2B Proteins and DNA Flashcards
catalyst
a substance that speeds up a reaction without changing the substances produced or being changed itself
enzymes
proteins that act as biological catalysts for a specific reaction or group of reactions
specificity
the characteristics of enzymes that means that each enzyme will catalyse only a specific reaction or group of reactions; this is due to the very specific shapes which come form the tertiary and quaternary structures
anabolic reaction
a reaction that builds up (synthesises) new molecules in a cell
catabolic reaction
a reaction which breaks down substances within a cell
metabolism
the sum of the anabolic and catabolic processes in a cell
metabolic chain
a series of linked reactions in the metabolism of a cell
extracellular enzymes
enzymes that catalyse reactions outside of the cell in which they were made
intracellular enzymes
enzymes that catalyse reactions within the cell
mononucleotides
molecules with three parts - a 5-carbon pentose sugar, a nitrogen-containing base and a phosphate group - joined by condensation reactions
adenosine triphosphate ATP
a molecules that acts as the universal energy supply molecule in cells; it is made up of the base adenine, the pentose sugar ribose and three phosphate groups
deoxyribonucleic acid (DNA)
a nucleic acid that is the genetic material in many organisms
ribonucleic acid (RNA)
a nucleic acid which is the genetic material in some organisms and is involved in protein synthesis
ribose
a pentose sugar that is part of the structure of RNA
deoxyribose
a pentose sugar that is part of the structure of DNA
purine base
a base found in nucleotides that has two nitrogen-containing rings
(adenine, guanine)
adenine
a purine base found in DNA and RNA
pyrimidine base
a base found in nucleotides that has one nitrogen-containing ring
(cytocine, thymine, uracil)
thymine
a pyrimidine base found in DNA
guanine
a purine base found in DNA and RNA
cytosine
a pyrimidine base found in DNA and RNA
uracil
a pyrimidine base found in RNA
nucleic acids/polynucleotides
polymers made up of many nucleotide monomer units that carry all the information needed to form new cells
phosphodiester bond
bond formed between the phosphate group of one nucleotide and the sugar of the next nucleotide in a condensation reaction
conservative replication
a model of DNA replication which suggests that the original double helix remains intact and some way instructs the formation of a new, identical double helix made up entirely of new material
complementary base pairs
complementary purine and pyrimidine bases which align in a DNA helix, with hydrogen bonds holding them together (C-G, A-T)
genome
the entire genetic material of an organism
semiconservative replication
the accepted model of DNA replication in which the DNA unzips and new nucleotides align along each strand; each new double helix contains one strand of the original DNA and one strand made up of new material
isotopes
different atoms of the same element, with the same number of protons but a different number of neutrons; isotopes have the same chemical properties
DNA helicase
an enzyme involved in DNA replication that unzips the two strands of the DNA molecules
translation
the process by which proteins are produces, via RNA, using the genetic code found in the DNA; it takes place on the ribosomes
DNA polymerase
an enzyme involved in DNA replication that lines up the new nucleotides along the DNA template strands
DNA ligase
an enzyme involved in DNA replication that catalyses the formation of phosphodiester bonds between the nucleotides
ribosomes
the site of protein synthesis in the cell
triplet code
the code of three bases that is the basis of the genetic information in the DNA
gene
a sequence of bases on a DNA molecules which codes for a sequence of amino acids in a polypeptide chain (that affects a characteristic in the phenotype of the organism)
codon
a sequence of three bases in DNA or mRNA
messenger RNA
the RNA formed in the nucleus that carries the genetic code out into the cytoplasm
complementary strand
the strand of RNA formed that complements the DNA acting as the coding strand
degenerate code
- a code containing more information than is needed
- 20 amino acids, 64 base triples
- some amino acid are coded for by more than one base triplet
sense strand
the DNA strand that carries the code for the proteins to be produced
non-overlapping
a code where each codon codes for only one thing with no overlap between codons
point mutation
a change in a single base of the DNA code
antisense strand (template strand)
the DNA strand which acts as a template for an mRNA molecule
RNA polymerase
the enzyme that polymerises nucleotide units to form RNA in a sequence determined by the antisense strand of DNA
start codon
the sequence of bases which indicates the start of an amino acid chain - TAC; this is the code for the amino acid methionine
stop codon
one of three sequences of bases which indicate the end of an amino acid chain
anticodon
a sequence of three bases on tRNA that are complementary to the bases in the mRNA codon
transfer RNA
small units of RNA that pick up specific amino acids from the cytoplasm and transport them to the surface of the ribosome to align with the mRNA
translation
the process by which the DNA code is converted into a protein from the mRNA codon
transcription
the process by which the DNA sequence is used to make a strand of mRNA in the nucleus
polysomes
groups of ribosomes, joined by a thread of mRNA, that can produce large quantities of a particular protein
start codon
TAC (in DNA)
what amino acid does the start codon code for?
