Histology of Eukaryotic Cell

Question 1

Cell

Cells are the __ _ of ___ organisms. There are approximately ___ different cell types in humans.

They are basically a mass of____ containing a ____ and ____ from the environment by a selectively permeable membrane.

Two physiologically distinct compartments.

1. ____
2. ____

Answer 1

Cells are the structural units of living organisms. There are approximately 200 different cell types in humans.

They are basically a mass of protoplasm containing a nucleus and partitioned from the environment by a selectively permeable membrane.

Two physiologically distinct compartments.

1. Cytoplasm
2. Nucleus containing nucleoplasm

Question 2

Components of the Cytoplasm

9

P

M

R

E

G

L

P

P

S

Answer 2

[*] Plasma membrane
[*] Mitochondria
[*] Ribosomes
[*] Endoplasmic reticulum
[*] Golgi apparatus
[*] Lysosomes
[*] Proteasomes
[*] Peroxisomes.
[*] Secretory vesicles or granules.

Question 3

Which cell has no nucleus

Which cell has more than one nucleus

Answer 3

RBC

Muscles and Hepatocytes (liver)

Question 4

Plasma Membrane (PM)

[*] A ______membrane composed of ____, ____, _____ and ____
[*] A selective barrier that maintains the intracellular environment____from the extracellular one.
[*] Functions in ____ and ____.
[*] Controls_____.
[*] Range in thickness from ____ and visible by ____
[*] Unit membrane = an ____ sandwiched between ____.

PM’s are roughly __% lipid, __% protein and __ % carbohydrate.

Answer 4

[*] A limiting membrane composed of phospholipids, proteins, cholesterol and oligosaccharides.
[*] A selective barrier that maintains the intracellular environment distinct from the extracellular one.
[*] Functions in recognition and regulation.
[*] Controls interactions with the extracellular environment.
[*] Range in thickness from 7.5-10 nm and visible by E.M.
[*] Unit membrane = an electron lucent layer sandwiched between two electron dense layers.
[*]
PM’s are roughly 45% lipid, 50% protein and 5 % carbohydrate.

Question 5

Activities of the Plasma Membrane

____:

_____:

_____: ________ of the PM which entrap extracellular___ and __ ___. These vesicles___ ___and eventually ________.

____: “___________”. Removes ____ ____, ___, ____ ___ etc. Cytoplasmic ____ surround the object, ___ ____ enclosing object in an intracellular _____.

Answer 5

Endocytosis: Mass uptake of material through the PM

Exocytosis: Bulk release of material through the PM

Pinocytosis: Invaginations of the PM which entrap extracellular fluid and soluble material. These vesicles pinch off and eventually fuse with lysosomes.

Phagocytosis: “Cell eating”. Removes foreign bacteria, fungi, damaged cells etc. Cytoplasmic processes surround the object, edges fuse enclosing object in an intracellular phagosome.

Question 6

Mitochondria

ØThe ___projects folds or ___ into the interior of the mito. These structures ____ the ___ of the IMM/
ØThe mitochondrial matrix is____ rich and contains __ ___ ___ and ___

Answer 6

ØThe IMM projects folds or cristae into the interior of the mito. These structures increase the surface area of the IMM/
ØThe mitochondrial matrix is protein rich and contains DNA, tRNA, rRNA and mRNA.

Question 7

Endoplasmic Reticulum

[*] A system of_____ _____ that form a continuous membrane and enclose a ____.
[*] ___ types of ER ____with one another
1.
2.

Can also use cisterna to describe____

Answer 7

[*] A system of intercommunicating channels that form a continuous membrane and enclose a cisterna.
[*] Two types of ER continuous with one another
1.Rough ER (RER).
2.Smooth ER (SER).

Can also use cisterna to describe part of mitochondria

Question 8

Rough ER

[*] Prominent in cells specialized for____ ____

[*] ___ and ___ stacks of ____.

[*] ___ face dotted with ribosomes.

