Tutorial 1 Flashcards
DNA forms _% nucleus mass?
<20%
detail types of nucleoprotein (2)
- histone proteins (control coiling)
2. non-histone proteins (enzymes for synthesis DNA/ RNA, regulatory proteins)
structure of nuclear envelope?
- double membrane
- outer lipid bilayer continuous with RER
Chromatin appearance in non-dividing cells?
- euchromatin (active synthesizing RNA, pale)
- heterochromatin (tightly coiled & inactive)
- nucleolus present
Chromatin appearance in dividing cells?
- chromosomes
- nucleolus absent
how does nucleus in active cell appear?
- dispersed (larger area)
- pale staining euchromatin
- prominent nucleoli
how does nucleus in in-active cell appear?
- small, condensed heterochromatin
- small or absent nucleoli
mRNA?
mRNA ⇒ messengerRNA
- DNA is transcribed into mRNA → new copy of genes - mRNA moves out nucleus → cytoplasm → protein synthesis - original DNA in-tact
tRNA?
tRNA ⇒ transferRNA
- tRNA transfers correct AA from cytoplasm to ribosome, according to mRNA
rRNA?
rRNA ⇒ ribsomalRNA
- rRNA translates AA into peptide chain
Ribosome composition?
rRNA & protein:
2 globular proteins of unequal size, each consisting of rRNA strand and associated ribosomal proteins
Where are ribsome globular subunits produced?
Nucleolar region nucleus
Ribosome location - how does location effect function?
- Free ribosomes
- scattered singly or polyribosomes
- synthesis intracellular proteins
- Rough ER
- is attached to normal ER
- synthesis extracellular proteins
ER general structure
System of paired membranes consisting of:
- A matrix (fluid filled space), which is continuous with nuclear envelope, plasma membrane and other organelles
- cisternae (flattened sacs)
- vesicles (connect parts inner cell)
What does RER produce?
- 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
What does SER produce?
- 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
3 functional parts golgi apparatus?
- Cis face → faces nucleus
- receives transport vesicles from SER
- phosphorylates certain proteins
- Medial golgi
- adds sugar residues to lipids/ peptides → form complex oligosaccharides
- Trans golgi network
- performs proteolytic steps
- adds sugar residues
- sorts macromolecules, directs to correct vesicles
Golgi apparatus function?
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
Mitochondria composition - how does inner and outer membrane differ?
- 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
Explain what’s meant by mitochondrial cytopathic syndromes?
- 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
Clinical patterns of mitochondrial cytopathic syndromes?
- extraocular muscle weakness
- degenerative CNS disease
- metabolic disturbance (high lactic acid)
Diagnosis of mitochondrial cytopathic syndromes?
muscle biopsy -> examination
lysosome composition?
- membrane bound small vesicles
- contain
- 40 different acid hydrolases (ie. acid phosphatases), and
- proenzymes (intracellular digestion)
how are lysosomes formed?
lysosome enzymes are synthesized RER → packed into vesicles in golgi → lysosome formed
Types of lysosomes?
1* (primary) = enzymes inactive
2* (phagolysosomes) = primary fuses with a substrate and enzymes activated
Residual bodies = phagolysosomes with undigested material, ie. lipofucsin & carbon particles
how may a 1* lysosome become a 2* lysosome - what substances may be processed?
- autophagocytosis → warn out cell parts recycled
2. heterophagocytosis → ingested bacteria
state an inheritable pathology related to lysosomes?
lysosomal storage diseases
Tay sach’s disease:
a. ) how does it occur?
b. ) what kind of pathology is it?
Tay sach’s disease:
a.) absence or inactivity of lysosome enzymes → improper digestion of → cerebrosides, gangliosides, sphingomyelin
b.) autosomal recessive pathology
Peroxisomes location and function?
- 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)
Peroxisomal disorders lead to?
- 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
3 classes of cytoskeleton filaments, with examples?
- microfilaments (ie. actin)
- present superficial zone of cytoplasm
- located in microvilli, ie. large intestine
- involved in cytoplasmic and membrane movement
- Intermediate filaments
- heterogenous group diameter
- support and maintain asymmetric cell shape
- ie. keratin (in keratinocytes), glial filaments (astrocytes)
- thick myosin filaments
- ie. in muscle, but also temporarily in other cells
what are microtubules made of?
tubulin
microtubule function?
- develop and maintain cell form
- intracellular transport
- basic structure for complex organelles (ie. centrioles, cilia, flagella etc)
State clinical applications of microtubules?
- use of colchicine in gout
- halting chromosomes on equator of mitosis
- cytogenic studies
cell membrane functions?
- 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
cell membrane composition?
- 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
state special membrane structures?
- microvilli
- membrane junctions
- tight
- desmosomes
- gap junctions
- cellular extensions
- cilia
- flagella
