Lecture 2 Cell Biology

8/8/2019 Lecture 2 Cell Biology

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222Cell Bilogy 1

Lecture (2)Lipid

Carbohydrates


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222Cell Biolgy 2

Lipid categories

Lipids may be divided into the following categories:

fatty acyls

Glycerophospholipids

sphingolipids

Neutral fats

Plasmalogens

Steroids Waxes


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fatty acyls = fatty acid

They are made of a hydrocarbon chain

It terminates with a carboxylic acid group

It has a polar (hydrophilic end) and a non polar(hydrophobic end)

The carbon chain, typically between four to 24

carbons long (saturated or unsaturated)

The fatty acid is commonly used as abuilding block of more structurally complexlipids.

222Cell Bilogy 3


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222Cell Bilogy 4

Glycerophospholipids= phospholipid

One of components of the lipid bilayer of

cells

Play a role in metabolism and cell signaling

Neural tissue (including the brain) contains

relatively high amounts of

glycerophospholipids, and alterations in their

composition could lead to neurologicaldisorder


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Gglycerophospholipids

in biological membranes

222Cell Bilogy 5


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222Cell Bilogy 6

Steroids Asteroid is a type of organic compound that contains a

specific arrangement of four rings that are joined to

each other.

Examples of steroids include cholesterol, the sex

hormones estradiol and testosterone

Cholesterol is an example of a steroid that plays asignificant role in the structure of the cell membrane

Cholesterol is the compound from which wesynthesize sex hormones and vitamin D2


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222Cell Bilogy 7

Consist of two hydrocarbon chains linked to polar

head groups that contains carbohydrate (Glucose

or galactose or2-10 oligosaccharides )

play an important role in Cell-cell recognition

Glycolipids


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222Cell Bilogy 9

Lipids in water can generate three most commonconfigurations:

(1) liposome or lipid vesicles (a lipid bilayer surrounding

water ): water surrounding the bilayer and containedinternally

(2) a micelle (polar heads in contact with water andhydrophobic tails clustered centrally).

(3) Bilayer sheet


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222Cell Bilogy 10

CARBOHYDRATESCARBOHYDRATESO

rganic compounds that contain carbon, hydrogen, andoxygen at a ratio of1:2:1

Carbohydrates range from small sugar molecules

(monomers) to large polysaccharides

Sugar monomers are monosaccharides, such as glucose

and fructose, mannoseImportance of carbohydrates:

- The major nutrient of cells,- They are energy-storage molecules, Plants store starch

while animals store glycogen.- Their breakdown provide both cellular energy and the

starting material for the synthesis of other cell constituents


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222Cell Bilogy 11

Monosaccharides are 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

((TriosesTrioses,, TetrosesTetroses ,, PentosesPentoses,, HexosesHexosesHeptoses)Heptoses)


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222Cell Bilogy 12

Structural Formulas of a FewCommon SugarsStructural Formulas of a FewCommon Sugars


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222Cell Bilogy 13

Structural Formulas of a FewCommon SugarsStructural Formulas of a FewCommon Sugars


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222Cell Bilogy 14

Disaccharides-2

- Two monosaccharides

(monomers) can bond to

form a disaccharide byglycosidic bonds in a

dehydration reaction

An example

Two glucose monomers

bonding together to

form maltose

Glucose Glucose

Maltose


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222Cell Bilogy 15

H

2

OH

OHOH

OH

OH

H

H

H

H

H

O

C

CH2OH CH

2OH

HHO

OH

OHH

H

+

H

2

O

C C

C

O

C

CH2OH

H

OH

OHH

H

C C

C

OC

C

CH2OH

OHOH

OH

H

H

H

H

H

O

CH2

OH

Glucose Fructose Sucrose (glucose E1,2

fructose)

+

glycosidicbond

Glucose monomer can bond to a fructose monomer

to form sucrose, a common disaccharide.


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222Cell Bilogy 16

sPolysaccharide-3

Polysaccharides are polymers of monosaccharides bondedtogether by glycosidic bonds

Polysaccharides are divided into two groups depending onits cellular function

1-Structural Polysaccharides:

Found inside and outside cells

Play critical roles in cell-cell recognition, cell protection andcell supporting

Example: Cellulose, Chitin, Hyaluronic acid

2- Nutrient Polysaccharides As storage molecules (starch, glycogen)

Foods high in carbohydrates include breads, pastas, beans,potatoes, bran, rice, and cereals


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222Cell Bilogy 17

The carbohydrates (saccharides) are

divided into four chemical groupings Monosaccharides: only one molecule of sugar (monomer)

Disaccharides: carbohydrates containing two

monosaccharides Oligosaccharides: carbohydrates containing several

monosaccharides

Polysaccharides: extremely long-chain carbohydrates, it

contains many monomeric units (monosaccharides)

connected by glycosidic bonds


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222Cell Bilogy 18

The Glycosidic Bond and Polysaccharides

Glycosidic bonds: covalentbonds linking sugars together in

a polysaccharide

Two possible geometric

orientations: alpha (E) and

beta (F) Configuration of

bond

The principle linkage is 1-4glycosidic bond

1-6 glycosidic bond leads to the

formation of branches joining two

separated 1-4 linkage chains


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222Cell Bilogy 19

The Glycosidic Bond and PolysaccharidesThe Glycosidic Bond and Polysaccharides


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222Cell Biology 20

Cellulose It is a polymer of glucose that forms plant cell walls

cellulose is the most abundant organic molecule on

Earth


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222Cell Biology 21

Chitin

Is a polysaccharide used by insects and crustaceans tobuild an exoskeleton

Found in cell wall of fungi


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222Cell Biology 22

Glycogen

Is energy storage polysaccharide composed ofglucose, which is hydrolyzed by animals whenglucose is needed

Highly branched molecules


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222Cell Biology 23

Starch

Is energy storagepolysaccharide

composed of

glucose monomers

Ti is found in plants

Starch helix may be

unbranched or

branched


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222Cell Biology 24

Paramylum

Homopolsaccharides, found inE

uglina


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222Cell Biology 25

Dextrin

It is a branched polysaccharides , produced bysome bacteria


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222Cell Biology 26

Complex polysaccharides

Polysaccharides can combine with otherclasses of

macromolecules to form complex polysaccharides:

- Glycoproteins: polysaccharides + proteins

Glycolipids:

polysaccharides + lipids


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Good Luck

Dr Mona

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Lecture 2 Cell Biology