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Cell structure
1. THE CELL
BY DR. SAKINA RUHI
MBBS, MD(BIOCHEMISTRY)
SENIOR LECTURER,DEPARTMENT OF
BIOCHEMISTRY,IMS, SHAHALAM
2. 2
OUTLINE
• Difference between prokaryotic & Eukaryotic cell .
• Difference between Animal & Plant cell
• Different cell organelles & Its function
• Cell Membrane
• Molecular movements & Cell-transport mechanism
3. 3
Cell Theory
• 1. All living things are made of cells.
• 2. New cells are produced from existing
cells
• 3. Cells are the basic unit of structure
and function in living things.
4. 4
Prokaryotes vs. Eukaryotes
• Prokaryotes
(bacteria)
nucleus not well
defined
and very few
organelles.
• Eukaryotes
(protists,
fungi, plants and
animals) larger,more
complex,DNA is
inside the nucleus
5. 5
Plant Cells Vs. Animal Cells
• Only plant cells
contain:
• Cell wall
• Chloroplasts
• Large central
vacuoles
• Only animal
cells contain:
• Centrioles
9. 9
Nucleus
• Repository for genetic material
• Directs activities of the cell
• Usually single, some cells several,
• RBC none
• Contains
• Chromosomes
• Nucleolus
10. 10
Nuclear Envelope
• Separates nucleus from
rest of cell by two
phospholipid bilayer
membrane
Double membrane
Has pores
11. 11
Nucleolus
• Directs synthesis of RNA
• Nucleolus is mainly involved in
the assembly of ribosomes
12. 12
Endoplasmic reticulum
• Largest internal membrane
• Composed of Lipid bilayer
• Serves as system of channels from the nucleus
• Functions in storage and secretion
• Two types
• Rough endoplasmic reticulum
• Smooth endoplasmic reticulum
14. 14
Smooth Endoplasmic Reticulum
• No attached ribosomes
• Has enzymes that help
build molecules
• Carbohydrates
• Lipids
15. 15
Rough Endoplasmic Reticulum
• Ribosomes attached to the
surface
• Manufacture protiens
• Not all ribosomes attached
to rough ER
• May modify proteins from
ribosomes
16. 16
Ribosomes
• Ribosomes are RNA-protein complexes composed of
two subunits that join and attach to messenger RNA.
• site of protein synthesis
• assembled in nucleoli
17. 17
Golgi Apparatus
Packaging & shipping station
of cell
collect, pack, and distribute
molecules synthesized at
one location in the cell
and utilized at another
location
18. 18
HOW Golgi Apparatus Functions
1. Molecules come in vesicles
2. Vesicles fuse with Golgi
membrane
3. Molecules may be modified
by Golgi
4. Molecules pinched-off in
separate vesicle
5. Vesicle leaves Golgi apparatus
6. Vesicles may combine with plasma
membrane to secrete contents
24. 24
PEROXISOMES
Peroxisomes –are single
membrane cellular
organelle,also called
microbodies
Catalase and peroxidase:
the enzymes of
peroxizomes destroy
unwanted peroxides & other
free radicals
25. 25
Cytoskeleton
• Network of
protein
filaments
• Maintains shape
• Involved in cell
movement
27. 27
Cell Membrane
• Regulates what
enters and leaves
the cell and
provides support
and protection
• Structure – lipid
bilayer with
embedded proteins
29. 29
Membrane Proteins
1. Channels or transporters
• Move molecules in one
direction
2. Receptors
• Recognize certain
chemicals
30. 30
Membrane Proteins
3. Glycoproteins
• Identify cell type
4. Enzymes
• Catalyze production of substances
31. 31
TRANSPORT MECHANISM
classified into
Passive Transport (i)simple diffusion
(ii)facilitated diffusion
(iii) ion exchange
Active Transport
Pumps –can drive molecules against the gradient using
energy
32. 32
Simple Diffusion
Particles move from an area of high
concentration to an area of lower
concentration
No energy is required
very slow
33. 33
Osmosis
• Diffusion of water through a
selectively permeable membrane
34. 34
Facilitated Diffusion
• Molecules move through protein
channels.
• Carrier mediated process
• No energy required
35. 35
ION CHANNELS
• Membrane have special devices called ion channels
• For quick transport of Na +,K+ ,Cl + and Ca ++
• They remain close and open on response to stimulus
• They are also called as gated channels
• Important for nerve impulse propogation,synaptic
transmission
36. 36
Active Transport
• Carried our by protein pumps found in
the membrane
• Energy is required
37. 37
• Molecular movAemcenttive Transport
• Requires energy (against gradient)
• Example is sodium-potassium pump
38. Endocytosis
38
• Cell takes material into cell by infolding of the cell
membrane
• Phagocytosis – eating – cell engulfs large particles
• Pinocytosis – drinking – cell takes in liquid
39. 39
• Plasma mPemrobrcanee ssusr rooufn dEs mnatderoialcytosis
• Edges of membrane meet
• Membranes fuse to form vesicle
41. 41
Transport system
• Classified as Uniport , Symport and Antiport
• UNIPORT-Carries single solute across the membrane e.g –
glucose transporter in most cells ,calcium pump
• CO TRANSPORT –If transfer of one molecule depend on
simultaneous transfer of another molecule.
• (i)SYMPORT (ii) ANTIPORT
43. 43
• SYMPORT-Transporter carries two solutes in same
direction .
• eg-sodium dependent glucose transport
• ANTIPORT –Carries two solutes or ions in opposite
direction
• eg sodium pump,sodium bicarbonate exchange in RBC