Why can we say that a cell without a nucleus will ultimately die?
Can't make proteins
Can't replace enzymes or other cell structures which are continuously recycled
Are Brownian motion, diffusion, and osmosis seen only in living tissue?
Passive processes that do not require energy
Occur in the absence of any cellular processes.
What forces maintain a steady state "resting" membrane potential?
Both diffusion and active transport mechanisms operate within the cell membrane to maintain a resting membrane potential
Briefly describe the glycocalyx
Sticky, carbohydrate-rich area on cell surface.
Binds cells together
Provides a highly specific biological marker by which cells can recognize each other
Explain the term genetic code. What does it code for? What are the letters of the code?
The genetic code is the information encoded in the nucleotide base sequence of DNA.
A sequence of three bases, called a triplet, specifies amino acid in a protein.
The letters of the code are the four nucleotide bases of DNA designated as A, T, C, and G.
Why are the free radicals so dangerous to cells and how are they dealt with by the body?
Highly reactive chemicals
Cause havoc in any cellular environment by reacting with things they should not.
Cells with peroxisomes have enzymes specific to reducing free radicals into less reactive chemicals.
In all living cells hydrostatic and osmotic pressures exist. Define these pressures and explains how they are used in the concept of tonicity of the cell?
Hydrostatic pressure: pressure of water exerted on the cell membrane
Osmotic pressure: created by different concentrations of molecules in a solution separated by the cell membrane
Pressures are exerted on the membrane
Used by the cell to change the shape of the cell
Regulate substances entering and exiting the cell
Brings about polarity of the cell
What is the common route of entry for flu viruses into a cell?
Attaches to the receptors or to the substances
Receptors accept to "hitch a ride" into the cell
How are the products of free ribosomes different from membrane-bound ribosomes?
Free ribosomes: Make soluble proteins that function in the cytosol.
Membrane-bound ribosomes: Produce proteins that are to be used on the cell membrane or exported from the cell
How are peroxisomes different from lysosomes?
Oxidases that use oxygen to detoxify harmful substances.
Neutralize free radicals.
Divide by budding.
Hydrolytic enzymes that destroy anything they come in contact with.
Manufactured by the Golgi apparatus.
Briefly name the subphases of interphase and tell what they do
G1 - growth phase. The cell is metabolically active and the centriole begins to divide at the end of this phase
S - DNA replicates itself. New histones are made and assembled into chromatin
G2 - Enzymes and proteins are synthesized and centriole replication is completed. This is the final phase of interphase.
What are nucleolar organizer regions?
Nuclear regions containing the DNA that issues genetic instructions for synthesizing ribosomal RNA
How is the resting potential formed? How is it maintained?
It is formed by diffusion of ions resulting in ionic imbalances that polarize the membrane.
It is maintained by active transport processes.
List possible causes of aging
Chemical insults and free radical formation (wear & tear)
Diminished energy production by free radical-damaged mitochondria
Progressive disorders in the immune system
What factors contribute to the fragility of the lysosome and subsequent cell autolysis?
Cell oxygen deprivation
Excessive amounts of vitamin A in the cell
Why can we say that cells are protein factories?
Most of the metabolic machinery of the cell is involved in protein synthesis
Structural proteins constitute most of the cell dry material
Functional proteins direct all cellular activities
What are cell exons and introns?
Exons are amino acid-specifying informational sequences in genes
Introns are noncoding gene segments that provide a resevoir of ready-to-use DNA segments for genome evolution and a source of a large variety of RNA molecules
What are lipid rafts? What are their function?
They are assemblies of saturated phospholipids associated with sphingolipids and cholesterol.
They are concentrating platforms for molecules needed for cell signaling
Act as "interpreter" molecules that recognize specific amino acids and nucleotide base sequences
Found in the cytoplasm, this structure specifies the exact sequence of amino acids of the protein to be made
Help prevent molecules from passing through the extracellular space between adjacent cells