Biological Molecules Flashcards
What is gen formula of carbs?
C6H12O6
What is the function of glucose?
Energy source
What is the function of glycogen?
Energy storage
What is glycosylation?
Sugars added to cell surface proteins - important aspect of the structure as they can differ as diff gly species attached to diff mol
What is the name of a sugar with 3 Cs and 2 e.gs?
Triose - e.g. glyceraldehyde, dihydroxyacetone
What is name of sugar with 5 Cs and e.g?
Pentose - ribose (in DNA + RNA)
What is name of sugar with 6 Cs and 2 e.g.s?
Hexose - e.g. glucose, fructose
What are aldoses and e.g?
Carbs containing aldose group e.g glucose
What are ketoses and e.g?
Carbs containing ketone group e.g. fructose
In terms of optical isomers, which sugars do humans use?
D-sugars
Which is C1?
carbon at the end closest to the carbonyl group
What % of hexoses are in linear form?
1%
What is the anomeric C?
Carbon attached to the original carbonyl group in cyclic form
What is the alpha form of glucose?
–OH group on the anomeric carbon in the down position
What is the beta form of glucose?
–OH group on the anomeric carbon in the up pos
Why are alpha/beta forms important?
glycosidic bond formation between sugars
What are alpha/beta forms like in solution?
α and β forms are in equilibrium and interconvert
What is a disaccharide and 3.e.gs?
2 monosaccharides joined together
e.g. sucrose (glucose + fructose)
– maltose (glucose + glucose)
– lactose (galactose + glucose)
What is a polysaccharide and 2 e.g.s?
Many mono
glycogen (branched chain glucose polymer)
– amylose (linear glucose polymer)
What is the structure of glycogen?
Linear glucose polymer α(1,4) with α(1,6) branches
What is the process of glycogen digestion?
1 glucose removed from 1 end + enz act on ends
Salivary α-amylase random hydrolysis of internal α(1,4) linkages
– Continues by pancreatic α-amylase mixture of mono- and disaccharides
– Finally maltase produces glucose be absorbed by the intestinal mucosal cells
What does Mobilisation of glycogen in liver involve?
Glycogen phosphorylase hydrolyses terminal α(1,4) to produce glucose-1-phosphate
What is lactose intolerance and what is it caused by?
can’t metabolise lactose correctly
• Normally in small intestine lactase (β-galactosidase) lactose → galactose and glucose
Red activity of b-galactosidase
• undigested lactose can then be digested by bacteria in large intestine producing excess carbon dioxide and other metabolites that cause bloating, diarrhoea etc
What are nucleic acids?
Polymers of nucleotides
What are the functions of nucleic acids?
Storage of genetic information - DNA
– Conversion of genetic information into proteins -ribonucleic acid RNA
What does DNA and RNA stand for?
DNA - deoxyribonucleic acid
RNA - ribonucleic acid
What is the structure of a nucleotide?
Pentose sugar
– Phosphate group
– Nitrogenous base
What are the DNA bases?
Adenine, thymine, cytosine, guanine
What are the RNA bases?
Adenine, thymine, cytosine, uracil
Describe DNA structure
Long polymer of nucleotides - 2 strands
• Backbone of alternating sugar and phosphate molecules
• Complementary second strand (A:T, C:G) , hydrogen bonds between bases
• Forms helical structure
• Bases extend inwards
What are the 3 classes of RNA?
Messenger, ribosomal, transfer
What is mRNA?
copy of gene, template for protein synthesis
What is rRNA?
structural component of the ribosome (protein synthesis machinery)
What is tRNA?
transport molecule for amino acids,
ensure sequence of proteins encoded in mRNA is decoded
What is transcription?
mRNA synthesis
What is translation?
Synthesis of protein based on encoded information on mRNA
Compare the size and structure of RNA to DNA
RNA is smaller than DNA
RNA is single stranded whereas DNA is double stranded
What is the function of ATP?
major energy molecule in cells
How does ATP release energy?
Bonds between phosphates are high-energy and when broken ⇒ energy
What is carbohydrate?
Large mol made from mono
What is a structural function of carbs?
part of cell wall in bacteria
Why is glycosylation an important aspect of structure?
as diff gly species attach to diff mol
What are 2 properties of carbs?
Water sol
Hydrophilic, polar
What is an e.g. of a mono and what is its function?
Glucose - energy source - broken down to smaller mol in series of reactions releasing energy cell can use to do work
also fructose + galactose
What is a glycosidic bond?
Covalent bond between -OH group of 1 sugar + -OH group of next b y cond reaction
What is condensation reaction?
H2O mol expelled
What enz involved in formation + breakdown of gly bond?
Glycosyltransferase
Why can’t glycosyltransferase not work for B 1,4 link/B glucoses?
Humans don’t have enz for formation/breakdown of cellulose
How are glycosidic bonds broken?
By hydrolysis
What is hydrolysis?
Water mol consumed
What is a reducing sugar?
If anomeric C not attached to another mol
Why is glycogen branched?
Each mono has sev free -OH groups that can form link to another mol/comp - branched - many ends of mol for enz to act - linear mol has just 1 end but many in branched - rapid breakdown of gly
ATP hydrolysis equation
ATP —> ADP + energy
ATP phosphorylation equation
ADP + Pi + energy —-> ATP
What is phosphorylation?
Transfer of phosphate group to mol
Which phosphate group is usually hydrolysed in ATP?
Last phosphate despite energy between phosphate groups being same - where enz evolved
Why ATP and not e.g. TTP?
Enz only recognise ATP
What types of reaction coupled with ATP hydrolysis?
