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Cell Bilogy ١
Lecture 2
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Cell Bilogy ٢
(amphipathic molecules : have one
hydrophobic end and one hydrophilic end
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Cell Bilogy ٣
4- Steroids
Steroids are lipids composed of fused ring structures (fourfour--ring system) ring system)
PerhydroPerhydrocyclocyclopentanopentanophenanthrene which are strongly hydrophobic , the hydroxyl phenanthrene group attached to one end of cholesterol is weakly hydrophilic (amphipatic molecules)
Cholesterol is an example of a steroid that plays a significant role in the structure of the cell membrane
In addition, cholesterol is the compound from which we synthesize sex hormones and vitamin D2
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Cell Bilogy ٤
Cholesterol
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Cell Bilogy ٥
5- Glycolipids & Glycoproteins
Consist of two hydrocarbon chains linked to polar head groups that contains carbohydrate ( Glucose or galactose or 2-10 oligosaccharides )
play an important role in Cell-cell recognition
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Cell Bilogy ٦
6-Sphingolipids
Sphingolipids are a complex family of compounds that share a common structural feature, a sphingoid base backbone that is synthesized from the amino acid serine and a long-chain fatty acids.
The major sphingoid base of mammals is commonly referred to as sphingosine ( Amino alcohol)
The major phosphosphingolipids of mammals are sphingomyelins,
they play an important role in the myelin sheath of nerve fibers.
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Cell Bilogy ٧
6-Sphingolipids
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Cell Bilogy ٨
7- Plasmogens (ether lipids)
They are mainly found in higher plants, fungi and anaerobic bacteria.
They are Structurally similar
Glycerophosphatides but they have ether
linkage instead of ester linkage in other lipids
They contain an unsaturated alcohol in ether
linkage instead of fatty acid in ester linkage at
C1 of glycero -3- phosphate
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Cell Bilogy ٩
Ether-linked Lipids
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Cell Bilogy ١٠
8 8 - - waxes waxes
Waxes form a thin layer over all the green tissue of plants that is both a chemical and a physical barrier.
This layer serves many purposes, for example to:
- limit the diffusion of water and solutes, while permitting a controlled release of volatiles that may deter pests or attract pollinating insects.
-
It provides protection from disease and insects, and helps the plants resist drought.
- Waxes also have a waterproofing and protective role for insects .
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Cell Bilogy ١١
9- Liposomes
Lipids may be broadly defined as hydrophobic or amphiphilic small molecules; the amphiphilic nature of some lipids allows them to form structures such as micelles, liposomes, or membranes in an aqueous environment
adding lipids to water can generate three most common configurations:
(1) liposome or lipid vesicles (a lipid bilayer surrounding water ):
water surrounding the bilayer and contained internally
(2) a micelle (polar heads in contact with water and hydrophobic tails clustered centrally).
(3) membranes in an aqueous environment
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Cell Bilogy ١٢
CARBOHYDRATES CARBOHYDRATES
Organic compounds that contain carbon, hydrogen, and oxygen at a ratio of 1:2:1
Carbohydrates range from small sugar molecules (monomers) to large polysaccharides
Sugar monomers are monosaccharides, such as glucose and fructose, mannose
These can be hooked together to form the polysaccharides
Importance of carbohydrates:
- The major nutrient of cells,
- They are energy-storage molecules, Plants store starch while animals store glycogen.
- Their breakdown provided both sources cellular energy and the
starting material for the synthesis of other cell constituents
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Cell Bilogy ١٣
Monosaccharides are the simplest carbohydrates
Represent the simplest carbohydrates
The carbon skeletons of monosaccharides vary in length
Glucose and fructose are six carbons long
Others have three to seven carbon atoms
( ( Trioses, Trioses , Tetroses Tetroses , , Pentoses, Pentoses , Hoxoses Hoxoses Heptoses) Heptoses)
-
Pentoses (C
5sugars): structural backbones of nucleic acids,
-
Hexoses (C
6sugars): monomeric constituents of cell wall polymers and energy reserves)
Monosaccharides have molecular formulae that are multiples of CH
2O. .
Monosaccharides, particularly glucose are the main fuels for cellular work
Monosaccharides are also used as raw materials to manufacture other organic molecules, Glucose is the starting compound for an important metabolic
pathway called cellular respiration. .
