Biochemistry Flashcards
(348 cards)
1
Q
Nonpolar amino acids
A
Alanine, glycine, valine, leucine, isoleucine, methionine, proline
2
Q
Aromatic amino acids
A
Tryptophan, phenylalanine, tyrosine
3
Q
Polar amino acids
A
Serine, threonine, asparagine, glutamine, cysteine
4
Q
Negatively charged amino acids
A
Aspartate, glutamate. They are acidic
5
Q
Postively charged amino acids
A
Lysine, arginine, histidine. They are basic
6
Q
Peptide bond formation
A
A dehydration reaction in which the electrophilic carbonyl carbon of one amino acid is attacked by the nucleophilic amino group of a second amino acid
7
Q
Primary structure
A
Sequence of amino acids. Stabilized by peptide bonds
8
Q
Secondary structure
A
Local structure of neighboring amino acids. Stabilized by H-bonding. Common examples: alpha-helices (CCW), beta-pleated sheets (can be parallel or antiparallel)
9
Q
Effect of proline on secondary structure
A
Disrupts secondary structure with its rigid cyclic structure
10
Q
Tertiary structure
A
3D shape of protein governed by hydrophobic interactions. Ex: disulfide bonds occur when two cysteine molecules are oxidized
11
Q
Quaternary Structure
A
Interaction between peptides in proteins that contain multiple strands
12
Q
Conjugated proteins
A
Proteins that have prosthetic groups, which may be a metal ion, vitamin, lipid, carb or nucleic acid
13
Q
Lyases
A
Catalyze cleavage without addition of water and without the transfer of electrons. May also be known as synthases performing the reverse of synthesis
14
Q
a-ketoglutarate + aspartate
A
Catalyzed by aminotransferase. Forms oxaloacetate and glutamate. A reaction of protein metabolism
15
Q
Ligases
A
Catalyze addition or synthesis reaction between large, similar molecules. Often use ATP
16
Q
Apoenzymes
A
Enzymes that require cofactors to function, but currently do not have their cofactor
17
Q
Holoenzymes
A
Enzymes that contain their necessary cofactors
18
Q
Cofactors and Coenzymes (and the difference)
A
Nonprotein molecules that some enzymes require for function. Cofactors: inorganic molecules/metal ions, often ingested as dietary minerals. Coenzymes: small organic groups that are mainly vitamins/derivatives of vitamins (NAD+, FAD, and CoA)
19
Q
Water-soluble vitamins
A
B complex vitamins, vitamin C
20
Q
Fat-soluble vitamins
A
A, D, E, K
21
Q
B-complex vitamins
A
Water-soluble. Thiamine, riboflavin, niacin, pantothenic acid, pyridoxal phosphate, biotin, folic acid, cyanocobalamin
22
Q
Prosthetic groups
A
Covalently bound cofactors or coenzymes. May be organic or inorganic
23
Q
Hill’s coefficient >1
A
Indicates positive cooperative binding takes place between substrate and enzyme
24
Q
Hill’s coefficient < 1
A
Indicates negative cooperative binding between enzyme and substrate
25
Hill's coefficient = 1
Indicates that no cooperative binding occurs
26
Feedback regulation
Regulation of an enzyme by products further down the given pathway
27
Types of Reversible Inhibition
Competitive, noncompetitive, mixed, and uncompetitive
28
Competitive inhibition
Inhibitor binds to the enzyme at the active site.
| K_m appears to increase, V_max stays the same
29
Noncompetitive Inhibition
```
Inhibitor binds to an allosteric site, which conformationally changes the active site. Binds well to both enzyme and enzyme-substrate complex. Cannot be overcome by adding more substrate.
K_m remains (because non-altered enzymes still function)
v_max decreases
```
30
Mixed Inhibition
Occurs when an enzyme can bind at an allosteric site to an enzyme OR an enzyme-substrate complex with different affinities for each.
If inhib binds better to enzyme, then K_m increases, but if it binds better to E-S complex, then K_m decreases.
In both cases, v_max decreases
31
Uncompetitive Inhibition
Inhibitor only binds the E-S complex and locks the substrate in, preventing its release and disabling the enzyme from performing its duty.
Both K_m and v_max decrease.
On L-B plot, the lines for with and without this inhib are parallel
32
Irreversible inhibition
Changes to the active site are permanent. Prime drug mechanism. Ex: aspirin
33
Mechanism of Aspirin
Irreversible inhibition of cyclooxygenase-1 in that it can no longer bind arachidonic acid to produce prostaglandins. Prostaglandins usually modulate pain and inflammatory response. The body must synthesize new cyclooxygenase-1
34
Glycosylation of Enzymes
Covalently tags an enzyme for transport within the cell or modifies protein activity and selectivity
35
Zymogens
Inacitve forms of enzymes that are activated when the enzyme is needed. Ex: trypsinogen is the zymogen of trypsin
36
Collagen
Main protein of the ECM. Has a trihelical structure (a helix made up of 3 helices). Provides strength and flexibility
37
Elastin
Also found in ECM. Responsible for stretch and recoil of tissues
38
Keratins
Intermediate filament proteins found in epithelial cells. Make up hair and nails. Aid in mechanical integrity of cells and have regulaotry functions
39
Motor proteins
ATPases that power conformational changes necessary for motor function. Interact with either actin (myosin) or microtubules (kinesin, dynein). Responsible for cellular movement and muscle contraction
40
Kinesin
Brings vesicles towards the positive end of microtubules. Ex: brings full vesicles of NTs to the membrane of pre-synaptic cell for release. Key roles in chromosome alignment during metaphase and depolymerizing MTs during anaphase of mitosis.
41
Dynein
Brings vesicles toward negative end of microtubules. Involved in the sliding movement of flagella and cilia. Bring vesicles of waste/recycled NTs towards the soma
42
Binding Proteins
Transport/sequester molecules by binding to them, increasing stability. Include Hb, Ca-binding proteins, DNA binding proteins, and more
43
Cell Adhesion Molecules (CAMs)
Proteins found on the surface of cells that help the cell bind to ECM or to other cells. 3 classes: cadherins, integrins, and selectins
44
Cadherins
Type of CAM. Glycoproteins. Mediate Ca-dependent cell adhesions. Often hold similar cell types together.
