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The Cellular Level of Organization Honors Anatomy & Physiology
The Cellular Level of Organization
Honors Anatomy & Physiology
~200 different types cells in body all arise from cell division each type has unique role in supporting
homeostasis
Cells
Plasma Membrane separates inside from outside selective barrier that helps establish &
maintain appropriate environment for normal cell activities
key role in cell-to-cell communication
Parts of a Cell
Plasma Membrane fluid mosaic model
◦lipid bilayer makes up basic structural framework
◦3 lipid molecules1. Phospholipids (~75% of membrane)2. Cholesterol (~20%)3. Glycolipids (~5%)
Simplified Plasma Membrane
*amphipathic: have both polar & nonpolar parts
made of 1. phosphate head (polar)2. two long fatty acid (f.a.) chains (nonpolar)
Phospholipids
PHOSPHOLIPID BILAYER
weakly amphipathic
Cholesterol
Integral Proteins most
transmembrane amphipathic
◦hydrophobic a.a. extend among f.a. tails
Membrane Proteins
Peripheral Proteins
not embedded in membrane
ass‘c loosely with polar heads or integral proteins
inner or outer surface
Membrane Proteins
protein + carbohydrate group attached that protrudes in ECF (never inside cell)
glycocalyx: all carbs attached to proteins or lipids on exterior surface of plasma membrane
Glycoproteins
1. Ion Channels◦selective pores or holes (think straws)
thru which specific ions can flow in/out of cell
Functions of Membrane Proteins
2. transporters selectively move a polar substance or ion
across membrane
Functions of Membrane Proteins
3. receptors integral proteins that serve as cell
recognition sites recognize specific type of molecule called
a ligand
Functions of Membrane Proteins
4. enzymes some integral (or peripheral) proteins
catalyze specific chemical rx on inside or outside of cell
Functions of Membrane Proteins
5. linkers integral (or peripheral) proteins that
anchor proteins in plasma membrane of neighboring cells to each other
Functions of Membrane Proteins
6. cell-identity markers glycoproteins (or glycolipids) enable cell to recognize other cells of
same kind during tissue formation or to recognize & respond to foreign cells ex: ABO bld type
Functions of Membrane Proteins
individual molecules not static in membrane *fluidity greater when there are more dbl
bonds in the f.a. tails of phospholipids cholesterol makes membrane stronger but
less fluid @ normal body temps
Membrane Fluidity
Membrane Fluidity
lipid bilayer permeable to most nonpolar, uncharged small molecules
& impermeable to ions & most charged or polar molecules
# of ion channels alters the membrane permeability
Cell Membranes are Selectively Permeable
Membrane Permeability
because membranes are selectively permeable, differences in concentrations of chemicals between inside/outside of cell can exist
differences in charge across membrane = electrical gradient called a membrane potential
Concentration Gradients
Membrane Potential
all ions & molecules have KE & each will move down its concentration gradient passively◦ diffusion◦ osmosis
active transport: material moves against its concentration gradient so cell must spend nrg ◦ pumps◦ endo- & exo- cytosis
Transport Across Membrane
Passive Transport is diffusion of substance across
membrane w/no nrg investment
higher concentration lower concentration ◦ equilbrium reached when concentration same◦ movement continues
Diffusion
affected by:1. steepness of concentration gradient2. temperature3. mass of diffusing substance4. surface area available for diffusing5. distance material is diffusing thru
Rate of Diffusion Across a Membrane
nonpolar, hydrophobic molecules, fat-soluble vitamins, small alcohols, ammonia, small amts water and urea◦ gases: O2, CO2, N2, ◦ steroids,◦ vit. A, D, E, K
Materials That Diffuse Thru Plasma Membrane
ion channels: allow K+, Na+, Cl-, & Ca++ to move down concentration gradients when open
Diffusion of Ions Across Plasma Membrane
Is Diffusing Material Polar or Nonpolar?
