L4: Principles of Cell Biology Flashcards
1
Q
plasma membrane
A
- 7.5 nm thick
- lipid bilayer with 2 leaflets
2
Q
e face
A
- extracellular face
3
Q
p face
A
- protoplasmic face
4
Q
lipids make up how much of plasma membrane
A
- 35%
- phospholipids
- glycolipids
- cholesterol
5
Q
proteins make up how much of plasma membrane
A
- 60%
- integral proteins
- peripheral proteins
6
Q
carbs make up how much of plasma membrane
A
- 5%
7
Q
plasma membrane fluidity
A
- fluidity for exocytosis, endocytosis, membrane trafficking, and membrane biogenesis
8
Q
integral proteins
A
- embedded in lipid bilayer
- transmembrane proteins
- composed of hydrophilic and hydrophobic amino acids
- folded; multipass
- serve as receptors, cell adhesion molecules, cell recognition proteins, signal transduction, transport
9
Q
peripheral proteins
A
- usually located on cytoplasmic aspect of inner leaflet
- bind to phospholipids or integral proteins
- serve as electron carriers, part of cytoskeleton, part of 2nd messenger system
10
Q
nuclear envelope structure
A
- formed by outer and inner nuclear membranes
- the 2 membranes fuse to form 80 nm nuclear pores
- outer nuclear membrane continuous with RER
11
Q
nucleolus structure
A
- nuclear inclusion but not surrounded by a membrane
- observed in interphase cells that are synthesizing proteins
- contains mostly rRNA and protein as well as DNA
12
Q
function of nucleus
A
- contains genetic material encoded in DNA
- synthesizes all forms of RNA
13
Q
ribosomes
A
- formed by small and large subunits of rRNA and proteins
14
Q
two types of ribosomes
A
- free ribosomes in cytosol
- membrane-bound ribosomes
15
Q
rough ER
A
- system of membrane free sacs
- outer surface covered in ribosomes
- continuous with outer nuclear membrane
- location where membrane-packaged proteins are synthesized
16
Q
smooth ER
A
- network of tubules, vesicles, and sacs (cistern)
- varies in amount, distribution, and complexity based on cell type/fxn
- smooth-surfaced membranes
- function varies by cell
17
Q
smooth ER function hepatocytes
A
- carbohydrate metabolism - glycogen -> glucose
- degradation of lipid-soluble drugs and alcohol (via cyt P450)
18
Q
smooth ER function steroid secreting cells
A
- ovary, testis, adrenal
- lipid and lipoprotein synthesis
19
Q
smooth ER function muscle cells
A
- smooth ER = sarcoplasmic reticulum
- calcium ion regulation
20
Q
Mitochondria membranes
A
- outer membrane
- inner membrane (invaginating to form cristae)
21
Q
mitochondria spaces
A
- intermembrane compartment - between outer and inner membrane
- inner matrix compartment - flows all within cristae
22
Q
mitochondria
A
- ATP synthesis via the Krebs cycle (most enzymes in the matrix)
- contains DNA and RNA for coding some mitochondrial proteins (although many mitochondrial proteins are coded by nuclear DNA)
- produce heat (rather than energy) in brown fat cells
23
Q
where does the Krebs cycle occur
A
- mitochondrial matrix
24
Q
where the ETC occur
A
- inner mitochondrial membrane
25
cytochrome c oxidase
- important component of the electron transport chain
- defects result in severe metabolic disorders
- don't confuse with C450 in smooth ER
26
Golgi apparatus
- membrane bound cisternae (saccules) arranged in irregular-looking sacs
- two faces
27
cis face of golgi
- toward nuclear next to RER
28
trans face of golgi
- toward plasma membrane and associated with vacuoles and secretory granules
29
function of golgi
- protein modification through the addition of oligosaccharides to proteins and lipids, tagging them for delivery to vesicles and lysosomes ( processes membrane-packaged proteins synthesized in RER)
- packaging materials for secretion outside the cell
- recycles and redistributes membranes
30
lysosomes
- dense membrane-bound organelles for degrading material/cell products
- identified by staining for acid phosphatase
- possess special membrane proteins and 50 acid hydrolyses
- ATP powered proton pumps in lysosomal membrane maintain an acid pH less than 5
31
vacoule
- space or vesicle enclosed by a membrane and containing fluid
- can result from fusion of lysosomes
32
peroxisomes
- membrane-bound
- identified by a cytochemical reaction for catalase
- contains enzymes for various functions
- can sometimes be identified by a crystalloid core
33
enzyme function in peroxisomes
- oxidation of long chain fatty acids
- synthesis of cholesterol
- detoxification of ethanol
34
microtubules
- maintain cell shape
- aid in transport of macromolecule within cytosol
- assemble into the mitotic spindle
- form the core of cilia and flagella
35
intermediate filaments
- provide mechanical strength to cells
| - seen in axons and nerves
36
actin
- help cell establish focal contacts with other cells and extracellular matrix
- assist with locomotion in non muscle cells
- form contractile ring in dividing cells
- assist with folding of epithelia into tubes during development
37
What is the lipid bilayer permeable and impermeable to?
