CHAPTER 4: CHEMICAL COMPOSITION OF THE CELL

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CHAPTER 4CHEMICAL COMPOSITION OF THE CELL
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• ELEMENT IN THE CELL
• There are about 92 element occurring naturally in
  nature.
• From these 92 element, only about 25 element are
  needed to build living organisms.
• Not all these element found in all living cell.
• Main element (CHON) are the most frequently found
  elements in cells, forming about 96 of the human
  body mass.
• Trace-elements are the elements are found in
  small quantity in cells, but are important in
  biological processes.

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CHEMICAL COMPOUND IN THE CELL

• Chemical compounds in the cell can be divided
  into two major group
• Organic
• Inorganic
• Organic compounds are
• Chemical compounds contain carbon (exception are
  carbon monoxide, carbon dioxide, carbides and
  carbonates which are typically considered as
  inorganic)
• Are usually found in and originate from living
  organism.
• Usually consist of macromolecules (large
  molecules).
• Inorganic compounds are
• Chemical compounds that do not contain carbon
• Usually a smaller and simpler than organic
  compounds
• Founds in cells water, acids, alkalis and
  mineral salts

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• There are 4 main group of organic compounds in
  cells
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
• Carbohydrates
• The carbohydrates are made up of carbon, hydrogen
  and oxygen. The ratio of hydrogen to oxygen atoms
  in a molecule usually 21.
• Many carbohydrates have the general formula
  CX(H2O)Y,where x is approximately equal to y.
• Three basic types of carbohydrates are
  monosaccharide, disaccharides and polysaccharides

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• Monosaccharide
• Monosaccharide also called simple sugar
• The common monosaccharide are six-carbon sugar
  with a molecular formula of C6H12O6
• Example of monosaccharide are glucose, fructose
  (fruit sugar) and galactose
• Glucose is the most common monosaccharide and
  respiratory substrate
• Monosaccharide are sweet-tasting crystalline
  substances which are soluble in water

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• Disaccharides
• Disaccharides are formed from two monosaccharide
  molecules combining together with the elements of
  a molecule of water. The chemical reaction of the
  formation is known as condensation.
• The general formula of a disaccharides is
  C12H22O11
• Disaccharides also called double sugar.
• Disaccharides can be broken down to their
  constituent monosaccharide by a chemical reaction
  involving the addition of water. The reaction is
  know as hydrolysis.

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• Like monosaccharide, they are sweet-tasting
  crystalline substances that are soluble in water.
• The most common disaccharides are maltose,
  lactose and sucrose.

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• Polysaccharides
• Many monosaccharide molecules join together in a
  condensation reaction (with the removal of water
  molecules) to form a large polysaccharides
  molecules.
• Polymerisation is the process of condensing many
  individual monosaccharide molecules to form a
  large polysaccharides molecules.
• In polymerisation, the individual monosaccharide
  molecule are called monomers.
• Polymerisation of monosaccharide forms
• Glycogen in humans and animals
• Starch and cellulose in plants

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• Sub unit Glucose
• Consists of two components.
• Unbranched, helical chains of glucose units
• Branched chains of glucose units
• Major storage of carbohydrate in plants

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glucose
glycogen

• Sub unit Glucose
• Molecules with many side branches
• Major storage of carbohydrates in animals and
  fungi, for
• examples, in muscle cells and liver cells

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glucose
cellulose
Straight unbranched chain of glucose units Plant
cell wall
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• Reducing and non-reducing sugar
• Some sugars act as mild reducing agents
• Two common test reagent to test for reducing
  sugar are
• Benedicts reagent (alkaline solution of CuSO4)
• Fehlings reagent (alkaline solution of CuSO4)
• c) Reducing sugars reduce Cu² (blue solution)
  to Cu (brick red precipitate) in both reagents.

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• Proteins
• Proteins are compounds of these element carbon,
  hydrogen, oxygen, nitrogen sulphur and
  phosphorus.
• Amino acids are the subunits of all proteins.
• Each amino acids carries two functional group
• A carboxyl group (- COOH) which is acidic and
• An amino group (-NH2) which is basic.
• COOH carboxyl group
• C
• NH2 amino
  group

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• Two amino acids can combine together to form a
  dipeptide by a condensation reaction between the
  carboxyl group of one and the amino group of the
  other. The resulting a bond liking the two amino
  acids that is called a peptide bond.

