Metabolism

Question 1

Carbs: uses in body

Answer 1

■ Glucose - fuel used by cells to make ATP
-Some cells use fats for energy
-Neurons and RBCs ~ entirely on glucose; neurons die quickly without glucose

■ Excess glucose converted to glycogen or fat and stored

■ Fructose and galactose converted to glucose by liver before circulation

Question 2

Liver makes _% of cholesterol

Answer 2

85%

Question 3

Lipids: uses in body

Answer 3

■ Help absorb fat-soluble vitamins
■ Major fuel of hepatocytes and skeletal muscle
■ Phospholipids essential in myelin sheaths and all cell membranes
■ Adipose tissue à protection, insulation, fuel storage
■ Prostaglandins à smooth muscle contraction, BP control, inflammation
■ Cholesterol stabilizes membranes; precursor of bile salts, steroid hormones

Question 4

All-or-none rule

Answer 4

All amino acids needed must be present for protein synthesis; if not, amino acids used for energy

Question 5

4 types of nitrogen compounds

Answer 5

1) Amino acids:
■ framework of all proteins, glycoproteins, and lipoproteins

2) Purines and pyrimidines:
■ nitrogenous bases of RNA and DNA

3) Creatine:
■ energy storage in muscle (creatine phosphate)

4) Porphyrins:
■ bind metal ions
■ essential to hemoglobin, myoglobin, and cytochromes

Question 6

Nitrogen balance occurs when

Answer 6

■ nitrogen absorbed from the diet (mainly protein)
■ balances nitrogen lost in urine and feces

Question 7

(+) nitrogen balance

Answer 7

■ Individuals actively synthesizing N compounds:
-need to absorb more nitrogen than they excrete
-e.g., growing children, athletes, and pregnant women

Question 8

(-) nitrogen balance

Answer 8

■ When excretion exceeds ingestion
-Starvation or muscle wasting

Question 9

7 minerals required in moderate amounts

Answer 9

Calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium

Question 10

Fat-soluble vitamins

Answer 10

■ Vitamins A, D, E, and K:
-are absorbed primarily from the digestive tract along with lipids of micelles
-normally diffuse into cell membranes and lipids in liver and adipose tissue

Question 11

Vitamin A

Answer 11

■ Provitamin A (Beta –carotene)

■ A structural component of rhodopsin pigment retinal; Antioxidant
-needed for scotopic (low light) vision
-Deficiency Þ night blindness

■ OD toxic signs & symptoms include:
-Headache, Chapped lips, Blurred vision, Liver toxicity, Alopecia (hair loss), Menstrual irregularities, Tinnitus (ringing in ears)

Question 12

Vitamin D (calciferol)

Answer 12

■ Is converted to calcitriol:
-which increases rate of intestinal calcium and phosphorus absorption

Deficiencies result in:
-Osteomalacia in adults leading to weakening of the skeleton and pathologic fracture
-Rickets in children marked by poorly mineralized, soft bone

■ Common cause of deficiency is steatorrhea – a fat malabsorption syndrome

■ Toxicity:
-Brain, cardiovascular and kidney damage.

Question 13

Vitamin E (tocopherol)

Answer 13

■ Stabilizes intracellular membranes
■ popular antioxidant
■ Needed for Hair/skin maintenance, reproductive patency
■ No reproducible, clinical signs and symptoms of overdose toxicity

Question 14

Vitamin K (aquamephyton, antihemorrhagic vitamin)

Answer 14

■ Helps synthesize several proteins:
-including 3 clotting factors including Prothrombin

■ produced by bacteria in large intestine bowel

■ Note: Coumadin (anticoagulant) - blocks Vit. K uptake and utilization to decrease Prothrombin formation by liver and prolongs clotting times

■ overdose toxicity can lead to liver damage and anemia

Question 15

Vitamin reserves

Answer 15

■ The body contains significant reserves of fat-soluble vitamins
■ Normal metabolism can continue several months without dietary sources

