Chapter 3 The Living Units

What is the apoptosis and what is its importance in the body?

Apoptosis of programmed cell death which rids the body of cells that are stressed, damaged, old, or no longer needed.

What are two body fluids that inhabit the extracellular space and what role does each play in the body?

Blood plasma is extracellular fluid that transports nutrients, gases, hormones, and other substances throughout the body. Interstital fluid is an important transport and dissolving medium.

How are microtubles and? micro-filaments related functionally?

Both are involved in organelle movements within the cell and/or movements.

What vesicular transport process allows a cell to take in cholesterol from the extracellular fluid?

Cholesterol is taken in by receptor-mediated endocytosis.

Codons and anticodons are both three-base sequences. How do they differ?

Codons are three base sequences in mRNA, each of which specifies an amino acid. Anticodons are three-base sequences in tRNA that are complementary to the codons specifying the amino acids they transport to the ribosome during protein synthesis.

What is the role of DNA in transcription?

DNA provides the coded instructions for protein synthesis via the mRNA synthesized on it.

What event or process establishes the resting membrane potential?

Diffusion of ions, mainly the diffusion of K+ from the cell through leakage channels, establishes the resting membrane potential.

As a cell grows, its plasma membrane expands. Does this membrane expansion involve endocytosis or exocytosis?

Exocytosis

What is the wear-and-tear theory of aging?

The wear-and-tear theory of aging attributes aging to little chemical insults and free radicals which have contribute detrimental effects.

If a cell ejects or loses its nucleus, what is its fate and why?

To die, it will be unable to make proteins, which include the enzymes needed for all metabolic reactions.

The major function of cilia is to move substances across the free cell surface. What is the major role of microvilli?

To increase the cell's surface area for absorption or filtration of substances.

What is the importance of ubiquitin in the life of a cell?

Ubiquitin attaches to misfolded, damaged, or unneeded proteins, tagging them for destruction by proteasomes.

During what phase of the cell cycle is DNA synthesized?

S phase

What basic structure do all cellular membranes share?

A double layer of phospholipids in which proteins are embedded.

How do the A, P, and E ribosomal sites differ functionally during protein synthesis?

A site = entry site fro tRNA at the ribosomes. P site = site where peptide bonds form between delivered amino acids E site = the tRNA exit site from the ribosome

If one of the DNA strands being replicated "reads" CGAATG, what will be the base sequence of the corresponding DNA stand?

GCTTAC

What is the importance of the histone proteins present in the nucleus?

Histone proteins provide the means to pack DNA in a compact, orderly way and play a role in gene regulation.

Why do phospholipids, which form the greater part of cell membranes, organize into a bilayer - tail-to-tail -in a watery environment?

Hydrophobic regions orient toward each other while the hydrophilic regions orient to he aqueous fluid inside and outside the cell.

What are two types of facilitated diffusion and how do they differ?

In channel - mediated diffusion, the diffusing substance moves through a membrane channel. In carrier - mediated diffusion, the diffusing substance attaches to a membrane carrier which moves it across the membrane.

Of micro-filaments, microtubules, or intermediate filaments, which is most important in maintaining cell shape?

Intermediate filaments

How would you explain the meaning of a "generalized cell" to a classmate?

It is the cell concept that includes structures and functions common to all cells.

What is the energy source for all types of diffusion?

Kinetic Energy

What term is used to indicate signaling chemicals that bind to membrane receptors? Which type of membrane receptors is most important in directing intracellular events by promoting formation of second messengers?

Ligands, G protein-linked receptors

What organelle is the major site of ATP synthesis?

Mitochondria

In the inside of the plasma membrane negative or positive relative to its outside in a polarized membrane?

Negative

What are three events occurring in prophase that are undone in telophase?

Nuclear envelope breaks up, spindle forms, nucleoli disappear, and the chromosomes coil and condense

What is the role of nucleoli?

Nucleoli are the site of synthesis of ribosomal subunits

Phagocytic cells gather in the lungs, particularly in the lungs of smokers. What is the connection?

Phagocytic cells engulf debris and a smoker's lungs would be laden with carbon particles and other debris and a smoker's lungs would be laden with carbon particles and other debris from smoke inhalation.

What happens when the Na+ -K+ pump is phosphorylated? When K+ binds to the pump protein?

Phosphorylation of the Na+ -K+ pump causes the pump protein to change shape so that it "pumps" Na+ across the membrane. K+ binding to the pump proteins triggers the release of phosphate and the pump protein returns to its original shape.

Name the three basic parts of a cell and describe the function of each.

Plasma membrane (the outer boundary of the cell), the nucleus (control center of the cell), and the cytoplasm (the fluid material between the nucleus and plasma membrane), which contains organelles.

What are three organelles involved in protein synthesis and how do these organelles interact in that process?

Ribosomes are the sites of protein synthesis. Rough ER provides a site for ribosomes attachment and its cisternae package invesicles the proteins made on the ribosomes for transport to the Golgi Apparatus. Golgi Apparatus modifies and packages the proteins it receives for various destinations within or outside the cell.

What two types of membrane junctions would you expect to find between muscle cells of the heart?

The heart has desmosomes (anchoring junctions) that secure cardiac cells together as the heart works and gap junctions (communicating junctions) that allow ions to flow from cardiac cells to cardiac cells.

How does the function of lysosomes compare to that of peroxisomes?

The lysosomal enzymes digest foreign substances engulfed by the cell, non useful or deteriorating organelles, or even the face itself to prevent the buildup of cellular debris. The enzymes in peroxisomes detoxify harmful chemicals and neutralize free radicals

What determines the direction of any diffusion process?

The relative concentration of the substance in different areas determines the direction of diffusion. Diffusion occurs from regions of high concentrations to regions of low concentration.

What is the importance of the glycocalyx in cell interactions?

The sugar residues of the glycocalyx provide recognizable biological markers for cells to recognize each other.