what is a molecule made up of
elements
what are elements
cannot be broken down or converted into other substances by chemical means
what is a chemical element
consists of one type of atom
what is an atom
the smallest particle of an element that still retains the elements distinctive chemical properties
what charge is a proton
positive
what charge is an electron
negative
what does the atomic number equal
number of protons
what does the number of protons equal
atomic number and the number of electrons
what does the number of electron equal
the number of protons
what charge is neutrons
neutral
electrons fill the shells from the ________ to the _____ shell
innermost, outer
most atoms have ___________ outer most electron shells making it reactive
unfilled
what is a covalent bond
sharing of electrons
what rotation is there about a single covalent bond
full
what rotation is there about a double covalent bond
restricted
what are the non covalent interactions
hydrogen bonds, ionic interactions, van der waals attractions and hydrophobic forces
what is the biological relevance of non covalent interactions
mediates molecular interactions and stabilises macromolecule structures
what are polar covalent bonds
unequal sharing of electrons belonging to a bond between two atoms
how is a polar covalent bond formed
causes if one atom has a higher electronegativity to electrons than other atoms such as hydrogen and oxygen in water
what are hydrogen bonds
polar covalent bonds create attraction (dipole) which can tract other polarised molecules.
how do hydrogen bonds form
is the polarised molecular contains a hydrogen atom and this hydrogen atom is between two electron attracting atoms
what is the strength of a hydrogen compared to a covalent bond
1/20th the strength of a covalent bond
when is a hydrogen bond the strongest
when 3 atoms are in a straight line
what are ionic interactions
electrons lost or gained by atoms –> electrically charged ions. opposite attractions hold each other together.
how are ionic interactions in water
weak because the charges are shielded by water
how are ionic interactions without water
strong
what are van der waals attractions
weak interactions due to fluctuating electrical charges between atoms, effective when atoms move close together
what are hydrophobic forces
hydrophobic molecules forced together due to repulsion by water molecules such as oil and water
what are macromolecules
most abundant compound inside cells after water
in biology, what are some macromolecules
nucleic acids (DNA and RNA), proteins, polysaccharides, lipids-phospholipids. most are polymers
what is the building block of macromolecules
carbon and the stable rings and chains it can form
what can carbon chains and rings be building blocks for
macromolecules, energy source or both
what are carbohydrates
hydrates of carbon (CH2O)n where n is typically 3,4,5,6
what is the basic form of carbohydrates
monosaccharides
what is glucose
C6H121O6, monosaccharide with 6 carbon ring and structure includes 5 carbons and one oxygen
what are polysaccharides
composed of sugar subunit or monosaccharides
what is an example of a disaccharide
sucrose which is glucose and fructose
what is an oligosaccharide
3-50 monosacchrides
what is a polysaccharide
100s to 1000s subunits
how can we form di and polysaccharides
condensation reactions
what are condensation reactions
leads to generation of water molecule as covalent bond forms between subunits
what is a hydrolysis reaction
addition of a water molecule cleaves bond linking two subunits
what are hydrolysis and condensation reactions catalysed by
enzymes and commonly found in the formation or cleavage of macromolecules
what are the two forms of glucose molecules (and other monosaccharides)
alpha and beta
what does alpha and beta formations of a monosaccharide mean
the hydroxyl group on the carbon atom that carries the aldehyde or ketone can rapidly change from one position to the other. the two positions are alpha and beta
what is alpha hydroxyl
the alcohol group is down
what is beta hydroxyl
the alcohol group is up
what happens when you link two monosaccharides
it freezes the alpha or beta form
where is cellulose found
walls of plant cells
what is the most organic molecule on earth
cellulose
what is cellulose made up of
repeating glucose units
where is chitin found
exoskeletons of arthropods and insects and cell wall of fungi
what is chitin
linear molecule of repeating units of the sugar derivative N-actylglucosamine in beta-1-4 linkage
what is common in chitin and cellulose
they both are made up of long chains of glucose subunits
what are some examples of lipids
fatty acids and derivatives, fats, oils, and phopholipids and steroids
describe the structure of fatty acid
have a hydrophobic tail and hydrophilic head. `
what does amphipathic mean
a molecule having hydrophilic and hydrophobic parts
describe the hydrophilic head of a fatty acid
carboxylic head, chemically reactive-nearly all covalently linked to other molecules
describe the hydrophobic head of a fatty acid
hydrocarbon tail- differ in length and position of double and single bond
what is an unsaturated fatty acid
double bond(s) linking carbon atoms in hydrophobic tail, can’t stack very well because of the double bond and the bend. therefore liquid at room temperature such as plant oils.