[*] ___ proteins not ___.

Answer 8

[*] Prominent in cells specialized for protein secretion.

[*] Saclike and parallel stacks of cisternae.

[*] Cytoplasmic face dotted with ribosomes.

[*] Segregates proteins not destined for the cytosol.

Question 9

Ribosomes

[*] ___-dense particles, ___X___ nm in size.
[*] Composed of ____ and ____.
[*] In eukaryotic cells the ____is synthesized in the nucleus and ribosomes comprise ____, ___Sand __S.
[*] Ribosomes stain ___ with ____
[*] Individual ribosomes are held together by ____ to form ____.
[*] mRNA encode for ____ and ribosomes______ into protein.

Answer 9

[*] Electron-dense particles, 20 X 30 nm in size.
[*] Composed of 4 types of RNA and >80 proteins.
[*] In eukaryotic cells the RNA is synthesized in the nucleus and ribosomes comprise 2 different subunits, 60S and 40S.
[*] Ribosomes stain blue with haemotoxylin.
[*] Individual ribosomes are held together by mRNA to form polyribosomes.
[*] mRNA encode for amino acids and ribosomes decode this and translate it into protein.

Question 10

Smooth ER

[*] A membranous network lacking ____ so it appears smooth.

[*] SER is ___ with RER.

[*] SER has specialized functions including _______ & ____

[*] In muscle cells the SER is specialized and participates in ____. Here it is called the ____ ____ and is involved in the ____ and ___ of __ during contraction.

Answer 10

[*] A membranous network lacking polyribosomes so it appears smooth.
[*]
[*] SER is continuous with RER.
[*]
[*] SER has specialized functions including synthesis of steroid hormones & phospholipids.
[*]
[*] In muscle cells the SER is specialized and participates in contraction. Here it is called the sarcoplasmic reticulum and is involved in the sequestration and release of ca2+ during contraction.

Question 11

Golgi Apparatus

[*] This organelle completes the _____

[*] It ___ and ___ the ____ _____ of the these proteins.

[*] RER ___ ___ ___ that shuttle _____ to the Golgi.

[*] Close to the RER the Golgi cisternae are ____ and form the -__ face

.[*] The opposite, ___ face is the____ face.
[*]____ ____ transport protein between Golgi compartments.

Answer 11

[*] This organelle completes the post-translational modification of proteins.

[*] It packages and directs the ultimate destination of the these proteins.

[*] RER buds off vesicles that shuttle new proteins to the Golgi.

[*] Close to the RER the Golgi cisternae are convex and form the cis face

.[*] The opposite, concave face is the trans face.
[*] Budding vesicles transport protein between Golgi compartments.

Question 12

Endosomes

ØThese are a system of ___ and ___ located within the ____ near the ____ (early endosomes) and ____ within the cytoplasm (late endosomes).
ØEndosomal membranes contain _____ which _____.
ØThe acidic environment causes the _____.
ØReceptors may ____ while the ligands are then_____
Ø

Answer 12

ØThese are a system of vesicles and tubules located within the cytosol near the cell surface (early endosomes) and deeper within the cytoplasm (late endosomes).
ØEndosomal membranes contain ATP-driven proton pumps which acidify the interior compartment.
ØThe acidic environment causes the separation of ligand/receptor complexes.
ØReceptors may recycle back to the PM while the ligands are then contained within late endosome
Ø

Question 13

Lysosomes

[*] Sites of ___ and ____

.[*] Membrane-_____, internally ___ and containing ____ enzymes.

[*] Abundant in ____ cells like ____

[*] Spherical, ____ in diameter.
[*] Lysosomal membranes and proteins are ____
[*] They are delivered separately in ____ coated vesicles to ____ forming ____ which then_____

Answer 13

[*] Sites of intracellular digestion and turnover

.[*] Membrane-limited, internally acidic and containing hydrolytic enzymes.

