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BH4 > Lecture 5/6 > Flashcards

Lecture 5/6 Flashcards

1
Q

What are alpha helices

A

Coil stabilized by hydrogen bonding btwn NH of 1 peptide bond CO of peptide bonds four AA’s in each direction

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2
Q

What are beta sheets

A

2 polypeptide regions whose backbones are parallel antiparallel

  • R groups stick out
  • H bonding btwn CO of 1 peptide group and NH group of adjacent peptide
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3
Q

What are motifs

A

common combo’s of a-helices and b-sheets connected by looped regions of varying lengths

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4
Q

What is the purpose of motifs?

A

.

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5
Q

What are domains

A

discrete, locally folded unit of tertiary structure that usually has a specific fxn (& contains several motifs)

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6
Q

Example of domain?

A

enzyme glyceraldehyde phosphate dehydrogenase is a single polypeptide chain folded into two functional domains

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7
Q

Thermodynamically-based approach defines protein domains as?

A

cooperative chain segments,

independently folded

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8
Q

How many disulfide linkages that hold 2 chains of insulin together?

A

3

- 2 intermolecular, 1 intra

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9
Q

Insulin molecules come together as ____ (stabilized by ___ zinc ions) for storage in the granules of the beta cells of the panreas

A
  1. hexamers

2. 2 zinc ions

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10
Q

When do insulin molecules get secreted and how

A

when you start to eat a meal

- into bloodstream via exocytosis

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11
Q

Diff btwn RNA and DNA?

A
  1. RNA has 2’OH and DNA has 2’H

1. RNA has uracil, DNA has thymine (alkyl group instead of H beside =O)

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12
Q

What is phosphoester bond

A

btwn P1 and O

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13
Q

What is phosphoanhydride bond

A

btwn P2 and O, P3 and O

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14
Q

Adenine vs adenosine

A

Adenine is base only adenosine is sugar + base

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15
Q

Fxns of nucleotides? Example of each

A
  1. Carry chemical nrg in their easily hydrolyzed phosphoanhydride bonds
    e. g. ATP
  2. Combine w/other groups to form coenzymes
    e. g. coenzyme A
  3. Used as small intracellular signaling molecules in the cell
    e. g. cyclic AMP
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16
Q

What are polysaccharides

A

polymers of sugar and sugar derivatives

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17
Q

What are the monomers of polysaccharides

A

monosaccharides

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18
Q

Formula for polysaccharides

A

CnH2nOn (n=3-7)

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19
Q

What are carbohydrates

A

Hydrates of carbon

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20
Q

Most common sugar in biological world

A

aldohexose D-glucose, C6H12O6

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21
Q

Examples of pentoses

A

Ribose, deoxyribose

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22
Q

How are carbons of glucose numbered

A

Beginning w/more oxidized end (carbonyl end)

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23
Q

If OH is on the right, it is ___.

If OH is on the left, it is ___.

A 
Right = D
Left = L
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24
Q

Most naturally occurring sugars are ___ isomers

A

D isomers

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25
Q

What are isomers

A

Same formulas but differ only in spatial arrangement of atoms

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26
Q

Why are these small differences in isomers have such a big affect

A

Have minor changes in chemical properties of the sugars but differences recognized by enzymes & other proteins thus have major biological effects

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27
Q

How is pyranose ring, predominant form of glucose, formed?

A

C1 aldehyde reacts w/OH on C5

- C1 is now hemiacetal

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28
Q

How many alternative forms of pyranose ring structures are there? What are they?

A
  • 2

- alpha and beta

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29
Q

What determines the form of pyranose ring structure? Is alpha up or down, is beta up or down?

A

Spatial orientation of hydroxyl group of C1

  • Alpha: 1’ OH is below, 4’ OH is below
  • Beta: 1’ OH is above, 4’ OH is below
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30
Q

What is another name for C1 carbon of glucose

A

Anomeric carbon

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31
Q

Starch and glycogen have ___-D-glucose

A

Alpha

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32
Q

Cellulose has __-D-glucose

A

Beta

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33
Q

What is expelled during condensation of 2 monosaccharides, what is formed?

A

Water expelled, O-glycosidic bond formed

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34
Q

How is O-glycosidic bond formed

A

Anomeric carbon reacts w/a hydroxyl (disaccharides)

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35
Q

Examples of disaccharides joined by O-glycosidic bonds between 2 monomers

A

Maltose, lactose, sucrose

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36
Q

How are disaccharides distinguished by?

