intro to biomolecules 2 Flashcards
what are nucleic acids
- important class of macromolecules
- essential to all forms of life
- found on all types of cells
what does the term nucleic acid relate to overall
- DNA and RNA (biopolymers composed of nucleotides)
what is a nucleotide made up of
- nitrogenous base (A,T,G,C,U)
- pentose sugar (ribose or deoxyribose)
- phosphate group
what is a nitrogenous base and why is it named “base”
- organic molecule
- contains nitrogen
- acts as a base in chemical reactions
- provides the “basic” property of a nucleotide (its basicity driven from the nitrogen atom)
- energy carriers in biochemical reactions
what are the 2 classes of nitrogenous bases
purines (double ring = A,T)
pyramidines (single ring = C,T,U)
what nitrogen is used to link the bases to sugar in a glycosidic bond
purines = N9
pyrimidines = N1
what is the name of RNA when the hydroxy group points in same direction as anomeric carbon
Ribose (beta-D-ribofuranose)
how are carbons numbered in the pentose sugar
- anomeric carbon (1) on side where beta group is
- number with a prime (ie 5’)
what is the difference between ribose and deoxyribose
deoxy = H on the 2’ carbon instead of OH
what are nucleosides
structure formed by link of a nitrogenous base with a carbohydrate (typically a ribose or deoxyribose) at carbon 1’
which bond couples a nitrogenous base to D-ribose or 2’-deoxy-D-ribose and what does it form between
beta-N-glycosidic bond
- between anomeric carbon 1’ of sugar and N9 of base
what nucleosides are found in rna and dna
cytidine uridine adenosine guanosine - ADD deoxy to the front for dna and deoxythymidine instead of uracil
how does a nucleoside make a a nucleotide
link to 1+ phosphate group
nucleoTide = phosphorylated form of nucleoSide
what is the most common site of phosphorylation
hydroxyl group attached to 5’ carbon of ribose
how can we identify the state of phospohrylation (number of phosphate groups)
monophosphate = dNMP di = dNDP tri = dNTP
ie - mono of adenosine is (AMP)
tri is ATP
mono of deoxyadenosine is dAMP
what are the major functions of nucleotides / nucleosides
- important metabolites
- form basic structural unit of nucleic acids
- participants in energy transfer reactions (predominantly carried out by ATP)
- encode, transmit express genetic info in living things
- role in intermediary metabolism and biosynthesis of macromolecules
- involved in cell signalling
how are nucleotides / nucleosides important in medicine
- antiviral + anticancer agents
- some show high degree of potency + selectivity against herpes group of viruses
what functions do proteins have
- catalysts
- transport (haemoglobin)
- communication (hormones)
- cell structure (actin cytoskeleton)
- give cells mobility (flagella)
- body immunity
what do proteins exist of and how many of these exist
- sub-units called amino acids
- 20 types exist in the human body
- so all proteins built from this selection of 20
what is the basic structure of amino acids
- chiral carbon = the alpha carbon (in centre)
- carboxyl group (COOH)
- amine group (NH2)
- Hydrogen
the only part that differs: - R group = side chain, variable, provides each amino acids characteristic properties
what is the significance of the amino acid glycine
- its R group is just a H atom
- so alpha carbon is NOT chiral (2 H groups)
what is the consequence of amino acids (except glycine) being chiral
- exist in 2 mirror images
- forms L and D
- every amino acid in cells and proteins is in the L configuration (only a few exceptions)
what is the common approach to classifying amino acids
according to whether functional group on R side chain at neutral pH is 1) non-polar
2) polar but uncharged
3) polar but positively charged
4) polar negatively charged
what property do non-polar amino acids have
hydrophobic
what property do polar uncharged amino acids have
R groups soluble in water and hydrophilic
so seek contact with aqueous solutions
because their functional group forms H bond w water
what property do positively charged amino acids have
r group basic
what property do negatively charged amino acids have
r group acidic
so why does a slight change of amino acids exerts a profound effect on the structure + biological activity of proteins
each has unique characteristics arising from - size - shape - solubility - ionisation property of R group
what does a peptide bond form between and what is formed
- carboxyl group of one amino acid and amine group of another
- makes H2O
- forms polypeptides and ultimately proteins
what physical property do lipids have so how is an organic compound classed as a lipid
solubility
- if they are more soluble in organic solvents than in water
what is included in the lipid category
- fats (fatty acids)
- triglycerides
- oils
- steroids
define lipids
molecules that are insoluble in aqueous solutions + soluble in organic solvents
how do lipids contrast to proteins, nucleic acids and polysaccharides
NOT large macromolecular polymers
what major groups are lipids classified into
1) fatty acids + its derivatives
2) cholesterol + its derivatives
3) lipoproteins
how are lipids formed
chemical linking of several small constituent molecules
where do fatty acids occur
- rarely as free molecules in nature
- usually as component of complex lipid molecules
1) fats (energy storage compound)
2) phospholipids (primary lipid component of cellular membrane)
what are biological fatty acids composed of
- hydrocarbon chain
- 1 terminal carboxyl group / moiety
- SO members of carboxylic acid class
what are the 2 types of fatty acid
saturated = no double bonds, commonly between 12+24 carbons long unsaturated = 1+ carbon-carbon double bond
which short chain saturated fatty acids are biochemically important
butyric acids (contain 4 carbon) caproic acids (contain 6 carbons) both in milk
how do we number fatty acid carbons
