubulin in rings= nucleating sites
Basal body
made of two centrioles at 90º
but no Pericentriolar matrix with gamma-tubulin nucleating rings
ARP
actin-related proteins
begin assembly of filaments, but don’t cap so monomers can still fall off
most frequently nucleated at or near plasma membrane
Spectrin
stabilizes actin filaments that make up the terminal web
binds them to the apical cell membrane
Taxol
chemotherapeutic drug that binds & stabilizes microtubules
thus inhibiting cell division
Nucleus
organelle in eukaryotes, “brain of the cell,” houses DNA
functions: cellular regulation (genetic material) & production of ribosomal subunits
dense circle in cell on LM
most cells have one, but some have more (hepatocytes, skeletal muscle) & few have none (erythrocytes)
Nuclear Lamina
composed of intermediate filaments (lamins)
functions: mechanical support, attachment site for chromatin to envelop, control nuceus disassembly during mitosis
Chromatin
DNA & proteins (ie histones)
found in nucleus of eukaryotic cell
Chromosome
structure of long DNA molecule & associated proteins that carry hereditary information of a human cell
46 in human
usually only seen during mitosis or meiosis
Nucleosome
8 histone molecules: 2 each of H2A, H2B, H3, & H4
DNA wraps around it and is held on at Link DNA by H1 histone
rRNA
ribosomal RNA
used to make ribosomes
transcribed & translated in nucleolus
knobs on top of 5 chromosomes code for these (13, 14, 15, 21, 22)
when knobs come together with cloud of assembling ribosomes, creates nucleolus (this is how you can have multiple)
mRNA
messenger RNA
codes for proteins
transcribed & modified (splicing & 3’ polyadenylation) in nucleus, then transported to cytoplasm to ribosomes
tRNA
transfer RNA
used during translation to carry and match up with amino acids
Heterochromatin
dense black spots in nucleus on EM
highly condensed, transcriptionally inactive DNA
Euchromatin
clear areas in nucleus on EM
less condensed, transcriptionally active DNA
Telomere
caps the end of a chromosome so they don’t degrade
repeated nonsense DNA
replication origin
when DNA or RNA polymerase binds & starts transcription
Centromere
DNA location on sister chromatids that bind together
Kinetochore
Proteins that bind to the centromere & link microtubules that form spindle fibers during mitosis
NPCs
Nuclear Pore Complexes
VERY tightly regulated
controls movement of all macromolecules between nucleus & cytoplasm
ions, ATP & <50kDa proteins diffuse freely
Targeting Signal
organelle specific proteins MUST have one to get to its corresponding organelle
made of a unique amino acid sequence & folded in a particular parttern: single discrete stretch or juxaposition after folding
NLS
Nuclear Localization Signal (or Sequence)
signal for nuclear import
usually basic amino acids
NES
Nuclear Export Signal (or Sequence)
singal for nuclear exportation
usually contains hydrophobis amino acids
Importins
import carriers to nucleus
binds NLS-containing import cargo→ docks at NPC→ carries through NPC→ stimulated to release cargo by RAN protein inside nucleus→ recycles back to cytoplasm
Exportins
export carriers from nucleus
binds NES-containing export cargo→ docks at NPC→ carries through NPC→ stimulated to release cargo by RAN protein outside nucleus→ recycles back to nucleus
RAN
small GTPase that regulates binding and release of importins & exportins
regulated by GTP or GDP form
DNA Structure
Phosphate- sugar backbone: 5’C one sugar- phosphate- 3’C next sugar
sugar is deoxyribose: 5C, 5 membered heterocyclic ring (5’ is NOT in ring)
nucleosides are attached at 1’ C: can be C, G, A, or T
guanine & cytosine form 3 H bonds, adenoine & thymine form only 2
in humans: antiparallel strands form double helix
Requirements for Genetic Material
- carry information
- must replicate
- must be able to change, mutations
- must govern phenotype
DNA Replication
semiconservative
occurs during S (synthesis) phase during interphase
Initiation
proteins bind to DNA & open helix to prepare for complementary base pairing
Elongation
proteins connect the correct sequence of nucleotides to extend the new strand of DNA
Termination
proteins release the replication complex
Rules of Replication
- semiconservative
- starts at “origin”
- bidirectional
- semi-discontinuous
- synthesized in 5’ → 3’ direction
- RNA primers required
Semiconservative
in replication each strand is a template for a new daughter strand & stays with daugther strand wehn cell divides, so each new cell has 1 parent & 1 daughter
Ori
origin of replication
where DNA replication starts
many on eukaryotes, approx. every 100,000bp
Leading Strand
DNA fragment going toward the replication fork
synthesized continuously
Lagging Strand
synthesized in fragments (Okazaki)
moves toward origin
Okazaki Fragments
short fragments of new DNA form the lagging strand template
DNA polymerase delta
synthesizes lagging strand
also has exonuclease activity to correct errors in 3’→5’ direction
DNA polymerase epsilon
synthesizes leading strand of DNA
also has exonuclease activity to correct errors in 3’→5’ direction
DNA polymerase alpha
primase that works as DNA & RNA polymerase
RNA polymersase part provides a base paired 3’ end as a starting point for delta/epsilon by creating approx. 10 nucleotide primers
b/c DNA polymerase delta/epsilon can only add to existing strand
Telomerase
enzyme with integrated RNA template for the lagging strand of the telomere
sequence is tandem repeats
RNA-dependent DNA polymerase
