L2: Cell Biology I

Question 1

List three cellular constituents. Describe briefly

Answer 1

1. ) Organelles: structural elements conferring functional attributes to cell. These and are membranous and non-membranous
2. ) Inclusions: nonliving entities found in cytoplasm and nucleus – stored food, pigements and crystalline
3. ) Cytoplasmic matrix / cytosol: portion of cytoplasm devoid of organelles and inclusions – typically about 50+% of volume of cell

Question 2

Compare and contrast cytoplasm and cytosol

Answer 2

• Cytoplasm: part of cell external to nucleus that suspends organelles and inclusions
• Cytosol/cytoplasmic matrix: portion of cytoplasm devoid of organelles and inclusions

Question 3

List general groups of cellular inclusions

Answer 3

• Stored foods
• Pigments
• Crystalline

Question 4

Types of stored foods in cells? Location?

Answer 4

• Glycogen: stored in liver and striated muscles (skeletal and cardiac) cells
• Fat: found in adipocytes, hepatocytes, muscles and steroid-secreting cells

Question 5

What conditions cause accumulation of stored food inclusions within the cell?

Answer 5

• Glycogen accumulation = glycogen storage diseases eg. McArdle disease
• Lipid accumulation = lipid storage disease and fatty liver

Question 6

What is McArdle disease? Symptoms/signs?

Answer 6

• Genetic defect in muscle phosphorylase resulting in accumulation of glycogen and inability to degrade it.
• S&S: cramping with exercise, exercise intolerance, myoglobin elevated with strenuous exercise, CK elevated, venous lactate level doesn’t increase with exercise

Question 7

List exogenous and endogenous pigments found in cells

Answer 7

1. ) Exogenous
   a. ) Carotene
   b. ) Inhaled dust/carbon particles
   c. ) Tattoo pigments
2. ) Endogenous
   a. ) Hemoglobin
   b. ) Hemosiderin
   c. ) Bilirubin
   d. ) Melanin
   e. ) Lipofuscin

Question 8

List of exogenous pigments

Answer 8

• Carotene
• Inhaled/carbon dust particles
• Tattoo pigments

Question 9

What is carotene? Condition associated with excessive amounts?

Answer 9

• Fat-soluble pigment that imparts yellow-orange color

- Carotenemia

Question 10

Where are inhaled dust/carbon particles found? Condition associated with this?

Answer 10

• Macrophages in lungs phagocytize dust

- Anthracosis is accumulation of carbon particles in lungs and regional lymph nodes. Harmless

Question 11

What is anthracosis?

Answer 11

• Accumulation of carbon particles in lungs and regional lymph nodes. Harmless

Question 12

Where are tattoo pigments stored?

Answer 12

• Macrophages of dermis

Question 13

List of endogenous pigments

Answer 13

• Hemoglobin
• Hemosiderin
• Bilirubin
• Melanin
• Lipofuscin

Question 14

What is hemosiderin? Color? Location? Clinical relevance?

Answer 14

• Iron-containing pigment
• Color = brown
• Found in macrophages of spleen and liver
• Clinical relevance = hemosiderosis, hemochromatosis, heart failure cells

Question 15

What is hemosiderosis?

Answer 15

• Increased deposition of hemosiderin in tissues and organs

- Seen with: increased absorption of iron in diet, impaired use of iron by body, hemolytic anemias and transfusions

Question 16

What is hemochromatosis?

Answer 16

• Severe accumulation of iron (compared to hemosiderosis) due to a genetic defect resulting in excessive iron absorption or transfusion

Question 17

What are heart failure cells?

Answer 17

• Macrophages indicative of CHF

Question 18

Color of bilirubin pigement? When is it seen elevated?

Answer 18

• Yellow-brown pigment

- Elevated in liver and biliary disease, skin and sclera appear yellow – known as jaundice (icterus)

Question 19

3 types of melanin. Color, location, function/clinical relevance

Answer 19

1. ) Eumelanin
   - Color: brown-black pigment
   - Location: membrane-limited granules in epidermis and pigment layer of retina
   - Function/relevance: 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
   - Color: black-brown pigement
   - Location: neurons, including substantia nigra and locus coeruleus, found in membrane-limited neuromelanin granules
   - Function/relevance: putative neuroprotective function, depigmentation of dopa cells located in substantia nigra of pts with Parkinson’s disease
3. ) Phaeomelanin
   - Color: red pigment
   - Location: hair
   - Function/relevance: responsible for red hair color, not protective against UV radiation

Question 20

What is lipofuscin? Color? Location? Function/clinical relevance?

Answer 20

• Aka lipochrome pigment, aka wear and tear pigment, aka aging pigment
• Color: brownish-yellow pigment that is amalgam of lipids, metals and organic molecules
• Location: accumulates in long-live cells like neurons and cardiac/skeletal muscle cells
• Function/relevance: accumulation is a measure of cellular stress and is observed in severe malnutrition and cachexia

Question 21

Where are crystalline inclusions found?

Answer 21

• Cells of Leydig (crystal of Reinke) of testis

- Sertoli (inclusion of Charcot-Bottcher) cells of testis

Question 22

3 types of lipids in plasmalemma

Answer 22

• Aka plasma membrane
  1. ) Phospholipids (most abundant)
  2. ) Glycolipids
  3. ) Cholesterol

Question 23

Function of cholesterol

Answer 23

• Strengthen lipid bilayer and make it less deformable. Less permeable to small, water-soluble molecules

Question 24

What are lipid rafts? Clinical relevance?

Answer 24

• Lipid rafts are small areas in membranes where sphingolipids and cholesterol are concentrated. These are involed in cell signaling.
• Some CA cell types have greater concentration of cholesterol, which correlates with more lipid rafts. Simvastatin (cholesterol inhibitor) has been shown to induce apoptosis by reduction in raft formation in CA cells via down regulation of Akt (cell survival signaling molecule).

Question 25

When is increased eumelanin seen in cells clinically? Absence?

Answer 25

• Increased production in response to UV radiation
• Increased in Addison’s disease in response to elevated ACTH
• Absent in albinos

Question 26

What pigment is implicated in Parkinson’s disease?

Answer 26

• Neuromelanin contained in membranes within dopa cells in substantia nigra

Question 27

What is the aging pigment? Where is it stored?

Answer 27

• Lipofuscin

- Accumulates in long-live cells like neurons and cardiac/skeletal muscle cells

Question 28

What is a nuclear inclusion body?

Answer 28

• Presence of nuclear inclusion is indicative of disease such as CMV infection

Question 29

28-yo male complains of muscle pain, fatigue within a few minutes of exercise. Continuation of exercise leads to muscle spams. He mentions that his urine is dark after colored spams. Lab studies and tests revealed elevated CK, absence of myophosphorylase activity and lack of lactate production during and ischemic forearm test.

a. ) What is the name of this disorder?
b. ) Why the myoglobinuria?
c. ) Why is CK elevated?
d. ) Why is lactate production absent?
e. ) What is the cytoplasmic inclusion seen in the following image? What stain is appropriate?

Answer 29

a. ) McArdle’s (glycogen storage disease)
b. ) Necrosis of muscle and myoglobin
c. ) Lysis/breakdown of muscle tissue
d. ) No CHO precursor in order to produce lactate, glycogen isn’t degraded
e. ) Glycogen. Stained with PAS reaction