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ISBM > Exam #2 > Flashcards

Exam #2 Flashcards

1
Q

proteolytic

A

breaks long chains of amino acids

- aka protease, proteinase, peptidase

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2
Q

kinases

A 
phosphorylate molecules (add a phosphate group via covalent bond)
 - use high energy molecule, such as ATP (source of energy / phosphate)
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3
Q

phosphatases

A

enzymatically remove a phosphate group resulting in a phosphorylated protein
- hydrolytic cleavage: use H2O to cleave phosphate group resulting in de-phosphorylated enzyme and inorganic phosphate (HPO4 or H2PO4)

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4
Q

polyols

A

6-carbon sugars (hexoses)

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5
Q

glycogenolysis

A

breakdown of glycogen to G-6-P

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6
Q

transition state

A

alteration in bond structure to form new molecules

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7
Q

catalyst

A

reduces the magnitude of free energy change that must be introduced into the molecule to promote molecular change

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8
Q

Properties of enzymes

A

proteins
inc. velocity/rate; do not effect Km
not consumed
specific (rx type and isomer)

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9
Q

Properties of regulatory enzymes

A

subject to regulation

  • covalent (phosphorylation)
  • non-covalent (induced conformational change)

catalytic activity may be enhanced or reduced

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10
Q

main classes of enzymes

A

Oxidoreductases: move an e- from one substance to another (oxidation/reduction rxs)
o Oxidation: loss of an e- (A is being oxidized)
o Reduction: gain of an e- (B is being reduced)
Transferases: transfer group from one substance to another
Hydrolases: spit H2O into H+ and OH- resulting in hydroxylated B and protonated A
Lysases: create alterations in chemical structure
Isomerases: alters form that substance takes
Synthases: join molecules; tend to be most active when non-phosphorylated

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11
Q

active site

A

specific domain within an enzyme in which a specific reaction is favorable; catalytic activity will occur here!

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12
Q

isozyme

A

family of enzymes all of which are catalyzing the same rx, yet have different structures (ex. LDH)

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13
Q

regulation of enzymes

A

irreversible (partial proteolytic cleavage)
reversible
- covalent
- allosteric

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14
Q

irreversible regulation of enzymes

A

partial proteolytic cleavage; alters the structure of a protein and permanently changes enzyme activity

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15
Q

covalent regulation of enzymes

A

requires the physical addition of a group to the enzyme (e.g. phosphorylation)
- reversible

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16
Q

non-covalent regulation of enzymes

- allosteric enzymes

A

regulation occurs through transient, electrostatic reactions (e.g. hydrogen bonds) at site other than active site

  • allosteric modulation
  • does not alter Vmax
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17
Q

phosphorylation

A

type of covalent regulation involving addition of a phosphate group to an enzyme, causing it to experience a large change in activity

  • stimulatory or inhibitory
  • everywhere in intermediate metabolism
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18
Q

types of enzyme inhibition

A

reversible (all non-covalent bonding)

  • competitive
  • non-competitive

irreversible: destroy enzyme

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19
Q

competitive inhibition

A

substance with similar structure non-covalently associates with enzyme in active site and prevents substrate from binding

  • increases Km
  • does not change Vmax
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20
Q

non-competitive inhibition

A

non-covalent association with enzyme at site other than active site

  • can bind enzyme alone or ES complex
  • prevents those bond from forming product
  • no effect on Km
  • decrease Vmax
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21
Q

irreversible inhibition

A

covalent binding of inhibitor to active site, killing enzyme

- ex. penicillin (blocks enzyme responcible for cell wall formation)

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22
Q

determinants of rate of entry of enzymes into plasma

A

tissue destruction (physiological or pathological)
tissue mass
rate of enzyme synthesis

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23
Q

determinants of rate of removal of enzymes from plasma

A

inactivation: proteolytic degradation into amino acids
clearance: through kidneys

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24
Q

reasons for measuring plasma membranes

A

identify location of cellular / organ damage
determine extent of damage
provide prognostic information

PROBLEM: enzymes tend not to be tissue-specific

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25
Q

ways to improve tissue location (based on measurements of plasma enzymes)

A

measure multiple enzymes
measure enzymes isozymes
take serial measurements over time

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26
Q

cardiac enzymes / indicators

A

CK-MB
LDH - 1 and 2
troponins I and T

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27
Q

roles of plasma proteins

A 
maintenance of oncotic pressure
buffering
transport
humoral immunity
enzymes
protease inhibitors
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28
Q

onconic oressure

A

osmotic pressure due exclusively to proteins

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29
Q

catabolism / oxidative metabolism

A

breaking down energy-yeilding nutrients (carbohydrates, fats, proteins) to create energy (in the form of reducing power and ATP)

