1. DNA and the Production of Proteins
National 5 Biology
DNA and the Production of Proteins
Mr G Davidson

2. Variety of Protein Proteins are important molecules in biology.
They contain the elements Carbon, Hydrogen, Oxygen and Nitrogen.
They often contain Sulphur and Phosphorous.
Friday, 30 November 2018
G Davidson

3. Variety of Protein
Proteins are built from chains of amino acids, held together by peptide bonds forming polypeptides.
If the polypeptides form parallel strands, fibrous proteins are formed, and if they become tangled up to form a spherical shape, globular proteins are formed.
Friday, 30 November 2018
G Davidson

4. Variety of Protein
Proteins form many different parts of an organism and have many functions.
e.g. -enzymes, antibodies, structural, hormones, etc.
Friday, 30 November 2018
G Davidson

5. Structure of DNA
Cell proteins are built according to inherited information held in the nucleus, the information is packaged as chromosomes.
The chromosomes are made up of chains of molecules, called genes.
A gene is a unit of heredity and is composed of a complex substance called Deoxyribonucleic acid.
Friday, 30 November 2018
G Davidson

6. Structure of DNA
Friday, 30 November 2018
G Davidson

7. Structure of DNA Deoxyribose sugar Phosphate Friday, 30 November 2018
G Davidson

8. Structure of DNA The DNA molecule can be described as a double helix.
It is made up of two strands of sub-units called nucleotides.
Each nucleotide has 3 parts:
deoxyribose sugar
a base
phosphate 
Base
Deoxy-ribose sugar P
Friday, 30 November 2018
G Davidson

9. Structure of DNA
Cytosine P
Guanine
Adenine
Thymine
Deoxy-ribose
There are four different nucleotides, because there are four different bases.
The four bases are:
Cytosine
Guanine
Adenine
Thymine
Friday, 30 November 2018
G Davidson

10. Structure of DNA The molecule is held together in two different ways.
A strand is connected by strong bonds between the sugar and phosphate.
The strands are held together by weak hydrogen bonds connecting cytosine to guanine and adenine to thymine.
Friday, 30 November 2018
G Davidson

11. Protein Synthesis
The sequence of bases along a strand of DNA is anything but random.
The order of bases is called the genetic code.
The code is actually a ‘recipe’ for protein production.
Friday, 30 November 2018
G Davidson

12. Protein Synthesis
Proteins are chains of amino acids of which there are twenty in nature , so it follows that the DNA code should be able to specify at least 20 different items.
To do this, the bases of DNA are grouped in threes, these are called triplets of bases, each containing a triplet code for a specific amino acid.
Friday, 30 November 2018
G Davidson

13. Protein Synthesis
DNA occurs in the nucleus of a cell, and protein synthesis on the ribosomes in the cytoplasm, therefore something must happen which transfers information from one place to another.
The information contained in the DNA code has to be collected and taken out of the nucleus and this is done by another nucleic acid called Ribonucleic Acid (RNA).
Friday, 30 November 2018
G Davidson

14. Protein Synthesis It is similar to DNA except:
1. it is a single strand
2. it has a ribose rather than a deoxyribose sugar
3. the base Thymine is changed to the base Uracil
Friday, 30 November 2018
G Davidson

15. Protein Synthesis
During protein synthesis, the appropriate region of DNA temporarily opens up to expose the bases to produce a strand of mRNA which then leaves the nucleus through the pores.
Once the mRNA leaves the nucleus, it becomes attached to a ribosome.
Friday, 30 November 2018
G Davidson

16. Protein Synthesis
Friday, 30 November 2018
G Davidson