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MCAT > Biochem: Ch 12, 4 > Flashcards

Biochem: Ch 12, 4 Flashcards

1
Q

open system

A

matter and energy can be exchanged with the environment

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2
Q

closed system

A

only energy can be exchanged with the envrionment

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3
Q

no work is performed in a ___ system because

A

closed

pressure and volume remain constant

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4
Q

entropy

A

measure of energy dispersion in a system

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5
Q

ΔU =

A

Q - W

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6
Q

ATP

A

mid level energy molecule

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7
Q

ATP contains ____ that are stabilized upon …

A

high energy phosphate bonds that are stabilized upon hydrolysis by resonance, ionization, and loss of charge repulsion

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8
Q

ATP provides energy through

A

hydrolysis and coupling to energetically unfavorable reactions

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9
Q

ATP can participate in ____ as a _____

A

phosphoryl group transfers

phosphate donor

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10
Q

ATP is formed from

A

substrate-level phosphorylation and oxidative phosphorylation

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11
Q

ATP consists of

A

adenosine molecule attached to 3 phosphate groups

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12
Q

ATP is consumed through

A

hydrolysis or the transfer of a phosphate group to another molecule

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13
Q

what is the result of one phosphate group being removed from ATP?

A

adenosine diphosphate (ADP)

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14
Q

what is the result of two phosphate groups being removed from ATP?

A

adenosine monophosphate (AMP)

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15
Q

ATP hydrolysis is most likely to be encountered in the context of

A

coupled reactions

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16
Q

ATP cleavage

A

transfer of high energy phosphate group from ATP to another molecule

this activates or inactivates the target molecule

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17
Q

how does coupling with ATP hydrolysis alter the energetics of a reaction?

A

ATP hydrolysis yields about 30 kJ/mol of energy, which can be harnessed to drive other rxns forward

this may either allow a nonspontaneous reaction to occur or increase the rate of a spontaneous reaction

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18
Q

explain why ATP is an inefficient molecule for long term storage

A

intermediate energy storage molecule and not energetically dense

the high energy bonds and presence of significant change make it an inefficient molecule

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19
Q

long term storage molecules are characterized by

A

energy density

stable, nonrepulsive bonds

(primarily seen in lipids)

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20
Q

many redox reactions involve

A

electron carrier to transport high energy electrons

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21
Q

electron carrier can be either

A

soluble or membrane bound

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22
Q

flavoproteins

A

type of electron carrier

derived from riboflavin (vitamin B2)

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23
Q

high energy electron carrier exs

A

NADH, NADPH, FADH2, ubiquinone, cytochromes

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24
Q

equilibrium is an undesirable state for most biochemical reactions bc

A

organisms need to harness free energy to survive

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25
Q

postprandial (absorptive) state

A

aka well fed

insulin secretion is high and anabolic metabolism prevails

observed in short term fasting (overnight)

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26
Q

prolonged fasting

A

aka starvation

increase glucagon and catecholamine (epinephrine) secretion

at max, 2/3 of brain’s energy can be derived from ketone bodies

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27
Q

anabolism

A

synthesis of biomolecules

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28
Q

catabolism

A

breakdown of biomolecules for energy

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29
Q

types of cells that are insensitive to insulin

A

nervous tissue and red blood cells

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30
Q

counterregulatory hormones

A

oppose the actions of insulin

act on skeletal muscles, adipose tissue, liver

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31
Q

counterregulatory hormones ex

A

glucagon, cortisol, epinephrine, norepinephrine, growth hormone

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32
Q

what tissue is least able to change its fuel source in periods of prolonged starvation?

A

cells that rely solely on anaerobic respiration are least adaptable to different energy sources

ex: red blood cells - stay reliant on glucose

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33
Q

during what stage is there the greatest decrease in the circulating concentration of insulin?

