Human Biochem Exam 3 > Exam 3 > Flashcards

Exam 3 Flashcards

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1
Q

is more energy available from the digestion of carbohydrates or lipids and why?

A

lipids, carbs enter the oxidation chain at the second level while lipids enter around the first level. a lower oxidation state allows for more energy

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2
Q

types of lipids

A

fatty acids, triacylglycerols, glycerophospholipids, lipid quinones, cholesterol and steroid derivatives

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3
Q

all lipids are

A

amphipathic (polar head and non polar chain group)

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4
Q

saturated

A

single bonds, more tightly packed

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5
Q

unsaturated

A

double bonds, less tightly packed

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6
Q

low melting point (more liquid at room temp)

A

shorter C chain, increased unsaturation (double bonds). less tightly packed and fewer

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7
Q

high melting point

A

longer C chain, increased saturation (single bonds). tightly packed which causes fewer noncovalent interactions

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8
Q

olive oil

A

has long-chain unsaturated fatty acids with a low melting point

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9
Q

beef fat

A

greatest proportional of saturated fatty acids and a long C chain (high melting point)

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10
Q

fatty acid composition changes as a function of temperature

A

increased temperatures want it to move less to counteract increased fluidity due to increased Brownian motion. the ratio of unsaturated to saturated gets lower as temperatures increase and decrease double bonds to maintain fluidity.

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11
Q

which has a lower melting point 18:0 or 18:1

A

18:1

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12
Q

a triacylglycerol consists of fatty acids attached to one

A

glycerol

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13
Q

glycolipids

A

covalent linkage between lipid and glucose or galactose

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14
Q

steroids

A

ABCD ring

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15
Q

fluidity is controlled by membrane composition and cholesterol content

A

cholesterol prevents tight packing of chains and reduces transition between fluid and solid like (makes curve more straight)

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16
Q

lateral vs transbilayer diffusion

A

lateral moves very quickly across membrane to same leaflet. transbilayer is thermodynamically unfavored and moves from 1 leaflet to the other

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17
Q

what is a general feature of lipid bilayer in all biological membranes

A

individual lipid molecules are free to diffuse laterally in the bilayer

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18
Q

peripheral membrane proteins

A

on one side of the membrane or the other, have polar AAs

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19
Q

integral membrane proteins

A

span the lipid bilayer and have non polar AAs

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20
Q

increasing membrane permeability

A

Na, K, Cl, glucose, tryptophan, urea glycerol, indole, H2O. size and polarity are important (np and small is more easy)

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21
Q

simple diffusion

A

high concentration to low concentration. small and np molecule, unaided, only down concentration gradient

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22
Q

facilitated transport (passive transport)

A

aided by a protein, only down concentration gradient, high concentration to low concentration

