Kaplan Biochemistry Unknown Concepts Flashcards
1
Q
What is the stereochemistry of all chiral amino acids?
A
eukaryotes: alpha carbon is only L, all are S configuration exception cysteine (R)
D amino acids can exist in prokaryotes
2
Q
What is an alpha amino acid?
A
amino group and carboxyl group are bonded to the same carbon (alpha carbon of CA)
- average molar mass = 100 daltons (g/mol)
3
Q
Nonpolar, nonaromatic AA.
A
glycine, alanine, valine, leucine, isoleucine, methionine, proline
4
Q
Aromatic AA
A
tryptophan (W), phenylalanine (F), tyrosine (Y)
5
Q
Polar AA
A
serine, threonine, asparagine (Asn, N), glutamine (Gln, Q), cysteine
6
Q
Negatively charged (acidic AA)
A
aspartate (D), glutamate (E)
7
Q
Positively charged (basic AA)
A
lysine (K), arginine (R), histidine
8
Q
What is pKa?
A
the pH at which half of the species are deprotonated
[HA] = [A-]
carboxyl group of AA: 2
amino group of AA: 10
9
Q
What do titration curves of amino acids look like?
A
flat in areas of pKa (2, 9-10): buffering
vertical at pI: electrically neutral
10
Q
What are the different forms amino acids exist in depending on pH?
A
pKa > pH, fully protonated
pKa = pH = pI, neutral Zwitterion
pKa < pH, fully deprotonated
11
Q
How do you calculate the pI of a neutral amino acid? acidic amino acid? basic amino acid?
A
neutral: pKa(amino) + pKa(carboxyl) / 2
acidic: pKa(R group) + pKa(carboxyl) / 2
basic: pKa(R group) + pKa(amino) / 2
12
Q
Describe peptide bond formation.
A
amino group attacks carbonyl carbon in a condensation reaction (acyl substitution)
- synthesized N to C terminus
- amide group had delocalizable pi electrons which gives the NC partial double bond character
13
Q
Describe the bonds that hold secondary, tertiary, and quaternary protein structures together.
A
secondary: H-bonding between amino groups and non-adjacent carboxyl groups
- only step without covalent bonding
tertiary: hydrophobic interactions (nonpolar R groups to the interior for positive entropy), acid-base interactions (salt bridges), hydrogen bonding between R groups, and disulfide bonds (two cysteine residues are oxidized + covalent bond)
quaternary: interaction between peptides in proteins with multiple subunits
14
Q
What are the types of enzymes you have to know? What are the shared general characteristics of enzymes?
A
1) oxidoreductase: redox reactions
2) transferase: move functional group from one molecule to another
3) hydrolases: catalyze cleavage with water
4) lyases: catalyze cleavage without water and without transfer of electrons
5) isomerases: catalyze interconversion of isomers including constitutional and stereoisomers
6) ligases: joining to larger biomolecules
LIL HOT
unchanged by reactions and reusable
do not alter free energy (delta G) or enthalpy (delta H), they change RATE
15
Q
What is an exergonic reaction?
A
release energy, delta G is negative
16
Q
What is the difference between cofactors and coenzymes?
A
cofactors: inorganic molecules or metal ions
coenzymes: small organic compounds like vitamins, or derivatives of vitamins like NAD+, FAD, and CoA
17
Q
What does Km represent?
A
substrate concentration at which half of the enzyme’s active sites are full
- when comparing enzymes, the one with the higher Km has lower affinity for its substrate bc it require higher [S] to reach half saturation
18
Q
What is vmax?
A
enzyme maximum velocity; only increase by adding more E
vmax = [E]kcat
where kcat = turnover rate
19
Q
What is catalytic efficiency?
A
kcat/Km
- large kcat or small Km means high turnover with high affinity, more efficiency
20
Q
What is cooperative binding? What is Hill’s coefficient?
A
change in affinity for substrate based on binding
Hill’s coefficient
> 1: positive cooperative binding
- Hb, sigmoidal shape
= 1: NOT cooperative binding
< 1: negative cooperative binding
21
Q
What are the different types of reversible inhibition?
