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Cell anatomy
- looks at parts
- like looking at a car engine that's not working
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Cell physiology
- looks at function
- like looking at how the car runs
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Body fluids
- intracellular
- extracellular
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Intracellular body fluids
- 90-94% water
- majority of fluid is contained within cell membranes
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Extracellular body fluids
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Interstitial fluid
- within tissues
- fluid/serum that leaks out when you skin your knee
- think of this as the humidity in the air in your house
- in order to move stuff from blood into cell, must travel through interstitial fluid
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Plasma
- within the blood vessels
- think of this as water in the pipes of your house
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Body fluid compartments
- extracellular fluid
- intracellular fluid
- solid matter
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Extracellular body fluid compartment
- 20% of body weight
- joint fluid
- fluid in stomach and intestines
- plasma
- fluid surrounding brain
- lymph fluid
- interstitial fluid
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Intracellular body fluid compartment
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Solid matter body fluid compartment
- 40% of body weight
- tissue matter
- bone
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Fluid regulation
- plasma membranes
- semi-permeable barrier
- - some things can get in, some can't
- ions
- - tend to be things that can get in
- - cations
- - anions
- - electrolytes
- -- salts
- -- acids
- -- bases
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Passive membrane processes
- require no cellular energy (ATP)
- 4 types:
- - diffusion
- - facilitated diffusion
- - osmosis
- - filtration
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Diffusion
- inherent molecular motion
- concentration gradient
- diffusion in biological systems
- selectively permeable membranes (plasmalemma)
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Inherent molecular motion
- - aka Brownian motion
- - kinetic energy
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Concentration gradient
- movement of molecules from areas of high concentration to areas of low concentration
- because of inherent molecular energy and reach equilibrium
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Diffusion in living systems
- think of this as huge open archway
- governed by
- - molecular size
- - lipid solubility
- - molecular charge
- rate
- facilitated diffusion
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Molecular size
small molecules diffuse readily across plasma membrane
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Lipid solubility
- phospholipid bilayer
- alchols, steroids, and gases are highly lipid soluble and readily diffuse
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Molecular charge
- charged particles require channels to pass through membranes
- eg sodium, potassium, chloride ions
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Rate
- limited by number of carriers or channels present
- fever increases rate of reactions
- cold (hypothermia) slows everything down
- anesthesia is all about delivering chemicals across the plasma membrane in one direction or the other
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Facilitated diffusion
- utilites integral proteins to provide a means of passage for large or charged particles to pass freely through the membrane
- think of this as a small door
- each cell has its own varieties of integral proteins to determine that can go in and out
- large molecules require action of integral proteins to permit diffusion
- channel proteins are like a door
- carrier proteins are like a turnstyle
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Osmosis
- special form of diffusion of water across a semi-permeable membrane
- specifically the movement of water molecules from areas of high concentration to areas of low concentration
- water moves readily across membranes until equilibrium is reached
- water and solutes tend to move in opposite directions
- in homeostasis, the concentration of water molecules inside of cells is equal to the concentration outside the cells
- solutes can be different, but water molecules are the same
- don't give pure water IV as water would rush in and cell would burst
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Osmotic flow
movement of water molecules from areas of high concentration to areas of lower concentration
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Osmotic pressure
the force of the movement of water molecules
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Tonicity
- isotonic
- hypertonic
- hypotonic
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Isotonic medium
- cells structure will remain the same
- picture a normal RBC
- give isotonic fluids IV (isotonic to what is normally in cell), eg 0.9% NaCl
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Hypertonic medium
- cells will collapse in on themselves
- picture a crenallated (spiky) RBC
- crenallated => dehydrated
- need water for Kreb's cycle, so as you get dehydrated, cells will not function
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Hypotonic medium
- cell will expand and, possibly, burst
- picture RBC as a ball
- sometimes will give this initially in severe dehydration to speed recovery, eg 0.45% NaCl
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Oncotic pressure
- difference between the osmotic pressure of bloos and the osmotic pressure of the interstitial fluids
- - big molecules pulling stuff in
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Hydrostatic pressure
- liquids (interstitial fluid) pulling stuff out
- the force that pushes liquid through membranes
- generated by beating heart
- the rest is from thefreedictionary.com:
- - the pressure in the circulatory system exerted by the volume of blood when it is confined in a blood vessel.
- - The hydrostatic pressure, coupled with the osmotic pressure within a capillary is opposed by the hydrostatic and osmotic pressure of the surrounding tissues.
- - Fluids flow from the higher pressure areas to the lower pressure areas.
