Exam #2 Flashcards

Question

Dietary Fiber - Cellulose

Answer 1

homopolysaccharide (glucose) - rough part of grains and fruit provides structure in the cell walls of plants dietary fiber - bulking agent and energy souce for bacteria considered dietary b/c can't be digested by mammals contains beta-1-4 glycosidic linkage therefore resistant to digestive enzyme alpha-amylase which favors alpha-1-4 linkages

Answer 2

has 4 different atoms or groups attached

Answer 3

OH group is to the right all naturally occurring sugars are D enzymes are specific and will only work on D or L NOT BOTH

Answer 4

OH group of the chiral C is to the left enzymes are specific and will only work on D or L NOT BOTH

Answer 5

The carbon that forms a ring structure with the reducing carbon reacting with OH group on the highest numbered chiral carbon of monosaccharide. the carbon atom comprising the carbonyl function anomeric carbon is the new asymmetric center

Answer 6

**FORM:** when OH group of anomeric carbon is drawn below the plane of ring DOWN Starches - soluble and easily digested **LINKAGE: (disaccharides)** Humans can digest alpha because enzyme is made to support alpha linkage. straight

Answer 7

**FORM**: when OH group is above the plane of the ring UP Fiber (can't digest-only animals and bacteria) Cellulose formed when synthesized from beta-glucose units is INSOLUBLE and cannot be digested as a food source by most animals **LINKAGE: (disaccharides)** zigzag

Answer 8

**Mouth** - _salivary alpha-amylase_ hydrolyzes alpha-1-4 linkages amylose-\>dextrins amylopectin-\>dextrins **Stomach** _no digestion_ pH too low inactivates enzyme **Small intestine** - _pacreatic alpha-amylase_ hydrolyzes alpha-1-4 linkage; bicarbonate in duodenum elevates pH dextrins-\> maltose dextrins-\>maltose and limit dextrins **Brush Border of SI (disaccarides)** amylose - maltose (_maltase_) -\> glucose amylopectin - maltose (_maltase_)-\> glucose limit dextrins (_alpha-dextrinase_) -\> glucose

Answer 9

crystalline starch is insoluble in water and nondigestible when heated becomes digestible but upon cooling reverts back starches can be chemically modified to resist digestion by increasing crosslinking between chains

Answer 10

**Mouth** - _no digestion_ **Stomach** - _no digestion_ **Upper Small Intestine** - microvilli of the intestinal mucosal cells (enterocytes) the brush border enzymes located on enterocytes _lactase, sucrase, maltase, and isomaltase_ lactose (_lactase_ catalyzes clevage) -\>galactose & glucose sucrose (_sucrase_ hydrolyzes) -\> glucose & fructose maltose (_maltase_ hydrolyzes) -\> glucose & glucose Isomaltose (_isomaltase or alpha-dextrinase_ from amylopectin hydrolyzes alpha-1-6 linkage) -\> glucose & glucose

Answer 11

once food is digested nutrients must move into the cells of the GI tract by the process absorption The wall of the small intestine is composed of absorptive mucosal cells that line projections called villi that extend into the lumen. On the villi are absorptive cells (enterocytes) that have microvilli (brush border) **diffusion** - particles move from high to low concentration **facilitated diffusion**-carrier want equalization of substance each side of membrane **active transport**-concentration only on one side. requires ATP and Na+. one directional carriers **pinocytosis**- large molecules cell membrane engulfs

Answer 12

Into **CELL**: _Active_ Transport - SGLT1 (sodium glucose transporter 1) uses ATP to transport sugar through mucosal cell. 1 glucose and 2 Na+ are transported into mucosal cell of the SI at one time. carrier used to cross cell membrane Into **BLOOD**: _Diffusion_ GLUT2 transports glucose from the intestinal mucosal cell (enterocyte) into the portal blood. dependent on blood glucose concentration

Answer 13

Into **CELL**: _facilitated_ transport - GLUT5 fructose transported into the mucosal cell of SI Into **BLOOD**: GLUT2 _factilitated_ transport fructose transported from the mucosal cell of SI absorbed by the liver where it is phosphorylated and trapped (no fructose in blood) limited in 60% of adults fructose absorption is slower than glucose and galactose