A
1) competitive: inhibitor similar to substrate binds to active site
- vmax is unchanged
- Km increases
2) noncompetitive: inhibitor binds with equal affinity to the enzyme and the enzyme-substrate complex; bind at allosteric site
- vmax is decreased
-Km unchanged
3) mixed inhibition: inhibitor binds with unequal affinity for enzyme and the enzyme-substrate complex; bind at allosteric site
- vmax decreased
- Km increased (enzyme) or decreased (ES) depending on affinity for enzyme vs. ES complex
4) uncompetitive inhibitor: inhibitor binds only with ES complex; bind at allosteric site
- vmax decreased
- Km decrease
22
Q
What are other ways enzymes activity is monitored?
A
allosteric sites occupied by activators, phosphorylation or glycosylation, zymogens (inactive form until cleaved)
23
Q
What do structural proteins do? What are the common ones?
A
compose the cytoskeleton, anchoring proteins, and the extracellular matrix
- collagen (connective tissue), elastin (connective tissue), keratin (epithelial cells), actin (+/- side), and tubulin (intracellular transport)
24
Q
What are motor proteins?
A
one or more heads capable of force generation through conformational change
- ATPase
functions: muscle contraction, vesicle movement within cells, and cell motility
- myosin, kinesin, dynein
25
What are cell adhesion molecules (CAM)?
allow cells to bind to other cells
- cadherins: calcium-dependent glycoproteins that hold similar cells together
- integrins: 2 membrane spanning chains that adhere to proteins in ECM
- selectins: adhere to carbohydrates on the surface of other cells
26
What does the activated alpha subunit of the G-protein do in the cell?
Gs : adenyl cyclase: increases cAMP levels
- Gi inhibits
phospholipase C: increases Ca2+ in cell
- Gq
27
What are the important sugars to know?
glucose
fructose
galactose
mannose
aldehydes = aldoses
ketones = ketoses
all monosaccharides are reducing sugars
28
What are epimers and anomers?
epimers: diastereomers that differ at one carbon
anomers: diastereomers that differ at the anomeric carbon
- mutarotation = switching between anomers
29
What are common disaccharides?
sucrose: glucose-alpha-1,2 fructose
lactose: galactose-Beta-1,4-glucose
maltose: glucose-alpha-1,4-glucose
30
What are the roles of the polysaccharides you need to know?
cellulose: main structural component of plant cell walls and is main source of fiber in human diet
- 1,4 linked beta-D-glucose
starches: function as main energy storage form for plants
- 1,4 linked alpha-D-glucose
glycogen: main energy storage form for animals
- 1,6 linked alpha-D-glucose
- highly branched, more soluble in solution, increase storage
31
How does saturation affect the lipid membrane?
saturated fatty acids are less fluid than unsaturated (double bond) ones
32
what is the difference between phospholipids and sphingolipids?
phospholipids: glycerol backbone, phosphodiester bond with head group, 2 FA tails
sphingolipids: sphingosine backbone, one fatty acid tail with amide bond
- can have phosphodiester linkgae or glycosydic linkage to sugar
33
What are sphingolipids?
contain a sphingosine (amino, 2 OH) backbone
- many, but not all are phospholipids, containing a phosphodiester bond with the head group
- sphingomyelins: contain phosphatidylcholine or phosphatidylethanolamine head group = myelin sheath
- glycosphingolipids: attached to sugar instead of phosphate (cerebroside have 1 sugar, globosides have two or more)
- gangliosides: contain oligosaccharides with one terminal NANA = "gangly"
34
What are waxes?
long-fatty acids esterified to long-chain alcohols
- used for protection against evaporation and parasites in plants and animals
35
What are terpenes?
odiferous steroid precursors made from isoprene, a 5C molecule
- 1 terpene unit = 2 isoprene units
36
What are steroids?
contain three cyclohexane rings and one cyclopentane ring
- steroid hormones: have high affinity receptors, work at low concentrations, and affect gene expression and metabolism
- cholesterol: keeps the membrane fluidity stable
37
What are prostaglandins?
autocrine and paracrine signaling molecules that regulate cAMP levels
- effects on smooth muscle contraction, body temperature, the sleep-wake cycle, fever, and pain
- NSAIDs inhibit COX, which aids in the production of prostaglandins
38
What are the fat-soluble vitamins?
