Cell Biology I

Question 1

Cellular constituents–3 of them

Answer 1

Organelles, inclusions, cytoplasmic matrix(cytosol)

Question 2

Organelles

Answer 2

i. Structural elements that confer functional attributes to the cell
ii. Membranous and non-membranous organelles exist

Question 3

Inclusions

Answer 3

– nonliving entities found in the cytoplasm and nucleus. Inclusions are characterized as stored food, pigments, and crystalline in composition and are typically not bound by a membrane.

Question 4

Cytoplasm

Answer 4

Part of the cell enternal to the nucleus, suspends organelles and inclusions

Question 5

Cytosol

Answer 5

portion of the cytoplasm devoid of organelles and inclusions

Question 6

Stored foods

Answer 6

Stored foods (proteins are not stored in the cytoplasm as inclusions)

i. Glycogen (polymer of glucose: occurs in clusters or discrete particles)
a. Liver and striated muscle cells (skeletal and cardiac) contain abundant glycogen
b. Demonstrated by the PAS reaction
c. Clinical significance – glycogen storage diseases
1. McArdle disease is due to a genetic defect in muscle phosphorylase and is specific to skeletal muscle. Accumulations of glycogen under the sarcolemma (plasma membrane of muscle) are observed. Symptoms include cramping with strenuous exercise, exercise intolerance, myoglobin elevated with strenuous exercise, creatine kinase is elevated, and venous lactate level does not increase with exercise.
ii. Fat (lipid) droplets
a. For example, found in adipocytes, hepatocytes, muscle, and steroid-secreting cells
b. Accumulation in lipid storage diseases and fatty liver (alcoholic and nonalcoholic)

Question 7

Pigments

Answer 7

Exogenous and Endogenous pigments

Question 8

Exogenous pigments

Answer 8

a. Carotene
1. Fat-soluble pigment that imparts a yellow-orange color
2. Carotenemia (reversible condition)
b. Inhaled dust (carbon particles) - Macrophages in the lungs phagocytize the dust – Anthracosis is an accumulation of carbon particles in lungs and regional lymph nodes. Condition is harmless.
c. Tattoo pigments are stored in macropahges of the dermis

Question 9

Endogenous pigments

Answer 9

Hemoglobin, hemosiderin, bilirubin, melanin, lipofusion

Question 10

Hemoglobin pigment

Answer 10

cyanosis and myoglobin

Question 11

Hemosiderin

Answer 11

1. Iron containing pigment
2. Brown color
3. Found in macrophages of the spleen and liver
4. Translation to clinical relevance
   a) Increased deposition of hemosiderin in tissues and organs is termed hemosiderosis
   b) Hemosiderosis is seen with: increased absorption of iron in diet; impaired use of iron by the body; hemolytic anemias; transfusions
   c) Hemochromatosis – a more severe accumulation of iron due to a genetic defect resulting in excessive iron absorption or transfusion
   d) Heart failure cells (macrophages) – congestive heart failure

Question 12

Bilirubin

Answer 12

1. Yellow-brown pigment
2. Elevated in liver and biliary disease, for example
3. Skin and sclera appear yellow – jaundice (icterus)

Question 13

Melanin

Answer 13

1. Eumelanin
   a) Brown-black pigment
   b) Found in membrane-limited granules in the epidermis and pigment layer of retina.
   c) Increased production in response to UV radiation and increased in Addison’s disease in response to elevated ACTH. Absent in albinos due to an absence of tyrosinase
2. Neuromelanin
   a) Black-brown pigment found in neurons. The most pigmented areas in the brain are the substantia nigra (black substance) and locus coeruleus.
   b) Membrane-limited neuromelanin granules
   c) Putative neuroprotective function
   d) Depigmentation of dopaminergic cells in nerve cells located located in the substantia nigra of patients with Parkinson’s disease
3. Phaeomelanin (skin and hair)
   a) Red pigment
   b) Responsible for red hair color
   c) Not protective against UV radiation

Question 14

Lipofusion

Answer 14

Lipochrome pigment

1. Brownish-yellow pigment that is an amalgam of lipids, metals, and organic molecules (aka “wear and tear’ and aging pigment)
2. Accumulates in long-lived cells
   a) Neurons
   b) Cardiac and skeletal muscle cells
3. Accumulation is a measure of cellular stress and is observed in severe malnutrition and cachexia

Question 15

Crystalline inclusions

Answer 15

have been found in the cells of Leydig (crystal of Reinke) and Sertoli (inclusion of Charcot-Böttcher) cells of the testis.

Question 16

Plasmalemma (plasma membrane)

Answer 16

A. The dynamic organelle that separates the cell’s internal environment from its external environment
B. Represents only a small fraction (2 to 5%) of the total membrane of a cell
C. 7.5 to 10 nm thick (visible with electron microscopy only)
D. Lipid bilayer (contains three types of lipids)

Question 17

Lipid bilayer (3 types of lipids)

Answer 17

i. Phospholipids (most abundant)
ii. Glycolipids
iii. Cholesterol
a. There may be up to one molecule of cholesterol for every phospholipid molecule
b. Cholesterol strengthens the lipid bilayer and makes its less deformable. Consequently, the lipid bilayer is less permeable to small, water-soluble molecules.

Question 18

Lipid rafts

Answer 18

small areas (50 nm in diameter) in membranes where sphingolipids (glycosphingolipid and sphingomyelin) and cholesterol are chiefly concentrated. As this raft region is thicker and molecularly unique from the rest of the membrane, certain membrane proteins will aggregate. The raft proteins are involved in cell signaling (e.g., apoptosis and cell proliferation). Thus, a lipid raft microdomain is a signaling platform.

Question 19

Clinical relevance of lipid rafts

Answer 19

some cancer cell types have greater concentrations of cholesterol which correlates with more lipid rafts. A cholesterol inhibitor, simvastatin, has been shown to induce apoptosis by a reduction in raft formation. A reduction in raft numbers down regulates the cell survival signaling molecule, Akt (a protein kinase). Restoration of cholesterol promoted Akt activity.