Answer 14

going from blood to other tissues

Answer 15

transport across the wall of **intestine** into portal circulation **portal circulation** -\> directly to **liver** (major site of metabolism) through specific hepatocyte receptors enters liver cells by _facilitated transport_ and metabolized converted to glucose derivatives and have same fate as glucose in liver-\> converts to glucose-\> stored as glycogen or catabolized

Answer 16

glucose is highly _polar_ cell (lipid bilayer) membrane is _nonpolar_ matrix the family of integral protein carriers involved in this process are glucose transports (GLUT) glucose enters cell through these proteins that are embedded within cell membrane. **FACILITATED DIFFUSION** these integral proteins (12) have specific combining site these proteins undergo conformational change upon molecule binding which allows the molecule to be **TRANSLOCATED** to the other side of the membrane and released can reverse this conformational change when molecule is unbound so that the process can be repeated

Answer 17

insulin - anabolic hormone involved in glucose synthesis and storage released by Beta-cells of pancreas role in cellular glucose uptake binds to membrane receptor stimulates GLUT4 to move to membrane Maintains blood glucose levels insulin receptor in mucles and liver muscles=use liver=store 1. ) stimulates uptake of glucose by muscle and adipose 2. ) Inhibits the synthesis of glucose (glyconeogenesis) The rise in blood glucose following a CHO meal triggers release of insulin while reducing the secretion of glucagon.

Answer 18

doesn't take glucose into cell insulin - anabolic hormone involved in glucose synthesis and storage insulin -\> receptor -\> 2nd messenger (signal) -\> stimulates uptake of glucose -\> to glycogen to store or insulin binds to it's receptor intracellular domain changes shape which cause chain of reactions that activate certain enzymes. more glucose transporter proteins are released from intracellular stores and move to the plama membrane and become embedded

Answer 19

**insulin** regulated GLUT4 concentration on plasma membrane increases in response to the hormone insulin more membrane transporters = increase in glucose uptake skeletal muscle and adipose tissue are responsive to insulin muscle, heart, brown and white adipocytes

Answer 20

high affinity glucose transporter with expression in those tissues that are highly dependent on glucose Brain

Answer 21

muscles, kidney, and adipose kidney - liver can't filter glucose out not suppose to have C units in urine diabetes= sweet urine kidney damage uptake of glucose by skeletal and adipose tissue are insulin dependent (GLUT4) uptake by liver is insulin independent

Answer 22

the rate glucose is absorbed from intestinal tract is important in controlling the homeostasis of blood glucose, insulin release, obesity, and possible weight loss.

Answer 23

increase in blood glucose level over the base-line level during a 2 hour period following consumption of a defined amount of carbohydrate (usually 50 g) compared with the same amount of CHO in a reference food high glycemic food cause a spike in bld glu levels low glycemic food not as bad of a spike PTN and FAT slow digestion

Answer 24

Glycemic load = glycemic index X g of CHO in a serving High GL = increase bld glu takes into account that we don't just eat single food but meals made up of a number of foods

Answer 25

_glycogenesis_ - making glycogen _glycoenolysis_ - breakdown glycogen _glycolysis_ - oxidation of glucose _gluconeogenesis_ - produce glucose from nonCHO intermediates _hexose monophosphate shunt_ - production of 5C monosaccharides from NADPH _TCA_ - oxidation of pyruvate and acetyl CoA

Answer 26

The pathway by which glycogen is enzymatically broken down to individual glucose units in the form of glucose-1-phosphate hormone regulated 1. glucagon (pancreas) 2. epinephrine (adrenal medulla) both hormones function through the second messenger cAMP which regulates phosphorylation state of enzymes phosphorolysis- glycogen glycosidic bonds are cleaved by adding a phosphate reaction is catalyzed and regulated by glycogen phosphorylase (muscle and liver)

Answer 27

conversion of glucose to **glycogen** (insulin stimulates) important in hepatocytes bc **liver **(maintaining _glucose homeostasis_) is major source of glycogen synthesis and storage other major site of storage is skeletal **muscle** (used for _energy_) and to a lesser extent also adipose tissue

