Cell biology Flashcards
What are the types of proteins that don’t finish translation in the cytosol (finish in rough ER)?
1) Secreted protein
2) Transmembrane protein
3) Lysosomal protein
4) ER/Golgi resident proteins
What do proteins that finish their translation in the rough ER have?
A signal sequence
Where does transcription occur?
Nucleus
Where does translation begin?
Cytosol
What proteins finish translation in the cytosol?
Cytosolic proteins
Information on the signal sequences in secreted proteins or lysosomal proteins?
1) Signal is first few amino acids translated
2) Signal is removed upon completion of translation
Information on the signal sequences in membrane bound proteins?
1) Signal can be anywhere in the amino acid sequence of the protein
2) Signal can appear several times
3) Signal is not removed but remains as part of the transmembrane protein
Steps for protein translation of a secreted protein
1) Ribosome with protein docks on docking site
2) signal recognition particle goes through the translocator pore and docks the protein in the ER lumen
3) Protein keeps being translated and gets pushed into the lumen
4) Signal sequence is clipped and the protein is put into a vesicle and transported to a specified location.
What are components of the cell membrane?
1) Phospholipids
2) Cholesterol: increases fluidity and stabilizes membrane
3) Proteins: channels
4) Carbohydrates: cell surface markers (glycoproteins, glycolipids)
What is a van’t hoff factor
Number of ions produced as a result of dissolving ionic substance
Eg: NaCl = Na and Cl = 2 van’t hoff factor.
Eg: CaCl2 = Ca and 2Cl = 3 van’t hoff factor
What are the four colligative properties?
1) Freezing point
2) Vapor pressure
3) Boiling point
4) Osmotic pressure
Which colligative go down when number of solute particles increase?
Freezing point and vapor pressure
Which colligative go up when number of solute particles increase?
Boiling point and osmotic pressure
What is freezing point depression equation?
Tf = -kf * i * m
What is the boiling point elevation equation?
Tb = kb * i * m
What is the equation for osmotic pressure elevation equation?
i * m * r * t
What is diffusion?
Movement of particles down a gradient
What is osmosis?
Movement of water down a gradient
Hypertonic vs Hyoptonic solutions
More particles vs less particles
What is isotonic?
Same number of particles (equilibrium)
What is osmotic pressure?
The pressure needed to resist/stop osmosis (movement of water)
Types of passive transport?
1) Simple diffusion
2) Facilitated diffusion
What is simple diffusion?
Molecules moves according to gradient. Works well for small hydrophobic molecules
What is facilitated diffusion?
Needs a helper protein because they are small hydrophilic molecules
What are pores?
Non-specific holes in the membrane
What are channels?
Highly-specific holes in the membrane
What are porters?
No holes. Undergo conformational change to move molecules across membrane.
Uni-porter = move one molecule
Co-transport = anti and symporter
1) Antiporter: Molecules in different direction
2) Symporter: Molecules in same direction
What is active transport?
Movement of molecules against gradient using energy
Two types of active transport?
1) Primary = use of ATP directly
2) Secondary = uses ATP indirectly
What is Na/K pump (primary active transport)?
3 Na out and 2 K in.
1) Maintains osmotic balance
2) Establishes electrical gradient
3) Sets up sodium gradient for secondary active transport
What is glucose/Na co-transporter (secondary active transport)
Na and glucose bind to a co-transporter which flips and lets glucose out
What is a G-protein linked receptor?
A receptor that binds a ligand causing GDP to fall off and GTP to bind. This activates the G-protein which stimulates adenlyl cyclase which makes cAMP. Increased cAMP leads to activation of cAMP-dependent protein kinases which phosphorylate enzymes which then changes enzyme activity.
What is an example of a second messenger?
cAMP
What are the three types of filaments?
1) Microtubules
2) Microfilaments
3) Intermediate filaments
What proteins make up microtubules?
Alpha and beta tubulin
What are uses of microtubules?
Mitotic spindle, Cilia, flagella and intracellular transport
What proteins make up microfilaments?
Actin
What are uses of microfilaments?
Muscle contraction, pseudopod formation and cytokinesis
What are uses of intermediate filaments?
Structural
What are desmosomes?
General adhesive junctions
What are tight junctions?
They are barriers that stop molecules from moving in between cells.
What are gap junctions?
They are like tunnels that are shared between two cells. Allow movement of molecules from one cell to a neighboring cell. They allow cell to cell communication
G1 vs G2 in cell cycle
Both involve cell growth but G2 includes preparation for mitosis while G1 continues normal cell activity.
What does S phase in cell cycle involve?
Involves DNA replication and synthesis
What are the two categories of cancer causing genes?
1) Oncogenes
2) Tumor suppressor genes
What are caspases?
They are proteases that mediate apoptosis
What are initiator caspases?
Activates in response to intracellular or extracellular signals
What are effector caspases?
Activated by initiators to carry out process of apoptosis