A,D,E,K
- A, carotene: metabolized to retinal for vision
- D, cholecalciferol: metabolized to calcitriol in the kidneys and used to increase calcium and phosphate reabsorption in the intestines, promoting bone formation
- E, tocopherols: biological antioxidants; aromatic rings destroy free radicals
- K, -quinones: forming of prothrombin = clotting factor; creates calcium binding sites on proteins too
39
What is the preferred method of storing energy for long term use?
triacylglycerols
- contain one glycerol attached to three fatty acids via ester bonds
- the carbon atoms in lipids are more reduced than carbs (OH groups), giving twice as much energy during oxidation
- very hydrophobic, so don't carry any water weight
**Adipocytes in animals = cells used for storage of TG**
40
What is a nucleoside? nucleotide?
5 carbon sugar bonded to a nitrogenous base vs. nucleoside + 1-3 phosphates added
- nucleotides in DNA = deoxyribose
- nucleotides in RNA = ribose
adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) -- all aromatic
41
How is DNA organized?
backbone composed of alternating sugar and phosphate groups and is always read 5'-->3'
2 strands with antiparallel polarity
purines (A,G) always pair with pyrimidines (T/U, C)
- AT has 2 H bonds
- AU has 2 H bonds
- GC has 3 H bonds
42
What are the rules of aromaticity?
cyclic, planar, and conjugated: has alternating single and multiple bonds or lone pairs, creating at least one unhybridized p orbital (4n +2 pi electrons)
43
What processes occur 5' to 3' ?
DNA synthesis (read 3'-->5'), DNA repair, RNA transcription (read 3'-->5'), RNA translation (read 5'--3')
44
How is DNA stored in eukaryotic cells?
organized into 46 chromosomes
DNA is wound around histone proteins to form nucleosomes = chromatin
- heterochromatin: dense, transcriptionally silent DNA that appears dark
- euchromatin: less dense, transcriptionally active DNA that appears light
45
What are telomeres?
ends of chromosomes
- high GC content to prevent unraveling of DNA
- shorten during replication
46
How is DNA replicated?
semi-conservative: one parent one daughter strand
1) DNA unwound at origin of replication by helicases, producing two replication forks
- prokaryotes have 1 O.O.R bc circular
- eukaryotes can have many
2) single strands kept from re-annealing by ssDNA binding proteins
3) primase puts down RNA primer
4) DNA polymerase synthesize new strand; reading it 3' to 5' and synthesizing new strand 5' to 3'
- leading strand: only one primer, continuous synthesis
- lagging strand: many primers and is synthesized in Okazaki fragments
5) DNA ligase fuse DNA strands together
47
How is supercoiling relieved in DNA replication?
torsional strain relieved by nicking DNA with DNA topoisomerases
48
What are oncogenes and tumor suppressor genes?
oncogenes: mutations of protooncogenes promote cell cycling
- only one allele mutation required; dominant
- stepping on the gas
tumor suppressor genes: reduce cell cycling
- need both alleles to mutate; inactivation of both
- taking away the brakes
49
How does DNA repair?
1) during replication, DNA polymerase proofreads its work and excises incorrectly matched bases
- S phase
2) mismatch repair occurs during G2
3) nucleotide excision repair fixes helix-deforming lesions (thymine dimers) using excision endonuclease
- G1 or G2
4) base excision repair fixes nondeforming lesions by removing the base, leaving AP site; AP endonuclease removes sequence
- G1 or G2
50
What is DNA cloning?
introduces a fragment of DNA into a vector plasmid
1) restriction enzyme cuts both the plasmid and the fragment, left with sticky ends
2) once fragment binds to plasmid, it can replicate and generate many copies of the fragment of interest
*vectors have origin of replication, fragment of interest, and antibiotic resistance gene to select for it after*
51
What are DNA libraries?
large collections of known DNA sequences
1) genomic libraries: large fragments of DNA
2) cDNA libraries: smaller fragments, only the exons; used to make recombinant proteins or for gene therapy
52
What is hybridization ?