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23
Q

primary active transport

A

movement of solute is against a gradient, energy provided by ATP hydrolysis

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24
Q

secondary active transport

A

2 solutes, 1 solute against concentration, coupled to primary transport

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25
c2/c1
c2 where it goes, c1 where it starts
26
membrane potential charge
final - initial (inside negative always)
27
ion channel
single gate, gate closed then open
28
transporter (alternating gates)
2 gates, one open one closed, then other opened other closed
29
GLUT1
causes conformational change that allows it to enter cell
30
how are enzymes similar to transport proteins
conformational changes, saturation kinetics, rate enhancement, specific
31
how are enzymes different to transport proteins
no chemistry
32
what happens when NaCl dissolves in water
water molecules orient so that O is near Na and H are near Cl
33
symport, antiport
same direction, different direction
34
how are ion selective channels different from transporters
ion channel rate is much much faster, channels are not saturable, and they are gated in response to cellular events
35
one way channels allow for specificity
changing the distance the molecule has to travel
36
B-adrenergic signalling pathway
1. epinephrine (1 messenger) binds to B-adrenergic receptor (7-TM GPCR) embedded in the membrane 2. GPD is initially bound (inactive) but primary messenger binding causes GDP-GTP swap (turned on) 3. GTP w a-subunit bound moves lateral across membrane to bind to and activate adenylate cyclase 4. adenylate cyclase activation causes ATP to convert to cAMP (2 messenger) which means it can now leave the membrane and diffuse into the cell 5. diffusion of cAMP into the cell allows it to activate PKA 6. activation of PKA then phosphorylates many substrate proteins
37
how is B-adrenergic pathway signal amplified
1 molecule of signal causes many phosphorylated proteins bc adenylate cyclase and PKA are enzymes and can repeat quickly. also if 2nd Ga subunit binds to GPCR in active conformation (while epinephrine is still bound)
38
how is B-adrenergic pathway terminated
1. epinephrine dissociation from GPCR 2. Ga dissociate from adenylate cyclase 3. intrinsic GTPase activity of Ga subunit 4. secondary messenger degredation 5. phosphatases that reverse kinase activity
39
a-adrenergic pathway
1. epinephrine binds to 7TM (GPCR) to activate a different G protein than B-adrenergic pathway, it activates Gaq 2. Gaq activates PLC (instead of adenylate cyclase) 3. PLC converts to DAG, IP3 and Ca (secondary messengers) 4. DAG IP3 and Ca diffuse and activates PKC
40
EGF pathway
dimerization and autophosphorylation - receptor is RTK and has 2 domains - EGF binds to RTK which causes 2 receptor domains to come together - cross phosphorylation happens and GTP-GDP swap activates Ras proteins
41
insulin signalling
-RTK exists as a dimer in the absence of insulin - insulin signals the fed state - insulin is the primary messenger - insulin RTK binding activated PI3K - PI3K forms PIP3 (2 messenger) - PIP3 activated PKB - PKB activation causes increased glucose uptake
42
most hydrolytic enzymes, particularly proteases, are synthesized in inactive forms called
zymogens, they are activated when needed by irreversible proteolytic cleavage
43
how does the acidic environment in the stomach aid in digestion
denatures proteins that facilitate hydrolysis of amide bonds, and activation of pepsinogen-- pepsin digests proteins into oligopeptides
44
initial digestion products stimulate the release of 2 hormones
secretin- promotes release of bicarbonate (a base) to naturalize the acid. CCK- promotes the release of pancreatic zymogens and bile salts
45
carbohydrate digestion
begins in the saliva, then a-amylase cleaves the a-1,4 bonds in starch, then glycosidases continue digestion
46
lipid digestion in the intestines
lipids aren't soluble in the same medium as the lipases (which are water soluble). emulsions are formed in the stomach by bile salts (which increase solubility). lipases degrade triacylglycerols which are products from soluble micelles. fatty acid binding proteins transport fatty acids and monoacylglycerol into the intestines. triacylglycerols are resynthesized then carried to adipose tissue and muscle in chylomicrons
47
anabolic
biosynthesis, biomolecules are synthesized from simpler components (condensation reactions)
48
catabolic
degradation, nutrients and cell constituents are broken down exergonically to 1. salvage their components 2. generate free energy
49
characteristics of all metabolic pathways
1. irreversible 2. catabolic and anabolic pathways must differ 3. has a first committed step 4. regulated
50
oxidation of C fuels
oxidation reactions release potential energy. occurs simultaneously with reduction. "activated carriers" of electrons are reduced
51
the lower the oxidation state
the higher the energy
52
oxidation states
1. high energy to low energy (catabolism) 2. low energy to high energy (anabolism)
