Tutorial 1

Question 1

DNA forms _% nucleus mass?

Answer 1

<20%

Question 2

detail types of nucleoprotein (2)

Answer 2

1. histone proteins (control coiling)

2. non-histone proteins (enzymes for synthesis DNA/ RNA, regulatory proteins)

Question 3

structure of nuclear envelope?

Answer 3

• double membrane

- outer lipid bilayer continuous with RER

Question 4

Chromatin appearance in non-dividing cells?

Answer 4

• euchromatin (active synthesizing RNA, pale)
• heterochromatin (tightly coiled & inactive)
• nucleolus present

Question 5

Chromatin appearance in dividing cells?

Answer 5

• chromosomes

- nucleolus absent

Question 6

how does nucleus in active cell appear?

Answer 6

• dispersed (larger area)
• pale staining euchromatin
• prominent nucleoli

Question 7

how does nucleus in in-active cell appear?

Answer 7

• small, condensed heterochromatin

- small or absent nucleoli

Question 8

mRNA?

Answer 8

mRNA ⇒ messengerRNA

- DNA is transcribed into mRNA → new copy of genes
- mRNA moves out nucleus → cytoplasm → protein synthesis
- original DNA in-tact

Question 9

tRNA?

Answer 9

tRNA ⇒ transferRNA

- tRNA transfers correct AA from cytoplasm to ribosome, according to mRNA

Question 10

rRNA?

Answer 10

rRNA ⇒ ribsomalRNA

- rRNA translates AA into peptide chain

Question 11

Ribosome composition?

Answer 11

rRNA & protein:

2 globular proteins of unequal size, each consisting of rRNA strand and associated ribosomal proteins

Question 12

Where are ribsome globular subunits produced?

Answer 12

Nucleolar region nucleus

Question 13

Ribosome location - how does location effect function?

Answer 13

1. Free ribosomes
   
   • scattered singly or polyribosomes
   • synthesis intracellular proteins
2. Rough ER
   
   • is attached to normal ER
   • synthesis extracellular proteins

Question 14

ER general structure

Answer 14

System of paired membranes consisting of:

1. A matrix (fluid filled space), which is continuous with nuclear envelope, plasma membrane and other organelles
2. cisternae (flattened sacs)
3. vesicles (connect parts inner cell)

Question 15

What does RER produce?

Answer 15

• ribosomes attached → extracellular protein synthesis
• produces:
  
  • pancreatic digestive enzymes
  • liver plasma proteins
  • lysosomal enzymes (all cells)
  • integral unit membrane proteins
    
    • proteins fold into secondary structure, form intra-chain disulphide bonds
  • involved in first step glycosylation

Question 16

What does SER produce?

Answer 16

• no ribosomes, continuous with RER
• enzymes for:
  
  • lipid, lipoprotein and steroid synthesis
  • regulation intracellular calcium (in muscle)
  • detoxification lipid soluble drugs (in liver)
  • glycogen storage

Question 17

3 functional parts golgi apparatus?

Answer 17

1. Cis face → faces nucleus
   
   • receives transport vesicles from SER
   • phosphorylates certain proteins
2. Medial golgi
   
   • adds sugar residues to lipids/ peptides → form complex oligosaccharides
3. Trans golgi network
   
   • performs proteolytic steps
   • adds sugar residues
   • sorts macromolecules, directs to correct vesicles

Question 18

Golgi apparatus function?

Answer 18

in association with ER…

• modifies and packages substances → secretory vesicles → cytoplasm → exocytosis
• proteins from ER → golgi within vesicles
• produce large CHOs → combine proteins (from RER) → glycoproteins

Question 19

Mitochondria composition - how does inner and outer membrane differ?

Answer 19

• elongated double membrane
  
  • outer → permeable with enzymes for lipid catabolism
  • inner → has cristae containing cytochromes, carrier molecules of ETC, enzymes for oxidative phosphorylation
• matrix → enzymes citric acid cycle, fatty acid oxidation
• circular DNA strands & ribosomes → synthesize 37 of own proteins

Question 20

Explain what’s meant by mitochondrial cytopathic syndromes?

