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56 terms

Chapter 3

Cells: The Living Units
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Describe two important functions of the Golgi apparatus
To modify, sort and package proteins
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

Can't replicate
Are Brownian motion, diffusion, and osmosis seen only in living tissue?
No.

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?
Receptor-mediated exocytosis.

Attaches to the receptors or to the substances

Receptors accept to "hitch a ride" into the cell
Other than the nucleus, which organelle has its own DNA?
Mitochondria
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?
Peroxisomes:
Oxidases that use oxygen to detoxify harmful substances.
Neutralize free radicals.
Divide by budding.

Lysosomes:
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.
List the steps in the process of transcription
Initiation
Elongation
Transcription
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

Genetic programming
What factors contribute to the fragility of the lysosome and subsequent cell autolysis?
Cell injury

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
Produces ATP aerobically
Mitochondria
Site of enzymatic breakdown of phagocytized material
Lysosome
Packages proteins for insertion in the cell membrane or for exocytosis
Golgi apparatus
Site of synthesis of lipid and steroid molecules
Smooth ER
Forms the mitotic spindle
Centrioles
Replicate for cell division
Nucleus
Source of cell autolysis
Lysosome
Nonpolar region of phospholipid
Polar tail
Glycocalyx
Attached to the end of outside of polar head
Polar region of phospholipid
Polar head
Peripheral protein
Outside of polar head
Integral protein
Embedded within the bilayer
Identification "tags" for the cell
Glycocalyx
Hydrophilic portion
Polar head
Forms part of the protein synthesis site in the cytoplasm
Ribosomal RNA
Act as "interpreter" molecules that recognize specific amino acids and nucleotide base sequences
Transfer RNA
Attaches the correct amino acid to its transfer RNA
Synthetase enzymes
Provides the energy needed for synthesis reactions
ATP
Found in the cytoplasm, this structure specifies the exact sequence of amino acids of the protein to be made
Messenger RNA
May be attached to the ER or scattered in the cytoplasm
Ribosomal RNA
Chromosomes decoil to form chromatin
Telophase
Chromosomal centromeres split and chromosomes migrate to opposite ends of the cell
Anaphase
Nuclear membrane and nucleolus disintegrate
Late prophase
Chromosomes align on the spindle equator
Metaphase
Centrioles move to opposite ends of cell
Early prophase
Plays a role in the synthesis of steroid-based hormones and proteins
Endoplasmic Reticulum
The actual site of protein synthesis
Ribosomes
Hollow cytoskeletal elements that act as organizers for the cytoskeleton
Microtubules
Dense spherical bodies in the nucleus that are the synthesis sites for ribosomal RNA
Nucleoli
Houses DNA and RNA
Nucleus
Help prevent molecules from passing through the extracellular space between adjacent cells
Tight junctions
Type of anchoring junction
Desmosomes
Communicating junction
Gap
Present in electrically excitable tissues
Gap
Abundant in tissues subjected to great mechanical stress
Desmosomes