Bioenergetics Flashcards

Question

How is ATP formed?

Answer 1

1 adenosine + 3 phosphate groups Adenosine is a nucleoside (adenine, a nitrogenous base, and a 5-carbon sugar ribose) Bonds b/t the phosphates = phosphoanhydride bonds (high energy) Formed from substrate-level phosphorylation & oxidative phosphorylation; ∼30 kJ/mol of energy

Answer 2

FAD is the (oxidized/form and (accepts) electrons in glycolysis

Answer 3

Flavoproteins are electron carriers in oxidation-reduction reactions = FAD, FMN

Answer 4

electron carrier (FADH₂ = reduced form) that is oxidized @ the 2ⁿᵈ complex in the ETC

Answer 5

an oxidizing agent in the TCA

Answer 6

a cofactor for the ETC's Complex I enzymatic activity.

Answer 7

Cn(H₂O)n

Answer 8

Cn(H₂O)m

Answer 9

◦ Aka- the absolute configuration for a carbohydrate is assigned based on the last chiral carbon in the chain as compared to the configurations of glyceraldehyde; L and D are based on the chiral carbon furthest from the carbonyl group. ◦ Those with the highest-#d chiral carbon with the OH group on the right in a Fischer projection = D sugars (naturally occurring) ◦ OH group on left = L sugars

Answer 10

enantiomers

Answer 11

◦ D/L = absolute configuration, assigned based on the chirality of the carbon atom furthest from the carbonyl group ◦ every chiral center in D-glucose has the opposite configuration of L-glucose

Answer 12

‣ The α form = anomeric carbon is in the axial position (OH below the plane) ‣ The β form = anomeric carbon is in the equatorial position (OH above the plane)

Answer 13

nonsuperimposable configurations of molecules w/ similar connectivity; differs at least one but not all chiral carbons

Answer 14

different configuration @ exactly 1 chiral carbon

Answer 15

subtype of epimers that differ at the chiral, anomeric carbon

Answer 16

carbohydrates that contain an aldehyde group as their most oxidized functional group

Answer 17

has a ketone as their most oxidized functional group

Answer 18

6-membered hexagonal shaped

Answer 19

5-membered pentagonal shaped

Answer 20

◦ At least a 3-carbon backbone ◦ An aldehyde or a ketone group ◦ At least 2 hydroxyl groups

Answer 21

glyceraldehyde & dihyrdroxyacetone

Answer 22

Fructose forms furanose when carbon 5 attacks the carbonyl carbon

Answer 23

Glucose forms pyranose when carbon 5 attacks the carbonyl carbon

Answer 24

• Down right • Up left • As you fill in the substituents, those on the right side of the Fischer diagram will point down, and those on the left side will point up. -OH group on the anomeric carbon (Fischer carbonyl) can be either UP (β) or down (α) • The CH₂OH group on absolute configuration carbon (C-5) points UP for D and down for L. • In planar conformation, everything = eclipsed • In chair conformation, everything = staggered • Everything in between = partially eclipsed

Answer 25

an acetal linkage that chains together monomers to form disaccharides, oligosaccharides, and polysaccharides; also terms the linkage b/t sugar and base in nucleotides

Answer 26

simple sugars; formula (CH₂O)n; typically have 3-7 C. * Position of the carbonyl group (C=O) can be used to categorize the sugars (aldose vs ketone) * They are named according to their # of carbons (trioses = 3 C; pentoses = 5 C; hexoses = 6 C)

Answer 27

glucose (aldohexose); main fuel source for the organism

Answer 28

Fructose (ketohexose); commonly used as sweetener; produced by many plants/fruits

Answer 29

Galactose (aldohexose); found in dairy products & sugar beets; can be rapidly converted to glucose

Answer 30

Mannose (aldohexose)

Answer 31

Sugars that can be oxidized = reducing agents; can be detected by reacting w/ Tollens' or Benedict's reagents

Answer 32

Sugars + COOH and COOH derivatives → esters

Answer 33

Phosphorylation- phosphate phosphate group from ATP + Sugar = phosphate ester

Answer 34

Glycoside formation: basis for building complex carbs; requires the anomeric carbon to link to another sugar

Answer 35

formed when two monosaccharides join together via a dehydration rxn (aka condensation rxn or dehydration synthesis). Here, the hydroxyl group of one monosaccharide combines with the H of another, releasing a molecule of water and forming a covalent bond = glycosidic linkage

Answer 36

Sucrose: made from α-glucose and β-fructose joined @ the hydroxyl groups on the anomeric carbons (creating acetals); glycosidic bond is formed b/t C1 of the α-anomer of glucose & C2 of the β-anomer of fructose; Glu(α1→β2)Fru

Answer 37

Lactose: requires lactase to be hydrolyzed; made from β-galactose and α/β-glucose joined by a 1,4-linkage; Gal(β1→4)Glu

Answer 38

Maltose: two glucose molecules; produced when amylase breaks down starch; Glu(α1→4)Glu

Answer 39

long chains of monosaccharides linked by glycosidic bonds

Answer 40

main energy storage form for plants; made of glucose molecules joined by α-1,4-linkages

Answer 41

linear polymer of glucose; connected by α-1,4-glycosidic bonds; 20%-30% of starch

