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The cell
- basic unit of life
- single or complex
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Characteristics of the cell
- grow
- develop
- reproduce
- adapt
- respond to stimuli
- maintain homeostasis
- convert food info useable energy
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Cells
- contain genetic material
- capacity to specialize
- enormously diverse
- work collaboratively to form tissues
- CS Lewis - The Lives of Cells
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History of cells
- 3 billion years old
- primordial ooze + electrical impulse = organic molecules
- organic molecule organized into primitive cells
- resemble present day bacteria
- - DNA (single strand)
- - protoplasm
- we can make proteins, lipids, molecules
- we can make cells, but we can't make life
- Holy Grail of biology is finding life and understanding it
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Prokaryotes
- very primitive, but actually quite sophisticated
- pre-nucleus
- DNA free floating in protoplas
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Bacterial prokaryotes
- develop pili
- can probe cytoplasm of another one and will share DNA
- share genetic material
- resultant strain of cholera tracked through the system
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Eukaryotes
true nucleus - DNA bound by a plasma membrane (nuclear membrane)
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History of Cell Theory
- 1665 - Robert Hooke - saw cork under microscope, named them cells
- 1800 - Mathias Schleiden - plant
- 1800s - Theodor Schwann - animal tissue; all life is composed of cells
- 1858 - Rudolf Virchow
- - cells can only arise from pre-existing cells
- - ends "spontaneous generation" theory of life
- - plants have cellulose - rigid
- - microscope inventor; saw bacteria
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Cell Theory
- cell size - avg 10-30 microns
- limiting factors:
- - surface area to volume ratio
- -- cells have to eat - if too big cannot move food in, waste out
- -- small cells are more efficient
- - governing capacity of the nucleus
- -- one nucleus can control a small cell most efficiently
- -- large or highly active cells may have more than one nucleus
- -- if cell gets too large, nucleus loses control
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Cell membrane
- plasma membrane
- plasmalemma
- external boundary of the cell
- governs the movement of atoms and molecules in and out of cell
- composed of protein, phospholipids, cholesterol and carbohydrates
- proteins are like stud in wall
- - globular can be porous like portals
- - peripheral proteins (like coconut on munchkins)
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Plasma membrane
- plasmalemma
- external cell boundary
- not visible with light microscope
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Plasma
anything formed or molded
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Cell membrane components
- internal membrane surface
- phospholipid bilayer
- external membrane surface
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Phospholipid bilayer
- strucural proteins
- globular proteins
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Structural proteins
strengthen bilayer
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Integral globular proteins
- span the width of the bilayer
- act as channels
- -- gated
- -- pores
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Peripheral globular proteins
- found on the inside or outside of the membrane
- on inner surface
- - act as anchors for:
- -- cytoskeleton
- -- keratin
- on outer surface:
- - attach to sugar groups
- -- glycoproteins
- -- glycolipids
- external surface
- - glycocalyx
- -- cell-to-cell adhesion; cell have to know what to stick to
- -- intercellular recognition
- -- activation of cell functions
- --- cell adhesion molecules
- --- membrane receptors
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Cell adhesion molecules (CAM)
- cover surface of mammalian cells
- allow cells to bond to each other and extracellular molecules
- signal circulation cells to area of infection and inflammation
- chemicals in glycocalyx that signal
- in eyes, glycocalyx holds mucus on eyes - tears are liquid but stay attached to eye surface
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Membrane receptors
- integral proteins and glycoproteins that act as binding sites on the surface of cells
- - contact signaling
- -- cell mediated immunity
- - chemical signaling
- -- ligands
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Extensions of the plasma membrane
- identical in structure to the plasma membrane
- - centrioles = basal bodies
- - inner surface of plasma membrane
- - push outward
- cilia and flagellum
- - controlled by centrioles
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Cilia
- short
- numerous
- move synchronously
- create waves of motion that move mucus, cell debris
- location
- - upper airways
- - oviducts
- mammalian reproduction
- - ovary not connected to fallopian tubes
- - cilia encourages eggs to go down fallopian tubes
- - if not, wind up in peritoneal cavity; will cause ectopic pregnancy if fertilized
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Flagella
- long
- single
- propulsion
- uncommon in mammals
- - sperm only