45
Integrins
Type of CAM. Have two membrane-spanning channels: alpha and beta, are essential to communicating/binding with ECM. Play an important role in cell signaling and may help promote cell division or apoptosis, also help with WBC migration and clotting
46
Selectins
Type of CAM. Bind to carbohydrates that originate on other cell surfaces. Weakest form of CAM. Expressed on WBCs and endothelial cells of blood vessels. Important role in inflammation and WBC migration
47
Immunoglobins
AKA antibodies. Work by neutralizing targets in the body like toxins and bacteria, then recruit other cells to help do away with the threat. Each only bind to one antigen at their unique antigen-binding regions (located at the tips of their "Y" structures)
48
Three possible outcomes of antibody binding to antigen
1. Neutralization (making antigen unable to exert its effect)
2. Opsonization (marking antigen for destruction by other WBCs)
3. Agglutination (clumping of the antigen+antibody into large complexes that will be phagocytosed by macrophages)
49
The 3 main types of G-proteins (and their functions)
G_s: stimulates adenylate cyclase, increases cAMP levels
G_i: inhibites adenylate cyclase, decreases cAMP levels
G_q: activates phosphlipase C -> cleaves phosphlipid from membrane to form PIP2, PIP2 gets cleaved into DAG and IP3, IP3 can open Ca-channels of ER, increasing Ca2+ levels in cell
50
GPCR mechanism of activation
Ligand binds to GPCR -> engages G protein -> GDP gets replaced by GTP -> alpha subunit dissociates -> alpha activates adenylate cyclase -> affects levels of cAMP depending on s vs i
51
Receptor tyrosine kinases
Enzyme-linked receptors. Composed of a monomer that dimerizes upon ligand-binding. The dimer then self-phosphorylates AND phosphorylates other enzymes
52
Electrophoresis
Subjects compounds to an electric field for separation. Negatively charged compounds migrate toward positively charged anode. Positively charged compounds migrate to negatively charged cathode. Polyacrylamide gel is the standard medium for proteins
53
Native PAGE
Polyacrylamide gel electrophoresis = PAGE. Analyzes proteins in their native states. Good for comparing molecular size or charge of proteins (better than SDS PAGE or size exclusion chromatography)
54
SDS-PAGE
Usefule for separating proteins based only off size. SDS disrupts all noncovalent interactions, binds to all proteins, and creates a large chain with net negative charges
55
Isoelectric Focusing
Separation of proteins based on pI. Gel has a pH gradient. Anode (+) is acidic , cathode (-) is basic. The protein stops moving when it reaches a portion of the gel wher ethe pH is equal to its pI
56
Column Chromatography
Adsorbent/stationary phase: silica or alumina beads. Separation basedon size and polarity. Less polar compounds have shorter retention times because they interact only weakly with beads
57
Ion-exchange chromatography
Column chromatography, except the beads are coated with a charged substance
58
Protein structure identification methods
X-Ray Crystallography, NMR. X-Ray is more common and reliable
59
Edman Degradation
Sequential digestion of proteins with specific cleavage enzymes in chunks of up to 50-70 amino acids. Removes N-terminal amino acid(s) that can then be run throughmass spec
60
Concentration Determination of Proteins
Method: spectroscopy. UV-spectroscopy is possible because proteins contain aromatic side chains. Also can be performed using colorimetric changes (BCA assay, Lowry reagent assay, Bradford protein assay)
61
Bradford Protein Assay
Measures protein concentration using color. The more blue the dye, the higher the concentration of protein. Most useful when there is only one type fo protein in the solution. Limited by presence of a detergent or excessive buffer
62
Migration velocity (proteins in PAGE)
v = E*z/f
E: electric field strength
z: net charge on the molecule
f: frictional coefficient
63
Equation to determine the number of stereoisomers with same C-backbone
= 2^n, where n is the number of chiral centers
64
The only stable cyclic carbohydrates
Pyranose rings (6 mem) and furanose rings (5 mem)
65
Anomeric Carbon
Carbon in a carbonhyrate that is the carbonyl C in straight-chain form
66
Anomers
alpha and beta forms of cyclized carbs. Alpha form has anomeric OH group trans to the CH2OH group. Beta form has anomeric OH group cis to the CH2OH group
67
Converting Fischer to Haworth projections
Any groups on the right in Fischer will point down in the Haworth projection.
68
Mutarotation
Spontaneous change in configuration between alpha and beta anomers. Can be sped up by addition of acid or base catalyst.
69
Dominant anomer of glucose (and reason)
beta anomer - because in alpha configuration the anomeric OH group is axial, which increases steric strain (decreases stability)
70
Aldonic acids
Aldoses that have been oxidized into carboxylic acids
71
Reducing sugar
Any monosaccharide with a hemiacetal ring (because they can be oxidized, therefore reducing another species)
72
Lactone
A cyclic ester with a carbonl group present on the anomeric C. Results when an aldose is oxidized in ring form.
73
Reagents used to detece the presence of reducing sugars
Tollens' reagent and Benedict's reagent
74
Tollen's reagent
Freshly prepared [Ag(NH3)2]+. Produces a silvery mirror when aldehydes are present.
75
Benedict's reagent
Indicates the presence of aldehydes when a red precipitate of Cu2O forms
76
Conversion of a ketose to carboxylic acid
Begins with keto-enol shift: tautomerization into an aldose under basic conditions. Aldose is then reacted with Tollens' of Benedict's reagent to form carb acid
77
Alditol
A former aldose that has been reduced to an alcohol
78
Glucokinase
Enzyme in the liver and pancreatic beta-islet cells that catalyzes phosphate esterification formation on glucose (ie phosphorylating glucose)
79
Glycosides (and how they are formed)
A form of acetal. Anomeric OH group on a hemiacetal is transformed into an alkoxy group (ether). Reaction of a hemiacetal and an alcohol. Formation is a dehydration reaction
80
Glycosidic bonds
Bonds between monosaccharides in di/polysoaccharides. Formed in the formation of glycosides.
81
Maltose
Disaccharide of two glucose molecules linked by alpha(1->4) linkage
82
Sucrose
Glucose-a-1,2-fructose. Disaccharide
83
Lactose
Galactose -beta-1,4-glucose. Disaccharide
84
Cellulose
Homopolysaccharide of glucose. Linkages: beta-1,4. Main strucutral component of plants. Humans cannot digest it because we lack cellulase, so it is a good source of fiber - draws water to the gut.
85
Starches
Alpha-D-glucose monomers. More digestable by humans.
86
Amylose vs Amylopectin
Both are starches. Amylose is linear. Amylopectin is branched, leading to a helix conformation. Iodine is often used to detect presence of amylose because it associated with the helical structure, forming a starch-iodine complex
87
Glycogen
glucose-alpha-1,4 polymer. Carbohydrate storage in animals. Highly branched (alpha1-6 linkages) --> makes it highly soluble in solution.
88
Glycogen phosphorylase
Cleaves glucose from the nonreducing end of glycogen branch and phosphorylates the freed monomer. Produces glucose-1-phosphate
89
Phospholipids
All contain a polar head group (a phosphate and an alcohol) attached to at least one hydrophobic fatty acid tail by a phosphdiester linkage
90
Link between polar head and nonpolar tail(s) in phospholipids
Phosphodiester linkages
91
Phosphoglycerides
AKA: glycerophosphlipids. Phospholipids with glycerol backbones. Two fatty acids are bound to the backbone by ester linkages
92
Sphingolipids
Phospholipids with sphingosine backbones
93
Phosphatidylcholine
Glycerophospholipids with a choline head group
94
Steroid hormones
Have high-affinity receptors often on the nucleus. Travel in the blood stream from endocrine glands. Simply diffuse through plasma membrane.
95
Triacylglycerol function and reason
Fuel storage. Reason: C's are highly reduced and yield high amount of energy upon oxidation, they are also dehydrated so they carry no extra water weight
96
Fat soluble vitamins
A, D, E, K
97
Do all sphingolipids contain a sphingosine backbone?
