life at the cellular level (2) - molecules Flashcards
which elements is 99% of our body made up of
Hydrogen (H)
Oxygen (O)
Nitrogen (N)
Carbon (C)
where do H,O,N,C lie on the periodic table and what does that mean
they lie early in the periodic table meaning they are relatively light atoms
generally speaking, light atoms form the strongest bonds
how many bonds do H,O,N,C make
1,2,3,4 respectively
which of the four atoms (H,O,N,C) is the most versatile
carbon
what is a molecule
two or more elements bonded together
what does the bonding versatility of C explain
why it forms the basis of almost all biomolecules
why is C particularly versatile
it can form stable: single bonds (with H) single and double bonds (with O and N) single, double and sometimes triple binds with other C atoms
what does the variety of C’s bonding capability underlie
the evolution of all the different combinations of H,O,N, and C into biological molecules
what defines biomolecular functions
functional groups
what are functional groups
groups of elements (e.g. -OH) bonded to C
name 3 important functional groups
hydroxyl groups
aldehyde groups
keto groups
what is critical in determining functionality
the polarity in a molecule
what is polarity
distribution of electrons
give examples of stable bonds
C-C and C-H bonds are relatively stable as they share e-‘s equally
give examples of highly polar bonds
C-O and C-N or C-functional group bonds are highly polar, which alters the bond reactivity
what does the function of biomolecules depend on
the configuration of groups on the molecule
what does configuration mean
the fixed arrangement of atoms in a molecule
lots of biomolecules contains a double bond between carbon atoms (C=C), what is this called
a rigid conformation
what are the two distinct configurations
trans and cis
how can you interconvert between the two configurations
by breaking and re-forming bonds
give an example of when configuration can be important biologically
Rhodopsin is a protein embedded in the (rods of the) retina of the eye. On exposure to light the configuration of rhodopsin alters and this alteration stimulates nerves cells in the optic nerve to send messages to the brain where we “see”.
what can carbon mades molecules be
symmetrical (achiral)
asymmetric (chiral)
what are the 2 forms of asymmetric (chiral) carbon molecules
L- (Laevo)
D- (Dectro)
each exert different biological effects
what are all proteins made from
L-amino acids only
what does conformation mean
the precise arrangement of atoms in a molecule
what are the 5 chemical reactions of life
- redox reactions
- making and breaking C-C bonds
- internal rearrangements
- group transfers
- condensation and hydrolysis reactions
what happens in many biological reactions
two e-‘s (and two protons) are gained or lost
what is often transferred from one molecule to another
2 hydrogen atoms (protons) are transferred in dehydrogenation reactions
what does oil rig mean in redox reactions
oxidation is loss (of electrons)
reduction is gain (ofelectrons)
what is a reducing agent
it becomes oxidised itself as it reduces another compount
what is an oxidation agent
it becomes reduced itself as it oxidises another compound
why are NAD+ and NADH very important agents
they allow biochemical reactions to take place in cells
what type of agent is NADH
a reducing agent
what type of agent is NAD+
an oxidising agent
give an example of making/breaking C-C bonds
cleavage of glucose in the glycolysis pathway
give an example of internal rearrangements
in glycolysis, a rearrangement of the conformation of G6P occurs before the sugar is split
give an example of group teransfers
in glycolysis, in an enzyme catalysed reaction, a phosphoryl group (PO32-) is transferred from ATP to F6P
ATP provides energy for cellular reactions
what is a condensation reaction
occurs where two smaller molecules combine to form a larger molecule and in doing so release water (or other small molecules e.g. methanol)
what is a hydrolysis reaction
involve adding water to a molecule, and most commonly simultaneously breaking down a large molecule into smaller units
what is joined by condensation and broken by hydrolysis reactions
the sub-units of protein, polysaccharides and nucleic acids
what reactions are condensation and hydrolysis reactions important in
carbohydrate metabolism
what are complex carbohydrates composed of
Complex carbohydrates (polysaccharides) such as starch or glycogen are composed of many individual monosaccharide molecules e.g. glucose. A disaccharide e.g. sucrose, is simply two monosaccharides joined together.
give examples of glucose polymers
glycogen
starch
how are glucose polymers formed
by condensation reactions between two glucose monomers
how are the glucose monomers in glycogen and starch linked together
one glucose monomer is liked to another which locks the additional glucose in a cyclic form
how are lots of monomers liked together
all monomers of the chain are locked in the cyclic form except the end monomer, which can remain linear
this end monomer then forms a ‘reducing end’
give an example of a reduced sugar
D-glucose
what functional group does the linear form of D-glucose have attached
an aldehyde group which can be oxidised
If this is oxidised then the other reactant would be reduced, so glucose is termed a ‘reducing sugar’
what is the difference between proteins and polypeptided
Proteins are (sometimes multiple) long chains of amino acids. Polypeptides on the other hand are shorter (but not necessarily short!) chains of amino acids.
what do nucleic acids form
the core structure of DNA and RNA
what are nucleic acids
polymers of nucleotide monomers linked by 3’,5’-phosphodiester bonds
what makes up a nucleotide monomer
a bade
a sugar molecule
a phosphate group
what are the 2 kinds of base in nucleic acids
pyrimidines
purines
what are pyrimidines
cytosine (C)
thymine (T) (DNA only)
uracil (U) (RNA only)
what are purines
adenine (A)
guanine (G)
what is RNA made from
“normal” ribose sugars
what is DNA made from
deoxyribose sugars, which lack an oxygen atom
what is DNA
a double stranded nucleic acid. In other words, it is two independent chains of nucleic acids, linked together by their bases, which wrap around themselves to form the characteristic double helix of DNA
what is RNA
a single stranded nucleic acidAlthough it can wrap itself up in such a way that double stranded sections may form.
how does base pairing occur in DNA and RNA
a pyrimidine always pairs with a purine
how does base pairing occur in DNA
purines - pyrimidines
adenine - thymine
guanine - cytosine
how does base pairing occur in RNA
purines - pyrimidines
adenine - uracil
guanine - cytosine
how are fatty acids formed
long chains of carbon and hydrogen atoms
what type of bonds can be within the fatty acid between the carbon atoms
single or double
what does it mean if the fatty acid is saturated
all of the bonds in the fatty acid are single
what does it mean if the fatty acid is mono-unsaturated
there is one double bond in the fatty acid
what does it mean if the fatty acid id polyunsaturated
there are more than one double bond in the fatty acid
what happens to a fatty acid molecule the more double bonds present
it becomes more “bendy”
what effect does desaturation have on the fluidity of the fatty acid
The more unsaturated the fatty acid (the more double bonds in the chain) the more fluid the fatty acid.
This has important implications for cell membranes, which are largely composed of fatty acids, and health generally.
what are lipids
a family of molecules made up of fatty acids
what are the 3 classes of lipids
triacylglycerides
phospholipids
sterols
what are triacylglycerides
they are also called triglycerides
storage lipids
non-polar
3 fatty acid chains lined to glycerol
what are phospholipids
Similar to triacylglycerides,
But they have only two fatty acids chains and a phosphate group attached to the ‘head’ of these chains
This makes them polar
They form biological cell membranes – very important!
what are sterols
Produced in plants, animals and some micro-organisms
Most important one in humans is cholesterol
-Another essential component of cell membranes
-Precursor to steroid hormones and fat soluble vitamins (A, D, E)