permeable: small, lipid-soluble, nonpolar molecules
impermeable: charged ions
38
Cells without a nucleus
- RBS
- platelets
- lens fiber cells in the eye
- squamous cells in epidermis
39
Where are ribosomes made?
nucleolus
40
Function of the nucleolus
- site of manufacture of ribosomal RNA with subsequent packaging into ribosomes
- very large nucleoli indicate increased rate of ribosome production (and proteins)
- large nucleoli are seen in many active cancers but can also be prominent in benign conditions characterized by high metabolic rate (tissue repair after trauma)
41
A cell with a large Golgi apparatus indicates
The cell is heavily involved in transport of material to the cell surface
42
Plasma cells that produce large amounts of immunoglobulins have what prominent organelles?
very large endoplasmic reticulum and golgi apparatus
may have large nucleoli
43
Is the nucleolus involved with DNA synthesis?
No - this is done elsewhere in the nucleus.
44
Where do proteins made on membrae-bund ribosomes go?
membrane-packaged proteins are made for secretion and export - they go to secretory vesicles, endosomes, lysosomes or the plasma membrane
45
Where do proteins made in free ribosomes go?
cytosolic and organellar proteins go to the nucleus, mitochondria or peroxisomes
46
What is I-cell disease?
"Inclusion cell" disease or mucolipidosis Type II:
- Inherited lysosomal storage disorder (Fatal in childhood)
- Failure of Goldi to phosphorylate mannose residues on glycoproteins
- Thus, lysosomal enzymes are not delivered to lysosomes and instead sent out of the cell by exocytosis - lysosomal inclusions develop.
Symptoms: coarse facial features, clouded corneas, restricted joint movement and high plasma levels of lysosomal enzymes.
47
What is Leigh's disease?
Subacute necrotizing encephalomyelopathy
- defective form of cytochrome C oxidase in the mitochondria of muscle and brain.
symptoms: intellectual deterioration, weakness, ataxia, seizures, and death at a young age.
48
Name diseases of ribosomes.
There are no known diseases of ribosomes because their function is so crucial that any problems produce death in utero.
49
What is barbiturate?
Lipid-soluble sedative for epilepsy treatment
(lethal in high doses due to respiratory depression)
Hepatocytes show a rapid increase in the amount of smooth ER in barbiturate poisoning.
In hepatocytes, smooth ER has an enzyme system (Cytochrome P450) for hydroxylation of barbiturates, making them more water-soluble and more easily eliminated.
50
Smooth ER functions in:
1. Sterol-secreting cells
2. Liver
3. Muscle cells
1. Lipid and lipoprotein synthesis (Sterol-secreting cells)
2. Degradation of lipid-soluble drugs and alcohol. Also CHO metabolism (Liver).
3. Calcium ion regulation (Muscle).
51
Bullous Pemphigoid
-Caused by antibodies against hemidesmosomes, which anchor cells to the basement membrane
Characterized by tense bullae (large blisters containing fluid) that do not rupture easily (negative Nikolsky sign) and spare oral mucosa.
52
What is Nikolsky sign
skin finding in which the top layers of the skin slip away from the lower layers when rubbed
53
What are features of Kartagener syndrome?
A variant of primary ciliary dyskinesia
Consists of (1) bronchiectasis, (2) situs inversus, (3) decreased male/female fertility ad (4) chronic sinusitis.
54
Compare and contrast cilia and microvili
Cilia: 5-10 microns, microtubules structure, moves due to dynein, functions to propel substances along a surface, located in trachea/bronchi, fallopian tube and gastrula
Microvili: 1 micron, actin structure, does not move, functions to increase surface area for absorption, located in proximal convoluted tubule cells in kidney and absorptive cells in intestine.
