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Crypt A level Biology > Module 2: Nucleotides and Nucleic Acids > Flashcards

Module 2: Nucleotides and Nucleic Acids Flashcards

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1
Q

Name the 2 types of nucleic acid

A

DNA (deoxyribonucelic acid)

RNA (ribonucleic acid)

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2
Q

What are the components of a nucleotide?

A

Nitrogenous base
Pentose sugar
Phosphate group

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3
Q

What are the 5 bases?

A 
Adenine 
Guanine 
Thymine 
Cytosine 
Uracil
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4
Q

Which of the 5 bases are only in RNA?

A

Uracil - replaces thymine

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5
Q

Which of the bases purines? Define purine

A

Adenine and guanine

Larger bases which contain a double carbon ring structure

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6
Q

Which of the bases are pyrimidine? Define pyrimidine

A

Cytosine, thymine, uracil

Smaller bases which contain a single carbon ring structure

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7
Q

What is complementary bases pairing?

A

Specific bases pair with specific bases i.e. purine must pair with pyrimidines due to complementary shape.

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8
Q

Which bases are complemenatry to each other?

A

A with T
C with G
A with U (RNA only)

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9
Q

How does the structure of DNA relate to its function?

A

1) Info storage = sequence of base pairs stores info to build proteins.
2) Long molecule = means that lots of info can be stored.
3) Base pairing rule = complementary strands can be replicated giving exact copies.
4) double helix, anti-parallel strand = very stable, essential for important molecules.
5) H bonds = easily unzipped for semi-conservative replication.

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10
Q

Where is almost all DNA found in eukaryotic cells?

A

Nucleus

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11
Q

How are nucleotides joined together?

A

Condensation reactions between the deoxyribose sugar and the phophate of another nucleotide.
From 5’ to 3’

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12
Q

Name of covalent bond that forms in a condensation reaction between nucelotides?

A

Phosphodiester bond

Forms sugar-phosphate backbone

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13
Q

Define the term anti-parallel

A

2 strands of DNA run in the opposite direction to one another

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14
Q

How are strands held together between bases?

A

Hydrogen bonds

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15
Q

How many H bonds between complementary bases?

A

2 H bonds between A and T

3 H bonds between C and G

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16
Q

What is the benefit of having H bonds between bases?

A

Allow the DNA molecule to easily unzip for DNA replication. Makes the molecule very stable and protects the base sequences

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17
Q

Differences between DNA and RNA

A

RNA is a single strand - DNA a double strand
RNA contains uracil instead of thymine
RNA has a ribose sugar instead of deoxyribose

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18
Q

What are the 3 types of RNA?

A

mRNA, rRNA, tRNA

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19
Q

Describe mRNA

A

Long single strand formed into a helix
Made in the nucleus
Passes into cytoplasm via nuclear pores
Moves to ribsomes for translation

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20
Q

Describe rRNA

A

Made in nucleolus
Found in cytoplasm
Forms in ribosomes
Ribosomes formed of rRNA and proteins

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21
Q

Describe tRNA

A

Forms clover-leaf shape
One end attaches to a specific amino acid
Other end has a triplet of bases used in protein synthesis known as an anticodon

22
Q

Describe the process of DNA extraction

A

Grind smaple in a mortar and pestle to break down the cell wall
Mix sample with detergent to break down the plasma membrane, releasing cell contents into solution
Add salt to break the H bonds between DNA and water molecules
Add protease enzyme to break down the proteins assciated with the DNA in the nuclei
Add a layer of cold ethanol causing the DNA to precipitate out of solution

23
Q

Why shoule the temperature be kept low throughout the extraction of DNA?

A

Reduce the activity of enzymes, which would break down the DNA and prevent extraction

24
Q

Why does the detergent break down the plasma membrane?

A

Disrupts the membrane structure making it more permeable and fluid, causing the phospholipids to form a suspension in the aqueous solution

25
Q

Why do cells require energy?

A

1) Synthesis = large molecules like proteins
2) Transport = molecules or ions across plasma membrane by active transport
3) Movement = protein fibres in muscle cells for contraction

26
Q

How is energy supplied to cells?

A

Adenosine triphosphate (ATP) supplies energy

27
Q

Components of ATP

A

Ribose sugar
Adenine base
3 phosphate groups

28
Q

What is ATP also known as for all living things?

