Ch.2 The Cell

Question 1

Histones

Answer 1

one of a number of simple proteins (often found in the cell nucleus) that contains a high proportion of basic amino acids, are soluble in H2O, dilute acids and alkalis, and do not coagulate by heat.

Question 2

Heterochromatin

Answer 2

• condensed chromatin
• peripheral chromatin
  
  • nucleolus associated chromatin
• gene transcription is suppressed

Question 3

Euchromatin

Answer 3

• extended chromatin
• nonstaining region
• site of DNA transcription

Question 4

Nucleolus

Answer 4

• exclusive site for syn of rRNA
• components:
  
  • pars granulosa-light part, rRNA to join with
  • pars fibrosa-more dense, location of newly synthesize
  • nucleolar organizer regions

Question 5

Centrioles

Answer 5

small, cylindrical structure w/ 9 bundles of microtubules

• arranged in bundles of three (triplets)
• replicate during cell cycle (G2)
• forms mitotic spindle

Question 6

2 stages of cell cycle:

1. Mitosis (1-1.5 hrs)
2. Interphase

Answer 6

2. G1 phase: 8 hours
   S phase: 7-8 hours
   G2 phase 4 hours

Question 7

Nuclear matrix

Answer 7

karyoskeletal network of fibrils in the interior of the nucleus.
-not generally accepted

Question 8

Nonmembranous organelles

5

Answer 8

• Ribosome
• Microtubules
• Centrioles
• Cilia and flagella
• filaments

Question 9

Membranous organelles

10

Answer 9

• Cell membrane
• mitochondria
• rough ER
• Golgi ap
• secretory vesicles
• lysosomes
• coated vesicles
• endosomes
• peroxisomes
• smooth ER

Question 10

inclusions

Answer 10

• nonliving.
• consists largely of secretory vesicles, pigment granules, neutral fat, other lipid droplets, and glycogen
• for stored foods:
  
  • carbs-glycogen
  • fat
• for pigments:
  
  • exogenous
    - carotene-orange pigment
    - carbon particles
  • endogenous
    - Hemoglobin
    - Hemosiderin-brown
    - Bilirubin-yellow
    - melanin-brown to black
    - lipofuschin-wear and tear pigment

Question 11

microtubules

Answer 11

• slender unbranched tubules of tubulin
• like railroad tracks of cell, along which vesicular movement occurs
• movement of cilia and flagella
• during mitosis and meiosis
• cell elongation and migration
• maintenance of cell shape
• motor proteins: dynein(-) and kinesins(+)
• main structural components of centrioles, mitotic spindles, cilia and flagella

Question 12

Cytoplasmic filaments (threadlike)
3 classes:
1.micofilaments
2.thick filaments
3. intermediate filaments

Answer 12

• thinner, shorter, more flexible than microtubules
• functions:
• anchorage and movement of membrane proteins
• formation of the structural core of microvilli
• locomotion
• extension of cell processes
• components of contractile elements of muscle cells
  1. made up of actin
  2. composed of myosin
  
  • myofibrils-in muscle cells
  • stress fibers-bundles of microfilaments in the superficial zone of cytoplasm just under cell membrane
  • microvilli-in absorptive cells, supported by cross-linked bundles of microfilaments
    
    3. -keratin -vimentin -desmin -neurofilaments -glial filaments
  • structural role in the cytoplasmic link of a tissue-wide continuum of cytoplasmic, nuclear, and extracellular filaments
  • rod-shaped
  • extend across desmosomes/hemides

Question 13

Cytoplasmic matrix(cytosol)
2 functional domains

Answer 13

1. central domain-few supporting intermediate filaments

2. peripheral domain-dense meshwork of actin microfilaments