Answer 28

1. **Glycogen Synthesis** - (Glycogenesis) reversible stimulated by high glucose (liver), insulin, low glycogen (muscle) 2. **ATP Synthesis** - produce energy NOT reversible Glycolysis - low energy produced, cytoplasm, anaerobic glucose -\> pyruvate releases ATP _Anaerobic Glycolysis_ = 2 ATP/glucose and maintain blood glucose. pyruvate to lactate RBCs, WBCs, kidney medulla, enterocytes, lens, cornea, skin, and skeletal muscle (rely on glycolysis bc lack mitochondria) _Aerobic Glycolysis_ = 38 ATP/glucose and maintain blood glucose glucose-\>pyruvate-\>acetyl-CoA-\>TCA brain, liver, skeletal muscle, kidney cortex TCA - high energy produced, mitochondria, aerobic upon completion of acetyl-CoA through TCA -\> lots of ATP!! Stimulated: high glucose, low ATP, insulin Inhibition: high ATP, FFAs 3. **FFA Synthesis** - fatty acid production NOT reversible (only occurs if excess calories are consumed) Acetyl-CoA-\>FFA synthesis-\>TG (liver and adipocytes) Stimulated: high glucose, high ATP, and insulin 4. **NEAA Synthesis** - amino acids reversible

Answer 29

glucose degraded into **2 pyruvate** _Anaerobic_ -\> pyruvate to _lactate_ from muscle can then move to the blood stream and be carried to the liver for conversion into glucose. releases only small amount of energy to help sustain muscles _Aerobic_ -\> pyruvate transported to mitochondria goes through TCA completely oxidized to _CO2 and H2O and ATP_ notes: pyruvate-\>acetyl CoA-\>TCA-\>electrons enter ETC=ATP

Answer 30

**Glucose** phosphorylated to **Glucose-6-Phosphate** Enzymes: **glucokinase** (Liver) and **hexokinase** (liver or other tissues) **Rate-limiting step** - 1 ATP consumed irreversible (unless use **G-6-phosphotase** in liver) liver isn't selfish will return glucose back to blood glucokinase and G-6-phosphotase enable the liver to regulate blood glucose levels adding phosphate traps glucose into cell (when BGL are high) _hexokinase_ is inhibited by G6P competes for active site and by allosteric interactions at a separate site on enzyme _glucokinase_ has high km for glucose (prevents too much glucose being removed from blood). only active at high glucose. not inhibited. allows glucose to be stored at glycogen in liver only when blood glucose is high ATP-\> ADP Phosphate added to glucose-6-phosphate

Answer 31

**G6P** isomerized to **Fructose-6-phosphate** Enzyme: **phosphoglucose isomerase** smaller ring but still 6 carbons

Answer 32

**F6P** phosphorylated to **fructose-1,6-bisphosphate** Enzyme: catalyzed by **phosphofructokinase (PFK)** Irreversible - **Rate limiting** allosteric _Inhibitors_: ATP, citrate, certain FA, increase in blood concentration of H ions _Activators_: AMP, ADP, and fructose 2,6-bisphosphate produced from fructose 6-P using enzyme phosphofructose kinase 2 (PFK2) low ATP speeds reaction up ATP -\> ADP phosphate added to fructose-1,6-bisphosphate

Answer 33

**F 1,6 bisP** into **glyceral dehyde-3-phosphate (G3P)** and **dihydroxyacetone (DHAP)** Enzyme: **aldolase** G3P and DHAP are each 3C units

Answer 34

**DHAP** is converts to **G3P** Enzyme: **triosephosphate isomerase** G3P = glyceraldehyde-3-phosphate

Answer 35

**G3P** is oxidized and phosphorylated to **1,3-bisphosphoglycerate** enzyme: **G3-P dehydrogenase** requires _NAD_ and _inorganic P_ produces **NADH** (energy producing) NADH = 3ATP

Answer 36

**1,3-bisphosphoglycerate** to **3-phosphoglycerate** enzyme: **phosphoglycerate kinase** substrate level phosphorylation **2 ATPs** produced from 1 glucose Net ATP=0 ADP -\> ATP phosphate removed from 1,3-bisphosphoglycerate