A

Component monosaccharides and their order, which carbons are involved in their glycosidic bond & configurations of the anomeric carbons

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37
Q

Even tho maltose and cellulose are both dimers of glucose, why is there such a big diff

A
  • Significant impact on shape of resulting molecule, which determines the bonds accessible to specific enzymes
  • diff enzymes are needed to catalyze their hydrolysis
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38
Q

What is lactose

A

principal carbohydrate in milk (& milk products)

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39
Q

How can disaccharides enter cells

A

Must be hydrolyzed to monosaccharides extracellularly

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40
Q

How can disaccharides enter cells

A

Must be hydrolyzed, by enzymes attached to outer surface of epithelial cells lining small intestine, to monosaccharides extracellularly

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41
Q

Enzyme that hydrolyzes lactose

A

Lactase (human

- B-galactosidase (bacteria)

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42
Q

Why do people become lactose intolerant

A

Stop producing enough lactase

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43
Q

How is N-glycosidic bond produced

A

Anomeric carbon reacts w/nitrogen (e.g. nucleotides)

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44
Q

What groups allow formation of branched of sugars

A

Multiple OH groups participating in glycosidic bonds

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45
Q

What are 3 fxns of polysaccharides in living organisms (3 S’s)

A

Storage
Structure
Signaling

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46
Q

Storage polysaccharide in plants? In animals? Are they alpha or beta glucoses

A

Plants: starch
Animals: Glycogen
Both a-D-glucose

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47
Q

What makes up starch

A

10-30% amylose

70-90% amylopectin

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48
Q

Is amylose branched or unbranched? Amylopectin?

A
  • Amylose: unbranched

- Amylopectin - branched

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49
Q

Where is glycogen found in animals? Difference btwn areas?

A
  • liver (storage)

- muscles (immediate nrg)

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50
Q

Amylose, amylopectin, and glycogen are all made of α-D-glucose. What distinguishes them?

A

Bonds

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51
Q

What are oligosaccharides?

A

Short chains

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52
Q

Characteristics of amylose

A
  • Linear polymer

- 1 ->4 linkage btwn glucose monomers

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53
Q

Characteristics of amylopectin

A
  • Branched polymer

- 1->4 and 1->6 linkage btwn every 25th glucose

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54
Q

Characteristics of glycogen

A
  • Branched polymer

- 1->4 and 1->5 linkage btwn every 10th glucose

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55
Q

Why are amylopectin and glycogen branched?

A

Enzymes catalyze removal of glucose from non-reducing ends (ends of branches) thus a lot of glucose can be released at once rather than one at a time if these polymers were a single chain

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56
Q

Cellulose is __-D-glucose and 1->___ linkage

A

b-D-glucose 1->4 linkage

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57
Q

Mammals cannot hydrolyze
β (1à4) bond and therefore
cannot use cellulose as food
Really?

A

.

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58
Q

Cell walls of most bacteria contain what 2 sugars? What linkage?

A

GlcNAc and MurNAc

- B(1->4)

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59
Q

Where is chitin found

A

Insect exoskeletons, crustacean shells, fungal cell walls

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60
Q

How does the structures of starch and glycogen and cellulose differ

A
  • Starch & glycogen coil spontaneously into loose helices but structure not highly ordered cause numerous side chains of amylopectin and glycogen
  • Cellulose forms rigid, linear rods. These aggregate into microfibrils & when combined w/other polymers in cell wall like pectin and protein extensin, resemble “reinforced concrete”
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61
Q

Why are lipids not true polymers?

A

Not built up of monomeric subunits so not polymerized

62
Q

Why are lipids still considered macromolecules?

A

Large MW and association w/other macromolecules

63
Q

What are the main storage lipids

A

Triacylglycerols

64
Q

What are the main constituents of membranes

A

Phospholipids

65
Q

What is the role of sphingolipids

A

Plays roles in cellular recognition

66
Q

Fxn of cholesterol

A

Both a membrane lipid & precursor for steroid hormones (in animal cells)

67
Q

What lipids are biologically active?

A
  • Lipid soluble vitamins A, D, E, K

- smaller amounts than storage or structural

68
Q

Fxn of biologically active lipids

A
  • Carry signals from cell to cell & from tissue to tissue
69
Q

Characteristic of lipids

A

Low solubility in water, relatively hydrophobic

70
Q

Biological fxns of lipids?

