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104 Cards in this Set

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  • Back
What is a polar cell?
A cell that has two distinct ends.
Name 6 functions of the cell's plasma membrane.
1) Maintains structural integrity of cell
2) controls movement of substances in and out
3) regulates cell-cell interactions
4) Serves as a recognition board via receptors
5) establishes transport system for specific molecules
6) transduces extracellular physical and chemical signals into intracellular events.
What are 3 types of lipids found in the bi-layer of the plasma membrane?
Phospholipids
Glycolipids
Cholesterol
What is the term that describes the hydrophobic and hydrophillic nature of lipids in the bilayer?
Amphipathic
What is an integral protein?
A membrane-bound protein that is embedded in the lipid bi-layer, or completely spans it.
What type of proteins associated with the plasma membrane are weakly attached via non-covalent interactions?
Peripheral proteins?
What molecule is only associated with the extracellular side of the lipid bilayer?
Glycoproteins and glycolipids. These "glyco" (or carbohydrate) modifications are only found extending into the extracellular space, not the cytosolic space.
What are two classifications for integral membrane proteins, based on how they weave through the lipid bilayer?
Single pass - pass through lipid bilayer once

Multipass - weave back and forth through the bilayer.
What is the major component of the "modified" fluid mosaic model?
It accounts for certain proteins needing to stick together for different functions, linked together via a "lipid raft".
What area of the lipid bilayer is most electron dense, and therefore darker on an electron micrograph?
The hydrophillic, polar heads.
What are channel proteins?
Integral membrane proteins that allow the passage of only one type of ion.
T/F - channel proteins are ion-specific.
True.
What are the 3 different types of channe proteins
Voltage-gated - open via a change in voltage

Ligand-gated - open via a molecule binding (taste)

Mechanically-gated - open via some movement (ear)
T/F - channel proteins require binding to transport against concentration gradient.
False. Ions travel through channel proteins passively, down their concentration gradient.
T/F - pumps and carrier proteins require binding of molecules to transport those molecules across the membrane.
True.
What are some examples of protein pumps in cellular membranes?
- Na/K pump
- Calcium pump
- Glucose transporter
What direction does the Na/K pump operate?
It pumps sodium OUT of the cell, and potassium IN the cell, to re-establish a gradient.
What direction does the Calcium pump operate?
It pumps calcium ions OUT of the cell.
What type/category of membrane proteins are involved in receptor-mediated endocytosis?
Receptor proteins (duh!).
What type of surface receptors on the plasma membrane are involved in signaling via phosphorylation?
Kinases
What do G-proteins do, basically?
They are coupled with surface receptors, involved with signaling.
What is the function for linker and structural proteins in the plasma membrane?
They are involved in cell-cell attachment, cell matrix attachment, and serve as scaffolding for the cytoskeleton.
Where is the nuclear lamina located?
Lining the inside of the inner nuclear membrane.
What are the dense, dark areas of the nucleus called?
Heterochromatin - they are dense, inactive regions of DNA.
What is the lighter-staining region of the nucleus called?
Euchromatin
Where in the nucleus is rRNA assembled into ribosomes?
In the granular portion of the nucleolus.
What is the difference in constitutive and facultative heterochromatin?
Constitutie - heterochromatin that remains inactive of transcription
Facultative - can de-condense and become transcriptionally active (depending on cell type)
T/F - not all euchromatin in the nucleus is "open" for transcription.
True. Some are closed, depending on the cell
What are the major proteins associated with the nucleus?
histones
fibrous proteins
nuclear matrix proteins
ribosomal proteins
transcription factors
polymerases to make DNA
Where do the inner and outer membranes of the nuclear envelope join or connect?
At nuclear pore complexes
What is each membrane of the nuclear envelope associated with?
Inner membrane - associates with nuclear lamina
Outer membrane - contiguous with the endoplasmic reticulum.
T/F - the nuclear pore is a single protein channel.
False. It's a large macromolecule consisting of more than 100 proteins.
T/F - anything can diffuse freely through nuclear pores when they are open.
False. Small molecules can diffuse freely, large macromolecules require energy
Besides energy, what to larger molecules require to go through nuclear pore?
They require a nuclear localization signal (a certain amino acid sequence).
What amino acids are involved in the nuclear localization signal?
Basic amino acids like lysine and arginine.
How are RNA's transported through nuclear pore complexes?
They are transported as ribonucleoproteins, which requires energy via ATP.
What do nuclear shuttle/transport proteins do?
They bring substances to nuclear pore, and tether the substance to the pore. They require energy.
What is the nucleolus?
Prominent structure in nucleus that is the site for rRNA synthesis and ribosome assembly.
T/F - the primary transcript of RNA (no modifications) is processed in the nucleolus to yield mature RNA for ribosome construction.
True.
How many ribosomal proteins are in the large of small subunits of a ribosomes, respectively?
49 proteins in large subunit
33 proteins in small subunit
How many histone molecules make up one nucleosome?
eight
What is a nucleosome?
The functional unit of euchromatin that helps organize the DNA and wrap it.
Where are most cells of the body located in the cell cycle?
In the arrested, G0 phase.
What are the 4 distinct phases of the cell cycle?
M, G1, S, and G2
What phase of cell cycle is involved in DNA rep?
S phase
What happens in the G2 phase of the cell cycle?
DNA proofreading and organelle multiplication.
What regulates the progression through specific "control points" in the cell cycle?
Extracellular signals and cell size.
T/F - no DNA syntesis occurs in G1 phase?
True.
What are ribosomes?
They are giant macromolecular machines that bring together mRNA and aa-tRNA to synthesize polypeptides
What proteins and RNA's are included in each subunit of a ribosome?
- small subunits have 33 proteins and one RNA molecule
- large subunits contain 59 proteins and three RNA molecules.
T/F - a ribosome can be recycled?
True. The subunits dissociated and reform many times.
What is it called when multiple ribosomes are on one mRNA?
Polyribosomes
The subunit numbers for the human ribosomes are what?
Large Subunit - 60S
Small Subunit - 40S
Total - 80S
Where can a protein that is sythesized freely in the cytosol go?
To the nucleus, mitochondria, or peroxisomes, or freely in cytosol
Where can proteins synthesized by membrane-bound ribosomes go?
To the plasma membrane, secretory vesicles, or lysosomes.
What are structures formed as a result of endocytosis, that usually lead to become lysosomes?
Endosomes
What ion concentration does the ER regulate?
Calcium
Where are lipids synthesized in the cell?
ER
Where do the ribosomal subunits bind to on the messenger RNA?
To the 5 prime end.
If a protein has no signal sequence related to it, the ribosome will release it where?
In the cytosol
What organelles are part of the secretory pathway?
ER, Golgi, Secretory Vesicles, Endosomes, Lysosomes, and the Plasma Membrane
What if a protein has an ER signal, but not other specifics, where is the default path after being inserted into ER?
To the plasma membrane.
What are the 3 sections/faces of the golgi, starting in and going out?
Cis, Medial, and Trans
What do vesicles bud off of the golgia?
At the trans-golgi network.
T/F - some post-translational modification of proteins happens at the golgi?
True.
Where in the cell do proteins get a sugar added to their ends and become glycoproteins? "terminally glycosylated"
At the golgi
T/F - vesicles in golgi travel in one direction.
False. Flow is bidirectional.
What is the difference in the constitutive and regulative secretory pathways?
The constitutive is unregulated and constant secretion (like in fibroblasts)