diffusion of water across semi-permeable (selectively permeable) membrane◦ water moves not the solute
Isotonic solution:◦ cell has same concentration of solutes as solution
Hypotonic solution:◦ cell has higher concentration of solutes than
solution Hypertonic solution:
◦ cell has lower concentration of solutes than solution
Osmosis
RBCs in Solution
http://www.stolaf.edu/people/giannini/movies/paramecium/para%20cont.mov
solute moves passively by diffusion but requires a protein channel to cross membrane
*glucose binds to a specific transporter protein changes shape glucose crosses membrane thru transporter protein returns to its original shape
Facilitated Diffusion
Facilitated Diffusion http://programs.northlandcollege.edu/biolog
y/Biology1111/animations/passive3.swf
used to move materials from high concentration side of membrane lower concentration side
ex: some ions, a.a., monosaccharides
Active Transport
2 sources:1. ATP
◦ pumps◦ Na+/K+ pump
2. nrg stored in Na+ or H+ concentration gradient
◦ 1 substance moves in down its concentration gradient & brings along 2nd material
Energy for Active Transport
#1 pump in body cells
Na+/K+/ATPase Pump
Na+/K+/ATPase Pump http://www.brookscole.com/chemistry_d/tem
plates/student_resources/shared_resources/animations/ion_pump/ionpump.html
medication given to patients with heart failure (weakened pumping action of heart)
action:◦ slows action of the Na+/K+ pumps which lets
more Na+ accumulate inside cardiac muscle fibers decreased Na+ concentration gradient across plasma membrane Na+/Ca++ antiporters in these cells to slow down increases intracellular concentrations of Ca++ increases force of contractions
Digitalis
uses both symporters & antiporters that are powered by an ion concentration gradient (usually Na+ or H+)
Secondary (2°) Active Transport
Bulk Transport Across the Membrane used by large macromolecules or large
volumes of smaller molecules1. Exocytosis2. Endocytosis
Endocytosis
cell eats solid particles neutrophils & macrophages are phagocytes
Phagocytosis
bulk-phase endocytosis◦ cell takes in ECF
Pinocytosis
1 side of cell vesicles undergoing endocytosis but also undergoing exocytosis of same material on opposite side of cell
Transcytosis
all cellular content inside plasma membrane except for the nucleus
consists of:1. Cytosol: (ICF)
◦ fluid portion◦ contains ions, proteins, a.a., f.a., lipids, ATP,
waste products2. Organelles:
◦ specialized structures with characteristic shapes that have specific structure
Cytoplasm
Cytoskeleton organizes the structure & activities of
a cell 3 types:
1. Microtubules2. Microfilaments3. Intermediate Filaments
Functions of the Cytoskeleton1. mechanical support2. maintain cell shape3. provides anchor for organelles &
cytosol enzymes4. cell motility
pair of centrioles & pericentriolar material that organizes microtubules in nondividing cells & the mitotic spindle in dividing cells
Centrosomes
numerous, hairlike projections that extend from surface of cell
each has 29 microtubules surrounded by plasma membrane
oar-like movement pattern of beating steady movement of fluid across surface of cell
Cilia (Cilium singular)
Damage Done by Smoking
structure similar to cilia but much longer only human cell: sperm generates forward motion
Flagella (Flagellum: singular)
Ribosomes rRNA & proteins carry out protein synthesis free ribosomes or ribosomes
embedded in membrane polysomes: string of ribosomes
Ribosomes Polysomes
Ribosomes
Endoplasmic Reticulum >50% of membrane in a cell “endoplasmic” means within the
cytoplasm” “reticulum” means little net made of network of tubules & sacs
Endoplasmic Reticulum cisternae spaces contiguous with
nuclear envelope
RER ribosomes on outer surface of
membrane most proteins made shipped out of cell most secretory proteins are
glycoproteins so that carbohydrate attachment is done by enzymes in RER membrane
SER functions:
◦lipid synthesis◦metabolism of carbohydrates◦detoxification of drugs & poisons◦storage of Ca++
SER cells with lots SER:
◦endocrine glands synthesize steroid hormones
ovaries, testes, adrenals◦hepatocytes detoxify by adding –OH, increases solubility cleared by kidneys
alcohol, drug abusers (legal or not) have increased amts of SER in their hepatocytes (also increases drug tolerance)
Detox by SER
SER
Golgi Apparatus receives, sorts, packages, ships also does a little modifying of proteins extensive in cells that secrete made of flattened membranous sacs
with a curve (has directionality cis & trans)
internal space = cisternae
Golgi Apparatus Vesicles when leave trans vesicles have