Answer 42

made of α-1,4-glycosidic bonds and α-1,6-glycosidic branches every 24-30 units; 70%-80% of starch

Answer 43

main energy storage form for animals; has α-1,4-glycosidic bonds and α-1,6-glycosidic bonds ◦ Humans store glycogen in: ‣ Liver- hepatocytes; regulates BGL and provides cells w/ energy ‣ Muscle- can be broken down to power glycolysis ◦ More heavily branched than amylopectin; branching occurs every 8-12 units

Answer 44

main structural component for plant cell walls; main source of fiber for humans; made of repeating β-1,4glycosidic bonds

Answer 45

major component of bacterial cell walls; polymer of carbohydrates that have been modified w/ amino acids

Answer 46

made of N-acetylglucosamine; connected by β-1,4-glycosidic bonds; major component of cell walls in the exoskeletons of crustaceans, insects, and fungi

Answer 47

Glycolysis converts glucose (6-C) to 2 molecules of pyruvate (3-C each). Takes place in the cytosol. Key enzymes: hexokinase, phosphofructokinase, pyruvate kinase. 2 NADH made for every glucose

Answer 48

* Aerobic decarboxylation occurs in the mitochondrial matrix. Converts pyruvate (3-C) to an acetyl group (2-C). (Pyruvate decarboxylation / pyruvate oxidation) * Key enzyme: pyruvate dehydrogenase * 1 NADH made for every pyruvate * Only occurs in the presence of oxygen * Acetyl group attaches to Coenzyme A to make acetyl CoA

Answer 49

oxygen absent Mammalian cells: Lactate dehydrogenase oxidizes NADH → NAD⁺ which replenishes the oxidized coenzyme for glyceraldehyde-3-phosphate dehydrogenase. Lactic acid fermentation: Pyruvate [reduction] → lactate Alcohol fermentation: Pyruvate [reduction] → ethanol

Answer 50

Gluconeogenesis: 2 molecules of pyruvate (noncarbohydrate source) → glucose Mitochondria: pyruvate carboxylase converts pyruvate → oxaloacetate by adding a COO- group. Oxaloacetate is briefly converted to malate for transport out of the mitochondria where it is then converted immediately back to oxaloacetate. In the cytosol, PEP carboxykinase converts oxaloacetate to PEP.

Answer 51

Glycolysis step 10: PEP → enolpyruvate (tautomerize) → pyruvate ‣ Goal: bypass pyruvate kinase ‣ Pyruvate carboxylase converts pyruvate → oxaloacetate → phosphoenolpyruvate ‣ Acetyl-CoA from β-oxidation activates pyruvate carboxylase ‣ Glucagon & cortisol activate PEPCK Glycolysis step 3: (F6P + ATP → F1,6BP) ‣ Frutose 1,6-bisphosphate → (catalysis of the hydrolysis of C1 phosphate group of F1,6BP) → fructose-6-phosphate = isomerized → glucose 6-phosphate (G6P) ‣ Rate limiting step of gluconeognesis ‣ Activated by ATP (directly) & glucagon (indirectly from ↓ levels of fructose-2,6-bisphosphate) ‣ Inhibited by AMP (directly) & insulin (indirectly from ↑ levels of F2,6BP) Glycolysis step 1: (Glucose + ATP → G6P) ‣ Goal: bypass glukokinase ‣ Glucose 6-phosphate → → free glucose

Answer 52

◦ Glycerol 3-phosphate (from triacylglycerols) ◦ Lactate (from anaerobic glycolysis) ◦ Glucogenic amino acids (from muscle proteins)

Answer 53

◦ Lactate → → pyruvate ◦ Alanine → → pyruvate ◦ Glycerol 3-phosphate → → DHAP

Answer 54

Pyruvate carboxylase: pyruvate → oxaloacetate Phosphoenolpyruvate carboxykinase (PEPCK): oxaloacetate → phosphoenolpyruvate Fructose 1,6-bisphosphatase: Fructose 1,6-bisphosphate → fructose 6-phosphate Glucose 6-phosphatase: glucose 6-phosphate → free glucose

Answer 55

Hexokinase; 1: glucose & glucose 6-phosphate Phosphofructokinase; 3: fructose 6-phosphate & fructose 1,6-bisphosphate Phosphofructokinase; 10: phosphoenolpyruvate & pyruvate

Answer 56

Glycolysis 1. What happens: the partial oxidation/breakdown of glucose → 2 pyruvate through 10 enzyme-mediated rxns 2. Location: occcurs in the cytosol or cytoplasm and is common for both aerobic and anaerobic respiration 3. Triggers: High BGL; insulin 4. Initial materials: Glucose 5. Final products: Pyruvate, ATP & NADH 6. Importance: Energy production

Answer 57

Glycogenesis 1. What happens: formation fo glycogen from excess glucose by liver cell sw/ the help of insulin; excess glucose = controlled by insulin 2. Location: cytosol/cytoplasm 3. Triggers: postprandial/well-fed state 4. Initial materials: Glucose & ATP 5. Final products: (glucose)n+1, ADP, Pi 6. Importance: creates glycogen from glucose, storing the excess energy for future use