  • exergonic
  • oxidation: loss of an electron
30
Q

anabolism / reductive metabolism

A

use of products from oxidative metabolism as building blocks to turn simple precursor molecules (amino acids, sugars, fatty acids, nucleotide bases) into usable macromolecules

  • endergonic
  • reduction: gain of an electron
31
Q

enthalpy

A

thermodynamic potential; represents reduction state (more reduced = higher enthalpy = electrons can be removed)

32
Q

triphosphate compounds

A

serve as sources of metabolic free energy (e.g. ATP)

- hydrolysis of these compounds can be coupled with non-spontaneous rxs to make them spontaneous

33
Q

adenylate charge

A

state of a cell’s metabolic battery

  • normal cell = 0.93 (ATP prominent; can engage in anabolic rxs)
  • hepatocyte = 0.8 (high rate of metabolic activity / catabolic reactions; glycolysis)

Note: we are always replenishing and utilizing ATP, just one more than another depending on cell needs

34
Q

Gibbs free energy

A 
negative = spontaneous (Keq>1)
zero = equilibrium (Keq=1)
positive = non-spontaneous (Keq
35
Q

reciprocal regulation

A

simultaneous stimulation of activity in one pathway while inhibiting activity in the opposite (counterpart) pathway

  • very important to not be wasteful
  • creates net flux in 1 direction
36
Q

glucose homeostasis

A

maintaining reasonable stable concentrations of glucose in the ECF
- CNS and RBCs critically dependent on glucose as fuel source

37
Q

respiratory quotient (RQ)

A

ratio of the amount of CO2 produced over O2 consumed with the metabolism of a particular amount of nutrient (glucose, fatty acids, amino acid)

  • cells in most tissue = 0.8 (glucose main fuel, but combo)
  • CNS = closer to 1 (primarily glucose)

Note:

  • glucose only = 1
  • fatty acids only = 0.7
  • amino acids only = 0.8
38
Q

keto acids: where do they come from and how utilized (during fasting!)
- typically low in normal state

A

Liver: fatty acid degradation to acetyl CoA (beta oxidation)
• Keto acids are formed from acetyl CoA
• Acetyl CoA typically goes to TCA cycle, but when fasting there is a decreased insulin / glucose ratio and acetyl CoA spills over to produce keto acids
• Since hepatocytes have plenty of reducing power, pathway is driven from acetyl CoA to acetoacetate and B-hydroxybuterate (keto acids)

Muscles and CNS: use ketone bodies as fuel and metabolize them to acetyl CoA (in mitochondria) which feed into TCA cycle and e- transport chain = fuel production

39
Q

how hormones impact cells and the amount of impact they have

A

by associating with an integral membrane protein (receptor)

have a huge effect with a small amount of hormone due to 2nd message systems and other systems which result in high levels of phosphorylation

40
Q

hormone receptor characteristics

A

specific for ligand (hormone)
saturable
show high affinity for hormone (small circulating amount can promote response)
kinetics of ligand association vary: dose-response relationship

41
Q

hormone power

A

magnitude or size of the response

- independent of hormone conc.

42
Q

hormone potency

A

concentration required to give a response

  • depended on hormone conc.
  • can compare to Kd (dissociation constant) - lower Kd = more potent
43
Q

agonist (for a hormone receptor)

A

substance which associate with a receptor and promotes a specific response
- can be endogenous or pharmacologic

44
Q

antagonist (for a hormone receptor)

A

substance which associate with a receptor and promotes no response
- pharmacologic only

45
Q

up-regulation

A

increase number of hormone cell surface receptors due to prolonged, reduced circulating hormone conc.

46
Q

down-regulation

A

reduction in cell surface receptor number due to prolonged, increased circulating hormone conc.

47
Q

properties of second messengers

A

substances produced intracellularly in response to cell

surface hormonal stimulation
mediate the cellular response to hormones
- influence enzyme activity
- promote release of regulatory ions (free Ca+2)

transient in nature

48
Q

calmodulin (CaM)

A

modulates the regulatory roles of Ca+2

- CaM, bound by Ca+2, activates a protein

49
Q

glycolysis

A

central pathway for glucose catabolism (glucose to pyruvate)

  • spontaneous
  • generates 2ATP and 2NADH
50
Q

importance of conversion of pyruvate to lactate

A

occurs in reactions with and without oxygen

key to regenerate NAD+ for use as a cofactor in oxidizing step of glycolysis

dependent on NADH/NAD ratio

51
Q

glycogen

A

polymerized glucose; short-term storage form of glucose in animals

52
Q

glycogen synthesis and degradation (glycogenolysis)