[*] Abundant in phagocytic cells like macrophages.

[*] Spherical, 0.05-0.5microm in diameter.
[*] Lysosomal membranes and proteins are packaged in the trans-Golgi network
[*] They are delivered separately in clathrin-coated vesicles to late endosomes forming endolysosomes which then mature to form lysosomes.

Question 14

Primary and Secondary Lysosomes

Answer 14

Primary Lysosomes: Lysosomes not involved in digestion.

Secondary lysosomes: Lysosomes fused with a phagosome, heterogeneous in size and appearance.–> are involved in digestion

Question 15

Residual Body

___ material remaining within ____ after ___ ___ ___ into the ____

Answer 15

Indigestible material remaining within vacuoles after soluble products diffuse into the cytosol.

Question 16

Autophagosomes

fusion of ____ with ____

Answer 16

Fusion of lysosome with intracellular organelles.

Question 17

Heterophagosomes

Fusion of ____ with ____ containing _____ ____

The end product of auto and hetero-phagic ___ is a___pigment which ____s with___. This is ____

Answer 17

Fusion of a lysosome with phagosomes containing foreign materials.

The end product of auto and hetero-phagic vacuoles is a yellow pigment which accumulates with age. This is lipofuscin

Question 18

Proteasomes

Multiple ____ complexes that _____ ____ ____.

Removes ____ AND ___ _____ proteins

Answer 18

Multiple protease complexes that digest ubiquinated proteins. Removes excess and improperly folded proteins

Question 19

Peroxisomes

____ organelles that ____ _____ ____ by___ _____ atoms to ____ ____. The product hydrogen peroxide is___and removed by___, also ____.

Peroxisomes also ___ ____ ____ chain and ____ chain ___ ____

Answer 19

: Spherical organelles that oxidize organic substances by tranferring hydrogen atoms to molecular oxygen. The product hydrogen peroxide is toxic and removed by catalase, also in the peroxisome. Peroxisomes also beta oxidize long chain and branched chain fatty acids.

Question 20

Secretory vesicles or granules

Found in cells that ____

Vesicles are ___ bound

Vesicles containing ___ are ____ ___

Answer 20

Found in cells that store a product.

Vesicles are membrane bound. Vesicles containing digestive enzymes are zymogen granules

Question 21

Centriole

___ ____ in a centrosome.

___ bundles of ___ microtubules

Each centriole is surrounded by ___ material (__ ____)

§Cylindrical bodies (___ X____) of short microtubules.
§Each centriole composed of ___ sets of microtubules arranged in____.

Answer 21

2 perpendicular in a centrosome.

9 bundles of 3 microtubules

Each centriole is surrounded by granular material (brown haze)
§Cylindrical bodies (0.15 X 0.3-0.5microm) of short microtubules.
§Each centriole composed of 9 sets of microtubules arranged in triplets.
§

Question 22

Centrosome

§Close to the ___ in ___ cells is the centrosome which is composed of ____ with their long axes perpendicular to each other.
§Before cell division (s phase) centrosome ____.
§During mitosis the centrosomes ___ and ____ where they become ____________.

Answer 22

§Close to the nucleus in non-dividing cells is the centrosome which is composed of 2 centrioles with their long axes perpendicular to each other.
§Before cell division (s phase) centrosome duplicates.
§During mitosis the centrosomes divide in two and move to opposite poles of the cell where they become organizing centers for microtubules of the mitotic spindle.

Question 23

Microtubules

• Cylindrical tubes of ____in all ____ within cytoplasm. They converge on the ____ and terminate near _____. Can be ____ in dividing cells.
• Microtubules are____ composed of___ and ____.
• α and b tubulin both have a molecular weight of ___
• Tubulin subunits can ___ and form ____.
• Microtubules form the __ for many complex cytoplasmic structures including ___, ____, ____ and ____.

