Cell 2 Flashcards
(23 cards)
What is the narrow space b/w the internal/external nuclear evelope membrane called?
What are the internal/external membranes associated with?
Are these membranes permeable to ions/proteins?
perinuclear cistera.
Internal membrane closely associated w/ fibrous lamina composed to 3 proteins Lamins A,B,C.
External membrane continuous w/ ER
They are not permeable.
What can pass through the nuclear pore complex?
ions and small molecules can pass freely but larger molecules require an active ATP-dependent process.
Describe both heterochromatin and euchromatin
Heterochromatin: electron dense and basophilc (likes basic dyes). It is unexpressed DNA that appears as coarse clumps.
Euchromatin: Less coiled chromosomes that appear as dispersed granular materal. Site of active transcription. CELLS ACTIVELY SYNTHSIZING PROTEINS have MORE euchromatin THAN heterochromatin.
What is chromatin composed of?
Coiled strands of DNA bound to histone proteins.
The human cell in the (haploid or diploid?) state contains _ _ pairs of chromosomes and _ _ sex chromosomes.
Are germ cells haploid or diploid?
Diploid; 22; 2;
Germ cells are haploid.
What is special about the chromosomes in a diploid female?
One X chromosome remains EUCHROMATIC while the other is condensed and inactive. It is called a Barr body.
What is the nucleolus?
Where are the protein components synthesized?
It is a spherical structure rich in rRNA & protein.
Protein synthesized in cytoplasm.
What are the 3 components of the nucleolus?
- Nuclear organizer DNA: Base sequences coding for rRNA
- Pars Fibrosa: Densely packaged ribonucleoprotein fibers closely associated w/ nuclear organizer DNA. It represents primary transcripts of rRNA genes
- Pars Granulosa: 15-20nm granules representing maturing ribosomes.
What are the 5 phases of the cell cycle and describe them? (phases 2-5 are mitosis)
1) Interphase: phase b/w 2 mitoses. DNA synthesis, and centrosome duplication occurs
2) Prophase: Coiling of chromatin, microtubles disintegrate, centrosomes separate and begin to migrate, NUCLEAR MEMBRANE/NUCLEOLUS DISAPPEAR, chromatin condenses to form chromosomes of 2 chromatids bound at centromere, mitotic spindle appears.
3) Metaphase: chromosomes migrate to equator, chromatids attached to microtubules of mitotic spindle at kinetochore
4) Anaphase: Sister chromatids separate and migrate to opposite poles, pulled by microtubles
5) Telophase: reappearance of nucleii in daughter cells, chromosomes uncoil, cleavage furrow develops b/w cells
What are the 3 phases of interphase in the cell cycle?
What is G0?
G1 (presynthesis)
S (DNA synthesis)
G2 (Post-DNA duplication)
Cells not actively dividing temp or perm are suspended in G0.
What is apoptosis? How does it occur?
What is oncosis/necrosis? How does it occur?
Programmed cell death; complex pathways activated, leading to a compacted nucleus, specific cleavage of chromatin, and blebbing of PM, PM doesn’t rupture so no immune system response.
Accidental cell death; cells swell and release intracellular components into extracellular space stimulating immune response often leading to inflammation.
What are microvilli and where are they located?
What is the brush border?
What are microvilli made of?
Fingerlike projections on the apical surface of cells (esp absorptive cells w/ thick glycocalyx)
Brush border=microvilli+glycocalyx
Microvilli have an actin core, actin filaments extend into the body of the cell where they form a network AKA TERMINAL WEB
What are stereocilia?
Where are they found?
Long, NONMOTILE, microvilli.
Found in epididymis (absorptive), and on hair cells in inner ear (sensory).
What are microplicae?
Fold-like extensions of cytoplasm present in cornea and esophagus. They function to increase Surface Area and the adherence of fluids to the surface.
What are the 5 types of cell junctions?
- Tight junctions (ZONULAE OCCLUDENS)
- Intermediate junctions (ZONULA ADHERENS)
- Gap Junctions
- Desmosomes (MACULA ADHERENS)
- Hemidesmosomes
What is the tight junction?
The most apical junction that divides the PM into the apical and basolateral domains.
Forms a tight band encirciling the cell/membrane. Membrane fusion sites b/w adjacent cells close off the basolateral domain from the extracellular space.
What is an intermediate junction?
Basal to tight junctions. Encircle cell.
Actin filaments form the terminal web insert on the cytoplasmic surfaces
What is a gap junction?
Found on basolateral membrane in almost all cells. Forms hexamers w/ a HYDROPHILIC pre which allows small molecules to pass.
What are Desmosomes?
Are they abundant in protective or multilayered epithelia?
complex disk shaped structure on one cell matched to an identical disk structure on the adjacent cell. They have tonofilaments which form hair pin loops.
Protective or multilayered epithelia bound togeher by many desmosomes
What are hemidesmosomes? What type of collagen fivers are they anchored by?
They are half desmosomes found at basal serfice.
They are anchored by type 7 collagen fibers to the subjacent basal lamina
What is the basal lamina?
What are the 2 layers?
By what type of collagen fibers is the basal lamina attached to the underlying connective tissue?
A sheet like extracellular structure in b/w an epithelial cell and subjacent contective tissue.
- Lamina densa: electron dense layer, CONTAINING TYPE 4 COLLAGEN
- Lamina rara: electron lucent layer (can be present on one or both sides of lamina densa)
Basal lamina attached to connective tissue by type 7 collagen fibers
How is the basement membrane formed?
2 ways: 1)The fusion of 2 basal laminae
2)A basal lamina fuses w/ a reticular lamina (which is formed by FIBROBLASTS in the underlying connective tissue. It contains fibronectin and type 3 collagen)
