Nucleic acids Flashcards by Charlotte Priday

Is RNA a polymer

Yes

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What is the monomer of RNA

A nucleotide

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What are the 3 components of the nucleotide that makes up RNA

Ribose (pentose sugar)
A nitrogenous base (A,G,C,U)
A phosphate group

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Name 4 differences between RNA and DNA

RNA contains ribose instead of deoxyribose in DNA
RNA has the base uracil whereas DNA has thymine
RNA is single stranded whereas DNA is double
RNA polymer is a relatively short polynucleotide chain whereas DNA is long

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What are the functions of RNA

Copy and transfer the genetic code from DNA in the nucleus to the ribosomes
Some RNA also combines with proteins to create ribosomes

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What are the 3 types of RNA

mRNA (messenger)
-tRNA (transfer)
-rRNA (ribosomal)

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What is mRNA

A copy of a gene from DNA

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Where is mRNA created

In the nucleus

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Why is mRNA created instead of just having DNA

Because DNA is too large to leave the nucleus whereas mRNA is much smaller because it’s only the length of one gene therefore can fit through the nuclear pores

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Why is mRNA short lived

Because once the genetic material has left the nucleus it has a risk of being exposed to enzymes which can hydrolyse the polymers

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How many bases on mRNA code for one specific amino acid

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What is the name of the 3 bases that code for an amino acid

A codon

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Where is tRNA found

In the cytoplasm

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Is tRNA single or double stranded

Single

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What is the shape of mRNA

A straight line

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What is the shape of tRNA

Folds in on itself to create a shape that looks like a cloverleaf

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What type of bonds hold the cloverleaf shape of a tRNA molecule

Hydrogen bonds

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What is the function of tRNA

To transfer amino acids

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At the top of the tRNA molecule there are 3 exposed bases, what is the name for these bases

The amino acid attachment site

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What is the function of rRNA

Combines with protein to make ribosomes

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Differences between the DNA and RNA monomers (x2)

DNA contains the base thymine whereas RNA contains uracil instead
DNA contains the pentose sugar deoxyribose, whereas RNA contains the pentose sugar ribose

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What is the function of DNA

Carries genetic code for protein synthesis

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What is the name of the monomer making up nucleic acid

Nucleotides

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What is the name of the polymer made from nucleotides

Polynucleotides

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What reaction joins nucleotides together to form a polynucleotide

A condensation reaction

What is the name of the bond when nucleotides join together via a condensation reaction

phosphodiester bond

How many polynucleotides make up DNA

How many polynucleotides make up RNA

What are the 3 main components of a nucleotide

- Phosphate group - Pentose sugar - Nitrogen-containing base

In DNA, what is the name of the pentose sugar

Deoxyribose

In DNA, what are the names of the 4 possible nitrogen-containing bases

- Adenine - Thymine - Cytosine - Guanine

In RNA, what is the name of the pentose sugar

Ribose

In RNA, what are the names of the 4 possible nitrogen-containing bases

- Adenine - Cytosine - Guanine - Uracil

What is the proper name for ATP

Adenosine triphosphate (must remember the osine)

What is the name of the pentose sugar in ATP

Ribose

What is the name of the nitrogen-containing base in ATP

Adenine

In ATP what is the name of the phosphate group

Triphosphate group

What type of structure do purine nitrogenous bases have

Double ring

What are the 2 nitrogenous bases that are purine bases

- Adenine - Guanine

What type of structure do pyrimidine, nitrogenous bases have

Single ring structure

What are the 3 nitrogenous bases that have pyrimidine structures

- Thymine - Cytosine - Uracil

What type of nitrogenous base is bigger, purine bases or pyrimidine bases

Purine bases are bigger

How many hydrogen bonds does the purine base adenine make

2 hydrogen bonds

How many hydrogen bonds does the purine base guanine make

3 hydrogen bonds

In DNA, what is the ratio of purine bases to pyrimidine bases

1:1

What is the name of the structure of DNA

Double helix

DNA has a sugar-phosphate backbone, what is it's role in overall DNA function

Gives strength to DNA molecule

DNA is composed of 2 chains held together by weak hydrogen bonds, what is this features relation to the overall function

