Metabolism and Localisation of Biochemical Pathways Flashcards
(177 cards)
1
Q
What are the three major types of membrane lipids?
A
Phospholipids, glycolipids, cholesterol
2
Q
What two alcohols can phospholipids be derived from?
A
Glycerol and sphingosine
3
Q
What are phospholipids derived from glycerol called?
A
Phosphoglycerides
4
Q
What are phosphoglycerides composed of?
A
Glycerol backbone, two fatty acid chains, and a phosphorylated alcohol
5
Q
Do glycolipids contain sugar?
A
Yes
6
Q
What functional group does cholesterol belong to?
A
Sterol
7
Q
Is cholesterol more present in eukaryotes or prokaryotes?
A
Eukaryotes
-present in eukaryotes but not in most prokaryotes
8
Q
Are plasma membranes or organelle membranes are rich in cholesterol?
A
Plasma membranes
-membranes of organelles typically have smaller amounts of cholesterol than the cholesterol rich plasma membrane
9
Q
What technique is used to identify lipid components of membranes?
A
Thin layer chromatography (TLC)
10
Q
What is the basic structure of a phospholipid?
A
Hydrophilic (polar group) head and hydrophobic (hydrocarbon) tail
11
Q
What is the hydrophobic unit of phosphoglycerides?
A
2 fatty acid chains
12
Q
What is the hydrophilic unit of phosphoglycerides?
A
Phosphorylated alcohol
13
Q
What is the hydrophobic unit of sphingomyelin?
A
Fatty acid chain and hydrocarbon chain of sphingosine
14
Q
What is the hydrophilic unit of sphingomyelin?
A
Phosphorylated choline
15
Q
What is the hydrophobic unit of glycolipids?
A
Fatty acid chain and hydrocarbon chain sphingosine
16
Q
What is the hydrophilic unit of glycolipids?
A
One or more sugar residues
17
Q
What is the hydrophobic unit of cholesterol?
A
Entire molecule except for OH group
18
Q
What is the hydrophilic unit of cholesterol?
A
OH group at carbon 3
19
Q
What are the three potential arrangements for phospholipids in aqueous medium?
A
Micelle, liposome, lipid bilayer
20
Q
Why are micelles difficult to form?
A
Fatty acid chains are too bulky to fit inside
21
Q
What is the most common structure of phospholipids in aqueous medium?
A
Lipid bilayer
22
Q
What stabilises a lipid bilayer?
A
Dispersion (London) forces and hydrophobic interactions between hydrocarbon chains and electrostatic & hydrogen bonding attractions between the polar head group and water
23
Q
How do we know the arrangement of lipids in the membrane?
A
X-ray diffraction
24
Q
What is membrane fluidity controlled by?
A
Fatty acid composition, cholesterol content
25
What are the two possible conformations of fatty acyl chains?
Trans (rigid) or gauche (more fluid)
26
How can cholesterol regulate membrane fluidity?
Increases fluidity by preventing crystallisation of fatty acyl chains and can decrease fluidity by sterically blocking larger motions of fatty acyl chains
27
What are integral membrane proteins?
Proteins which are embedded in and span the lipid bilayer
28
What are peripheral membrane proteins?
Proteins bound to the membrane by electrostatic and hydrogen-bond interactions
29
What type of membrane proteins are used for active transport?
ATP-powered pumps
30
What are the four classes of ATP-powered pumps?
P-class, V-class, F-class, ABC superfamily
31
What do P-class pumps transport?
Ions
32
Where are P-class pumps found?
- Plasma membrane of plants, fungi, and bacteria (H+ pump)
| - NA+/K+ pump of higher eukaryotes plasma membrane
33
What do V-class pumps transport?
Protons (across pH)
34
Where are V-class pumps found?
- Vacuolar membranes of plants, yeast, and other fungi
| - Endosomal and lysosomal membranes in animal cells
35
What do F-class pumps transport?
Protons
36
Where are F-class protons found?
- Bacterial plasma membranes
| - Inner mitochondrial membrane
37
What does the ABC superfamily transport?
Small molecules
38
Where are ABC superfamily pumps found?
- Bacterial plasma membranes
| - Mammalian plasma membranes
39
Which class of ATP-powered pumps is cystic fibrosis linked to?
ABC superfamily
40
What are ABC superfamily transporters made up of?
