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98 Cards in this Set

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  • Back
What are the general components of a eukaryotic cell?
1.Plasma membrane
2.One or more nuclei
What are the three mechanisms by which cells move materials?
1.Active/Passive transport
2.Gated Transport
3.Vesicular Transport
How do small, uncharged molecules move inside the cell
Simple diffusion across a concentration gradient
How do small, water soluble molecules move inside the cell
Active or facilitated transport
What molecules can move across the cell membrane in special channels (i.e. membranes surrounding the RER)
Proteins in the process of synthesis
Give an example of gated transport
Movement of molecules through nuclear pores into/out the nucleus
How does vesicular transport occur?
By uptake of vesicles by cells via endocytosis or phagocytosis
How does selective transport of vesicles occur?
By the budding of vesicles of one cell binding to another cell.
When does this occur?
Biosynthetic-secretory pathway and the endocytic pathway in cells
What are the three types of vesicles involved with vesicular transport?
What do clathrin coated vesicles tend to be involved with?
1.Movement into the cell to cytoplasm
2.Movement from the Golgi to the cell surface
What do COP-II vesicles tend to be involved with?
1.Movement from the ER to and through the Golgi
What do COP-I vesicles tend to be involved with?
1. Retrieval of membranes and contents
What is the plasma membrane and what is its function?
A selective barrier that regulates the passage of materials into/out of the cell.
Also transmits signals
Cell membranes are (homogenous/non-homogenous)in nature
What is a lipid raft?
Molecules group as a microdomain (less fluid than the membrane)
Enzymatically active areas of the membrane contain high amount of ________?
The fluid mosaic model of the cell membrane proposes that:
1. Membrane consists of a phospholipid bi-layer (50% mass)
2. Membrane has 50% mass in proteins (integral, transmembrane, and peripheral proteins)
3. Oligosaccharide chains on the extracellular surface
The glycolipids and glycoproteins on the surface of the cell form the ______ with a (+,-) charge
glycocalyx, negative
How does the membrane act to regulate the intercellular env.
By acting as a selective barrier via the actions of integral proteins
What are the functions of integral proteins
2.Cell receptors
4.Cell adhesion
Where are tight junctions (zonula occludens) located and what is their function?
a.Located on the luminal border between adj. epithelial cells
b.Limits the movement of proteins & lipids to that cell only.
c. Allows cells to have different compositions/functions
How big is the nucleus?
6-10 um diameter
How many layers does the nuclear membrane have?
What are the functions of the nucleus?
1.Protection, replication, synthesis, and expression of the genome.
2. Synthesis of large and small ribosomal subunits.
Where are the two unit membranes of the nucleus continuous with each other
At nuclear pores
What is the perinuclear cisterna?
The space between the 2 nuclear membranes.
What can the outer nuclear membrane be continuous with?
the RER
What are the function of nuclear pores
1.Act as gated channels
What is the fibrous lamina?
Layer of intermediate filaments just inside the inner nuclear membrane
What is the fibrous lamina composed of?
Lamins a,b,c
What happens when they are phosphorylated?
The nuclear envelope disassembles
What is chromatin
uncondensed genetic material (DNA, histones, non-histone protein)
What is a nucleosome?
DNA wrapped around packets of 4 specific proteins (histones)
Heterochromatin is/is not capable of being expressed.
Euchromatin is/is not capable of being expressed.
Heterochromatin: Not capable
Euchromatin: Capable
What is a chromosome
1. A darkly-stained, rod-like body of condensed chromatin.
What is the basic unit of a chromosome?
A nucleosome.
What is the nucleolus
A dense aggregate of protein and nucleic acid.
What happens at the nucleolus
1.Transcription of ribosomal DNA by RNA polymerase I
2. Synthesis of ribosomal subunits
What are the 3 components of the nucleolus?
1. The nucleolar organizing DNA
2. Nucleolema pars fibrosa (densely packed RNP fibers)
3. Nucleolema pars granulosa(maturing ribosmes)
What are the number and size of nucleoli usually related to?
1.# of ribosomes produced
2.Protein synthesis act. of cell
Where are polyribosomal proteins synthesized?
In the cytosol (enter the nucleus and associate w/ribosomes in nucleolus)
How does protein/polypeptide synthesis begin?
When the small ribosomal subunit binds to the m/tRNA in the cytoplasm. Large subunit binds afterwards
What are polyribosomes
The appearance of multiple ribosomes translating the same mRNA
Accumulations of ribosomes are _____?
On what type of ribosomes are proteins destined for use in the cytosol translated?
Free ribosomes
Secreted, lysosome-used, and integral proteins are translated where?
Bound to RER
What is the structure of the RER?
Series of membrane-limited flattening interconnected cisterna containing ribosomes on the cytoplasmic surface.
What is the function of the RER?
1. Synthesis of proteins for secretion, use by other organelles, and integral membrane proteins.
What 4 characteristics will cells specialized for protein secretion have?
