1.2 Proteins Flashcards
Proteome
The entire set of proteins expressed by a genome
Why is the proteome larger than the number of genes?
More than one protein can be expressed from a single gene due to alternative RNA splicing
Alternative RNA splicing?
Alternative RNA splicing is the removal of introns from the primary transcript. The remaining exons can be either included or removed to allow for several different possible proteins to be produced from one primary transcript
What factors can affect the set of proteins expressed by a given cell type?
- Metabolic activity of cell (changes with age, dormancy state etc.)
- Cellular stress (depends on extremes of temperature, pH, toxin exposure etc.)
- Response to signalling molecules such as hormones
- State of health or disease
Non-Coding RNA Genes
Genes that don’t code for proteins
Examples of non-coding RNA genes
Those that are transcribed to produce tRNA, rRNA and other RNA molecules that control expression of protein coding genes
Endoplasmic Reticulum
Forms a network of membrane tubules continuous with the nuclear membrane
Golgi Apparatus
Series of flattened membrane discs
Lysosomes
Membrane-bound organelles containing a variety of hydrolases that digest proteins, lipids, nucleic acids and carbohydrates
Vesicles
Transport materials between membrane compartments
Classes of R Group
Basic (positively charged), acidic (negatively charged), polar and hydrophobic
Primary Structure
The sequence in which the amino acids are synthesised into the
polypeptide
Prosthetic Group
A non-protein unit tightly bound to a protein and necessary for its function
What can interactions between R groups be influenced by?
Temperature and pH
Ligand
A substance that can bind to a protein
What increases the total membrane area in eukaryotes?
System of internal membranes
What is synthesised in the ER?
Lipids and Proteins
Types of Secondary Structure
Alpha helices, parallel or anti-parallel beta-pleated sheets, or turns
What causes secondary structure?
Hydrogen bonding along the backbone of the protein strand
Tertiary Structure
Tertiary structure is the folding of the polypeptide, stabilised by interactions between R groups such as LDFs, hydrophobic interactions, hydrogen bonding, disulfide bridges and ionic bonds
Where does quaternary structure exist?
Proteins with two or more connected polypeptide subunits
Ligand Binding (3 points)
- R groups not involved in protein folding can allow binding to ligands
- Binding sites have complementary shape to ligands
- When binding occurs, the protein changes conformation causing a functional change
ATPase
Hydrolyses ATP
Cooperativity
Process whereby binding of oxygen to one subunit of haemoglobin alters the affinity of remaining subunits
Kinase
Catalyses the transfer of a phosphate group to other proteins
Phosphatase
Catalyses the transfer of a phosphate group from other proteins
Haemoglobin’s Affinity for Oxygen
Increased with decreased temperature or increased pH
Decreased with increased temperature or decreased pH
