Introduction to Anatomy (Lec 3) 2021-2022-1.pdf

Introduction to Anatomy (Lec 3) 2021-2022-1.pdf

1. STRUCTURE OF CELL
Pharm D 1
st
Prof
Bahauddin Zakariya University Multan
Waseem Ashraf

2. Recommended Books:
•Fundamentals of Anatomy & Physiology. Martini F, Nath JL, Bartholomew EF. 10th Edition
•Principles of Anatomy and Physiology. Tortora GJ, Derrickson B. 13th Edition

3. STRUCTURE OF CELL
Cytology-The study of cellular structure and function is a part of the broader discipline of cell biology,
which integrates aspects of biology, chemistry, and physics.
Cells were first discovered in 1665 by Robert Hooke and later research led to the development of cell
theory.
•Cells are the building blocks of all plants and animals.
•All cells come from the division of preexisting cells.
•Cells are the smallest units that carry out life’s essential physiological functions.
•Each cell maintains homeostasis at the cellular level. Homeostasis at the level of the tissue,
organ, organ system, and organism reflects the combined and coordinated actions of many cells.
Two general classes of cells are
Somatic Cells and Sex Cells

4. STRUCTURE OF CELL

5. STRUCTURE OF CELL
Major Parts of the Cell
•Cell Membrane
•Cytoplasm (Cytosol + Organelles)
•Nucleus
The plasma membrane is extremely thin, ranging from 6 to 10 nm in thickness. Its general functions
include:
•Physical Isolation
•Regulation of Exchange with the Environment
•Sensitivity to the Environment
•Structural Support

6. STRUCTURE OF CELL Membrane
The structure of cell membrane is best explained by fluid mosaic model. Made up of around 40-45% of
lipids and 55-60% of proteins.
Lipid bilayer
Thebasicstructuralframeworkoftheplasmamembraneisthelipidbilayer,twoback-to-backlayers
madeupofthreetypesoflipidmolecules—phospholipids,cholesterol,andglycolipids
About75%ofthemembranelipidsarephospholipids,lipidsthatcontainphosphorus.Presentin
smalleramountsarecholesterol(about20%),asteroidwithanattached–OH(hydroxyl)group,and
variousglycolipids(about5%),lipidswithattachedcarbohydrategroups.
Thebilayerarrangementoccursbecausethelipidsareamphipathicmolecules,whichmeansthatthey
havebothpolarandnonpolarparts.

7. STRUCTURE OF CELL Membrane
In phospholipids, the polar part is the phosphate-containing “head,” which is hydrophilic. The nonpolar
parts are the two long fatty acid “tails,” which are hydrophobic hydrocarbon chains.
The headsface a watery fluid on either side—cytosol on the inside andextracellular fluid on the outside.
The hydrophobic fatty acid tails in each half of the bilayer point toward one another, forming a nonpolar,
hydrophobic region in the membrane’s interior.
Cholesterolmolecules are weakly amphipathic and are interspersed among the other lipids in both
layers of the membrane. The tiny -OH group is the only polar region of cholesterol, and it forms hydrogen
bonds with the polar heads of phospholipids and glycolipids. The stiff steroid rings and hydrocarbon tail of
cholesterol are nonpolar; they fit among the fatty acid tails of the phospholipids and glycolipids.
The carbohydrate groups of glycolipids form a polar “head”; their fatty acid “tails” are nonpolar.
Glycolipids appear only in the membrane layer that faces the extracellular fluid, which is one reason the
two sides of the bilayer are asymmetric, or different

8. STRUCTURE OF CELL Membrane

9. STRUCTURE OF CELL Membrane
Membrane Proteins
There are two general structural classes of membrane proteins.
•Integral Proteins
•Peripheral Proteins
Integral proteins are part of the plasma membrane structure and cannot be easily separated from it
without damaging or destroying the membrane. Most integral proteins span the width of the membrane
one or more times and are known as transmembrane proteins. These proteins contain hydrophobic
portions embedded within the hydrophobic lipid bilayer, with their hydrophilic portions extended into the
extracellular environment and cytosol.
Peripheral proteins are bound to the inner or outer surface of the membrane and are easily separated
from it.
Integral proteins greatly outnumber peripheral proteins.