joining of complementary base pair sequences
1) PCR: DNA of interest denatured, replicated with primers and DNA poly from bacteria, cooled for reannealing. Each time DNA doubles
2) DNA separated by size using gel electrophoresis
3) Southern blotting: after electrophoresis, membrane with ssDNA molecules to look for sequence of interest
53
How does DNA sequencing work?
dideoxyribonucleotides: terminate DNA chain because they lack 3' -- OH group
- fragments separated by gel electrophoresis
54
What is gene therapy?
curing genetic deficiencies by introducing a functional gene with a viral vector
ex) retroviral gene replaced with human therapeutic gene, multiple virions produced, integrate into DNA
55
What is a transgenic mouse? knockout mouse?
created by integrating gene of interest into the germ line of a developing mouse
- organisms with cells from two different lineages = CHIMERAS
KO: delete gene of interest
56
What are the most important codons to know?
initiation (start): AUG
termination (stop): UAA, UGA, UAG
57
What can point mutations cause?
silent: no effect on protein synthesis
nonsense: produce a premature stop codon
missense: codon that codes for a different amino acid
58
What is a frameshift mutation?
nucleotide addition or deletion, and change the reading frame of subsequent codons
59
Difference between DNA and RNA?
RNA: substitution of ribose, uracil for thymine, and it is single-stranded
60
What are the three types of RNA in transcription?
mRNA: carries DNA info from nucleus to cytoplasm
tRNA: brings in amino acids and recognizes codon on the mRNA using its anticodon
rRNA: makes up the ribosome and is enzymatically active
61
What are the steps of transcription?
1) helicase unwinds DNA
2) RNA polymerase II binds to TATA box within the promoter region of the gene (25 bp upstream from first base)
3) hnRNA is synthesized from DNA template strand
- identical to coding strand
4) post-transcriptional modifications
- modified guanine/phosphate cap added to 5' end
- poly-A tail added to 3' end
- splicing done by snRNA and snRNPs in the spliceosome; exons ligated together
- alternative splicing = combining different exons to form different products
62
What are the steps of translation?
1) initiation: 40S ribosome attaches to the 5' cap and scans for the start codon; lays down methionine in the P site of the ribosome
2) elongation: addition of new aminoacyl-tRNA into the A site, peptide bond forms, ribosome slides to the right
3) termination: codon in A site is a stop codon; release factor place water molecule on the polypeptide chain and release the protein
4) post-translational modifications
- folding by chaperones
- formation of quaternary structure
- cleavage of proteins
- covalent addition of other biomolecules (phosphorylation, glycosylation, carboxylation)
63
how do you determine the anti-codon ?
codon is read 5' to 3'
anticodon is antiparallel and complementary
64
What are operons?
inducible or repressible clusters of genes transcribed as single mRNA
- inducible (lac): bonded to repressor under normal conditions (glucose); can be turned on by inducer (lactose) pulling repressor from operator site
- repressible (trp): transcribed under normal conditions; turned off by corepressor coupling with the repressor and their binding to the operator site
65
What are transcription factors?
search for promoter and enhancer regions in the DNA
- promoters: within 25 bps of transcription start site
- enhancer: more than 25 bps away from transcription start site
Ex) cAMP: Second messenger that activates PKA, triggering phosphorylation of CREB.
- CREB: Transcription factor that binds to cAMP response elements (CREs) in DNA = enhancers
- CREB recruits coactivators to boost transcription.
- CREB-regulated genes control metabolism and synaptic plasticity.
histone acetylation = increase accessibility to DNA
DNA methylation = decrease accessibility to DNA
66
Describe the outer and inner mitochondrial membrane.
outer: highly permeable to metabolic molecules and small proteins
inner: surround mitochondrial matrix where the CAC produces electrons used in the ETC
- no cholesterol
- less permeable
67
What is the difference between gap, tight junctions, and desmosomes?
gap: direct cell-cell communication
- permit movement of water and solutes between cells
tight: for a watertight seal, preventing paracellular transport of water and solutes
- lining of renal tubules
desmosomes: bind adjacent cells by anchoring their cytoskeletons
- found at interface between two layers of epithelial tissue
- hemidesmosomes attach epithelial cells to basement membrane
68
What is osmotic pressure?
colligative property = physical property of solutions that is dependent on the concentration of dissolved particles but not on the chemical identity of those particles
"sucking pressure"
pi = iMRT
- i: van't Hoff factor: number of particles obtained from the molecule when in solution
- molarity, ideal gas constant, temperature
69
Where is each GLUT receptor found?
