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science > Ib bio- unit 2.5-2.7 > Flashcards

Ib bio- unit 2.5-2.7 Flashcards

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Biology 101 flashcards
1
Q

provide a general description of nucleic acids

A
  • first discovered from extracted material from the nuclei of a cell
    -two types of nucteic acids: dna+rna
    -acids very large molecules
  • connected by linking together nucleotides (forms a polymer)
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2
Q

what are nucleotides made up of?

A
  • single unit of nucleic acid polymer
    -Sugar: 5 atom (pentose sugar)
    -phosphate (circle shape): acidic,negativelycharged part of nucleic acid
    -base (rectangle shape): contains nitrogen and has either 1 or 2 rings of atoms in each structure
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3
Q

what kind of bonds are the base and phosphate group linked to the sugar group by?

A

Covalent bonds

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4
Q

what are the 4 complementary bases and which pair together?

A

-adenine(A) and thymine(T)
-guanine(G) and cystine(C)

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5
Q

Purines

A

Adenine and guanine

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6
Q

Pyrimidines

A

Thymine and cytosine

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7
Q

What is the purpose of nucleosomes?

A

-a structural unit of a eukaryotic chromosome, consisting of a length of DNA coiled around a core of histones
-protects DNA from damage

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8
Q

Supercoiling

A

-allows chromosomes to be mobile in mitosis or meiosis
-CANNOT be transcribed for protein synthesis

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9
Q

how do the bases make up a genetic code?

A

-nucleotides are linked into a single arranged via condensation reactions
-covalent bonds are then formed between phosphate of one nucleotide and the next pentose sugar
-phosphate group attaches to 5-c of sugar and joins with the hydroxyl (OH) group that attachâtes to the 3-c sugar (called phospodiester bond)

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10
Q

what is a phosphodiester bond?

A

-when phosphate group joins with the hydroxyl group

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11
Q

What results with the phosphodiester when bonding the nucleotides?

A

-between the phosphate group and sugar group, a water molecule is formed (creating condensation reaction)
-results in formation of a long sided strand

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12
Q

TRUE or FALSE: DNA is a double strand of polynucleotides

A

true
-the sugar phosphate-backbone is on the outside(base on the inside) strand held together by hydrogen bonds between bases
-DNA twists into double helix held by hydrogen bonds

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13
Q

how is the double helix structure maintained in DNA?

A

-hydrogen bonds hold sections together and complementary base pairs
-sugar-phosphate backbone is hydrophilic so its on the outside
-nitrogenous bases are very reactive, so are protected on the inside

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14
Q

When does DNA rep occur?

A
  • during s-phase
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15
Q

provide a general description of enzymes

A

-enzymes are globular
-work as w catalysts
-speed chemical reactions w out altering themselves
-called biological catalysts cuz they are made by living cells and speed up biochemical reactions
-proteins (enzymes are proteins)

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16
Q

enzyme-substrate specificity

A

-only one enzyme can catalyze one reaction at a time
-however there are thousands of reactions that take place in cells

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17
Q

Enzyme activity

A

-three stages of enzyme catalysis
1) the sub binds to the active site of enzyme (some enzymes have two diff subtracted that bind to different parts of the active site
2) while the subs are in the active site they change into different chemical substances (products of the reaction)
3) products then separate from the active site, leaving it free for the next sub

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18
Q

Substrates

A

-substances that enzymes convert into products in reactions

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19
Q

what is the active site?

A

-substrates bind to this special surface of the enzyme
-the shape and chemical properties allows substrates to bind but not other substances
-subs are converted into products while they are bound to the active site
-the products are then released, freeing rage arrive sit to a bother catalyst reaction

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20
Q

TRUE or FALSE: one substrate for each enzyme and one per each active site

A

TRUE

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21
Q

whats a collision?

A

-the coming together of an active site and a substrate
-most reactions the subs are dissolved in water cuz water is in liquid state the particles dissolves in it come on contact with each and are allows in motion
-collions occur dream the random movement of subs and enzymes

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22
Q

list 4 advantages of immobilized enzymes

A

1) enzyme can easily be separated from the products in the reaction and prevent from contaminating other products
2) after being retrieved from the reaction mixture the enzyme may be recycled (useful cost savings)
3) immobilization increases the stability of enzymes to changes in the temp and pH (therefore reducing the rate of reactions)
4) subs can be exposed to higher enzyme conc than w enzymes (speeds up reaction rate)

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23
Q

What happens when an enzyme becomes denatured?