1. Abundant RER
2. Prominent golgi
3. Euchromatic nuclei
4. Dense membrane-bounded secretory products.
How are proteins modified in the RER?
1.Signal seq. cleaved by sig. peptidases
2.Glycosylation of glycoproteins
3.Post-translational modification
5.Assembled w/other proteins
What are the functions of the Golgi?
1. Major site of carb synthesis
2. Sorting station for material in the cell
How does the golgi modify proteins?
1. glycosylation of proteins nad lipids
2. phosphorylation or sulfonation of glycoproteins
What is the structure of the golgi?
- stack of 3-10 flattened membrane-bound cisternae with dilated rims
Where is the golgi located
near (often apical) to the nucleus
What are the 3 regions of the golgi?
Cis-golgi network (forming face)
Medial golgi cisterna
Trans golgi cisterna
What are the major digestive organelles of the cell
What are the enzymes that catalyze degradative functions called in lysosomes?
What is the structure of a lysosome?
Single-unit membrane with a number of morphologic appearances.
How is a low pH maintained in a lysosome?
By membrane-bound ATP-driven pump (Exchanges NA+ for H+)
How are materials digested by lysosomes?
endo/pinocytosis, receptor-mediated endocytosis, phagocytosis, or autophagy
What are proteasomes?
multi-hydolase compounds that digest single cytoplasmic proteins
Accumulations of SER are baso, eosinophilic?
eosinophilic due to protein content of membranes
What are the functions of the SER?
1.Synth. of steroid hormones
2.Detox of lipid-sol. drugs
3.Convert water-insol drugs to more water-sol. drugs
4.Synth. of lipids for lipoproteins for cell membrane
5.Synth. of phopholipids for cell membrane
6.Glycogen metabolism
7.Ca++ ion sequestration
What are the functions of peroxisomes
1.Degrade toxic molecules, part. in the liver and kidney
2.Beta oxidation of long-chain FA's
3.Can be involved in purine metabolism
How do oxidases work?
By removing hydrogen
What is the byproduct?
Hydrogen peroxide
What does catalase do?
converts hydrogen peroxide to water and oxygen
What is Zellweger syndrome?
Defects in the transport enzymes that move peroxisomal enzymes into the membrane.
Mitochondria are present in all cells except _____
What is the s(x) of mitochondria?
Two unit membranes that form the intermembrane space and matrix compartment
What are the tubular cristae
The projections of the inner mitochondrial membrane.
Where is most of the mitochondrial protein made?
In the nucleus (nuclear DNA) and made on cytoplasmic ribosomes.
What are the functions of the mitochondria?
1.Conv. of pyruvate to Acetyl-CoA
2.ATP formation
3.Ca++ sequestering
4.lipid metabolism
5.processing of intermediates in steroid synthesis
What are the 3 components of the cytoskeleton?
3.Intermediate Filaments
What are microtubules?
Unbranched tubular structures composed of the protein tubulin.
What do microtubules do?
1.Support the force-generating actions of cilia and flagella
2.Form the mitotic and meiotic apparatus/spindle
What do the drugs colchicine, vinblastine, vincristine do and what are they used for?
Break down microtubules; used for cancer treatment

Taxol: microtubule stabilizing
What are microfilaments composed of?
What are the functions of microfilaments?
1.Motility of cytoplasmic comp's
2.form a support network under the plama membrane
What is the "molecular motor" that moves actin?
What are the functions of intermediate filaments?
1.Provide tensile strength
2.Insert into desmosomes and hemidesmosomes.
What are the three types of cell junctions?
1.Occluding Junctions
2.Anchoring junctions
3.Communicating junctions
What is the function of occluding junctions?
To regulate the flow of material from the lumen/surface of an epithelium to the lateral intercellular space between the epithelial cells
What do anchoring junctions do?
provide adhesion between cells
Where are zonula adherens located?
at the junctional complexes in epithelial cells
What is the zonula adherens molecule composed of?
E-cadherin: transmembrane adhesion molecule
What is the adhesion of zonula adherens dependent on?
Ca++ presence
What is the fascia adherens located?
cardiac muscle cells
What is another name for a macula adherens?
On what side of the macula adherins is an attachment plaque through which intermediate fibers run?
cytoplasmic side
Between the cells of a macula adhesions, what are the extracellular parts of the transmembrane glycoproteins a part of?
Ca++ dependent cadherin cell adhesion molecules
What does a hemidesmosome do?
provide adhesion btw. a cell and the basement membrane. (think thick skin)
how are communicating junctions connected?
by transmembrane channels or small pores
what do connexons do
allow diffusion of small molecules btw. cells
how much electrical resistance is there btw. cells at gap junctions
What is the structure of connexons
6 integral membrane proteins in a circular arrangement
Where do gap junctions occur
2.Cardiac muscle
3.Bone cells
4.Smooth muscle
5.Nerve cells