Answer 58

Glycogenolysis 1. What happens: conversion/breakdown of glycogen to release glucose by liver cells w/ the help of glucagon; deficient glucose = glucagon 2. Location: cytosol/cytoplasm 3. Triggers: fasting or b/t meals 4. Initial materials: glycogen 5. Final products: glycogenin-1 residues & glucose-1-phosphate 6. Importance: energy production & BGL maintenance

Answer 59

Gluconeogenesis 1. What happens: formation of glucose (or glycogen) fro noncarbohydrate sources (amino acids, fatty acids, glycerol) 2. Location: takes place in the liver, kidneys, and striated muscles 3. Triggers: low BGL, glucagon 4. Initial materials: pyruvate 5. Final products: glucose 6. Importance: allows other sources (noncarbhydrates) to be converted into glucose

Answer 60

the pentose phosphate pathway (PPP), AKA hexose monophosphate shunt, HMP; it's 1 of the 3 main ways the body creates molecules w/ reducing power; accounting for ∼60% of NADPH production; occurs in the cytoplasm/cytosol; ratelimiting enzyme = glucose-6-phosphate dehydrogenase (activated by NADP⁺ & insulin; inhibited by NADPH) Primarily anabolic role, using the energy stored in NADPH to synthesize large complex molecules from small precursor ones

Answer 61

Allosteric regulation of glycogenesis & glycogenolysis is done through the regulation of glycogen synthase & glycogen phosphorylase.

Answer 62

Hormonal regulation of glycogenesis & glycogenolysis is done by insulin and glucagon

Answer 63

Rate-limiting enzyme = glycogen synthase. This forms the α-1,4-glycosidic bonds found on the linear glucose chains

Answer 64

It is stimualted by glucose-6-phosphate & insulin and inhibited by epinephrine & glucagon through a protein kinase cascade

Answer 65

Branching enzyme = introduces the α-1,6-linked branches; hydrolyzes one of the α-1,4 bonds, releasing a block of oligoglucose which is then moved and added to a slightly different location

Answer 66

Glycogen synthase makes a linear α-1,4-linked polyglucose chain

Answer 67

Glycogenolysis = the catabolism of glycogen (glycogen break down); is induced by adrenaline

Answer 68

Enzyme: Glucokinase Action: converts glucose --\> glucose 6-phosphate Activated by: present in the pancreatic β-islet cells; is responsive to inuslin in liver

Answer 69

Enzyme: Hexokinase Action: converts glucose --\> glucose 6-phosphate in peripheral tissues Activated by: insulin Inhibited by: G6P (feedback inhibition) Glucagon

Answer 70

Enzyme: Phosphofructokinase-1 (PFK-1) Action: phosphorylates fructose 6-phosphate --\> fructose 1,6-bisphosphate (rate-limiting step of glycolysis) Activated by: (3) 1. AMP (indicates that energy is required -\> glycolysis is activated) 2. Fructose 2,6-bisphosphate 3. Insulin (postprandial state); indirect stimulation by increasing these levels Inhibited by: (4) 1. ATP (energy is plentiful -\> slows glycolysis) 2. citrate (indicates plentiful supply of intermediates for producing energy) 3. low pH 4. In the liver only = glucagon = indirectly inhibits glycolysis by decreasing levels of fructose 2,6-bisphosphate during a fasting state

Answer 71

Enzyme: Phosphofructokinase-2 (PFK-2) Action: makes F2,6-BP Activated by: insulin

Answer 72

Enzyme: Glyceraldehyde-3-phosphate dehydrogenase Action: makes NADH which can feed into the ETC

Answer 73

Enzyme: 3-phosphoglycerate kinase Action: substrate-level phosphorylation, putting Pi onto ADP -\> ATP

Answer 74

Enzyme: Pyruvate kinase Action: substrate-level phosphorylation, putting Pi onto ADP -\> ATP converts PEP -\> pyruvate Activated by: Fructose 1,6-bisphosphate (feed-forward stimulation) Inhibited by: ATP; alanine

Answer 75

Enzyme: Pyruvate dehydrogenase Action: complex of enzymes that converts pyruvate -\> acetyl CoA Activated by: Insulin Inhibited by: acetyl-CoA

Answer 76

Enzyme: Glycogen synthase Action: creates α-1,4 glycosidic links b/t glucose molecules Activated by: insulin

Answer 77

Enzyme: Branching enzyme Action: moves a block of oligoglucose from one chain and adds it to the growing glycogen as a new branch using an α-1,6 glycosidic link

Answer 78

Enzyme: Glycogen phosphorylase Action: removse a single glucose 1-phosphate molecule by breaking α-1,4 glycosidic links Activated by: 1. liver- glucagon to prevent low blood sugar 2. skeletal muscle-- epinephrine & AMP to glucose for the muscle

Answer 79

Enzyme: Debranching enzyme Action: moves a block of oligoglucose from one branch and connects it to the chain using an α-1,4-glycosidic link and removes the branchpoint

Answer 80

Aerobic decarboxylation occurs in mitochondrial matrix Converts pyruvate to an acetyl group key enzyme is pyruvate dehydrogenase

Answer 81

Mammalian cells: lactate dehydrogenase oxidizes NADH to NAD+ which replenishes the oxidized coenzyme for glyceraldehyde-3 phosphate dehydrogenase.