Transmembrane domains and two cytosolic ATP binding sites
41
Which ions can be transported down concentration gradients by their specific ion channels?
NA+, K+, Ca2+, Cl-
42
Is the potential difference negative inside or outside the cell?
Inside
43
What is the difference between gated and non-gated ion channels?
Gated change state in response to membrane potential signalling but non-gated have no response
44
What is resting membrane potential?
The potential difference between the inside and outside of the cell
45
What is the typical range fo resting membrane potential?
30 to -100 mV
46
What are the three reasons for the existence of the resting membrane potential?
- semi-permeable cell membrane means unequal ion distribution inside and outside of cell
- presence of ion pumps
- presence of ion channels
47
What is a uni-porter?
Transport only one type of species substrate
48
What is co-transport?
Happens against the conc. gradient and is where a molecule and ion are coupled and must move together
49
What is symport?
When coupled molecule/ion move in the same direction
50
What is antiport?
When coupled molecule/ion move in opposite directions
51
A mutation in which transport protein contributes towards epilepsy?
Brain Na+ channels
52
A mutation in which transport protein contributes towards cystic fibrosis?
CFTR
53
A mutation in which transport protein contributes towards cancer drug resistance?
MDR-1
54
Which channel is inhibited to treat stomach ulcers?
Gastric H+/K+ ATPase
55
Which biomolecules are the most abundant on Earth?
Carbohydrates
56
Name 6 structural and protective elements contributed to by carbohydrates
- cell walls of bacteria and plants
- connective tissues of animals and lubrication of skeletal joints
- adhesion between cells
- exoskeletons
- essential to protein function
- central to cell survival and cell-to-cell communication
57
What are carbohydrates made from?
Monosaccharides
58
What functional groups are the monosaccharides that make up carbohydrates?
Aldehydes or ketones:
| - aldoses/ketoses
59
Are carbohydrate chiral?
Yes
60
What is the definition of chirality?
Non-superimposable on its mirror image
61
Which isomers are the most naturally occurring monosaccharides?
D-isomers
62
What is the predominant form of saccharides with 5 or more carbons?
Cyclic
63
How does cyclisation of D-glucose occur?
Nucleophilic attack of the C5 hydroxyl on the C1 aldehyde/ketone to form the hemiacetal/hemiketal
64
How many saccharide units in oligosaccharides?
Two to ten
65
In what form are polysaccharides stored in plants?
Starch
66
What are the two types of glucose polymer in starch?
Amylose and amylopectin
67
Describe amylose
Long, unbranched chains of D-glucose, alpha 1,4 linkages
68
Describe amylopectin
Highly branched, alpha 1,4 and 1,6 linkages
69
In what form are polysaccharides stored in animal cells?
Glycogen
70
In which tissues is glycogen most abundant?
Muscle and liver
71
Describe glycogen
Succesive D-glucose molecules, alpha 1,4 linkage, alpha 1,6 branch points, more extensively branched than amylopectin
72
Where are alpha-amylases and glycosidases secreted?
Salivary glands and pancreas
73
What is the role of alpha-amylases and glycosidases?
Break alpha 1,4 glycosidic bonds between glucose units during digestion allowing ingested starch and glycogen to serve as sources of D-glucose for aerobic respiration
74
Describe cellulose
Tough, fibrous, water insoluble, found in plant cell wall, polymer of D-glucose, unbranched, homopolysaccharide, beta D-glucose, 1,4 linkage
75
How many enzyme catalysed reactions are there in glycolysis?
10
76
What are the two phases of glycolysis?
Preparatory and payoff
77
What happens overall in the preparatory phase?
ATP consumption
78
What happens overall in the payoff phase?
