Central Dogma Flashcards
gene expression
The process by which the DNA instructions are converted into the functional product is called gene expression
Central dogma of molecular biology
the framework for the flow of genetic information within a biological system
DNA
- contains base triplets – sequence of 3 nucleotides
- double-stranded
- present in the nucleus
RNA
- contains codons
- singe stranded
- present in the nucleus and cytoplasm
Protein
- contains amino acids
- amino acid sequence
- present anywhere in the cell
Define Translation
Translation is the process where the information carried in mRNA molecules is used to create proteins. The specific sequence of nucleotides in the mRNA molecule provides the code for the production of a protein with a specific sequence of amino acids.
Much like how RNA is built from many nucleotides, a protein is formed from many amino acids. A chain of amino acids is called a ‘polypeptide chain’ and a polypeptide chain bends and folds on itself to form a protein.
During translation, the information of the strand of RNA is ‘translated’ from RNA language into polypeptide language i.e. the sequence of nucleotides is translated into a sequence of amino acids.
TRANSLATION OCCURS IN RIBOSOMES
Ribosomes are small cellular machines that control the production of proteins in cells. They are made from proteins and RNA molecules and provide a platform for mRNA molecules to couple with complimentary transfer RNA (tRNA) molecules.
Each tRNA molecule is bound to an amino acid and delivers the necessary amino acid to the ribosome. The tRNA molecules bind to the complementary bases of the mRNA molecule.
Define Transcription
Transcription is the process in which a gene’s DNA sequence is copied (transcribed) to make an RNA molecule.
RNA polymerase is the main transcription enzyme.
Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins).
RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule.
Transcription ends in a process called termination. Termination depends on sequences in the RNA, which signal that the transcript is finished.
The 3 stages in both transcription and translation are
Initiation
II. Elongation
III. Termination
Plasma membrane (PM): separates the interior of the cell from the outside environment. Structure and Function
Structure:
· Flexible, fluid (allows movement of proteins & lipids), selectively permeable
· Lipid bilayer – 2 parallel layers of molecules (75% phospholipids – polar, hydrophilic head & non-polar, hydrophobic tails; 20% cholesterol – interspersed among the other lipids; 5% glycolipids – appear only in membrane that faces the extracellular fluid)
· Contains proteins (integral – extend into or through PM [transmembrane]; peripheral – attached to lipid heads/ integral proteins at inner or outer membrane surface)
Function:
· Protection
· Regulate movement of substances in and out of cell
· Communication
” Question: Which molecules are the plasma membrane permeable and impermeable to?
Permeable to non-polar, uncharged molecules, steroids, 02, C02, NH3, come nutrients and wastes, some alcohols.
IMPERMEABLE TO ions, and large uncharged polar molecules (glucose)
SLIGHTLY PERMEABLE small uncharged polar molecules (water, urea)
” Question: What does the term amphipathic mean? Which structures in the plasma membrane are amphipathic?
Amphipathic is a word used to describe a chemical compound containing both polar (water-soluble) and nonpolar (not water-soluble) regions in its structure.
Phospholipids, Cholesterol and Glycolipids are amphipathic.
The proteins contained within the Permeable membrane differ from cell to cell. Membrane proteins have a variety of functions such as:
ion channel
Ø carrier
Ø receptor
Ø enzyme
Ø linker
Ø cell identity marker