Answer 82

Lactic acid fermentation: pyruvate [reduction] --\> lactate

Answer 83

Alcohol fermentation: Pyruvate [reduction] --\> ethanol

Answer 84

1. A carboxyl group is removed from pyruvate; CO₂ molecule is released; leaves behind a 2-C molecule 2. The 2C molecule is oxidized, and the e⊖ are accepted by NAD+ reducing it → NADH 3. The oxidized 2C molecule is now an acetyl group attached to Coenzyme A (organic molecule derived from vitamin B5) and this forms acetyl-CoA.

Answer 85

Acetyl-CoA can be produced in the following ways • Glycolysis ◦ Pyruvate is transformed into acetyl-CoA in the mitochondria. Pyruvate dehydrogenase makes pyruvate lose a carbon, producing a new 2C molecule called acetyl-CoA. The carbon that's removed takes two O from private with it, exits the body as CO₂ • Aerobic decarboxylation ◦ Done in the mitochondrial matrix; converts pyruvate (3C) → an acetyl group (2C) ◦ 1 NADH for every pyruvate; requires oxygen; acetyl group attaches to Coenzyme-A → acetyl-CoA • Fat metabolism ◦ In β-oxidation, fatty-CoA is broken down, 2C at a time, to make acetyl-CoA which feeds into the TCA ◦ β-oxidation also produces FADH₂ & NADH. These feed into the ETC • Protein metabolism ◦ The catabolism of some amino acids (phenylalanine, tyrosine, leucine, lysine, and tryptophan) can make acetyl-CoA

Answer 86

Large influx of glucose, stimulates insulin, promotes glycolysis.

Answer 87

Large influx of oxaloacetate, stimulates glucagon, promotes gluconeogenesis.

Answer 88

F1,6BP is regulated by the activation of citrate (↑ citrate = ↑ enzyme activity) & inhibited from ↑ AMP or ↓ ATP

Answer 89

In total for one round of the cycle (aka 1 pyruvate molecule) ◦ 1 GTP ◦ 3 NADH ◦ 1 FADH₂ ◦ 2 CO₂ ◦ 1 regenerated oxaloacetate molecule

Answer 90

• Step 1— Citrate Formation ◦ Acetyl-CoA & oxaloacetate [condensation rxn] → citric-CoA ◦ The hydrolysis of citric-CoA → citrate & CoA-SH ; catalyzed by citrate synthase ‣ Synthases = enzymes that form new covalent bonds w/o needing significant energy • Step 2 — Citrate Isomerized → Isocitrate ◦ Achiral citrate → isomerized: 1 of 4 possible isomers of isocitrate ‣ 1: citrate binds @ 3 points to the enzyme aconitase ‣ 2: water is lost from citrate → cis-aconitate ‣ 3: water is added back to form isocitrate ◦ Enzyme is a metalloprotein, requires Fe²⁺ ◦ Results in a switching of a H and a hydroxyl group • Step 3—α-Ketoglutarate and CO₂ Formation: ◦ Isocitrate: oxidized → oxalosuccinate by isocitrate dehydrogenase (the rate-limiting enzyme of the CAC); the first of the 2 carbons from the cycle is lost here; this is also the first NADH produced from intermediates in the cycle ◦ Oxalosuccinate: decarboxylated → α-ketoglutarate & CO₂ • Step 4—Succinyl-CoA and CO₂ Formation ◦ These rxns are carried out by the α-ketoglutarate dehydrogenase complex; formation of succinyl-CoA, α-ketoglutarate & CoA = 1 CO₂ ◦ The CO₂ represents the 2ⁿᵈ and last carbon lost form the cycle; NAD⁺: reduced → NADPH ‣ Dehydrogenases are a subtype of oxidoreductases (enzymes that catalyze an oxidation–reduction reaction). ‣ Dehydrogenases transfer a hydride ion (H − ) to an electron acceptor, usually NAD + or FAD. Therefore, whenever you see dehydrogenase in aerobic metabolism, be on the lookout for a high-energy electron carrier being formed! • Step 5—Succinate Formation ◦ Hydrolysis—thioester bond on succiny-CoA → succinate & CoA-SH & is coupled to the phosphorylation of GDP → GTP ◦ Rxn is catalyzed by succinyl-CoA synthetase ‣ Synthetases: creates new covalent bonds w/ energy input ◦ Phosphorylation of GDP → GTP = driven by the energy released by thioester hydrolysis ◦ GTP is formed: nucleosidediphosphate kinase = catalyzes phosphate transfer GTP → ADP thus producing ATP (this is the only tie in the entire CAC where ATP is produced directly); ATP production is predominantly w/in the ETC ‣ Citrate synthase doesn’t require energy input in order to form covalent bonds, but succinyl-CoA synthetase does. • Step 6—Fumarate Formation: ◦ Occurs in the inner membrane ◦ Succinate: oxidation → fumarate (catalyzed by succinate dehydrogenase = a flavoprotein b/c it is covalently bonded to FAD, the electron acceptor in this rxn) ◦ As succinate is oxidized to fumarate → FAD is reduced to FADH₂ = 1.5 ATP ‣ NADH = 2.5 ATP ◦ FAD = the electron acceptor in this rxn b/c the reducing power of succinate is not great enough to reduce NAD⁺ • Step 7—Malate Formation ◦ Fumarase: catalyzes hydrolysis of the alkene bond in fumarate → malate (only L-malate forms in this rxn) • Step 8—Oxaloacetate Formed Anew ◦ Malate dehydrogenase: catalyzes oxidation: malate → oxaloacetate ◦ 3ʳᵈ and final molecule of NAD⁺: reduced → NADH ◦ Newly formed oxaloacetate is ready to take part in another turn of the CAC; we've gained all of the high-energy electron carriers possible from 1 turn of the cycle