A

Storage of energy: reduced compounds, lots of available energy

Hydrophobic nature: good packing

Insolation from environment:

  • low thermal conductivity
  • high heat capacity (can “absorb” heat)
  • mechanical protection (can absorb shocks)

Water repellant:
- keep surface of organisms dry, prevent
excessive wetting (birds), prevent loss of water via evaporation

Provide membrane structure

Cofactors for enzymes (e.g., vitamin K for blood clot formation; coenzyme Q for ATP synthesis in mitochondria)

Signaling molecules (e.g., steroid hormones)

Pigments (colour of tomatoes, carrots, etc.)
Antioxidants (e.g., vitamin E)

71
Q

How are lipids classified?

A
  • based on structure & fxn
  • lipids that contain fatty acids and lipids that do not
  • lipids that contain fatty acids can be further separated into storage lipids and membrane lipids
72
Q

What characteristics of fatty acids

A
  • carboxylic acids w/CH chains 4-36 carbons
  • most natural FA’s have even $ of carbons
  • most natural FA’s unbranched
73
Q

What are saturated FA’s

A

no DB’s btwn carbons in chain

74
Q

What are omega-3 fatty acids

A
  • essential nutrients

- humans cannot synthesize inc ALA, DHA, and EPA

75
Q

Which (saturated or unsaturated) FA’s has DB’s that is rigid and creates kink in chain

A

unsaturated

76
Q

The double bonds in natural unsaturated fatty acids are commonly in __ confirmation, which kinks the chain

A

cis

77
Q

Saturated fatty acids pack in a fairly orderly way due to _____ (e.g., van der Waals)

A

extensive favourable interactions

78
Q

Unsaturated cis fatty acids pack less evenly due to the ___ (less extensive favourable interactions)

A

kinks

79
Q

It takes ___ thermal energy to disrupt disordered/kinky packing of unsaturated fatty acids: ____ melting point

A
  • less

- lower melting point

80
Q

Solubility of fatty acids _________ as the chain length increases

A

decreases?

81
Q

Melting point decreases as the chain length __________ and

the # of double bounds ____________

A
  • decreases

- increases

82
Q

How are trans fatty acids formed

A

Partial hydrogenation of unsaturated FA’s to reduce # of cis bonds

83
Q

Purpose to hydrogenation

A

Inc shelf life or stability at high temps of oils in cooking

84
Q

A ___ double bond allows a given fatty acid to adopt an extended (___) confirmation

A
  • trans

- less kinky than cis

85
Q

Consuming trans fats increases risk of?

A

Cardiovascular disease

86
Q

Majority of fatty acids in biological systems are found in the form of
___

A

triacylglycerols

87
Q

How many ester linkages in triacylglycerol

A

3 ester linkages

88
Q

Solid triacylglycerols are called? Liquid?

A 
Solid = fat
Liquid = oil
89
Q

The primary storage form of lipids (body fat) is in the ___ tissue

A

adipose

90
Q

TAGs are less soluble in water than fatty acids due to

A

the lack of charged

carboxylate group

91
Q

TAG are ___ dense than water

A

less (fats and oils float)

92
Q

Fatty acids carry more energy per carbon

than polysaccharides because they are more ___

A

reduced

93
Q

Difference btwn glucose/glycogen and fats for energy needs?

A
  • Glucose/glycogen for short-term energy needs, quick delivery
  • fats for long-term energy needs, slow delivery
94
Q

The number of adipocytes increases most rapidly

during what period of your life

A

late childhood and early adolescence

95
Q

With fat loss, adipocytes shrink in size or number?

A

Shrink in size, never number

96
Q

Membrane lipids contain ___ head groups and
___ tails (usually attached
fatty acids)

A
  • polar

- non polar tails

97
Q

Membrane lipids diversification can come from? (3)

A
  • modifying the backbone
  • changing the fatty acids
  • modifying the head groups
98
Q

What determine the surface properties

of membrane

A

properties of head group

99
Q

All organisms have same membrane lipid head group composition? T or F

A

False

Dif organisms have dif membrane lipid head group compositions

100
Q

All tissues have the same membrane lipid head group compositions

A

False

Diff tissues have dif membrane lipid head group compositions

101
Q

In water, lipids can form what 2 shapes?

A
  • surface film or spherical micelle
102
Q

Lipid derivatives can form larger aggregates held together by ____ forces

A

hydrophobic

103
Q

___ form large spherical fat droplets in cell cytoplasm

A

Triacylglycerols

104
Q

____ and ____ form self-sealing lipid bi-layers, which are the basis for cell membranes

A

phospholipids and glycolipids

105
Q

Lipid structures formed in water depend on what 2 things

A
  • type of lipid

- concentration

106
Q

How many AA’s present in a cell at a given time? How many build up protein? What confirmation are they all in?

