Quiz #1 Review Flashcards
Describe the ultra-structure of the mammalian cell stating the function(s) of the different levels of cell organization
Prokaryotic Lack of a nuclear envelope -nucleoid Generally smaller and simpler than eukaryotic cell Less complex genomes No organelles or cytoskeleton Complex cell wall Examples are Archaebacteria Eubacteria
Eukaryotic
Genome (genetic information) in organized nucleus
Highly organized cytoplasmic components called organelles.
Much more complex than the prokaryotic cell
Cytoskeleton is present.
Large cell volume
Complex protein transport system
Usually found in multicellular organisms.
Proteins form structural and functional components of the cell membrane. Discuss; stating how proteins are synthesized and what are their functions.
Integral proteins
Span the entire membrane
Peripheral proteins
Attached only on the periphery of the membrane
Amino acids of membrane proteins
Within membrane
Nonpolar AA (Gly, Ala, Val, Cys, Leu, Ile, Met, Phe, Trp, Pro)
Hydrophobic
On outer surface
Polar AA (Ser, Thr, Tyr, Asn, Gln)
Hydrophilic
List any three factors that regulate membrane fluidity. Explain how each factor operates.
Temperature:
Low temp- Thickens membrane, phospholipids clump together
High temp- Membrane is more flexible
Cholesterol
Near the head more rigid
In between the tails more flexible
Saturated fatty acids: less flexible, pack closer together
Unsaturated fatty acids: more flexible, don’t pack as close together
Longer = less kinks, more interactions therefore, stronger interactions
What is the function of membrane scramblase and how does its function affect the asymmetrical distribution of phospholipids in the cell membrane of eukaryotic
In the cell membrane, the asymmetrical distribution of phosphoglycerates maintains the architectural stability of the cell. The first step in apoptosis involves enzymes called scramblases to redistribute or disrupt this asymmetrical distribution.
List any four polar amino acids that form the hydrophilic and hydrophobic portions of the integral proteins of the cell membrane.
Serine, Tyrosine, Glutamine, Threonine, Asparagine
What is tubulin polymerization and how does it contribute to the development of cancer.
Microtubules can assemble and disassemble easily and quickly. Tubulin proteins polymerize to form microtubules. Microtubules have an alpha and beta subunit. They function similar to actin by providing mechanical support and mechanical activities for the cell. In mitosis the condensation of chromatin and the movement to opposite ends of the cell is possible due to microtubules. If a cell has a higher concentration of tubulin it will divide at a higher rate. In cancer cells there is typically a high rate of tubulin polymerization. An objective of anticancer therapy it to decrease concentration of tubulins.
What is a membrane lipid raft? How are they formed? Give two types of lipid rafts and their protein make up?
Lipid rafts are a cluster of phospholipids on the cell membrane for lateral or transitional movements of lipids from one monolayer to another and along a monolayer. They limit the fluidity of a region. They can act as receptors for cell signaling. Characterized by caveolar/cavolins and flotinlins/planar proteins. Caveola forms an indentation and is part of the 7 step process of endocytosis. They assist with the internalization of lipid proteins.
Which attribute of the cell membrane determines the susceptibility of the cell to microbial infections?
Carbohydrates are on the external monolayer of the cell and extend into the extracellular matrix to form the glycocalyx. The cell membrane is negatively charged. IgA will bind to these glycolipids, glycoproteins and proteoglycans to increase the negative charge of the cell. Bacteria is also negatively charged and the increased negative charge of the cell will further repel the negatively charged bacteria.
What is lysosomal storage disease?
Accumulation of substrates within lysosome typically related to a defect in hexosamidase. Hexosamidase is an enzyme required for the degradation of glycolipids. In class example involved poor development of the optic nerve due to the buildup of glycolipids to gangliocytes. The extra glycolipids due to lack of hexosamidase led to improper optic nerve development and resulted in blindness. Another in class example was Gaucher's disease which led to accumulation of glycolipids in the spleen and liver.
Which protein functions in the polymerization of actin monomers?
Polymerization is when monomers of actin are linked together through an ATP dependent process. Profilin is an enzyme that catalyzes an increased exchange of ADP for ATP which increases the rate of polymerization of actin. Cofilin ADF (Actin depolymerization filament) inhibits nucleotide exchange and actin becomes depolymerized.
Actin occurs as bundles or networks. Fliamin is a monomer that binds to the actin network to increase stability.
Explain how calcium and cytochrome c contribute to cell apoptosis.
This goes back to the mitochondria which controls levels of Ca and cytochrome C in the cell cytosol. The mitochondrial membrane has an inner membrane and an outer membrane. At the crests, apical portions, of the membrane there is a high concentration of mitochondrial enzymes and an electron gradient for further cell functions and ATP generation. Special membrane translocases transport materials across the mitochondrial membrane. The outer layer of the mitochondrial membrane is more permeable that this inner layer. The mitochondria mops up Ca and cytochrome c. When the mitochondrial membrane permeability equalizes it no longer is able to mop and store Ca or cytochrome c. This increase in mitochondrial membrane leads to apoptosis.
List the 4 phases of cell cycle and state what happens in each state.
M1: during this phase the cell undergoes prophase, interphase, anaphase and telophase.
G1: characterized by normal mature cell growth. During this cycle cyclins (which are non catalytic proteins) and activated cyclin dependent kinase are produced.
S1: transcription factors are made
G2: post synthetic phase with less cyclins and cyclin dependent kinases.
In between M1 and G1 and G2 and M1 there is cytokinesis which is the division of cytoplasm.
The cell may enter the G0 phase, which is an arrest phase before cell division.
There are stable cells which do not often divide but when necessary can go from G0 to G1- bone cells, osteocytes. neurons and skeletal muscles.
There are labile cells with will always be able to go from G0 to G1- skin, kidney, intestine and in class he said brain.
Explain how Ca and cytochrome c contribute to cell apoptosis
Further lecture included discussion of programmed cell death. It can be initiated by stress, hormones lack of nutrients (these are intrinsic and extrinsic factors). When Ca and cytochrome c concentrations increase outside of the mitochondrial membrane this leads to activation of caspases. These caspases will then activate executioner caspases which will then destroy the cell. Apoptotic bodies are the results of caspases. Also discussed p53 proteins regulating micro tubulin in cells and cancer drugs working to either increase p53 or decreasing tubulin concentration. This was a bit of a non sequitur during the class discussion but I thought I would add it. In apoptosis there is no inflammation, it is natural. Also states no Blebs but there are apoptotic bodies.
What are cyclins? How do they differ in function from cyclin-dependent kinases?
Cyclins are proteins that exist in G1. During this phase concentration of cyclins will increase which will trigger cyclin dependent kinases.