10. STRUCTURE OF CELL Membrane
Manyintegralproteinsareglycoproteins,proteinswithcarbohydrategroupsattachedtotheendsthat
protrudeintotheextracellularfluid.Thecarbohydratesareoligosaccharides,chainsof2to60
monosaccharidesthatmaybestraightorbranched.Thecarbohydrateportionsofglycolipidsand
glycoproteinsformanextensivesugarycoatcalledtheglycocalyx.Thepatternofcarbohydratesinthe
glycocalyxvariesfromonecelltoanother.
Therefore,theglycocalyxactslikeamolecular“signature”thatenablescellstorecognizeoneanother.For
example,awhitebloodcell’sabilitytodetecta“foreign”glycocalyxisonebasisoftheimmuneresponse
thathelpsusdestroyinvadingorganisms.Inaddition,theglycocalyxenablescellstoadheretooneanother
insometissuesandprotectscellsfrombeingdigestedbyenzymesintheextracellularfluid.The
hydrophilicpropertiesoftheglycocalyxattractafilmoffluidtothesurfaceofmanycells.Thisaction
makesredbloodcellsslipperyastheyflowthroughnarrowbloodvesselsandprotectscellsthatlinethe
airwaysandthegastrointestinaltractfromdryingout.

11. STRUCTURE OF CELL Membrane
Membraneproteinscarryoutavarietyofspecializedfunctions.Herearesomeexamplesofimportant
typesofmembraneproteins:
AnchoringProteins:Anchoringproteinsattachtheplasmamembranetootherstructuresandstabilizeits
position.Insidethecell,membraneproteinsareboundtothecytoskeleton,anetworkofsupporting
filamentsinthecytoplasm.Outermembraneproteinsmayattachthecelltoextracellularproteinfibersor
toanothercell.
RecognitionProteins(Identifiers):Thecellsoftheimmunesystemrecognizeothercellsasnormalor
abnormalbasedonthepresenceorabsenceofcharacteristicrecognitionproteins.Manyimportant
recognitionproteinsareglycoproteins(forexampleMHCproteins).
Enzymes:Enzymesinplasmamembranesmaybeintegralorperipheralproteins.Theycatalyzereactionsin
theextracellularfluidorinthecytosol,dependingonthelocationoftheproteinanditsactivesite.For
example,dipeptidesarebrokendownintoaminoacidsbyenzymesontheexposedmembranesofcells
thatlinetheintestinaltract.

12. STRUCTURE OF CELL Membrane
ReceptorProteins:Receptorproteinsintheplasmamembranearesensitivetothepresenceofspecific
extracellularmoleculescalledligands.Aligandcanbeanythingfromasmallion,likecalcium,toarelatively
largeandcomplexhormone.Whenanextracellularligandbindstotheappropriatereceptor,thatbinding
maytriggerchangesintheactivityofthecell.Forexample,thebindingofthehormoneinsulintoaspecific
membranereceptorproteinisthekeystepthatleadstoanincreaseinthecell’srateofglucoseabsorption.
Plasmamembranesdifferinthetypeandnumberofreceptorproteinstheycontain,andthesedifferences
accountforacell’ssensitivitytospecifichormonesandotherligands.
CarrierProteins:Carrierproteinsbindsolutesandtransportthemacrosstheplasmamembrane.Carrier
proteinsmayrequireATPasanenergysource.Forexample,virtuallyallcellshavecarrierproteinsthat
bringglucoseintothecytoplasmwithoutexpendingATP.YetthesecellsmustuseATPtotransportions
suchassodiumandcalciumacrosstheplasmamembraneandoutofthecytoplasm.

13. STRUCTURE OF CELL Membrane
Channels:Someintegralproteinscontainachannel,orcentralpore,thatformsapassagewaycompletely
throughtheplasmamembrane.Thechannelpermitswaterandsmallsolutestomoveacrosstheplasma
membrane.Ionsdonotdissolveinlipids,sotheycannotcrossthephospholipidbilayer.Forthisreason,
ionsandothersmallwater-solublematerialscancrossthemembraneonlybypassingthroughchannels.
Manychannelsarehighlyspecificandpermitonlyoneparticulariontopass.Themovementofions
throughchannelsisinvolvedinavarietyofphysiologicalmechanisms.Channelsaccountforabout0.2
percentofthetotalsurfaceareaoftheplasmamembrane,buttheyareextremelyimportantin
physiologicalprocesseslikemusclecontractionandnerveimpulsetransmission.

14. STRUCTURE OF CELL
Transport Across Cell Membrane

15. STRUCTURE OF CELL
Transport Across Cell Membrane

16. STRUCTURE OF CELL
Transport Across Cell Membrane