NO! Sphingolipids may contain either a sphingosine or sphingoid backbone
98
ABO blood-typing is reliant upon lipids of which class of glycolipids
Sphingolipids
99
Isoprene
5-Carbon molecules that make up terpene. One terpene has two isoprene units
100
Prostaglandins
Paracrine or autocrine signaling molecules that regulate cAMP production. Major downstream effects: pain, inflammation, smooth muscle contraction, body temp elevation, sleep-wake cycle
101
Effect of NSAIDs on prostaglandins
NSAIDs inihibit the production of COX, an enzyme that helps synthesize prostaglandins. Thus, prostaglandin production is decreased/inhibited
102
Waxes (and function)
Esters of long-chain fatty acids with long-chain alcohols. Function: protection in both plants and animals. Prevent dehydration in animals or repel water from birds' feathers
103
Terpenes
Odiferous chemicals made of isoprene subunits. Produced mainly by plants and some insects. Ex: Vitamin A, carotenoids, natural rubber
104
Terpenoids
AKA: Isoprenoids. Derivatives of terpenes that have undergone oxidation or rearrangement of the carbon skeleton. Also have functional groups added to the C skeleton
105
Steroids
Signaling lipids that contain 3 cyclohexane rings and 1 cyclopentane ring. Derivatives of terpenes
106
Which type of hormone at estrogens, testosterone, aldosterone, and cortisol?
Steroid hormones
107
Cholesterol
A steroid with hydrophilic and hydrophobic parts. Regulates membrane fluidity. In low temperature environments, cholesterol keeps membrane from getting too solid, and in high temperatures, keeps membrane from getting too fluid. Also a precursor to many steroid hormones, bile acids, and vitamin D
108
Vitamin A
AKA carotene. Important to vision, growth and development, and immune function. Precursor of retinal (light-sensing component in the eye) and retinol (storage-form of retinal)
109
Vitamin D
AKA: cholecalciferol. Active form is calcitrol, which increases uptake of Ca2+ and phosphate in the intestines. Promotes bone production
110
Rickets
Vitamin D deficiency
111
Vitamin E
AKA tocopherols and tocotrienols. Prevents cancer by acting as an antioxidant: attacks free-radicals and thus prevents oxidative damage.
112
Vitamin K
Vital to production of prothrombin, an important clotting factor in the blood.
113
Saponification
Strong base + triacylglycerol --> glycerol + fatty acid salt (soap)
An ester hydrolysis reaction
114
Surfactant
Decreases the surface tension at the surface of a liquid, acting as a detergent or emulsifier. Soaps are surfactants
115
Heterochromatin
Condensed DNA that remains condensed during interphase (only a small portion of total DNA). Transcriptionally silent. Contains highly repetitive sequences. Appears dark under light miscroscopy.
116
Euchromatin
Dispersed chromatin (classic "beads on a string" appearance). Genetically active. Appears light under light microscopy
117
Higher GC-content indicates ____ melting point because _____.
Higher MP because G-C bond has three hydrogen bonds wherease A-T only has two.
118
Purines
Contain two rings in their structures. Adenine and guanine.
119
Pyrimidines
Contain one ring in their structures. Cytosine, thymine, and uracil
120
Requirements of Aromaticity
1. Cyclic
2. Planar
3. Conjugation: alternating single and multiple bonds, or lone pairs, creating at least one unhybridized p-orbital for each atom in the ring
4. Huckel's rule: there are 4n + 2 pi electrons
121
cDNA
Complementary DNA that results from reverse transcription of mRNA. Used in DNA libraries and contains only the exons of genes that are transcriptionally active in the sample tissue
122
Ingredients of PCR
DNA sample, primer, free nucleotides, and enzymes (including polymerase from Thermus aquaticusis because it can withstand high temperatures)
123
Endonucleases
Cut DNA in the middle of sequences. Also used by cell from DNA repair. Used in lab for DNA analysis as restriction enzymes (they are used to cleave DNA for electrophoresis, Southern blotting, and to introduce a gene of interest into a viral vector for gene therapy)
124
Cytosine deamination results in ____
Uracil
125
Probe DNA
DNA with a known sequence
126
Replisome / Replication complex
Set of specialized proteins that assist DNA polymerases
127
Centromere
Point at which sister chromatids remain connected. Also can be seen at the "meeting point" of the replication forks
128
DNA topoisomerases
Introduce negative supercoiling by creating nicks in the DNA that allow relaxation of the coils. Then reseal their cuts
129
Direction of DNA/RNA Synthesis
5' to 3'
130
Direction that DNA and RNA polymerases read
3' to 5'
131
DNA Polymerase III
Replicates leading strand in prokaryotes
132
DNA polymerase - alpha, delta, epsilon
Work together to synthesize both the leading and lagging strands of DNA. Delta fills in the gaps left behind when the RNA primers are removed
133
DNA Polymerase - gamma
Replicates mitochondrial DNA
134
DNA Polymerase - beta and epsilon
Aid in DNA repair during replication
135
DNA Polymerase I
In prok, adds DNA nucleotides where RNA primer used to be
136
DNA ligase
Seals the ends of DNA newly synthesized DNA molecules together
137
Mismatch Repair
Detects and removes errors in replication. Occurs during G2 phase of cell cycle. Relevant genes are MSH2 and MLH1
138
Nucleotide Excision Repair
Proteins scan the DNA molecule for errors (like Thymine dimers that are induced by UV light), then and exicion endonuclease nicks the phosphodiester backbone of the damaged strand on either sides of the faulty nucleotide(s) and then removes it. DNA polymerase fills in the gaps and DNA ligase patches it all up
139
Base excision repair
First, glycolase enzyme recognizes and removes affected base, leaving an abasic/AP site. AP endonuclease recognizes the AP site and removes the damaged sequence. Repair by DNA polymerase and ligase occurs
140
DNA Cloning
Used to produce large amounts of a desired sequence.
Process: investigator ligates the gene of interest (extracted from a sequence using restriction enzymes) into a viral/bacterial plasmid vector that also contains an antibacterial resistant gene. Recombinant vector is then inserted into host bacterium and grown, isolated, in large quantities. The bacteria can either be made to express the gene of interest or lysed to reioslate the recombinant vectores.
141
Restriction enzymes
Recognize specific, palindromic, double-stranded DNA sections and then cuts the DNA backbones at those sequences. Isolated from bacteria, where their original purpose is to protect the bacteria from DNA viruses.
142
DNA libraries: genomic and cDNA
Large collections of known DNA sequences. Genomic libraries include exons (coding) and introns (noncoding). cDNA libraries contain sequences of DNA produces via reverse transcription of mRNA, contain no introns, AKA expression libraries
143
Hybridization
Joining of complementary base pair sequences. Can be DNA-DNA recognition or DNA-RNA. Vital part of PCR and Southern blotting
144
Gel electrophoresis of DNA
All DNA migrates towards positive anode because of neg backbone. Preferred gel is agarose gel. Longer strands of DNA migrate shorter distances
145
Southern blotting
Used to detec the presence and quantity of various DNA strands in a sample. After DNA fragments are separated using gel electrophoresis, they are transferred separately to a membrane. Membrane is then probed using many copies of single-stranded DNA. The probe will bind to its complementary sequence and form dsDNA. Probes are labelled with radioisotopes or indicator proteins, both of which can indicate the presence of a desired sequence.
146
DNA sequencing
Uses dideoxyribonucleotides and the ingredients of PCR to synthesize many fragments that all end in a dideoxyribonucleotide. Then gel electrophoresis is performed and then bases can then be read in order.
147
Transgenic mice
Altered at their germ line by introducing a cloned gene into embryonic stem cells. If the transgene is a disease-producing allele, the mice can be used to study the progression of the disease from early embryonic development through adulthood
148
Knockout mice
Mice in which a gene has been intentionally deleted to determine whether the cut-out gene is desease-inducing.
