Cytology

There are over 200 distinguishable cell types in the body assembled into which basic tissue groups?

1. Epithelia

2. Connective tissue

3. Muscle

4. Nerve

Type of tissue that

cover body exterior surfaces and line body cavities including blood vessels

epithelia

Type of tissue that

form glands both exocrine and endocrine

have cells that tightly adherent to one another

epithelia

Type of tissue that

known for shapes: squamous, cuboidal and columnar

epithelia

Type of tissue that

functions include protection, absorption, secretion and excretion, and gas exchange

epithelia

Type of tissue that

consists of relatively few cells that are not adherent to each other

connective tissue

Type of tissue that

serve vascular system

has abundant matrix

connective tissue

Type of tissue that

functions include cohesion of structural elements

serves as a medium through which blood vessels distribute nutrients and take up metabolic waste

connective tissue

Type of tissue that

have cells involved in immune & inflammatory responses and in tissue repair following injury

connective tissue

Type of tissue that

is responsible for movement and changes in the size & shape of body organs

muscle

Type of tissue that

has elongated cells oriented parallel to each other and organized in bundles

muscle

Type of tissue that

arrange the filaments highly organized → contraction

muscle

The muscle cytoplasm or sarcoplasm is occupied mostly by _____ and ____

myofilaments actin & myosin

Cells can be various in shapes, sizes and specialized functions

However, they always share common features. List

1. surrounded by a membrane

2. have zero ( ex: in mature RBC) to many nuclei

3. contain organelles, which can be membrane-bound or non-membrane-bound

4. contain inclusions (temporary non-living structures, ex: secretory products, pigment granules, or metabolic byproducts)

The nucleus is a membrane-limited organelle that contains _____ of the cell

genetic information

T/F The nucleus has double membrane, inner and outer, in the nuclear envelope

True

Functions of the nucleus are

• replication of DNA → cell division

• DNA repair

• RNA transcription & processing

Sketch the nucleus

Three major components of nucleus are

1. nuclear envelope

2. chromatin

3. nucleolus

What make up the nuclear envelope?

• outer nuclear membrane - continuous with ER, contains proteins involved in transport and structural support

• inner nuclear membrane

• nuclear pores - protein channels embedded in the membranes - regulate passage of molecules in/out the nucleus

• nuclear lamina - a meshwork of lamin protein on inner membrane - give structural support and anchors chromatin

Why is the evaluation of the morphology of the nucleus important?

to determine the health of a cell through examination of normal cells characteristics

Characteristics found in normal cells are

1. shape: round, ellipsoid, infolded, lobulated

2. size: various

3. number of nuclei per cell: none to multi

4. location: central, basal, eccentric (strange)

T/F Nuclear envelope inner and outer membranes are connected with no space in between

False: they are separated by a 10-30 nm space

The space between the two unit membranes of nuclear envelope

perinuclear cisternae

T/F The nuclear pores are attached to the outer nuclear membrane only

False: the inner and outer nuclear membranes are continuous at nuclear pores

Direction of nuclear pores

bidirectional

T/F Small molecules still have to pass through the nuclear pores

F they can pass through by diffusion

Why do we call the nuclear pores highly selective?

The proteins of any size need to contain a nuclear localization amino acid sequence to be carried through an active transport (ATP or GTP hydrolysis)

Why do we call the structure of nuclear pores nucleoporins

The shape of a central cylindrical body between inner and outer octagonal rings

• each ring = 8 protein particles

The basket on nuclear side formed by protein filaments that extend from each ring

Functions of nuclear lamina are

• give shape and stability to the nuclear envelope

• organize the interphase nucleus

• structural link between chromatin and nuclear envelope

• responsible for the dissolution and reformation of the nuclear envelope during cell division

• position nuclear pore complexes within the nuclear envelope

Location of nuclear lamina

between the inner nuclear membrane and the peripheral heterochromatin

What make up nuclear lamina

a class of intermedia filament proteins called lamins ( lamins A, B, C)

What causes the dissolution of nuclear lamina at mitosis

lamin phosphorylation

Give me some defects of mutations in proteins of the nuclear membranes or pore complexes ( nuclear envelopathies) or lamins ( laminopathies)

Inheritable diseases

• striated muscle disorders, partial lipodystrophy syndromes, peripheral
  neuropathies, progeroid syndromes, developmental abnormalities & death.