A

-structure gets altered so sub cant bind to active site anymore cuz the structure changes
-in many cases it causes the enzyme that were dissolved in the water to become insoluble and form precipitate

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24
Q

What could influence the denaturation in enzymes?

A

-high temps
-low temps
-high pH
-low pH

25
Q

What are 4 factors that can affect enzyme activity?

A

1) liquids (higher chances of collisions)
-the particles are in continual motion so when the liquid is heated there is more kinetic energy w the particles in it making both the enzyme and substrate move faster
2) heated enzyme (denaturation)
-when enzymes are heated the bonds vibrate more and the chance of breaking bonds is increased
-when bonds in the enzyme break, the structure changes in the active site
-when denaturation occurs, enzymes can no longer catalyze anymore reactions
3) pH sensitive (denaturation)
-most enzymes have the most ideal pH when their at the peak of their activity
-if the pH increases or decreases from the optimum enzyme actuality eventually stops
4) subs conc (denaturation)
-enzymes cannot catalyze a reaction w out the sub being in the active site
-if the conc is increased within the sub, collisions will take police more frequently

26
Q

Why would the increases of the conc result in the number of reactions being catylzed getting smaller?

A

-as the conc rises, collisions occur more which means more active sits are being occupied and being blocked so enzyme activity would diminish

27
Q

What key crucial step need to be carried out before replication can occur and briefly explain

A

1) first helical needs to unwind the double helix by breaking the hydrogen bonds in between the complementary bases

28
Q

What is helicase and what does it do?

A

-unwinds the double helix and separates the two strands by breaking hydrogen bonds in between the complementary bases in preparation for DNA rep
-helicase is a group of enzymes that uses energy from ATP
-polypeptide in globular shape

29
Q

What are two functions carried out by ATP in helicase for DNA rep

A

1) breaking hydrogen bonds
2) move the helicase along the DNA molecules

30
Q

what is DNA polymerase?

A

-links nucleotides together to form a new strand, using the pre- existing strand as a template
-after helicase occurs, each of the two strands acts as a template for the formation of a new strand. The assembly for this is carried out by DNA polymerase
-moves along the template stand in the same direction adsding one nucleotide at a time
-brings nucleotides into the position where hydrogen bonds could form
-once a nucleotide with the correct base has been brought into position and hydrogen bonds have been formed between the two bases, DNA polymerase links it to the end of the new strand
-this is done by making a covalent bond between the phosphate group of the free nucleotide and the sugar

31
Q

When would DNA rep occur in a eukaryotic cell during the cell cycle?

A

-during S phase in interphase (before mitosis or meiosis occur)

32
Q

Primase and primers in DNA rep

A

Primase: (the initializer) makes a primer so that the DNA polymerase knows where to get started to start to work
Primer: made up of RNA

33
Q

What are 4 key enzymes needed to operate DNA replication in order

A

1) helicase
2) primers
3) DNA polymerase
4) ligase

34
Q

TRUE or FALSE: DNA polymerase can build a new DNA strand in 5’ to 3’ direction or 3’ to 5’ direction

A

FALSE
-it can only build from 5’ to 3’ direction

35
Q

Leading vs lagging strand in the DNA rep

A

Leading strand: strand that DNA primers move along (5’ to 3’)

Lagging strand: is the strand that moves in the opp direction and creates gaps called Okazaki fragments that need to then be “glued together by the DNA ligase

36
Q

What is the PCR reaction

A

-a technique chain reaction used to make many copies of a selected DNA sequence
-useful when only a small of amount of DNA collected for testing (eg. blood samples from crime scenes, semen, hair, etc..)
-process artificially recreates DNA rep

37
Q

explain in 3 steps the pcr process

A

1) denaturation- dna sampled is heated to 95 degrees to break H bonds and separate into two strands
2) annealing- dna sample is cooled at 54 degrees allowing primers attach to opposite ends of the target sequence
3) elongation- a heat-tolerant DNA polymerase (taq) copies the strands

38
Q

How many copies of DNA seq can one cycle of PCR make

A

Two identical copies of DNA seq

39
Q

What are TAQ DNA polymerase

A

-used for PCR reaction
-comes from heat-resistant bacterium, (thermus aquatics) that lives in hot springs
-can resist denaturation at high temps so its can separate dna strands in pcr
-copies up to 1000 nucleotides per min