Answer 37

**3-phosphoglycerate** to **2-phosphoglycerate** Enzyme: **phosphoglycerate mutase** reversible phosphate group transfer from carbon 3 to carbon 2

Answer 38

**2 phosphoglycerate** to **phosphoenolpyruvate + H2O** enzyme: **enolase** Dehydration rxn reversible forms a double bond between the 2nd and 3rd C

Answer 39

**phosphoenolpyruvate (PEP)** to **pyruvate** enzyme: **pyruvate kinase (PK)** transfer of phosphate from phosphoenolpyruvate (PEP) to ADP _substate level phosphorylation_ **IRREVERSIBLE** net yields **2 ATPs** per glucose molecule PK _inhibited_ by ATP and alanine PK _activated_ by Fructose 1,6 bisphosphate PK is regulated by covalent phosphorylation inhibited by phosphorylation ADP -\> ATP phosphate removed from 2nd Carbon

Answer 40

**pyruvate** to **lactate** enzyme: **lactate dehydrogenase** under _anaerobic_ conditions (fermentation) NADH+ and H+ have 2H and electrons removed and given to pyruvate NADH-\>**NAD** NAD formed from this reaction can replace NAD needed in step 6 of glycolysis

Answer 41

3 enzymes catalyze highly spontaneous rxns 1. hexokinase 2. phosphofructokinase (PFK) 3. pyruvate kinase control of these enzymes determines the rate of glycolysis IRREVERSIBLE RXNs

Answer 42

Glucose step 1 use 1 ATP = -1 step 3 use 1 ATP= -2 step 6 gain NADH (3 ATP) per G3P = 2 NADH step 7 gain 2 ATP = 0 step 10 gain 2 ATP per glucose = **2** Pyruvate step 11 (anaerobic) use NADH (-3 ATP) = -2 NADH NAD too big to leave cytosol need shuttle system glucose + 2NAD + 2ADP + 2P -\> 2 pyruvate + **2NADH + 2 ATP**

Answer 43

NADH (hydrogens and electrons) produced by glycolysis cannot enter mitochondria directly in order to be oxidized by ETC 1. Malate - Aspartate shuttle system liver, kidney, and heart 2 NADH from glycolysis = 6 ATPs + 2 ATP from glycolysis = **8 ATPs** 2. G3P shuttle system (dominate) brain and skeletal muscle 2 NADH from glycolysis -\> 2 FADH2 = 4 ATPs + 2 ATP from glycolysis = **6 ATPs**

Answer 44

glycolysis is in cytosol of cell pyruvate goes to mitochondrion to be further metabolized inner membrane of mitochondria permeability barrier matrix contains pyruvate dehydrogenase of TCA

Answer 45

3C -\> 2C + CO2 enzyme: **pyruvate dehydrogenase** (PDH) oxidative decarboxylation of pyruvate produce **NADH** and **CO2** NADH = 3 ATPs **IRREVERSIBLE** - acetyl CoA is also produced from fatty acids (no fatty acid to glucose possible) Important bc ready for TCA and fatty acid synthesis Regulated by Inhibition NADH competes with NAD for E3 binding Acetyl CoA competes with CoA for E2 binding

Answer 46

presence of oxygen pathway for oxidation of amino acids, fatty acids, and carbohydrates 6C goes CO2 -\> 5C goes CO2 -\> 4C 3CO2 , 4NADH , 1 FADH2 , 1 ATP produced 1 NADH produced when pyruvate goes to acetyl CoA

Answer 47

Acetyl CoA (2C) + Oxaloacetate (4C) + H2O -\> Citrate (6C) + CoA enzyme: citrate synthase condensation rxn

Answer 48

Citrate (6C) -\> Isocitrate (6C) enzyme: aconitase isomerization

Answer 49

Isocitrate (6C) + NAD -\> Alpha-ketoglutarate (5C) + **CO2** + **NADH** + H enzyme: isocitrate dehydrogenase oxidatve decarboxylation Allosteric Enzyme inhibited by NADH and ATP activated by ADP too much product then acetyl coa goes to fatty acid synthesis instead and entire pathway shutdown NADH=**3 ATPs**