A

postabsorptive state

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34
Q

effects of insulin on metabolism

inc vs dec

A
  • dec in blood glucose levels by increasing cellular uptake
    • dec: triaglycerol breakdown in adipose tissue, formation of ketone bodies by liver
  • inc rate of anabolic metabolism
    • inc: glucose and triacylglycerol uptake by fat cells, lipoprotein lipase activity, triacycglycerol synthesis
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35
Q

insulin secretion by _____ is regulated by _____

A

pancreatic beta cells

blood glucose levesl

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36
Q

effects of glucagon on metabolism

A

inc blood glucose levels by promoting gluconeogenesis and glycogenolysis in liver

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37
Q

glucagon secretion by _____ is stimulated by _____

A

pancreatic alpha cells

low glucose and high amino acid levels

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38
Q

effect of glucocorticoids on metabolism

A

inc blood glucose in response to stress by mobilizing fat stores and inhibiting glucose uptake

inc the impact of glucagon and catecholamines

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39
Q

effect of catecholamines on metabolism

A

inc glycogenolysis in liver and lipolysis in adipose tissue

inc basal metabolic rate through their sympathetic nervous system activity

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40
Q

effect of thyroid hormones on metabolism

A

module the impact of other metabolic hormones

inc basic metabolic rate

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41
Q

T3 and T4

A

T3 is more potent than T4, but has a shorter half life and is available in lower conc in the blood

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42
Q

T__ is converted to T__ in the ___

A

T4

T3

tissues

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43
Q

insulin is a ___ hormone

A

peptide

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44
Q

thyroid hormones are ___ hormones

A

amino acid derivative

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45
Q

cortisol is a ___ hormone

A

steroid

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46
Q

glucose is absorbed by ___ via ___

A

peripheral tissues

facilitated transport mechanisms that utilize glucose transporters located in cell membrane

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47
Q

effect of cortisol on metabolism

A

inc lipolysis and amino acid mobilization

dec glucose uptake in certain tissues

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48
Q

hepatocytes

A

maintenance of blood glucose levels by glycogenolysis and gluconeogenesis in response to pancreatic hormone stimulation

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49
Q

liver function

A

processing of lipids and cholesterol, bile, urea, and toxins

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50
Q

adipose tissue stores __ under the influence of ___ and releases them under the influence of ___

A

lipids

insulin

epinephrine

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51
Q

skeletal muscle metobolism

A

differes based on current activity level and fiber type

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52
Q

resting muscle metabolism

A

conserves carbs in glycogen stores

uses free fatty acids from bloodstream

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53
Q

active muscle metabolism

A

may use anaerobic metabolism, oxidative phosphorylation of glucose, direct phosphorylation from creatine phosphate, or fatty acid oxidation

depending on fiber type and exercise duration

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54
Q

cardiac muscle metabolism

A

uses fatty acid oxidation in both wwell fed and fastin gstates

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55
Q

brain and nervous tissue metabolism

A

consume glucose in all metabolic states except for prolonged fasts, where it comes from ketone bodies

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56
Q

chylomicrons

A

carry triacyglycerols absorbed from gut

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57
Q

creatine phosphate

A

transfers a phosphate group to ADP to form ATP

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58
Q

what is the preferred fuel for most cells in the well fed state? what is the exception and its preferred fuel?

A

preferred: glucose
exception: cardiac muscle - prefers fatty acid

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59
Q

metabolic rates can be measured using

A

calorimetry, respirometry, consumption tracking, or measurement of blood conc of substrates and hormones

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60
Q

respiratory quotient (RQ)

A

estimated composition of fuel that is actively consumed by the body

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61
Q

hormones that play a role in body mass

A

leptin, ghrelin, orexin

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62
Q

long term changes in body mass result from changes in

A

lipid storage

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63
Q

what must happen for weight change?

A

changes in consumption or activity must surpass a threshold

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64
Q

the threshold is ___ for weight gain than for weight loss

A

lower

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65
Q

calorimeters

A

measure basal metabolic rate (BMR)

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66
Q

orexin

A

increase appetite

involved in alterness and sleep wake cycle

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67
Q

ghrelin

A

increases appetite

stimulates secretion of orexin

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68
Q

leptin

A

decreases appetite by suppressing orexin production

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69
Q

how is the respiratory quotient expected to change when a person transitions from resting to brief exercise?

A

as a person begins to exercise, the proportion of energy erived from glucose increases

this transition to almost exclusively carb metabolism will cause the respiratory quotient to approach 1

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70
Q

True or False? Coupled reactions tend to occur simultaneously.

A

True. Coupled reactions tend to occur simultaneously.

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71
Q

ATP has three phosphate groups directly next to one another. What about this structure makes ATP a high-energy molecule?

