2.1.3 nucleic acids and 2.1.4 Enzymes Flashcards
Biological catalysts
catalysts in living organisms
work at lower temp and pressure to chemical catalysts
speeds up reaction without being used up
what type of protein are enzymes
globular
specific shape
water soluble
what do enzymes do to the activation energy of a reaction
decrease it
less energy needed to start a reaction
provide alternative pathway by holding reacting groupps close together or put strain on the bonds
Anabolic reactions
enzymes make large molecules out of smaller ones
Catabolic reactions
break large molecules into smaller ones
metabolism
sum total of all reactions happening in cell or organism
metabollic pathway
essential process for life
Intracellular enzymes
enzymes produced and act inside the same cell
extracellular enzymes
enzymes act outside the cell in which they were produced
why is extracellular enzymes neccessary
large molecules cant fit into the cell directly through the plasma membrane
example of intracellular enzyme
catalase
ensure hydrogen peroxide is broken down to oxygen and water
example of extracellular enzyme
digestion
break large molecules into smaller ones
Amylase
produced by salivary glands and pancreas
released into saliva and pancreatic juice
breaks down starch polymers into maltose
trypsin
a protease
digestion of proteins into smaller peptides which can be further broken down into amino acids
lock and key hypothesis
substrate fits into active sit of only one enzyme
when substrate binds it forms enzyme substrate complex
products are produced and released
induced fit hypothesis
substrate cause enzyme to change shape slightly as it binds
shape of active site is NOT fixed
Active site
made of 6-10 amino acids
precursor activation
the activation of an inactive enzyme
how can enzymes be activated
change to their tertiary structure
change in their enviroment
addition of a non protein helper (cofactor)
cofactors
non protein molecule that binds to an enzyme to activate it
An enzyme that needs one can’t function without it
3 types of cofactors
prosthetic groups
inorganic ions
coenzymes
prosthetic groups
bind tightly to become a permanent part
coenzyme
bind loosely
enzyme activity definition
indicates the rate of reaction catalysed by the enzyme expressed
factors that affect enzyme activity
temperature
ph
enzyme concentration
substrate concentration
why is rate not controlled
start particles move fast
collide making lots of enzyme substrate complexes
reaction slows as less available to collide
reaction stops when all are used up
inhibitors
a molecule that binds to enzymes to prevent them carrying out their catalytic functions
slow down rate of enzyme controlled reactions
competitive inhibitors
molecule with simular shape to active site binds
blocks substrate binding
less enzyme substrate complexes formed
reduced rate of reaction
non competitive inhibitors
bind to allosteric site causing change to tertiary structure
active site changes shape so substrate is no longer complementary
less ESC’s formed
reversible binding
binds temporarily
non covalent
enzyme goes back to normal
irreversible binding
permanent binding
covalent
permanently changed
product inhibition
product of reaction inhibits enzyme involved in that reaction
can be competitive or non competitive
always reversible
DNA
deoxyribonucleic acid
found in nucleus
carries code to make all proteins in body
RNA
ribonucleic acid
used to make proteins
3 forms - messenger , transfer, ribosomal
structures of nucleotide
phosphate
pentose sugar
nitrogenous base
how are nucleotides linked together
condensation reaction
phosphate group at 5th carbon of pentose sugar forms covalent bond with hydroxyl group at 3rd carbon of pentose sugar of adjacent sugar
forms phosphodiester bond
name of bond between nucleotides
phosphodiester
pyrimidines
smaller bases which contain single carbon ring structures
Thymine and cytosine
purines
larger bases which contain double carbon ring structures
adenine and guanine
pure as gold (Ag)
ATP structure
3 phosphate groups
ribose sugar
adenine base
formation of ADP
hydrolysis reaction of ATP where water used to split bond between 2nd and 3rd phosphate group releasing the phosphate group Pi and a small amount of energy
reaction to convert ADP back to ATP
add energy from food to re join bond
ADP add Pi
phosphate group re joins releasing a water molecule
condensation reaction
structure of dna
double helix
made of 2 anti-parallel DNA nucleotides held together by hydrogen bonds between complementary base pairs
sense strand definition
contains genetic code for protein
antisense strand definition
acts as a template strand for transcription
runs 3’ to 5’
complementary to sense strand
complementary base pairing rules
adenine and thymine form 2 hydrogen bonds