ATP production
79
Describe the first reaction of glycolysis
```
Reactant: Glucose
Product: Glucose-6-phosphate
Enzyme: Hexokinase
Reversible?: No
Produces ADP from ATP
```
80
Describe the second reaction of glycolysis
Reactant: Glucose-6-phosphate
Product: Fructose 6-phosphate
Enzyme: Phosphoglucose isomerase
Reversible?: Yes
81
Describe the third reaction of glycolysis
```
Reactant: Fructose 6-phosphate
Product: Fructose 1,6-biphosphate
Enzyme: Phosphofructokinase
Reversible?: No
Produces ADP from ATP
```
82
Describe the fourth reaction of glycolysis
Reactant: Fructose 1,6 biphosphate
Product: Glyceraldehyde 3-phosphate (GAP) and dihydroxyacetone phosphate
Enzyme: Aldolase
Reversible?: Yes
83
Describe the fifth reaction of glycolysis
Reactant: Dihydroxyacetone phosphate
Product: Glyceraldehyde 3-phosphate (GAP)
Enzyme: Triose phosphate isomerase
Reversible?: Yes
84
Describe the sixth reaction of glycolysis
Reactant: Glyceraldehyde 3-phosphate (GAP)
Product: 1,3-biphosphoglycerate
Enzyme: Glyceraldehyde 3-phosphate dehydrogenase
Reversible?: Yes
Produces NADH from Pi and NAD+
85
Describe the seventh reaction of glycolysis
```
Reactant: 1,3-biphosphoglycerate
Product: 3-phosphoglycerate
Enzyme: Phosphoglycerate kinase
Reversible?: Yes
Produces ATP from ADP
```
86
Describe the eighth reaction of glycolysis
Reactant: 3-phosphoglycerate
Product: 2-phosphoglycerate
Enzyme: Phosphoglycerate mutase
Reversible?: Yes
87
Describe the ninth reaction of glycolysis
```
Reactant: 2-phosphoglycerate
Product: Phosphoenolpyruvate
Enzyme: Enolase
Reversible?: Yes
Produces water
```
88
Describe the tenth reaction of glycolysis
```
Reactant: Phosphoenolpyruvate
Product: Pyruvate
Enzyme: Pyruvate kinase
Reversible?: No
Produces ATP from ADP
```
89
Which reactions of glycolysis make up the preparatory phase?
1-5
90
Which reactions of glycolysis make up the payoff phase?
6-10
91
How many molecules of GAP are produced in the preparatory phase?
Two
92
List the ten enzyme used in glycolysis
1. Hexokinase
2. Phosphoglucose isomerase
3. Phosphofructokinase
4. Aldolase
5. Triose phosphate isomerase
6. Glyceraldehyde 3-phosphate dehydrogenase
7. Phosphoglycerate kinase
8. Phosphoglycerate mutase
9. Enolase
10. Pyruvate kinase
93
What is the pyruvate dehydrogenase complex?
A complex of 3 enzymes and 5 coenzymes that convert pyruvate into acetal-coA by pyruvate decarboxylation
94
What is E1?
Pyruvate dehydrogenase
95
Which cofactors accompany E1?
Thiamine pyrophosphate (TPP)
96
What is E2?
Dihydrolipoyl transacetylase
97
Which cofactors accompany E2?
Lipoic acid and coA-SH (coenzyme A)
98
What is E3?
Dihydrolipoyl dehydrogenase
99
Which cofactors accompany E3?
NAD+ and FAD
100
What are the 5 cofactors in the pyruvate dehydrogenase complex?
TPP, lipoid acid, coA-SH, NAD+, FAD
101
What is the fuel for the citric acid cycle?
Acetyl-CoA
102
How many enzyme catalysed reactions are there in the citric acid cycle?
8
103
Describe the first reaction in the citric acid cycle
Enzyme: Citrate synthase
Intermediate: Citrate
Converts acetyl-CoA into CoA-SH
104
Describe the second reaction in the citric acid cycle
Enzyme: Aconitase
Intermediate: Isocitrate
105
Describe the third reaction in the citric acid cycle
Enzyme: Isocitrate dehydrogenase
Intermediate: alpha-Ketoglutarate
Carbon dioxide produced
NADH produced from NAD+
106
Describe the fourth reaction in the citric acid cycle
Enzyme: alpha-Ketoglutarate dehydrogenase
Intermediate: Succinyl-CoA
Carbon dioxide produced
NADH produced from NAD+
107
Describe the fifth reaction in the citric acid cycle
Enzyme: Succinyl-CoA synthetase
Intermediate: Succinate
CoA-SH produced
ATP produced from ADP and Pi
108
Describe the sixth reaction in the citric acid cycle
Enzyme: Succinate dehydrogenase
Intermediate: Fumarate
FADH2 produced by FAD
109
Describe the seventh reaction in the citric acid cycle
Enzyme: Fumarase
Intermediate: Malate
110
Describe the eighth reaction in the citric acid cycle
Enzyme: Malate dehydrogenase
Intermediate: Oxaloacetate
NADH produced by NAD+
111
How many times must the citric acid cycle be completed before 1 glucose molecule is completely oxidised?
