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Topic 1A- Biological Molecules
Created
Class

@February 3, 2025 8:32 PM
Cells to Systems

Carbohydrates
A lot of carbs are polymers
Big, complex molecules made of smaller molecules called monomers
which join together
Examples
Monosaccharides
Creates monomers
Glucose is a monosaccharide containing 6 carbon atoms
Splits into Alpha and Beta Glucose
Amino acids
Nucleotides

Condensation Reaction
Two molecules join together and water molecule is released as biproduct
Reaction links monosaccharides together
Water molecule release creates glycosidic bond
Two monosaccharides joining creates disaccharide

Hydrolysis Reaction

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Breaks polymers
Removes chemical bond between monomers using water
Opposite of condensation reaction

Starch
Glucose is energy source for cells, excess is stored as starch in plants
If plant needs more energy, starch is broken down for glucose release
Consists of amylose and amylopectin
Amylose
Long chain of alpha glucose
Coiled structure due to glycosidic bonds
Structure makes it ideal for storage as it’s more compact
Amylopectin
Long branched chain of alpha glucose
Side branches on the structure allow multiple access points for
glycosidic bonds to be broken down
Results in quick glucose release
Energy source is insoluble in water, so water potential is not affected
and swelling due to osmosis is avoided
Good for storage

Glycogen
Energy source for animals
Known as alpha glucose, known as glycogen when stored as excess

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Similar structure to Amylopectin but contains more side branches, leading
to quicker release of energy
Compact shape

Cellulose
Long chain of beta glucose
Bonding of molecules creates cellulose chains
Chains are fused together by Hydrogen bonds forming microfibrils
Microfibrils are strong fibres supporting cellulose structure

Triglycerides
Type of lipid
Made of glycerol and 3 fatty acids
Fatty acids contain hydrophobic tails making molecule insoluble in water
Formed by condensation reactions
Structure
Hydrocarbon tails contains a lot of chemical energy
Energy is released when tail breaks
Insoluble so water potential is unaffected
Tails being hydrophobic means molecules clump together
Tails face inwards and protect themselves from surrounding water

Fatty Acids are Unsaturated or Saturated
Saturated fats don’t have double bonds between carbon atoms

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Unsaturated fats have at least one double bond, creates ‘kink’ between
carbons

Phospholipids
Found in cell membranes
Structure is similar to triglycerides, but one fatty acid is replaced with
phosphate group
Phosphate group is hydrophilic, attracts water
Structure
Make up the bilayer of cell membranes, controlling what goes in and
exits the cell
Heads are hydrophilic and tails are hydrophobic
Creates double layer with heads facing towards water
Bilayer centre is hydrophobic, water soluble molecules can’t easily
pass
Cell membrane is a barrier

Proteins
Made of amino acids, type of monomer
Two amino acids create a dipeptide
More than two amino acids create a polypeptide
Multiple polypeptides create proteins
Different Amino acids have different variable groups
Carboxyl group -COOH
Amine/amino group -NH2

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R group

Condensation Reaction
Amino acids fusing together via condensation reaction create
polypeptides
Water molecule is released at the end of the process
Polypeptide bond forms between amino acids

Structural Levels
Primary Structure
Amino acids create polypeptide chain
Secondary Structure
Chain is not flat or straight
Hydrogen bonds between amino acids force it to coil into alpha
helix, or folds into beta pleated sheet
Tertiary Structure
Coiled or folded chain can coil or fold even further
Contains more and different bonds between amino acids
Bonds include Hydrogen and ionic
Disulfide bridge forms when two cysteine (Amino acids) are close
together
Quarternary Structure
Consists of different polypeptide chains
Held together by lots of bonds

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Proteins with Functions
Enzymes
Sphere like shape
Soluble
Involved in metabolic processes
Antibodies
Involved in immune responses
Made of two light and two long polypeptide chains
Contains variable regions
Amino acid sequences can vary
Transport Proteins
Contains hydrophobic and hydrophilic amino acids
Causes protein to fold and create a channel
Responsible for transporting molecules and ions across membrane
Structural Proteins
Very strong
Made of long peptide chains parallel next to each other
Examples include keratin and collagen

Biological Catalysts (Enzymes)
Catalyses metabolic reactions at cellular level and for whole organism
Affects structures and functions in organism
Action of an enzyme can take place inside or outside of a cell
Are proteins

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Contains active site which has specific shape and allows substrate to bind
to it
Structure is specific due to tertiary structure

Enzymes Reduces Reaction Activation Energy
Activation Energy
Amount of energy required to initiate a reaction
Enzymes reduce activation energy required for reactions
Allows reactions to happen at lower temp and also speeds up rate of
reaction
Enzyme Substrate Complex
Repulsion is reduced as two substrates join together while each
substrate molecule bonds to enzyme
Enzyme catalysing breakdown reaction applies stress on bonds
between substrates leading to easier breakage

Lock and Key Model
Substrate fits into enzyme like a key fitting a lock

Induced Fit
Active site changes shape for substrate
Substrate can be any shape and fit active site

Enzyme Tertiary Structure

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Enzymes are specific
Active site only carries single complimentary substrate
Shape of active site is decided by tertiary structure
Every enzyme contains different tert

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