Biological molecules (chemical tests and nucleic acids) proteins and Lipids recap AS Biology [JM}
AS Level Biology - 1) Biological Molecules
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BIOLOGY AS LEVELREVISION 01
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1. BIOLOGICAL MOLECULESAnd the Components of Life
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Definitions
Organic Molecules: Any Compound containing Carbon and Hydrogen
Macromolecule: A large biological moleculeMonomer: A relatively simple molecules used
as a building for polymerPolymer: A giant molecule made up of many
subunits of polymer joined togetherPolarity: The uneven distribution of charge
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Introduction
4 Biological Molecules: Hydrogen, Carbon, Oxygen
Carbon – is able to join with up to 4 atoms – very versatile and stable – form chains/ ring structures
Monomer: A simple molecule – basic building block e.g. Monosaccharide, Nucleotides, amino acids
Polymer: Many repeating subunits of monomers joined together e.g. Polysaccharides, Nucleic Acid, Proteins
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Ionic vs. Covalent bond
Ion: Molecules that are charged
Ionic do not share electron
One donates electron to fulfill the other’s octate
One becomes – The other becomes + Hence, they become
charges
When they share electrons
When one molecule shares certain electrons with the other – both using them – to create a bond
Equally distributed – non-polar
Slightly charges - polar
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The Hydrogen Bond
The small charge between the H minus and Oxygen plus between different water molecules
This can work with any of the 3: F, O, N
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About Carbon
Doesn’t take up a lot of spaceCan combine with a lot of other moleculesNeed 4 extra electronsAlso not too reactive
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The Properties of Water
Hydrogen bonding qualitySolvent property – Derived from hydrogen
bondThermal Properties – High specific heating
capacity/ High heat of vaporization
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Solvent Property
Positively charged part of ions are attracted to the negatively charged part of the water molecules – causing hydrophilic substance to dissociate
The substance becomes hydrated
Dissolve: Glucose, amino acid, hemoglobin, enzymes, hormones, vitamins, respiratory gases
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CARBOHYDRATE
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Carbohydrates
Carbon, Hydrogen, OxygenUsed as a source of energy in the form
of glucoseStored in the form of starch/ GlycogenStructure in the form of cellulose (CH2O)n
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MonosaccharideSimple Sugar – Triose,
Pentose, HexosePentose (Ribose, Deoxyribose)Hexose (Glucose, Fructose,
Galactose)Pentose and Hexose have
long carbon chains that can form a stable ring structure
2 forms of chemicals – isomers (Alpha and Beta)
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Alpha and Beta
Carbon atom number 1 – has hydroxyl groupHydroxyl group could be above or below the
ring If above the ring: Beta glucose If below the ring: Alpha glucose
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Monosaccharides for energy
The Carbon-hydrogen bond is largeCan be broken down to make energyAssist the making of ATP
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Disaccharide
Joined by 1,4 glycosidic bond – condensation reaction (loses H2O)
Split by the adding of water – hydrolysis (gains H2O)
Maltose = Alpha Glucose + Alpha GlucoseSucrose = Alpha Glucose + FructoseLactose = Beta Galactose + Alpha Glucose
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Polysaccharides
Polymer: Many repeating subunits of monomer joined together to form a large molecule
Many monosaccharide form polysaccharide Starch, Glycogen, CelluloseThese are not sugars
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Starch
Mixture of Amylopectin and AmyloseAmylose: Many alpha-glucose linked by 1.4 –
helical structure (makes it compact)Amylopectin: Amylose with shorter chains of
alpha glucose with 1,6 glycosidic branches
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Glycogen
Amylose + Amylopectin – with more 1,6 chains
Shorter amylose chainsAllow it to be less compact – quicker releases
of energy in animal bodies
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Cellulose
A polymer of beta-glucoseTo connect by 1,4 glycosidic bond, one
glucose of a pair has to flip 180 degreesThis arrangement creates weak hydrogen
atom with an oxygen molecule in the same cellulose
The most abundant molecules in nature (in cell wall, also hard to break down)
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Cellulose
50 – 60 cellulose molecules are cross-linked side by side by hydrogen bond to form microfibrils
