Brief discrption of cell it's type

1. Biochemistry of cell, its
organelles and cell membrane
MLT 102
1st semester

2. Introduction
A cell is the smallest unit that is capable of
performing life functions.

3. Cell Theory
• All living things are made up of cells.
• Cells are the smallest working units of all living
things.
• All cells come from preexisting cells through cell
division.

4. Types of cell
Prokaryotic
• Do not have structures
surrounded by membranes
• Few internal structures
• One-celled organisms,
Bacteria
Eukaryotic
• Contain organelles
surrounded by membranes
• Most living organisms

5. Molecules of cell
Organic
• Proteins
• Carbohydrates
• Lipids
• Nucleic acids
Inorganic
• Minerals
• Water

6. Subcellular Organelles
• Cell membrane
• Nucleus
• Golgi Apparatus
• Lysosomes
• Mitochondria
• Peroxisomes
• Cytoskeleton
• Centriole

7. Cell Membrane
Cell Membrane Composition
• Plasma membrane encloses cell and cell
organelles
• Made of hydrophobic and hydrophilic
components
– Semi-permeable and fluid-like
– “lipid bilayer”

8. Cell membrane composition
• Integral proteins interact with “lipid bilayer”
– Passive transport pores and channels
– Active transport pumps and carriers
– Membrane-linked enzymes, receptors and
transducers
• Sterols stabilize the lipid bilayer
– Cholesterol

10. Lipid Molecules
(Figure 4-3, pg 81)

12. Molecules Related to Cell Permeability
• Depends on
– Molecules size (electrolytes more
permeable)
– Polarity (hydrophillic)
– Charge (anion vs. cation)
– Water vs. lipid solubility

13. Cell Permeability
• Passive transport is carrier mediated
– Facilitated diffusion
– Solute molecule combines with a “carrier” or
transporter
– Electrochemical gradients determines the
direction
– Integral membrane proteins form channels

14. Crossing the membrane
• Simple or passive diffusion
• Passive transport
– Channels or pores
• Facilitated transport
– Assisted by membrane-floating proteins
• Active transport pumps & carriers
– ATP is required
– Enzymes and reactions may be required

15. Modes of Transport
(Figure 4-17, pg 91)

16. Carrier-Mediated Transport
• Integral protein binds to the solute and undergo a
conformational change to transport the solute
across the membrane

17. Channel Mediated Transport
• Proteins form aqueous pores allowing specific solutes to
pass across the membrane
• Allow much faster transport than carrier proteins

18. Coupled Transport
• Some solutes “go along for the ride” with a
carrier protien or an ionophore
Can also be a Channel
coupled transport

19. • Three main mechanisms:
– coupled carriers: a solute is
driven uphill compensated by a
different solute being
transported downhill
(secondary)
– ATP-driven pump: uphill
transport is powered by ATP
hydrolysis (primary)
– Light-driven pump: uphill
transport is powered by energy
from photons
(bacteriorhodopsin)
Active transport

20. Active transport
• Energy is required

21. •Against their
electrochemical
gradients
•For every 3 ATP, 3
Na+ out, 2 K+ in
Na+/K+ Pump
• Actively transport Na+ out of the cell and K+ into the cell
(Figure 4-24, pg 96)

22. • About 1/3 of ATP in an animal cell is used to
power sodium-potassium pumps
Na+/K+ Pump
• In electrically active nerve
cells, which use Na+ and K+
gradients to propagate
electrical signals, up to 2/3 of
the ATP is used to power these
pumps

23. Calcium pump
• ATP dependent calcium pump also functions to
regulate muscle contraction
• Specialized membrane system called
sarcoplasmic reticulum found in skeletal muscles
regulate calcium concentration around muscle
fibers
• During relaxation Ca++ concentration around
muscle fibers is low
• Stimulation by nerve impulse releases large
amount of Ca++ and triggered muscle
contraction