Twice
112
Which intermediate is a source for fatty acids and sterols?
Citrate
113
Which intermediate is a source for glutamate?
alpha-Ketoglutarate
114
Which intermediate is a source for porphyrins, heme, and chlorophyll?
Succinyl-CoA
115
Which intermediate is a source for aspartate and glucose?
Oxaloacetate
116
What regulates the citric acid cycle?
Concentrations of ATP and NADH
117
How does most recycling of ADP back to ATP take place?
Oxidative phosphorylation
118
Is ubiquinone (UQ) hydrophilic or hydrophobic?
Very hydrophobic
119
Where UQ found?
Inner mitochondrial membrane
120
Where does oxidative phosphorylation take place?
Inner mitochondrial membrane
121
What moves electrons through proteins in the electron transfer chain?
Cofactors with metal centres
122
Describe the reactions that occur in complex I of the ETC
- NADH is converted into NAD+
- one electron from previous reaction is donated to the following reaction
- 2H+, UQ, and the donated e- are converted into UQH2
123
Describe the reactions that occur in complex II of the ETC
- FADH2 (succinate) is converted into FADH
- one electron from previous reaction is donated to the following reaction
- 2H+, UQ, and the donated e- are converted into UQH2
124
Describe the reactions that occur in complex III of the ETC
- 2H+ go into the complex from the matrix
- UQ is converted to UQH2
- each UQH2 from complex I and complex II is converted into 2UQ
- Fe3+ is converted into Fe2+
- 4H+ leave the complex into the intermembrane space
125
Describe the reactions that occur in complex IV of the ETC
- 1/2 O2 and 2H+ are converted to H2O
| - the Fe2+ from complex III is converted to Fe3+
126
Compare the concentration of protons, pH, and relative charge of the matrix with the intermembrane space
```
The matrix:
- lower conc. of proteins
- more alkaline
- more negative charge
than the inter membrane space
```
127
What are the two types of reactions in photosynthesis?
Light reactions and carbon-assimilation reactions
128
What energy-transforming machinery do chloroplast thylakoid membranes contain?
- light-harvesting proteins
- reaction centres
- electron transport chains
- ATP synthase
129
What is the structure of chlorophyll?
Cyclic tetrapyrrole
130
Where does the Mg ion bind in chlorophyll?
At the centre of the structure
131
What is photosystem II (PS II)?
- large transmembrane assembly of over 20 subunits
- catalyses light-driven transfer of e- from H2O to plastoquinone
- drives reaction to a higher energy by harvesting solar energy
132
What is plastiquinone?
An electron acceptor
133
Describe the process that occurs in PS II
1. P680 absorbs light at 680nm
2. on excitation, P680 transfers an electron to a nearby pheophytin
3. the e- is transferred to a tightly bound plastoquinone
4. it is then transferred to a mobile plastoquinone
134
Describe the process that occurs in photosystem I (PS I)
1. P700 absorbs light at 700 nm
2. the e- travels from P700, via a chlorophyll and a quinone, to a set of 4 Fe-4S clusters
3. the e- is transferred to Ferredoxin and then to NADP+
135
What is gluconeogenesis?
The synthesis of glucose from non-carbohydrate precursors
136
Are tumour cells more regularly aerobic or anaerobic?
Anaerobic
137
Do tumour cells consume ATP?
Yes (lots)
138
Describe the four pathways of the metabolism of glucose?
- Glycogen/starch/sucrose: storage
- Pyruvate: Oxidation via glycolysis/gluconeogenesis
- Ribose 5-phosphate: Oxidation via pentose phosphate pathway
- Extracellular matrix and cell wall polysaccharides: structural polymer synthesis
139
What are the 3 main precursors that can be used in gluconeogenesis?
- lactate
- amino acids
- (not in animal cells) glycerol
140
What are non-carbohydrates converted into to enter the pathway?
Pyruvate or enter the pathway at a later stage as an intermediate
141
Which 2 molecules can the gluconeogenesis pathway start from?
Pyruvate or oxaloacetate
142
Where does gluconeogenesis take place?
Mostly in the liver and some in the kidney
143
Is glycolysis anabolic or catabolic?
Catabolic
144
Is gluconeogenesis anabolic or catabolic?
