Lecture 4, 6, 7 Flashcards
(50 cards)
List and describe the structure & function of the nucleus
Structure: Largest organelle in the cell
- 10% volume
- DNA sequestered in nucleus
Function:
- houses
1. nucleolus- site of ribosome production - has 3 zones
a: Fibrillar center - pale region of DNA loops of 5 chromosomes
b: Fibrillar material- transcription of rRNA genes
c: Granular material - initial ribosomal assembly
- nuclear envelope- inner and outer mem
- nuclear lamina- mesh like sheet
- nuclear pores
- made up of >50 protein (nucleoporins)
- allow transport of molecules btw nucleus
and cytoplasm
- ions 9 nm = active transport - nucleoplasm
Ribosome
Structure:
- made in nucleus
- leaves nucleus and goes to cytoplasm
- 2 ribosomal RNA subunits and associated proteins
- has: membrane bound ribosomes + free ribosomes
Function:
- site of protein synthesis (translation)
Endoplasmic Reticulum
Structure: interconnected network that spans cytoplasm
- ER mem continuous with nuclear envelope membrane
Function:
- allows protein and lipids to travel from nucleus because it comes in contact with Nuclear Pore Complex
- two regions:
1. Smooth ER
2. Rough ER
RER
Structure: has membrane bound ribosomes and structure is continuous with plasma membrane. The ribosome is where tRNA and mRNA come in to produce protein from mRNA.
- next to nucleolus which makes ribosomes
Function:
synthesis of proteins destined for plasma membrane, lysosomes, or secretion
SER
Structure: lacks ribosomes
Function:
- synthesis of lipids and detoxification
Golgi
Structure: flat membrane enclosed cistern
- located next to nucleus + centrosome
- microtubule dependent
- esp well developed in secretory cells: rER -> sends golgi –> secretory
- 2 faces:
- CIS/ CGN (cis golgi network); entry
- TRANS/ TGN (trans golgi network); exit
Function:
- post translational modifications
- processes, packages, transports synthesized protein from Golgi to lysosome via TGN
rER- Golgi - lysosomal pathway, constitutive secretory pathway, regulated secretory pathway
Lysosome
Structure:
membrane enclosed compartments with hydrolytic enzymes which need an acidic envt
Function:
digestive organelles
Peroxisome
Structure: small organelle
- made by free ribosomes (cytoplasmic) - sER
Function:
- fat metabolism (B oxidation enzymes, FA oxidation, catalyze initial reactions in formation of plasmalogens
- deficiencies cause: abnormalities in myelination of nerve cells because they normally have phospholipids in myelin
- degrade toxic reactive oxygen molecules
- have catalase
- convert H202 to O2 and water
- liver: detox of ingested alcohol
Mitochondria
Structure:
- 2 membranes = outer and inner
- 2 compartments = intermembrane space and matrix
Function: look at slide 64*** generate ATP via: TCA oxidative phosphorylation B oxidation of FA
Diseases:
- MERRF: myoclonic epilepsy with ragged red fibers
- mutation in tRNA gene - Leber hereditary optic neuropathy
Describe the structure and function of the nucleolus, nuclear envelope and nuclear
pore complex.
Nucleolus:
- site of ribosome production
- has 3 zones
a: Fibrillar center - pale region of DNA loops of 5 chromosomes
b: Fibrillar material- transcription of rRNA genes
c: Granular material - initial ribosomal assembly
Nuclear Envelope:
- inner membrane= functions as scaffold stabilizing the nuclear envelope
- outer membrane= continuous with RER; contains ribosomes
Nuclear Pore Complex: - made up of >50 protein (nucleoporins) - allow transport of molecules btw nucleus and cytoplasm - ions 9 nm = active transport
Describe the organization of chromatin structure.
Chromatin= is chromosomes in various degree of uncoiling
- packaged into nucleosomes (protein/ histones + DNA)
Distinguish euchromatin and heterochromatin in a nucleus
Chromatin can be:
- Euchromatin: lightly stained
- less condense = more transcriptionally active - Heterochromatin: densely staining
- highly condensed chromatin = less transitionally active
Predict cellular activity based on the chromatin structure. Describe the bi-directional vesicle transport between the endoplasmic reticulum and Golgi apparatus
Cellular Activity of chromatin Structure:
- Euchromatic: more transcriptionally active/ less condense
- Heterochromatin: less transcriptionally active/ more condense
- chromosome has centromere: centric
heterochromatin that holds sister
chromatids together during interphase
Bi-directional vesicle transport btw ER and Golgi: slide 48
- COP1: Retrograde = CGN - rER
- COP2: Anterograge = rER- CGN
Describe protein trafficking for lysosomes, secretion, plasma membrane, nucleus,
mitochondria, cytosol and peroxisomes.