149
Gap Junctions
Allow rapid exchange of ions or small molecules between adjacent cells. Cells are held together by pores made of connexin which connect the cytoskeletons of the neighboring cells
150
Tight Junctions
Prevent paracellular transport (eg lateral transport through an epithelial layer of cells). Prevents fluid leakage. Consist of a continuous band around the cell. Create a transepithelial voltage difference due to differing ion concentrations
151
Desmosomes
Bind adjacent cells by anchoring to their cytoskeletons. Formed by transmembrane proteins associated with internal intermediate filaments. Primarily found between epithelial cells
152
Hemidesmosomes
Attach epithelial cells to underlying structures, like basement membrane, or ECM
153
Two essential fatty acids for humans
alpha-linolenic acid and linoleic acid
154
Chylomicrons
Transport fatty acids in the form of triacylglycerols from the intestines
155
Glycerophospholipids
Mainly used for membrane synthesis. Can produce a hydrophilic surface on the layer of lipoproteins, like VLDL, a lipid transporter
156
Pinocytosis
Endocytosis of fluids or dissolved particles.
157
Phagocytosis
Endocytosis of large particles.
158
Clathrin
Vesicle-coated protein that is largely responsible for invagination of endocytosed particles coming into the cells
159
Nernst equation
E = RT/(zF) *ln ( [ion_out] / [ion_in] ) = 61.5/z log ( [ion_out] / [ion_in] )
E is the membrane potential
160
Goldman-Hodgkin-Katz equation
V_m = 61.5 * log( (P-Na*[Na+_out] + P-K*[K+_out] +P-Cl*[Cl-_in]) / (P-Na*[Na+_in] + P-K*[K+_in] +
P-Cl*[Cl-_out]) )
Calculates voltage of a membrane using the permeability of each ion
161
Cardiolipin
Major component of the inner mitochondrial membrane
162
Does the inner mitochondrial membrane contain cholesterol?
No, mainly cardiolipin
163
trans-phospholipids ____ the melting points / ____ the fluidity of the plasma membrane
increase; decrease
164
Types of sphingolipids
Ceramides, sphingomyelins, gangliosides, cerebrosides
165
Role of Waxes in Plasma Membrane
Stabilize and enforce rigidity of the plasma membrane by associating with the nonpolar tail region. Serve extracellular functions of waterproofing and protection
166
What type of molecule is responsible for the ABO blood typing system?
The ABO antigens on RBCs are sphingolipids than only differ by their carbohydrate sequences
167
GLUT2 transporter protein
Glucose transporter protein found in liver and pancreatic cells. Low affinity - cannot be saturated under normal physiologic conditions. Takes glucose into liver cells as a function of blood glucose levels (first-order kinetics). Acts as a glucose sensor in the beta-islet cells of the pancreas in order to signal proper insulin release
168
GLUT4
Glucose transport proteins on adipose and muscle cell surfaces. K_m is very close to physiologic glucose concentration, so they are almost always saturated. Cells increase rate of transport through GLUT4s by increasing the number of them on the surface. Insulin triggers vesicles to migrate to the inner surface of the plasma membrane and insert more GLUT4s.
169
Hexokinase
First enzyme of glycolysis in most tissues. Phosphorylates glucose to glucose 6-phosphate in order to prevent a GLUT transporter from removing the glucose from the cell.
170
Glucokinase
Induced by insulin. Found in liver and beta-islet pancreatic cells - is the first second enzyme involved in glycolysis here. Phosphorylates glucose in order to prevent GLUT from removing it from the cell
171
PFK-1
The main rate-limiting enzyme in glycolysis. Converts fructose-6-phosphate to fructose-1,6-bisphosphate using ATP. Inhibited by citrate and ATP, so that the cell stops glycolysis once energy is sufficient. It is activated by AMP, so the glycolysis starts when there is a great need for energy. Activated by insulin and inhibited by glucagon, both indirectly and involving PFK-2
172
PFK-2
Indirectly activates PFK-1 by converting fructose 6-phosphate to fructose 2,6-bisphosphate, which then activates PFK-1, regardless of ATP levels, which means that energy production can continue even though energy levels are sufficiently high. Activated by insulin and inhibited by glucagon.
173
Glyceraldehyde-3-phosphate dehydrogenase
Catalyzes an oxidation and addition of P_i to glyceraldehyde-3-phosphate. Produces 1.3-bisphosphoglycerate and reduces NAD+ to NADH
174
3-phosphoglycerate kinase
Engages in substrate-level phosphorylation to generate ATP, also forming 3-phosphoglycerate from 1,3-bisphosphoglycerate and ADP. The only means of ATP production in anaerobic tissue.
175
Substrate-level phosphorylations in glycolysis
Performed on 1,3-bisphosphoglycerate to by 3-phosphoglycerate kinase, as well as on phosphoenolpyruvate to by pyruvate kinase.
Yield ATP. the only ATP-producing mechanism in glycoloysis alone
176
Pyruvate kinase
The last enzyme of glycolysis. Uses the high-energy intermediate, phosphoenolpyruvate to phosphorylate ADP, forming ATP. Activated in a feed-forward mechanism by F-1,6-BP (produced by PFK-1).
177
Lactate dehydrogenase
Key fermentation enzyme. Reduces pyruvate to lactate while oxidizing NADH to NAD+. This new NAD+ replenishes the supply of coenzymes for glyceraldehyde-3-phosphate dehydrogenase.
178
Dihydroxyacetone phosphate (DHAP)
Used in hepatic and adipose tissue for triacylglycerol synthesis. Formed from F-1,6-BPG. It can be isomerized back to glycerol 3-phosphate and then converted to glycerol (backbone of triacylglycerols)
179
Irreversible enzymes of glycolysis
Hexokinase, glucokinase, PFK-1, and pyruvate kinase
180
Glycolysis in RBCs
Only respiration is through glycolysis because RBCs do not have mitochondria.
181
Bisphosphoglycerate mutase
In RBCs, converts 1,3-BPG to 2,3-BPG. 2,3-BPG then binds to the beta-chains of Hb, decreasing its affinity for O2, thus releasing O2. Fetal RBCs do not have this enzyme, so O2-binding affinity of 2,3-BPG is quite high.
182
Sucrose
Disaccharide of glucose and fructose
183
Lactose
Disaccharide of glucose and galactose
184
Important enzymes of galactokinase
Galactokinase and galactose-1-phosphate uridyltransferase (an epimerase that converts galactose-1-phosphate to glucose-1-phosphate for glycolysis)
185
Fructose metabolism
Fructokinase, then cleavage into glyceraldehyde and DHAP by aldolase.
186
Pyruvate dehydrogenase complex (def. and cofactors)
Irreversible system that converts pyruvate to acetyl-CoA in prep for the citric acid cycle. Inhibited by acetyl-CoA, so that pyruvate is no longer converted to acetyl-CoA, rather, to oxaloacetate to enter gluconeogenesis.
Cofactors: thiamine pyrophosphate, lipoic acid, CoA, FAD, and NAD+
187
The three fates of pyruvate (and the relevant enzymes)
Conversion to acetyl-CoA by pyruvate dehydrogenase
Conversion to lactose by lactase dehydrogenase
Conversion to oxaloacetate by pyruvate carboxylase
188
Differing roles of glycogen in liver and skeletal muscle tissues
Liver: broken down to replenish blood glucose levels
Skel muscle: broken down for fuel for the muscle during exercise
189
Glycogen synthase
The rate-limiting enzyme of glycogenesis. It forms the a-1,4-glycosidic bond in LINEAR glycogen. Stimulated by insulin and glucose-6-phosphate. Inhibited by epinephrine and glucagon.
