,The biological importance of weak interactions, organic
molecules in living organisms and their respective
functions, the role of enzymes.
1) Enzyme catalysis relies on weak forces to hold reactants in
favorable positions to (usually) stabilize the transition state of the
reactants and so push the reaction forward. The 'shape' of the active site
brings atoms of the enzyme into positions where London forces and
hydrogen bonds stabilize the favorable configuration for reactions.
2) Protein structures are maintained by hydrogen bonding, London
forces, ionic interactions and hydrophobic interactions.
1º structure – peptide bonds
2º structure - H bonds
3ª structure - disulphide bridges/bonds; hydrophobic interactions ~
London dispersion forces; ionic/electrostatic interactions
3) DNA strands are held together chiefly by hydrogen bonds and
hydrophobic interactions (base stacking). The bases in the DNA are apolar
(even though having a N) and can be divided into PURINES (adenine +
guanine) and PYRIMIDINE (thymine + cytosine). Hydrogen bonding is also
the chief mechanism of selecting the correct nucleotide in DNA replication
and transcription.
4) RNAs have folded secondary structures that are maintained by
hydrogen bonds and hydrophobic interactions (base stacking). This is
important in all classes of RNA (mRNAs have stability and other motifs,
tRNAs rely on their folded structure, rRNAs rely on weak forces for their
structures and catalytic activities).
5) Lipid bi-layer membranes are held together chiefly by
hydrophobic interactions between the aliphatic tails. The polar heads
provide hydrogen bond potential to allow interaction with surrounding
molecules.
6) Immune recognition is mediated by weak forces (ionic,
hydrophobic and hydrogen bonds) between proteins and carbohydrates.
GENERALLY IONIC BONDS ARE THE STRONGEST ONES!
,Functions of the Four Major Groups of Organic Molecules
Group Examples Functions
Carbohydrate Glucose 1. Short term energy source
“Sugars” Glycogen 2. Transport form in animal - long
term energy storage
Lipids Fats and oils 1. Components of membranes
“Esters” Carboxylic Acid + (phospholipids)
Alcohol 2. Long term energy storage
3. Insolation
Proteins Enzymes Organic catalysts and
Sucrase Digestive enzymes
Lactase Structural protein in hair
Keratin Structural protein in skin
Collagen
Nucleic acids DNA 1. Information molecule
RNA 2. Molecule of heredity
ATP 3. Director of metabolism
involved in protein synthesis
immediate source of energy for
cellular work
Enzymes
Are highly specific, catalyst structures that bring down the
ACTIVATION ENERGY necessary for a reaction to occur, making them occur
faster. They are mainly proteic though some can be made of RNA
(ribozymes), and they have both tertiary and quaternary structure that
must be preserved so it can function.
They have active sites that bind to the substract, in what is called
induced-fit model. Enzymes can only work in certain conditions, mainly
related to temperature and pH range. They can be "defeat" by 4 types of
inhibitors: competitive ones (a molecule blocks the active site so the
substrate has to compete with the inhibitor to attach to the enzyme), non
competitive inhibitors (a molecule binds to an enzyme somewhere other
, than the active site and reduces how effectively it works), uncompetitive
(it only attaches to the complex enzyme + substract, causing the Vm and
Km to decrease), irreversible inhibitors (binds to an enzyme and
permanently inactivates it).
An enzyme can also become saturated if all the available active sites
have been occupied, we say therefore it has reached it's maximum
reaction velocity. One of the important constants related to this
occurence is the "Km", which corresponds to half of the substrate
concentration at which the reaction is half of the maximum velocity.
• A small Km indicates that the enzyme requires only a small amount
of substrate to become saturated. Hence, the maximum velocity is
reached at relatively low substrate concentrations.
• A large Km indicates the need for high substrate concentrations to
achieve maximum reaction velocity.
• The substrate with the lowest Km upon which the enzyme acts as a
catalyst is frequently assumed to be enzyme's natural substrate,
though this is not true for all enzymes.
The cell as the basis of life.
All the basic functions of life:
• Movement
• Reproduction
• Sensitivity
• Growth
• Reproduction
• Excretion
• Nutrition
molecules in living organisms and their respective
functions, the role of enzymes.