The formula of Glucose is C
6H
12O
6, its structure shows a number of hydroxyl groups (-OH), which make sugar an alcohol, and a carboxyl group (C=O)
depending on its position, makes it either aldose (glucose) or a ketose (fructose
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Cell Bilogy ١٤
Structural Formulas of a Few Common Sugars
Structural Formulas of a Few Common Sugars
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Cell Bilogy ١٥
Structural Formulas of a Few Common Sugars
Structural Formulas of a Few Common Sugars
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Cell Bilogy ١٦
ﻲﺋﺎﻨﺛ
ﻲﺴآورﺪﻴه نﻮﺘﻴﺳأ ) نﻮﺘﻴآ (
Dihydroxyacetone (a ketone (
ﺪﻴهﺪﻟاﺮﺴﻴﻠﺟ )
زوﺪﻟا ( Glyceraldehyde
(an aldose
( C C
C
O
C
H
C H 2O H
O H H
O H H
O H H
C C
C
O
C
C
C H 2O H H
O H H
H O H
O H H
O H H ﺔﻋﻮﻤﺠﻣ
ﺪﻴهﺪﻟا Aldehyde group
ﺔﻋﻮﻤﺠﻣ
ﺪﻴهﺪﻟا Aldehyde group
ﺔﻋﻮﻤﺠﻣ
نﻮﺘﻴآ Keto group
ﺔﻋﻮﻤﺠﻣ
نﻮﺘﻴآ Keto group
Triosesn=3
ﺔﻴﺳاﺪﺳ ﺔﻳدﺎﺣأ تاﺮﻜﺳ Hexosesn=6
ﺔﻴﺳﺎﻤﺧ ﺔﻳدﺎﺣأ تاﺮﻜﺳ Pentosesn=5
زﻮﺒﻳاﺮﻟا
Ribose
زﻮﺒﻳار ﻲﻘﻠﺣ
α-D-Ribose CH2OH
C CH2OH
O
C C
CH2OH
H OH
H O
C C C C C C
O HO H H OH H OH H OH
H H H OH C
C C C C C H OH HO H
H OH H OH H OH
H O H
زﻮﺘآﺮﻔﻟا Fructose ﻲﻘﻠﺣ زﻮآﻮﻠﺟ
α-D-glucose
زﻮﺘآﺮﻓ ﻲﻘﻠﺣ
Fructose زﻮآﻮﻠﺠﻟا
Glucose
ﺔﻋﻮﻤﺠﻣ
ﺪﻴهﺪﻟا Aldehyde group C
C C C C H OH
H OH H OH H OH
H
H O
OHCH2 O
HO OH H
H
HO CH2OH H
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Cell Bilogy ١٧
Disaccharides -
2
The source of the sweet taste
- Two monosaccharides (monomers) can bond to form a disaccharide by glycosidic bonds in a
dehydration reaction
An example is a glucose monomer bonding to a fructose monomer to form sucrose, a common disaccharide.
Two glucose monomers bonding together to form maltose
Glucose Glucose
Maltose
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Cell Bilogy ١٨
C C
C O C C
CH2OH
OH OH
OH OH H
H H
H H
C C
C O
C
CH2OH CH2OH
H HO
OH H OH
H +
H2O
C C
C O
C
CH2OH
H
OH H OH
H
C C
C O C C
CH2OH
OH OH
OH H
H H
H H
O
CH2OH
Glucose Fructose Sucrose (glucose α1,2
fructose)
+
glycosidic bond
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Cell Bilogy ١٩
-
3 Polysaccharide s
Polysaccharides are polymers of monosaccharides bonded together by
glycosidic bonds
They can function in the cell as a storage molecule or as a structural compound in cell walls
Animals and plants store sugars for later use. Plants store starch while animals store glycogen.
Polysaccharides are divided into two groups depending on its cellular function
1- Structural Polysaccharides:
Found inside and outside cells
Play critical roles in cell-cell recognition, cell protection and cell supporting
Example: Cellulose, Mannan, Hyaluronic acid , Peptidoglycans
2- Nutrient Polysaccharides
As storage molecules (starch, glycogen)
Polysaccharides are divided into two groups depending on its cellular structure
1- Homopolysaccharides :
Formed of one type of monosaccharides. Example: Cellulose, starch
Formed of more than one type of monosaccharides Examples: (Hyaluronic acid , hemicellulose)
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Cell Bilogy ٢٠
Polysaccharides
Polysaccharides: carbohydrates containing many monomeric units (monosaccharides) connected by glycosidic bonds
Disaccharides: carbohydrates containing two monosaccharides
Trisaccharides: carbohydrates containing three monosaccharides
Oligosaccharides: carbohydrates containing several monosaccharides
Polysaccharides: extremely long-chain carbohydrates
Glycosidic bonds: covalent bonds linking sugars together in a polysaccharide
Two possible geometric orientations: alpha (α) and beta (β)
Configuration of bond imparts different functional properties to
macromolecules composed of the same building blocks (e.g., starch and cellulose)
The principle linkage is 1-4 glycosidic bond
1-6 glycosidic bond leads to the formation of branches joining two separated 1-4
linkage chains
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Cell Bilogy ٢١
The Glycosidic Bond and Polysaccharides
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Cell Bilogy ٢٢
