Transcript Amino acids - Zanichelli

Sylvia S. Mader
Immagini e
concetti
della biologia
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A3 – Biological
molecules
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Carbon is the Basic Element of
Biomolecules
A single bacterial cell may contain
up to 5000 different types of
organic compounds.
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Carbon needs four electrons
Every single carbon can bond with four other atoms
Carbon-carbon bond is a covalent and stable bond, so it can
form very long and strong carbon chains.
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The great variety of biomolecules
Functional
groups
are
specific combinations of atoms
and confer typical features to
the molecules.
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Isomers
Chemical compounds with identical molecular formulas but
different arrangements of atoms (or functional groups).
Isomers react differently in chemical reactions
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Macromolecules
Carbohydrates, lipids, proteins and nucleic acids are
large molecules composed by molecular subunits linked
together.
Category
Carbohydrates*
Lipids
Proteins*
Nucleic acids*
MACROMOLECULES
Example
Subunit(s)
Polysaccharide
Monosaccharide
Fats
Glycerol and fatty acids
Polypeptide
Amino acids
DNA or RNA
Nucleotide
*The biggest macromolecules are polymers, large molecules composed of repeating
structural units (monomers), normally connected by covalent bonds
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Polymers
In the synthesis of a polymer, enzymes attach monomers
to one another. This reaction is named dehydration as a
molecule of water is freed.
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Polymers
The opposite reaction is the degradation of a polymer. During this
process a molecule of water is used to separate the two molecules.
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Carbohydrates
Organisms use carbohydrates as instant sources of
energy and structural materials.
Carbohydrates are composed of
Carbon (C), Hydrogen (H) and Oxygen (O)
with the ratio
1:2:1
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Carbohydrates
Simple carbohydrates, known as sugars, can be:
•monosaccharides (a single molecule);
•disaccharides (two molecules);
•polysaccharides (several monosaccharides).
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Monosaccharide and disaccharides
Simple carbohydrates provide quick energy
Glucose is a simple sugar and a major source of energy for
living organisms with formula C6H12O6.
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Monosaccharide and disaccharides
Sucrose is an important disaccharide in plant’s nutrients
circulation. It is composed by two monosaccharides
(glucose and fructose) joined through dehydration.
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Monosaccharide and disaccharides
Ribose (C5H10O5) and deoxyribose (C5H10O4) are found in
RNA and DNA respectively and are both monosaccharides.
Lactose is a disaccharide found in milk and is formed from
glucose and galactose (an isomer of glucose).
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Polysaccharides
Starch: supply sugar contained in plants.
Glycogen: supply sugar contained in animals and fungi.
Cellulose: structure sugar contained in plants.
Chitin: structure sugar contained in some animals.
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Lipids: energy storage and protection
Lipids are insoluble in water as they are nonpolar.
Fats and oils are rich energy-storage lipids.
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Lipids: fats and oils
Unsaturated: have one or more double bonds in their fatty
acid chain.
Saturated: no double bonds in the fatty acid chain.
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Phospholipids: cell membrane
component
A phosphate group replaces
the third fatty acid.
Hydrophilic “head”
Hydrophobic “tail”
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Steroids and waxes
Steroids serve as cell membrane
component or have hormonal function.
Waxes are used to prevent water loss
and assist in skin maintenance.
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Proteins are versatile biomolecules
1.Support: as keratin (in hair and fingernails) and
collagen (in ligaments and tendons).
2.Metabolisms: as enzymes (catalyze reaction).
3.Transport: carrier proteins in the plasma membrane
allow substances to enter or exit cells.
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Proteins are versatile biomolecules
4.Defense: antibodies destroy
agents and prevent infections.
diseases-causing
5.Regulation: some hormones, such as insulin, are
regulatory proteins.
6.Motion: actin and myosin compose muscular tissues.
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Proteins: sequences of amino acids
Amino acids are essentially composed of:
•a central carbon
•an amino group (-NH2)
•an acid group (-COOH)
•an R-group
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Polypeptides
A single protein contains one ore more polypeptides
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Amino acids differ on the R-group
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Protein structure
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Nucleic Acids carry coded information
Nucleotides are composed of a sugar, a phosphate group
and a nitrogen base (Adenine, Guanine, Cytosine, Thymine,
Uracil).
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RNA - RiboNucleic Acid
Convey coded information from DNA
to ribosomes for the protein synthesis.
Pentose sugar = ribose
Nitrogen bases = are A, G, C and Uracile.
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DNA - DeoxyriboNucleic Acid
Is located in the nucleus, contains the
genetic information and has a double
helix structure.
Pentose sugar = deoxyribose
Nitrogen bases = are A, G, C and Thymine.
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Nucleic Acids
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ATP: the energy currency
ATP (adenosine triphosphate) consists of three parts:
1. An adenine (A) base;
2. A five-carbon ribose;
3. Three phosphate groups linked by covalent bonds.
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ATP: the energy currency
When the covalent bond of the third phosphate group is
broken down by an enzyme, energy is released.
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