BR Bio Set 2 Flashcards
antibody mechs
- opsonization: coating leads to phagocytosis
- neutralization by coating
- complement activation by creating an antibody-antigen complex that is recognized by a complement protein, thus triggering an immune response (eg. membrane attack complex lyses the cell)
types of antibodies
IgA: found in milk; protects the nursing infant
IgD: unknown
IgE: binds to mast cells and is involved w allergic reactions
IgG: able to cross the placenta; most abundant and is produced within days after IgM antibody is secreted
IgM: produced a few days after detection of an antigen, making it the first antibody produced in response to an antigen
antibody structure
Composed of four subunits arranged in a Y configuration
= 2 lights chains + 2 heavy chains, Joined together by disulfide bonds
within each subunit is a variable and constant domain
- Variable regions are located at the terminal ends of the chains, differing in the amino acid sequence; Also the location of the antigen binding site
- Constant regions are found in the lower portion of the Ig
D vs L configuration
in sugars; look at their fisher projection
dependent on the chiral carbon that is most distant from the carbonyl carbon, referred to as a reference carbon
D if hydroxyl group on reference carbon is to the right
L …. to the left
Cholesterol
be able to draw structure
synthesized in the cytosol and generally exists as the cholesterol ester; major constituent of eukaryotic animal plasma membrane and is an intermediate in the biosynthesis of all human steroid hormones
Has a fairly rigid set of four fused non polar rings + polar hydroxyl group, thus granting it a slightly amphiphilic attribute
smooth ER
lacks ribosomes; appears more tubular in shape; involved in the synthesis of a majority of the cell’s membrane lipids; also involved in hydroxylation reactions that aid in the detoxification of drugs (basically makes a substance more water soluble, thus making it easier to eliminate in the body)
In hepatocytes, important for catabolism of liver glycogen
In other cells, can help regulate Ca2+ levels
rough ER
studded w ribosomes; generally flat and sheet like
Embedded ribosomes synthesize membrane and secretory proteins that are then passed through the RER and into the lumen, where post-translational modification begins via hydroxylation and glycosidation events
Proteins after this modification are then shuttled to the Golgi apparatus, where modification continues even more
After golgi, the proteins are sent to their final destinations
golgi apparatus
- regions
- pathway
complex of cisternae (flattened membranes)
- Cis cisterna region: face the nucleus and ER
- Trans: face plasma membrane
- Medial: located btwn the cis and trans cisternae
As a protein is passed from the cis to trans cisterna, diff chemical modifications occur, involved glycosylation (addition of carbohydrates), sulfation (addition of inorganic sulfate), proteolysis (reducing the size of the protein)
Once the proteins reach the trans face, they are sorted and concentrated into vesicles that are destined for different regions of the cell
Peroxisomes
single membrane-bounded organelles found within the cellular cytoplasm, contains lots of enzymes (like lysosome) but notably contains catalase, which degrade hydrogen peroxide
Peroxisome can generate hydrogen peroxide, which is a potentially damaging oxidant
– Used in the dissipation of heat
viral interactions w host cells
- adsorption
- host range
Adsorption: interaction of that virus w the host cell’s surface to facilitate binding prior to entry
Host range: restriction on the specific organisms or cell types that a virus can infect
– Dependent on interaction of that virus w the host cell’s surface proteins, glycoproteins, and glycolipids
metabolism v catabolism v anabolism
Metabolism: refer to all processes that occur within living organisms
Catabolism: breakdown of complex molecules into smaller and simpler products, usually accompanied by the release of energy
Anabolism: building up or becoming more complex development of a molecule; biosynthesis of small precursor molecules into larger and more complex
how do we regenerate NAD+ in order to continue glycolyssi
Pyruvate acted on by lactate dehydrogenase to yield lactate and NAD+
Occurs when oxygen becomes a limiting factor, thus becoming an anaerobic reaction → ie in muscles during exercise
Lactate will be transported by blood to liver, where it is converted back into pyruvate
Pyruvate can be converted back into glucose via gluconeogenesis since two lactates (C3H6O3) can make one glucose (C6H12O6)
ALTERNATIVELY,
Pyruvate can be acted on by pyruvate decarboxylase to yield acetaldehyde and CO2 via alcoholic fermentation → acetaldehyde can be acted on by alcohol dehydrogenase to yield ethanol and NAD+
regulation of glycolysis
Irreversible at hexokinase, phosphofructokinase, and pyruvate kinase → act as control points
High levels of ATP allosterically inhibit phosphofructokinase
[H+] from conversion of pyruvate into lactate also allosterically inhibits phosphofructokinase → surplus of hydrogen ions causes drop in pH, leading to acidosis
Citrate from the Krebs cycle also inhibit phosphofructokinase
High levels of AMP promote / stimulate phosphofructokinase
Complexes of ETC, pathway
Complex 1 (NADH-Q reductase): reduced NADH + H+ passes two electrons and two hydrogens to the oxidized flavin mononucleotide (FMN) prosthetic group assoc w this complex → results in production of reduced FMNH2 and regeneration of oxidized NAD+ -- Electrons from FMNH2 are passed to a series of iron-sulfur clusters (Fe-S) where iron atoms cycle btwn the reduced ferrous (Fe2+) and the oxidized ferric (Fe3+) states, allowing electrons to eventually be passed from a reduced Fe-S moiety to the oxidized CoenzymeQ (CoQ; aka quinone)
Complex 2 (Succinate-Q reductase): recall that when succinate is oxidized to fumarate in the Krebs cycle by the enzyme succinate dehydrogenase, FADH2 is generated → this FADH2 needs to be reoxidized by immediately passing its electrons to an Fe-S protein which funnels them into the oxidized form of CoQ (very similar to what happens in Complex 1), allowing the regeneration of FAD
At the end of the Fe-S complex (found in both Complex 1 and 2), there is a quinone / CoQ (coenzyme Q) that collects all of the electrons from the various substrates into one pocket, becoming CoQH (ubiquinol) → we need to reoxidize CoQ now
– Nomenclature: reduced quinone is dihydroquinone, oxidized quinone is just quinone → BUT reduced CoQ is ubiquinone and oxidized CoQ is ubiquinol
Complex 3 (Cytochrome Reductase): contain cytochrome (b and c) and an Fe-S protein
- As CoQH2 transfers one electron at a time to an Fe-S protein in the complex, it is converted to CoQH· (semiquinone) and will react w the reduced cytochrome b (Cyt b2+) to give CoQH2 and the oxidized form of cytochrome b (Cyt b3+)
- Cyt b3+ can then oxidize another molecule of CoQH· to CoQ
- The electrons are eventually passed to the reduced form of cytochrome c
Complex 4 (Cytochrome Oxidase, an enzyme): consists of two heme groups (heme a and heme a3) which each have a copper atom associated w it
- Copper atoms can alternate btwn +1 and +2 oxidation states
- Electrons are passed from cyt c to heme a to heme a3 then to oxygen, where the transfer of four electrons to molecular reduction leads to its reduction into two molecules of water
- ** this is the only step that actually requires oxygen
cytochromes
aka electron carriers; electron transporting proteins that contain a heme prosthetic group w an iron atom (alternating btwn Fe2+ and Fe3+)
- —- Cyt b acts as the go-btwn that allows interactions btwn CoQH and Fe-S to occur
- —- Cyt c has an iron atom of the heme group bonded to a sulfur atom of a Met residue on one side and nitrogen atom on the other side