Answer 23

•Cylindrical tubes of tubulin in all orientations within cytoplasm. They converge on the centrosome and terminate near centrioles. Can be conspicuous in dividing cells.
•Microtubules are heterodimers composed of a and b tubulin.
•α and b tubulin both have a molecular weight of ~ 50 kDa
•Tubulin subunits can polymerize and form microtubules.
•Microtubules form the basis for many complex cytoplasmic structures including centrioles, basal bodies, cilia and flagella.
•

Question 24

Molecular Inclusions

Usually accumulated ____, that are ____.

____: ____ droplets of ___

_____: ___ deposits appearing as____ ___X____ particles (b) or ___ (a).

____: ____ of colored substances. May be ____ by ____ like ____ or come from ____. ____ one of the most common pigments.

Answer 24

Usually accumulated metabolites, transitory.

Lipids: Spherical droplets of triglyceride

Carbohydrates: Glycogen deposits appearing as single 20-30nm particles (b) or rosettes (a).

Pigments: Deposits of colored substances. May be synthesized by the cell like melanin or come from outside. Lipofuscin one of the most common pigments.

Question 25

Cell Nucleus

Main components: (4)

____ ____
____
_____
____ _____

Answer 25

Main components:

Nuclear envelope
Chromatin
Nucleolus
Nuclear matrix

Question 26

Nuclear Envelope

•Composed of _ _____ ___membranes separated by a __ __ (the ____ ____).

These membranes are ____(perm imperm) to ____and ____.
•Internal membrane closely associated with the ____. The ____ is composed of___ proteins; (____ _ _ and _). In non-dividing cells the ____ are associated with the FL.
•External membrane continuous with the ____ and ____ are attached to the outer surface.
•At the nuclear pore the inner and outer membranes ____and ____.

Answer 26

• Composed of 2 parallel unit membranes separated by a narrow space (the perinuclear cistera). These membranes are impermeable to ions and proteins.
• Internal membrane closely associated with the fibrous lamina (FL). The FL is composed of 3 main proteins; Lamins A, B, & C. In non-dividing cells the chromosomes are associated with the FL.
• External membrane continuous with the ER and polyribosomes are attached to the outer surface.
• At the nuclear pore the inner and outer membranes fuse and leave a gap.

Question 27

Nuclear Pores

• These provide pathways between the ___ and the ____.
• Nuclear pore complex is ____ in diameter and comprised of ____
• ____ and ____ can pass freely through but larger molecules and ____ require an active, ATP-dependent, process

Answer 27

• These provide pathways between the nucleus and the cytoplasm.
• Nuclear pore complex is ~ 150nm in diameter and comprised of >100 proteins
• Ions and small molecules can pass freely through but larger molecules and protein complexes require an active, ATP-dependent, process

Question 28

Chromatin I

• In ____ cells this is the chromosomes in ____.
• ___types of chromatin can be distinguished by light microscopy and EM, dependent upon the degree of uncoiling.

____: E- _____ and ____, appears as __ ___ associated with the ___ ____. _____DNA (Expressed or not)

____: ____coiled chromosomes appears as __ ___ ____ ____. Site of ____.

Cells actively synthesizing proteins have more ____ than ______.

Answer 28

• In non-dividing cells this is the chromosomes in different degrees of uncoiling.
• 2 types of chromatin can be distinguished by light microscopy and EM, dependent upon the degree of uncoiling.

Heterochromatin: Electron dense and basophilic, appears as coarse clumps associated with the nuclear lamina. Unexpressed DNA.

Euchromatin: Less coiled chromosomes appears as finely dispersed granular material. Site of active transcription.Cells actively synthesizing proteins have more euchromatin than heterochromatin.

Question 29

Chromatin II

• In ___ cells chromosomes become ___ and therefore ____ ____.
• Chromatin is composed of___ __ of dna bound to ____ ____ (____).
• Human cell in the diploid state, contains ____pairs of chromosomes (autosomes) and ___ sex chromosomes. Germ cells are ____(half number of chromosomes).
• In diploid female cells one X chromosome remains ___ while the other is ___ and ___. This inactive chromosome can be seen as the ___, a drum-stick-like nuclear appendage.