A

synthesis from G-6-P to store glycogen in times of high adenylate charge or high plasma glucose levels

53
Q

pyrophosphate (PPi)

A

product formed, along with UDP-sugar

- has a very large free energy hydrolysis and its hydrolytic splitting drives the formation of UDP-sugar

54
Q

phosphoproteinphosphatase (PPPi)

A

enzyme that is phosphorylated as a result of increased insulin stimulation of tyrosine kinase receptors; its phosphorylation leads to de-phosphorylation of other regulator enzymes

55
Q

pentose phosphate pathway

A

Metabolic option for G-6-P
Results in:
- generation of NADPH - used for glutathione reduction / regeneration
- generation of an intermediate that produced RNA
- produces important glycolytic intermediates

56
Q

importance of glutathione

A

oxidation of this molecule (glutathione peroxidase) results in production of H2O from H2O2
- NADPH from pentose phosphate pathway used to convert oxidized glutathione to reduced state for further use

57
Q

gluconeogenesis

A

synthesis of glucose from non-hexose precursors

  • anabolic process
  • costly! biosynthetic rss coupled with ATP hydrolysis
  • very important in maintaining plasma glucose levels during fasting
  • only in liver and renal cortex
58
Q

Cori cycle

A

metabolic option for lactate (product of glycolysis; conversion from pyruvate)

  • lactate from muscles cells moves through MCTs into ECF and into cells of liver
  • converted to pyruvate (LDH) and undergoes gluconeogenesis to from glucose
  • overall: increases glucose conc in plasma
59
Q

adrenergic receptors

A 
class of G-protein coupled receptors that are targets for epic and nor-epi
 - there are alpha (NE) and beta receptors (E)
60
Q

epinephrine

A

hormone released from adrenal medulla

61
Q

norepinephrine

A

neurotransmitter

62
Q

epimer

A

only difference is the molecular configuration of the groups attached to one carbon

63
Q

epimerase

A

enzyme that changes the structure of an epimer

64
Q

importance of UDP-sugars

A

addition of UTP to sugar phosphate, resulting in UDP-sugar, is a critical charging mechanism through which many sugar enter metabolic pathways

  • formation of PPi (high free energy of hydrolysis) is what drives the formation of UDP-sugar
    • note: energy of hydrolysis higher than that of ATP
65
Q

Uses of UDP-Sugars (4)

A

glycogen production
glycoprotein prodcution
UDP-glucuronate (glucuronic acid) production: enhances water solubility of many substances
UDP-galactose production, leading to lactose production

66
Q

metabolism of galactose - general

A

galactose phosphorylated (galatokinase)
galactose-1-P altered to UDP-glucose (GALT and epimerase)
UDP-glucose to glucose-1-P (possible conversion to G-6-P, but galactose-1-P inhibits phosphoglucomutase so glycolysis less likely)

67
Q

galactosemia

A

accumulation of galactose in plasma resulting from in-born, autosomal recessive errors of metabolism (can occur at 3 pts. in pathway):

  1. classical: deficiency in GALT = high levels of galactose-1-phosphate (bad - hypoglycemia)
  2. non-classical: absence of galactokinase = high levels of galactose (not as bad)
  3. deficiency in epimerase (rare)
68
Q

clinical features of galactosemia

A

classical - hypoglycemia
cataracts (via polyol pathway - conversion of galactose to galactitol (enzyme = aldose reductase) which accumulates in lens
jaundice, hepatomegaly, liver disease, mental retardation, bacterial sepsis

69
Q

polyol pathway

A

synthesis of fructose from glucose (and other sugars)
occurs in liver; reversible pathway
glucose reduced to sorbitol (6-carbon polyol) (enzyme = aldose reductase; NADPH also needed)
sorbitol subject to oxidation to yield fructose

70
Q

metabolism of fructose - general

A

fructose converted to fructose-1-P (enzyme = fructokinase)
fructose-1-P is metabolized to two glycolytic intermediates that enter glycolysis after 2 regulatory steps
- insulin levels increase
- activate pyruvate kinase (de-phosphorylate)
- TCA cycle slows
- pyruvate and acetyl CoA shunted off to fatty acid production

why we have so many fat people
huge ATP sink (formation of uric acid)

71
Q

fructose intolerance

A

deficiency in adolase reductase causing accumulation of fructose-1-P and intolerance of digestion of fructose
- accumulation inhibits gluconeogenesis and glycogenolysis = hypoglycemia

ISBM (7 decks)

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