190
Branching enzyme
Enzyme in glycogenesis that forms the a-1,6 glycosidic bond essential for glycogen to branch. Mechanism involves cleavage of existing linear glycogen at an a-1,4 glycosidic bond to free an oligoglucose, then moves the freed piece to a new location and creates the new 1,6 bond.
191
Glycogen phosphorylase
Rate-limiting enzyme of glycogenolysis. Breaks a-1,4-glycosidic bonds between glucose using inorganic phosphate, thus releasing glucose from the granules. In liver, it is activated by glucagon. In muscle, it is activated by AMP and epinephrine. It is inhibited by ATP.
192
Debranching enzyme
Made up of two enzymes for the multi-step process of breaking down branched glycogen: the first a-1,4 bond on the branch adjacent to the branch point is broken, and then the new oligoglucose is moved to the exposed end of the chain where a new a-1,4 bond is formed. The a-1,6 bond is then cleaved and a single residue is released
193
Isoforms
Slightly different versions of the same protein from the same gene. Results from alternative splicing (different combinations of exons), so the nucleic acid and amino acid sequences differ
194
Substrates for Gluconeogenesis
Glycerol-3-phosphate from triacylglycerols
Lactate from anaerobic respiration
Glucogenic amino acids (all except Leu and Lys, from muscle proteins)
195
Glucoenogenesis
Mainly occurs in the liver. Keeps glucose levels up during fasting.
196
Alanine aminotransferase
Converts alanine to pyruvate for gluconeogensis
197
Pyruvate carboxylase
Mitochondrial enzyme that converts pyruvate to oxaloacetate due to high levels of Acetyl-CoA (sourced from fatty acids).
198
PEPCK: phosphoenolpyruvate carboxykinase
Converts oxaloacetate to phosphoenolpyruvate using GTP for gluconeogenesis. PEP then continues on the F-1,6-BP. Circumvents the pyruvate kinase step of glycolysis.
199
Fructose-1,6-bisphosphatase
Key control point of gluconeogenesis, rate-limiting. Reverses the action of PFK-1 in that it converts F-1,6-BP to fructose-6-phosphate. Inhibited by AMP and F-2,6-BP. Activated by ATP (makes sense because sufficient ATP signifies that the cell is energetically well-off and able to produce glucose for other cells in the body).
PFK-2, which is activated by insulin, forms F-2,6-BP, so high amount of sugar in the blood increases insulin levels, which increases F-2,6-BP levels, which decreases the rate of gluconeogenesis by inhibiting F-1,6-bisphosphatase
200
Glucose-6-phosphatase
Converts glucose-6-phosphate to glucose. Circumvents glucokinase and hexokinase. Only present in lumen of the ER in liver cells. The fact that it is not present in skeletal muscle cells shows that glycogen in these cells is not a source of glucose for the blood, only for the muscle.
201
Gluconeogenesis requires expenditure of ___ produced by ____ of fatty acids
ATP; beta-oxidation
202
Pentose Phosphate Pathway / Hexose Monophosphate Shunt
Occurs in cytoplasm. Serves to prodcue NADPH and as a source of ribose-5-phosphate for nucleotide synthesis
203
G6PD in PPP
The rate-limiting enzyme of the PPP. Converts glucose-6-phosphate into 6-phosphogluconate. Induced by insulin because PPP is classified as a glucose-storage pathway. It is inhibited by NADP+.
204
Second part of the PPP
Starts with ribulose 5-phosphate and ends with ribose 5-phosphate for nucleotide synthesis, as well as products that are also glycolytic intermediates, so they feed into glycolysis.
205
Transketolase and Transaldolase in PPP
Synthesize pentoses from glycolytic intermediates
206
Functions of NADPH
A potent reducing agent. Aids in synthesis of fatty acids and cholesterol, cellular bleach production in some WBCs, and maintenance of reduced glutathione supply (the body's natural antioxidant)
207
Glutathione
A reducing agent that is the body's natural antioxidant by reversing radical-formation before they can damage cells (specifically cell membranes). Protects the body from radical oxidative damage caused by peroxides.
208
Formation of Acetyl-CoA from CoA
Covalent attachment of an acetyl group to CoA-SH at the sulfur, thus forming a thioester (which is high energy)
209
Pyruvate dehydrogenase
PDH. Oxidizes pyruvate, forming CO2, while the remaining two C's bind covalently to thiamine pyrophosphate (TPP, vitamin B1). Mg2+ is also required
210
Dihydrolipoyl transacetylase
Second enzyme in pyruvate dehydrogenase complex. It oxidizes the product of PDH and transfers it to lipoic acid (its coenzyme) where it is oxidized again to create an acetyl group that is thioester-linked to lipoic acid. Then dihydrolipoyl transacetylase catalyzes the CoA-SH interaction with the newly formed thioester, transferring the acetyl group to form acetyl-CoA. Lipoic acid is left in its reduced form
211
Dihydrolipoyl dehydrogenase
Third enzyme in the pyruvate dehydrogenase complex. Its coenzyme FAD is used to reoxidize lipoic acid (resetting it), which reduces FAD to FADH2
212
Carnitine
Carries an acyl group from a cytosolic CoA-SH to a mitochondrial CoA-SH because the whole molecules cannot traverse the mitochondrial membrane. Group is transferred to and from carnitine via transesterification.
213
Methods of Acetyl-CoA formation
Pyruvate dehydrogenase complex (after glycolysis), beta-oxidation, amino acid catabolism, reversal of ketone-body formation, and conversion of alcohol
214
How is Acetyl-CoA formed from amino acids?
Ketogenic amino acids lose their amino group via transamination, and then a ketone body can be formed from the C skeleton. Ketone bodies can be converted to Acetyl-CoA
215
Formation fo acetyl-CoA from alcohol
Upon buildup of alcohol, it is catalyzed by alcohol dehydrogenase and acetaldehyde dehydrogenase.
216
Substrates of the Citric Acid Cycle
PCIKSSFMO:
pyruvate, citrate, isocitrate, a-ketoglutarate, succinyl-CoA, succinate, fumarate, malate, oxaloacetate
217
Citrate formation in CAC
Condensation of acetyl-CoA and oxaloacetate to form intermediate citryl-CoA. Hydrolysis of citryl-CoA yields citrate and CoA-SH via citrate synthase. This step helps propel the cycle forward
218
Aconitase
Catalyzes the isomerization of citrate to isocitrate by switching an H and an OH on citrate, achieved by dehydration and then re-hydration of a different C. The enzyme requires Fe2+
219
Isocitrate dehydrogenase
The rate-limiting enzyme of the citric acid cycle. Catalzyes the formation of oxalosuccinate from isocitrate, which is then decarboxylated to form a-ketoglutarate and CO2. This step also produces the first NADH
220
Mechanism of dehydrogenases
Transfer of a Hydride ion to an electron acceptor, usually NAD+ or FAD. Dehydrogenases are a form of oxidoreductases
221
a-ketoglutarate dehydrogenase complex
Catalyzes the formation of succinyl CoA from a-ketoglutarate in a method similar to PDH complex. Also results in the second and final CO2 formed in the CAC and reduces another NAD+ to NADH
222
Synthetase vs Synthase
Both form new covalent bonds, but synthetases require the input of energy whereas synthases do not
223
Succinyl-CoA Synthetase
The reverse of the synthesis reaction of this enzyme forms succinate from succinyl-CoA by hydrolyzing the thioester bond. Since thioesters require high energy input to form, this energy is released upon cleavage and is used to phosphorylate GDP to GTP, which then phosphorylates ADP to ATP.