53
metabolic reactions involving the breakdown of cellular fuels into cellular energy are referred to as
catabolic reactions
54
NADH is... NAD+ is
reduced form, oxidized form
55
add H2 to the reactants
reduction
56
add H2 to products
oxidation
57
in order to generate ATP you need
1,3-BPD, PEP, or creatine phosphate
58
the breaking of a high energy bond provides energy to
drive a reaction that would otherwise be unfavorable
59
how does breaking a high energy bond provide energy
1. increased resonance stabilization of products 2. reduction in repulsion of adjacent negative charges 3. hydration more favorable for products than for ATP
60
determining favorability
- if reactants and products have the same amount of HEB= near equilibrium - if reactants have HEB and products don't= thermodynamically favorable - if 0 HEB to 0 HEB= unfavorable - if 0 HEB to HEB's= unfavorable
61
what makes ATP a good energy source
1. thermodynamically unstable- energy can be derived from its hydrolysis 2. kinetically stable
62
how can we make a non-spontaneous reaction take place inside a cell
1. reaction coupling- manipulate concentrations of reactants and products to control the flux through a pathway. maintaining low product concentration is 1 way to control flux through a pathway 2. control the number of enzyme molecules- transcription/translation 3. control the activity of the enzyme through allosteric regulation and energy change 4. control the location of the enzyme
63
carbohydrate metabolism
starch broken down by a-amylase 1,4 enzyme, need a different enzyme to catalyze a-1,6, monosaccharides glucose is final product
64
oxidation of glucose
provides the energy to synthesize ATP
65
which steps of glycolysis use ATP
66
which steps of glycolysis generate ATP
67
what is the overall purpose of glycolysis
1. to provide energy as ATP 2. to provide biosynthetic intermediates
68
hexokinase reaction
hexokinase specificity= open clamp: active site not formed. glucose binds and the clamp closes. active site must keep water away from ATP. in the presence of xylose, hexokinase becomes an ATPase. relatively nonspecific- D-glucose, D-mannose, D-fructose. phosphorylation traps glucose inside cell.In the first reaction of glycolysis, the enzyme hexokinase rapidly phosphorylates glucose entering the cell, forming glucose-6-phosphate (G-6-P). As shown below, the overall reaction is exergonic; the free energy change for the reaction is -4 Kcal per mole of G-6-P synthesized.
69
PAK reaction
requires input of ATP to form ADP. replaces OH with OPO3(2-). this reaction is exergonic and is the committed step. In the second step of glycolysis, an isomerase converts glucose-6-phosphate into one of its isomers, fructose-6-phosphate. An isomerase is an enzyme that catalyzes the conversion of a molecule into one of its isomers. This change from phosphoglucose to phosphofructose allows the eventual split of the sugar into two three-carbon molecules. The third step is the phosphorylation of fructose-6-phosphate, catalyzed by the enzyme phosphofructokinase. A second ATP molecule donates a high-energy phosphate to fructose-6-phosphate, producing fructose-1,6-bisphosphate. In this pathway, phosphofructokinase is a rate-limiting enzyme. It is active when the concentration of ADP is high; it is less active when ADP levels are low and the concentration of ATP is high. Thus, if there is “sufficient” ATP in the system, the pathway slows down. This is a type of end product inhibition, since ATP is the end product of glucose catabolism
70
GAPDH reaction
The sixth step in glycolysis (Figure 3) oxidizes the sugar (glyceraldehyde-3-phosphate), extracting high-energy electrons, which are picked up by the electron carrier NAD+, producing NADH. The sugar is then phosphorylated by the addition of a second phosphate group, producing 1,3-bisphosphoglycerate. Note that the second phosphate group does not require another ATP molecule. Here again is a potential limiting factor for this pathway. The continuation of the reaction depends upon the availability of the oxidized form of the electron carrier, NAD+. Thus, NADH must be continuously oxidized back into NAD+ in order to keep this step going. If NAD+ is not available, the second half of glycolysis slows down or stops. If oxygen is available in the system, the NADH will be oxidized readily, though indirectly, and the high-energy electrons from the hydrogen released in this process will be used to produce ATP. In an environment without oxygen, an alternate pathway (fermentation) can provide the oxidation of NADH to NAD+.
71
what is the importance of triose phosphate isomerase
TPI deficiency is lethal. only enzyme in glycolysis that if you don't have gene for you die, because you produce 1/2 the amount of ATP.
72
how is oxidation coupled to phosphorylation
if oxidation took place and intermediate diffused, we'd lose energy. intermediate is in a low energy state so energy can be captured by the enzyme with the use of covalent catalysis.

Human Biochem Exam 3 (1 decks)

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