Introduction to Biochemistry
Biochemistry : a multidisciplinary science that explores the chemistry of living organisms and molecular basis for changes occurring in living cells. Principal areas of Biochemistry
1. Struture and Function of Biomolecules
Based on structure depend the function (structure function relationship) Example:
Hemoglobin S differs from regular adult hemoglobin (hemoglobin A) by just one single amino acid. A valine replaces a glutamine in the 6th position of the beta chain of globin.
e.g. krebs cycle, photosynthesis, respiration
3. Storage and transmission of genes
Branches that deals with it:
a. Bioinformatics -the application of computer science and information technology to the field of biology and medicine. Bioinformatics was applied in the creation and maintenance of a database to store biological information at the beginning of the "genomic revolution", such as nucleotide and amino acid sequences.
b. Bioenergetics – concerns with the energy flow through living systems. i. Endergonic – “inside” input of energy
ii. Exergonic – output of energy
Central Dogma of Molecular Biology
DNA replication – DNA to DNA
Transcription – DNA to RNA
Translation – RNA to protein
Reverse Transcription – RNA to DNA
Biochemistry encompasses organic chemistry, genetics, physiology (study of function), microbiology, medical research, nutrition, biophysics, cell biology. Cell
Fundamental and Structural unit of all organisms
Classification of cell:
1. Prokaryotic cell – (Greek: pro, before), which lack this organelle. 2. Eukaryotic cell – (Greek: eu, good or true _ karyon, kernel or nut), which have a membrane enclosed nucleus encapsulating their DNA (deoxyribonucleic acid)
Difference between a prokaryotic cell and a eukaryotic cell:
| All species that belong to Kingdom Monera.
| All other organisms that doesn’t belong to Kingdom Monera.
| ‘pro’ – before‘karyon’ - nucleus
| ‘eu’ – true
| Major Group
| Eubacteria – true bacteriaArchaebacteria – ancient class
| Cellular organization
| Multicellular (except unicellular Protist)
| Absence of ‘true’ nucleusNucleoid
| Presence of ‘true’ nucleus
| 0.2-5 μm in diameter
| 10-50 μm in diameter
* Prokaryotes are considered as ancestor of eukaryotic cell. * Only organisms in Kingdom Monera are prokaryotic cells. * Unicellular
* Escherichia coli is the most studied prokaryote
Two major divisions:
1. Archaebacteria (ancient class)
a. Acidophiles – can withstand low pH
b. Halophiles – can withstand gases
c. Thermophiles – can withstand temperature
d. Osmophiles – can withstand salt concentration
2. Eubacteria (true bacteria)
Structure of a prokaryotic cell:
* There are two definite membranes in a bacterial cell: the cell wall and the plasma membrane (cytoplasmic membrane). * Some bacteria further encase themselves in a gelatinous polysaccharide capsule that protects them from the defenses of higher organisms.
Parts of the membrane of bacterial cell:
1. Cell wall – outer layer membrane; it is rigid and serves as mechanical support. It is made up of polysaccharides, lipids and protein molecules. 2. Porin – acts as channels that allow diffusion of solutes. 3. Plasma membrane – the inner membrane; it is a lipoprotein structure which serves as molecular barrier. Some enzymes involved in respiratory chain and photosystems maybe present.
* Sandwich between the cell wall and plasma membrane is the periplasmatic space.
Figure : Periplasmatic space in gram positive gram negative bacteria.
1. Ribosomes – 20,000 to 30,000 ribosome particles are present in the cytoplasm. These are sites for protein...
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