BIOC 2300 > Midterm 2 > Flashcards

Midterm 2 Flashcards

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1
Q

Which enzyme catalyzes glucose phosphorylation?

A

Hexokinase

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2
Q

Is the active site on an enzyme or on its substrate?

A

Enzyme

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3
Q

Direction of a reaction is indicated by __, while reaction speed is dependent on __

A

Free energy change, activation energy

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4
Q

What are coenzymes?

A

an enzyme cofactor that is necessary to certain enzymes but loosely bound

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5
Q

Where is an enzyme’s active site?

A

Buried deeply within the enzyme, only accessible to small reactants

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6
Q

Describe the difference between a unimolecular and bimolecular reaction

A

unimolecular reaction’s velocity is dependent on the concentration of one substrate, bimolecular reaction’s velocity is dependent of concentration of two substrates

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7
Q

What is the Michaelis constant?

A

The concentration of the substrate when the velocity is 50% of its maximum

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8
Q

Kcat/ Km measures what?

A

Enzyme efficiency

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9
Q

An enzyme’s preferred substrate will have the highest __ value

A

kcat / km

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10
Q

The two most important parameters of an enzyme are __ and __

A

Vmax and Km

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11
Q

Enzyme inhibitors prevent __

A

Enzyme catalysis

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12
Q

__ inhibitors are irreversible

A

Covalent

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13
Q

__ inhibitors bind to the enzyme active site in the place of the __, increasing enzyme __ and not changing __

A

Competitive, substrate, Km, Vmax

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14
Q

__ inhibitors bind to the enzyme not at the active site, affecting the enzyme in an __ manner, lowering __ and not affecting __

A

non-competitive, allosteric, Vmax, Km

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15
Q

__ inhibitors bind to a non-active site of an enzyme, reducing __ and increasing Km

A

Mixed, Vmax, Km

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15
Q

__ enzymes have a quaternary structure, showing cooperativity (analogous to myoglobin and hemoglobin) and can have a positive or negative __

A

allosteric, allostery

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15
Q

allosteric __ may inhibit or activate enzymes, and are used to control metabolic pathways

A

effectors

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16
Q

Lipids are __genous, hydro__, (amphipathic), and thus __

A

hetero, phobic, insoluble

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16
Q

The major structural lipid classifcations are __, while the functional lipid classifications are __

A

fatty acids, Triacylglycerols, phospholipids, Isoprenoids/steroids, glycolipds, then, cellular structures, energy storage, bioactivity

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17
Q

__ double bonds produce a bend in the fatty acid chain, while __ double bonds result in a linear chain

A

cis, trans

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18
Q

most human fatty acids are esterified to __ or __, or are bound to __ in blood

A

cholesterol, glycerol, albumin

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18
Q

Tell me about Triacylglycerols

A

Triacylglycerols consist of 3 fatty acids estrified to glycerol, found in circulating lipoproteins or insoluble lipid droplets, can be hydrolyzed to release free fatty acids and glycerol for delivery to other tissues, major energy reserve in body

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19
Q

__ are esters of 3-glycerophosphate, two fatty acids, polar headgroup, precursors of lipid second messagers, headgroups vary a lot

