Covalent Bonding - atoms share a pair of electrons in their outer shell, outer shell of both atoms
filled so a more stable compound, called a molecule is formed.
Ionic Bonding- ions with opposite charges attract each other, electrostatic attraction is known as
ionic bond, ionic bonds weaker than covalent bonds.
Hydrogen Bonding- electrons within a molecule not evenly distributed and spend more time at 1
position which is more negatively charged than the rest of the molecule.
a molecule with uneven distribution of charge said to be polarised (polar molecule), negative
region of 1 polarised molecule and positively charged region of another attract each other,
forming weak electrostatic bonds.
Monomers are small units which are the components of larger molecules, examples include
monosaccharides such as glucose, amino acids and nucleotides. Polymers are molecules made
from many monomers chemically bonded together. Polythene and polyesters are industrially
produced while polysaccharides, polypeptides and polynucleotides made naturally by living
organisms.
- E.g subunit of polysaccharide is a monosaccharide/single sugar.
- Polypeptides formed by linking together peptides that have amino acids as their basic
sub unit
Monomers are joined by a chemical bond in a condensation reaction whereby a water molecule
is eliminated. This removal of water from monomers enables a chemical bond to form between
the monomers.Hydrolysis is the opposite of a condensation reaction and is when water is added
to break a chemical bond between two bonded monomers.
Mole: SI unit for measuring amount of substance
- 1 mole contains 6.022 x 10^23 carbon atoms (Avogardo’s constant)
Molar Solution: solution that contains one mole of solute in each litre of solution.
,Atomic Number- the number of protons in an atom
Mass Number- the total number of protons and neutrons in an atom.
If an atom loses/receives an electron, it becomes an ion.
Carbon atoms readily form bonds with other carbon atoms
- Allows sequence of carbon atoms of various lengths to be built up, forming a “backbone”
along which other atoms can be attached.
- Carbon containing molecules are known as organic molecules
Carbohydrates are molecules which consist only of carbon, hydrogen and oxygen and they are
long chains of sugar units called saccharides. A single monomer is called a monosaccharide
with a pair of monomers being called a disaccharide. Combining many monosaccharides results
in the formation of a polysaccharide. These are all joined together with a glycosidic bond formed
in a condensation reaction.
Monosaccharides
Glucose is a monosaccharide containing six carbon atoms in each molecule, and is the main
substrate for respiration and therefore of great importance. It has two isomers – alpha and beta
glucose with structures being seen on the right. Common monosaccharides include glucose,
galactose and fructose. These are typically sweet tasting, soluble substances which have the
general formula is CnH2nOn where n can have any number from three to seven.
,Disaccharides: Two monosaccharides can join together in a condensation reaction to form a
disaccharide. In this process a glycosidic bond is formed. The diagram below shows the
formation of a 1,4 glycosidic bond between two alpha glucose molecules in order to form a
molecule of maltose.
Examples of some common disaccharides and how they are formed are shown below: • Maltose
is a disaccharide formed by condensation of two glucose molecules.
• Sucrose is a disaccharide formed by condensation of glucose & fructose.
• Lactose is a disaccharide formed by condensation of glucose & galactose.
Polysaccharides
Polysaccharides are formed by combining together many monosaccharide molecules. •
Glycogen and starch which are both formed by the condensation of alpha glucose. • Cellulose
formed by the condensation of beta glucose.
Glycogen is the main energy storage molecule in animals and is formed from many molecules
of alpha glucose joined together by 1, 4 and 1, 6 glycosidic bonds. It has a large number of side
branches meaning that energy can be released quickly as enzymes can act simultaneously on
these branches. Moreover, it is a relatively large but compact molecule thus maximising the
amount of energy it can store. Finally being insoluble means it will not affect the water potential
of cells and cannot diffuse out of cells.
Starch stores energy in plants, formed by the joining of 200 & 100,000 alpha-glucose molecules
by glycosidic bonds in a series of condensation reactions, forms an important component of
food and is the major energy source in most diets and is a mixture of two polysaccharides called
amylose and amylopectin:
• Amylose – amylose is an unbranched chain of glucose molecules joined by 1, 4 glycosidic
bonds, and as a result amylose is coiled and thus a very compact molecule storing a lot of
energy.