55
Type I collagen (synthesis, location and function)
Synthesized by: fibroblasts, osteoblasts and odontoblasts
Location: skin, tendon, bone, ligaments, cartilage and fibrocornea
Function: resist tension
56
Type II collagen
| synthesis, location and function
Synthesized by: chondroblasts
Location: hyaline cartilage
Function: resists intermittent pressure
57
Type III collagen
| synthesis, location and function
Synthesized by: fibroblasts, reticular cells, smooth muscle, Schwann cells, hepatocytes
Location: Lymphatic system, cardiovascular system, liver, lung, spleen, intestine, uterus, and endoneurium.
Function: forms structural framework in expandable organs
58
Type IV collagen
| synthesis, location and function
Synthesized by: endothelial cells, epithelial cells, muscle cells and Schwann cells.
Location: Basal lamina and external lamina
Function: Provides support and filtration; acts as scaffold for cell migration
59
Detail the intracellular and extracellular steps of Collagen synthesis.
1. In the nucleus, the DNA encoding the collagen protein is transcribed to mRNA.
2. The mRNA travels to the RER, where it is translated to make "Preprocollagen"
3. In the RER, this "Preprocollagen" is hydroxylated and glycosylated.
4. In the RER, three of these hydroxylated-glycosylated preprocollagen molecules come together to form a triple helix called "Procollagen"
5. The "Procollagen" is sent via transfer vessivles to the Trans Golgi. Addition of carbohydrates occurs in the Golgi. "Precollagen" is secreted in secretory vesicles by the trans-Golgi and guided to the cell surface along microtubules for exocytosis from the cell.
6. In the ECM, the propeptides flanking the "Procollagen" are cleaved, forming "Tropocollagen" (i.e. collagen).
7. The "Tropocollagen" molecules spontaneously self-assemble to form "Collagen fibrils"
60
Osteogenesis Imperfecta
Autosomal dominant structural defect in Type I collagen synthesis
- deficiency in T1C (found in bone and connective tissue) can lead to progressive hearing loss resulting from ossicular dislocation, stapes fixation, or fracture of the ossicles.
- patients with OI have two distinct attributes: (1) Blue Sclerae and (2) discolored teeth.
61
Symptoms of "brittle bone disease"
aka Osteogenesis imperfecta
- Genetic bone disorder
- Multiple fractures with minimal trauma
- Blue sclerae (underlying veins show through translucent tissue)
- Hearing loss (abnormal ossicles)
- Tooth abnormalities
62
How is Vitamin C important to collagen synthesis?
Vitamin C is a required co-factor for the hydroxylation of Pro (P) and Lys (K) residues.
Note: glycosylation of hydroxylysines ensues
63
Scurvy
- Vitamin C deficiency
- presents with bruising, poor wound healing a weakened immune response, bleeding gums and eventual tooth loss
- caused by synthesis of poorly hydroxylated collagen, which is unable to form either a stable triple helix or collagen fibrils.
64
Ehlers-Danlos syndrome (EDS)
Group of disorders resulting from defects in (T3/T5 collagen) synthesis/processing.
-Genetic disease
-Deficiency in type 3 (aneurysms of various vessels, organ rupture)
Deficiency in type 5 (hyperextensible skin, hypermobile joints, joint dislocation, tendency to bleed, easy bruising)
65
Vascular EDS
caused by Type III procollagen defect
characteristic skin findings, easy bruising, predisposition to rupture of hollow organs or arterial aneurysms.
66
Compare/contrasts the RER and Golgi
Rough ER:
- synthesis of membrane-packaged proteins for section/export
- addition of oligosaccharides to proteins
- recall its function for collagen
- N-linked glycosylation
Golgi:
- processing of membrane-packafed proteins synthesized in RER
- recycling and redistribution of membranes
- O-linked glycosylation
67
Type IV collagen synthesis
- unique; there is a meshwork instead of fibrils
| - contributes to basal lamina underlying epithelial cells
68
Type IV collagen disorders
Alport syndrome: affects kidneys, hearing and eyes
Goodpasture syndrome: affects basement membranes of pulmonary alveoli and renal glomeruli
69
What is Marfan Syndrome?
Results from mutations in genes encoding fibrillin - component of elastic fibers
- patients have long, slender limbs and fingers
- lens of eye dislocates, cardio problems, aorta rupture, death