A

phospholipids

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20
Q

__ and __ contain sphingosine backbone, signaling / recognition roles, abundant in brain

A

glycosphingolipids and sphingomyelin

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21
tell me about cholesterol
humans excrete (don’t degrade) it, it is important for maintaining lipid bilayer fluidity, highly insoluble and must be transported in lipoproteins, imbalances cause antherosclerosis and vascular diseases
22
__ and __ are packaged as lipoproteins when in circulation to allow for transport
TAGs and cholesterol
23
lipid bilayer contains mainly __ and __
lipids and proteins
24
lipid composition is different in __ and __ membrane leaflets because they don't normally "flip flop"
inner and outer
25
__ fats don't pack together well because of __ due to __ bonds
unsaturated, bends in the fatty acid chain, cis
26
membrane fluidity increases with __, decreases with __
degree of fatty acid chain unsaturation, FA chain length
27
__ proteins are associated w/ lipid bilayer via non-polar interactions, require detergents, can span bilayer as a-helices or b-barrels while __ proteins are associated w/ membrane surface via electrostatic contracts
integral, peripheral
28
nucleic acids are made from series of nucleotide triphosphates, one is __
deoxyadenosine triphosphate (ATP without an O)
29
Double Helix (B) form consists of two nucleotide __ strands, base pairs in __, perpendicular to __ axis, __ exterior and __ interior, formed by __ bonds between bases
polymer, middle, helix, polar, non-polar, hydrogen
30
Melting temp. of DNA increases with __ content, because these pairs contain 3 H bonds instead of 2
G-C pair
31
what is the central dogma of life
(replication) dna-> (transcription) rna -> (translation) protein
32
replication requires unwinding of DNA by __, __ anneal to regular positions on DNA, __ synthesizes complementary strands from each primer
helicase, RNA primers, DNA polymerase
33
most genes are regulated at the __ stage
transcription
34
rna and dna differences?
rna like dna but contains 2’ hydroxyl on sugar, U replaces T, single strand can adopt base-paired folded structure
35
what are some causes for genome sequence variability
SNPs, VNTRs, insertions, deletions, translocations, mutations
36
mutations can be __ or __
point (silent, missense, nonsense, non-coding) or frameshift (addition / deletion of nucleotides, changes whole script)
37
talk about ribosomes
large organelle w/ two parts, made from protein and rnas, ribosome catalyzes formation of peptide bonds between amino acids carried by trnas as it moves along mrna from 5’ to 3’ end, results in growing peptide chain w/ amino acid residues corresponding from 5’-3’ sequence
38
define trna
clover-shaped rna carrying specific amino acid and anticodon pairing with mrna
39
what is transthyretin amyloidosis?
protein folds incorrectly and forms amyloid structure, interfering w several organs (particularly heart), can be fatal, treated by small inhibiting rna and antisense rna
40
go ahead and tell me about carbs.
Carbohydrates are the most abundant biomolecule in nature, wide variety of cellular functions, direct link btwn solar energy and chemical bond energy
40
how to convert linear structure to cyclic?
to convert linear to cyclic, right side goes down
41
how does cyclization occur in monosaccharides?
linear form of glucose becomes cyclic when C5 OH attacks C1, results in intramolecular hemiacetal or hemiketal, monosaccharides form 5-member rings (4C 1 O) or 6 member rings, furan has O at top and Pyran has O top right, new chiral centre forms at C1
41
tell me about monosaccharides
Monosaccharides distinguished from one another according to number of carbons, simplest contain 3C, up to 9C, monosaccharides can occur in D and L forms (most are D
42
pyranose ring is not planar, can adopt __ or __ position. stability of two forms depends on __
boat, chair, substituent positions on rings
43
With cyclization, carbonyl C becomes __ and there are two __ (a and B), in the a form, OH at C1 is on __ side of sugar from C6, for D sugars, in a anomer, H is __ at C1, in the B form, OH is on __ side of sugar as C6 (CH2OH), in other words, in D sugars, OH is __ and H is __
asymmetric, anomers, opposite, up. Same, up, down
44
a and B forms of __ are readily interconverted in __ environments, this process is called __
monosaccharides, aqueous, mutarotation
45
Mutarotation produces __ mixture of a and B forms in both __ and __ ring structures, open chain form can participate in __ reactions
equilibrium, furanose, pyranose, redox
46
__ can reduce compounds such as benedict's reagent, requires open chain with __, all aldoses are __ as well due to __
reducing sugars, aldehyde, reducing sugars, isomerization
47
common monosaccharides?