1) Enzyme catalysis relies on weak forces to hold reactants in
favorable positions to (usually) stabilize the transition state of the
reactants and so push the reaction forward. The 'shape' of the active site
brings atoms of the enzyme into positions where London forces and
hydrogen bonds stabilize the favorable configuration for reactions.
2) Protein structures are maintained by hydrogen bonding, London
forces, ionic interactions and hydrophobic interactions.
1º structure – peptide bonds
2º structure - H bonds
3ª structure - disulphide bridges/bonds; hydrophobic interactions ~
London dispersion forces; ionic/electrostatic interactions
3) DNA strands are held together chiefly by hydrogen bonds and
hydrophobic interactions (base stacking). The bases in the DNA are apolar
(even though having a N) and can be divided into PURINES (adenine +
guanine) and PYRIMIDINE (thymine + cytosine). Hydrogen bonding is also
the chief mechanism of selecting the correct nucleotide in DNA replication
and transcription.
4) RNAs have folded secondary structures that are maintained by
hydrogen bonds and hydrophobic interactions (base stacking). This is
important in all classes of RNA (mRNAs have stability and other motifs,
tRNAs rely on their folded structure, rRNAs rely on weak forces for their
structures and catalytic activities).
5) Lipid bi-layer membranes are held together chiefly by
hydrophobic interactions between the aliphatic tails. The polar heads
provide hydrogen bond potential to allow interaction with surrounding
molecules.
6) Immune recognition is mediated by weak forces (ionic,
hydrophobic and hydrogen bonds) between proteins and carbohydrates.
GENERALLY IONIC BONDS ARE THE STRONGEST ONES!
,Functions of the Four Major Groups of Organic Molecules
Group Examples Functions
Carbohydrate Glucose 1. Short term energy source
“Sugars” Glycogen 2. Transport form in animal - long
term energy storage
Lipids Fats and oils 1. Components of membranes
“Esters” Carboxylic Acid + (phospholipids)
Alcohol 2. Long term energy storage
3. Insolation
Proteins Enzymes Organic catalysts and
Sucrase Digestive enzymes
Lactase Structural protein in hair
Keratin Structural protein in skin
Collagen
Nucleic acids DNA 1. Information molecule
RNA 2. Molecule of heredity
ATP 3. Director of metabolism
involved in protein synthesis
immediate source of energy for
cellular work
Enzymes
Are highly specific, catalyst structures that bring down the
ACTIVATION ENERGY necessary for a reaction to occur, making them occur
faster. They are mainly proteic though some can be made of RNA
(ribozymes), and they have both tertiary and quaternary structure that
must be preserved so it can function.
They have active sites that bind to the substract, in what is called
induced-fit model. Enzymes can only work in certain conditions, mainly
related to temperature and pH range. They can be "defeat" by 4 types of
inhibitors: competitive ones (a molecule blocks the active site so the
substrate has to compete with the inhibitor to attach to the enzyme), non
competitive inhibitors (a molecule binds to an enzyme somewhere other
, than the active site and reduces how effectively it works), uncompetitive
(it only attaches to the complex enzyme + substract, causing the Vm and
Km to decrease), irreversible inhibitors (binds to an enzyme and
permanently inactivates it).
An enzyme can also become saturated if all the available active sites
have been occupied, we say therefore it has reached it's maximum
reaction velocity. One of the important constants related to this
occurence is the "Km", which corresponds to half of the substrate
concentration at which the reaction is half of the maximum velocity.
• A small Km indicates that the enzyme requires only a small amount
of substrate to become saturated. Hence, the maximum velocity is
reached at relatively low substrate concentrations.
• A large Km indicates the need for high substrate concentrations to
achieve maximum reaction velocity.
• The substrate with the lowest Km upon which the enzyme acts as a
catalyst is frequently assumed to be enzyme's natural substrate,
though this is not true for all enzymes.
The cell as the basis of life.
All the basic functions of life:
• Movement
• Reproduction
• Sensitivity
• Growth
• Reproduction
• Excretion
• Nutrition