what is a saturated fatty acid
no double bonds, tight packing, solid at room temperature such as animal oils
describe energy reserve in cells as a role of fatty acids
provide 6 times as much usable energy as glucose (on a weight basis). It is stored as triacylglycerid molecules
what are phospholipids
two fatty acids linked to glycerol, 3rd site on glycerol linked to phosphate group and small hydrophilic group attached covalently to phosphate group making is strongly amphipathic
unsaturated tails _____ membrane fluidity
increase
saturated tails ____ fluidity
decrease
what are glycolipids
similar to phospholipids but sugar groups replace phosphate. Amphipathic nature retained
what is the role of glycolipids
cell-to-cell recognition
what are the two main types of steroids
membrane and non-membrane steroids
what are non-membrane steroids
signalling molecules, hormones like testosterone and estradiol, can pass through membrane
what is RNA
transcient carrier of information
what is DNA
long term storage of hereditary material
what is DNA and RNA composed of
nucleotides
what are nucleotides
nitrogenous base, five carbon sugars (pentose), phosphate group (one or more)
what are nitrogenous bases
contains nitrogen, made up of pyridines and purines
what are pyrimidines
single ring structure , cytosine, thymine and uracil
what are purines
double ring structure, adenine and guanine
what bases do DNA have
ACGT
what bases do RNA have
ACGU
what is a nucleoside
nitrogenous base and pentose
what is an example of a nucleoside
adenoside
what is more stable out of ribose and deoxyribose
deoxyribose because it doesn’t form an intermediate
what bonds connect phosphate groups
phosphoanhydride
what is conserved in a phosphoanhydride bond
high amounts of energy- cells use this as a source of energy
what charge does a phosphate group give to a nucleotide
negative charge
what charge are DNA and RNA
negatively charged
what are the different bases in DNA and RNA
DNA has guanine and Rna has guanine
what sugar does DNA have
2-deoxyribose
what sugar does RNA have
ribose
how are nucleotides joined together
through condensation reactions
what bonds link adjacent nucleotides in nucleic acids
phosphodiester
true or false- the hydroxyl group on 3’ carbon of pentose is covalently linked to phosphate group attached to 5’ carbon of adjacent pentose
true - forming the sugar-phosphate backbone
what way by convention is the sequence of bases read in a nucleic acid strand
5’ to 3’ using single letter code
how are strands of DNA held together
by hydrogen bonds
what is the ratio to purines and pyrimidines
1:1
what are three other functions of nucleotides
carriers of chemical energy, combined with other groups as coenzymes and signalling molecules
how can nucleotides be used as chemical energy
phosphoanhydride bonds can be hydrolysed
how can nucleotides be used as signalling molecules
activate enzymes and turn on genes such as cyclic AMP which is the starving signaller for a cell
at what pH are the side chains of amino acids ionised
7
what are the different groups on an amino acid
amino group, carboxyl group and a side chain with the carbon in the middle known as the alpha-carbon.
Define antiparallel
Describes the relative orientation of the two strands in a DNA double helix or two paired regions of a polypeptide chain, the polarity of one strand is oriented in the opposite direction to that of the other