Bacteria
Describe what happens in the lag, log, stationary, and death phase of bacteria grown in culture.
Lag phase - bacterial cells getting acclimated to their environment, metabolically active, no increase of the number of cells in the population.
Log Phase- exponential growth of bacterial cells, nutrients are abundant
Stationary Phase - death rate = reproduction rate due to nutrient deprivation, lack of oxygen, changes in pH, waste buildup
Death phase - death rate is greater than reproduction rate due to limiting factors in the environment
describe the fluid mosaic model of the cell membrane
Made of lipids and proteins that move around
For these items select either passive, active, or bulk transport
1. Does not require energy
2. Molecules move from high concentration to low concentration.
3. Molecules move from low concentration to high concentration.
4. Sodium/Potassium Pump is an example
5. Endo/Exocytosis
6. Facilitated Diffusion
1.Passive
2. Passive
3. Active
4. Active
5, Bulk
6. Passive
Cells hypertonic, cell will swell and gain water.
Describe what the signal sequence is composed of and what is the purpose of the signal sequence
20 hydrophobic amino acids, of a protein has this it will be translated on a bound ribosome
Describe three structures and their functions that are unique in bacteria
1. Pilli and/or fimbriae - short- hair like extensions outside the cell that allow bacteria to adhere to surfaces
2. Nucleoid - region within the cytoplasm where DNA is stored
3. Capsule - located outside the cell wall made of complex carbohydrates that allow bacterial cells to adhere to surfaces and make bacteria more pathogenic by making it difficult to be phagocyted by macrophages
Describe three ways to increase the fluidity of a cell membrane.
decrease both cholesterol and saturated fatty acids, increase unsaturated fatty acids.
Compare and contrast simple diffusion and facilitated diffusion.
1. Both high to low, both no energy
2. Simple through phospholipid bilayer, small/non-polar molecules, facilitated through a transport protein large/polar molecules.
Where are peripheral proteins located and explain if they are polar or non-polar.
They are on the surface of the cell, and are polar.
Daily Double -What must happen to a polypeptide in the lumen of the rough ER and if these processes occur where does the protein go next.
Both N-linked glycosylation and chaperones help polypeptide chain to fold into a protein and if folded correctly will travel to the golgi.
1.Compare and contrast gram -positive and gram- negative bacteria
2. Explain how you perform gram staining and how does this allow you to distinguish gram-positive and gram- negative bacteria
1. Both made of peptidoglycan. In gram pos. there is a thick peptidoglycan layer outside the cell membrane. In gram neg. the peptidoglycan layer is thinner and is located between the outer and inner cell membrane, which is unique to gram neg. bacteria.
2. Cells are treated with crystal violet, which will cross both the cell wall and cell membrane and both gram positive and gram neg. will appear violet. Cells are then treated with iodine, which will cross both the cell wall and cell membrane and both gram positive and gram neg. and bind to the crystal violet. Cells are then treated with alcohol which will be able to only penetrate the thinner gram neg. cell wall and then enter across the cell membrane and wash away the crystal violet stain inside the cell. At this point gram positive will still appear violet, while gram neg will now be colorless. Safranin is then applied and gram positive will still appear violet, while gram negative will appear pink.
Describe in detail why both phospholipids and integral proteins are amphiphilic.
Have both polar and non-polar part. Phospholipid head is polar, fatty acid tail non-polar. Interior of integral protein non-polar, exterior polar.
Daily Double -Two differences between active and passive transport
1. Passive high to low, active low to high
2. Passive no energy, active needs energy from ATP
What are the six functions of cell membrane proteins and which of those functions are carried out by peripheral proteins and which ones are carried out by integral proteins.
1. Transport- only integral
2. Enzymes - both
3. Cell recognition - both
4. Cell Signaling - both
5. Anchor cell - both
6. Intercellular joining - both
1. What is the difference between a normal and mutant prion protein (location and secondary structure)
2. How does a mutant prion protein convert a normal prion protein into a mutant prion protein.
3. Describe how mutant prion proteins become toxic to neurons.
1. Normal prion protein is located on the cell membrane, mutant prion is located in the cytoplasm. Secondary structure of normal prion protein is alpha helix. secondary structure of mutant prion protein is B-sheet.