Unenergetically favourable reactions through which other mol syn - transfer if terminal phos in ATP to another mol
Sol of triacyglycerols?
Water-insoluble (hydrophobic) but sol in fat + org sol
What is triacyglycerol?
Ester of 3 FA + glycerol
What is function of triacylglycerols?
Energy storage but compared to where some O2 associated partially ox - less energy gen whereas FA has little O2 - more energy released in ox
Where are triacylglycerols stored?
Adipose tissue
What are fatty acids?
Long chain aliphatic carboxylic acids
What is structure of fatty acids?
Long hydroC chain - hydrophobic + COOH group behaves as acid
Properties of FA?
Hydrophilic
Ionised in aq sol
Function of FA?
Met via B-ox pathway to gen ATP
What is sat FA + e.g. + 2 e.g.s with shorthand?
no C=C e.g. palmitic acid C16:0, stearic acid C18:0
What is unsat FA + e.g. + shorthand?
1/more C=C e.g. oleic acid C18:1
What is a property of unsat FA?
C=C create kinks in hydroC tails interfering with ability to pack together
What is polyunsat FA (PUFA) + e.g. + shorthand?
More than 1 C=C e.g. linoleic acid C18:2 (9,12)
What does each bit of shorthand for FA mean?
no. after C = no. of Cs
no. after : = no. of C=C
no. in brackets = location of C=C
What is structure of phospholipid?
Glycerol + 2FA andphosphate containing
group
What is function of phospholipids?
2 hydrophob FA tails + hydrophilic phos-containing head - diff phys + chem properties to triacy - tightness of packing affects fluidity of mem
Form bilayer in aq env - hyrdophil tails face air + hydrophob heads in H2O
What is structure of glycolipids?
Glycerol + 2FA and sugars
What is amphipathic?
mol with both hydrob + hydrophil regions - polar head group + non-polar tail
What is structure of steroids?
Common multi-ring structure
What is cholesterol?
Small hydrophob mol with sterol backbone
Where do u get cholesterol from?
diet and de novo synthesis = syn of complex mol from simple mol e.g. sugars/aa as opposed to recycling after partial degradation
Statins also involved in syn of chol
What is role of cholesterol?
In membrane fluidity - mol short + rigid - fill spaces between neighbouring phospholipid mol left by kinks in unsat hydroC tails - stiffen bilayer - less flexible + permeable
Precursor of steroid hormones e.g. testosterone, oestrogen, cortisol
What is structure of aa monomer?
COOH + NH2 group both linked to a-C
Side chain attached to a-C
all exist as L-forms in proteins
What are 2 properties of aa?
H2O sol
electrically charged at phys pH
How many universal aa are there?
20
What is a protein?
Long sequences of aa linked by peptide bond in chain that folds to form 3D structure - big polypeptide
What is a dipeptide?
2 aa joined togther by peptide bond
What is a polypeptide?
Chain of many aa joined by peptide bonds
What is a peptide?
Small protein
What do ‘essential aa’ mean?
Can’t be syn de novo by humans - lack nec enz
What are 9 essential aa?
Thr, met, lys, val, leu, ile, his, phe, trp
What is 3 letter code for: asparagine, glutamine, isoleucine and tryptophan
Asp, gln, ile, trp
What is single letter code for: asp glu lys, asn gln tyr trp ,
D E K N Q Y W
Which aa have COOH side chain?
asp, glu
Which aa have NH2 side chain?
arg, lys
At phys pH, which aa side chains are -ve, polar/hydrophilic?
Asp, glu
At phys pH, which aa side chains are +ve, polar/hydrophilic?
Arg, lys, his
At phys pH, which aa side chains are uncharged, polar/hydrophilic?
Asn, gln, ser, thr, tyr
At phys pH, which aa side chains are non-polar/hydrophoic?
Ala, gly, val, leu, ile, pro, phe, met, trp, cys
Which aa have ketone side chain?
Asp, gln
Which aa have OH side chain?
Ser, thr
Which aa have aromatic side chain?
Tyr, phe, trp, pro, his
Which aa have aliphatic side chain?
Gly, ala, val, leu, ile
Which aa have sulphur side chain?
Met, cys
What are some other roles of glu, gln, tyr, his, trp
Glu - MSG taste enhancement Gln - neurotransmitters Try - syn of epinephrine, dopamine His - syn of histamine Trp - syn of serotonin
What is N-terminus?
Amino group end of polypeptide
What is C-terminus?
Carboxyl group at other end of polypeptide?
What is hydrolysis of peptide bond by?
Enz in digestion/lysosome
What type of reaction is peptide bond formed and by what?
Cond reaction by enz
What is pKa?
Measure of ease with which side groups in aa give their protons
What happens to aa at phys pH?
COOH and NH2 groups attached to a-C fully ionised
What is the pka of a-COOH group in aa?
2.3
What is the pka of a- NH2 group in aa?
9.8
Which pka is relevant in polypeptides?
R groups not the a groups as they’re pare of peptide bond and so have influence on structure + function of proteins
Which 5 aa side chains form ions in sol and carry charge?
Asp, glu, his, lys
Which aa can change during bio pH?
His
What is pk of asp and what happens to COOH r group above and below it?
4.7
above 4.7: COO-
below 4.7: COOH
What is pk of glu and what happens to COOH r group above and below it?
4.7
above 4.7: COO-
below 4.7: COOH
What is pk of his and what happens to COOH r group above and below it?
6.5
above 6.5: N
below: NH+
What is pk of lys and what happens to COOH r group above and below it?
10.2
above 10.2: NH2
below 10.2: NH3+
