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59 Cards in this Set
- Front
- Back
What are the major functional categories or proteins? |
Transport Structural Motor function Other functions: Catalysis Immunity Regulation of gene expression |
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What are the characteristics of the transport function of proteins? |
Myoglobin transports O2 throughout muscles Hemoglobin transports O2 in blood |
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What are the characteristics of the structural function of proteins? |
Actin forms microfilaments in cells Tubulin dimers constitute microtubules Keratin filaments constitute the bulk of animal hair Collagen is a major protein in connective tissue |
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What are the characteristics of the motor function of proteins? |
Myosin interacts with actin to facilitate muscular movement Kinesin moves along microtubules to support a variety of cellular functions |
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Where is myoglobin found? |
In muscle cells |
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What is the function of myoglobin (Mb)? |
Promote diffusion of O2 into and through muscle cells |
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Where is hemoglobin (Hb) found? |
In red blood cell |
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What is the function of hemoglobin? |
Promote diffusion of O2 through the body ( binds O2 at lungs releases at tissues) |
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What are the three important characteristics of hemoglobin and myoglobin? |
1. O2 transport is critical for sustaining life 2. Hemoglobin mutation can possibly lead to disease 3. Characteristics about O2 binding to myoglobin and hemoglobin are observed in many areas of biochemistry |
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What type of group is a heme? |
A prosthetic group |
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What is a heme? |
A porphyrin that chelates iron for oxygen transport |
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What type of protein is myoglobin? |
Classical globular protei |
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How does myoglobin transport O2? |
Via the Fe in hem |
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What role does histidine play in myoglobin function? |
Histidine residues play a key role in anchoring both O2 and iron |
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How is anemia treated? |
With iron supplements or an iron-rich diet |
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What is the product of the reaction Mb + O2? |
MbO2 |
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Pertaining to heme in the myoglobin function, what is K equal to? |
K = {[Mb][O2] / [MbO2]} |
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In what trend does myoglobin bind to O2? |
Hyperbolic trend |
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In what way does O2 bind to the heme group of myoglobin? |
Such that binding is half-maximal when the oxygen concentration is equal to the dissociation constant |
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What is a prosthetic group? |
Organic molecule bound to protein that is essential for the protein's function |
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What are the similarities of myoglobin and hemoglobin? |
Subunits are structurally similar Only approximately 18% identical in primary sequence Similar in their secondary and tertiary structures (they almost overlap perfectly) |
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Hb or Mb: Has a quaternary structure |
Hemoglobin |
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What does the similarities in Mb and Hb structures and sequence indicate? |
A common evolutionary background |
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What is the level of importance for invariant of Hb sequences? |
Essential for function |
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What is the level of importance for conservatively substituted of Hb sequences? |
Somewhat important for function |
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What is the level of importance for variable of Hb sequences? |
Not important for functio |
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What is the chemical formula for Bohr effect and O2 transport? |
Hb . H+ + O2 <-- --> Hb . O2 + H+ |
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What happens to pH and O2 affinity based on the Bohr effect? |
pH increases = O2 affinity increases |
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What decreases Hb's O2 affinity? |
BPG |
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What effects does BPG have on Hb's O2 affinity? |
BPG binds only to the tense (deoxy) conformation of Hb BPG stabilizes the deoxy state Cells need BPG in order for Hb to release enough O2, otherwise O2 binds too tightly |
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What amino acid mutation is caused by a point mutation in beta-hemoglobin? |
Glu --> Val mutatio |
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What are the symptoms of sickle cell anemia? |
Fatigue Shortness of breath Joint pain Splenic sequestration Lung and other tissue damage |
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How do RBC's get the sickled shape? |
Results in polymerization of hemoglobin (fiber formation) |
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What happens when one has sickle cell anemia? |
People with sickle cell anemia have two copies of the mutated gene |
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What characteristic do carriers of sickle cell anemia have? |
Carriers of the sickle cell trait only have one copy of the mutated gene |
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Like cystic fibrosis, what type of disease is sickle cell anemia? |
A recessive disease |
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How many types of proteins is cytoskeleton ("skeleton") made of? |
Three |
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What helps maintain the shape and position of organelles? |
Cytoskeleton |
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What are the characteristics of microfilaments? |
Actin forms microfilaments in cells Polymers of actin Support plasma membrane and determines shape Associates with motor proteins Formed by globular actin subunits associate in a double chain Monomeric actin is a globular protein that binds to ATP Actin polymerization is driven by the hydrolysis of ATP |
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What are the characteristics of intermediate filaments? |
Do not associate with motor proteins Basic structural unit is a dimer of alpha-helices that wind around each other --> coiled coil The dimers then associate to form higher-order fibrous structures that consist of 16-32 polypeptides |
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What is keratin? |
Intermediate filament |
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What is the thickness of intermediate filaments? |
Intermediate in thickness to microfilaments and microtubules |
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What are the characteristics of microtubules? |
Tubulin dimers constitute microtubules Hollow fibers built from tubulin dimers Associates with motor proteins Thicker and more rigid than microfilaments Constructed as a hollow tube built from tubulin dimers Made from dimers of the proteins alpha- and beta tubulin |
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What constitutes the bulk of animal hair? |
Keratin filament |
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What is a major protein in connective tissue? |
Collagen |
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What is the function of actin in microfilaments? |
Actin is added and removed on both the (-) and (+) ends Actin is added more rapidly on the (+) end |
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What allows cells to change/adjust shape? |
The ability for microfilaments to change and adjust in lengt |
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What are the characteristics of the assembly/disassembly of microtubules? |
Able to assemble and disassemble to allow for cells to change shape Can be observed as dividing cells The disassembly of microtubules, along with action of motor proteins, draws the chromosomes apart |
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What are the characteristics of keratin? |
Keratin forms a coiled-coil structure Keratin fibers are cross-linked through disulfide bonds Keratin is used to make hair, nails, and ski |
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What are the characteristics of collagen? |
Structural protein that is not part of the cytoskeleton Helps hold cells together --> in connective tissue and bone Most abundant protein in animal Triple helix Covalently cross-linked Every 3rd amino acid = Gly Approximately 30% or remaining amino acids are proline or hydroxyproline |
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What stabilizes collagen' structure? |
Cross-linking |
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What is required for the formation of Hyp and Pro? |
Ascorbate or Vitamin C |
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What is a motor protein? |
Molecular motors that use ATP hydrolysis to move along cytoskeletal filaments within the cel |
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What is the function of myosin? |
Acts on actin filaments to carry out muscle contraction |
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What are the characteristics of myosin? |
Two heads and a long tail Binds to ATP ATP hydrolysis drive the physical movement of myosin along an actin filament |
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What are the four steps as to how two myosin heads work independently of each other? |
1. The reaction sequence begins with a myosin head bound to an actin subunit of the thin filament. ATP binding alters the configuration of the myosin head so that it releases actin 2. The rapid hydrolysis of ATP to ADP + Pi triggers conformational change that rotates the myosin lever and increases the affinity of myosin for actin 3. Myosin binds to an actin subunit farther along the thin filament 4. Binding to actin causes Pi and then ADP to be released. As these reaction products exit, the myosin lever returns to its original position. This causes the thin filament to move relative to the thick filament (the power stroke). ATP replaces the lost ADP to repeat the reaction cycle |
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What are the characteristics of kinesin? |
Moves along microtubules for intracellular transport A microtubule-association protein |
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How does kinesin transport cargo? |
By moving processively along a microtubule trac |
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Through what mechanism does kinesin work?
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Similar to myosin, except the two heads work in a coordinated fashion, not independently |