CELL Biochemistry.ppt cell structure & function

cell

2. Cell Bio
chemistry
Dr. Jamal Asad
B.D.S ,
M.phil. Biochemistry scholar (UHS)
Demonstrator Dept. of Biochemistry
Multan Medical & Dental College, Multan.

3. Learning Objectives

5. Define Biochemistry
•Biochemistry or biological chemistry is
the study of chemical processes within
and relating to living organisms.

6. •The chemical components of the human body,
including carbohydrates and lipids; amino acids
and proteins; blood and plasma; biological
membranes; nucleic acids (DNA and RNA)
•The major chemical processes in the human
body, such as cell development; enzyme activity;
membrane transport mechanisms; homeostasis;
blood coagulation (clotting); oxygen transport;
neurotransmitter function; ageing.

7. •Nutrition and mineral metabolism, including
the role and function of vitamins in the body
•Molecular genetics
•Heredity
•Genomics

8. •Much of biochemical inquiry deals with the structures,
functions and interactions of biological
macromolecules — large and complex molecules (such
as proteins) which provide the structure of cells and
perform many of the functions associated with life.
•The chemistry of the cell also depends on the reactions
of smaller molecules and ions. These molecules can be
organic (e.g. the amino acids that are used to
synthesize proteins) or inorganic (e.g. water and metal
ions).

14. Thanks?

15. CELL MEMBRANE
•It defines the periphery of the cell, separating its
contents from the surroundings. It is composed of
enormous numbers of lipids & protein
molecules, held together by primarily non
covalent hydrophobic interactions ,forming a
thin, tough, pliable hydrophobic bilayer around
the cell.
•It is 7.5 to 10 nanometers thick.

16. CELL MEMBRANE
•The approximate composition of cell membrane is
55% proteins, 25% phospholipids, 13%
cholesterol 4% other lipids & 3% carbohydrates.
The plasma membrane of RBC contains
approximately 52% proteins, 40% lipids & 8%
carbohydrates.
• Its basic structure is a lipid bilayer, which is a
thin double layered film of lipids, each layer
only one molecule thick, that is continuous
over the entire cell surface.

17. •Most abundant class of membrane lipids is phospholipid &
less abundant class of membrane lipids is sphingolipids.
•Membrane lipids are amphipathic in nature.
1. HYDROPHILIC END 2. HYDROPHOBIC END
•Phospholipids and cholesterol make this bilayer almost
entirely impermeable to water & water soluble substances
as ions, glucose, Urea & others.
•Fat soluble substances such as oxygen, carbondioxide
& alcohol can penetrate this portion of the membrane.

19. CELL MEMBRANE
•A special feature of lipid bilayer is that it is a
fluid & not a solid. Therefore, portions of
membrane can literally flow from one point to
another point in the membrane.
•It is semi permeable and acts as a barrier.

21. CELL MEMBRANE PROTEINS
•These are the glycoproteins.
1.Integral Proteins:
That penetrate into lipid bilayer which
protrude all the way through the cell. These
proteins provide structural pathways through
which water & water soluble substances,
especially ions, can diffuse between the extra
cellular & intracellular fluid, thus providing so
called cell membrane pores. some of them can
also act as enzymes.

22. CELL MEMBRANE PROTEINS
2.Peripheral proteins:
Which are attached only to integral proteins
& do not penetrate or occur inside the
membrane. They almost act as enzymes &
control many of the chemical reactions inside
the cell
3. Lipid anchored proteins:
They are located outside the lipid bilayer but
are covalently linked to a lipid molecule that
is situated within bilayer.

23. THE MEMBRANE CARBOHYDRATES
•They occur almost outside the membrane.
•These are the glyco-portion of protruding
glycoproteins molecules.
•Depending on the species & cell type, the
carbohydrate contents of plasma membrane
ranges b/w 2 to 10% by weight.

24. Chemical Structure of Plsma Membrane

25. CYTOPLASM & CYTOSOL
•Cytoplasm is viscous & collidal material
which is more or less transparent in visible
lights.
•Cytoplasm is composed of an aqueous
solution the cytosol, & a variety of
insoluble suspended particles.
•The cytosol is not simply a dilute aqueous
solution it has a complex composition & gel
like consistency.

26. DISSOLVED SUBSTANCES IN CYTOSOL
Dissolved in the cytosol are:
•Many enzymes & the RNA molecules
•The monomeric subunits (AA & nucleotide)
•Small organic molecules called metabolites
•Intermediates in metabolic pathways
•Coenzymes
•Inorganic ions.

27. MEMBRANE BOUNDED ORGANELLES
•Nucleus
•Endoplasmic reticulum
•Mitochondria
•Lysosome
•Golgicomplex
•Peroxisomes

28. Nucleus
•It is the control center of the cell .
•It controls both chemical reactions and
reproduction of the cell.
•The nucleus contains more than 95% of the cell's DNA.
•A double membrane structure, nuclear membrane
separates the nucleus from the cytosol.