Answer 29

• In dividing cells chromosomes become supercoiled and therefore intensely staining.
• Chromatin is composed of coiled strands of DNA bound to basic proteins (histones).
• Human cell in the diploid state, contains 22 pairs of chromosomes (autosomes) and 2 sex chromosomes. Germ cells are haploid (half number of chromosomes).
• In diploid female cells one X chromosome remains euchromatic while the other is condensed and inactive. This inactive chromosome can be seen as the Barr body, a drum-stick-like nuclear appendage.

Question 30

Nucleolus

Spherical structure up to ___ in diameter.Rich in ___ and ___.

All protein components synthesized in the___. 3 components by ____.

Nuclear organizer DNA: ____ ____ coding for ___

Answer 30

Spherical structure up to 1mm in diameter.Rich in rRNA and protein. All protein components synthesized in the cytoplasm. 3 components by EM.

Nuclear organizer DNA: Base sequences coding for rRNA

Question 31

Pars Fibrosa: ___ packed ____ fibers closely associated with ____. Represent primary transcripts of rRNA genes

Pars Granulosa: :___ nm ____ representing ____

Answer 31

Densely packed ribonucleoprotein fibers closely associated with nuclear organizer DNA. Represent primary transcripts of rRNA genes

: 15-20 nm granules representing maturing ribosomes.

Question 32

Microvilli

• ____ projections (___ x ____) on the ___ surface of cells, especially ___cells where it has a thick ____.
• Microvilli plus glycocalyx= ____.
• Microvilli have an ____ core,

the actin filaments ___ from the microvillus into the ___where they form a network, called the ____.

Found in ___ to ___ for ___

Answer 32

• Fingerlike projections (1 x 0.1microm) on the apical surface of cells, especially absorptive cells where it has a thick glycocalyx.
• Microvilli plus glycocalyx = brush border.
• Microvilli have an actin core, the actin filaments extend from the microvillus into the body of the cell where they form a network, the terminal web.

Found in intestines to increase SA for absorption

Question 33

Cilia and Flagella

§Motile processes covered by ____
§Highly ___ with a similar ____ core.
§____ cilia per cell, ___ flagellum (___).
Length of each
§Core organization is ___ i.e. __ central microtubules surrounded by _____ of microtubules = an ___.
§ Protein bridges, ___, link ____ _____ ____ of ____. Each pair consists of an___ and ___ microtubule.

___, an ATPase, arms extend from __.
At the base of each cilia or flagellum is a ___ ____ which consists of microtubules arranged as in a ____

Answer 33

§Motile processes covered by cell membrane.
§Highly organized with a similar microtubular core.
§Large numbers of cilia per cell, only one flagellum (spermatozoa).
§Cilia 2-3microm long; Flagella ~100 microm long.
§Core organization is 9+2 i.e. 2 central microtubules surrounded by 9 pairs of microtubules = an axoneme.
§ Protein bridges, nexins, link adjacent peripheral pairs of microtubules. Each pair consists of an A and B microtubule. Dynein, an ATPase, arms extend from A.
At the base of each cilia or flagellum is a basal body which consists of microtubules arranged as in a centriole

Question 34

Stereocilia

A misnomer. These structures are ___, non-___, ___.

Found in the ___ and on ___ cells in the ___ (sensory).

Answer 34

A misnomer. These structures are long, non-motile, microvilli. Found in the epididymis and on hair cells in the inner ear (sensory).

Question 35

Microplicae

__ __ extensions of ___ present on ___ ____ cells e.g. ___, ____

They function to___ the ___ ___ and ___ ___ of fluids.

Answer 35

Fold like extensions of cytoplasm present on luminal epithelial cells e.g. cornea, esophagus. They function to increase surface area and surface adherence of fluids.