GLUT2: found in the liver (glucose storage) and pancreatic B-islet cells (glucose sensor)
- high Km, low affinity
GLUT4: found in adipose tissue and muscle and is stimulated by insulin (increases # in the membrane)
- low Km, high affinity
70
What is glycolysis?
occurs in the cytoplasm of all cells and does not require oxygen
- yields 2 ATP per glucose, 2 NADH, and 2 pyruvate
71
What are dehydrogenases?
subtypes of oxidoreductases that transfer H- ion to electron acceptor (NAD+)
72
What are the important enzymes in glycolysis?
1) Glucokinase: converts glucose to glucose 6-phosphate in pacreatic B-islet cells as part of the glucose sensor; responsive to insulin in liver
- irreversible
- high Km
2) Hexokinase: converts glucose to glucose 6-phosphate in peripheral tissues
- irreversible
- low Km
3) Phosphofructokinase-1 (PFK-1): phosphorylates fructose 6-phosphate to fructose 1,6-biphosphate in the rate-limiting step of glycolysis
- irreversible
- activated by AMP and fructose 2,6-biphosphate
- inhibited by ATP and citrate
4) Phosphofructokinase-2 (PFK-2): produces F2,6-BP which activates PFK-1
- activated by insulin
- inhibited by glucagon
5) Glyceraldehyde-3-phosphate dehydrogenase: produces NADH
6) 3-phosphoglycerate kinase and pyruvate kinase: substrate-level phosphorylation (ADP to ATP)
73
Describe pyruvate dehydrogenase.
complex of enzymes that convert pyruvate to acetyl-CoA
- stimulated by insulin and inhibited by acetyl Co-A
- produces NADH
74
What happens with the NADH produced from glycolysis?
if oxygen, it is oxidized in ETC
if no oxygen, it is oxidized by lactate dehydrogenase
- RBCs, skeletal muscle
75
What happens in the cell with galactose and fructose?
galactose: comes from lactose in milk
- trapped in cells by galactokinase, converted to glucose 1-phosphate
fructose: comes from honey, fruit, sucrose
- trapped in cell by fructokinase, cleaved by aldolase B to form glyceraldehyde
76
How does glycogenesis work?
production of glycogen
1) glycogen synthase: creates alpha-1,4 glycosidic links between glucose molecules
- activated by insulin in the liver
2) branching enzyme: move a block of oligoglucose from one chain and adds it to the growing glycogen as a new branch using alpha 1,6-glycosidic link
77
How does glycogenolysis work?
breakdown of glycogen
1) glycogen phosphorylase: removes single glucose 1-phosphate molecules by breaking alpha-1,4 glycosidic links
- activated by glucagon in the liver
- activated by epinephrine and AMP in muscle
2) debranching enzyme: moves a block of oligoglucose from one branch and connects it to the chain using a alpha-1,4 glycosidic link
- removes branchpoint, releasing 1 free glucose
78
How does gluconeogenesis work?
occurs in cytoplasm and mitchondria of the liver; reverse of glycolysis
1) pyruvate carboxylase: convert pyruvate into oxaloacetate
- activated by acetyl CoA from B-oxidation
2) phosphoenolpyruvate carboxykinase (PEPCK) converts oxaloacetate into phosphoenolpyruvate
- activated by glucagon and cortisol
3) fructose-1,6-bisphosphatase: converts fructose 1,6-biphosphate to fructose 6-phosphate
- rate limiting step, activated by ATP
4) glucose-6-phosphatase: converts glucose 6-phosphate to free glucose
- only in liver
79
What is the pentose phosphate pathway?