Answer 50

alpha-ketoglutarate (5C) + NAD -\> Succinyl-CoA (4C) + **CO2** + **NADH** + H enzyme: alpha-ketoglutarate dyhydrogenase oxidative decarboxylation NADH=**3 ATPs** multienzyme complex composed of 3 subunits E1, E2, E3 requires CoA, NAD, TPP, Lipoic Acid, and FAD Allosteric enzyme inhibited by increased levels of succinyl CoA, NADH, ATP

Answer 51

Succinyl-CoA (4C) + P -\> Succinate (4C) + CoA enzyme: succinyl-CoA synthetase bond hydrolyzed energy released used for substrate level phosphorylation GDP phosphorylated to **GTP** require inorganic phosphate GTP=**1ATP**

Answer 52

Succinate (4C) + FAD -\> Fumarate (4C) + FADH2 enzyme: succinate dehydogenase oxidation rxn enzyme is integral protein of inner mitochondrial matrix SDH enzyme requires coenzyme uses FAD instead of NAD FADH oxidized in ETC to produce **2 ATPs**

Answer 53

Fumarate (4C) + H2O -\> Malate (4C) enzyme: fumarase hydration rxn lose double bond

Answer 54

Malate (4C) + NAD -\> Oxaloacetate (4C) + **NADH** + H enzyme: malate dehydrogenase oxidation rxn NADH=3ATPs

Answer 55

acetyl CoA step 3 NADH = 3 ATPs step 4 NADH = 3 ATPs step 5 GTP = 1 ATP step 6 FADH2 = 2 ATPs step 8 NADH = 3 ATPs oxaloacetate 12 ATPs x 2 acetyl CoA = 24 ATPs

Answer 56

inner mitochondrial membrane oxidative phosphorylation occurs oxidation of a metabolite by oxygen and phosphorylation of ADP Electron carries are substances that make up ETC contain prosthetic groups which are either e- acceptors (oxidizing agent) or e- donors (reducing agent) downhill flow of electrons from NADH to FADH2 to O2

Answer 57

electrons pass in ETC H+ are translocated to inner membrane space creating electrical charge and pH difference Complex I - NADH + H to NAD electrons pass to CoQ and 4 H+ to intermembrane. enzyme: NADH dehydrogenase Complex II - FADH2 to FAD electrons and hydrogens pass to CoQ. enzyme succinate dehydrogenase CoQ transports electrons to Complex III Complex III - H to intermembrane heme (Cu & Fe) Cyt C transports electrons to Complex IV Complex IV - reduces O2 to form H2O heme (Cu & Fe) electrical change and pH difference provide driving energy Complex V - ATP-synthase enzyme protein changes conformation results in ATP synthesis and movement of H back to mitochondrial matix heme holds apart electrons until 4 are acheived then gives

Answer 58

pentose phosphate pathway purpose is to generate intermediates Products: 1. **Pentose Phosphates** - for DNA, RNA, and nucleotide synthesis 2. reduced cosubstrate NADP to **NADPH** - reducing agent for biosynthesis of fatty acids and cholesterol very efficient - recycling 2 ribose to fructose-6-phosphate to glucose

Answer 59

formation of glucose by liver or kidney from nonCHO precursors purpose: maintain blood glucose level: fasting sustained excercise, stress, and hypoglycaemia when glucose storage is low or tissue without mitochondria (anaerobic) rely on it (nerve cells and RBC) pyruvate to PEP has to be done by OAA by pyruvate carbosylase PEP to pyruvate by phyruvate kinase lactate -\> pyruvate (cyto) moves to mito amino acids -\> pyruvate or oxaloacetate in mito glycerol -\> DHAP -\> G3P all in cyto bypass irreversible steps in glycolysis to produce glucose

Answer 60

pyruvate (3C) to OAA (4C) step 1 of gluconeogenesis allosteric enzyme postively regulated by Acetyl CoA Pyruvate + HCO3 + ATP \<-\> OAA + ADP + P + H elongation process need bicarbonate when low CHO pyruvate has to be from AAs, lactate, glycerol to make OAA needed for TCA starvation, low CHO diet, infection, and trauma glucose needed for anaerobic tissues brain RBC

Answer 61

male or female 130 g/day