- common in microbes (single-celled organisms)
- mammalian reproduction
- - sperm are the only flagellated cells in mammals
- - forwardly mobile - looks like a snowstorm
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Cytoplasm
- has only been described for 10 years
- there are still elements that are only postulated (can't yet see with microscope resolution available)
- cytosol - solution in the cell
- - viscous (thick)
- - semitransparent
- - site of metabolic activities within the cell
- cytoskeleton
- organelles
- inclusions
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Cytoskeleton
- flexible, fibrous structure that changes with cell function
- provides
- - support and shape
- - movement
- - direction for metabolic activity - like roads for the organelles to line up on
- - anchors organelles
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Fibers in cytoskeleton
- 3 different types (from book - says 3, lists 4)
- - Proteins - made of amino acids; form 3 dimensional complex shapes
- - microtubules
- - intermediate fibers
- - microfilaments
- - microtrabeculae - extremely small - only postulated
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Microtubules
- thickest fiber
- hollow tubes
- act as anchors for organelles
- proteins allow organelles to move along the microtubules
- - tubulin
- - organelles move kind of hand over hand along the microtubule
- exist all over the cell
- they don't move
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Intermediate fibers
- woven - ropelike
- toughest
- most permanent
- name for the cells they're found in or for proteins they're composed of
- - tonofilaments
- -- keratin in epithelial cells
- -- give strength to cell junctures
- - neurofilaments - in neurons
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Microfilaments
- arranged in bundles and meshes
- found near the plasma membrane
- composed of actin and myosin
- allow shape change (contraction)
- assembled where and when needed
- - no cell moves constantly
- WBCs use these when called to injury/infection
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Microtrabeculae
- all this is postulated only
- lattice that connects other cytoskeleton components
- - like a spiderweb over all the other filaments
- give cytosol its viscosity
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Organelles
- literally, little organs
- membrane bound
- - most have phospholipid monolayer, some bilayer
- specialized function
- no glycoclayx - unlike plasma membrane
- creates separate internal environment - like rooms in a building
- metabolic processes include:
- - food absorption
- - energy production
- - excretion
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Types of organelles
- mitochondria - like furnace room
- ribosomes - part of kitchen
- endoplasmic reticulum - part of kitchen
- Golgi apparatus - part of kitchen
- lysosomes - garbage chutes
- peroxisomes - garbage chutes
- inclusions - gift shop
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Mitochondria
- produces ATP
- ATP = cell energy
- uses glucose (CHO2 - preferred fuel)
- changes O2 to CO2
- cellular respiration
- if no glucose available, fatty acid then amino acid catabolism
- respiratory electron transport
- oxidative phosphorylation
- oxidative reactions of the citric acid cycle
- CHO2 => CO2 + water + energy = cellular respiration
- ketones vs CO2 + water for fatty acid and amino acid catabolism, also diabetics (ketoacidosis)
- number of mitochondria relates to activity level of cell
- - 1 or 2 in mature bone
- - crammed full in muscle cells of Olympic athelete
- divide by fission - takes lots of protein
- congregate at sites of energy need
- contain DNA, RNA, proteins
- motile - along microtubules
- two membranes
- - inner - cristae
- - inside - matrix of enzyme rich fluid - Kreb's cycle happens here
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Ribosomes
- most common organelle
- 2 globular subunits containing a globular reactive protein and ribosomal RNA
- cell maintenance
- site of protein synthesis
- free ribosomes
- - attached to the cytoskeleton
- - produce proteins used within the cell
- those bound to endoplasmic reticulum
- - produce proteins used in the cell membrane and exported
- - eg saliva, tears, thyroid hormones, estrogen
- everything wears out and need to the replaced or repaired
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Endoplasmic reticulum (ER)
- single lipid bilayer
- continuous with the nuclear membrane and the Golgi apparatus
- flattened tubes stacked on one another
- 2 types: rough, smooth
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Rough Endoplasmic Reticulum
- has ribosomes
- protein production
- finished proteins move internally to the cisternae
- move on the the Golgi apparatus for packaging for export out of the cell
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Smooth Endoplasmic Reticulum
- no ribosomes
- makes lipids (phospholipids and steroids), generally for internal purposes
- connected to the rough ER
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Kreb's cycle
- every turn of Kreb's cycle gets you 2 ATP
- fairly complex chemical reaction
- this is why you need O2 and H2O
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Golgi apparatus
- similar in structure to ER
- flattened tubes containing cisternae
- proteins (usually around the tertiary stage of folding) arrive from the ER, then...