224
During which reaction is ATP DIRECTLY formed in the citric acid cycle?
ONLY during the reaction that forms succinate from succinyl-CoA via the enzyme succinyl dehydrogenase
225
Succinate dehydrogenase
Catalyzes the oxidation of succinate to form fumarate, the only step that does not occur in the mitochondrial matrix because this enzyme is an integral membrane protein so it occurs on the inner membrane instead. During this reaction, FAD is reduced to FADH2.
226
Fumarase
Catalyzes the formation of an alkene bond in fumarate to yield malate. Both enantiomers are possible, but only L-malate forms in the body
227
Malate dehydrogenase
Catalyzes the oxidation of malate to form oxaloacetate. Reduces the third and final NAD+ to NADH.
228
Yield of ATP from one molecule fo glucose
25 ATP after CAC and ETC are complete
229
Describe regulation of Pyruvate Dehydrogenase
When the cell is energetically satisfied, the high levels of ATP signal pyruvate dehydrogenase kinase to phosphorylate the enzyme, thus inhibiting it. But when ADP levels are high, pyruvate dehydrogenase phosphatase dephosphorylates PDH, thus allowing the production of Acetyl-CoA for progression of the CAC. Also, high levels of Acetyl-CoA iteself can inhibit PDH
230
Control points of the Citric Acid Cycle
Citrate synthase, isocitrate dehydrogenase, and a-ketoglutarate dehydrogenase complex.
All are regulated by allosteric inhibitors or activators
231
Inhibitors of citrate synthase
ATP, NADH, Acetyl-CoA, and succinyl-CoA. All are allosteric
232
Regulation of isocitrate dehydrogenase
All are allosteric
Inhibitors: ATP and NADH
Activators: ADP and NAD+
233
Regualtion of a-ketoglutarate dehydrogenase complex
All allosteric.
Inhibitors: succinyl-CoA, NADH, ATP
Activators: ADP, Ca2+
234
Driving force behind the electron transport chain
Proton-motive force created by the proton gradient across the inner mitochondrial membrane
235
Describe the general mechanism of the electron transport chain
High-energy electron carriers from the citric acid cycle, NADH and FADH2, transfer their electrons to proteins on the inner mitochondrial membrane. Eventually, the electrons are given to O2 as H- ions, which forms water. The energy released from the transporting of electrons facilitates H+ ion transport across the membrane, intensifying the gradient, which allows for ATP synthesis via ATP synthase.
Based on the fact that ATP formation is endergonic and electron transport is exergonic
236
Complex I of the ETC
NADH-CoQ oxidoreductase. NADH transfers its electrons over to FMN to form FMNH2, which then becomes oxidized with sulfur. Then the Fe-S subunit is reduced and the electrons are transferred to CoQ (ubiquinone) to form CoQH2. Results in 4 protons being moved into the intermembrane space
237
Complex II of the ETC
Succinate-CoQ oxidoreductase. Succinyl-CoA transfers its electrons to FAD, which is covalently bonded to Complex II and is then converted to FADH2. FADH2 then reduces an Fe-S protein. Final step is reoxidation of the Fe-S protein and transfer of electrons to ubiquinone. No H pumping occurs here
238
Complex III of the ETC
AKA: cytochrome reductase. Facilitates the transfer of e from ubiquinone to cytochrome c. Each molecule of cytochrome c can only accept one electron, so one molecule of CoQH2 with two electrons requires two cytochrome c molecules. Contributes to the proton gradient through the Q cycle
239
Q cycle
Part of Complex III of the ETC that displaces four protons into the intermembrane space
240
Cytochromes
Proteins with heme groups that have iron ions that get reduced to Fe2+ and then reoxidized to Fe3+
240
Cytochromes
Proteins with heme groups that have iron ions that get reduced to Fe2+ and then reoxidized to Fe3+
241
Cpomplex IV of the ETC
Transfer of electrons from cytochrome c to oxygen (the final acceptor) by way of cytochromes a and a3 and Cu2+
242
Why are NADH shuttles required? What are the different types?
They are needed because NADH produced in glycolysis cannot directly cross the mitochondrial membrane.
Specific examples include: glycerol-3-phosphate shutter, malate-aspartate shuttle
243
F0 and F1 portions of ATP synthase
This is the transmembrane portion of the protein that houses the ion channel. As protons flow through here, F1 portion of the protein utilizes the energy being released from the electrochemical gradient to phosphorylate ADP to ATP
244
Chemiosmotic coupling
There is a direct relationship between the electrochemical gradient and the synthesis of ATP
245
Conformational coupling (ATP synthase)
Suggests that electrochemical gradient and ATP synthesis are indirectly related in that the F1 portion of ATP synthase is motivated to rotate like a turbine when H+'s pass through F0. The turbine mechanism is a conformational change in the protein that causes P and ADP to be forced together and bonded
246
Key regulators of oxidative phosphorylation (and other side regulators)
O2 (key!): when O2 is low, ATP synthase activity is relatively low
ADP (key!): when O2 is in sufficient supply, rate of ATP synthesis is determined by ADP. Low ADP signals ATP synthesis to increase
Others: NADH (buildup causes ATP synthase to
247
How is O2 consumption affected in a patient who was exposed to a toxin that increases permeability of the inner mitochondrial membrane to H+?
O2 consumption would increase because the electrochemical gradient will not be as intense due to the increased permeability, so ATP synthesis per molecule of glucose will be less efficient, thus requiring more O2 use to meet the body's ATP needs
248
Tricarboxylic acid cycle
Another name for the Citric Acid/Krebs cycle
249
In what form do fatty acids enter the catabolic pathway?
Describe the mechanism
acetyl-CoA
Mechanism: fat from adipose tissue can be hydrolyzed by lipases to form fatty acids and glycerol. Fatty acid can then be activated in the cytoplasm by coupling to CoA-SH and forming acyl-CoA. Acyl-CoA is then attached to a carnitine transporter to cross the inner mitochondrial membrane. Then transfer of from carnitine occurs to reform acyl-CoA, which can then undergo beta-oxidation to form acetyl-CoA that can enter the CAC
250
Nucleosidediphosphate kinase
Phosphorylates GDP to GTP during succinate formation in the CAC
251
Digestive enzymes/mixtures that aid in the digestion of dietary fats
Bile (bile salts, cholesterol, pigments), pancreatic lipase, colipase, and cholesterol esterase
252
How are lipids absorbed from the digestive tract?
After emulsification in the small intestine, the fragments form micelles that are able to diffuse through the brush border of the mucosal cells of the small intestine where they are then absorbed into the mucosa and re-esterified.
The re-resulting triacylglycerols and cholesteryl-esters are then packaged into chylomicrons which can exit the intestine via lacteals (lymphatic system) or enter the bloodstream through the thoracic duct
253
Hormone-sensitive lipase
An enzyme that is triggered at night time by a fall in insulin levels. Hydrolyzes triacylglycerols in adipose cells to yield fatty acids and glycerols. May also be activated by epinephrine and cortisol.