occurs in cytoplasm, generating NADPH and sugars for biosynthesis (ribose 5-phosphate)
- rate limiting enzyme is glucose-6-phosphate dehydrogenase, activated by NADP+ and insulin
80
What are the rate limiting enzymes in glycolysis, fermentation, glycogenesis, glycogenlysis, gluconeogensis, and PPP?
glycolysis: phosphofructokinase-1
fermentation: lactate dehydrogenase
glycogenesis: glycogen synthase
glycogenlysis: glycogen phosphorylase
gluconeogensis: fructose 1,6-biphosphatase
PPP: glucose 6-phosphate dehydrogenase
81
What are the irreversible steps of glycolysis?
hexokinase
glucokinase
PFK-1
pyruvate kinase
82
What is acetyl-CoA?
contains high energy thioester bond used to drive other chemical reactions
- formed from pyruvate via pyruvate dehydrogenase complex = 5-enzyme complex in mitochondrial matrix
1) pyruvate dehydrogenase (PDH) oxidizes pyruvate, creating CO2
2) dihydrolipoyl transacetylase oxidizes the remaining two-carbon molecule using lipoic acid, and transfers resulting acetyl group to CoA
FAD gets reduced into FADH2--> NADH --> ETC
83
How is acetyl-CoA formed from fatty acids?
1) fatty acid couples with CoA in cytosol to form fatty acyl-CoA, which moves into the intermembrane space
2) acyl group is transferred to carnitine to form acyl-carnitine, crossing the inner membrane
3) acyl group is transferred to mitochondrial CoA --> fatty acyl-CoA--> beta oxidation --> acetyl-CoA
84
How else can acetyl-CoA be formed?
carbon skeletons of ketogenic amino acids, ketone bodies, and alcohol
85
Describe the citric acid cycle.
mitochondrial matrix; oxidizes carbons in intermediates to CO2 and generate NADH, FADH2, and GTP
86
What are the key enzymes of the citric acid cycle?
1) citrate synthase: couples acetyl-CoA to oxaloacetate and then hydrolyzes resulting product, forming citrate and CoA-SH
- negative feedback from ATP, NADH
2) Aconitase: isomerizes citrate to isocitrate
3) Isocitrate dehydrogenase: oxidizes and decarboxylates isocitrate to form alpha-ketoglutarate
- first CO2 and NADH of cycle
- RATE LIMITING STEP; ATP and NADH inhibitors
4) succinyl-CoA synthetase: hydrolyzes thioester bond ni succinyl-CoA to form succinate and CoA-SH
- one GTP
5) Succinate dehydrogenase: oxidizes succinate to form fumarate
- FADH2
6) Fumarase: hydrolyzes the alkene bond of fumarate, forming malate
7) malate dehydrogenase: oxidize malate to form oxaloacetate
- NADH
87
Describe the electron transport chain.
matrix-facing surface of the inner mitochondrial membrane
- NADH donates electrons to the chain, reduction potential increases until O2 receives electrons at the end
Complex I: NADH dehydrogenase
- Accepts electrons from NADH, oxidizing it to NAD⁺.
- Transfers electrons to ubiquinone (coenzyme Q), reducing it to ubiquinol.
- Pumps 4 protons (H⁺) from the mitochondrial matrix into the intermembrane space, creating a proton gradient.
Complex II: succinate dehydrogenase
- transfer electrons from succinate to FAD
- transfers electrons from FADH₂ to ubiquinone, reducing it to ubiquinol.
- Does not pump protons
Complex III: cytochrome c
- Transfers electrons from ubiquinol to cytochrome c as part of Q cycle
- Pumps 4 protons (H⁺) into the intermembrane space
Complex IV:
- Accepts electrons from cytochrome c and transfers them to molecular oxygen (O₂), reducing it to water (H₂O).
- Pumps 2 protons (H⁺) into the intermembrane space
88
How are the electrons from NADH transferred into the inner mitochondrial membrane?
glycerol 3-phosphate shuttle: electrons transferred to DHAP --> FAD--> FADH2
malate-aspartate shuttle: electrons transferred to oxaloacetate, forming malate-->mitochondrial NAD+ --> NADH
89
How is ATP generated in oxidative phosphorylation?