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• Long chains of amino acids are called
  polypeptides.
• A polypeptide is formed by the condensation
  reaction of many amino acids, with the removel of
  water.
• A polypeptide chain can also be hydrolysed, with
  the addition of water molecules to form
  individual amino acids.
• PROTEIN STRUCTURE
• Primary-linear sequence of amino acids
• Secondary structure- forming ahelixor pleated
  sheet.
• Tertiary structure- compact structure
• Quaternary structure- 2 or more tertiary structure

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• LIPIDS
• Lipids a diverse group of substance that contain
  carbon, hydrogen and oxygen. The proportion of
  oxygen is lower than that in carbohydrates. For
  example, the general formula of stearic acid is
  C18H36O2.
• All lipids are insoluble in water
• Lipids dissolve readily in other lipids and in
  organic solvent such as ether and ethanol.
• The main types of lipids are
• Fats
• Oils
• Waxes
• Phospholipids
• steroids

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• Fats and oils
• Fats are solid at room temperature (20C),
  whereas oil are liquid
• Each molecule of fats or oils is made up of one
  glycerol combine with three fatty acids which may
  be the same or may be different. Three molecule
  of water are remove in this condensation reaction.

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• These molecules of fats and oils are known as
  triglycerides.
• Fats often contain only saturated fatty acids.
• Oils usually contain unsaturated fatty acids.
• In a saturated fatty acids, the carbon atoms are
  bonded to the maximum number of other atoms.
  Saturated fatty acid has only single bond and the
  hydrocarbon chain is relatively straight.
• Unsaturated fatty acids has double bond in the
  form of CHCH- in the hydrocarbon chain. Fatty
  acids those with two or more double bond are
  called polyunsaturated fatty acids.

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Type of fatty acids Example Structural formula
Saturated Stearic acid CH3(CH2)16COOH
Unsaturated Oleic acid CH3(CH2)7CHCH(CH2)7COOH

• Fats and oils function efficiently as energy
  storage material. Fats and oils provide 38kJ per
  gram, while carbohydrates can provide only 17 kJ
  per gram.

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• Waxes
• Waxes are similar to triglycerides, but the
  fatty acids are bonded to long-chain alcohols
  rather than glycerol
• Waxes are usually hard solids at room temperature
• Waxes are used to waterproof the external surface
  of plants and animal. The cuticle of a leaf and
  the protective covering on an insects body are
  made of waxes.
• Wax is also a constituent of the honeycomb of bees

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• Phospholipids
• Phospholipids have a similar structure to
  triglycerides but one of the fatty acids is
  replaced by a phosphate group
• The end of the phospholipids molecule containing
  the phosphate group is hydrophilic. The other end
  containing the hydrocarbon chain of the fatty
  acids is hydrophobic.
• The hydrophilic end is soluble in water while
  hydrophobic is insoluble in water.
• Phospholipids bilayer from the basis of all cell
  membrane.

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• Steroids
• A steroid molecule has a complex ring structure
• Steroid occur in plants and animals
• Examples of steroids are cholesterol,
  testosterone, estrogen and progesterone.

Steroid Function
cholesterol Strengthens the cell membrane at high body temperature
testosterone Male reproductive hormone
estrogen and progesterone. female reproductive hormone
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• Saturated and and saturated fats
• Animal fats such as lard, butter and cream are
  example of saturated fats
• Vegetable oil such as olive oil and sunflower oil
  are example of unsaturated fats.

