Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology > DNA,RNA and protein synthesis > Flashcards

DNA,RNA and protein synthesis Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Nucleotides

A

Consist of 3 parts:
- A five carbon sugar molecule called a
PENTOSE SUGAR.
- A nitrogen-containing molecule called a
BASE.
- Negatively charge PHOSPHATE GROUP.

  • The covalent bond between the sugar and the phosphate group is also called a PHOSPHODIESTER BOND.

Contain the ELEMENTS:
- Carbon
-Hydrogen
- Oxygen
- Nitrogen
- Phosphorus

  • Used to make both the molecules DNA and RNA.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Polynucleotide

A

A PHOSPHODIESTER BOND is formed between:
- PHOSPHATE GROUP of nucleotide
- The HYDROXYL GROUP on carbon 2 of the pentose sugar of the other nucleotide.

Water is released ~ CONDENSATION reaction.

  • The molecule we have formed between TWO nucleotides is called a DINUCLEOTIDE
  • If we continue to add nucleotides by forming phosphodiester bonds we will form a polymer of nucleotides known as a POLYNUCLEOTIDE.
  • Both DNA and RNA are examples of polynucleotides.
  • We can BREAK the phosphodiester bond by adding back water known as a HYDROLYSIS reaction.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

DNA & its structure

A

A nucleic acid and one of the important MACROMOLECULES that make up the structure of living organisms.

  • consists of two POLYNUCLEOTIDE strands which twist around each other to form a DOUBLE HELIX.
  • A SUGAR-PHOSPHATE BACKBONE on the outside with the BASES in the centre.
  • the two polynucleotide strands are held together by HYDROGEN BONDS , which form between the bases on opposite strands.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

COMPLEMENTARY bases

A
  • The bases on one strand are complementary to the bases on the other strand.
  • GUANINE on one strand always pairs with CYSTOSINE on the opposite strand.
  • ADENINE always pair with THYMINE.
  • This complementary base pairing is CENTRAL to how DNA functions.
  • A PURINE (two rings) base always pairs with a PYRAMIDINE (one ring) base on the opposite strand.
  • This means the DISTANCE between the sugar phosphate backbones is CONSTANT all down the DNA molecule.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does it mean that the two polynucleotide strands in DNA are ANTIPARALLEL?

A
  • They run in OPPOSITE directions.

ONE STRAND:
- The top phosphate group will be attached to carbon 5 of the deoxyribose sugar.

  • At the bottom , the hydroxyl group will be attached to carbon 3.

OTHER STRAND:
- The carbon 3 hydroxyl group is at the top.

  • At the bottom we have the carbon 5 attached to the phosphate group.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

The number of HYDROGEN BONDS formed between complementary pairs and the PROPORTIONS of different nucleotides.

A

GUANINE & CYSTOSINE ~ 3
ADENINE & THYMINE ~ 2

  • Because of complementary base pairing, the proportion of G & C are always the same and the proportions of A&T are always the same.
  • This means we can calculate the proportions of different nucleotides.
  • Proportions of a base can change in different species due to different :
  • proteins
  • genes
  • DNA bae sequences
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

DNA nucleotides

A
  • the pentose sugar is called DEOXYRIBOSE which has one fewer OXYGEN atoms than ribose.
  • LONG polynucleotide chain
  • FOUR different bases ~ adenine , cytosine guanine and THYMINE.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

RNA nucleotides

A
  • Have the pentose sugar RIBOSE
  • SHORT polynucleotide chain.
  • FOUR different bases ~ adenine , guanine , cytosine and URACIL.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Differences in DNA and RNA
(not already mentioned)

A

DNA:
- Found in CHROMOSOMES in the nucleus
- TWO polynucleotide strands in a double helix.

RNA:
- Found in the CYTOPLASM where it plays a key role in protein synthesis.
- ONE polynucleotide strand.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

DNA replication STEPS

A

GYRASE ~ Unwinds the DNA

HELICASE :
- This enzyme attaches to the DNA molecule.