The chains can be separated for transcription (protein synthesis) and replication

DNA has a coiled structure why is this useful

Protects the hydrogen bonds therefore reducing corruption of genetic code

DNA contains many weak hydrogen bonds what benefit does this have

Make DNA a stable molecule

DNA is a long molecule, what impact does this have on the role of DNA

It can store a lot of genetic information (genes)

Where is DNA found

Nucleus

Where is RNA found

- Nucleus - Cytoplasm

What forms from the hydrolysis of ATP

ADP and Pi

What is the enzyme that catalyses the hydrolysis of ATP

ATP hydrolase

Is the hydrolysis of ATP an exergonic or endergonic reaction

Exergonic reaction

What molecules are required to synthesise ATP

ADP and Pi

What is the name of the enzyme that catalyses the synthesis of ATP

ATP synthase

Is the synthesis of ATP endergonic or exergonic

Endergonic reaction

What is the function of ATP

An immediate source of energy for biological processes

Why is it essential that cells have a constant, steady supply of ATP

So the can under go all the chemical reactions in the cell

What process makes ATP

Respiration

Why is ATP described as an immediate source of energy

Because only one bond has to be hydrolysed to release energy - so very rapid

Why is ATP releasing small, manageable amount of energy better than the energy released from glucose

- Less energy is wasted - Stops cells from overheating since a lot of waste energy is released in the form of heat - Glucose would release large amounts of energy

Why is ATP being a small and soluble molecule beneficial

It can easily be transported around the cell

How many bonds in ATP need to be broken/ hydrolysed to release energy, and why is this better than glucose

Only 1 bond needs to be hydrolysed, so is an immediate energy release, whereas glucose would need several bonds to be hydrolysed to release all its energy

What does phosphorylation mean in terms of ATP

The inorganic phosphate group can be bonded to new molecule and make that molecule more reactive

Why is ATP not being able to pass out of the cell a benefit

So the cell always has an immediate supply of energy whereas glucose can run out

When does DNA replication occur in the cell cycle

Before cell division

What is the name of the process of DNA replication

Semi-conservative replication

What does semi-conservative replication mean

In the daughter DNA one strand is from the parental DNA and one strand is newly synthesised

What are the 2 complementary base pairs

- Adenine and thymine - Cytosine and guanine

What are the names of the 2 key enzymes involved in semi-conservative replication

- DNA helicase - DNA polymerase

What is the role of DNA helicase

This enzyme breaks the hydrogen bonds between complementary base pairs between the 2 strands within a double helix

What is the first step needed to start the DNA replication process

The DNA double helix needs to unwind using the enzyme DNA helicase by breaking the hydrogen bonds

Once the double helix of DNA has separated what do the 2 parental strands now act as

A template

Once the 2 strands of DNA have been separated, what does the free floating DNA nucleotides within the nucleus do

They are attracted to their complementary base pairs on the template strands of the parental DNA - but these nucleotides are not attached together yet so still monomers

Once the free floating nucleotides that are attracted to the template DNA strand align adjacent to one another, what enzyme catalyses the joining of these adjacent nucleotides

DNA polymerase

What is the function of DNA polymerase

To join together adjacent nucleotides

What are the names of the DNA replication theories

- Conservative - Semi-conservative - Dispersive

Explain what the theory semi-conservative replication of DNA is

Each replicated DNA molecule contains one of the original DNA strands and one newly synthesised DNA strand Conservative one entire original strand

Explain what is meant by conservative DNA replication

The original DNA remains intact following DNA replication and the two newly synthesised strands of DNA join together

What are the names of the men who conducted the experiment proving semi-conservative DNA replication

- Meselson - Stahl

When Meselson and Stahl carried out their experiment on DNA replication what were the 2 different isotopes of nitrogen that were used, and which is the lighter one

- Nitrogen-14, lighter - Nitrogen-15, heavier

What bacteria did Meselson and Stahl use in their experiment

Ecoli

In the first generation of bacterial growth in the Meselson and Stahl experiment, what medium was the ecoli grown in and how was this proven