cytosine and guanine form 3 hydrogen bonds
which parts of dna are hydrophobic
nitrogenous base
which parts of dna are hydrophilic
phosphate group
chromosome definition
long strand of dna made up of many genes
chromatin
chromosomes wrapped around histones
histones
proteins dna’s wrapped around it
gene
short section of dna that codes for a particular protein
dna extraction practical method
crush strawberry using pestle and mortar with 20cm3 dna extraction buffer
strain into beaker using tea strainer and muslin
pour filtrate into boiling tube
add 5cm3 ethanol
let stand for 5 minutes
dna will form white precipitate on top layer
use inoculating loop to scoop out
why is strawberry crushed
to break up cells
function of adding detergent to strawberry
break up cell wall and phospholipid bilayer
function of adding protease enzyme during dna extraction
break down histones to separate from dna
function of adding salt during dna extraction
helps make it less soluble
function of adding ethanol during dna extraction
to make dna become visible
what is DNA replication and when and where does it take place
copying of dna
happens in the nucleus immediately before mitosis in late interphase
semi conservative replication definition
each daughter DNA molecule has one new and one old strand
DNA replication steps
dna helicase unwinds dna molecule and travels along it breaking the hydrogen bonds between complementary base pairs
makes 2 single strands
each strand acts as template for assemble of new complementary strand
free dna nucleotides attract to exposed bases on template strand and hydrogen bonds form between them
DNA polymerase travels along new strand catalysing the joining of nucleotides by phosphodiester bonds
each new dna molecule has one new and one old strand
where do the free dna nucleotides come from in dna replication
cytoplasm
conservative dna
dna copied and get one new strand
dispersive replication
dna is cut into several parts and each section is copied and reattached to produce 2 molecules
Experiment on bacteria for DNA replication
1- heavy nitrogen growth medium . bacteria uses heavy nitrogen to synthesis new dna
2- moved into light nitrogen medium. Bacteria uses light nitrogen to synthesis nitrogenous bases in dna. Band moves slightly up tube
3- still in light nitrogen. 2 molecules are now made of light nitrogen
if carried on more pure light nitrogen will be forms but 2 molecules will still always have only 1 strand of light
what is the genetic code
code that determines the order of amino acids in each and every protein in all living things
where is the genetic code found
our DNA in the nucleus
mRNA that goes to ribosome for protein synthesis
why is there 2 versions of the genetic code
1st version allows you to translate dna
2nd version allows you to translate rna
triplet
3 bases codes for one amino acid
what is the genetic code described as
triplet
non-overlapping
degenerate
universal
Non-overlapping for genetic code
each base is read in only one triplet /codon
degenerate in terms of the genetic code
each amino acid has more than one triplet code that codes for it
what does it mean by the genetic cod is universal
same code used for all living things
gene
short section of DNA that codes for a specific protein
why don’t ribosomes go straight into the nucleus to make the protein
dna might get damaged
ribosomes needs single strand whereas dna is double stranded
overview of transcription
genes copied from dna to mrna
happens in nucleus
overview of translation
happens in ribosomes
code on rna is used to assemble the amino acid in the correct order to make protein
steps for protein synthesis
transcription and translation
messenger RNA
carries code from gene to ribosome
ribosomal RNA
joined with protein to form ribosome
small subunit binds to mRNA
transfer RNA
amino acid on it is specific to each tRNA anticodon
brings amino acid to mRNA in translation
steps in transcription
dna is unwound by dna helicase
dna helicase travels up centre of dna breaking the hydrogen bonds to form 2 separate strands
antisense strand is used as template (3’ to 5’)
free RNA nucleotides base pair with complementary bases on template strand Uracil replaces thymine
RNA polymerase catalyses formation of phosphodiester bonds
continues util end of gene
mrna leaves nucleus via nuclear pore and goes to ribosome
where does translation occur
ribosome
translation steps
end of mRNA binds between small and large subunits of ribosome
ribosome moves along mRNA until finds start codon
tRNA with complementary anticodon to start codon binds to mrna
another trna with complementary anticodon to nxt codon binds
the 2 amino acids then form a peptide bond
this releases the 1st amino acid
this repeats until stop codon is reached and then the ribosome becomes detached from polypeptide chain