• Amylopectin is branched and is made up of glucose molecules joined by 1, 4 and 1, 6
glycosidic bonds. Due to the presence of many side branches these can be acted upon
simultaneously by many enzymes and thus broken down to release its energy.
- Glucose monomers are released very rapidly used for respiration.
• Some key properties of starch that make it suitable are that;
its insoluble so will not affect cell water potential, water not drawn into cells by osmosis
- Large and insoluble, does not diffuse out of cells
, it is compact so a lot of energy can be stored in a small space
when it is hydrolysed the released alpha glucose can be transported easily and readily used for
respiration.
, - Never found in animal cells
GLYCOGEN
- Found in animals and bacteria, never in plant cells
- Similar in structure to starch but shorter chains, and more highly branched
- Stored as small granules mainly in muscles and liver
- Same properties as starch except more highly branched, so more ends acted on
simultaneously by enzymes.
- Important to animals who have higher metabolic and respiratory rate than plants as they
are more active.
Cellulose is a component of cells wells in plants and is composed of long, unbranched chains of
beta glucose which are joined by glycosidic bonds. Microfibrils are strong threads which are
made of long cellulose chains running parallel to one another that are joined together by
hydrogen bonds forming strong cross linkages, microfibrils are grouped to form fibres all of
which provides more strength.
Cellulose is important in stopping the cell wall from bursting under osmotic pressure. This is
because it exerts inward pressure that stops the influx of water. This means that cells stay turgid
and rigid, making non-woody parts of the plant semi-rigid, helping to maximise the surface area
of plants for photosynthesis.
Biochemical tests: • Benedict’s reagent can be used to test for the presence of reducing sugars.
All monosaccharides and some disaccharides (e.g. maltose) are reducing sugars. These are
therefore sugars that can donate an electron to the Benedict’s Reagent. Benedict’s reagent is a
filled so a more stable compound, called a molecule is formed.
Ionic Bonding- ions with opposite charges attract each other, electrostatic attraction is known as
ionic bond, ionic bonds weaker than covalent bonds.
Hydrogen Bonding- electrons within a molecule not evenly distributed and spend more time at 1
position which is more negatively charged than the rest of the molecule.
a molecule with uneven distribution of charge said to be polarised (polar molecule), negative
region of 1 polarised molecule and positively charged region of another attract each other,
forming weak electrostatic bonds.
Monomers are small units which are the components of larger molecules, examples include
monosaccharides such as glucose, amino acids and nucleotides. Polymers are molecules made
from many monomers chemically bonded together. Polythene and polyesters are industrially
produced while polysaccharides, polypeptides and polynucleotides made naturally by living
organisms.
- E.g subunit of polysaccharide is a monosaccharide/single sugar.
- Polypeptides formed by linking together peptides that have amino acids as their basic
sub unit
Monomers are joined by a chemical bond in a condensation reaction whereby a water molecule
is eliminated. This removal of water from monomers enables a chemical bond to form between
the monomers.Hydrolysis is the opposite of a condensation reaction and is when water is added
to break a chemical bond between two bonded monomers.
Mole: SI unit for measuring amount of substance
- 1 mole contains 6.022 x 10^23 carbon atoms (Avogardo’s constant)
Molar Solution: solution that contains one mole of solute in each litre of solution.
,Atomic Number- the number of protons in an atom
Mass Number- the total number of protons and neutrons in an atom.
If an atom loses/receives an electron, it becomes an ion.
Carbon atoms readily form bonds with other carbon atoms
- Allows sequence of carbon atoms of various lengths to be built up, forming a “backbone”
along which other atoms can be attached.
- Carbon containing molecules are known as organic molecules
Carbohydrates are molecules which consist only of carbon, hydrogen and oxygen and they are
long chains of sugar units called saccharides. A single monomer is called a monosaccharide
with a pair of monomers being called a disaccharide. Combining many monosaccharides results
in the formation of a polysaccharide. These are all joined together with a glycosidic bond formed
in a condensation reaction.