methionine
the first amino acid in every polypeptide chain is?
methionine
examples of intracellular enzymes
DNA polymerase, DNA ligase
examples of extracellular enzymes
digestive enzymes, lysozyme
what type of enzymes are trypsin and pepsin?
protease enzymes (protein digesting enzymes)
how does temperature have an effect on the rate of a reaction?
the number of successful collisions leading to a reaction increases at higher temperatures
temperature coefficient Q10
enzyme action (in a catabolic reaction)
how does a phosphodiester bond form?
by a condensation reaction between the phosphate group of one nucleotide and the hydroxyl group on carbon 3 of the pentose sugar of another nucleotide
describe the process of DNA synthesis
- the enzyme DNA helicase breaks the hydrogen bonds between the complementary base pairs of the original DNA molecule
- teh DNA double helix unwinds/unzips, and the two strands separate
- free nucleotides in the nucleus align iwht the complementary bases of the exposed polynucleotide strands, due to complementary base pairing
- 2 hydrogen bonds A,T 3 between C,G
- DNA polymerase catalyses the formation of phosphodiester bonds
- DNA helicase moves up the molecule from the 3’ end to the 5’ end of the leading strand
- DNA polymerase can only form phosphodiester bonds on the leading strand continuously
- fragments on lagging strand (okazaki fragments)
- DNA ligase joins the okazaki fragments together
how many hydrogen bonds form between A & T?
2
how many hydrogen bonds form between G & C?
3
in what direction does DNA helicase move up the DNA molecule?
from the 3’ end to the 5’ end of the leading strand
how does DNA polymerase bind to the parent strand?
DNA polymerase can only bind to the 3’ end of the parent strand
what does ATP stand for?
adenosine triphosphate
what does a ATP molecule consist of?
- a nitrogenous base Adenine
- a ribose sugar
- three phosphate groups
what are proteins made up of?
rRNA and proteins
ribosomes are the site of what?
site of proteins synthesis
what do ribosomes hold together during translation, and what do they act as?
they hold together the mRNA and tRNA and act as enzymes controlling the process of protein synthesis
describe the process of transcription
- DNA helicase unwinds and unzips the DNA, breaking hydrogen bonds between complementary bases
- beginning at the start codon, pre-mRNA forms alongside the template strand
- RNA polymerase catalyses formation of phosphodiester bonds between the nucleotides in the pre-mRNA, until the chain reaches a stop codon
4.mRNA chain separates from the DNA template - the DNA chains of the double helix rejoin
- splicing converts pre-mRNA into mRNA, and introns are removed
- mRNA leaves nucleus, through nuclear pore, to ribosomes for translation
introns
non-coding sections
exons
coding sections
describe the process of translation
- mRNA molecules attaches to surface of the ribosome at at the start codon
- tRNA carry individual amino acids to the surface of ribosome
- tRNA molecules with the complementary anticodon to the start codon in the mRNA, aligns opposite the mRNA held in place by the ribosome
- enzymes join the amino acids together via a peptide bond
- tRNA then brakes away and return to cytoplasm to pick up another amino acid
- ribosome moves along mRNA molecule until it reaches the stop codon
how many tRNA molecules can a ribosome hold at a time?
2
where is tRNA found?
in the cytoplasm
where is mRNA formed?
in the nucleus
mRNA
carries the instructions for a polypeptide from the DNA in the nucleus to the ribosomes where proteins are made
tRNA
picks up specific amino acids from the protoplasm and carries them to the surface of ribosomes
rRNA
makes up the bulk of the ribosomes themselves