40
Q

DNA rep prokaryotes

A

1) DNA helical evidence unwinds the base pairs
2) DNA polymerase 111makes a complementary strand on the leading strand (adding nucleotides to the 3’ end of the complementary new strand)
3) RNA primasse follows helical et, leaving RNA primers
4) when it reaches another RNA primer it detaches leaving Okazaki frags
5) DNA polymerase moves along the rep fork rem,obvint rna primers

41
Q

function of DNA gryase

A

-stabilizes DNA helix as it is unwound by helicase

42
Q

function of single stranded binding
proteins (SSB)

A

-holds unzipped, single stranded sections of DNA apart during replication

43
Q

function of DNA polymerase III

A

-adds new DNA nucleotides in the 5’ to 3’ direction in prokaryotes

44
Q

function of DNA polymerase I

A

-replaces RNA primers with DNA nucleotides

45
Q

The process of transcription

A

1) the enzyme RNA polymerase binds to a site on the DNA at the start of the gate
2) RNA polymerase moves along the gene seperating DNA into single strands and pairing up RNA nucleotides w complementary bases on one strand of DNA
3) RNA polymerase dorms covalent bonds between the RNA nucleotides and bases
4) the RNA forms double helix
5) transcription stops at the end of the gene and the completed RNA molecule is released

46
Q

What is the products and purpose of transcription? (What are the results of it)

A

-the products is a molecule of RNA with a base sequence that is complementary to the template strand of DNA but w uracil instead of thymine
-now has to be translated

47
Q

antisense strand

A
  • also knows as the template strand or transcribed strand
    -5’ to 3’
    -is the top strand
48
Q

sense strand

A

-also known as the non template strand or coding strand
-bottom strand

49
Q

Describe the process of translation

A

-synthesis of polypeptides on ribosomes
-takes place in cytoplasm
1) an mRNA binds to a small subunit of the ribisome
2) a molecule of tRNA with an anticodon complementary to the first codon that is translated on the mRNA that binds to the ribisome
3) then a second RNA w anticodon complementary to the second codon on the mRNA binds (max of two tRNAs can be bound at the same time
4) the ribosome transfers the amino acid carried by the first tRNA to then amino acid on the second tRNA by making a new peptide bond
5) the ribisome moves along the mRNA so the first tRNA is released the second becomes first
6) another tRNA binds w an anticodon complementary to the next codon on the mRNA
7) the ribosome transfers the chain of amino acids carried by the first tRNA to the amino acid on the second tRNA, by making a new peptide bond

50
Q

What is “the promoter”

A

-a sequence located near a gene
-binding site of RNA polymerase and it catayzles the formations of the covalent bond between nucleotides during synthesis of RNA
-an enzyme and protein

51
Q

codons vs anticodons

A

Codons:
-cuz there is 4 diff bases and 20 amino acids one base cannot code for one amino acid
-a sequence of 3 bases on the mRNA strand is called a codon
-each codons code for a specific amino acid to be added to the polypeptide
-64 possible codons
-3 codons are “stop” codons that are for one translation

Anticodons:
-is the RNA strand complementary to the mRNA codon

52
Q

Introns vs exons

A

Introns:
-non-coding regions
-are removed from transcript

exons:
-coding regions
-stay in transcript strand

53
Q

mRNA splicing

A

-splicing of mRNA increases number of diff proteins on organism can produce
-prices during gene expression
-occurs in genes w multiple exons to remove introns
-takes out the introns to compete the mRNA

54
Q

Initiation of translation

A

-mRNA nines to the ribisomal subunit at an mRNA binding site
-an initiator and RNA molecule carrying methionine then binds at the start codon “AUG”
-then binds to small ribosomal subunit
-the indicator tRNA is in the p site and the next codon signals another tRNA to bind that occupies the A site
-peptide bond formed between A + P site

55
Q

Elongation of the peptide

A

-ribosome translocates three bases along the mRNA

56
Q

Termination of translation

A

-process continues until a stop codon is reached when the free polypeptide (completed polypeptide) is released

57
Q

The functions of free ribosomes

A

-synthesize proteins for use usually within the cell
-in eukaryotes, proteins are synthesized either in cytoplasm or endoplasmic reticulum
-proteins destines for use in the cytoplasm, mitochondria, and chloroplasts are sythenised by ribisomes free in the cytoplasm

58
Q

function of bound ribosomes

A

-synthesize proteins for use primarily for secretion or for use in lysosomes

science (20 decks)

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