Anabolic
145
What regulates enzymes to prevent glycolysis and gluconeogenesis happening at the same time?
Allosteric mechanisms
146
Why do glycolysis and gluconeogenesis not occur at the same time?
They are both high energy processes
147
Give four reasons why the pentose phosphate pathway important?
- source of NADPH
- protects against oxidative stress
- major product is pentose 5-phosphate which is used to make RNA, DNA, and coenzymes
- important for rapidly dividing cells
148
What are the two phases of the pentose phosphate pathway?
- Oxidative generation of NADPH from NADP+
| - Nonoxidative interconversion of sugars
149
What is the initial reactant of the oxidative pentose phosphate pathway?
Glucose 6-phosphate
150
What is ribose 5-phosphate a precursor for?
Nucleotide and nucleic acid synthesis
151
What are fatty acids a source of?
Energy
152
What is produced during oxidation of fatty acids?
Acetyl-CoA
153
What is the process of converting fatty acids to acetyl-CoA called?
β-oxidation
154
What are the 7 steps of processing dietary lipids?
1. Bile salts emulsify dietary fats in the small intestine, forming mixed micelles
2. Intestinal lipases degrade triacylglycerols
3. Fatty acids and other products are taken up by the intestinal mucosa and converted into triacylglycerols
4. Triacylglycerols are incorporated into chylomicrons
5. Chylomicrons move through the lymphatic system and bloodstream to tissues
6. Lipoprotein lipase converts triacylglycerols to fatty acids and glycerol
7. Fatty acids are oxidised as fuel or re-esterified for storage
155
How are lipids often stored in cells?
Triacylglycerols
156
How are triacylglycerols mobilised from adipose tissue?
1. low levels of glucose in blood trigger glucagon release
2. glucagon binds to its hormone receptor
3. free fatty acids leave the adipocyte and are carried through the blood to provide energy to various cells
157
What are the 3 stages of fatty acid oxidation?
1. Long-chain fatty acid oxidised to give acetyl-CoA (β-oxidation)
2. Acetyl groups oxidised to CO2 via citric acid cycle
3. Electrons from stages 1 and 2 pass to O2 via respiratory chain, generating ATP
158
How many steps are involved in β-oxidation?
4
159
When are additional enzyme required in β-oxidation?
If the fatty acid:
- is unsaturated
- has odd number of carbons
160
How many additional enzymes are required if the fatty acid is unsaturated?
2
161
How many additional enzymes are required if the fatty acid has an odd number of carbons?
3
162
In what 3 circumstances does oxidative degeneration of amino acids occur in animals?
- during synthesis and degradation of cellular proteins
- when amino acids cannot be stored, due to protein-rich diet provided excess amino acids than needed
- during starvation/uncontrolled diabetes, when carbohydrates are unavailable or improperly used
163
Where are amino acid groups catabolised?
Liver
164
What happens if a muscle catabolises amino acids?
Nitrogen is transferred to alanine and released in the bloodstream
165
What happens to alanine taken up in the liver?
Converted into pyruvate for the synthesis of glucose
166
What happens to excess nitrogen?
Excreted via the urea cycle
167
What is the principal form of stored energy in. most organisms?
Lipids
168
Give the 7 examples of what specialised lipids serve as
- pigments e.g. retinol, carotene
- cofactors e.g. vitamin K
- detergents e.g. bile salts
- transporters e.g. dolichols
- hormones e.g. vitamin D derivatives, sex hormones
- extra- and intracellular messengers e.g. eicosanoids, phosphoinositols
- anchors for membrane proteins e.g. prenyl groups
169
Which hormones act faster: peptide and amine hormones or steroid and thyroid?
Peptide and amine hormones
170
What is metabolism?
A series of activities that provide cells with the molecules and energy they need to function, grow, and divide
171
Is the net ΔG of a metabolic pathway positive or negative under physiological conditions?
Negative
172
Why must transport of ammonia be carefully regulated?
It is toxic (mainly due to effects on the brain)
173
How is excess NH4+ (ammonium) excreted?
As ammonia, urea, or uric acid
174
Define ureotelic
Excrete amino acids as urea
175
What is energy coupling?
Mechanism to couple unfavourable reactions with strongly exergonic processes
176
What is intermediary (central) metabolism?
Combined activities of all pathways that interconvert precursors and molecules of low molecular weight
177
What are allosteric mechanisms?
The regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site