Define chromatin

complex of DNA, histone and non-histone proteins found in the nucleus of eukaryotic cells

T/F Chromatins are made up of chromosomes, and carry the cell genetic material.

F Chromatins make up chromosomes

During interphase nucleus

the electron-dense portions of chromosomes are

heterochromatin

T/F Heterochromatin are constitutive (never transcribed). Only euchromatin represents genes that are being transcribed

F Heterochromatin can also be facultative ( transcription depends on cell type)

During interphase nucleus

the uncoiled or loosely packed portions of chromosomes are

euchromatin

Barr body

In XX individual, one of X chromosomes is inactive and highly coiled

Under light microscope, shows up as a small drumstick of heterochromatin located adjacent to the nuclear envelope

Why is nucleolus rich in rRNA and proteins?

functions as a site of ribosomal RNA transcription and rRNA synthesis

regulates cell cycle (nucleostemin)

T/F nucleolus is surrounded by a membrane

False

T/F 1-2 nucleolus in cell determined by the synthetic activity of cell, eccentrically placed in the interphase nucleus

True

Main parts of nucleolus

NO: nucleolar organizer region of those chromosomes processing nucleolar genes

PF: pars fibrosa, dense fibrillary component

PG: pars granulosa or granular component - ribonucleo-protein particles

NAC: nucleolus-associated chromatin

How is nucleolus formed?

regions of 10 interphase chromosomes ( pairs of 5 diff chro in human) that contain the genes that encode rRNA (Nucleolar Organizing Regions) reorganize the nucleoli following cell division

What is the difference between RNA and DNA?

• linear molecule

• ribose sugar instead of deoxyribose

• uracil base instead of thymine

• product of transcription of DNA

messenger RNA (mRNA) is used for

direct the amino acid sequence of proteins

transfer RNA (tRNA) is used for

transfer the correct amino acid to the ribosome for incorporation into the protein

ribosomal RNA (rRNA) is used for

form ribosomes in association with specific protein

Ribosomes are composed of 2 subunits.

large subunit is composed of

5S

28S

5.8S rRNA

~ 49 proteins

Ribosomes are composed of 2 subunits.

small subunit is composed of

18S rRNA

~ 33 proteins

Function of ribosomal large subunit

catalyze the peptide bond formation

Function of ribosomal small subunit

bind mRNA and tRNA

T/F Under the electron microscope, the ribosome can be observed individually

F ribosomes (polyribosomes) appear as granular material, associating with outer nuclear membrane and the endoplasmic reticulum

Series of ribosome formation

in nucleolus

(1) transcription of rDNA to form pre-rRNA

(2) association of pre-rRNA with ribosomal proteins to form ribonucleoprotein

(3) cleavage of pre-rRNA into the 28S, 18S, and 5.8S rRNAs found in ribosomes

in nucleus

(4) 28S and 5.8S rRNA combines with 5S rRNA ( 5S rRNA is transcribed in the nucleus) to form the large ribosomal subunit

(5) active transport of ribosomal subunits to the cytoplasm through nuclear pores

in cytoplasm

(6) assembly of ribosomal subunits into ribosomes and polysomes in the
presence of mRNA

T/F membranes are homogenous

False

T/F membrane components are fixated

F they are in a constant dynamic flux

T/F membranes are asymmetric

True

T/F the underlying cytoskeleton partially determines the shape of the surface of the membrane

True

What is a unit membrane? What does it composed of?

The general structure of cell membranes (plasma membrane and membranes of organelles)

three distinct layers (trilaminar structure) when consisting of two electron dense lines (inner and outer leaflets) separated by an electron-lucent intermediate zone

What basic structures make up the membranes?