A

Phosphate groups are very negatively charged, and negatively charged groups do not want to be next to each other. This is a high-energy situation.

Think about it like two similar charges being next to each other. The closer the charges, the higher the electric potential energy. As these charges separate, the high amount of electric potential energy is converted into kinetic energy.

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72
Q

If ATP hydrolysis has a very negative ∆G value, why doesn’t ATP hydrolyze spontaneously all the time? How is our body able to control when ATP hydrolysis occurs?

A

Although ATP hydrolysis has a very negative ∆G value, the reaction has a very high activation energy (Ea). When an enzyme is used in conjunction with ATP, the Ea is lowered, allowing the reaction to occur. This way, reactions with ATP will primarily occur only in the presence of the needed enzyme.

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73
Q

Which of the following are also names for the Absorptive State?

I. Postprandial State
II. Well-Fed State
III. Counterregulatory State

(A) I only
(B) I and II only
(C) II and III
(D) I, II and III

A

(B) I and II only

The Absorptive State can also be called the Well-Fed State and the Postprandial State.

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74
Q

Adipose Tissue can receive which of the following for subsequent energy storage?

I. Triglycerides
II. Fatty Acids
III. Glucose

(A) I Only
(B) I and II Only
(C) II and III Only
(D) I, II, and III

A

(D) I, II, and III

Adipose Tissue can receive Triglycerides from VLDLs. It can also receive glucose, which it will then convert into Fatty Acids and subsequently Triglycerides.

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75
Q

Mike just ate a big Thanksgiving feast. Which state is Mike likely in?

(A) Absorptive
(B) Post-absorptive
(C) Excretion
(D) Filtration

A

(A) Absorptive

The absorptive state is also known as the “well-fed state” and is characterized by energy storage.

The Post-absorptive State is also known as the “fasting state” and is characterized by energy utilization.

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76
Q

How long after the last meal would it take to transition from the Postabsorbtive “Fasting state” to the Prolonged Fasting “Starvation” state?

(A) 1 day
(B) 1 hour
(C) 12 hours
(D) 3 days

A

(A) 1 day

After 1 day (24 hours) since the last meal, the Starvation State will start.

77
Q

The Absorptive State is most closely associated with _____________. The Post-absorptive State is closely associated with ___________.

(A) catabolism, catabolism
(B) catabolism, anabolism
(C) anabolism, anabolism
(D) anabolism, catabolism

A

(D) anabolism, catabolism

The Absorptive State is most closely associated with anabolism (macronutrient storage). The Post-absorptive State is closely associated with catabolism (macronutrient breakdown).

78
Q

Insulin will be released in periods of ______________, and glucagon will be released in periods of ___________.

(A) hypoglycemia, hypoglycemia
(B) hypoglycemia, hyperglycemia
(C) hyperglycemia, hyperglycemia
(D) hyperglycemia, hypoglycemia

A

(D) hyperglycemia, hypoglycemia

Insulin will be released in periods of hyperglycemia, and glucagon will be released in periods of hypoglycemia.

79
Q

Insulin causes glucose ___________, and glucagon causes glucose _____________.

(A) storage, storage
(B) storage, release
(C) release, release
(D) release, storage

A

(B) storage, release

Insulin causes glucose storage, and glucagon causes glucose release.

80
Q

Insulin will stimulate:

Gluconeogenesis or Glycolysis?
Glycogenesis or Glycogenolysis?
Lipogenesis or Lipolysis?

A

Insulin will stimulate:

  • Glycolysis
  • Glycogenesis
  • Lipogenesis
81
Q

After Insulin has stimulated Lipogenesis in the liver, how are the Fatty Acids stored?

(A) They are converted to Triacylglycerols and stored in the liver.
(B) They are converted to Triacylglycerols and released into the blood as VLDL.
(C) They are converted to Triacylglycerols and released into the blood as LDL.
(D) They are converted to Triacylglycerols and released into the blood as HDL.

A

(B) They are converted to Triacylglycerols and released into the blood as VLDL.

Triacylglycerols are often called Triglycerides, and VLDL stands for Very Low Density Lipoprotein.

82
Q

Glucagon will stimulate:

Gluconeogenesis or Glycolysis?
Glycogenesis or Glycogenolysis?
Lipogenesis or Lipolysis?

