How is the structure of DNA adapted to its function ?
8
- double stranded =stable
- bases are on inside = protected , code is maintained
- molecules are long = store a lot of genetic information
- Hydrogen bonds = break for transcription and maintain shape
When does DNA replication occur ?
Interphase -
S phase
Outline DNA replication
(5)
5- main points
3- enzymes
1- unwinds (Gryase)
2- Unzips (Helicase)
3-free phosphorylated nucleotide in nucleoplasm bind to exposed bases
4- Bonding /joining of bases ( DNA Polymerase ) Semi conservative
5-Hydrolysis removes extra phosphate groups
Purines ?
Structure / 2bases
Have 2 rings ( hexose and pentose )
- Adenine
- Guanine
Pyrimidine ?
Structure / bases
1 hexose ring
- Cytosine
- Thymine / Uracil
How is the lagging strand synthesised in DNA replication?
Discontinuously
- enzyme Ligase joins it up later
What enzymes are involved in DNA replication and what is there function ?
6 marks
- Gryase - Catalyses unwinding of DNA
- Helicase - catalyses the breaking of hydrogen bonds between bases
- DNA Polymerase- cataclysms he addition of new nucleotides to both old strands
Why is DNA replication semi conservative?
- 2 new molecules contain an old strand and new strand
What organelles are involved in protein synthesis ?
1- ribosome
2-nucleus & and nucleolus
3-endoplasmic reticulum
4-mitochondria
What is the function of a ribosome ?
Catalyst - allows polypeptide to form by bringing amino acids close together
Where is MRNA made ?
Nucleus
Where are ribosomes made / how do they pass out ?
- made in nucleolus into 2 smaller subunits
- pass Out separately in 2 subunits
- Mg later bonds them together
Why are ribosomes thought of as catalysts ?
They are unchanged at the end of reaction
They allow amino acids close together to form polypeptides
Outline transcription ?
(4)
-strands
1- DNA unwinds :
There is a coding strand and a non coding strand
2- free nucleotides bond to non coding strand .
3 - template is made
4- template is same to Coding strand
This template is MRNA
- Thymine is replaced with Uracil
Outline translation
5
1-mRNA codons go to ribosome
2-TRNA brings anticodon / amino acids
3-Anticodons pair up with bases in mRNA temporarily
4- Amino acids are meanwhile forming the primary structure - joint by peptide bonds
5-competed protein folds up appropriately
What is a sequence of 3 bases Called in :
1- DNA
2-mRNA
3-tRNA
1- bass triplet
2-Codon
3-Anticodon
What’s transcription ?
Transcription is the process of making MRNA from DNA
What is translation ?
Translation is :
- formation of protein
- by assembling amino acids into particular sequence according to coded instructions given by mRNA from nucleus .
- at ribosomes
Function of mRNA
-carries instruction / template to the ribosomes for protein synthesis
Function of TRNA ?
tRNA brings anticodons to ribosome and hence amino acids forming the primary structure of a protein and polypeptide chain !
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Chapter 1 - Cell Structure33
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2.2 Biological Molecules28
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Nucleic Acids20
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Chapter 2.4 ENZYMES31
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Chapter 2.6 Cell Division ....42
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Biological Membranes37
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Exchange Surfaces And Breathing Chapter 3.136
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Chapter 3.2 Transport In Animals61
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Chapter 3.3 Transport In Plants42
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Chapter 4.1 Communicable Diseases57
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Chlater 4.2 Biodiversity24
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Chapter 4.3 Biological Classification35