- ... are modifed within the Golgi (additional functional groups are added)
- sugar groups are synthesized and added
- end product goes into vesicles to world outside cell
- you can see this happening
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Lysosomes
- formed by the Golgi apparatus
- contain hydrolytic enzymes (protein)
- digests cell nutrients and bacteria
- autolysis
- exocytosis
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Hydrolytic
breaking down by addition of H2O
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Autolysis
lysosome breaks open and digests everything in the cell
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Exocytosis
- profiles measure this "garbage" in blood
- high BUN => kidneys not effectively removing it or not excreting it
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Peroxisomes
- created by fission
- common in liver and kidney
- act to detoxify various molecules
- remove free radicals
- contain 2 enzymes that break down radicals:
- - peroxidase
- - catalase
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Free radicals
- groups hanging off proteins/carbs can fall off
- can chemically interact with cells detrimentally
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Inclusions
- everything else in the cell that is not an organelle
- membrane bound
- - secretory granules - generally cell product waiting to be used/shipped
- - vesicles - contain liquid
- - vacuoles - contain gas
- non-membrane bound
- - lipid droplets - small amount of fat
- - fat globules - large amount of fat
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Centrioles
- hollow cylinders composed of microtubules
- paired
- located at the centrosome
- active in cell division
- - only time they do anything
- - produce the spindle fibers (probably actin)
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Nucleus
- largest organelle
- "brain"
- contains DNA
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Nucleus functions
- primary one - control cellular activity through protein synthesis
- secondary - maintian hereditary information of the species
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DNA
- deoxyribonucleic acid
- contains hereditary information
- directions for protein synthesis
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Multinucleated cells
- large, active cells
- skeletal muscle
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Anucleated cells
- mammals
- - red blood cells - erythrocytes
- other vertebrates
- - birds, reptiles - nucleated RBCs
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Nuclear anatomy
- 4 parts
- - nuclear envelope or membrane
- - nucleoplasm
- - chromatin
- - nucleolus - source of RNA, ribosomes; assume there are microtrabeculae here too
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Nuclear membrane (or envelope)
- double phospholipid bilayer
- - outer layer continuous with ER
- - nuclear pores - allow things to enter and exit
- - perinuclear cisterna - space created by membranes
- - proteins similar to ones in plasma membrane
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Nucleoplasm
- similar to cytoplasm/cytosol, has no cytoskeleton
- contained within the nuclear membrane
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DNA, RNA and chromatin
- Rosalind Franklin
- - x-ray crystallography
- - double helix
- James Watson, Francis Crick
- - Nobel prize for structure in 1962
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DNA and RNA structure
- composed of nucleotides
- gives enormous flexibility
- important as different proteins will affect medicines - how they work, reactions to them
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Nucleotides
- nitrogenous bases
- - adenine
- - guanine
- - cytosine
- - thymine - DNA only
- - uracil - RNA only
- backbone of:
- - phosphate group
- - five carbon sugars
- -- deoxyribose - DNA
- -- ribose - RNA
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Chromatin
- composed of DNA and histones
- nucleosome = 1 strand of DNA + 8 histones
- nucleosomes are linked together by linker DNA
- histones are important in gene regulation
- chromatin is the mechanism that keeps DNA from getting tangled
- when it is time to make a protein, unspools the section of DNA that contains instructions for that protein
- the way you spool/unspool DNA is as important as what's in your DNA
- the ER makes the histones for internal use (in the cell)
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Nucleoli
- occur within the nucleus
- not membrane bound
- site of ribosomal subunit synthesis and ribosomal RNA synthesis
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