Week 1 tute - biomedical basics Flashcards
DNA is ?% mass of a nucleus?
<20%
where are nucleoproteins synthesised?
cytoplasm
once sythesised, where are nucleoproteins transported into?
the nucleus
what are the 2 classifications of nucleoprotein
- histone proteins
- non-histone protein:
what is the purpose of histone proteins?
bind to DNA & control coiling of strand
what are the two types of non-histone proteins in the nucleus?
non-histone protein:
- enzymes for DNA & RNA synthesis
- regulatory proteins
what are the main types of RNA that can be found in the nucleus?
newly synthesised m-RNA, t-RNA & r-RNA
describe the structure of the nuclear envelope
2 lipid bilayers with intermembranous space, contains pores
what is the outer membranes of the nuclear envelope continous with?
ER (+ has ribosomes)
what is the purpose of the pores in the nuclear membrane?
permit & regulate (active) exchange of metabolites, macromolecules & ribosomal subunits between nucleus & cytoplasm
In dividing cells, chromatin appears in form of ______
chromosomes
In non-dividing cells, chromatin exists in 3 forms, they are:
- H?
- E?
- N?
- Heterochromatin-electron dense areas, of tightly coiled inactive chromatin
- Euchromatin-pale staining areas of DNA, active in synthesising RNA (e.g. m-RNA)
- Nucleolus:
•one or more in active cells
• site of r-RNA synthesis & ribosome assembly
what is heterochromatin?
electron dense areas, of tightly coiled inactive chromatin
what is euchromatin?
pale staining areas of DNA, active in synthesising RNA (e.g. m-RNA)
what is the nucleolus?
site of r-RNA synthesis & ribosome assembly, there are one or more within active cells
what is the difference in the appearance of the nucleus between inactive and highly active cells?
- inactive cells have small nuclei, condensed (hetero) chromatin, small or absent nucleoli
- highly active cells have dispersed (pale staining) chromatin (euchromatin) with prominent nucleoli
role of mRNA?
transcribes DNA instructions for protein synthesis & carries to cytoplasm
role of rRNA?
moves to cytoplasm becomes site of protein synthesis, it translates mRNA sequence into sequence of amino acids
role of tRNA?
transfers amino acids in sequence, from pool in cytoplasm, to elongating polypeptide chain being assembled
the cytosol (fluid matrix) colloidal solution contains? (list 6 things)
– water
– electrolytes
– suspended proteins
– neutral fats
– glycogen
– pigments
at what region in the nucleus are ribosomes assembled at?
the nucleolar region within nucleus
where does the synthesis of extracellular proteins occur? (e.g. digestive enzymes, some hormones, neurotransmitters)
Rough endoplasmic reticulum
what synthesises proteins to be used within the cell?
free ribosomes in the cytoplasm
describe the structure of the ER
a system of paired membranes with matrix (fluid-filled space), cisternae (flattened sacs) & vesicles connecting parts of inner cell
what is the matrix of the ER continuous with?
- cell membrane
- space between 2 layers of nuclear membrane
- other membranous organelles
the ER functions as tubular __________ _________ for transport of molecules through cell
the ER functions as tubular communication network for transport of molecules through cell
the ER’s large surface area & attached multiple ________ ______ means it has an active role in ___ ______
the ER’s large surface area & attached multiple enzyme systems means it has an active role in cell metabolism
where is the main site of structural modification for the following enzymes?
–pancreatic digestive enzymes
–liver plasma proteins
–lysosomal enzymes (all cells)
RER
what is the main function of RER?
protein synthesis and structural modification for specific functions
smooth endoplasmic reticulum is continuous with ___?
rough endoplasmic reticulum
_______ endoplasmic reticulum contains enzymes for:
- lipid, lipoprotein, steroid synthesis
- regulation of intracellular calcium (skeletal & cardiac muscle)
- detoxification of lipid-soluble drugs (liver)
- glycogen storage
smooth
describe the structure of the Golgi apparatus
stacks of 4 or more thin flat membranous sacs, located near (concave surface facing) nucleus
the Golgi apparatus ______ substances & packages into _______ vesicles, which move into cytoplasm, fuse with cell membrane then leave via ________
the Golgi apparatus modifies substances & packages into secretory vesicles, which move into cytoplasm, fuse with cell membrane then leave via exocytosis
________ either within lumen of coated vesicle or embedded within its membrane are transported to Golgi from ER
proteins, either within lumen of coated vesicle or embedded within its membrane are transported to Golgi from ER
______ _______ may produce some of the larger CHOs that combine with proteins in RER to form glycoproteins
Golgi Complex (apparatus) may produce some of the larger CHOs that combine with proteins in RER to form glycoproteins
list the three functional parts of the Golgi apparatus
i) Cis face (faces nucleus):
ii) Medial Golgi
iii) Trans Golgi network
functions of cis face of Golgi apparatus?
