Cell and Organelles Flashcards
Tissues vs. organs
• Tissues – group of cells with similar properties that perform specific function
o Epithelium
o Connective tissue proper
Specialized – cartilage, bone, fat, blood
o Nerve
o Muscle
• Organs – structures comprised of different tissues that collectively carry out specific function
plasma membrane structure and function
• Plasma Membrane Structure – Fluid Mosaic Model o Unit membrane – phospholipid bilayer o Asymmetrical o Fluid • Plasma Membrane Function o Separate o Barrier o Transport/exchange o Constancy o Recognition
phospholipid bilayer
o Amphipathic
Nonpolar fatty acid hydrocarbon tails
Polar charged head groups
o Asymmetrical
o Glycocalyx striated border = glycocalyx + microvilli
Glycocalyx – carbohydrate chains that vary at the surface of the membrane
cholesterol
– necessary ingredient for membranes
o Cholesterol stiffens the membrane and reduces the permeability
Can be temporary or permanent
o Impairment in neuronal membranes indicated in Alzheimer’s and Autistic spectrum disorders
o Essential component of myelin
o Required for brain growth, differentiation, preservation
o Keeps membrane architecture stable
Failures in homeostasis contribute to progressive neurodegeneration
Participates in membrane raft microdomain composition – sites of protein signaling clusters
proteins
o Peripheral – noncovalent interactions; changing the salt concentration of environment can affect these proteins
o Integral – stronger interactions
o Transmembrane
membrane transport - endocytosis
Fluid-phase pinocytosis – cell membrane invaginates to form a pit
Receptor-mediated endocytosis
Phagocytosis – extension of pseudopodia from the cell that engulf particles and then internalize the material
Clathrin-mediated endocytosis – energy dependent and highly regulated
• Receptor-mediated endocytosis
• Sequestration of receptors
• Synaptic vesicle recycling
• Co-opted by viruses for host entry
Intracellular Clathrin-coated vesicles
• Mediate protein transport
• Mediate lipid transport
membrane transport - exocytosis
Fusogenic proteins – energy dependent; fuse with outer membrane to excrete products extracellularly
Increase in Ca+
Malfunctioning Clathrin-coated pits
o Huntington’s Disease
Nerve cells in brain waste away resulting in altered cellular physiology and peripheral pathologies
Genetic defect that presents in middle age
Presentation – uncontrolled movements and loss of balance
Late stages – loss of mobility, can’t talk/swallow, poor memory
o Familial Hypercholesterolemia – unable to remove LDL “bad cholesterol”; high levels in blood
Genetic – autosomal dominant, familial condition
Coronary disease at early age
• Atherosclerosis (narrowing arteries)
• Angina
Histopathology
• Narrowing of arteries
• Atherosclerosis – plaque deposits with lipid core and fibrous cap
nucleus and nuclear envelope
• Nucleus – “brain” of the cell; controls eating, movement, and reproduction
• Nuclear Envelope
o 2 parallel membranes
o Fibrous lamina made of lamins A, B, C provide skeleton framework for the nuclear envelope
myoclonic epilepsy associated with ragged-red fibers (MERRF)
o Presentation – myoclonic seizures, ataxia, muscle weakness
o Histopathology
Massive subsarcolemmal
Proliferation of dysfunctional mitochondria
endoplasmic reticulum
– site of translation of mRNA into proteins o Rough ER Segregate proteins NOT destined for cytosol Post-translational modification o Smooth ER Synthesize phospholipids Neutralize noxious substances Steroid synthesis Muscle cell contraction
golgi apparatus
o Finishes post-translational modifications
o Packages and concentrates
o Addresses proteins for delivery
Packages proteins in specific way depending on where they are destined to go
lysosomes
o Intracellular digestion and turnover of cellular components
Tay-Sachs
o Early and late onset o Presentation Hypotonia and muscle weakness Impaired thinking Blindness and deafness o Histopathology GM2 gangliosidosis Accumulation in lysosomes
peroxisomes
o Oxidize organic substances with catalase
H2O2 decomposed to H2O and O2 via catalase
Degrade ethyl alcohol, drugs, toxic molecules
Beta-oxidation of long fatty acid chains
Zellweger’s syndrome
– cerebrohepatorenal syndrome
o High levels of long chain fatty acid and bile acid intermediates
o Presentation – seizures; eye defects
o Histopathology – low catalase in peroxisomes
proteasomes
– only removes proteins that have been tagged with ubiquitin
o Digest specific proteins targeted for destruction with the aid of ubiquitin (Ub)
o Ub is conjugated to targeted proteins through ATP-dependent, enzymatic pathway
o Ub-activating enzyme (E1) transfers Ub to Ub-conjugating enzyme (E2), then Ub is covalently transferred to the targeted substrate protein
o Altered Ub enzymatic pathway contributes to several diseases
ubiquitin-dependent proteolysis impacts
o Cell cycle progression
o Transcription
o Receptor endocytosis
o Signal transduction
cervical cancer
o 3rd most common form of cancer in women
o Healthy cells are transformed by oncogenic form of HPV (16 and 18)
o Early cancer – no signs or symptoms
o Late cancer – bloody vaginal discharge; pelvic pain
o Caused by: dysregulated Ub-dependent proteolysis – HPV cellular machinery promotes ubiquitination (removal) of cell’s tumor suppressor protein (p53)
o Histopathology
Squamous cell carcinoma epithelial lining
Adenocarcinoma glandular tissue
Cancer cells obliterate the normal epithelial structure
cytoskeleton
o Function – structural Proteins that provide shape for a cell o Components Microtubules Actin and myosin Intermediate filaments
microtubule structure and function
o 24 nm diameter
o Heterodimer of alpha and beta tubulin
o Polymerize into spiral of 13 units per turn
o Polymerization is asymmetrical and calcium dependent – growing end (+) and subtracting end (-)
• Microtubule Function – intracellular transport of organelles
actin structure and arrangements
o 5-7nm diameter
o Thin filament with globular subunits arranged as a double helix
Polymerization is Ca+ dependent
• Actin Arrangements
o Paracrystalline array with myosin
o Cell cortex – thin sheath beneath cell membrane
o Organelles – cytoplasmic streaming
o Cytokinetic apparatus – separates daughter cells
o Scattered in the cytoplasm
sickle cell anemia
o Presentation – fatigue, shortness of breath, dizziness, headaches
o Histopathology
Defective hemoglobin
Distorted RBC bears sickle shape
Actin/spectrin cytoskeleton locks; RBC is less deformable
Sickle cells obstruct the microcirculation
intermediate filaments
– can be used to identify cancer based on presence of certain types of intermediate filaments o 10-12nm o Keratin – epithelium o Vimentin – embryonic mesenchyme o Desmin – smooth muscle and Z disks o Glial (GFAP) – astrocytes
duchene’s muscular dystrophy
o Presentation – muscle weakness; apparent lack of coordination; progressive crippling, fixations (contractures) of the muscles around joints; loss of mobility
o Histopathology
Disrupted dystrophin gene
Abnormal dystrophin cannot anchor cytoskeletal elements to plasma membrane
Lack of structural support leads to permeable membrane and intracellular pressure rises resulting in cell “exploding”
mitosis
o Interphase – duplicate centrosomes and centrioles
o Prophase – mitotic spindle MOC (mitotic operating center) migration
o Metaphase – chromosomes migrate to center upon the MOC arriving at midline of cell
Microtubules grow to reach the chromosomes in center
o Anaphase – chromatids migrate to opposite poles
Microtubules break down in order to pull
o Telophase and Cytokinesis – cell divides
Intermediate filaments involved