Question 16

Water-soluble vitamins

Answer 16

■ Are components of coenzymes

■ Are rapidly exchanged between fluid in digestive tract and circulating blood:
-excess is excreted in urine

Question 17

Bacterial inhabitants of intestines produce small amounts of:

Answer 17

■ fat-soluble vitamin K
■ some water-soluble vitamins

Question 18

Vitamin C- Absorbic Acid

Answer 18

▪ Promotes the laying down of collagen in connective tissues – antioxidant
▪ Overdose toxicity – Gi upset
▪ Deficiency results in scurvy – a connective tissue disorder

Question 19

B-complex vitamins

Answer 19

■ most act as coenzymes for enzymes of intermediary metabolism
■ NOTE : B6 (Pyridoxine) - is linked to sensory neuropathies in high doses with S & S including: Numbness of hands/feet, unstable gait, decreased deep tendon reflexes
■ Niacin (B3; Component of NAD+) - Low dose toxicity ® skin flush; High dose toxicity ® skin rash, liver toxicity

Question 20

Metabolism

Answer 20

Biochemical reactions inside cells involving nutrients

■ Enzymes shift high-energy phosphate groups of ATP to other molecules (phosphorylation)

■ Phosphorylated molecules activated to perform cellular functions

Question 21

Anabolism

Answer 21

synthesis of large molecules from small ones
■ Ex. Amino acids ➡️proteins
■ Endergonic = Energy Requiring with energy provided by ATP

Question 22

Catabolism

Answer 22

hydrolysis of complex structures to simpler ones
■ Ex. Proteins ➡️amino acids
■ Exergonic = Releases energy used to synthesize high-energy compounds (e.g., ATP)

Question 23

Cellular respiration

Answer 23

Catabolism of food fuels ➡️capture of energy to form ATP in cells

Question 24

3 stages in processing nutrients

Answer 24

1) Digestion, absorption, and transport to tissues
2)Cellular processing (in cytoplasm)
■ Synthesis of lipids, proteins, and glycogen, or
■ Catabolism (glycolysis) into pyruvic acid and acetyl CoA
3) Oxidative (mitochondrial) breakdown of intermediates into CO2, water, and ATP

Question 25

Cellular respiration

Answer 25

■ Goal= trap chemical energy in ATP -Energy also stored in glycogen and fats -Oxidation of food for fuel -Step by step removal of pairs of hydrogen atoms (and electron pairs) from substrates à only CO2 left ■ Includes glycolysis, Krebs cycle, oxidative phosphorylation

Question 26

Oxidation

Answer 26

Gain of oxygen or loss of hydrogen atoms

Question 27

Oxidation-reduction (redox) reactions

Answer 27

■ Oxidized substances lose electrons and energy ■ Reduced substances gain electrons and energy ■ Catalyzed by enzymes

Question 28

Dehydrogenases

Answer 28

Removal of hydrogen atoms

Question 29

Oxidases

Answer 29

Transfer of oxygen

Question 30

Oxidation-reduction (redox) reactions usually require the help of…

Answer 30

vitamin B derivatives ■ Coenzymes act as hydrogen (or electron) acceptors ■ Nicotinamide adenine dinucleotide (NAD+) ■ Flavin adenine dinucleotide (FAD)

Question 31

NAD (coenzyme)

Answer 31

■ Nicotinamide adenine dinucleotide (NAD+, Oxidized form) ■ A derivative of vitamin B3 niacin ■ Is reduced to NADH + H+ ■ NADH is the reduced containing form

Question 32

FAD (coenzyme)

Answer 32

■ Flavin adenine dinucleotide (FAD+, Oxidized form) ■ A derivative of vitamin B2 riboflavin ■ Is reduced to FADH2 + H+ ■ FADH2 is the energy containing form ■ Both accept hydrogen atoms from TCA cycle: ■ gaining 2 electrons