A

Glucagon will stimulate:

  • Gluconeogenesis
  • Glycogenolysis
  • Lipolysis
83
Q

Compare the cause of Type I versus Type II Diabetes.

A

Type I Diabetes results from an inability of the pancreas to produce insulin. This usually occurs early on in life.

Type II Diabetes results from desensitized insulin receptors and usually occurs later in life.

84
Q

Although we know relatively little regarding the mechanism of glucagon release from α-cells, we do know that it is triggered by:

(A) Glucose
(B) Glycogen
(C) Lipids
(D) Amino Acids

A

(D) Amino Acids

Although we know relatively little regarding the mechanism of glucagon release from α-cells, we do know that it is triggered by amino acids.

85
Q

Samantha is also really hungry. What hormone will tell her hypothalamus that her stomach is empty?

(A) Insulin
(B) Glucagon
(C) Leptin
(D) Ghrelin

A

(D) Ghrelin

Ghrelin is produced when your stomach is “growling.”

86
Q

Which of the following are Catecholamines and Counterregulatory Hormones?

I. Epinephrine
II. Noradrenaline
III. Cortisol

(A) I only
(B) I and II only
(C) I and III only
(D) II and III only

A

(B) I and II only

Epinephrine/Adrenaline and Norepinephrine/Noradrenaline are Catecholamines and Counterregulatory Hormones.

87
Q

carbohydrates are organized by

A

number of carbon atoms and functional groups

88
Q

trioses

A

3 carbon sugars

89
Q

tetroses

A

4 carbon sugars

90
Q

aldoses

A

sugars with aldehydes as most oxidized group

91
Q

ketoses

A

sugars with ketones as their most oxidized group

92
Q

nomenclature is based on

A

D and L forms of glyceraldehyde

93
Q

D-sugars

A

sugars with highest numbered chiral carbon with the OH group on right (in Fischer projection)

94
Q

L-sugars

A

sugars with highest numbered chiral carbon with the OH group on left (in Fischer projection)

95
Q

D and L forms of the same sugar are

A

enantiomers

96
Q

diasteriomers

A

non superimposable configurations of molecules with similar connectivity

differ by at least one, but not all, chiral carbons

include epimers and anomers

97
Q

epimers

A

subtype of diasteromers

differ at exactly one chiral carbon

98
Q

anomers

A

subtype of epimers

differ at anomeric carbon

99
Q

glyceraldehyde

A

simplest aldose

100
Q

numbering of carbons in monosaccaride

A

carbonyl carbon most oxidized - lowest number

101
Q

aldehyde carbon of sugar can participate in

A

glycosidic linkages

102
Q

glycosyl residues

A

sugars acting as substituents via glycosidic linkages

103
Q

dihydroxyacetone

A

simplest ketone sygar

104
Q

numbering of carbons in aldose

A

aldehyde carbon is number 1

105
Q

numbering of carbons in ketose

A

carbonyl carbon is C2

106
Q

D-fructose

107
Q

D-glucose

108
Q

D-galactose

109
Q

D-mannose

110
Q
A

D-fructose

111
Q
112
Q
A

D-galactose

113
Q
114
Q

optical isomers

A

aka stereoisomers

compounds that have the same chemical formula, differ in terms of spatial arrangement of comoobent atoms

115
Q

absolute configuration

A

3D arrangement of the groups attached to the chiral carbon

116
Q

D-isomers are equivalent with (__)

117
Q

L-isomers are equivalent with (__)

118
Q

as the number of chiral carbons increases, so does the number of

A

possible stereoisomers

119
Q

number of steroisomers with common backbone =

A

2n

n = number of chiral carbons

120
Q

D-glyceraldehyde determined to exhibit a ___ rotation

121
Q

D-glyceraldehyde determined to exhibit a ___ rotation

122
Q

how is direction of rotation determined

A

experimentally

123
Q

fischer projection

horizontal lines

A

wedges - go out of page

124
Q

fischer projection

vertical lines

A

dashes - into page

125
Q

carbs

enantiomers

A

same sugars in different optical families

ex: D glucose and L glucose

126
Q

carbs

diasteromers

A

sugars that are in same family (both are either ketoses or aldoses and have same number of carbons) that are not identical and are not mirror images of each other

