topic 1 Flashcards
monosaccharide
single sugar monomer
disaccharide
sugar made from 2 monosaccharides joined by a glycosidic bond in a condensation reaction
polysaccharide
polymer made up of long chains of monosaccharides joined by glycosidic bonds
what is the difference between alpha and beta glucose?
on alpha glucose the OH group on carbon-1 is below the plain of the ring
what bond/reaction joins monosaccharides?
condensation/glycosidic
what reaction splits a glycosidic bond between monomers?
hydrolysis reaction
glucose structure
contains 6 carbon atoms
major energy source for most cells
very soluble
main form carbs are transported around the body
starch structure
stored in plastids (leaves and potatoes)
produced from glucose in photosynthesis
broken down during respiration for energy
made of many alpha glucose molecules
amylose has a helical structure, 1-4 bonds
amylopectin is branched so more compact, 1-6
multiple chains ends - rapid hydrolysis as more attachment points for amylase enzyme
glycogen structure
insoluble
main carb storage molecule in animals and fungi
1-6 glycosidic bonds
compact so large amount of glucose is stored
stored in liver and muscle cells in animals - power respiration
cellulose
beta glucose
main component of plant cells
very high tensile strength
h-bonds form between adjacent hydrogen molecules
h-bonds between cellulose molecules form microfibrils which then form thicker fibre
fibres cross link - forms cell wall
stops cell wall bursting under pressure
allows turgidity
cannot be digested by most animals
triglyceride
one glycerol and 3 fatty acids joined by a condensation reaction where 3 water molecules are removed and an ester bond forms
ester bond
formed between the carboxyl group of a fatty acid and the hydroxyl group of glycerol in a condensation reaction
saturated fats
NO double bonds between carbon atoms
linear, lie parallel close to each other
more dense than unsaturated
solid at room temp
unsaturated fats
double covalent bonds between at least 2 carbons
cannot lie parallel
less dense than saturated
liquid at room temp
use of lipids
energy store
respiratory substrate
thermal insulation
buoyancy
electrical insulator
insoluble in water - don’t interfere with chemical reactions in cells
protect organs from mechanical shock
phospholipids
glycerol molecules with 2 hydrocarbon tails and a phosphate
phosphate is polar/hydrophilic
fatty acids are not polar/hydrophobic
form phospholipid bilayer in water
amino acid structure
r-groups control bonding between amino acids
control protein structure
polar or non-polar
forming proteins
hydrogen from amino group reacts with the hydroxyl group of the carboxyl group (of another amino acid) to form a peptide bond
water is produced in the condensation reaction
peptide bond
strong covalent bond
polypeptides
formed when many amino acids are bound togehter via a series of condensation reactions
can be several thousand amino acids
when folded its called a protein
protein bonding
ionic
disulphide
hydrogen
hydrogen bonding (proteins)
partially positive r-group and a partially negative r-group
weak bond which can be broken by increase temps or pH
ionic bonding (proteins)
r-group with a full negative charge and one with a full positive charge
stronger than hydrogen
broken by changes in pH
disulphide bonding (proteins)
R-group of 2 cysteine amino acids
very strong covalent bonds
holds together different polypeptide chains in proteins with quaternary structure
protein structure
primary
secondary
tertiary
quaternary
primary structure
linear sequence
number and order of amino acids determined by DNA sequence
only involves peptide bonding
determines 3D shape + properties of protein
varies:
number of amino acids
order of amino acids
type of amino acids used
secondary structure
hydrogen bonds between amine and carboxyl group of adjacent amino acids
most fibrous proteins have this structure
2 different types: alpha helix and b pleated sheet
- both hydrogen bonds occur between the oxygen of carboxyl group and hydrogen of amino group
- (alpha helix) 1 amino acid forms a hydrogen bond 4 places ahead of it in the chain
- (B pleated sheet) polypeptide is folded into regular pleats
tertiary structure
protein becomes folded and takes on a 3D shape
occurs in the ER
5 types of bonds holding the structure together
(ionic, hydrogen, disulphide, hydrophobic/hydrophilic interactions)
globular shape
quaternary structure
3D shape arrangment of more than one polypeptide chain
assosiation of 2 or more polypeptide chains with each other
fibrous proteins
polypeptide form long chains running next to each other
linked by disulphide cross bridges - stable + strong
structural functions a) keratin b)collagen
collagen
found in: tendons, cartilage, bone, sea anemones, egg cases of dogfish
strong
inelastic
flexible
(primary structure) repeat sequence of 3 amino acids, every 3rd amino acid is glycine
(quaternary) 3 helical polypeptides are wound very closely around each other, held by h-bonds
forms a tight coil
triple helix - tropocollagen
staggered ends so no line of weakness
globular proteins
most tertiary structure some quaternary
roughly globular
shape determines its function
haemoglobin
large globular protein
4 polypeptide chains linked by disulphide bonds
polypeptide chains arranged around an iron containing haem group
glycoproteins
water reduces their viscosity
lubricants found in mucus and synovial fluids
lipoproteins
important in the transport of cholesterol in the blood
DNA
deoxyribonucleic acid
double helix made of 2 polynucleotides joined together by h-bonds
RNA
ribonucleic acid
single stranded
mRNA, tRNA, rRNA
purines
adenine and guanine