Monosaccharides
Glucose is a monosaccharide containing six carbon atoms in each molecule, and is the main
substrate for respiration and therefore of great importance. It has two isomers – alpha and beta
glucose with structures being seen on the right. Common monosaccharides include glucose,
galactose and fructose. These are typically sweet tasting, soluble substances which have the
general formula is CnH2nOn where n can have any number from three to seven.
,Disaccharides: Two monosaccharides can join together in a condensation reaction to form a
disaccharide. In this process a glycosidic bond is formed. The diagram below shows the
formation of a 1,4 glycosidic bond between two alpha glucose molecules in order to form a
molecule of maltose.
Examples of some common disaccharides and how they are formed are shown below: • Maltose
is a disaccharide formed by condensation of two glucose molecules.
• Sucrose is a disaccharide formed by condensation of glucose & fructose.
• Lactose is a disaccharide formed by condensation of glucose & galactose.
Polysaccharides
Polysaccharides are formed by combining together many monosaccharide molecules. •
Glycogen and starch which are both formed by the condensation of alpha glucose. • Cellulose
formed by the condensation of beta glucose.
Glycogen is the main energy storage molecule in animals and is formed from many molecules
of alpha glucose joined together by 1, 4 and 1, 6 glycosidic bonds. It has a large number of side
branches meaning that energy can be released quickly as enzymes can act simultaneously on
these branches. Moreover, it is a relatively large but compact molecule thus maximising the
amount of energy it can store. Finally being insoluble means it will not affect the water potential
of cells and cannot diffuse out of cells.
Starch stores energy in plants, formed by the joining of 200 & 100,000 alpha-glucose molecules
by glycosidic bonds in a series of condensation reactions, forms an important component of
food and is the major energy source in most diets and is a mixture of two polysaccharides called
amylose and amylopectin:
• Amylose – amylose is an unbranched chain of glucose molecules joined by 1, 4 glycosidic
bonds, and as a result amylose is coiled and thus a very compact molecule storing a lot of
energy.
• Amylopectin is branched and is made up of glucose molecules joined by 1, 4 and 1, 6
glycosidic bonds. Due to the presence of many side branches these can be acted upon
simultaneously by many enzymes and thus broken down to release its energy.
- Glucose monomers are released very rapidly used for respiration.
• Some key properties of starch that make it suitable are that;
its insoluble so will not affect cell water potential, water not drawn into cells by osmosis
- Large and insoluble, does not diffuse out of cells
, it is compact so a lot of energy can be stored in a small space
when it is hydrolysed the released alpha glucose can be transported easily and readily used for
respiration.
, - Never found in animal cells
GLYCOGEN
- Found in animals and bacteria, never in plant cells
- Similar in structure to starch but shorter chains, and more highly branched
- Stored as small granules mainly in muscles and liver
- Same properties as starch except more highly branched, so more ends acted on
simultaneously by enzymes.
- Important to animals who have higher metabolic and respiratory rate than plants as they
are more active.
Cellulose is a component of cells wells in plants and is composed of long, unbranched chains of
beta glucose which are joined by glycosidic bonds. Microfibrils are strong threads which are
made of long cellulose chains running parallel to one another that are joined together by
hydrogen bonds forming strong cross linkages, microfibrils are grouped to form fibres all of
which provides more strength.
Cellulose is important in stopping the cell wall from bursting under osmotic pressure. This is
because it exerts inward pressure that stops the influx of water. This means that cells stay turgid
and rigid, making non-woody parts of the plant semi-rigid, helping to maximise the surface area
of plants for photosynthesis.
Biochemical tests: • Benedict’s reagent can be used to test for the presence of reducing sugars.
All monosaccharides and some disaccharides (e.g. maltose) are reducing sugars. These are
therefore sugars that can donate an electron to the Benedict’s Reagent. Benedict’s reagent is a