The regulated is where secretions are kept and released by signals (like Mast cells)
What organelle contains degradative enzymes and a low pH of 4.5 - 5.0?
Lysosomes
What do proteins have that serve as "recognition" that they are meant for a lysome?
They have a phosphoyrlated mannose attached. (M6P)
What pump proteins are important for lysosomes?
Hydrogen pumps (to lower pH)
What vesicles are formed by phagocytosis?
Phagosomes
What are peroxisomes?
Membrane-bound organelles containing enzymes that participate in oxidative reactions.
T/F - peroxisomes oxidize long chain fatty acids to create ATP.
False. They do oxidize long chain fatty acids, but the energy generated is not used to synthesize ATP
What organelle is responsible for detoxifying various toxic substances.
Peroxisomes
What is is produced when peroxisomes oxidize substrates?
Hydrogen peroxide, which si broken down by catalase.
What breaks down hydrogen peroxide?
Catalase.
What genetic malfunction in this organelle causes several forms of mental retardation?
Peroxisomes.
What organelles in the cell have double membranes surrounding them?
Mitochondria and the Nucleus
Where do you find the most mitochondria?
In areas of high ATP use (sperm tails, muscle cells, nerve terminals)
What organelle releases toxic cocktail of proteins that brings about death of cell (apoptosis) in response to toxic stimuli?
MItochondria
How to mitochondria divide?
By binary fission.
Which membrane of the mitochondria is not very permeable?
The inner (it must regulate hydrogen ion concentration in the intermembrane space)
What proteolytic structures are located in the cytosol, and not membrane bound?
Proteasome
How to cytosolic proteins get tagged to be destroyed by proteasome?
Tagged with 76 amino acid peptide called ubiquitin
What are proteasome?
Large cylindrical structures that float in the cytoplasm and degrade proteins.
T/F - all the cytoskeletal elements are held together by non-covalent bonds.
True.
What cytoskeletal elements are made up of a dimeric molecule called tubulin?
Microtubules.
Where do you find microtubules?
1) mechanical reinforcing rods for cytoskeleton of cell
2) form spindle fibers for chromosome movement
4) Called neurotubules in neurons, provide tracks for movement in axons
5) cilia and flagella component
What cytoskeletal component is integral in axons?
Microtubules
What is the major site of microtubule polymerization called?
Centrioles (short cylinders of MT at right angles to one another)
What cytoskeletal component anchors and reinforces surface of cell?
Actin (microfilaments)
What protein supports fingerlike projections of the plasma membrane to facilitate movement and increase surface area (microvilli)
Actin
What genetic defect in this actin binding protein causes most common forms of muscular dystrophy?
Genetic defect in dystrophin, an actin-binding protein
What cytoskeletal elements provide tracks for ATP powered motor porteins?
Actin filaments AND microtubules.
What molecule essentially makes up intermediate filaments?
The keratin molecule
What cytoskeletal element forms bundles that link plasma membrane with nucleus?
Intermediate filaments.
What cytoskeletal element reinforces nuclear envelope?
intermediate filaments. And they criss cross around the cell too.
A genetic defect in this filament causes severe blistering of skin, and other disorders.
Intermediate filaments
T/F - intermediate filaments don't usually break under stress.
True. They are like ropes.
Which filament will not break under the most stress?
Intermediate filaments
T/F - intermediate filaments don't polymerize/depolymerize
True. Once you form them they don't form/reform like actin and MT.
What are the inclusions mentioned in class?
Glycogen, LIpids, Lipofuscin, Skin Pigments (hemosiderin, Melanin), and Crystals.
What is lipofuscin?
Brownish, age pigment .