Answer 91

* Fatty acids are amphipathic molecules that have a polar carboxylate-head group and nonpolar hydrocarbon tail. They are longchain carboxylic acids. They are generally considered insoluble in water while longer hydrocarbon chains have a lower solubility. * Main function = energy provision & precursors for the synthesis of other molecules

Answer 92

triglycerides, phospholipids, cholesterol, and eicosanoids

Answer 93

Fatty acid oxidation (β-oxidation) = catabolic breakdown of fatty acids → energy ◦ Can completely degrade saturated fatty acids ◦ Requires the input of the enzymes enoyl-CoA isomerase & 2,4-dienoyl CoA for the complete degradation of unsaturated fatty acids ◦ Occurs in the mitochondrial matrix; converts their fatty acid chains → 2 C units of acetyl groups, producing NADH & FADH₂ which are then used by the ETC.

Answer 94

1. The fatty acid is activated. Coenzyme A is added to the end of a long-chain fatty acid, after which the activated fatty acyl-CoA enters the β-oxidation pathway 2. fatty acyl-CoA (oxidation) → enoyl-CoA A. A trans double bond is introduced into the acyl chain 3. Enoyl-CoA (hydration) → an alcohol 4. Alcohol (oxidation) → carbonyl 5. Carbonyl → cleaves off acetyl-CoA from the oxidized molecule; also yields an acyl-CoA that is 2 C shorter than the original molecule that entered the β-oxidation pathway 6. Cycle repeats until the fatty acid has been completely reduced to acetyl-CoA, which is fed through the citric acid cycle to yield cellular energy in the form of ATP.

Answer 95

Carbohydrates break down into glucose (sugar) which go through glycolysis. Fats break down into fatty acids and glycerol which go through β-oxidation. Proteins break down into amino acids which go through transamination.

Answer 96

Acetyl-CoA (2C; inner mitochondrial matrix) = precursor for fatty acid synthesis. Acetyl-CoA is converted to citrate so that the citrate shuttle can transport it into the cytoplasm, where its broken back up to oxaloacetate & acetyl-CoA. For OAA to return to pyruvate, a C is lost as CO₂ and NADP⁺ is reduced to NADPH

Answer 97

Acetyl-CoAs are linked together → a large fatty acid chain = **Palmitic acid (16C)** = primary product of fatty acid synthesis in the body. Requires ***8 acetyl-CoA*** molecules (since they're 2 C each). **7** ATP molecules are required for this rxn. **14** NADPH are required to reduce the carbonyl group in the acetyl-CoA to just C-C bonds; end up with **7** ADP & Pi & **14** NADP⁺

Answer 98

First enzyme that carries out the activation step in fatty acid synthesis = acetyl-CoA carboxylase which adds a carboxy group to acetyl-CoA. It is the rate-limiting step of the entire fatty acid synthesis pathway, so it's regulated through allosteric and hormonal regulation. Citrate is an allosteric activator; insulin activates this pathway. Long-chain fatty acids can inhibit this enzyme through product inhibition. Glucagon is a hormonal inhibitor--it signals adipose cells to release fatty acids and for our cells to break down.

Answer 99

the enzyme that polymerizes the manlonyl-CoA subunits together.

Answer 100

The actual digestion of proteins begins in the stomach. HCl & pepsin begin the process of breaking down the proteins. As chyme enters the small intestine, it mixes w/ bicarbonate (neutralizes the HCl) & digestive enzymes (breaks down the proteins into smaller polypeptides & AA).

Answer 101

Enteropeptidase = enzyme in the wall of the small intestine; activates trypsin which then activates chymotrypsin.

Answer 102

Substrates: 1. NADH (reduced form) 2. FADH₂ (reduced form) 3. O₂ 4. ADP 5. Pi Products: 1. ATP 2. NAD+ (oxidized form) 3. FAD (oxidized form) 4. H2O

Answer 103

The final stage in cellular respiration is oxidative phosphorylation which is made up of two interdependent processes: flow of e⊖ through the ETC down to oxygen & chemiosmotic coupling.

Answer 104

E⊖ are transferred from NADH → DHAP making glycerol-3-phosphate. These e⊖ can then be transferred to mitochondrial FAD making FADH₂

Answer 105

E⊖ are transferred from NADH → oxaloacetate making malate which can then cross the inner mitochondrial membrane and transfer the e⊖ to mitochondrial NAD⁺ making NADH.

