building blocks of bio Flashcards
water accounts of __% of a cell’s weight
70%
name the four building blocks of every cell
sugars
fatty acids
amino acids
nucleotides
polymers made from the four building blocks
sugars –> polysaccharides
fatty acids –> fats / lipids / membranes
amino acids –> proteins
nucleotides –> nucleic acids
basic structure of a nucleotide
N-containing base
5-C sugar
phosphate group(s)
name five types of N-containing bases
adenine
guanine
cytosine
thymine
uracil
how many rings do each of the N-containing bases have?
A and G = 2
T and C = 1
so that all base pairs have 3 rings in total
nucleoside vs nucleotide
nucleoside = sugar + base
nucleoTide = sugar + base + phosphaTe (eg. ATP, dAMP)
biological polymerisation is driven by___
ATP
w/ loss of H2O (condensation polymerisation)
general bonding in DNA
covalent - phosphate backbone
H-bonds between bases
DNA structure main features
double helix, major + minor groove
phosphate backbone = POLAR due to -vs charge on phosphate
planar bases
stacking of bases influences stability
how many H-bonds form between A-T and C-G?
A=T
C-G 3 bonds
RNA vs DNA nucleotides differences
additional hydroxyl group in ribose sugar of RNA (ribose, not deoxyribose)
Uracil rather than thymine
describe RNA secondary structure
does not form a double helix like DNA
moves in space until it finds the lowest energy folding combination
held together by H-bonds
general amino acid structure
NH2 amino group
COOH carboxyl group
R functional group (side chain) attached to alpha C chiral centre
at pH7, what happens to amino acids?
both amino and carboxyl groups ionised –> zwitterionic
formation / breaking of peptide bond
N and C terminus of two amino acids
condensation reaction –> peptide bond
hydrolysis reaction (+H2O) to break
describe the four levels of protein structure
primary = amino acid residues
secondary = local folding (determined by interactions between amino acids)
tertiary = global folding, combination of secondary structures –> polypeptide chain
quaternary = assembled subunits
describe the bonding in an alpha-helix protein secondary structure
N-H of every peptide bond is H-bonded to the C=O four amino acids away
Left or right handed
bonding in beta-sheets of protein
H-bonding between adjacent strands of polypeptide chains
can run parallel / antiparallel
simple monosaccharide general formula
(CH2O)n
eg. glucose C6H12O6
how are disaccharides formed
C w/ ald/ket can react w any hydroxyl group on a second sugar
glycosidic bond formed
eg. sucrose = glucose + fructose
what is a glycosaminoglycan
GAGs = unbranched polysaccharide chains made of repeating disaccharide units
name 5 GAGs
hyaluronic acid
chondroitin sulfate
dermatan sulfate
heparin sulfate
keratan sulfate
describe the properties of GAGs
polysacc chains are stiff + strongly hydrophilic
–> GAGs occupy huge volume relative to mass + negative charge density attracts could go cations, esp Na+ which is osmotically active sucking up lots of water
hence GAGs fill extracellular space
phospholipid molecule structure
hydrophilic head (glycerol+phosphate+polar functional group)
two hydrophobic fatty acid tails which can be saturated or unsaturated
lipid micelles are formed from…
phospholipids w a single tail, form a ball
cholesterol structure
rigid steroid ring + polar head group = hydrophilic
non polar hydrocarbon tail
amphipathic
cholesterol function
stiffer than phospholipids, can pack into membranes –> controls stiffness
important in cell signalling