NOT subject to regulation by gluagon
254
Lipoprotein lipase (LPL)
Metabolizes chylomicrons and VLDL to release free fatty acids
255
Albumin
Transport protein that carries free fatty acids (and other nonpolar molecules) through the blood
256
Lipoproteins
Rank them from least to most dense
Aggregates of apolipoproteins and lipids. Carry cholesterol and triacylglycerols (varying amounts depending on the type of lipoprotein) around the blood.
Increasing density: chylomicrons, VLDL, IDL, LDL, HDL
257
Chylomicrons
Lipoproteins that mainly transport dietary triacylglycerols, cholesterol, and cholesteryl esters from the intestines to tissues. Least dense of the liprproteins
258
VLDL
Lipoproteins that carry triacylglycerols and fatty acids from liver to tissues
259
IDL
Intermediate density lipoproteins. They are remnants of VLDL. They pick up cholesteryl esters from HDL to become LDL (increase in density). They get picked up by the liver
260
LDL
Delivers cholesterol to the cells
261
HDL
PIcks up cholesterol accumulating in the blood vessels and delivers it to liver and steroidogenic tissues. Transfers apolipoproteins to other lipoproteins
262
Apoproteins
The protein component of lipoproteins. They are receptor molecules involved in signaling
263
De novo cholesterol synthesis
Relevant enzymes and reactants that drive it?
What triggers the process?
Occurs in the liver. It is driven by Acetyl-CoA and ATP. The rate-limiting step has the enzyme HMG-CoA reductase that yields mevalonic acid.
Triggers: low cholesterol, high insulin, and upregulation of the HMG-CoA reductase gene
264
LCAT
Enzyme activated by HDL in the bloodstream that adds a fatty acid to cholesterol --> yields soluble cholesteryl esters like those in HDL
265
CETP
Enzyme that facilitates transfer of cholesteryl esters from HDL to IDL so that it becomes LDL.
266
Fatty acids (def. and nomenclature)
Long-chain carboxylic acids
Naming: carbons:double bonds, further specified with the # of the first C of the unsaturated bond and the isomerization
267
Essential fatty acids
alpha-linolenic acid and linoleic acid
268
Citrate lyase
Splits excess citrate from the citric acid cycle back into acetyl-CoA and oxaloacetate. Located in the cytoplasm
269
Acetyl-CoA carboxylase
Key rate-limiting enzyme in fatty acid synthesis. It adds CO2 to acetyl-CoA to form malonyl-CoA. It is activated by citrate and insulin
270
The product of de novo fatty acid synthesis
Palmitic acid / palmitate
271
Palmitate synthase
Commonly called fatty acid synthase: a large multienzyme complex found in the cytosol that is rapidly activated following insulin-rise after a big meal
Substrates and coenzymes: 8 acetyl-CoA molecules, pantothenic acid (vitamin B5), NADPH
272
Steps of Palmitate Synthase
Attachment of acetyl-CoA to acyl carrier protein
Bond formation between activated malonyl-CoA and growing fatty acid chain
Reduction of double bond
Dehydration
Reduction of double bond
273
Fatty-acyl-CoA-synthetase
Activates fatty acids for beta-oxidation by attaching them to acyl-CoA
274
Carnitine acytransferase I
Rate-limiting enzyme of fatty acid oxidation. Shuttles fatty acids that over 12 Cs long into the mitochondria
275
Products of one round of beta--oxidation
1 acetyl-CoA and the freshly reduced NADH and FADH2
275
Products of one round of beta--oxidation
1 acetyl-CoA and the freshly reduced NADH and FADH2
276
Steps of beta-oxidation
1. Oxidation of the fatty acid to form a double bond
2. Hydration of the double bond to form a hydroxyl group
3. Oxidation of the OH to form a beta-ketoacid (a carbonyl)
4. Splitting of the beta-ketoacid to form acetyl-CoA and a shortened acyl-CoA
277
What is the three-C product formed at the end of odd-chain beta-oxidation
propionyl-CoA
278
Enoyl-CoA isomerase
Enzyme that converts a 2,3-cis double bond in unsaturated fatty acids to 3,4-trans, which allows beta-oxidation to occur
279
2,4-dienoyl-CoA reductase
Enzyme involved in the oxidation of unsaturated fatty acids. Mechanism involves converted two conjugated double bonds into one double bond, so that it can undergo isomerization by enoyl-CoA isomerase and then beta-oxidation
280
Ketone bodies
What are the major two that arise from acetyl-CoA, yielded by beta-ox?
Essentially transportable forms of acetyl-CoA. Can be broken down as fuel by cardiac and skeletal muscle, and in extreme fuel shortages, the brain
Major two: acetoacetate and 3-hydroxybutyrate
281
Ketogenesis (def. and major enzymes)
Production of ketone bodies. Occurs in the mitochondria of liver cells. Triggered by buildup of acetyl-CoA in the blood.
Major enzymes: HMG-CoA synthase, HMG-CoA lyase
282
Ketolysis (def. and major enyzmes)
Catabolism of ketone bodies. Major enzyme is thiophorase. The liver lacks this enzyme so that it cannot breakdown the keton bodies it produces
283
Pancreatic proteases
Trypsin, chymotrypsin, and carboxypeptidases A and B
284
Pepsin
Begins breakdown of proteins in the stomach
285
Proteolytic enzymes in the brush-border of the small intestine
Dipeptidase and aminopeptidase
286
Method of amino acid transport out of intestinal lumen
Secondary active transport linked to Na+
287
Method of transport of amino acids from epithelial cells into bloodstream
Facilitated diffusion
288
Glucogenic amino acids
Can become glucose via gluconeogenesis
Includes all of them except leucine and lysine
289
Ketogenic amino acids
Can be converted into ketone bodies and acetyl-CoA. There are 7 of them:
Leu, Lys, Ile, Phe, Trp, Tyr, Thr
290
Transamination
AKA deamination, which is the process by which amino acids lose their amino groups and are left a C-skeletons. The Carbon skeleton can then be used as metabolic fuel
291
Urea Cycle
Pathway the body uses to eliminate ammonia in the form of urea because ammonia is toxic
292
Where does the bulk of protein digestion occur?
Small intestine (brush-border enzymes!)
293
What is the fate of long-chain fatty acids contained in micells?
They are packaged into chylomicrons and then released into the lymphatic system through lacteals
294
In which process is hormone-sensitive lipase active?
Fatty acid mobilization
295
Nomenclature of the fatty acid synthesized in the body (C:double bonds)
16:0
| Palmitic acid
296
Location of ketogenesis
In the mitochondria of liver cells during a prolonged fast
297
What ketone bodies does the human body produce? Which are used for fuel?
Acetoacetate, 3-hydroxybutyrate, and acetone. Only the first two are used as fuel, whereas acetone is a byproduct
298
Enthalpy
Measures overall heat loss or gain of a system. At constant pressure and temp., it is equal to Q
299
Entropy (def and units)
Measure of a system's energy dispersion or degree of disorder. Units are J/K
300
Concentration of H+ at "modified standard state"
[H+] = 1e-7 M
pH = 7
301
Amount of energy yielded in combustion per gram of fat
9 kcal/g
302
Amount of energy yielded in combustion of one gram of carbohydrates/proteins/ketone bodies
4 kcal/g
303
delta G at modified standard state of ATP
-30.5 kJ/mol
304
Methods of ATP formation in the cell
Substrate-level phosphorylation and oxidative phosphorylation
305
Soluble high-energy electron carriers
NADH, NADPH, FADH2, ubiquinone, cytochromes, and glutathione
306
Flavin mononucleotide
An example of a membrane-bound electron carrier. Also known as FMN. It is bonded to complex I of the ETC.