  • Causes the hydrogen bonds between complementary bases to BREAK.

-This causes the two polynucleotide strands to separate from one another.

  • Both strands act as a TEMPLATE
  • The ACTIVATED nucleotides (contain 3 phosphate group rather than one) now line up with their complementary bases on the DNA strands and are held in place by HYDROGEN BONDS only.

DNA POLYMERASE:
- This enzyme now attaches to the DNA molecule.

  • Moves down the molecule and catalyses the formation of a PHOSPHODIESTER bond between the activated nucleotides.
  • This is an example of a CONDENSATION reaction.
  • The activated nucleotides now lose their EXTRA TWO phosphate groups which leave and provide ENERGY for the reaction.
  • We have now got TWO copies of our double stranded DNA molecule.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Mutations

A
  • Sometimes an INCORRECT BASE is inserted into the growing polynucleotide strand.
  • This means the DNA sequence has CHANGED.
  • This is called a MUTATION which are RANDOM and occur SPONTANEOUSLY.
  • Can have very SERIOUS EFFECTS on the organism.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

TRANSLATION in 8 steps

A
  1. Once the mRNA moves from the nucleus into the cytoplasm, the small subunit of a ribosome binds with the mRNA at the START CODON.
  2. A tRNA molecule with an ANTICODON complementary to the start codon attaches.
    The tRNA delivers 1 SPECIFIC amino acid.
    This is held in place by HYDROGEN BONDS between the complementary base pairs on the mRNA and tRNA.
  3. Now a second tRNA molecule moves into place.
    The anticodon on this tRNA is complementary to the second codon on the mRNA.
  4. A PEPTIDE BOND is formed between the two amino acids using energy provided by ATP.
    This is catalysed by the enzyme peptidyl transferase which is part of the rRNA.
  5. Now the ribosome moves to the next codon and forms a peptide bond to the next amino acid.
  6. The first tRNA molecule is released and later attaches to their amino acid by enzymes in the CYTOPLASM.
  7. The ribosome continues moving down the mRNA forming the POLYPEPTIDE.
  8. When the ribosome comes to a STOP CODON , it DETATCHES and the polypeptide chain is released.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

mRNA nucleotides

A
  • The nucleotide sequence of the mRNA is used to determine the amino acid sequence of the polypeptide.
  • the mRNA nucleotides are read as a series of TRIPLETS known as the GENETIC CODE.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

tRNA

A
  • TRANSFER RNA
  • Single stranded
  • Clover shaped
  • Larger than mRNA
  • TOP of molecule is a BINDING SITE for an amino acid.
  • BOTTOM is a TRIPLET of bases called the ANTICODON.
  • The anticodon is COMPLEMENTARY to the triplet of bases in the mRNA called the CODON for that amino acid.
  • Many amino aids are encoded by SEVERAL triplets , each one of these will have a corresponding tRNA.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

3 featured of the genetic code

A
  1. DEGENERATE ~ most amino acids have more than one triplet, usually FOUR.
  2. NON-OVERLAPPING ~ no base is read more than once.
  3. UNIVERSAL ~ the same triplets encode the same amino acids in the vast majority of organisms on planet earth.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

START & STOP triplets

A

START ~ determine where to start translating the mRNA molecule.

STOP ~ determines where translation stops.

17
Q

Why can a large number of polypeptide molecules be produced rapidly?

A
  • Once the first ribosome has started moving along, another ribosome can attach to the start codon and begin translating.
  • This may cause a whole line of ribosomes making their way along the mRNA, allowing the process to occur quickly.
18
Q

DNA in PROKARYOTES

A
  • Circular DNA with no free ends.
  • Relatively short
  • Not bound to histones
19
Q

DNA in EUKARYOTES

A

In the NUCLEUS:
- Linear DNA with two ends.
- Much longer
- Tightly wrapped around histone proteins.