2 nitrogen containing rings
pyrimidines
thymine, cytosine, uracil
single ring structure
1 nitrogen containing ring
nucleotides
join together via phosphodiester bonds formed in condensation reactions
DNA replication
semi conservative - uses strand from original DNA molecule as template, new DNA contains 1 old and 1 new strand
helicase
polymerase
ligase
helicase in DNA replication
breaks h-bonds between base pairs
forms 2 separate strands
DNA polymerase (replication)
joins adjacent nucleotides on new strand in 5’ to 3’ direction
via condensation reactions
form phosphodiester bonds
ligase (replication)
leading strand replicated continuously in direction of replication fork
lagging strang is replicated in Okazaki fragments in opposite direction
gene
a sequence of bases on a DNA molecule that codes for a specific sequence of amino acids to make a polypeptide
structure of mRNA
long ribose polynucleotide
single stranded + linear
codon sequence is complementary to exons of 1 gene from 1 DNA strand
structure of tRNA
single stranded
clover shape
anticodon at one end - binds to complementary mRNA codon
amino acid binding site at the other - amino acid corresponds to anticodon
transcription
molecule of mRNA is made in the nucleus
h-bonds between complimentary bases uncoil (DNA helicase)
antisense strand is used as a template to make mRNA
sense strand
free nucleotides line up on template strand, join with adjacent nucleotides by phosphodiester bonds (DNA polymerase)
mRNA goes out of the nucleus through nuclear pore and attaches to ribosome in cytoplasm
translation
amino acids join together to form a polypeptide chain
mRNA attaches to ribosome on RER
tRNA molecules binds to mRNA codon
h-bonds form between the anitcodon of tRNA and codon of mRNA
2nd tRNA molecules binds to the next mRNA codon
2 amino acids form a peptide bond
3rd tRNA molecules joins and the 1st leaves the ribosome
ATP is used to form peptide bonds
polypeptide chain is made
stops when a stop codon is reached on the mRNA
genetic code
triplets of bases - codons
non overlapping - each triplet is only read once
degenerate - more than one codes for an amino acid
universal - same bases and sequencing used by all species
effect of degenerate
reduces effect of mutations (deletions/insertions/substitutions)
mutations of DNA
a change in base sequence may still code for the same amino acid
sickle cell anaemia - harmful base sequence change
deletions or insertions is more likely to be harmful as they create a frame shift
start codon
nucleotides triplet AUG on mRNA codes for amino acid met
stop codon
nucleotide triplets UAA UAG UGA which dont code for an amino acid
introns
majority of DNA
consists of non-coding regions within and between genes
extrons
regions of DNA that code for amino acid sequences
separated by 1 or 2 introns
non-disjunction
can cause down’s syndrome and turner’s syndrome
spindle fibre snaps and 2 copes of chromosome 21 enter the egg
if egg is fertilised the zygote has 3 copies of chromosome 21
enzymes
large globular proteins
tertiary structure
metabolic rate
catalyse anabolic and catabolic reactions
biological catalyst
induced fit
shape of an active site changes shape in response to a substrate entering and forming an enzyme substrate complex
active site becomes even more complimentary to shape of substrate
a reaction is more likely
what affects enzymes rate of activity
temperature
pH
enzyme concentration
substrate concentration
temperature effect on enzymes
increases up to optimum temperature and after decreases as enzymes have denatured
pH effect on enzymes
works best at optimum pH otherwise decrease until it stops
enzyme concentration effect on enzymes
increase rate up to a point and then it doesn’t have an effect
substrate concentration affect on enzymes
increases up to a point until all active sites are used up
inhibitors
can affect enzymes when they are present
competitive or non-competitive
reversible or non-reversible
competitive inhibitors
similar structure to common substrate
competition depends on concentration
can be:
reversible - increase substrate concentration reduces inhibition
irreversible - binds permanently to the active site
non competitive
when inhibitor binds to the inhibitor site the shape of the active site changes and the substrate can no longer bind to it
cannot be reversed
inorganic ions
required for growth and development
nitrate
phosphate
magnesium
calcium
nitrate ions
make DNA and amino acids
protein for growth and repair
phosphate ions
make ATP, ADP and nucleic acid
magnesium ions
produce chlorrophile
photosynthesis pigment - glucose - respire
calcium ions
form calcium pectate
middle lamella in plant
water
partially negative - oxygen
partially positive - hydrogen
dipolar
hydrogen bonding
weak electrostatic forces
cohesion
water molecules are attracted to each other
allows water to move as a continuous column of water
hydrogen bonding causes more cohesion between molecules
leads to high specific heat capacity and high latent heat of evaporation
universal solvent
ionic solutions are dissolved in water
good transport medium because so many substances dissolve in it
maximum density of 4
lower temps it becomes more dense
hydrogen bonds stabilise
less dense than water
insulates water below + prevents freezing
provides a habitat for many animas
cannot be compressed
some organisms rely on hydraulic mechanisms
adhesion
water molecules are attracted to other molecules
high surface tension
water molecules below the surface are more attracted to each other than the air molecules above
essential for metabolic reactions
benefit of adhesion and cohestion
allows capillary action to take place