2. Mutant prion protein changes the secondary structure of the normal prion protein into a B-sheet thus converting the normal prion protein into a mutant prion protein.
3. Mutant prion protein forms toxic aggregates that will result in apoptosis of the neuron
Describe how endospores are formed and what is the function of endospores.
Endospores form under stress conditions such as nutrient deprivation , high temp, radiation. First step is DNA is replicated, and the replicated DNA is stretched and combined to form an axial filament, a furrow form called a septum, two sides of the cell become more distinct with a forespore forming on the left side, forespore engulfed by mother cell, and mother cell DNA is degraded. cortex made of peptidoglycan is formed outside of the cell wall of the forespore, mature spore will burst out of the mother cell and will germinate when environmental conditions become favorable.
Explain the differences between phagocytosis, pinocytosis, and receptor- mediated endocytosis.
Phagocytosis transport large solid molecules such as bacteria, polysaccharides, proteins. Pinocytosis transports bulk liquids, receptor-mediated endocytosis transport viruses by specific interaction between receptor on host cell and spike protein on virus.
Describe in detail gap junctions, tight junctions, plasmodesmata
1. Gap Junctions- in animal cells allow for the exchange of materials
2. Tight Junctions - in animal cells, seals cells
3. Plasmodesmata - plant cells allow for the exchange of materials
Give an example of antiporter pump and an example of a symporter pump.
Antiporter- Na+/K+ pump
Symporter - H+/sucrose pump, Na+/glucose pump
1. What is the difference at the genetic level between the normal and mutant huntington gene.
2. What does CAG code for
3. Explain why the mutant huntingtin protein tends to form aggregates and why these aggregates are toxic to the cell.
1.Normal huntington gene has less then 35 CAG repeats, mutated one has 35 or more
2. CAG codes for glutamine
3. Proteins with poly-glutamine stretches tend to have a rich B-sheet secondary structure which tend form aggregates. These aggregates are toxic to cells because they tend to sequester other proteins that are required for the normal homeostasis of the cell, therefore this will lead to apoptosis.
1. Describe five ways antibiotics kill bacteria
2. Describe five ways bacteria become resistant to antibiotics.
Question 1
1.Inhibition of cell wall synthesis
2.Breakdown of the cell membrane structure or function
3.Interference with functions of DNA and RNA
4.Inhibition of protein synthesis
5.Blockage of key metabolic pathways
Question 2
1. Drug inactivation
2. Decreased permeability
3. Drug is pumped out of the cell
4. Change in binding site
5. Use an alternative pathway
Describe in detail how the H+/sucrose transporter works.
Using energy from ATP, proton pump, pumps protons out of the cell (low to high ), creating an electrochemical gradient. The H+/sucrose transporter moves sucrose into the cell (low to high) using energy from electrochemical gradient powered by the proton pump as protons travel back into the cell from high to low conc.
Describe in detail how the Na+/glucose transporter works.
Na+/K+ pump, using energy from ATP pumps 3 Na+ out out of cell (low to high) and pumps two K+ into cell (low to high) creating an electrochemical gradient (+ outside, - inside) that provides energy to move glucose into the cell (low to high ) powered as energy is released ( generated from electrochemical gradient created by Na+/K+ pump) as Na+ moves into cell from high to low.
Describe in detail how the Na+/K+ pump works.
Na+/K+ pump, using energy from ATP pumps 3 Na+ out out of cell (low to high) and pumps two K+ into cell (low to high) creating an electrochemical gradient (+ outside, - inside).
1. What must happen to a polypeptide in the lumen of the rough ER and if these processes occur where does the protein go next.
2. If these processes can not occur properly what are the two possibilities of the protein?
1. Both N-linked glycosylation and chaperones help polypeptide chain to fold into a protein and if folded correctly will travel to the golgi.
2. Degraded by the proteosome, or protein will form aggregates.