127
Q

carbs

epimers ex

A

D-ribose and D-arabinose - differ at C2

128
Q

carbs

cyclization

A

ring formation of carbs

129
Q

when rings form, ___ carbon can take on either a ___ or ___ conformation

A

anomeric

alpha or beta

130
Q

cyclization

anomeric carbon

A

new chiral center formed in ring closure

was the carbon containing the carbonyl in straight chain form

131
Q

alpha-anomers

A

have -OH on anomeric carbon trans to the free -CH2OH group (axial and down)

132
Q

beta-anomers

A

have the -OH on the anomeric carbon cis to the free -CH2OH group (equatorial and up)

133
Q

Haworth projections

A

provide a good way to represent the 3D structure of cyclic compounds

134
Q

cyclic compounds can undergo

A

mutarotation

135
Q

mutarotation

A

cyclic compounds shift from one anomeric form to another with the straight chain form as an intermediate

136
Q

mutarotation results in

A

mixture that ontians both alpha and beta anomers at equilibrium conc

137
Q

is alpha or beta anomeric conformation favored in solution?

A

alpha anomeric configuration is less favoried bc hydroxyl group of anomeric carbon is axial, adding to the steric strain of the molecule

138
Q

monosaccarides

A

single carbohydrate units, with glucose as the most commonly observed monomer

139
Q

monosaccharides can udnergo 3 main rxns:

A

redox, esterification, glycoside formation

140
Q

aldoses can be oxidized to

A

aldonic acids

141
Q

aldoses can be reduced to

142
Q

sugars that can be oxidized are

A

reducing agents/sugars

143
Q

reducing sugars can be detected by reacting with

A

Tollens’ or Benedict’s reagents

144
Q

reducing sugars

A

sugars that can be oxidized

145
Q

deoxy sugars

A

sugars with a -H replacing an -OH group

146
Q

sugars can react with carboxylic acids and their derivatives, forming

147
Q

sugar esterification

A

when sugars react with carboxylic acids and their derivatives to form esters

148
Q

phosphorylation

A

phosphate ester is formed by transferring a phosphate group from ATP onto a sugar

149
Q

glycoside formation

A

basis for building complex carbs

requires the anomeric carbon to link another sugar

150
Q

aldonic acids

A

oxidized aldoses

151
Q

lactone

A

cyclic ester with carbonyl group on anomeric carbon

152
Q

tollens’ reagent

A

used to detect the presence of reducing sugars

silver oxide dissolved in ammonia - [Ag(NH3)2]+

produces a silvery mirror when aldehydes are present

153
Q

benedict’s reagent

A

used to detect the presence of reducing sugars

turns into red precipitate of Cu2O

154
Q

tautomerization

A

rearrangement of bonds in a compound, usually by moving a hydrogen and forming a double bond

155
Q

enol

A

compound with a double bond and an alcohol group

156
Q

alditol

A

when the aldehyde group of an aldose is reduced to an alcohol

157
Q

hemiacetals react with alcohols to form

158
Q

glycosidic bonds

A

C-O bonds when acetals are made

159
Q

furanosides

A

glycosides derived from furanose rings

160
Q

pyranosides

A

glycosides derived from pyranose rings

161
Q

breaking a glycosidic bond requires

A

hydrolysis

162
Q

disaccharides form as a result of

A

glycosidic bonding between two monosaccharide subunites

163
Q

polysaccharides form by

A

repeated monosaccharide or poly saccharide glycosidic bonding

164
Q

sucrose

165
Q

lactose

166
Q

maltose

167
Q

cellulose

A

polysaccharide

main structural component for plant cell walls

main source of fiber in human diet

168
Q

starches

A

polysaccharide

main energy storage form for plants

ex: amylose and amylopectin

169
Q

starches ex

A

amylose and amylopectin

170
Q

glycogen

A

polysaccharide

main energy storage form for animals

171
Q

homopolysaccharides

A

polysaccharide composed of the same monosaccharide

172
Q

heteropolysaccharide

A

polymer made up of more than one type of monosaccharide

173
Q
174
Q
175
Q
176
Q

Draw or visualize D-glucose versus D-fructose. These two compounds are considered:

(A) diasteriomers
(B) epimers
(C) constitutional isomers
(D) enantiomers

A

(C) constitutional isomers

These two compounds are considered constitutional isomers because they have the same molecular formula with different connectivity.