A
  • 60
  • 20
  • L
107
Q

What bond dictates final folding?

A

Non-covalent bonds

108
Q

Can domains be separated from one another

A

yes

109
Q

Similarity btwn DNA and RNA

A

both directional (5’ -> 3’) and antiparallel

110
Q

Most naturally occurring sugars are __ isomers

A

D

111
Q

Why can’t disaccharides directly enter cells

A

Membrane is impermeable to disaccharides. There is not channels or carriers that take them up.

112
Q

Which TEM would show a lactose intolerant person

A

Whichever image shows lactase enzyme being less dark and dense

113
Q

Storage polysaccharides have __ links

A

alpha links

114
Q

How do mammals digest cellulose

A

Microflora and rumination

115
Q

Is b-D-gluose or a-D-glucose more stable

A

b-d-glucose cause no branching = more stable

116
Q

Is chitin heteropolysaccharie or homopolysaccharide

A

homopolysaccharide

117
Q

Alkyl chain emphasized on what molecule

A

Steriod

118
Q

What kind of lipid does not have fatty acids

A

Archaebacterial ether lipids

119
Q

why dont archaebacterial ether lipids have fatty acids

A

can survive high temps so membranes need to be more protected

120
Q

are storage lipids polar or neutral

A

neutral (aggregate for storage)

121
Q

are membrane lipids polar or neutral

A

polar

122
Q

What would happen if FA became part of lipid bilayer

A

Saturated FA are very straight and packed together tightly so membrane becomes more stable

123
Q

Why is it membranes are bad when liquid

A

leaky liquid anything can go in

124
Q

Trans conformation looks similar to what FA’s? Allows for what kind of packing

A

saturated FA’s, more tightly packed

125
Q

Charge of triacylglycerol?

A

Neutral

126
Q

Main fxn of triacylglycerol

A

storage

127
Q

How many FA in TAG

A

3

128
Q

If u have a fatty acid w/just 1 hydrophobic tail what till it aggregate to

A

micelle

129
Q

individual unit of micelle is what shape

A

conical

130
Q

individual unit of bilayer is what shape

A

cylindrical

131
Q

3 main types of lipids found in membranes

A
  • phosphoglycerides
  • sphingolipids
  • steroids
132
Q

What is the primary constituents of cell membranes

A

phosphoglycerides

133
Q

Phosphoglycerides characteristic

A

Two fatty acids form ester linkages with the first and second hydroxyl of glycerol-3-phosphate

The highly polar phosphate group may be further esterified through a phosphodiester bond to a head group (R)

134
Q

How are phosphoglycerides classified

A

by their head group

135
Q

The backbone of sphingolipids is NOT glycerol but a long-chain amino alcohol ____

A

sphingosine

136
Q

A fatty acid is joined to sphingosine
via an ___ linkage rather than an ester linkage usually seen
in lipids

A

amide

137
Q

A polar head group is connected to sphingosine by a ____ or ___ linkage

A

glycosidic or phoshodiester

138
Q

The sugar-containing glycosphingolipids are found largely where

A

in the outer face of plasma membranes

139
Q

Fxn of sphingolipids

A

structure and cell signaling

140
Q

What is the steroid nucleus made of

A

4 fused rings, hydroxyl group (polar head) in A-ring, various nonpolar side chains

141
Q

Fxn of cholesterol and related steroids in membranes

A
  • modulate fluidity and permeability

- thicken the plasma membrane

142
Q

How do mammals obtain cholesterol

A

From food or synthesize de novo in the liver

143
Q

How is cholesterol transported

A

bound to proteins, is transported via blood vessels in low-density lipoproteins (LDL)
- tends to deposit in and clog arteries

144
Q

What is the precursor to steroids

A

cholesterol

145
Q

What causes cholesterol to precipitate

A

If the phospholipid: cholesterol ratio is 1:1, cholesterol is in effect soluble in the phospholipids

If the ratio is higher than 1:1, cholesterol will come out of solution and crystallize

146
Q

Do steroid hormones have alkyl chain found in cholesterol?

A

no

147
Q

Are steroids or cholesterol more polar

A

steroids

148
Q

how are steroid hormones synthesized

A

from cholesterol in gonads and adrenal glands

149
Q

how are steroid hormones transported

A

carried in bloodstream by carrier proteins

150
Q

What are terpenes (class of lipids) formed from

A

5 carbon isoprene is fundamental building block

151
Q

What is the precursor of cholesterol

A

isoprene

BH4 (9 decks)

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