Lecture 2 Flashcards
What makes up the primary structure of a protein?
the sequence of amino acids linked together to form a polypeptide chain
What is electrostatic attraction?
between negative and positive charged groups
If proteins can’t self organize, what helps them?
Chaperone proteins or isolation chambers
Example of a post-translational modification
Phosphorylation
Process of phosphorylation
A kinase transfers a phosphate from ATP - phosphate dephosphorylates
Explain the process of breaking open cells and tissues
- Disrupt tissues and cells
- Using homogenization, plasma membrane of cells can be ruptured (cell contents released)
Centrifuge process
Homogeneate is placed in test tubes and rotated at high speed in a centrifuge
Different centrifugation process
Progressively higher speeds will fractionate cell homogenates into components
Gel Electrophoresis process
An electric field is applied to a solution containing protein molecules, proteins migrate in a direction and at a speed that reflects their size & net charge
What do the 2 lipid sheets of cell membranes do?
They prevent molecules on one side from freely mixing with the other
Act as selective barriers
What are cell membranes composed of?
- Phospholipid bilayer
- Other lipids
- Embedded proteins
- Associated carbohydrates
What vital functions are cell membranes apart of?
- Communication with the environment
- Import and export of material
- Flexibility for growth and movement
What different types of membrane lipids are amphipathic?
- Phospholipids
- Sterols
- Glycolipids
What are phospholipids made of?
- A polar head
- Two nonpolar hydrocarbon chains for the tail
- A molecule of glycerol
When do small spherical liposomes form?
When pure phospholipids are added to an aqueous environment
Explain fluorescence recovery after photobleaching
Bleach patch with laser beam, labeled proteins diffuse throughout membrane, fluorescence returned to bleached patch
What is the density of phospholipids controlled by?
Hydrocarbon tail length, presence and number of double bonds, cholesterol
What do enzymes near the cytosolic surface use to deposit new phospholipids?
Free fatty acids
Flippases
Phospholipid-handling transporters - catalyzes transfer of specific phospholipids to cytosolic monolayer
True or false: Asymmetry is maintained as membranes move by a process of budding and fusing
True
What side chains do membrane-spanning segments have in integral proteins?
Hydrophobic side chains
What is the membrane stabilized by in animal cells?
a meshwork of filamentous proteins called the cell cortex
What maintains the distinctive flattened shape in red blood cells? What is this?
Spectrin - a dimeric protein that forms a lattice
What might protein movement be restricted by? (4)
- Attachment to the cortex
- Attachment to molecules outside the cell
- Cell junctions
- Diffusion barriers