D-glucose is an aldose, while D-fructose is a ketose.

177
Q

Which of the following statement(s) is true of a diastereomers?

I. They have similar physical properties
II. They have different physical properties
III. They have similar chemical/biological properties
IV. They have different chemical/biological properties

(A) I and III Only
(B) II and IV Only
(C) I Only
(D) III Only

A

(B) II and IV Only

Diastereomers are molecules that are different from each other in terms of their physical and chemical/biological properties.

178
Q

True or False? A sugar monomer in the D configuration will rotate plane-polarized light to the right.

A

False. Sugar monomers in the D configuration will sometimes rotate plane polarized light to the right and sometimes rotate it to the left. The D/L configuration has no correlation to the direction the compound will rotate plane polarized light.

179
Q

Draw or visualize D-glucose versus D-mannose. These two compounds are considered:

(A) diasteriomers
(B) epimers
(C) constitutional isomers
(D) enantiomers

A

(B) epimers

These two compounds are considered epimers because they have the opposite stereochemistry designation (R/S) at a single stereocenter.

180
Q

How many possible D-aldohexoses are there?

(A) 4
(B) 6
(C) 8
(D) 16

A

(C) 8

An aldohexose has 4 chiral centers. You can calculate the possible number of configurations using the formula 2^n where n is the number of stereocenters. 2^4 is 16, so there are 16 possible aldohexoses (8 D-aldohexoses and 8 L-aldohexoses).

181
Q

Fill in the blank: Knowing that any specific Aldohexose has 4 chiral centers, it will have __________ enantiomer(s) and __________ diastereomer(s).

(A) 2 , 5
(B) 2 , 14
(C) 1 , 6
(D) 1 , 14

A

(D) 1 , 14

Knowing that Aldohexoses have 4 chiral centers, they can have 1 enantiomer and 14 diastereomer(s).

Note that any molecule can only have one Enantiomer, and that one of the 16 possible Aldohexoses is the original Aldohexose everything else is being compared to.

182
Q

Draw or visualize D-glucose as a Fischer projection versus a Haworth diagram. Indicate which OH group attacks/attacked the carbonyl carbon in each.

A

The phrase “down right, up lefting” (which sounds like “downright uplifting”) can help you remember that the groups on the right in the Fischer projection should point down in the Haworth diagram, and the groups on the left should point up.

183
Q

Draw or visualize a pyranose and a furanose.

A

The key difference is that a pyranose is a 6-membered ring with one O in the ring, whereas the furanose is a 5-membered ring with one O in the ring.

184
Q

Draw or visualize D-glucose α and β anomers as Haworth projections. What differentiates the α from the β anomer?

A

In the α form, the OH group at the anomeric carbon points in the same (think “sαme”) direction (up/down) as the OH on C2, and the opposite direction of the CH2OH flag group.

In the β form, the OH group at the anomeric carbon points in the same direction as the CH2OH flag group, and the opposite direction of the C2 hydroxyl.

185
Q

Describe the process of mutarotation.

A

Mutarotation is when the ring-form of the sugar opens up and then recloses again. This may cause the sugar to bounce back and forth between the α and β anomers.

186
Q

What does the naming convention for dissacharides of α-Man1,3-Gal indicate?

A

α indicates that the anomeric carbon (C-1) of mannose involved in this bond is an α anomer. 1,3 indicates that the bond is between C-1 of mannose and C-3 of galactose.

187
Q

Sucrose is considered a nonreducing sugar while lactose and mannose are considered reducing sugars. Why is this the case?

A

Lactose and mannose have an anomeric carbon that can undergo mutarotation to form an aldehyde group, which can be oxidized and act as a reducing agent.

Sucrose is considered a nonreducing sugar because it does not have an anomeric carbon available for mutarotation. Both sugar monomers are trapped in their cyclic forms.

188
Q

CRB True or false? Any monosaccharide with an Acetal Ring is considered a Reducing Sugar.

A

False. Any monosaccharide with a Hemiacetal Ring is considered a Reducing Sugar.

189
Q

Compare the structure of cellulose and amylose (starch).

A

Cellulose is a polysaccharide composed of glucose with β-1,4 linkages.

Amylose is a polysaccharide composed of glucose with α-1,4 linkages.

MCAT (26 decks)

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