Question 33

Metabolic pathway

Answer 33

These are a series of steps in the synthesis or breakdown of a molecule

Question 34

Allosteric regulation of enzymes

Answer 34

■ Is the regulation of an enzyme by the binding of a substance at a site other than the active site ■ This substance is called an allosteric regulator ■ Phosphofructokinase is an enzyme important early in the glycolysis pathway which leads to the eventual build up of ATP ■ It is inhibited by ATP build up ■ It is stimulated by ADP build up

Question 35

2 mechanism of ATP synthesis

Answer 35

1) Substrate-level phosphorylation 2) Oxidative phosphorylation

Question 36

Substrate-level phosphorylation

Answer 36

■ High-energy phosphate groups directly transferred from phosphorylated substrates to ADP ■ Occurs twice in glycolysis and once in Krebs cycle

Question 37

Oxidative phosphorylation

Answer 37

■ More complex; produces most ATP ■ Chemiosmotic process ■ Couples movement of substances across membrane to chemical reactions ■ Energy used to pump H+ across inner mitochondrial membrane à ■ As flows back through ATP synthase membrane channel ➡️energy used to phosphorylate ADP

Question 38

Carb metabolism

Answer 38

Oxidation of glucose ■ C6H12O6 + 6O2 à 6H2O + 6CO2 + 32 ATP + heat ■ Glucose enters cells by facilitated diffusion ■ Phosphorylated to glucose-6-phosphate ■ Most cells lack enzymes for reverse reaction à traps glucose inside cell ■ Cells in intestine, kidney, liver can reverse reaction and release glucose ■ Keeps intracellular glucose concentration low à continued glucose entry

Question 39

Complete glucose catabolism requires these 3 pathways

Answer 39

■ Glycolysis ■ Krebs cycle ■ Electron transport chain and oxidative phosphorylation

Question 40

Glycolysis

Answer 40

■ 10-step pathway ■ Anaerobic; occurs despite presence/absence of O2 ■ Occurs in cytosol ■ Glucose ® 2 pyruvic acid molecules

Question 41

3 major phases of glycolysis

Answer 41

1) Sugar activation 2) Sugar cleavage 3) Sugar oxidation and ATP formation

Question 42

Sugar activation

Answer 42

■ Glucose phosphorylated by 2 ATP alpha fructose-1,6-bisphosphate ■ Energy investment phase -provides activation energy for later reactions

Question 43

Sugar cleavage

Answer 43

■ Fructose-1,6-bisphosphate à two 3-carbon fragments; isomers ■ Dihydroxyacetone phosphate ■ Quickly reverses to glyceraldehyde 3-phosphate ■ Glyceraldehyde-3-phosphate

Question 44

Sugar oxidation and ATP formation

Answer 44

■ Six steps; two major events ■ Two 3-carbon fragments oxidized (reducing NAD+) ■ Inorganic phosphate groups (Pi) attached to each oxidized fragment ■ Phosphate group cleavage ➡️4 ATP formed by substrate-level Phosphorylation

Question 45

Final product of glycolysis

Answer 45

■ 2 pyruvic acid (C3H4O3) ■ 2 NADH + H+ (reduced NAD+) ■ Net gain of 2 ATP (2 used in sugar activation)

Question 46

For glycolysis to continue…

Answer 46

NAD+ must be present to accept hydrogen atoms

Question 47

Glycolysis: supply of NAD+ limited

Answer 47

■ NADH must donate its accepted hydrogen atoms to become NAD+ again ➡️glycolysis to continue ■ If oxygen present, occurs in mitochondria during electron transport chain ■ If no oxygen present NADH gives hydrogen atoms back to pyruvic acid, educing it à lactic acid

Question 48

Glycolysis: fate of lactic acid

Answer 48

■ Most leaves cell à liver ■ May convert glucose-6-phosphate for storage as glycogen or de-phosphorylate and release glucose to blood

Question 49

Krebs cycle (citric acid cycle)

Answer 49

-Occurs in mitochondrial matrix if oxygen is present -Fueled by pyruvic acid and fatty acids -does not directly use O2 -NADH molecules must be oxidized in electron transport chain for Krebs cycle to continue