31. Endoplasmic Reticulum
•The endoplasmic reticulum is a network of folded
membranes that form channels.
•The Endoplasmic Reticulum makes protein and lipid
components.
•Consists of a smooth ER and a rough ER.
•This organelle is responsible of moving proteins and
other carbohydrates to the Golgi Apparatus,
lysosomes, and other places.

33. Rough Endoplasmic Reticulum
•The RER is dotted with ribosomes.
(Which is why it is called “rough.”)
•The RER is involved with protein
production, protein folding, quality
control and dispatch.
•The RER is involved with the
synthesis of proteins. They
produce and process specific
proteins at ribosomal sites.
•Consists of network-like tunnels
with tubules, vesicles and cisternae
which is held together by the
cytoskeleton of the cell.

34. Smooth Endoplasmic Reticulum
•SME is more tubular then RER and forms a
separate interconnecting network. (Is found
evenly distributed among the Cytoplasm.)
•SME has no ribosomes on it.
•Smooth ER manufactures lipids and in some cases
the metabolism of them and associated products.

35. THE MITOCHONDRIA
•It is called the “powerhouse” of the cell.
• The number of mitochondria per cell varies from less than a
hundred to many thousand depending upon the amount of
energy required by each cell .
•It is mainly composed of outer membrane & inner membrane.
•The liberated energy is used to synthesize a high energy
substance called (ATP). ATP is then transported out of the
mitochondrion & diffuses throughout the cell to release its
energy wherever it is needed for performing cellular
functions.
•Mitochondria are self-replicative.

36. Cross - Section

37. Respiratory Chain

38. GOGI COMPLEX
The name comes from Italian anatomist Camillo Golgi,
who identified it in 1898.
It is closely related to the ER. Its membrane is
similar to that of SER.
It is composed of four or more stacked layers of
thin ,flat vesicles lying near the nucleus (cisternae).
It is very prominent in secretory cells.

40. Functions of Golgi Apparatus
1.They function mainly in association with the ER.
2.They are concerned with cell secretions .
3.The proteins or enzymes that have to be transported
out of the cell, pass through Golgi apparatus.
4.Carry out the modification of lipids and proteins
5.Most important function is to modify the proteins and
lipids by adding corbohydrates and converting them into
Glycoproteins and Glycolipids.
6.Storage and packaging of materials that will
be exported from the cell.

41. THE LYSOSOMES
•The lysosomes provide an intracellular digestive
system that allows the cell to digest & remove
unwanted substances & structures especially damaged
and foreign structures such as bacteria.
•Its diameter is 250-750 nm.
•Lysosomes are spherical organelles that contain
enzymes (acid hydrolases). They break up food so it is
easier to digest.

42. Lysosomal Enzymes
•Some important enzymes found within
lysosomes include:
•Lipase, which digests lipids
•Amylase, which digest carbohydrates (e.g.,
sugars)
•Proteases, which digest proteins
•Nucleases, which digest nucleic acids

43. Lysosomal Enzymes
•All these hydrolytic enzymes are produced in
the endoplasmic reticulum, and to some
extent in cytoplasm are transported and
processed through the Golgi apparatus.
•And through golgi apparatus they pinch off as
single membrane vesicles.

44. •Lysosomes are sometimes called "suicide bags“
•A lysosome is a membrane bag containing
digestive enzymes
•The digested food can then diffuse through the
vacuole membrane and enter the cell to be used
for energy or growth.

45. Lysosomes
Lysosomes are the cells' garbage disposal
system. They are used for the digestion of
macromolecules from phagocytosis (ingestion of
other dying cells or larger extracellular material,
like foreign invading microbes) .

46. Lysosomes
•Lysosomes are responsible for autolysis and
programmed cell death called apoptosis.
•Intracellular digestive system. It digests
oForeign particles
oUnwanted substances
oDamaged structures of the cell.

47. Lysosomes
•Lysosomes pick up foreign invaders such
as bacteria, food and old organelles and
break them into small pieces that can
hopefully be used again.
•The only thing that keeps the cell itself
from being digested is the membrane
surrounding the lysosomes.

48. PEROXISOMES
•Peroxisomes are similar physically to
lysosomes.
•First observed by electron microscopy in animal
cells (1950s)
•Oxidase enzymes present in large quantity in
peroxisomes, oxidize many substances
poisonous to the cell.

49. PEROXISOMES
•The oxidases combine oxygen and
hydrogen ions to form H
2
O
2
.
•H
2
O
2
is used by catalase enzyme.

50. DIFFERENCE B/W LYSOSOMES & PEROXISOMES
LYSOSOMES
•They are formed by
Golgi apparatus.
•They contain enzymes
hydrolases
PEROXISOMES
•They are formed by
budding off from the SER.
•Enzymes present are
oxidases

51. THANKS ?

52. Cytoskeleton
•Acts as skeleton and
muscle
•Provides shape and
structure
•Helps move organelles
around the cell
•Made of three
types of filaments:
•microtubulues,
•microfilaments,
•intermediate filaments.