ATP synthase: protons flow back into the mitochondrial matrix, generating ATP from ADP + Pi using the energy from the gradient
90
Summarize the total energy yield from each metabolism process.
1) glycolysis: 2 NADH, 2 ATP
2) pyruvate dehydrogenase: 2 NADH from one glucose
3) CAC: 6 NADH, 2 FADH2, and 2 GTP per glucose
Each NADH = 2.5 ATP; 10 NADH = 25 ATP
Each FADH2 = 1.5 ATP; 2 FADH2 = 3 ATP
GTP converted to ATP = 2
TOTAL = 2 ATP (glycolysis) + 2 ATP (CAC) + 25 (NADH) + 3 (FADH2) = 32 ATP / molecule of glucose
91
How are lipids digested?
small intestine facilitated by bile and pancreatic lipase
- short FA absorbed across intestine into blood
- long FA absorbed as micelles and assembled into chylomicrons for release in the lymphatic system
92
How are lipids mobilized?
from adipocytes by hormone-sensitive lipase
from lipoproteins by lipoprotein lipase
93
How are lipids transported?
chylomicrons: dietary triacylglycerol/cholesterol via lymphatic system
VLDL: newly synthesized TAG from liver to peripheral tissues
LDL: transports cholesterol into cells
HDL: picks up cholesterol accumulating in blood vessels; delivers to liver
94
How are fatty acids synthesized?
in the cytoplasm from acetyl-CoA
- activation, bond formation, reduction, dehydration, reduction
- repeated 8 times to form palmitic acid (16:0) = only FA humans can synthesize
95
What is fatty acid oxidation?
in the mitochondria following transport by carnitine shuttle
- oxidation, hydration, oxidation, cleavage
- produces one NADH, FADH2, and acetyl-CoA
- each cycle removes 2 carbons, producing shorter acyl-CoA and acetyl-CoA
**unsaturated FA need isomerase and reductase during this**
96
What are ketone bodies?
fat for energy during prolonged starvation due excess acetyl-CoA in the liver
97
What is the difference between open and closed systems?
open: matter and energy can be exchanged with the environment
closed: only energy can be exchanged with the environment
- changes in enthalpy = change in internal energy = heat exchange within the environment, deltaU = Q
- no work is performed (PV and constant)
98
What are flavoproteins?
subclass of electron carriers that are derived from vitamin B2
99
What is the difference between postprandial state and postabsorbative state?
absorbative (well-fed): insulin secretion is high and anabolic metabolism pathway prevails
postabsorbative (fasting): insulin secretion decreases while glucagon and catecholamine increases
- catabolic catabolism
100
What do insulin glucagon do?
insulin: decrease in blood glucose, increase in anabolic metabolism
glucagon: increases blood glucose by increasing gluconeogenesis and glycogenlysis in the liver
101
What do glucocorticoids do?
increase blood glucose in response to stress by mobilizing fat stores and inhibiting glucose uptake
102
Describe the difference between T3 and T4.
T3 is more potent than T4, but has shorter half life
- T4 converted to T3 at tissues
103
What does each tissue type prefer in terms of metabolism?
Liver: hepatocytes maintain blood glucose by glycogenlysis and gluconeogenesis; also processes lipids, cholesterol, bile, urea, and toxins
Adipose tissue: stores lipids under insulin and releases them under epinephrine
Skeletal muscle
- resting: conserves carbohydrates in glycogen stores and uses free fatty acids in the bloodstream
- active: may use anaerobic, oxidative phosphorylation, direct phosphorylation from creatine, or FA oxidation
cardiac muscle: fatty acid oxidation
brain: glucose, except fasts = ketone bodies
104
What is the respiratory quotient (RQ) ?
RQ = CO2 produced / O2 consumed
for carbs: 1
for lipids: 0.7
in humans = 0.8
105
What are the three hormones that control hunger and satiety?
Ghrelin: secreted by stomach in response to signals of impending meal, increasing appetite
Orexin: further increases appetite
Leptin: hormone secreted by fat cells that decreases appetite
106
What is the formula for BMI?
BMI = mass/ height ^2