Answer 106

NADH-CoQ oxidoreductase & NADH dehydrogenase; 4 protons are transferred from the mitochondrial matrix -\> intermembrane space converts NADH -\> NAD+ Overal rxn: NADH + H⁺ + Q -\> NAD⁺+ QH₂ NADH transfers its e⊖ to CI. The part of complex I that receives the e⊖ = a flavoprotein (a protein w/ an FMN molecule attached). FMN is a prosthetic group (a non-protein molecule tightly bound to a protein and required for its activity). It's the FMN that actually accepts e⊖ from NADH. FMN passes the e⊖ to the Fe-S protein (another protein inside complex I ) which in turn transfers the e⊖ to ubiquinone (Q).

Answer 107

Succinate-CoQ oxidoreductase Succinate dehydrogenase No proton pumping specifically deals w/ FAD/FADH₂ Succinate dehydrogenase = a membrane-bound enzyme that catalyzes the conversion of succinate -\> fumarate in the TCA, generating FADH₂ which delivers more e- to Q -\> QH₂ FADH₂ deposits its electrons in the ETC via CII. The enzyme that reduces FADH₂ in the TCA & FADH₂ are embedded in the inner mitochondrial membrane. FADH₂ transfers its e⊖ to the iron-sulfur proteins w/in CII, which then passes the e⊖ to ubiquinone (Q); same as in CI.

Answer 108

CoQH₂ cytochrome c oxidoreductase e- are passed from QH₂ -\> cytochrome c, regenerating Q, resulting in teh reduced form of cytochrome c, Q carries 2 e-, cytochrome c carries 1 4 protons are translocated into teh intermembrane space per molecule of QH₂ As e⊖ move through complex III, more H ions are pumped across the membrane, and the e⊖ are ultimately delivered to cytochrome C (cyt C) which carries the e⊖ to complex IV (CIV) where a final batch of H ions is pumped across the membrane. CIV passes the e⊖ to O₂ which splits into 2 oxygen atoms & accepts protons from the matrix to form water. 4 e⊖ are required to reduce each molecule of O₂, and 2 H₂O molecules are formed. Complex III (CIII): has both the Fe-S protein as well as cytochromes (family of related proteins that have heme prosthetic groups w/ iron ions). In CIII, e⊖ are passed from one cytochrome to the Fe-S protein to a 2ⁿᵈ cytochrome, and then finally transferred out of the complex to cytochrome C (e⊖ carrier). CIII also pumps protons from the matrix → intermembrane space

Answer 109

Cytochrome C oxidase 2 protons are translocated Cytochrome C delivers the e⊖ to the last complex in the ETC, CIV. Here, the e⊖ are passed through 2 more cytochromes, and the 2ⁿᵈ cytochrome, w/ the help of a copper ion, transfers the e⊖ to O₂, splitting oxygen to form 2 H₂O molecules. The protons used to form H₂O come from the matrix, contributing to the H ion gradient, and CIV also pumps protons from the matrix to the intermembrane space.

Answer 110

In eukaryotes, ETC is in the **inner mitochondrial membrane** while in prokaryotes it's in the **plasma membrane**.

Answer 111

a non-protein molecule tightly bound to a protein and required for its activity

Answer 112

Oxidized form of Q is **ubiquinone** while the reduced form is ubiquinol (QH₂)

Answer 113

You get 2.5 ATP from NADH and 1.5 ATP from FADH₂.

Answer 114

◦ NADH is a very good e⊖ donor (its e⊖ are at a high energy level) ◦ NADPH is primarily produced in the oxidative part of the pentose phosphate pathway and is used in anabolic synthesis to make cholesterol, fatty acids, transmitter substances & nucleotides ◦ NADH & NADPH are both reductive agents

Answer 115

proteins that have both a nucleic acid derivative of riboflavin (flavin adenine dinucleotide / flavin mono nucleotide) Located on the matrix face of the inner mitochondrial membrane; functions as a specific e⊖ acceptor for 1˚ dehydrogenase, transferring the e⊖ to the ubiquinone pool in the inner mitochondrial matrix

Answer 116

◦ Compounds made of heme bound to a protein ◦ Functions as e⊖ transfer agents ◦ Cytochrome c transfers e⊖ from CIII → CIV in the ETC; can only carry 1 e⊖ at a time

Answer 117

the process that links the ETC (which creates an electrochemical gradient across the inner mitochondrial membrane) to the production of ATP through ATP synthase. Chemiosmotic coupling allows the chemical energy from the gradient to be harnessed to phosphorylate ADP → ATP (endergonic)

Answer 118

the relationship b/t the proton gradient and ATP synthesis is indirect; ATP is released by the synthase as a result of a conformational change caused by the gradient. The F₁ portion of ATP synthase harnesses the gradient energy for chemical bonding from the spinning that occurs when protons go through it. * The F₀ portion is the portion of ATP synthase that spans the membrane. It functions as an ion channel, so protons travel through it along their gradient back into the matrix. * The F₁ portion utilizes the energy released from the electrochemical gradient to phosphorylate ADP → ATP. * When the proton-motive force is dissipated through the F₀ portion, (free energy change of the rxn) ∆G˚' = -220 kj/mol (highly exergonic)

Answer 119

Pyruvate dehydrogenase complex converts pyruvate → acetyl-CoA and this is upregulated by high levels of AMP, CoA, and NAD⁺ (signs that the cell needs to make more energy).

