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)

Tutorial 1 Flashcards by Edan Johnston

DNA forms _% nucleus mass?

<20%

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detail types of nucleoprotein (2)

histone proteins (control coiling)

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

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structure of nuclear envelope?

double membrane

- outer lipid bilayer continuous with RER

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Chromatin appearance in non-dividing cells?

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

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Chromatin appearance in dividing cells?

chromosomes

- nucleolus absent

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how does nucleus in active cell appear?

dispersed (larger area)
pale staining euchromatin
prominent nucleoli

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how does nucleus in in-active cell appear?

small, condensed heterochromatin

- small or absent nucleoli

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mRNA?

mRNA ⇒ messengerRNA

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

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tRNA?

tRNA ⇒ transferRNA

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

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rRNA?

rRNA ⇒ ribsomalRNA

- rRNA translates AA into peptide chain

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Ribosome composition?

rRNA & protein:

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

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Where are ribsome globular subunits produced?

Nucleolar region nucleus

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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

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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)

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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

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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?

1. 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?

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

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?

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