glucose, fructose, galactose (synthesizes important biomolecules like lactose, glycolipids, phospholipids, proetoglycan, and glycoproteins)
48
-hemicetals and hemiketals at __ carbon of a cyclic sugar react with __ to form corresponding __ and __, new linkage is a __ linkage and the compound is a __
anomeric, alcohols, acetal, ketal, glycosidic, glycoside
49
__ is two monosaccharides linked by a glycosidic bond (covalently linked), __ is saccharide polymers containing up to about 15 units, __ is greater than 15 units, __ are oligo or poly saccharides with single kind of sugar monomers, __ are oligo or polysaccharides containing more than one kind of sugar monomer
disaccharide, oligosaccharide, polysaccharide, homoglycans, heteroglycans
50
cellulose is main component of plant cell walls, forms strong structural polymer with h bonds, humans can’t digest __ glycosidic bond between glucose units, for us this is __
B(1->4), fiber
51
starch is formed of amylose (unbranched) and amylopectin (branched), major glycosidic bond of amylose is __, starch is stored in cytoplasm of plant cells, can assemble into compact helical structure, forms amylose and amylopectin. Humans can cleave __ bond between glucose units in a-amylose, with the enzyme amylase, so for us, starch is a source of __
a(1->4), a(1->4), glucose
52
3 sources of blood glucose and problems / lack thereof?
diet (sporadic), gluconeogenesis (slow), glycogen degradation (rapid and effective)
53
glycogen has one __ end, where anomeric carbon – O bond can open to form reactive __, due to __, glycogen has multiple __ ends where __ can be __
reducing, aldehyde, branching, non-reducing, glucose, released
54
four steps of glyconeogenesis?
-release of terminal glucoses as glucose-1-phosphate by the action of glycogen phosphorylase, removes glucose units from non-reducing ends of a glycogen molecule by cleaving a(1-4) bond formed by terminal glucose, releasing one glucose-1-phosphate -glycogen phosphorylase will continue to cleave successive glucose residues until it reaches poition 4 units away from branch, then debranching enzyme rearranges structure. this enzyme transfers last 3 glucose residues approaching branch point and then cleaves the sole a(1-6) bond to complete branched chain removal -glycogen breakdown releases glucose-1-phosphatase, however, entry of glucose into glycolysis requires glucose-6-phosphate. Phosphoglucomutase catalyzes conversion of g-1-p to g-6-p. -glycogen breakdown in liver can raise glucose levels in blood, requiring release of glucose from g-6-p by enzyme g-6-p-ase in endoplasmic reticulum, resulting glucose in endoplasmic reticulum can then be transported back into cytosol by T2 glucose transporter, then out of hepatocyte into blood by cell membrane glucose transporter GLUT2.
55
when blood glucose is low, the liver releases __ and blood glucagon levels __. in a fight-or-flight response, __ levels rise.
glucose, rise, epinephrine
56
what is epinephrine's relationship with glycogen?
epinephrine stimulates glycogen degradation and inhibits glycogen synthesis. it is the only hormone affecting muscle glycogen degradation.
57
__ amplify the effects at every step, (epinephrine binding to its receptor for example), so when __ needs to rise, it can happen very quickly (cascade)
hormones, blood sugar
58
four steps of glycogenesis?
glucose is activated by UTP to form UDP-glucose -glycogenin generates an 8-glucose-unit primer (glucose transferred from UDP-glucose to Tyr194 residue of glycogenin) -glycogen synthase is responsible for chain elongation -glycogen-braching enzyme generates branches in growing glycogen structure
59
Glucokinase has high Km, leads to allosteric activation of __ and inactivation of __ via __ from g-6-p and glucose
glycogen synthase, glycogen phosphorylase, dephosphorylation
60
__ allosterically activates glycogen synthase, __ inhibit glycogen phosphorylase in the liver and muscle, __ activates glycogen phosphorylase in the muscle
g-6-p, g-6-p and atp, AMP
60
when glucose in blood is high, blood insulin levels __, insulin binding to its receptor leads to glycogen __
rise, synthesis
60
__ secreted into blood before meal, __ secreted into blood after meal in response to blood glucose spike
glucagon, insulin
61
glucagon enacts __, including __ glycogen synthesis, while insulin enacts __, including __ glycogen synthesis
phosphorylations, stopping, dephosphorylations, starting
62
tell me about a spontaneous reaction
exergonic, negative delta G, reaction proceeds in the forward direction
63
coupled reactions contain 2 reactions in which one has a __ that is a reactant in the other. with coupled reactions, __ is calculated in a net way
product, spontaneity
64
ATP hydrolysis (highly exergonic, favoured) can be used to drive endergonic reactions by reaction __
coupling
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