25. Transport System
• Uniport
Carries single solute across membrane
e.g calcium pump
• Symport
Carries two solute in same direction across the
membrane
e.g Amino acid transport
• Antiport
Carries two solute or ion in opposite direction
e.g sodium pump

27. Endocytosis and Exocytosis
• Exocytosis
- membrane vesicle fuses with cell membrane,
releases enclosed material to extracellular space.
• Endocytosis
- cell membrane invaginates, pinches in, creates
vesicle enclosing contents
Two types
-Pinocytosis( Liquid form)
-Phagocytosis( Solid form)

28. Receptor Mediated Endocytosis
(Figure 4-30, pg 102)

30. Interaction between cell
and its Environment

31. Introduction
• Cells do not exist alone
• Cell interact with extracellular material to
form defined tissues.
• These interactions are crucial to formation of
epithelial tissue and connective tissue, which
are crucial for various cellular activities.
• It includes cell migration, cell growth, cell
differentiation, organization of tissues , organs
that emerges during embryonic development.

32. Extracellular Space
Glycocalyx (cell coat)
• It is formed from carbohydrates projection
originated from plasma membrane
• Outer surface of plasma membrane
• Mediate cell-cell and cell-substratum
interactions
• Provides mechanical protection to the cell
• Bind important regulatory factors

33. Extracellular matrix
• It is the organized
network of proteins
and polysaccharides
beyond the plasma
membrane
• Glue the holds the
cell together
• Often determine
the shape and
regulatory activity
of cell

34. Continued
Gel-like ground
substance are primarily
made up of
polysaccharide
a. Glycosaminoglycan
b. Proteoglycans
Fibrous proteins
collagen., laminin,
elastin, fibronectin,
They have structural
and adhesive role

35. Major types of collagen
• Type I
Chief component of tendons, ligaments, bones
• Type II
Represent more than 50% of protein cartilage ,
important component of vitreous of eye.
• Type III
Strengthen the wall of hollow structure like arteries,
intestine, uterus
• Type IV
Forms the basal lamina of epithelia

36. Proteoglycans
• Protein-polysaccharide complex, with a core protein
attached to glycosaminoglycans (GAGS)
• Glycosaminoglycans (GAGS) have repeating
disaccharides
• Negatively charged
• Negative charge attract water forming a porous
hydrated gel
• Able to withstand compression forces through
hydration and swelling pressure to the tissue

38. Extracellular Space
Fibronectin(Fn)
• Multiple binding domains
• Complex proteins that binds to multiple substrate
• Helps cell to attach matrix
• Fn has binding sites for other components
• It involved in many cellular processes including
tissue repair, embryogenesis, blood clotting , cell
migration / adhesion

40. Extracellular Space
Laminins
• Extracellular glycoproteins consisting of three
polypeptide chains linked by disulphide bonds
• Help cell migration during development
• Components of basement membranes
Integrins
• Family of proteins composed of heterodimers withα and
β
• Having a major role in integrating extracellular and
intracellular environments
• Adhesion of cells to their substratum or other cells.

41. Continued
Hemidesmosomes
• Cell- substratum adhesion sites that connect
extra cellular matrix to keratin cytoskeleton
• Basal attachment of epithelial cells to the
basement membrane in vivo
• Contain dense plaque with filaments
consisting of keratin

42. Continued
Focal contacts
Found at cell membrane where cytoskeleton
interacts with proteins of extracellular matrix
It is scattered discrete site for cell adhesion
Act as a type of sensory structure

44. Selectins
• Family of integral membrane
glycoproteins that bind to
sugars on the surface of cell
• Contain cytoplasmic domain ,
single membrane spanning
domain, a large extracellular
segment
• Three types
• E-selectin on endothelial cells
• P- selectin on platelets and
endothelial
• L-selectiin on WBCs

45. Immunoglobin super family(IgSF)
• Most proteins are involved in immune
functions
• They mostly mediate interaction of
lymphocytes with cell required or immune
response