307
Flavoproteins
Electron carriers that contain modified vitamin B2, or riboflavin. Also function as coenzymes in fatty acid oxidation, decarboxylation of pyruvate, and reduction of glutathione (a soluble electron carrier in the cytoplasm) . They are derived from nucleic acids. Two types: FMN and FAD
308
Postprandial state
AKA absorptive or well-fed state. Characterized by anabolism of fuel molecules rather than breakdown. Lasts about 3-5 hours after a big meal. Insulin levels are high and leads first to maximum glycogen synthesis and storage, and then to synthesis of fatty acids in the liver from excess glucose and protein synthesis in muscle
309
Which types of tissues are not sensitive to insulin?
Red blood cells, nervous tissue, kidney tubules, intestinal mucosa, and beta-cells of the pancreas
310
Postabsorptive state
AKA Fasting state. The following hormones increase in concentration in the body: glucagon, cortisol, epinephrine, norepinephrine, and growth hormone. They promote breakdown of glycogen and the release of glucose. Gluconeogenesis is also triggered in the liver, but is much slower than glycogenolysis
311
Prolonged state
AKA Starvation. Characterized by uniquely high levels of glucagon and epinephrine. Gluconeogenesis becomes the main source of glucose after glycogen stores have been depleted (about 24 hours of fasting). The brain adapts ketone bodies as its primary fuel source when levels of fatty acids and ketone bodies are high enough in the blood
312
Amino acid-derived hormones (def. and relative rate of affect)
Include thyroid hormones and steroid hormones. They are slower to effect change than peptide hormones but induce longer-lasting effects because their modifications are made at the transcriptional level.
313
Glucokinase
Enzyme in the liver that phosphorylates glucose as the first step in glycogen synthesis (increases glycogen storage). It is also the first enzyme of glycolysis in the liver. It is activated by insulin
314
Effect of insulin on fuel storage/mobilization
Insulin increases glycogen synthesis by activating glucokinase and glycogen synthase (which is the rate-limiting enzyme), and by inhibiting enzymes of glycogenolysis like glucose-6-phosphatase and glycogen phosphorylase.
Increases the uptake of amino acids by muscle cells to increase protein synthesis. It also decreases the formation of ketone bodies
Increases synthesis of triacylglycerols in the liver and fat tissue and decreases lipolysis in fat tissue.
315
Cells of origin of Glucagon
Primary target cells, too
Origin: alpha islet cells of the pancreas
Target: hepatocytes
316
Effects of glucagon
Increases in glycogenolysis and gluconeogenesis in order to raise the levels of blood glucose.
Increases ketogenesis and decreases lipogenesis.
Activates hormone-sensitive lipase in the liver, thus increasing breakdown of lipids, although the effect is indirect so glucagon is not considered a major fat-mobilizing hormone.
317
Triggers of glucagon release
Low blood glucose level.
High amino acid levels, especially basic amino acids
318
Glucocorticoids
Released from the adrenal cortex. Responsible for glucose mobilization for the fight or flight response. Main one is cortisol, released in response to stress -- it mobilizes energy stores via degradation. It also elevates blood glucose levels but also inhibits its uptake in tissue including muscle, lymphoid, and fat.
319
Effects of prolonged exposure of the body to cortisol
Hyperglycemia which stimulates insulin, which actually promotes fat storage in fat tissue, rather than breakdown.
320
Steroid hormone classes secreted by the adrenal cortex
Glucocorticoids, mineralocorticoids, and sex hormones
321
Catecholamines and their effect on metabolism
Released from the adrenal medulla and include epinephrine and norepinephrine. They act on the liver and skeletal muscle tissues to promote glycogenolysis, on adipose tissue to promote lipolysis, and epinephrine targets organs like the heart to increase basal metabolic rate
322
Difference in structures of epinephrine and norepinephrine
Epinephrine has a secondary amine whereas norepinephrine has a primary amine.
Think: Norepinephrine has the N at the eNd of a chain in its structure
323
Deiodonases
Enzymes that remove iodine from a molecule. Convert T4 to T3.
324
Thyroid hormones
T4 and T3. They increase BMR. Their specific main effects include increase of glucose uptake in the small intestine for metabolism in the cells. Also affect lipid metabolism and accelerate clearance of cholesterol from the plasma.
325
Sources of C-skeleton for glucose synthesis
Lactate (from anaerobic repspiration), glycerol (from triacylglycerols), and amino acids
326
Primary energy fuel for the liver in a well-fed state
Excess amino acids
327
Effects of insulin on adipose tissue
High insulin activates lipoprotein lipase --> causes release of triacylglycerols from VLDL and chylomicrons. Insulin also suppresses the release of triacylglycerols from adipose cells, thus promoting storage of fat.
Low insulin activates hormone-sensitive lipase, thus causing the release of triacylglycerols from adipocytes
328
Resting skeletal muscle's sources of fuel
Glucose and fatty acids.
329
Type of cellular respiration in skeletal muscle during short bursts of intense exercise
Anaerobic respiration reliant on muscle glycogen
330
Primary source of fuel of cardiac muscle cells
Fatty acids. May switch to ketones in the event of long fasting
331
Fuel sources of the brain during rest and fast
Rest and whenever possible: blood glucose
Fasting: glucose from hepatic glycogenolysis and gluconeogenesis, then ketones
Never fatty acids because they cannot cross the blood-brain barrier
332
Respiratory quotient
RQ = CO2 produced / O2 consumed
333
Hormones of hunger
Grehlin: increases appetite and stimulates release of orexin
Orexin: further increases appetite and plays a role in alertness/the sleep cycle. Can be triggered by hypoglycemia
Leptin: secreted by fat cells, suppresses orexin which decreases appetite
334
Equation for BMI
BMI = mass (kg) / [height (m)]^2
335
T/F: Hormonal control of glycolysis proceeds via noncovalent interactions
False - hormones exert their effect on glycolysis main via phosphorylation and dephosphorylation
336
Which tissues are most dependent on insulin for fuel uptake?
Resting skeletal muscle and adipose tissue
337
Homotropic regulation
Type of enzymatic reaction in which a particular molecule acts as both a substrate and a regulator of the given enzyme
338
O2 is the final electron acceptor in which metabolic process?
Electron transport chain
339
Arachidonic Acid
An essential fatty acid from which the body synthesizes eicosanoids (20-C omega-6 polyunsaturated fatty acids with four cis bonds), most importantly, prostaglandins.
340
Prostaglandins
A specific type of eicosanoids that have a divers range of effects, including the modulation of inflammation
341
Thromboxanes
A type of eicosanoid that is involved in the clotting cascade
342
Which of the following will be in high urine concentration during chronic hyperglycemia?
A: proteins
B: glucose
C: ketone bodies
B and C
343
Mnemonic for Purines and Pyrimidines (names and structure
"Pure As Gold" = adenine and guanine are the purines
so the other ones (cytosine, uracil, and thymine) are the pyrimidines, which are single rings making them more shaped like "pyramids"
344
Order the nitrogenous bases in order of decreasing molecular weight
G > A > T > U > C
345
Which amino acid residues are most commonly phosphorylated? Why?
Serine, Threonine, and Tyrosine.
Reason: they each bear a hydroxyl group, which is the preferred site of phosphorylation
346
Major products of the pentose phosphate pathway
NADPH and ribose-5-phosphate