53. MICROFILAMENTS
The febrile proteins of the cell cytoplasm are organized
in to microfilaments or microtubules.
At first they are present in dissolved form in
the cytoplasm.
Then they are polymerized to form microfilaments.
Microfilaments are made up of contractile actin
protein linked to the inner surface of the plasma
membrane.
The are involved in internal cell motion.
Muscle contraction through out the body is due to
microfilaments present in the muscle cells.

54. MICROTUBULES
Microtubules are hollow, cylindrical structures.
They are made up of protein called TUBULIN
•Primary function of microtubules is to act as
cytoskeleton, providing rigid physical structures
for certain parts of cell.
•The are involved in internal cell motion.

--------------------------

55. An example of the role of microtubules in transporting
organelles. The peroxisomes are shown in green and MT in red
The machinery that moves materials and organelles within cells
Peroxisome
Microtubule (MT)

56. Transport through cell
membranes
The phospholipid bilayer is a good barrier around
cells, especially to water soluble molecules. However,
for the cell to survive some materials need to be
able to enter and leave the cell.
•There are 4 basic mechanisms:
1.DIFFUSION and FACILITATED DIFFUSION
2.OSMOSIS
3.ACTIVE TRANSPORT
4.BULK TRANSPORT

57. •Diffusion is the net movement of molecules (or
ions) from a region of their high concentration to
a region of their lower concentration.
The molecules move down a concentration gradient.
Molecules have kinetic energy, which makes them move
about randomly.
As a result of diffusion molecules reach an equilibrium
where they are evenly spread out.
This is when there is no net movement of molecules
from either side.

58. Diffusion through a membrane
Cell membrane
Inside cell
Outside cell

59. Diffusion through a membrane
Cell
membrane
Inside cell
Outside cell
diffusion

60. Diffusion through a membrane
Cell
membrane
Inside cell
Outside cell
EQUILIBRIUM

61. What determines the rate of diffusion?
There 4 factors:
1.The steepness of the concentration gradient. The bigger
the difference between the two sides of the membrane
the quicker the rate of diffusion.
2.Temperature. Higher temperatures give molecules or ions
more kinetic energy. Molecules move around faster, so
diffusion is faster.
3.The surface area. The greater the surface area the
faster the diffusion can take place. This is because the
more molecules or ions can cross the membrane at any one
moment.
4.The type of molecule or ion diffusing. Large molecules
need more energy to get them to move so they tend to
diffuse more slowly. Non-polar molecules diffuse more
easily than polar molecules because they are soluble in the
non polar phospholipid tails.

62. Facilitated diffusion
•Large polar molecules such as
glucose and amino acids,
cannot diffuse across the
phospholipid bilayer. Also
ions such as Na
+
or Cl
-
cannot
pass.
•These molecules pass
through protein channels
instead. Diffusion through
these channels is called
FACILITATED DIFFUSION.
•Movement of molecules is
still PASSIVE just like
ordinary diffusion, the only
difference is, the molecules
go through a protein channel
instead of passing between
the phospholipids.

64. Facilitated Diffusion through a membrane
Cell
membrane
Inside cell
Outside cell
Protein channel

65. Facilitated Diffusion through a membrane
Cell
membrane
Inside cell
Outside cell
Protein channel
diffusion

66. Facilitated Diffusion through a membrane
Cell
membrane
Inside cell
Outside cell
Protein channel
diffusion
EQUILIBRIUM

68. Active Transport
•Movement of molecules and ions against their
concentration gradients.
•From lower to higher concentrations.
•Requires ATP
•Passive transport Active transport
hig
h
low
Weeee!!!
high
low
This is
gonna be
hard work!!

69. •Two Types of Active Transport:
–Primary
–Secondary
Transport of small substances is of 3 types.
•Uniport
•Symport
•Antiport

70. • EXAMPLES:( primary active transport)
•Ca pump
• It is an example of uniporter pump.
• H-K ATPase/Proton pump.
• It is an example of antiporter pump.
• Na-K ATPase/ Na K Pump
• It is example of antiporter pump.

71. Primary Active Transport
•ATP directly required for
the function of the carriers.
•Molecule or ion binds to
carrier site.
•Binding stimulates
phosphorylation
(breakdown of ATP).
•Conformational change
moves molecule to other
side of membrane.

73. Secondary Active Transport
•Coupled transport.
•Energy needed for
uphill movement
obtained from downhill
transport of Na+.

74. COTRANSPORT
•It also uses the process of diffusion.
•In this case a molecule that is moving naturally
into the cell through diffusion is used to drag
another molecule into the cell.
•Example: Glucose hitches a ride with sodium.

76. THANK YOU