- Membrane bound ribosomes:
- attached to cytoplasmic surface of ER/ RER
- synthesis protein translocated into ER lumen
- ribosome -> ER -> Golgi -> lysosome, secretion, plasma membrane
- Free ribosome: unattached
ribsome -> nuclear protein, MT protein, cytosolic protein, peroxisomal protein
List and describe the three cellular pathways to lysosomal degradation.
- phagocytosis
- endocytosis
- autophagy - self eating
- intracellular membrane surrounds organelle + cytoplasm –> autophagosome formed –> fuses with lysosome –> degraded, recycled and reused
- used for cell aging, cell death or starvation
Describe the types of intracellular inclusions
Inclusions: cytoplasmic or nuclear structures formed from metabolic products of the cell
1: Pigments
a: lipofucsin
- brown gold
- non dividing cells “wear and tear”
b: hemosiderrin
- brown
- iron storage
- formed from hemoglobin (spleen)
c: melanin
- brown pigment
- Glycogen
- storage of glucose
- non membrane bound dense bodies - Lipid
- non membrane bound dense bodies
- fat droplets; liquid at room temp
- energy store
- source of short carbon chains
- lipidoses (lipid storage disease
List the three major types of protein filaments that form the cytoskeleton.
- Microtubules
- Intermediate filaments
- Microfilaments
Describe the structure, function and assembly of microtubules, intermediate filaments and microfilaments.
Microtubules: Structure --> - non branching, rigid, hollow tubes - polar - and + end - a/b tubulin - 25 nm
–> Function:
- intracellular transport
- cell motility (cilia and flagella)
- mitotic spindle
- rigid intracellular skeleton - cell shape and polarity
- have MAP: microtubule associated proteins i.e.:Tau (stabilize axonal microtubules) –> linked to Alzheimer’s
Note:
9 microtubules –> centriole (basal body for cilia and flagella)–> centrosome
Intermediate filaments: Structure: - 6 classes: a: 1, 2keratins- all epithelial cells b: vimentin, vimentin like- mesoderm c: neurofilaments- neurons d: lamins- nucleus e: beaded filaments- eye lens
- 8-12 nm
- nonpolar
- rope like filaments
Function:
- stabilize cell structure (maintain position of nucleus and other organelles
- resist shearing forces (connect with desmosomes and hemidesmosomes; extend across cytoplasm)
- essential for integrity of cell to cell and cell-ECM junctions
Microfilaments:
- aka actin filaments
- 7 nm
- actin: g and f (f needs ATP)
- polarized structure ( + and - polar ends needed for movt)
- can be as single, bundle or networks
Describe the structure and function of the centrosome.
9 microfilaments arrange together –> create the centriole (basal body needed for cilia and flagella –> make up the centrosome
Centrosome structure: slide 70
- has pair of centrioles so they are perpendicular to each other
- amorphous(ill defined) protein matrix
- y tubulin =nucleation site for microtubules
Centrosome function:
- organize microtubules
- neg end: microtubules nucleated
- pos end: microtubules point out to periphery
Describe the structure and function of the primary cilia, cilia and flagella.
Primary cilia:
- microtubule, antennae like
- sensory antennae: chemoreceptor, photoreceptor, or mechanoreceptor (polycystic kidney disease)
- 9+0
Cilia:
- microtubules base, hair like structure
- motile: synchronous
- 9+2
- pair of dynein arms
- anchored to cell via basal body
Flagella:
List and describe the molecular motor proteins associated with microfilaments and microtubules.
Microtubules: Dynein Family
- move along microtubules from + to -***
- meaning moving from lysosome to MT
- 2 members:
a: cytoplasmic dynein
b: axonemal dynein
- cilia + flagella (most caused by bending of the core-
axoneme)
Microtubules: Kinesin
- move from - to + (cell body to out in periphery)
Microfilaments: Myosin
Myosin 2: generates force for muscle contraction
- has polar head that binds and hydrolyzes ATP
Stages:
1. attachment
2. release- ATP binds; reduce affinity for actin
3. bending- ATP hydrolysis
4. power stroke
5. reattachment
Describe role of the cytoskeleton in intracellular transport and cellular motility.
Intracellular transport:
- Cilia and Flagella - via Microtubule Dynein
- Myosin via Microfilaments/ actin
Cellular motility:
- Protrusion- actin dependent
- actin polymerization (monomer to polymer) at + end extends lamellipodium - Attachment
- actin anchored to ECM via integrin proteins - Contraction
- bulk of cells and cytoplasm dragged forward
List and describe the three components of whole cell motility across a substrate.
3.
List and describe the three types of membrane protrusion structures.
- Filopodia
- finger like projections
- actin filaments - Lamellipodia
- sheet like structures - Pseudopodia
- 3D projections