Also find DNA in the MITOCHONDRIA & CHLOROPLASTS:
- This DNA is very similar to the DNA found in prokaryotes.
- Relatively short, circular and not attached to histones.

20
Q

How do chromosomes become VISIBLE in the cell?

A
  • In the nucleus of a eukaryotic cell, the dark material is the DNA bound to histones.
  • It is not possible to see any distinct chromosomes because at this stage, the chromosomes have a relatively OPEN STRUCTURE.
  • At this point, we refer to the DNA and histones as CHROMATIN.
  • Before a cell divides, all of the chromosomes are COPIED.
  • These two copies remain attached at a point called the CENTROMERE.
  • Now the DNA molecules are called CHROMATIDS.
  • At this stage we refer to the entire structure as a CHROMOSOME.
  • The chromosomes CONDENSE , the DNA and histones form densely packed loops and coils.
  • The chromosomes are now VISIBLE in the cell.
21
Q

Homologous Chromosome

A
  • In human cells, we find 46 chromosomes,
    23 from father and 23 from mother.
  • This is called HOMOLOGOUS CHROMOSOME PAIRS.
  • The two chromosomes in a homologous pair have the SAME GENES.
  • The POSITION of a gene on a
    chromosome is called the LOCUS for that
    gene.
22
Q

Why is DNA replication a SEMI-CONSERVTIVE replication?

A
  • The DNA double helix separates into TWO polynucleotide strands.
  • Each strand is then REPLICATED into a complementary NEW strand.
  • So at the end, ONE molecule of DNA has been copied into TWO molecules of DNA.
  • Each of the two copies contains one strand from the ORIGINAL DNA molecule and one NEW strand.
23
Q

What if DNA replicated CONSERVATIVELY?

A

This would produce:
- One molecule of DNA containing TWO ORIGINAL strands.
- One molecule of DNA containing TWO NEW strands.

ONE ROUND OF REPLICATION :
- One DNA molecule containing only nitrogen-15 .
- One DNA molecule containing only nitrogen-14.

TWO ROUNDS OF REPLICATION:
- One DNA molecule containing only nitrogen-15.
- THREE DNA molecules containing only nitrogen -14.

This means we would have NO DNA molecules containing BOTH nitrogen-14 and nitrogen-15.

24
Q

Which ELEMENT was used to test that DNA replicated semi-conservatively?

A

NITROGEN:
- All the bases in DNA contain the element nitrogen which exists in two main forms or isotopes:
- Nitrogen-14 (lighter)
- Nitrogen-15 (heavier)

  • Due to their difference in MASSES , they form a BAND in different positions .
25
Q

How scientists SHOWED that DNA replicates semi-conservatively - STEP 1

A
  • Took a sample of BACTERIA .
  • Under normal conditions , almost all of the NITROGEN atoms in the DNA of these bacteria will be N-14 (lighter)
  • EXTRACTED the DNA , placed in a SOLUTION, and spun this at very high speeds in a CENTRIFUGE.

-The DNA moved down the solution and formed a BAND which the scientists could detect.

  • As it mostly contained the lighter isotope, the band formed near the TOP of the tube.
26
Q

How scientists SHOWED that DNA replicates semi-conservatively - STEP 2

A
  • Next the scientist cultured the bacteria in a growth medium which only contained NITROGEN-15.
  • After the bacteria had REPRODUCED many times, almost all the nitrogen atoms in the DNA were N-15.
  • When this DNA was extracted and centrifuged , it formed a band near the BOTTOM due to be the HEAVIER isotope.
27
Q

How scientists SHOWED that DNA replicates semi-conservatively - STEP 3

A
  • The scientist took a sample of the bacteria which had been growing on NITROGEN-15.
  • TRANSFERRED these bacteria to a NITROGEN-14 and allowed them to REPLICATE their DNA only ONCE.
  • DNA was EXTRACTED and spun in a CENTRIFUGE.
  • This DNA produced a band IN BETWEEN the two bands produced before.
  • This shows that this DNA contained one strand with NITROGEN-14 and one strand with NITROGEN-15.
  • This means that DNA must have replicated SEMI-CONSERVATIVELY.
28
Q

What happened when the scientist allowed the bacteria to replicate one more time on NITROGEN-14?

