nucleic acids, atp, water and inorganic ions Flashcards
what does DNA stand for?
deoxyribose nucleic acid
function of DNA
codes for seq. of amino acids in primary struc. of protein —> determines tertiary struc. & function of protein
shape of DNA polymer
double helix (2 polynucleotide strands)
monomer for DNA
nucleotide
what does a DNA nucleotide consist of?
-a deoxyribose sugar
-a nitrogenous base (A,T,C,G)
-a phosphate group
how is a polynucleotide created?
condensation reactions between deoxyribose of one nucleotide and phosphate group of another
what is the bond between a deoxyribose and phosphate group called?
phosphodiester bond (strong cov. bond —> ensures genetic code isn’t broken down)
how many h-bonds between c & g?
3
how many h-bonds between a & t?
2
how does the struc. of DNA relate to the function?
1) sugar-phosphate backbone —> gives it stable struc., protects bases & prevents them from denaturing
2) double stranded —> replication can occur using one strand as template
3) weak h-bonds —> easy unzipping of 2 strands in helix during replication
4) complementary base pairing —> identical copies can be made
shape of rna
& what it consists of
- a ribose sugar, a nitrogenous base (A, U, C, G) & a phosphate group
- short, single stranded nucleotide chain
function of rna
to copy & transfer the genetic code from dna in the nucleus to the ribosomes
what are the diff types of rna?
•mRNA
•tRNA
•rRNA
mRNA (messenger rna)
- copy of a gene from a dna strand
- created in nucleus —> leaves nucl. to carry copy of gene to ribosome in cytoplasm
shape of mRNA
- single-stranded
- shorted than dna –> allows it to leave the nucleus
tRNA (transfer rna)
- only found in cytoplasm
- function —> attaches to a free amino acid & transfers it to the ribosome to create a polypeptide chain
- specific aa’s attach to compl. trna mols —> the 3 trna bases are compl. to the 3 mrna bases —> anticodon compl. to codon
shape of tRNA
single-stranded but folded to make a clover-leaf shape
rRNA (ribosomal rna)
combines with proteins to form ribosomes
diffs between rna & dna
monomers:
* dna has thymine, rna has uracil
* dna has deoxyribose, rna has ribose
polymers:
* dna large, rna short
* dna double stranded, rna single stranded
when does dna replication occur?
in interphase, before mitosis/meiosis
process of semi-conservative replication
edit using mindmap
- dna helicase breaks h-bonds between compl. bases in DNA strand
- double strand separates, 1 strand acts as a template strand
- free nucleotides join to exposed, compl. bases on template strand
- phosphate group joined to deoxyribose –> formation of sugar-phosphate backbone catalysed by DNA polymerase
evidence for semi-cons. repl.
-bacterial dna replicated in 2 types of nitrogen isotopes (nitrogen found in bases of dna)
-15N = heavy iso. & 14N = light iso.
-dna from 15N would have high density, dna from 14N would have low density
-exp —> 15N bacteria replicated in environment of 14N bacteria —> produces dna mols with half 15N/half 14N —> has medium density
what does atp stand for? what is it?
•adenosine triphosphate
•energy carrier mol. (delivers energy for life processes)
struc. of atp & how it’s formed
- a ribose sugar, an adenine base & 3 phosphate groups
- formed via a condensation reaction between adp + pi , uses atp synthase enzyme
(occurs during respiration, energy used)
what does adp stand for?
adenosine diphosphate
phosphorylation using pi (inorganic phosphate)
- energy can be transferred to other compounds during hydrolysis of atp
- pi that is released can be bonded onto other compounds —> makes them more reactive (happens to glucose at start of respiration)
how does atp release energy?
- carries energy in bonds between phosphate groups
- hydrolysis reaction occurs —> atp = adp + pi (uses atp hydrolyse enzyme)
- energy released from bonds when broken
what makes atp a good deliverer of energy?
- immediate source of energy —> only needs to break one bond —> bond is weak
- manageable source —> releases small amount of energy
uses of atp in organisms (name 3!)
•protein synthesis
•dna replication
•cell division
•active transport
•maintaining constant body temp (homeostasis)
•metabolic reactions
which types of bonds form between water molecules?
h-bonds
properties of water n how they make water important for biological processes
1) water = metabolite eg. hydrolysis/photosynthesis
2) water = important solvent in reactions —> transports things with ease eg. substances in plasma in blood/substances in water in xylem
3) high heat capacity —> buffers temps —> enzymes in body wont denature easily
4) large latent heat of vaporisation —> provides cooling effect with loss of water through evaporation
5) strong cohesion between water mols (due to h-bonds between mols) —> supports columns of water being pulled up xylem —> also produces surface tension to support small organisms
inorganic ions
•found in solutions eg. in cytoplasm & body fluids of organisms
•don’t contain carbon
H+ ions
•higher H+ conc. = lower pH
•pH affects enzyme controlled reactions
Fe2+ ions
•haemoglobin made from 4 poplypeptide chains, each with Fe2+ bound to prosthetic haem group in centre
•Fe2+ temporarily binds to oxygen, making Fe3+ until the oxygen is released
Na+ ions
•used for co-transport of glucose/amino acids into cells —> sodium moved out by active transport…
•affects osmosis/w.p
phosphate ions
•found in dna (form phosphodiester bonds with deoxyribose sugar)
•used to produce atp
•phosphorylates other compounds, making them more reactive
diff. between prokaryotic dna & eukaryotic dna
*prokaryotic dna = non-linear, eukaryotic dna = linear
*prokaryotic dna has no histone proteins, eukaryotic dna has histones
how do organisms have the same bases but different. shapes n functions?
- organisms have diff. genes
- the bases are sequenced in a diff. order
- the diff. a.a sequences code for diff. proteins
why does the tissue being viewed under a microscope need to be thin?
> so more light can go through
a single layer of cells can be viewed
when a dna strand is being produced via scr, why do the enzymes work in opposite directions?
- dna has anti-parallel strands
- the nucleotides are aligned differently in both strands
- enzymes have actives sites with specific shapes
- only substrates with compl. shape can bind to active site of dna polymerase
why is a certain virus only found in a certain part of the body?
- outside of virus has antigen proteins
- antigen proteins have compl. shape to receptor protein
- receptor proteins only found on membrane of cell