Answer 120

◦ 1) formation of citrate ‣ Upregulated: high levels of ADP ‣ Downregulated: ATP, NADH, [citrate, and succinyl-CoA = negative feedback] ◦ 2) Conversion of isocitrate → α-ketoglutarate ‣ Upregulated: ADP ‣ Downregulated: ATP ◦ 3) α-ketoglutarate → succinyl-CoA ‣ Upregulated: Ca²⁺ ‣ Downregulated: NADH & [succinyl-CoA = negative feedback]

Answer 121

Mitochondria play a significant role in initiating apoptosis: ◦ 1st steps = ↑ permeability of the outer mitochondrial membrane. ‣ Regulated by proteins in the BCL-2 family (which includes both pro-apoptotic proteins and anti-apoptotic proteins) ◦ When the mitochondrial membrane becomes more permeable, cytochrome C (the shuttle b/t CIII & CIV of the ETC) is released from the intermembrane space → cytoplasm ◦ Once in the cytoplasm, cyt c activates the caspases (enzymes that act as proteases to initiate large-scale protein degradation) and the nucleases to degrade DNA ◦ Together, the above processes result in regulated cell breakdown; from there the components can be phagocytosed and reused

Answer 122

hormones are signals produced in the endocrine system & released into bodily fluids to be transferred to the target cells ## Footnote 3 classes of hormones (which are based on their chemical structure): ◦ Steroids ◦ Amines (amino acid-derived) ◦ Peptide hormones (includes peptides & proteins)

Answer 123

Steroid hormones are lipid-derived so they are lipid soluble and water insoluble * They remain in circulation longer * They have high-affinity receptors, work @ low concentrations, and affects gene expression & metabolism. * These hormones and some of the amines can diffuse through the cell membrane with ease, but once they do so, they need transport proteins to get to their target cells * Target cell receptors for lipid-soluble hormones = cytoplasm or nucleus * When the lipid-soluble hormone forms a complex w/ its receptor, they bind together the DNA and induce the expression of certain genes. So the action of steroid hormones is slower b/c they need to promote the translation & transcription of these mRNA @ the target gene

Answer 124

* Includes insulin, growth hormone, and MOST of the amines (like epinephrine) * They are water-soluble molecules (so they can't pass through the cell membrane) so their receptors are on the surface of the target cells. * These hormones are secreted by exocytosis and travel to the destination via the blood * When the water-soluble hormone binds to its target receptor, this induces a cell-signaling pathway that either (1) causes a prompt cellular response, or (2) induces changes in the expression of certain genes * IE— When epinephrine (adrenaline) binds to its receptor, this activates a cytoplasmic enzyme that inhibits glycogen synthesis. * Since peptide hormones must bind to the membrane receptors, they rely on cascades of kinases to transmit their message to the target cell, having a faster effect.

Answer 125

Glycogenesis

Answer 126

Glycogenolysis

Answer 127

Gluconeogenesis

Answer 128

Ketogenesis

Answer 129

β-oxidation

Answer 130

Pentose phosphate pathway (PPP)

Answer 131

Glucose is transported to the liver; can be stored as glycogen or converted to triglycerides; glucose must be converted into glycerol & fatty acids; triglycerides are mostly stored in adipose tissues and can't be transported in the blood, so they have to be converted into VLDL which can be exported from the liver into blood. the liver breaks down AA -\> keto acids. These α-keto acids give off ammonia when it's excreted as waste (urea) if the liver needs energy during the absorptive state, the keto acids can be broken down -\> acetyl-CoA which then goes through TCA & ETC to produce ATP After a meal, [glucose] in the portal blood is ↑. The liver extracts excess glucose and uses it to replenish the glycogen stores. Remaining glucose is then converted to acetyl-CoA for fatty acid synthesis. This ↑ in insulin s/p a meal stimulates both glycogen synthesis & fatty acid synthesis in the liver. Fatty acids → triacylglycerols & released into the blood as VLDL • Well fed state: liver derives most of its energy from oxidizing excess AA

Answer 132

glucose needs to be converted into triglycerides. The VLDL from the liver will be turned into fatty acids which are then combined w/ glycerol to form triglycerides. ## Footnote * After a meal, the ↑ insulin levels stimulate glucose uptake by adipose tissue. Insulin triggers fatty acid release from VLDL and chylomicrons. * Lipoprotein lipase = enzyme found in the capillary bed of adipose tissue; induced by insulin * The fatty acids released from lipoproteins are taken up by adipose tissue and re-esterified to triacylglycerols (storage) * Insulin can suppress the release of fatty acids from adipose tissue

Answer 133

Glucose can be taken up & has 2 pathways: - can convert to glycogen (storage form) - can convert to pyruvate (if energy is needed) - muscle can take up AA from proteins and store them as proteins in the muscle * Major fuels = glucose & fatty acids * S/p a meal, insulin promotes glucose uptake, replenishing glycogen stores & AA used for protein synthesis. Excess glucose & AA can be oxidized for energy.