Grown in nitrogen-15 medium and once placed in a centrifuge the DNA accumulated at the bottom of the tube

After the Ecoli had replicated in the nitrogen-15 medium, what did Meselson and Stahl do next

They took the Ecoli out of the nitrgoen-15 medium and placed it in a nitrogen-14 medium

In the first generation of Ecoli, placed in the nitrgon-14 medium, what happens when the DNA is centrifuged

There is only one band but it's higher up the tube compared to the Ecoli that only contained nitrogen-15

In the 2nd generation of ecoli DNA replication, what happens to the DNA when centrifuged

2 bands are formed - one in the middle of the tube - 50% DNA is nitrogen-15 and nitrogen-14 - One at the top of the tube- 50% DNA is nitogen-14 and nitrogen-14

In the 3rd generation of ecoli DNA replication, what happens to the DNA when centrifuged, what are the %

2 bands form - one in the middle- 25% DNA is N-15 and N-14 - one thicker band at the top- 75% DNA is N-14 and N-14

Name the type of bond between complementary base pairs

Hydrogen bonds

Name the type of bond between adjacent nucleotides in a DNA strand

Phosphodiester bonds

Describe the structure of DNA (5 marks)

- Polymer of nucleotides - Each nucleotide formed from deoxyribose, a phosphate group, and an organic base - Phosphodiester bonds - Double helix held by hydrogen bonds - Hydrogen bonds between adenine, thymine and cytosine, guanine

Describe how a phosphodiester bond is formed between 2 nucleotides within a DNA molecule (2 marks)

- Condensation reaction - Between phosphate and deoxyribose - Catalysed by DNA polymerase

Name the protein associated with DNA in a chromosome

HIstone

Describe how the separation of the 2 DNA strands in semi-conservative DNA replication (2 marks)

- DNA helicase - Breaks hydrogen bonds between base pairs / breaks hydrogen bonds between polynucleotide strands

Describe the role of DNA polymerase in the semi-conservative replication of DNA (2 marks)

- Joins adjacent DNA nucleotides - Catalyses condensation reactions - Phosphodiester bonds

Name the 2 scientists who proposed models of the chemical structure of DNA and of DNA replication

Watson and Crick

Give 2 features of DNA and explain how each one is important in the semi-conservative replication of DNA ( 2 marks)

- Weak hydrogen bonds between bases allow 2 strands to separate - 2 strands, so both can act as templates - Complementary base pairing allows accurate replication

Describe the role of 2 names enzymes in the process of semi-conservative replication of DNA (3 marks)

- DNA helicase causes breaking of hydrogen bonds between DNA strands - DNA polymerase joins the DNA nucleotides - Forming phosphodiester bonds

Describe the function of DNA helicase

Breaking hydrogen bonds between bases

Describe the function of DNA polymerase

Joins adjacent nucleotides / forms. phosphodiester bonds

Contrast the structures of ATP and a nucleotide found in DNA to give 2 differences (2 marks)

- ATP has ribose and DNA nucleotides has deoxyribose - ATP has 3 phosphate groups and DNA nucleotide has 1 phosphate group - ATP- base always adenine and in DNA nucleotide base can be different

Define universal, non-overlapping and degenerate (3 marks)

- Universal- The same codon/ triplet always codes for the same amino acid - Non-overlapping - Each base is only part of one triplet/ codon - Degenerate - More than one codon/ triplet codes for each amino acid

Describe the role of DNA polymerase in the semi-conservative replication of DNA (2 marks)

1. Joins (adjacent DNA) nucleotides; 2. (Catalyses) condensation (reactions); 3. (Catalyses formation of) phosphodiester bonds (between adjacent nucleotides);

Give 2 ways in which the arrangement of prokaryotic DNA is different from the arrangement of the human DNA

1. Circular (as opposed to linear); 2. Not associated with proteins/histones ; 3. Only one molecule/piece of DNA OR present as plasmids;

Nucleic acids Flashcards

(106 cards)