Cell pathology lecture 2-3 Flashcards
What is homeostasis?
The way internal variables are kept in a normal range
Give the order of negative feedback
Stimulus->variable->receptor senses change ->Control centre compares to normal value -> Effectors make adjustments against reference value ->effectors make variable normal
List some of the determinants of cell viability:
Protection from environment, nutrition, communication, energy generation, movement, renewal of senescent/old molecules, molecular catabolism
What are the purposes of the mitochondria?
ATP generation, source of intermediates for metabolism, haem production, apoptosis regulators
What is the warburg effect
Cancer cells do not break down sugar completely, only completing glycolysis
What do cell membrane proteins & glycoproteins do?
Ion & metabolite transport,
Fluid phase & receptor mediated uptake of macromolecules,
Cell ligand, cell matrix and cell-cell interactions
What molecules can move though membranes by passive diffusion?
Oxygen, Carbon dioxide, water, urea, alcohol, steroids
How does water move passively?
Via osmosis
What causes water to move into/out of cells?
High extracellular salt: water goes into cells. Hypotinic extracellular: Water comes out
How do polar molecules >75 daltons and ions move across membranes?
Channel (fast) proteins or carrier (slower) proteins
what is needed for passive transport?
A concentration gradient
What are the 2 types of endocytosis and which is vitamin uptake done by?
Caveolae mediated and receptor mediated (Vitamin is caveolae)
What is transcytosis?
Movement of endocytosed vesicles between basolateral and apical aspects of the cell.
Involved in vessel wall permeability, movement of antibodies from breast milk though babys intestinal cells
What is an example of receptor-mediated endocytosis?
LDL cholestero luptake
WHat are the four main components of the cytoskeleton
Actin microfilaments, intermediate filaments, microtubules, lamin
What joins adjacent cells?
Desmosomes
What joins cells to epithelial matrix?
Hemi-desmosomes
What makes rough ER rough?
It is studded with ribosomes
What does sER do?
Cyclical release and storage of calcium ions for muscle contraction
What happens in Endoplasmic reticulum itself?
Proteins fold
What are lysosomes and proteosomes involved in?
Waste disposal. Lysosomes contain acid hydrolases, proteosomes recycle senescent or misfolded proteins
How do mitochondia mediate cells
Mediate oxidative phosphorylation. Rapidly growing cells do this very quickly
What occurs in the intermembrane space of mitochondia?
ATP synthesis
What is autocrine communication?
sending the message to the own cell, occurs during cell development or to amplify a response
What is paracrine communication?
Another cell in the viscinity signals a cell. Growth factors can act via this way
What does endocrine mean
A mediator is released into the bloodstream, travelling to a distant target. Includes FSH
What are the signals cells respond to?
Pathogens, damage to neighbouring cells, contact with neighbouring cells, contact with extracellu;ar matrix, secreted molecules such as growth factors, cytokines or hormones
What happens once a ligand binds to a receptor?
An ion channel can open
A G-protein is activated
Tyrosine kinase can activate
or latent transcription factor can activate
What are G-protein receptors?
They trigger G-proteins which are attached to inner aspect of membrane, triggering a response
What does p53 do
it is a transcription factor activating genes causing growth arrest
What are the 5 possible purposes of growth factors
Stimulate activity of proteins needed for cell survival/growth/division,
Promote cells to enter cell cycle,
relieve blocks on cell cycle progression, prevent apoptosis, enhance systhesis of cell components
What does the extracellular matrix do?
Support anchorage, polarity and migration,
Controls cell proliferation via growth factors and integrin signalling,
Scaffolding for tissue nenewal, estabishment of tissue microenvironments
What makes up the extracellular matrix?
Collagen and elastin for structure, proteoglycans and glycoproteins
What are the stages of the cell cycle?
G1 (duplicates organelles, chromosome replication begins)
S (DNA replicated)
G2 (Growth continues, enzymes and other proteins, chromosome replication continue)
Mitosis
What are totipotent stem cells?
They can differentiate to all cell types
What tissues can adult stem cells replace
Only the tissue in which they reside
What are the two important properties of stem cells?
Self renewal and asymmetric division (2 daughter cells, one a replica, the other can differentiate)
What can damage cells?
Oxygen deprivation, physical agents, chemicals/drugs, infectious agents, immune reactions, genetic abnormalities, nutritional imbalances
What cell injuries are reversible?
Cell swelling, fatty change, eosinophilia, cell membrane blebbing, mitiochondiral swelling, dilation of ER with ribosome detatchment, chromatin clumping
What is hypertrophy?
Increase in size of cells, increasing size of organ. Pathological (myocardium in hypertension) or physiological (Muscle, uterus), increased workload
What is hyperplasia?
Increase in number of cells in response to stimulus. Can be pathological or physiological
What is atrophy?
The reduction in organ size/tissue due to decrease in cell size and number (eg uterus post birth)
What are the 6 types of pathological atrophy
Disuse, denervation, diminished blood suppky, inadequate nutrition, loss of endocrine stimulation, pressure
What is metaplasia?
A reversible change where one differentiated cell type is replaced by another type
What can squamous cells differentiate to in lower oesophagus in response to acid reflux?
Goblet cells
What are the 3 outomes of a cell following irreversible injury?
Necrosis, apoptosis, necroptosis + pyroptosis
What is necrosis?
Unregulated cell death with lysosomal enzyme digestion of membranes and cell leakage. Inflammatory
What causes necrosis?
Infection, ischaemia, toxins, trauma
What mechanisms underly cell imjury in necroisis?
ATP depletion, mitochondiral damage, influx of calcium, oxygen derived free radicals, membrane permeability defects, DNA and protein damage.
What does an influx of calcium do in cells?
activates enzymes destroying cell, Opens mitochondrial permeability transition pores: depletes ATP
What is apoptosis
Highly regulates, programmed cell death caused by protein/DNA damage. No loss of membrane integrity or inflammation
What occurs in apoptosis
Cell shrinkage, chromatin condensation, formation of apoptotic blebs and apoptotic antibodies, phagocytosis by macrophages.
What is the intrinsic mitochondiral pathway of apoptosis?
Cellular injury, DNA damage or decreased hormona; stimulation inactivates BCL2, allows cytochrome C to activate caspases. Caspase 9 initiates
Describe the extrinsic receptor-ligand pathway of apoptosis
FAS ligand binds to CD95 receptor on target cell, activating caspases. TNF binds to receptor to do the same, Caspases 8 and 10 initiate
What molecule flips from inner to outer membrane to be recognised by macrophages?
Phosphatidylserine