1 = carbon of the carboxyl (COOH) group (most reactive component)
what properties do saturated fatty acids have
1) V stable - not prone to rancidity
2) straight chains stack tight
3) solid at room temp
4) in butter, animal fats, eggs, coconut oil, palm oil + BODY
how can we determine number of double bonds in an unsaturated fatty acid
1) monounsaturated = one double bond
2) polyunsaturated = 2+ double bonds
what configurations can the double bond of unsaturated fatty acid exist in
- CIS (2 H atoms on carbons of double bond stick out on same side of chain)
- TRANS (2 H atoms stick out on opposite side of chain)
what is the structural difference between cis and trans-fatty acids
cis
- causes chain to bend
- restricts conformational freedom
- more double bonds in the chain = less flexibility it has
trans
- doesn’t cause the chain to bend much
- shape is similar to straight saturated fatty acids
which of cis or trans fatty acids are more common
CIS
in ALL biological unsaturated fatty acids
what properties do unsaturated fatty acids have
- double bonds prone to rancidity
- double bonds cause bent chains which do not stack as tightly as saturated
- liquid at room temp
- in plant oils
what are numerical symbols used to describe fatty acid chains
ratios
1st number - no of carbons in fatty acid chain
2nd = no of double bonds in chain
small numbers (to power of with delta symbol then a number) = position of the start of each double bond counting from carbon 1
what is linolenic acids numerical symbol
- 18 carbon
- 3 double bonds starting at positions 9, 12, 15
18:3^delta9,12,15
what is an essential fatty acid
important animals cannot synthesise them so obtain them in the diet from plant source ie linoleic acid linolenic acid
what are
a) myristic acid
b) palmitic acid
c) arachidonic acid
a) attached to N-term of plasma membrane associated cytoplasmic proteins
b) end product of mammalian fatty acid synthesis
c) precursor for eicosanoid synthesis
what are triglycerides
- energy storage compound in form of fat droplets composed of triglycerides in specialised fat cells (adipose cells)
- major components of stored fat (storing fatty acids in biological systems)
what are phospholipids
primary lipid component of cellular membrane
what is the structure of a triglyceride / triaglycerol
- large triester molecule
- derived from glycerol combined with 3 fatty acid molecules
- each of 3 fatty acid molecules undergoes an esterification with 1 of the hydroxy groups of the glycerol molecule
- forms 3H2O
what is glycerol
a triol (alcohol that contains 3 hydroxy functional groups)
where do triacyclglycerols accumulate in mammals
cytoplasm of adipose cells
what do fatty acids provide when stored as energy
thermal insultion
- fat deposits under skin + throughout body cut heat loss by 2/3
protection against mechanical comparation
why is triglycerides the preferrd form of energy storage over glucose
produce approximately 6x the amnt of usable energy
why are triglycerides good in the body
efficient long term energy storage
large molecules so high potential energy
gram for gram MORE THAN 2x energy of carbs
what are glycerophospholipids
- similar basic structure to triglycerides
- carbon 3 of glycerol backbone = esterified to a phosphoric acid
what is the building block of phospholipids
a phosphatidic acid
how do phospholipids form the cell membrane
ampithatic / amphiphilic = have hydrophilic (head - contains -vely charged phosphate group, miscible w + attracted to water) and hydrophobic (non-polar tail - interact w other none polar molecules turns away from water ) regions SO when added to water self-assemble into a bilayer with hydrophobic tails pointing towards interior
what are the most important and abundant phospholipids in all mammalian cells
phosphatidylcholine (PC)
phosphatidylethanolamine (PE)
phosphatidylserine (PS)
phosphatidylinositol (PI)
how are steroids defined
- class of lipids
- defined by chemical structure - carbon skeleton consisting of 4 fused rings (3 six sided, 1 five sided)
why do steroids vary in nature
- different groups have functional group attached
- vary in nature of attached group and position of the groups
a steroid is any…
class of natural or synthetic compounds characterised by molecular structure derived from the 4 fused rings
give 3 examples of steroids
cholesterol
estradiol
testosterone
what does the steroid group include
1) sex hormones
2) adrenal cortical hormones
3) bile acids
4) sterols of vertebrate
5) other physiologically active substances of animals + plants
what synthetic steroids are of therapeutic value
large number of
1) anti-inflam agents
2) anabolic agents (growth stimulating)
3) oral contraceptives
cholesterol is the precursor for the synthesis of what
1) vitamin D
2) testosterone
3) estrogen
4) progesterone
5) aldosterone
6) cortisol
7) bile salts
what role does cholesterol have
in membrane structure
how is over accumulation and abnormal deposition of cholesterol prevented
its synthesis + utilisation must be tightly regulated
why is abnormal deposition of cholesterol and cholesterol-rich lipoproteins in coronary arteries clinically important
lead to atherosclerosis
which vitamins are derived from steroids
ergosterol
vitamin D
what are the 4 steroid hormones
- pregnenolone
- progesterone
- estradiol
- testosterone
what is pregnenolone
- produced directly from cholesterol
- precursor molecule for all C18, C19, C21 steroids
what is progesterone
- produced directly from pregnenolone
- secreted from the corpus luteum
- responsible for changes associated w luteral phase of menstrual cycle
what is estradiol
- estrogen principal female sex hormone
- produced in ovary
- responsible for female sex characteristics
what is testosterone
- androgen
- synthesized in testes
- responsible for secondary male sex characteristics