- receives transport vesicles from SER
- phosphorylates certain proteins
function of medial Golgi
adds sugar residues to both lipids & peptides to form complex oligosaccharides
function of trans Golgi network
- performs proteolytic steps
- adds sugar residues
- sorts different macromolecules & directs to correct vesicles
the mitochondria are?
FUCK YES
cristae of inner mitochondrial membrane have
- 3.
- cytochromes
- carrier molecules of ETC
- enzymes for oxidative phosphorylation & ATP production
_____ mitochondrial membrane is permeable, with enzymes for lipid catabolism
outer mitochondrial membrane is permeable, with enzymes for lipid catabolism
mitochondrial ______ has enzymes for CAC and fatty acid oxidation
mitochondrial matrix has enzymes for CAC and fatty acid oxidation
how many mitochondria can a hepatogyte have?
2,000 - aka a lot
how many of their own constituent proteins do mitochondria synthesise?
37
what kind of abnormalities can result from abnormal mitochondrial DNA?
- structural abnormalities of muscle
- structural abnormalities of nervous system
- metabolic abnormalities from failed oxidative metabolism
Clinical patterns caused by Mitochondrial Cytopathic Syndromes include?
extraocular muscle weakness, degenerative disease of CNS, metabolic disturbances e.g very high levels of lactic acid
how would you diagnose Mitochondrial Cytopathic Syndromes
muscle biopsy & microscopic examination
what is a lysosome?
a membrane bound veiscle containing acidhydrolases and proteoenzymes
the enzymes contained within lysosomes are synthesised in ___ then packed into vesicles in _____
synthesised in RER, packed into vesicles in Golgi
what is the optimal pH for the enzymes within a lysosome?
5.0
what happens if lysosomal contents leak out into the cytoplam?
they become less effective due to the higher cytoplasmic pH
What is a type 1 lysosome?
A lysosome who’s enzymes have not yet begun the digestive process
what is a type 2 lysosome?
a phagolysosome (endolysosome) - foms when type 1 lysosome fuses with the substrate material, the enzymes become activated & chemical degradation process begins
what are the 2 ways in which a type 2 lysosome can form?
i) autophagocytosis: worn-out cell parts for recycling
ii) heterophagocytosis: ingested bacteria in phagosome
what are residual bodies?
type 2 lysosomes with undigested material, e.g.
- lipofuscin (age pigment in neurons, cardiac muscle)
- carbon particles in lung & tattoo pigments in macrophages (last decades)
what is autolysis?
release of enzymes into cytoplasm, massive destruction of cell contents (abnormal)
how do neutrophils work on bacteria?
release enzymes from type 1 lysosomes into extracellular spaces, destroy surrounding cells – e.g. purulent inflammatory lesions
what is the effect of lysosomal storage (inherited) diseases?
specific enzymes are absent or inactive, digestion of e.g. cerebrosides, gangliosides, sphingomyelin doesn’t occur
e.g. Tay Sachs disease (autosomal recessive)
what do peroxisomes do?
- contain special reducing enzyme that degrades peroxides e.g. H2O2
- function in control of free radicals which, if not degraded, will damage other cytoplasmic molecules
- contain enzymes for catabolism of very long-chain fatty acids (C 18 & above)
- formation of bile acids in liver cells
give examples of peroxisomal disorders
–defects in enzymes which process long chain fatty acids –metabolic disturbances e.g. acidosis
–storage of abnormal lipids
• e.g. adrenoleukodystrophy resulting in impaired oxidation of fatty acids >> abnormal lipid storage in brain, spinal cord and adrenals >>intellectual deterioration (dementia), adrenal failure
what are the three classes of cytoskeleton filaments?
– Microfilaments
– Intermediate filaments
– Thick myosin filaments
what are microfilaments?
- e.g. actin
- present in superficial zone of cytoplasm in most cells” cytoplasmic & membrane movement in endocytosis, exocytosis
- in microvilli of e.g. intestine
what are intermediate filaments?
• heterogeneous group diameter (?nm)
• support & maintain asymmetric cell shape
– e.g. keratin in keratinocytes,
– e.g. glial filaments in astrocytes
give an example of thick myosin filaments
in muscle, also temporarily in other cells
what are cytoskeleton microtubules made of?
tubulin
give 3 functions of cytoskeleton microtubules
– development & maintenance of cell form
– intracellular transport
– basic structure for some complex organelles e.g. centrioles, cilia, flagella, spindle fibres
cytoskeleten microtubule abnormalities can lead to? (2 things)
- alterations in cell mobility & function e.g. diabetes
- altered leukocyte migration interferes with inflammatory response
what is colchicine used in?
it binds to tubulin affecting the microtubule/cytoskeleton structure. used in:
- treatment of gout
- halting chromosomes on equator in mitosis, for cytogenetic studies
FINISH SLIDES ON CELL MEMBRANE