Microfibrils bundled up to form a fiber
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LIPID
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Lipids
Contain: Carbon, Hydrogen, OxygenExcept for glycerol – insoluble in waterDissolve in Chloroform/ BenzeneLess dense than water
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Lipids
TriglyceridePhospholipidsCholesterol
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Triglyceride
Glycerol (Three-carbon Alcohol)Fatty Acid (Acid)- A carboxyl group with carbonskeleton
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Triglyceride
Combination of glycerol(alcohol) and 3 fatty acid molecules
Glycerol: A three carbon alcoholEster bond is formed in the condensation
between an alcohol group and an acid groupCan have tails that are 14 – 22 carbon atoms
longLong tails – insoluble in water
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Saturated/ UnsaturatedFatty acid chains with
double bonds – are not saturated with hydrogen- they are bent in the middle – is called UNSATURATED (better for your body – liquid at room temperature hence accumulate less)
Fatty acid chains with no double bond – are saturated with hydrogen – is called SATURATED
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Functions of Lipids Energy Source (soluble/mobile respiratory substrate) –
Glycerol + Fatty Acid Insoluble energy store – Fats/ Oils Thermal insulation – fats Buoyancy – fats Protection for vital organs – fats Waterproofs – waxes for plants (Suberin, cutin) Solvent for certain vitamins (A,D,E,K) Cell membranes (Phospholipids, glycolipids, cholesterol)
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Biological functions of Triglycerides
Fat yields more energy than carbohydrates
They also yield water in metabolic reaction – desert animals
Fats of whales in Arctic and Antarctic regions
Blubber of seals/ walrus – help them float
Mammalian kidney has fat
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PROTEIN
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Proteins C, H, O, N 20 different types Bond: Peptide bond (Formed by condensation)
(broken by hydrolysis) One’s Carboxyl loses a hydroxyl group, the other’s Amine
loses a hydrogen atom A single protein can have 1 polypeptide chains or many
combined Synthesized in ribosomes, broken down (hydrolyzed) in
the stomach by protease
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Amino Acid
Organic molecules with carboxyl and amino groups
They differ in properties according to its R-group
E.g. Glycine – has hydrogen R-group
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The Primary Structure
A chain/ sequence of amino acid linked by peptide bond forming a polypeptide
A change in one amino acid can make a different protein
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The Secondary Structure
The structure of protein caused by the regular coiling or folding of a polypeptide or protein.
The chain coils up in a corkscrew shape – due to the hydrogen bond between the oxygen of the carboxyl group with the hydrogen of the amine group 4 places ahead of it. – a-helix
ProblemsElectrostatic chargesProlineTemperature
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The Secondary Structure
Beta Pleated SheetPolypeptide chains – adjacent Parallel or anti-parallel – R groups alternate pointing up/ down
Held together via hydrogen bond
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The Tertiary Structure
Fibrous:
Do not fold upon itself, long rod, strong structure, typically insoluble, (collagen, keratin)
Globular:
Polypeptide backbone folds upon itself, compact and spherical, typically water soluble (Hemoglobin, Enzymes)
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Globular ProteinH2O
H2O
H2O
H2O
HYDROPHILICHYDROPHILICHY
DROP
HILIC
HYDROPHILIC
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Globular ProteinH2O
H2O
H2O
H2O
Hydrophobic effect
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Globular ProteinH2O
H2O
H2O
H2O
Hydrogen bond between R groups side chains
Disulfide bond – between Sulfur
Ionic bondBetween ionized carboxyl,Amine groups
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Fibrous Protein
1. Sequence of polypeptide form an helical shape – not tightly wounded.
2. 3 of these chains are tied around each other by hydrogen bond and some covalent bond
3. Glycine is at every 3rd amino acid – the small size allow for tight wounding
4. They lie side by side – cross links are created – out of step to increase strength – strong bundle: fibril
5. Many fibrils = fibers
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Uses of Proteins
Transport – Hemoglobin, Myoglobin – transport protein in cells
Storage – OvalbuminEnzymesHormones Immune system – AntibodiesParts of the phospholipid membraneStructure – fibrous protein, collagen, keratinMuscle – Actin, Myosin