-
nLight microscopy (LM)
- oLimit of resolution ~0.2 µm (200 nm) (~ x 1,000)
- oStudy organs, tissues, cells
- oTwo dimensional
-
nTransmission electron microscopy (TEM)
- oLimit of resolution ~1.0 nm (~ x 50,000)
- oStudy cell structures
- oTwo dimensional
-
nScanning electron microscopy (SEM)
oThree dimensional image
-
Metric system
- o1,000 nm = 1 µm
- o1,000 µm = 1 mm
- o10 mm = 1 cm
- o1,000 mm = 1 m
- o100 cm = 1 m
- o1,000 m = 1 km
- o2.5 cm = 1 inch (English system)
- oAverage sheet of paper = 96.5 µm, or 0.0038 inches
-
Cell sizes
- oRed blood cells (rbc’s) are a ubiquitous reference, ~7.5 µm
- o“typical cells” are ~20-50 µm in diameter
-
A prototypical (standard) cell’s major constituents
- oPlasma membrane
- oCytoplasm
- oNucleus
-
Plasma membrane (PM)?
- oA.k.a. cell membrane, plasmalemma
- oSemipermeable membrane between interior of cell and extracellular (interstitial) fluid (ECF)
- oComponents
- nLipids
- nProteins
- nCarbohydrates
-
Membrane lipids
- oPhospholipids
- nAmphipathic
- oPolar phosphate head (water soluble, hydrophilic)
- nPolar = uneven distribution of charge
- oNonpolar lipid tail (water insoluble, hydrophobic)
- oPhospholipid bilayer
- oSeparates extracellular and intracellular fluids
-
Membrane proteins
- oIntegral proteins – embedded within the phospholipid bilayer.
- nMay form hydrophilic channels or transporters across membranes
- nMay include receptors
- oCell-cell recognition
- oSignal transduction
- oPeripheral proteins – on inner or outer membrane surface
-
Transport across plasma membranes
- oPassive transport
- nDoes not require energy (ATP)
- nFrom high concentration to low concentration (down concentration gradient)
- oActive transport
- nRequires energy (ATP)
- nMovement against concentration gradient
-
Passive transport
- oSimple diffusion – movement from high to low concentration until equilibrium is reached
- nSmall and/or nonpolar molecules (O2,CO2)
- oOsmosis – diffusion of water (e.g., in salty water rbc’s will shrink)
- oFacilitated diffusion – use of transporter proteins, e.g., glucose diffusion
- o
-
Active transport
- oTransport against a concentration gradient (from low to high concentration) requiring ATP
- oIon pumps – e.g., for Na+, K+, Ca++
- oBulk transport
- nExocytosis of secretory vesicles (secretion)
- nEndocytosis
-
Endocytosis
- oPhagocytosis – pseudopodia extend and engulf a particle
- oPinocytosis – incorporation of droplets of ECF
- oReceptor-mediated endocytosis – receptors bind specific molecules for more efficient uptake
-
Major structural components of cells
- oPlasma membrane
- oCytoplasm
- oNucleus
-
Cytoplasm
- oCytosol (cytoplasmic matrix, intracellular fluid) – water + solutes
- oOrganelles
- nMembrane-bound – ER, Golgi apparatus, lysosomes, mitochondria
- nNonmembrane-bound – ribosomes, cytoskeleton, cilia & flagellae, microvilli
- oInclusions
- nStorage droplets, usually nonmembrane-bound
- nPigment, glycogen, triglycerides
-
Endoplasmic reticulum (ER)
- oRough ER (rER)
- nCisternae + ribosomes
- nProtein synthesis
- oCell export (secretion)
- oMembrane insertion
- oLysosomes
- oSmooth ER (sER)
- nCisternae w/o ribosomes
- nSynthesis of lipids, metabolism of carbohydrates,
- detoxification
-
Golgi apparatus (Golgi complex)
- oCisternae
- oProtein modification, intracellular transport and packaging, sorting
-
Lysosomes
- oMembrane-bound sacs
- nFormed by Golgi apparatus (enzymes made in rER)
- nContain digestive enzymes to break down waste products and ingested material (enzymes: proteins that catalyze (facilitate) metabolic reactions)
-
Mitochondria
- oOuter and inner membrane
- nCristae
- nMatrix
- nContain mitochondrial DNA (maternal)
- oMitochondria produce ATP (adenosine triphosphate – contains high energy chemical bond)
-
Ribosomes
- oMade of RNA (ribonucleic acid)
- oMade in nucleus (nucleolus)
- oResponsible for protein synthesis
-
Cytoskeleton
oProteins arranged as microfilaments, intermediate filaments, or microtubules; functions - movement, shape.
-
Actin cytoskeleton
- oActin microfilaments made visible by ultraviolet fluorescence
- oNote the network of actin fibers
- oActin seen in skeletal muscle cells
-
Cilia & flagella
- oBoth cilia and flagella are composed of microtubules surrounded by cytoplasm and plasma membrane
- nCapable of movement, consuming ATP
- oCilia are numerous and are on the surface of some body cavities; transport mucus (e.g., trachea)
- oFlagella occur only
- on sperm
- oVisible with LM
- (light microscope)
-
Microvilli
- oComposed of cytoplasm and plasma membrane in the shape of numerous, thin fingers (Fig 26.15e)
- oMuch smaller than cilia
- nNot visible with LM
- Increase surface area for absorption (not motile
-
Nucleus
- oStructure
- nNuclear envelope – double membrane structure around nucleus (DNA)
- oNuclear pores allow movement between nucleus and cytoplasm
- Nucleoli – site of synthesis of RNA for ribosomes (dark staining; visible with LM)
-
Chromosomes
- oChromatin and chromosomes – DNA and proteins
- oDuring cell division (mitosis), DNA molecules condense into tightly packed chromosomes
- oDNA=deoxyribonucleic acid
-
The cell cycle
- oInterphase + mitosis
- oInterphase DNA: heterochromatin
- oMitosis DNA: chromosomes
-
Mitosis (mitotic cycle)
- oProduces two identical daughter cells (clones)
- nGrowth and development
- nReplacement of tissue
- nTissue repair
- oInterphase – cell growth, DNA replication
- oProphase – DNA forms chromosomes
- oMetaphase – chromosomes line up
- oAnaphase – chromosomes divide and separate
- oTelophase – two new cells begin to develop
- oCytokinesis – cell division
- o
- o
-
Cancer
- oFaulty control of mitosis
- oUncontrolled cell division
- oMalignant neoplasms – uncontrolled cell growth that spreads (metastasis)
- oCancer cells trigger new blood vessel formation - angiogenesis
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