A

Universal energy currency

29
Q

What type of reaction is the removal of a phosphate group in ATP?

A

Hydrolysis

30
Q

What are hydrolysis reactions of ATP said to be?

A

Couple. Happen simultaneously in association with an energy requiring reaction

31
Q

What is the negative of ATP?

A

The insatbility of the phosphate bond means its not a good long-term energy store.

32
Q

How is ATP formed?

A

The breakdown of fats and carbohydrates by cellular respiration. A phosphate group is reattached to the ADP molecule to reform ATP

33
Q

What is the process of forming ATP from ADP known as? What type of reaction is it?

A

Phosphorylation

Condensation reaction

34
Q

What type of energy store is ATP good for?

A

Immediate energy store as it is not needed as a large store

35
Q

How do the properties of ATP relate to its function?

A

1) Small = moves easily in and out of cells
2) Soluble = energy requiring processes happenin aqueous environments
3) Bonds between phosphates = large enough to provide immediate energy for cellular reactions, but not so large to waste energy as heat
4) Release energy is small quantities = energy not wasted as heat
5) Easily regenerated = recharged with energy

36
Q

When does DNA replication occur?

A

During interphase

37
Q

Describe the process of DNA replication

A

1) 2 strands of DNA must unwind (using gyrase) and split apart
2) H bonds are broken using DNA helicase, exposing bases
3) Free nucleotides line up against DNA strands. Nucelotides activated by extra phosphate groups using complementary base pairing
4) This occurs in the 5’ to 3’ direction (leading strand) using DNA polymerase
5) The lagging strand (3’ to 5’) uses primers and Okazaki fragments with DNA polymerase
6) DNA polymerase joins the 2 strands together forming 2 new DNA molecules
7) Ligase adds H bonds between bases

38
Q

Define semi-conservative replication

A

Molecules have one original strand and one new strand

39
Q

Define gene

A

A length of DNA which codes for one polypeptide or a length or RNA that helps regulate gene expression

40
Q

Define locus

A

Location of a gene on a chromosome

41
Q

Define allele

A

An alternative form of gene

42
Q

Define triplets

A

3 DNA bases code for 1 amino acid

43
Q

Define degenerate code

A

Most amino acids have more than one codon that can code for them. This can reduce the impact of point mutation

44
Q

Define universal

A

The tripet code TCG codes for the amino aicd serine in almost all organisms. There are some variations, a strong case for common ancestry.
All organims use thr same code, but sequences of bases coding for each individual protein will be different

45
Q

Define non-overlapping

A

Read starting from a fixed point in groups of 3 bases (codon)

46
Q

How does DNA control all metabolic activities in cells?

A

Chemical reactions control the cells activities
All chemical/metabolic reactions are catalysed bby enzymes
Enzymes are proteins
Sequence of bases of DNA codes for polypetide and protein molecules.
Hence DNA controls metabolic activities

47
Q

What are the 2 stages of ptrotein synthesis?

A

Transcription and translation

48
Q

Initiation in transcription

A

RNA polymerase binds to DNA at promoter region
Unwinding of DNA due to helicase
H bonds broken between bases and bases exposed

49
Q

Elongation in transcription

A

Free RNA nucleotides pair up with exposed complementary bases on template (anti-sense) strand in 5’ to 3’ direction
Added using RNA polymerase
Coding strand (sense strand) not transcribed

50
Q

Termination in transcription

A

Stops at the end of a gene
Stop codon produced on mRNA
H bonds catalysed by RNA polymerase, before detaching
Phosphodiester bonds form in a condensation reaction.
mRNA levaes the nucleus via the buclear pores into the cytoplasm

51
Q

Describe translation

A

mRNA binds to a ribsome in the cytoplasm or RER
Ribosome reads sequences of bases in the 5’ to 3’ direction until start codon of AUG
tRNA carrying amino acid methionine is complementary to codon on mRNA and will bind
Temp H bonds form
Each tRNA molecule carries a specific amino acid. One codon is read at a time
Peptide forms between amino acids (condensation) with peptidyl transferase catalysing
Stop codon found and polypeptide chain released and translation ends

Crypt A level Biology (8 decks)

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