Cell Molecules

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CHAPTER 5 THE STRUCTURE AND FUNCTION OF
MACROMOLECULES
Polymer principles And Macromolecules
Page 62
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Introduction (Polymers principles)

• Cells join ???? smaller organic molecules
  together to form larger molecules.
• These larger molecules called macromolecules, may
  be composed of thousands of atoms and weigh over
  100,000 daltons.
• The four major classes of macromolecules are
  carbohydrates, lipids, proteins, and nucleic
  acids ( Will be studied later)
• Three of the four classes of macromolecules form
  chainlike ??? ??????? molecules called polymers.
• Most macromolecules are polymers
• Polymers consist of many similar or identical
  building blocks linked by covalent bonds.
• The repeated units are small molecules called
  monomers.

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• Monomers are connected by covalent bonds by a
  condensation reaction or dehydration reaction
  ????? ??? ?????.
• One monomer provides a hydroxyl group and
  
  the other provides a hydrogen to form water.
• This process requires energy and is aided by
  
  enzymes.

• The covalent bonds connecting monomers in a
  polymer are disassembled ????????? by hydrolysis
  ?????? ?????.
• In hydrolysis as the covalent bond is broken a
  
  hydrogen atom and hydroxyl group from a
  split
  water molecule attaches
  where the covalent
  bond used to
  be.
• Hydrolysis reactions dominate the digestive
  
  process, guided by specific enzymes.

Fig. 5.2a b, Page 63
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(Carbohydrates, Lipids, Proteins and nucleic
acids)
Mono-mer
Di-mer
Poly-mer
Polymer is a long molecule consists of a chain of
similar building molecules (monomers) covalently
bounded together.
Polymer can be built up ????????? by linking its
monomers by dehydration (removing H2O).
Polymer can be broken down ?????????? ??? to its
monomers by hydrolysis (adding H2O).
Page 62 63, Fig. 5.2
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1- Carbohydrates Fuel and Building Material (????
?????? ? ?????? )
1. Sugars, the smallest carbohydrates, serve as
fuel and carbon sources 2. Polysaccharides, the
polymers of sugars, have storage and structural
roles
Page 64-68
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• Carbohydrates include sugars.
• Monosaccharides, are the simplest carbohydrates
  (simple sugars).
• Disaccharides, double sugars, consist of two
  monosaccharides joined by a condensation reaction
  (dehydration).
• Polysaccharides, are polymers of monosaccharides.
• Monosaccharides have a carbonyl group and
  multiple hydroxyl groups.
• If the carbonly group (CO) is at the end of C
  chain, the sugar is called aldose (aldehyde
  sugar), if not, the sugars is called ketose
  (Ketone sugar).
• Glucose called aldose, and fructose called
  ketose. They are structural isomers.
• Monosaccharides may also exist as enantiomers.
• For example, glucose and galactose, both
  six-carbon aldoses, differ in the arrangement
  around asymmetrical carbons ??? ??????? ?????
  ???????.
• Monosaccharides, particularly glucose, are a
  major fuel for cellular work.

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1- Monosaccharides
Aldehyde sugars
Page 64, Fig. 5.3
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Ketone sugar
Page 64, Fig. 5.3
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• Monosaccharides are also classified by the number
  of carbons in the backbone.
• Glucose and other six carbon sugars are hexoses
  ?????.
• Five carbon backbones are pentoses ????? and
  three carbon sugars are trioses ?????.

Fig. 5.3, Page 64
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Monosaccharides are classified into -
A- Based on the location of CO
Aldoses are the monosaccharides of carbonyle
group (CO) at the end of C chain (e.g. Glucose).
Ketoses are the monosaccharides of CO carbonyle
group within the C chain (e.g. Fructose).
B- Based on the number of C in the skeleton
Triose (3C) e.g. Glyceraldehyde.
Pentose (5C) e.g. Ribose.
Hexose (6C) e.g. Glucose, Fructose and Galactose.
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2- Disaccharides
Consisted of 2 monosaccharide molecules during a
dehydration reaction ????? ??? ?????.
1- Maltose
2(C6H12O6)
C12H22O11
H2O
2 Glucose
Maltose
FIG. 5.5a, Page 65
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2- Lactose (milk sugar) consists of Glucose
Galactose.
3- Sucrose (table sugar) consists of Glucose
Fructose.
Fig. 5.5, Page 65
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3- Polysaccharides
Consisted of few hundreds to few thousands of
monosaccharides.
They have storage ??????? and structural ???????
roles.
Storage polysaccharides provide sugar for cell by
hydrolysis.
Structural polysaccharides serve as building
materials for the organism.
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I- Starch ( in plants)
A)- Storage ??????? Polysaccharides
A storage polysaccharide of plants (within
plastids).
It is consisted of thousands of ? glucose
molecules.
Thus, it gives glucose when hydrolysed ??????
????? by special enzymes in human .
Potatoes and grains are the major source of
starch.
Fig. 5.7, Page 67
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II- Glycogen ( in animal)
Stored in animal cells (e.g. liver and muscle
cells in Human).
It is consisted of thousands of glucose molecules.
Thus, it gives glucose when hydrolysed.
Fig. 5.7, Page 66
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I- Cellulose
B)- Structural ??????? Polysaccharides
It is the building material of plants (cell wall).
Forms the micro-fibrils and cell wall in plants.
It is consisted of thousands of ß glucose
molecules.
Human cannot digest it, but some bacteria and
protozoa can (e.g. in Termites and Cows stomach).
Fig. 5.7c, Page 67
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Arrangement of cellulose in plants
Fig. 5.8, Page 68
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• The enzymes that digest starch cannot hydrolyze
  the beta linkages in cellulose.
• Cellulose in our food passes through the
  digestive tract and is eliminated in feces as
  insoluble fiber.
• As it travels through the digestive tract, it
  abrades the intestinal walls and stimulates the
  secretion of mucus.
• Some microbes can digest cellulose to its glucose
  monomers through the use of cellulase enzymes.
• Many eukaryotic herbivores ????? ?????, like cows
  and termites, have symbiotic relationships with
  cellulolytic microbes, allowing them access to
  this rich source of energy.

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II- Chitin
It is the building material of the cuticle in
insects.
It is consisted of thousands of glucose molecules
with a N atom in one end.
It is used to manufacture the surgical threads.
Fig. 5.9, Page 68
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Carbohydrates
No. of C atoms
No. of sugar molecules