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 products

2. 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 & SER Contiguous

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

Golgi Apparatus

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

http://www.google.com/imgres?q=cell+biology+cartoons&start=130&hl=en&biw=1366&bih=499&tbm=isch&tbnid=ask5vj79u6_XJM:&imgrefurl=http://www.ascb.org/index.php?option=com_content&view=article&id=877&Itemid=361&docid=pXPawxVv0F67gM&imgurl=https://www.ascb.org/meetings/images/CellDance2012Poster.png&w=800&h=1200&ei=LxhfUJeQJon68QShtIDADg&zoom=1&iact=hc&vpx=398&vpy=95&dur=798&hovh=275&hovw=183&tx=91&ty=179&sig=102733850649124752380&page=8&tbnh=152&tbnw=117&ndsp=18&ved=1t:429,r:8,s:130,i:156

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

http://www.google.com/imgres?q=cell+biology+cartoons&start=130&hl=en&biw=1366&bih=499&tbm=isch&tbnid=-oh5VRXkoHE3SM:&imgrefurl=http://franczyk.yolasite.com/&docid=OggVq4sIwRNkuM&imgurl=http://franczyk.yolasite.com/resources/Cartoon.gif&w=240&h=286&ei=LxhfUJeQJon68QShtIDADg&zoom=1&iact=hc&vpx=112&vpy=142&dur=8377&hovh=228&hovw=192&tx=82&ty=158&sig=102733850649124752380&page=8&tbnh=152&tbnw=128&ndsp=18&ved=1t:429,r:6,s:130,i:150

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

Mitochondrion Structure

Nucleus contains most of the DNA 5 microns across on average enclosed by dbl membrane: nuclear

envelope

Chromatin

Nucleolus

Nucleus Nucleolus

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 divides

2. 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