Cell Biology - AB1
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What is the size of an animal cell?
What is the size of a bacterium?
What is the main factor of resolution for microscopes?
Describe how green fluorescent protein can be used in fluorescence microscopy. (3 answers)
- All for live cells
- Insert gene into target cells, follow fate of cells (eg in embryo)
- - Attach gene to another gene (chimaera). Follow location
- - Attach gene to DNA regulatory sequence. Follow timing of expression
What methods can be used to make cells fluorescent?
- 1. Use of fluorescent ion chelators
- 2. Use of antibodies
- 3. Use green fluorescent protein
Describe how using antibodies can make a cell fluorescent.
- - Antigen with multiple epitopes (bumps)
- - primary antibody (rabbit vs antigen)
- - secondary antibody (goat vs rabbit) fluorescently tagged
What is the function of ribosomes?
- "Protein synthesis machines"
- (Composed of ribosomal RNA and protein subunits)
What are the characteristics and function of the nucleus?
- Diameter 5 - 10 microns
- Double membrane
- Carries most genomic information
- Site of RNA synthesis (transcription)
- Site of ribosome synthesis
What is heterochromatin and what does it mean?
- - Densely stained areas
- - tightly packed
- - low transcriptional activity
What is euchromatin and what does it mean?
- - light stained areas
- - loosely packed
- - high transcriptional activity
Where does protein synthesis start?
in the cytoplasm
What is the structure and function of the RER?
- - continuous with nuclear outer membrane
- - active ribosomes attached to membrane
What is the function of the transport vesicles?
Bud off ER and travel through the cytoplasm to the golgi apparatus
What are the different protein processing events that happen in the golgi?
- cis face: arrival of vesicles, protein phosphorylation
- medial golgi: addition of sugar residues
- trans face: proteolysis, sorting of lipids and proteins, vesicle release
What is the function of lysosomes?
- - contains hydrolase enzymes that break down macromolecules
- - pH of the lysosome is maintained at 5.
- the destructive enzymes are active only in an acidic environment
What are the types of filaments of the cytoskeletons?
- microfilaments (made of actin)
- intermediate filaments (variable protein composition depending on the tissue)
- microtubules (made of tubulin)
What is the structure and function of the mitochondrion?
- 0.5-2 microns
- variable number per cell depending on energy requirements
- small cicular genome
- double membrane
What are the kinds of covalent bonds?
- hydrogen bonds
- ionic bonds
- van der Waals attractions
What is a hydrogen bond?
- electropositive hydrogen is shared between 2 electronegative atoms
- very weak
- can form between backbone or side chain groups
- very short range
What is an ionic bond?
- electrostatic bonds or salt bridges
- formed between +ve and -ve charged amino acid side chains
- less strong on the surface of the molecule as water molecules cluster around the charged side chains
- very important in an environment protected from water
What is a van der Waals interaction?
caused by fluctuating electric charges around molecules
What is a hydrophobic effect?
hydrophobic amino acids are buried on the inside of the molecule, protected from interaction with polar water molecules
What are disulfide bonds?
covalent bonds formed by the oxidation of two cysteine residues. They stabilize the tertiary and/or quaternary structure of proteins.
What is the structure of a protein?
- primary structure - order of amino acids (covalent)
- secondary structure - alpha helices, beta pleated sheets (hydrogen bonds - weak bonds)
- tertiary structure - 3D structure (weak bonds)
- quaternary structure - multiple subunits (weak bonds)
What are the most abundant types of collagen and where are they located?
- Type I (composed of two alpha 1 and one alpha 2 genes) - located in tendon, bone and dermis
- Type IV - located in the basement membranes
What is the structure of collagen?
- Triple helix is formed by three alpha chains
- Repeating Gly-X-Y structure
- Essential that every 3rd residue is a Gly
What are the characteristics and function of membranes?
- 2 molecules thick
- hydrophobic interior
- self-organizing and self-healing
- serve to partition aqueous compartments
- permeable to water by not ions
What is a lipid bilayer composition?
What is entropy?
Degree of disorder
What is an exergonic reaction?
- Energy releasing
- -ve deltaG(change in free energy level)
What is an endergonic reaction?
- Energy requireming
- +ve deltaG (change in free energy level)
What value does a spontaneous process have for free energy change? (delta G)
What is the link in the body between energy yielding processes and energy requiring processes?
What is considered a proton donor?
What is considered a proton acceptor?
When is buffering effective?
at pH values +1 or -1 from a weak acids pKa
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