• lipids - mainly - 50% of membrane mass - membrane form and permeability properties

• proteins - membrane’s specific functions

• carbohydrates - membrane’s surface recognition, facing away from the cytoplasm

The most abundant type of lipid in membranes

phospholipids

Why do we call the phospholipids amphipathic

a hydrophilic head

the hydrophobic tails

The second major lipid of membranes

cholesterol

Cholesterol function

maintains the structural integrity of membranes

The third most abundant membrane lipids

glycolipids

Where do most glycolipids locate in the membrane?

outer leaflet

peripheral proteins

associate with membranes through ionic
interactions

not across the membrane

integral proteins

buried in the lipid membrane
transmembrane proteins

Which structure perform most of the membrane’s functions

proteins

the presence of membrane proteins is indicated by

freeze fracture technique

Which membrane component contributes to the glycocalyx

carbohydrate

What are Lipid rafts

specialized membrane domains that associate with or segregate
different proteins or signaling molecules in one part of the cellular membrane

What is cytoskeleton?

A highly dynamic, complex network of protein filaments that organizes the cytoplasm and determines cell shape

functions of cytoskeleton

cell motility

organelle and vesicle transport

muscle contraction,
cell division

endocytosis/phagocytosis

providing mechanical strength

Thickest cytoskeleton component

microtubules

Thinnest cytoskeleton component

microfilaments

Strongest cytoskeleton component

intermediate filaments

Why do we call microfilaments actin filaments?

composed of actin which is the major cytoskeletal protein of most cells (~5-10% of total cell protein)

Polarization of actin protofilemnt

G-actin (globular protein) that binds head to tail

Polarization of F-action filament

two actin protofilaments twist around each other (right-handed helix)

Depolarization of actin filaments

ATP hydrolysis in G-actin

T/F a new branch of actin filaments can grow out of the current one

True

Functions of actin-binding proteins

1/ regulate the assembly and disassembly of actin; examples: cofilin,
profiling, gelsolin

2/ influence filament dynamics; for example, actin capping proteins such as
cap Z and tropomodulin regulate filament growth

3/ organize actin filaments into bundles (fimbrin, α-actinin) or networks
(filamin, spectrin, fodrin, dystrophin)

4/ actin-motor proteins utilize ATP to move along the actin filament towards
the plus end; examples myosin I and II

Functions of actin

• cell attachment (focal adhesion)

• cell-cell adhesion

• cell surface modifications (example, microvilli and stereocilia)

• movement/contraction

T/F intermediate filament can be polarized

False

T/F intermedia filaments are composed of a variety of proteins whose expression is cell-type specific

True

Functions of intermedia filaments

structural support & mechanical strength

Classes of intermediate filaments

• Class 1: Keratins – epithelial cells

• Class 2: Vimentin & vimentin-like – fibroblasts, muscle, glial cells, nerve stem cells

• Class 3: Neurofilament – neurons

• Class 4: Lamins – nucleus (in all nucleated cells)

• Class 5: Beaded filaments – eye lens fiber cells

T/F microtubules can branch out from the one and another

False

T/F inside of microtubules are hollow

True

What make up microtubules

from 13 parallel protofilaments, each protofilament is composed of
dimers of α and β tubulin subunits

Microtubules are polarized with a plus end and a minus end.

Which end is fast growing end?

plus end

Microtubules are polarized with a plus end and a minus end.

Which end is slow growing end?

minus end

Which microtubular end is embedded in the MTOC (microtubule-organising center or centrosome)

minus end

What make up centrosome

• fibrous centrosome matrix containing 50 or more copies of the γ-tubulin ring (γ-TuRC)

• a pair of centrioles arranged at right angles to each other. Each centriole is composed of nine triplets of MT

Functions of microtubules

• maintenance of cell shape

• transport of organelles

• separation of chromosomes during mitosis/meiosis

• ciliary/flagellar movement

T/F many functions of microtubules are due to the property of dynamic instability; the rapid conversion between a growing and shrinkage state.

True

Functions of microtubules-associated proteins (MAPs)

• bind to and organize MTs into bundles

• stabilize MTs against disassembly

• mediate interactions of MTs with other cellular components

• serve as molecular motors that are responsible for the movement
  of organelles, vesicles, etc.; they utilize ATP to move “cargo” in a single direction along the filament

kinesin movement toward ___ end

plus

dynein movement toward ___ end

plus