Cell Biology

Question 1

Hemotoxylin Staining

Answer 1

blue stain; carries a + charge;
binds to negatively charged structures (PO4-2 in DNA, RNA; SO4-2 in cartilage)
Example: nucleus & rER appear blue (basophilic)

Question 2

Eosin Staining

Answer 2

red stain; carries a – charge; 
adheres to amine groups (NH3+) on proteins;
 cytoplasmic filaments (e.g., actin & myosin), intracellular membranous components (mitochondria, sER), most extracellular fibers (e.g., collagen) 
appear pink (eosinophilic/acidophilic).

Question 3

Euchromatic vs. Heterochromatic

Answer 3

Euchromatic: nucleus is light staining and larger because chromosomes are less coiled for transcription

Heterochromatic: nucleus is dark staining and smaller because chromosomes are more coiled and not transcriptionally active

Question 4

rER

Answer 4

site of protein synthesis
Free ribosomes and free polyribosomes – synthesize intracellular proteins

rER are flattened interconnected sacs which are the site for protein synthesis; leave nucleus through the pore and the mRNA can either be bound to rER membranes and then make three classes of proteins

rER assembles 3 classes of proteins:

1. secretory proteins
2. integral membrane proteins
3. lysosomal enzymes

Question 5

Secretion of Glycoproteins

Answer 5

rER – protein synthesis

Golgi – adds sugars

Vacuole –buds off Golgi, fuses with cell membrane

Question 6

Golgi Apparatus Functions

Answer 6

A. Modification of proteins via:

1. Glycosylation
2. Sulfation
3. Phosphorylation of lysosomal enzymes (mannose-6-P)
4. Proteolysis of proproteins

B. Secretory products via

1. Packing
2. Concentration
3. Storage

Addition of mannose-6-phosphate targets that enzymatic protein to a lysosome.

Question 7

Plasma Cells

Answer 7

Constitutive secretion of immunoglobulins by plasma cells – proteins NOT stored in secretory granules but secreted immediately after their synthesis

Plasma cells that make Ab with Golgi that are pale staining because flattened stacks of membranes
As soon as the secretory products are synthesized, they are immediately released = constitutive secretion
Regulated: secretory proteins will be stored and will not be released unless receive a signal to do so

Question 8

sER

Answer 8

Synthesis of lipids and membrane phospholipids and cholesterol

Synthesis of steroid hormones (testosterone, estrogen, etc)

Enzymes that control glycogen breakdown

Enzymes that detoxify drugs

Question 9

sER in Steroid Secreting Cells

Answer 9

spongy looking= spongiocytes

Characteristics:

1. lots of lipid droplets
2. Highly developed sER
3. Mitochondria with tubular cristae

Question 10

Residual Bodies

Answer 10

Residual Bodies = lysosomes w/ undigestible material
Residual bodies are late-stage lysosomes that are retained by long-lived cells (ex., nerve cells and muscle), engaging over and over in digestive activity, growing large and more heterogeneous in content, and over time becoming lipofuscin granules.

Lipofuscin Granules = residual bodies in neurons, muscle, liver

Question 11

Endocytosis

Answer 11

movement of substances into the cell

Pinocytosis is a subtype: movement of fluid and small soluble proteins

Phagocytosis is a subtype: non specific ingestion of large particles such as bacteria, cellular debris, etc.; only in special cells like macrophages and neutrophils by extending pseudopods

Question 12

Cytoskeletal Elements

Answer 12

A. Microtubules: in cilia, flagella, cytoplasm

B. Microfilaments (actin): in microvilli, stereocilia, cytoplasm

C. Intermediate filaments: in cytoplasm

Question 13

Cilia and Flagella

Answer 13

core of microtubules in 9 + 2 arrangement;

move fluid over cells; found in trachea, oviducts

Question 14

Microtubules

Answer 14

Rigid hollow tubes of the protein tubulin
~ 20-25 nm in diameter
Rapidly disassemble in one place, reassemble elsewhere
Alternating a and b subunits of tubulin arranged to form 13 protofilaments
Polar : (+) end is growing end to which tubulin dimers bound to GTP are added; nongrowing (-) end
Disrupted by colchicine to stop vesicular transport

Question 15

Microfilaments

Answer 15

Made of Actin

1. Form the structural core of microvilli: non-motile; increase surface area for absorption
2. Form the terminal web, a robust scaffold; helps maintain the shape of the apical surface
3. Cytokinesis – a “purse-string” ring of actin filaments associated with myosin constricts, resulting in cleavage of mitotic cells
4. Formation of cytoplasmic pseudopods for phagocytosis
5. Extension of growth cones, filopodia, and lamellipodia, for ex., used in migration of transformed cells of invasive tumors

Question 16

Microfilaments Structure

Answer 16

G-actin (globular): free actin molecules in the cytoplasm

F-actin (filamentous): actin polymerized into a filament; ~ 6 nm diameter

Polar: fast-growing end is called +; slow-growing end is called –

Enzymatic activity: once g-actin is incorporated into f-actin, it hydrolyzes ATP ADP

In non-muscle cells, MFs readily dissociate and reassemble.

Actin-binding proteins (ABPs) can prevent or enhance polymerization.

Question 17

Intermediate Filaments

Answer 17

10-12 nm in diameter;

Unlike MTs and MFs, IFs are nonpolar (no growing end) and have no enzymatic activity, no ATPase or GTPase activities
Two will coil together to make a coiled dimers and then the dimers associated with each other to form a tetramere; 8 tetramers will become cross linked to each other

Question 18

Monoclonal Ab

Answer 18

Monoclonal antibodies are often used in
pathology to identify the tissue origin of tumors; e.g., cells from an adenocarcinoma would be cytokeratin-positive but desmin-negative.

Intermediate filaments: only certain filaments will be found in certain tissues
Desmin is only in muscle cells
Vimentin in mesodermal origin
Cytokeratins in epithelial
Neurofilament in neural tissue
Glial fibrillary acid protein in glial cells only
This is how we can use an Ab to a filament so we can find the origin of the tumor

Question 19

Free Polyribosomes and Free Ribosomes

Answer 19

Polyribosomes can either be attached to the rough ER or free in the cytosol. If they are free, they synthesize proteins that are used within the cell. Free ribosomes do that too. On the other hand, ribosomes or polyribosomes that are attached to the rER synthesize proteins that are destined for exocytosis, lysosomes, or membranes.