A

It produced a band pattern:
- One band~ same position as the band shown when DNA has replicated once.

  • Second band~ same position as the band shown with only NITROGEN-14.

This is because the second round of replication produces FOUR DNA molecules:

  • TWO contain a strand with N-14 and a strand with N-15.
  • TWO both contain two strands with only N-14.
29
Q

Why is ATP needed?

A
  • Carbohydrates and triglycerides are used as LONG-TERM storage molecules.
  • For example, the molecule GLYCOGEN can be hydrolysed to produce GLUCOSE.
  • This glucose can then be used as a source of energy through respiration.
  • PROBLEM~ glucose contains a great deal of stored energy , much more than would ever be required by any single process in the cell.
  • This means that cells need a way to transfer the energy from the glucose molecule , into SMALLER & USEFUL amounts.
  • To do this, cells use the molecule ADENOSINE TRIPHOSPHATE (ATP).

-The energy released in the aerobic respiration of ONE glucose molecule can be transferred to over THIRTY molecules of ATP

  • Also PHOSPHORYLATES molecules to make them more REACTIVE.
30
Q

What is ATP ?

A

ATP:
- A nucleotide
- Acts as an IMMEDIATE energy source
- Transfers energy from the site of RESPIRATION , to the parts of the cell which require energy.

Processes that require this energy:
- Active transport
-Muscle contraction
- Formation of larger molecules such as proteins.

31
Q

The STRUCTURE of ATP

A
  • Contains the base ADENINE bonded to the pentose sugar RIBOSE.
  • Together this part of the molecule is called ADENOSINE.
  • On the other side of the ribose there are THREE PHOSPHATE GROUPS.
  • It only takes a SMALL AMOUNT of energy to break the covalent bond holding the last phosphate group in place.
  • But when this bond is broken, a GREAT DEAL OF ENERGY is released.
  • Breaking this bond requires a water molecule so is a HYDROLYSIS REACTION.
  • This energy can then be used by processes in the cell.
32
Q

GENE

A

A length of DNA that codes for a polypeptide or for a length of RNA that is involved in regulating gene expression.

  • Within each gene , there is a sequence of DNA BASE TRIPLETS that determines the amino acid sequence , or primary structure of a polypeptide.
  • Some do NOT encode for polypeptides but instead functional RNA molecules such as TRANSFER RNA (tRNA) and RIBOSOMAL RNA ( rRNA)
33
Q

TRANSCRIPTION

A

The process of DNA being copied into mRNA.

  • The enzyme RNA POLYMERASE joins the RNA nucleotides by forming PHOSPHODIESTER BONDS.
  • These nucleotides line up by complementary base pairing, A-T,C-G,A-U.
  • The enzymes continue making their way along the DNA until they reach the end of a gene.
  • The mRNA has now been SYNTHESISED and the RNA polymerase DETATCHES from the DNA and the DNA goes back to its normal double helix structure.
  • The mRNA now moves out of the nucleus through a NUCLEAR PORE ,where it enters the cytoplasm, ready to take part in TRANSLATION.
34
Q

RNA splicing

A

Converts the pre-mRNA into FUNCTIONAL mRNA.

  • Non-coding and coding regions DNA are found both between and within GENES.

Non-coding regions ~ INTRONS
Coding regions ~ EXONS

  • In humans , many genes contain a large number of INTRONS.
  • During transcription, both EXONS and INTRONS are copied into RNA.
  • This means RNA contains non-coding regions called PRE -mRNA.
  • Once the pre-mRNA is formed , the INTRONS on then REMOVED and the ends of the EXONS connected ( splicing).
  • This process does not take place in PROKARYOTES as INTRONS are UNCOMMON.

Biology (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions