B6 NUCLEIC ACIDS AND ATP

What’re nucleotides made up of?

• a phosphate group (with a negative charge)

• a nitrogenous base

• a pentose sugar

How is a polynucleotide formed?

nucleotides join together via a condensation reaction between the phosphate group of one nucleotide and the pentose sugar of another

What type of bonds are found in a polynucleotide?

• phosphodiester bonds

• chain of sugars and phosphates is known as the sugar phosphate backbone

What does DNA stand for?

deoxyribonucleic acid

What pentose sugar is found in DNA?

a deoxyribose sugar

What is the function of DNA?

• genetic material in the cell is DNA

• DNA controls the cell by providing information on how to make proteins

What is the structure of DNA?

• a double helix

• consists of 2 polynucleotide strands

• strands are held together by hydrogen bonds between the paired bases

What bases bind together in complementary base pairing?

• purine adenine pairs with pyrimidine thymine, forming 2 hydrogen bonds

• purine guanine pairs with pyrimidine cytosine, forming 3 hydrogen bonds

How is DNA antiparallel?

• 2 strands form a double helix with each strand running antiparallel to the other

• one strand runs in the 5’ to 3’ direction while the other strand runs in the 3’ to 5’ direction

What characteristics of DNA make it well suited to its job of storing and expressing genetic information?

• very stable molecule

• two complementary strands

• DNA is a long molecule

• 4 different bases

Why is DNA being a very stable molecule an adaptation of DNA?

• purine and pyrmidine pairing gives a regular and stable structure

• denaturation occurs at a higher temperature than most proteins

• sugar-phosphate backbone gives stability during unzipping

• DNA is coiled to form double helix which protects the bases from other chemicals

• strands do not separate at the hydrogen bonds unless required

Why is there 2 complementary strands an adaptation of DNA?

means that there are 2 copies of the information which is useful for repair, copying and error checking

Why is DNA being a very long molecule an adaptation of DNA?

it stores a lot of information

Why is DNA containing 4 different bases an adaptation of DNA?

the bases appear in any order so their sequence can encode information

What does RNA stand for?

ribonucleic acid

What is the pentose sugar found in RNA?

ribose sugar

What is found in RNA?

• a phosphate group

• a ribose sugar

• a nitrogenous base

What bases are found in RNA?

• adenine

• cytosine

• guanine

• uracil

What’re the 3 different types of RNA?

• messenger RNA

• transfer RNA

• ribosomal RNA

What is messenger RNA?

• mRNA

• a single stranded polynucleotide chain

• linear

• sequence of bases is complementary to the sequence of basses of the gene its copying

What is a sequence of 3 bases on a molecule of DNA known as?

a triplet

What is a sequence of 3 basses on a molecule of mRNA known as?

• a codon

• each codon codes for an amino acid

Whats transfer RNA?

• tRNA

• single stranded

• consists of a polynucleotide containing 75 nucleotides

• folded into a cloverleaf shape- held in place by hydrogen bonds

• has an amino acid attachment site

What is the region of 3 bases found on tRNA known as?

an anticodon

What does ATP consist of?

• adenine

• a nitrogenous organic base

• 3 phosphate groups

How is ATP formed?

• from ADP and Pi

• requires energy to add a phosphate group

• creates a high energy bond

• a condensation reaction

• involves ATP synthase

How is ATP broken down?

• hydrolysis reaction

• forms ADP and Pi

• releases large amounts of energy

• ATP hydrolase

• Pi can be used to phosphorylate other compounds to make them more reactive

What’re uses of ATP?

• active transport

• muscle contraction

• protein synthesis

• cell division

Why is ATP so useful?

• releases energy in small amounts

• broken down in one step

• makes energy available rapidly

• phosphorylates substances making them more reactive

• can be reformed

What are chromosomes?

• eukaryotic cells contain linear DNA molecules which have to be wound up to fit into the nucleus

• DNA associates with histones to help support the DNA (known as chromatin)

• DNA and histones are coiled tightly to make compact chromosomes

What’s the definition of a chromosome?

a thread like structure made up of one long DNA molecule

What’s the definition of a chromatid?

one arm of a double stranded chromosome after replication

What’s chromatin?

a complex made up from DNA and histones

What’s a homologous pair?

pairs of matching chromosomes

What does locus mean?

the position of a gene which is fixed on a particular chromosome

What’s an allele?

• different versions of a gene

• the order of bases in each allele is slightly different so they code for slightly different versions of the same polypeptide

What is a gene?

a base sequence of DNA that codes for the amino acid sequence of a polypeptide or a functional RNA

What’s a genome?

all of an individuals genes found in every nucleus

What’s a proteome?

the particular range of proteins that a cell produces using its DNA

What does a triplet code for?

each triplet codes for one amino acid, e.g. start and stop signals

What’re the three descriptions of the genetic code?

• universal

• non-overlapping

• degenerate

What does it mean that the genetic code is universal?

each triplet codes for the same amino acid in all organisms

What does it mean that the genetic code is non-overlapping?

each base in the sequence is read only once

What does it mean that the genetic code is degenerate?

most amino acids are coded for by more than one triplet

What is the non coding DNA found between genes?

• non-coding repeats

• each region contains a core sequence of bases which is repeated a number of times

What is the non-coding DNA found within genes?

• introns

What does prokaryotic DNA contain?

a single circular DNA molecule and multiple circular DNA molecules called plasmids

What’re key characteristics of prokaryotic DNA?

• circular DNA molecule

• shorter than eukaryotic DNA

• not associated with histones

• does not form chromosomes

• no introns or non-coding DNA

• fits into cell by supercoiling

What’re key characteristics of eukaryotic DNA?

• linear

• longer than prokaryotic DNA

• associated with histones

• forms chromosomes

• contains introns and non-coding repeats

• fits into cell as coiled very tightly to make a compact chromosome

What is DNA found in the mitochondria and chloroplast similar to?

prokaryotic DNA

What is the endosymbiotic theory?

• mitochondria and chloroplasts evolved from bacteria that were endocytosed into ancestral cells containing a eukaryotic nucleus

• mitochondria and chloroplasts in todays eukaryotes contain short, circular DNA not associated with proteins- like DNA found in prokaryotes