Answer 20

• mDNA maternal only → mitochondria in spermatozoa jettisoned at fertilization (penetration zona pellucida)
• abnormal mDNA → 37 genes for mitochondrial structure are located within mDNA, so this means impaired mitochondria → structural abnormalities of:
  
  • muscle system
  • nervous system
  • metabolic abnormalities (failed oxidative phosphorylation)
• severity depends on proportion mDNA effected

Question 21

Clinical patterns of mitochondrial cytopathic syndromes?

Answer 21

• extraocular muscle weakness
• degenerative CNS disease
• metabolic disturbance (high lactic acid)

Question 22

Diagnosis of mitochondrial cytopathic syndromes?

Answer 22

muscle biopsy -> examination

Question 23

lysosome composition?

Answer 23

• membrane bound small vesicles
• contain
  
  • 40 different acid hydrolases (ie. acid phosphatases), and
  • proenzymes (intracellular digestion)

Question 24

how are lysosomes formed?

Answer 24

lysosome enzymes are synthesized RER → packed into vesicles in golgi → lysosome formed

Question 25

Types of lysosomes?

Answer 25

1* (primary) = enzymes inactive 2* (phagolysosomes) = primary fuses with a substrate and enzymes activated Residual bodies = phagolysosomes with undigested material, ie. lipofucsin & carbon particles

Question 26

how may a 1* lysosome become a 2* lysosome - what substances may be processed?

Answer 26

1. autophagocytosis → warn out cell parts recycled | 2. heterophagocytosis → ingested bacteria

Question 27

state an inheritable pathology related to lysosomes?

Answer 27

lysosomal storage diseases

Question 28

Tay sach's disease: a. ) how does it occur? b. ) what kind of pathology is it?

Answer 28

Tay sach's disease: a.) absence or inactivity of lysosome enzymes → improper digestion of → cerebrosides, gangliosides, sphingomyelin b.) autosomal recessive pathology

Question 29

Peroxisomes location and function?

Answer 29

- contain enzyme degrading peroxides (H2O2) - control free radicals (otherwise they damage cytoplasmic molecules) - contain enzymes → catabolism long chain fatty acids (>18C) - formation bile acids in liver cells an organelle found in cytoplasm (similar to lysosome)

Question 30

Peroxisomal disorders lead to?

Answer 30

- defects in enzymes catabolizing long chain fatty acids - metabolic disturbances (acidosis) - storage abnormal lipids - impaired oxidation fatty acids → abnormal lipid storage in brain/ SC/ adrenals → intellectual deterioration (dementia) & adrenal failure ⇒ adrenoleukodystrophy

Question 31

3 classes of cytoskeleton filaments, with examples?

Answer 31

1. microfilaments (ie. actin) - present superficial zone of cytoplasm - located in microvilli, ie. large intestine - involved in cytoplasmic and membrane movement 2. Intermediate filaments - heterogenous group diameter - support and maintain asymmetric cell shape - ie. keratin (in keratinocytes), glial filaments (astrocytes) 3. thick myosin filaments - ie. in muscle, but also temporarily in other cells

Question 32

what are microtubules made of?

Answer 32

tubulin

Question 33

microtubule function?

Answer 33

- develop and maintain cell form - intracellular transport - basic structure for complex organelles (ie. centrioles, cilia, flagella etc)

Question 34

State clinical applications of microtubules?

Answer 34

1. use of colchicine in gout 2. halting chromosomes on equator of mitosis 3. cytogenic studies

Question 35

cell membrane functions?

Answer 35

- semipermeable (selective) → - cross membrane transport - generate and maintain membrane potential - seperate intracellular and extracellular environment - receptors for hormones/ molecules - regulates cell growth and proliferation - role in behaviour cancer cells

Question 36

cell membrane composition?

Answer 36

- phospholipid bilayer - small amounts → cholesterol, glycolipids - intrinsic (integral) proteins, mostly transmembrane - allow passage small charged ions - extrinsic (peripheral) proteins, channels - glycocalyx → - glycolipid and glycoprotein - highly specific biological markers

Question 37

state special membrane structures?

Answer 37

- microvilli - membrane junctions - tight - desmosomes - gap junctions - cellular extensions - cilia - flagella