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Filtraton
- requires a pressure gradient, eg heart beat (BP)
- molecules are pushed through the membrane due to differences in pressure on either side
- molecules that would not normally pass, may
- really important in kidneys
- by the time you can diagnose kidney disease, 75% of nephrons are not functioning correctly
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Active membrane processes
- requires ATP to assist movement of molecules across cell membranes
- relies on carrier proteins
- works against the concentration gradient
- Na+, K+, Mg+, Ca+ actively transport across cell membranes
- - eg more potassium needed in cell for electrical activity
- Cl-, I-, Fe2+ trasport across specialized cells, eg thyroid
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Uniport
one substance moves in one direction
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Symport
- more than one substance moves in one direction
- sometimes, must be together
- eg proton pump and sucrose-H+ cotransporter work together to form a symport
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Antiport
- some substances move in and some move out
- - eg sodium potassium pump - 3 NA, 2 K
- - need more K in cells than out for muscle contraction, nerve impulses
- - sodium diffuses in to cell down concentration gradient, usually drags in water
- - that's why BP goes up when eat salt
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Cytosis
active transport requiring ATP
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Endocytosis
- moves material into the cell
- non-specific - takes everything
- - phagocytosis - cell eating
- - pinocytosis - cell drinking
- -- when drink orally, osmosis not enough to move water, so large int?? cells take chunks of water to move in
- -- macrophages will drink harmful fluids like botulin toxin
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Phagocytosis
- phagosomes
- - ameboid motion of pseudopodia
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Pinocytosis
- - tiny infolding of the plasma membrane
- - fluid released into the cytoplasm
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Receptor mediated endocytosis
- specific proteins act as specialized receptors
- ligands bind to these receptors
- coated pit forms
- receptor molecule is recycled
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Exocytosis
- moves material out of cell
- - excretion
- - secretion
- - both processes very similar
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Excretion
- removal of waste products
- - eg urine
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Secretion
- export of cell manufactured molecules
- - eg ear wax
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Resting membrane potential
- there is a charge inside and outside each cell
- membrane potential = Voltage
- all cells maintain a membrane potential, -20 to -200 millivolts
- EKG measures this in the heart
- negative charge
- - is on the inside of the plasma membrane
- - is negative relative to the extracellular fluid
- electrons move toward positive pole
- cells are like little batteries
- sodium potassium pump maintains negative charge bu releasing 3 Na for each 2K that come back in
- irritable cells - conductive - muscle and nerve
- change polarity to allow flow of information
- epithelial and connective tissues not conductive
- electricity runs through a cell
- to bridge the gap between cells, chemicals are released which bond to the next cell and change its electrical gradient
- neurotransmitters are chemical switches to turn on/off electrical gradient
- - eg dopamine, nicotine, caffeine, morphine, acetylcholine
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Voltage
the potential electrical energy created by the separation of opposite charges
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Life cycle of the cell
- somatic cells divide by mitosis
- produce 2 genetically identical daughter cells
- in juveniles, all cells are mitotically active
- cells reproduce to maintain body tissues, heal wounds and enable growth
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Somatic cell
all cells in the body exclusive of the reproductive cells (sperm and eggs)
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Interphase
- the period between cell divisions
- historically called the resting phase
- now referred to as the metabolic phase - when cell is doing most of its regular work
- nucleus and nuceoli visible
- DNA arranged as loose chromatin strands
- divided into 3 phases:
- - Growth 1
- - Synthesis
- - Growth 2
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Growth 1 phase
- most active phase
- lasts for variable periods depending on the nature of the cell
- - minutes to years
- - muscle & nerve cells in adult are long term
- - cells in mouth are replaced every 24-36 hours
- intensive metabolic activity
- cell growth - small amount
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Synthesis phase
- DNA replication occurs
- new histones are produced
- - cell is working for itself now
- chromatin is assembled
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Growth 2 phase
- very brief
- enzymes and proteins required for cell division are produced
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DNA replication
- must occur before cell division can proceed
- intricate multistep process that is not fully understood
- helicase breaks the hydrogen bonds between bases (unzips)
- primase forms DNA on the leading strand
- polymerase forms DNA on lagging strand
- ligase joins fragments (replaces RNA) on lagging strand
- only does this during synthesis phase
- rest of the time DNA is active in protein synthesis
- estrogen is trigger for bone cells to reproduce
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Protein synthesis
- during G1 phase - normal maintenace
- during G2 phase - stuff for new cell
- doesn't require entire DNA strand to unravel to make a protein
- RNA polymerase causes DNA to open at the specific gene needed
- creates messenger RNA (mRNA) from gene
- mRNA exits nucleus
- nucleoli also forms tRNA, rRNA & ribosome exits nucleus
- ribosome attaches to mRNA
- tRNA brings amino acids to ribosome
- attach to each other to form polypeptide which forms protein (goes to ER, folds it, then Golgi apparatus to be packaged)
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Anticodon
3 base code for one amino acid
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Transcription
- DNA -> mRNA
- inside nucleus
- genes - sections of DNA that code for a specific protein (only 10% codes for protein)
- replicaton begins at the start signal or promoter
- RNA polymerase encourages binding of mRNA to DNA
- 3 RNA nucleotides form a codon
- each codon represents a different amino acid
- ends when reach the terminator code
- spliceosomes remove introns
- small ribonucleic proteins splice the exons back together
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Introns
non-informational triplets of DNA
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Extrons
informational triplets of DNA
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Translation
- nucleic acid (mRNA) -> amino acid
- outide nucleus
- mRNA binds to a ribosome and protein synthesis begins
- tRNA docks to the larger ribosomal unit's active site
- tRNA contains an anti-codon and an amino acid binding site
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Mutation
- a genetic error
- sometimes neutral
- DNA wears out and breaks
- minimum number of mutations needed to make cancer is 4
- - some cancers needs up to 20
- cancer usually occurs in:
- - young - rapidly dividing cells
- - old - cells have divided many times, possibly many mutations
- - BRCA1 & BRCA2 genes don't guarantee cancer, just means you need fewer mutations
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Mutagen
- factors that cause mutations
- - wear & tear
- - viruses
- - ionizing radiation
- - certain chemicals
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Development
complex multicellular organism from one cell
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Cell differentiation and development
- each division results in increased specialization of the cells
- controlled by the genes within the DNA
- genes can be turned on or off based upone the geometry of the DNA molecule
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Differentiation
- involves temporary or permanent inhibition of genes within a given cell that may be active in another cell
- eg nerve cells make neurotransmitters, epithelial cells do not
- eg epithelial cells make keratin, nerve cells do not
- juvenile cells are more active than adult cells
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Specialization
- what type of cell within the tissue type
- occurs as a result of differentiation
- leads to morphologic changes involving the number and types of organelles within a cell
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