molecular ID tags that indicates where they are going
vesicles have receptor proteins on external surface that “recognize” where vesicle is supposed to dock (other organelles, plasma membrane)
Lysosomes membranous sac filled with hydrolytic
enzymes digests macromolecules use acidic pH made in RER Golgi cytosol
Lysosome Functions digest food vacuoles ingested by
phagocytosis in protists or by macrophages (WBCs that ingest bacteria or debris and recycle nutrients in them)
autophagy: hydrolytic enzymes in lysosomes recycle cell’s own organic material in worn out organelles
Lysosomal Storage Diseases autosomal recessive diseases
lack a functioning hydrolytic enzyme whatever that enzyme would have chemically broken down builds up in lysosome (called a residual body) lysosomes fill up interferes with cell functions◦ example: Tay Sachs disease
lipid-digesting enzyme malfunction (Hex A) affects neurons seizures, muscle rigidity,
demented, uncoordinated, death usually in childhood
Peroxisomes specialized metabolic compartment
with 1 membrane contain enzymes that remove H atoms
from various molecules to O2 H2O2 H2O2 2 H2O by enzymes in liver
peroxisomes new ones form from old ones functions:
◦break down fatty acids◦in hepatocytes detoxify alcohol, poisons
Mitochondria in nearly all cells, 1- 10 microns # correlates with metabolic activity of cell dbl membrane inner membrane folded (cristae) & divides
mitochondria into 2 separate inner compartments (intermembrane space & matrix)
matrix contains enzymes for cellular respiration, DNA, ribosomes
intermembrane has enzymes that make ATP
Nucleus contains most of the DNA 5 microns across on average enclosed by dbl membrane: nuclear
envelope
Chromatin
http://www.studiodaily.com/2006/07/cellular-visions-the-inner-life-of-a-cell/
Inner Life of Cell
Quiz Time
2 parts:1. Transcription2. Translation
Protein Synthesis
set of rules that relates the base triplet sequences of DNA to the corresponding codons of RNA & the a.a. they specify
Genetic Code
DeoxyriboNucleic Acid building blocks: nucleotides
◦ 3 parts: __________, ___________, & ____________◦ 4 different nucleotides in DNA:1. Adenine2. Guanine3. Cytosine4. Thymine
DNA
Cytosine (C) always paired with Guanine (G)
Adenine (A) always paired with Thymine (T)
RNA has no T but does have U (uracil)
Base-Pair Rules
DNA serves as template for copying information into a complementary sequence of codons in mRNA
1 gene will be transcribed into 1 mRNA enzyme RNA polymerase:
◦ unwinds DNA◦ makes mRNA using complementary base pair
rules
Transcription
the synthesis of RNA using information in DNA
mRNA made using complimentary base pairing
Transcription: short version
Transcription
mRNA leaves nucleus ribosome in cytoplasm
nucleotide sequence of mRNA specifies a.a. sequence of a protein◦ start codon stop codon
mRNA binds to ribosome tRNA delivers a.a. (using base-pair rules) a.a. joined by peptide bonds form polypeptide chain
Translation
synthesis of a polypeptide using the information in mRNA
“translates” message in mRNA a.a.
Translation: short version
Protein Synthesis
http://bcs.whfreeman.com/thelifewire/content/chp12/1202003.html
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120077/micro06.swf::Protein%20Synthesis
Animation Time!
http://www.wiley.com/college/boyer/0470003790/animations/translation/translation.htm
Try at home: Interactive
process by which cells reproduce 2 daughter cells genetically identical to
parent cell (2n # of chromosomes) 2 parts:1. Mitosis
◦ nucleus divides2. Cytokinesis
◦ cytoplasmic division
Cell Division
Mitosis
Cytokinesis
results in production of gametes 2n parent cell 4 (n) daughter cells that are
genetically different from parent
humans: 23 pair of chromosomes so… n = ___________
2n = ____________
Reproductive Cell Division
Prophase I homologous chromosomes synapse forming
tetrad crossing over (trading small portions)
Meiosis I
Meiosis I
start with 2 daughter cells from meiosis I◦ each has n # of duplicated chromosomes
go through 2nd nuclear division & cytokinesis 4 daughter cells each with n # chromosomes (haploid)
Meiosis II
Meiosis II
Meiosis
meiosis in males 4 haploid sperm meiosis in females 1 ova + 3 polar bodies
due to unequal division of cytoplasm
Male/Female Difference
~200 different types of cells in bodysizes vary from 8μm to 140μm
1μm = 1/25,000 inch
*cell’s shape reflects its function
Cellular Diversity
many theories of aging proposed:◦ genetically programmed cessation of cell division◦ buildup of free radicals◦ intensified autoimmune response
Aging & Cells
