Test 1 (Module 1) Flashcards
What are limiting factors of Cell size?
Cell size is limited by:
1) the volume of cytoplasm that can be supported by the genes in the nucleus
2) the volume cytoplasm that can be supported by exchange of nutrients
3) the distance over which substances can efficiently travel through the cytoplasm via diffusion
What are HeLa cells?
Cultured tumor cells that were isolated from a cancer patient (Henrietta Lacks) by George Gey in 1951. They are used in research today.
What are the central differences between Prokaryotic and Eukaryotic cells?
Complexity: Prokaryotes are relatively simple; eukaryotes are more complex in structure and function
Amount: Eukaryotes have much more genetic material
Form: Eukaryotes have many chromosomes made of both DNA and protein whereas prokaryotes have a single circular DNA
Cytoplasm: Eukaryotes have membrane-bound organelles and complex cytoskeletal proteins. While both have ribosomes, they differ in size
Cellular Reproduction: Eukaryotes divide by mitosis; prokaryotes divide by simple fission
Locomotion: Eukaryotes use both cytoplasmic movement, and cilia and flagella; prokaryotes have flagella but they differ in both form and mechanism
What are the Two Types of Prokaryotic Cells? What are examples of each?
1) Domain Archaea: Methanogens, Halophiles, Acidophiles, Thermophiles
2) Domain Bacteria:
Includes the smallest known cells - mycoplasma
Includes cyanobacteria, some photosynthetic bacteria Cyanobacteria gave rise to green plants and an oxygen-rich atmosphere
Some bacteria are capable of nitrogen fixation
What are the primary Model Organisms used for research purposes?
There are six (6) model organisms:
1) the bacterium Escherichia coli
2) the yeast Saccharomyces
3) the mustard plant Arabidopsis
4) the nematode Caenorhabditis elegans
5) the fruit fly Drosophila melanogaster
6) the mouse Mus musculus
Discuss some characteristics of the Semipermeable Lipid Bilayer, then discuss the main roles of Epithelial cells.
Semipermeable lipid bilayer: osmotic pressure, [charges], [P-] inside cell is much greater than outside cell in the plasma, electrolytes [Ca2+, Na+, Cl-, K+]
Epithelial cells: 1) protection, 2) absorption, 3) secretion (endocrine)
Discuss the characteristics of Multicellular organisms.
Differentiation occurs (terminally differentiated cells, pluripotency), but stem cells and gametes also present (totipotent). Even though cells differentiate, adaptation occurs as they respond to physiological pressures such as hormones, steroids, and stress. The can switch to a different phenotype but not a completely different kind of cell (dedifferentiation). For example, fibroblasts can differentiate to adipocytes due to the presence of hormones (cortisol). Importantly, there is significant plasticity and flexibility with multicellular organisms (eg. neurogenesis in CNS).
The cells share: genome/RNA, organelles (ribosomes, mitochondria), membrane/cell wall, cytoplasm, Pr- (including enzymes, structural/histones, carrier, channel and receptor proteins)
What are the Major Roles of the Plasma Membrane?
- Protection (from pathogens)
- Signaling (responding to external signals, intra and intercellular interaction; energy transduction)
- Fusion/Splitting of cells
- Transport/Selectively Permeable Barrier (endocytosis/exocytosis)
- Osmotic Pressure [gradient]
- Electrical Charge
- Compartmentalization (creating a specific environment/conditions for various functions)
- Scaffolding for biochemical activities (the shape affects functional capabilities)
Discuss the Plasma Membrane Structure.
- Lipid Bilayer (hydrophilic head, hydrophobic tail)
- Protein-lined pores punctuate the contour of the cell membrane; this is a key to polar solute and ion movements
- Fluid-Mosaic Model is current understanding. The lipid bilayer exists in fluid state, capable of movement itself.
- Includes: peripheral Pr-, hydrophobic alpha helix, integral Pr-, cholesterol, phospholipids, glycoproteins, glycolipids, oligosaccharides, etc.
- Chemical Composition; lipid and Pr- components bound by non-covalent bonds, and contains carbohydrates
Why are Carbohydrates important in the Plasma Membrane?
They reinforce the structural integrity of membranes, and are important in presenting receptors for identification (antigens) and communication (eg. RBC and blood type/Rh Factor)
Why are Saturated and Unsaturated Lipids important in the structural integrity of the plasma membrane?
Combining both types allows for greater size/thickness with fewer molecules–while still maintaining structural integrity–due to the linear and kinked nature of saturated and unsaturated lipids respectively.
When would a cell need to change the shape/confirmation of its Plasma Membrane?
- phagocytosis
- extravasation
- locomotion
- secretion
- fusion (embryogenesis)
How does a cell membrane expand, as in cellular division?
Cell membranes come from other cell membranes (it is not a de novo process)
Cells produce the lipid components via golgi bodies to expand existing components
Lipids are much more dynamic than previously thought. How so?
Integral membrane proteins, peripheral membrane proteins (non-covalently linked), and GPI-anchored protein (covalent linkage) allows them to participate in various movements, many of which are continuous, and this allows the membrane to remain a dynamic structure.
Understanding the topography of the membrane allows us to draw conclusions about membrane “sidedness”–which is to say where and how much protein is distributed throughout. Proteins embedded in the plasma membrane are anchored more prevalently on one side of the lipid bilayer of the other. What methods might we use to determine this sidedness of proteins?
- if it is located inside the cell membrane, use an enzyme
- GFP
- antibodies
- florescence
- radioactivity/radioactive markers
- Western Blot
- We can use data/fxn/known similar activity of a given target receptor/molecule to determine its likely structure in cases where direct study of the structure is not possible