Answer 134

glucose from blood -\> pyruvate makes ATP so brain can work

Answer 135

Glycogen is broken down to glucose which can then be exported out of the liver into the blood. AA are taken up by the liver & converted -\> keto acids and can be used to make glucose, broken down to acetyl-CoA Triglycerides -\> glucose Fatty acids = 2nd rxn so they can be broken down -\> ketones; can be used in the brain * In the fasting state: the liver releases glucose into the blood and this ↑ promotes glycogen degradation & gluconeogenesis. * Lactate (from anaerobic metabolism), glycerol (from triacylglycerols), and AA = provide the carbon skeletons for glucose synthesis

Answer 136

triglycerides broken down -\> glycerol & fatty acids; can be exported into the blood and brought to the liver to make glucose • Fasting state: ↓ insulin & ↑ epinephrine = activates hormone-sensitive lipase in fat cells, allowing fatty acids to be released into circulation

Answer 137

Protein -\> AA -\> liver to be converted to α-keto acids -\> glucose Glycogen -\> glucose -\> pyruvate -\> acetyl coA & produce energy for the muscles. If muscles low on O2, glucose can produce lactate * Fasting state: resting muscle uses fatty acids derived from free fatty acids; ketone bodies may be used in prolonged fasting state (Active Muscle) * Fuel depends on magnitude & duration of exercise; ◦ Short-lived source of energy (2-7 s) comes from creatine phosphate (transfers a phosphate group to ADP → ATP) * Skeletal muscle has glycogen stores (and some triacylglycerol stores) so both blood glucose & free fatty acids may be used * Short bursts, high intensity exercise = anaerobic glycolysis * Moderately high-intensity, continuous = oxidation of glucose & fatty acids * S/P 1-3 hours of continuous exercise = oxidation of fatty acids

Answer 138

brain takes glucose from the blood -\> pyruvate; goes thorugh cellular respiration to produce ATP ketones from liver can be used by the brain

Answer 139

↑ BGL = insulin is released → promotes glycolysis, glycogen synthesis (liver & skeletal muscles); fatty acid synthesis (liver), and fatty acid storage (adipose tissue).

Answer 140

Epinephrine triggers glycogen breakdown; cortisol promotes gluconeogenesis & ↑ BGL

Answer 141

Insulin = released by the β cells of the pancreas; stimulates glucose uptake by target cells; is released upon the entry of glucose into pancreatic β cells through the GLUT2 glucose transporters.

Answer 142

When glucose enters the Krebs cycle in the β cells, the ΑΤP:ADP ratio ↑ → closing the ATP-sensitive potassium channel → buildup of intracellular potassium ions → depolarization & opening of voltage-gated calcium channels w/in the membrane of β cells. Entry of Ca²⁺ ions triggers a signaling cascade → release of additional calcium ions from the ER. This ↑ in the intracellular [Ca²⁺] → a release of previously stored insulin from secretory vesicles

Answer 143

Other substances stimulating insulin release = AA arginine, leucine; parasympathetic release of acetylcholine; cholecystokinin (CKK); glumoagon-like peptide-1 (GLP-1) & glucose-dependent insulinotropic peptide (GIP)

Answer 144

In insulin responsive tissues (like skeletal muscle & fat cells) insulin binds w/ insulin receptors → triggers an intracellular signaling cascade, promoting more GLUT4 receptors coming in; presence of more GLUT4 in the plasma membrane promotes the uptake of glucose into the target cells → reduces BGL

Answer 145

↑ the concentrations of circulating insulin ↓ proteolysis (protein breakdown) & ↑ AA uptake

Answer 146

* Glucagon = synthesized by α-cells of the pancreas; compensatory ↑ in BGL by causing the liver to convert stored glycogen → glucose which is then released into the bloodstream. Glucagon antagonizes insulin's action on BGL (aka glucagon and insulin forms a feedback system that ensures blood glucose homeostasis if properly regulated) * Glucagon promotes lipolysis (breakdown of triglycerides) by activating protein kinase A → activates hormone-sensitive lipase → releases free fatty acids & glycerol into the bloodstream. Glycerol can enter the TCA (s/p conversion to glycerol 3-phosphate by glycerol kinase) in the liver & kidneys

Answer 147

Pancreatic β-cells secrete insulin (high glucose) while Pancreatic α-cells secrete glucagon (low glucose, high AA levels)

Answer 148

promotes glycogenolysis & ↑ basal metabolic rate through sympathetic nervous system activity

Answer 149

Ones that ↓ food intake & ↑ energy expenditure = insulin & leptin. ## Footnote ‣ Insulin stimulates the production of leptin by adipose tissue, ↓ appetite & gives satiety feeling ‣ Leptin ↓ insulin secretion & ↑ tissue sensitivity to insulin → glucose uptake for energy utilization/storage. • It lives in the adipose tissue and goes to the hypothalamus ‣ Insulin resistance = when he body doesn't use the stored fat as an energy source ‣ Leptin resistance = dysfunction in the feeling of satiety ◦ Other hormones that act on the satiety center in the brain: ‣ Ghrelin: secreted by the stomach wall; ↑ feelings of hunger ‣ Peptide YY (PYY): secreted by the small intestine; acts on brain receptors to ↓ appetite

Answer 150

further ↑ appetite; also involved in alertness & the sleep-wake cycle; triggered by hypoglycemia

Bioenergetics Flashcards

(181 cards)