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Saturated fats Unsaturated fats
Similarities Similarities
Both are triglycerides They yield 38 kJ per gram Their molecules congregate into globule because of their hydrophobic properties Both are triglycerides They yield 38 kJ per gram Their molecules congregate into globule because of their hydrophobic properties
Differences Differences
Saturated fats Unsaturated fats
Higher melting point Lower melting point
Most are solid at room temperature Most are liquid at room temperature
More likely to cause disease of the heart and arteries Less likely to cause disease of the heart and arteries
More stable at room temperature and less readily become rancid Unstable at room temperature and less readily become rancid
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ENZYMES

• Enzymes are protein molecules act as biological
  catalysts. They speed up the rate of metabolic
  reactions and do not chemically changed at the
  end of the reaction
• The substance whose reactivity is increased by an
  enzymes is knowing as a substrate

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THE GENERAL CHARACTERISTICS OF ENZYMES

• Enzymes speed up the rates of biochemical
  reactions in cells.
• Only a small amount of enzymes is needed to
  catalyse a lot of substrate.
• Enzymes are very specific each class of enzymes
  will catalyse only one particular reaction.
• Enzymes are not used up or destroyed in the
  reactions that they catalyse, but can be reused
  again.
• Enzymes catalyse reversible reactions
• Many enzymes are only able to work with in
  presence of a coenzymes (or cofactor).
• Enzymes are effected by changes in temperature
  and pH

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NAMING OF ENZYMES

• An emzyme is named by taking its substrate name
  and adding the suffix -ase
• Example, protease catalyses the hydrolysis of
  protein.
• The -ase rule does not apply to enzymes
  discover before the -ase idea was introduced.
  For example, pepsin, rennin, ptyalin and tripsin.
• The modern classification of enzymes was decided
  by the International Union of Biochemistry (IUB)
  in 1961

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INTRACELLULAR AND EXTRACELLULAR ENZYMES

• Intracellular emzyme that catalyses reaction
  within a cell and formed by the free ribosome in
  the cytoplasm.
• Extracellular emzyme that leaves the cell and
  catalyses reaction outside the cell and
  synthesised by ribosome attached to the rough
  endoplasmic recticulum.

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MECHANISM OF ENZYMES ACTION

• Each enzyme molecule has a region with very
  precise shape called active site.
• The substrate molecule fit into the active site
  of the enzymes like a key into a lock, forming an
  enzyme-substrate complex, a temporary structure.
• Reaction take place at active site to form a
  product.
• The product have a different shape from the
  substrate and therefore repelled from a active
  site.

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• THERE ARE 4 FACTORS AFFECT THE ACTIVITY OF
  ENZYMES
• pH
• Temperature
• Concentration of enzyme
• Concentration of substrate
• The effect of pH on enzyme activity
• Each enzyme has a optimum pH at which its rate of
  reaction is the fastest. i.e. pepsin at pH
  2,(acidic) amylase pH 7 (neutral) and trypsin at
  pH 8-9 (alkaline)

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• The effect of temperature on enzyme activity
• The rate of reaction will increase up to maximum,
  known as optimum temperature.
• After the optimum temperature around 37ºC-40ºC,
  the rate of reaction falls quickly because of the
  bonds maintaining the structure of the enzyme
  start to break and the active site loses its
  shape.
• At 60ºC, enzyme activity will stop altogether
  because the enzyme is denatured

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• The effect of substrate concentration on enzyme
  activity
• Increase the substrate concentration will
  increase the chance of enzyme-substrate
  collision, and the rate of reaction will
  increase.
• Addition of substrate will not increase the rate
  of reaction anymore because the constant enzyme
  concentration becomes the limiting factor.

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• The effect of enzym concentration on enzyme
  activity
• When the concentration of enzyme increase, there
  are more chance enzyme-substrate collision. The
  rate of reaction increase linearly as long as no
  other factors are limiting.
• THE USES OF ENZYMES
• Enzyme can extracted from any living organism,
  and used either at home or in industry
• Enzymes that are commonly used in daily life
  are
• Papain-found in papaya used to tenderise meat
• Protease-used to tenderise meat and remove hair
  from the skin etc.

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CHEMICAL COMPOSITION OF THE CELL
What
Health problems
Leads to
Definition
Deficiency
How
Water
Mechanism

• Compound

Element
Consists of
Enzymes
Can be classified
Forms
Why
Includes
Lipid
Carbohydrate
Protein
Importance
Affected by
Form
Break down into
Factors
Simpler molecules