Question 50

Krebs cycle: transition phase converts pyruvic acid to acetyl coa in 3 steps:

Answer 50

-Decarboxylation - removal of 1 C to produce acetic acid and CO2 -Oxidation – H atoms removed from acetic acid; picked up by NAD+ à NADH + H+ -Formation of acetyl CoA - Acetic acid + coenzyme A à acetyl coenzyme A (acetyl CoA)

Question 51

Coenzyme A (CoA): Krebs cycle

Answer 51

■ Derived from pantothenic acid (vitamin B5) ■ This is a very important substance involved in many metabolic pathways: ■ Critical for preparing private to enter the TCA cycle ■ Important in the breakdown of fatty acids for energy ■ Necessary for recycling acetylcholine in the synapse

Question 52

Products of each turn of Krebs cycle (yield for 1 acetyl CoA)

Answer 52

3 NADH + H+, 1 FADH2, 2 CO2, 1 ATP

Question 53

Electron transport chain and oxidative phosphorylation

Answer 53

-NADH + H+ and FADH2 (from glycolysis and Krebs cycle) deliver hydrogen atoms -Hydrogen atoms combined with O2 à water -Released energy harnessed à ATP by oxidative phosphorylation -directly uses oxygen -Pumped H+ creates electrochemical proton gradient -Created pH gradient; voltage across membrane -H+ attracted to matrix side of membrane by pH gradient and voltage

Question 54

Cyanide

Answer 54

■ Binds at the oxygen cite on the last cytochrome ■ Blocks the ETS activity ■ No ETS activity no ATP no good

Question 55

Chemiosmosis and (OP)

Answer 55

■ Last step (Phase 2) is chemiosmosis) ■ where H+ diffuses back to matrix via ATP synthase à electrical current ■ ATP synthase uses electrical current à ATP

Question 56

ATP production-summary

Answer 56

■ For 1 glucose molecule processed, cell gains 36 molecules of ATP: ■ 2 from glycolysis ■ 3 from NADH generated in glycolysis ■ 2 from Krebs cycle (through GTP) ■ 23 from ETS

Question 57

Allosteric regulation of enzymes

Answer 57

-regulation of an enzyme by the binding of a substance (allosteric regulator) at a site other than the active site

Question 58

Glycolysis

Answer 58

“Anaerobic metabolism” “Cellular respiration” -breaks down glucose in cytosol into smaller molecules used by mitochondria -does not require O2 Starts 1glucose and ends with 2pyruvate, 2ATP

Question 59

If O2 supplies are adequate

Answer 59

Aerobic reaction -mitochondria absorbs and breaks down pyruvic acid -30ATP (cellular respiration)

Question 60

Oxidative phosphorylation

Answer 60

■ More complex; produces most ATP ■ Chemiosmotic process ■ Couples movement of substances across membrane to chemical reactions ■ Energy used to pump H+ across inner mitochondrial membrane ➡️ ■ As flows back through ATP synthase membrane channel ➡️energy used to phosphorylate ADP

Question 61

Krebs cycle ATP result

Answer 61

2ATP

Question 62

Lactic acid

Answer 62

When O2 is not present, and pyruvic acid cannot go into mitochondria so it gets converted back to lactic acid which goes into blood➡️glucose in liver (gluconeogenesis)

Question 63

Gluconeogenesis

Answer 63

Glucose produced from noncarb precursors in the liver when ⬇️glucose ➕by glucagon

Question 64

Glycogenesis

Answer 64

Glucose➡️glycogen ➕by insulin

Question 65

Glycogenolysis

Answer 65

Glycogen➡️glucose ➕by glucagon

Question 66

Beta oxidation

Answer 66

Breakdown fatty acids into acetly-COA➡️krebs cycle ➕by epi and cortisol(need to breakdown fats for energy) ➖by insulin(builds up fats)

Question 67

LDL

Answer 67

Bad cholesterol Cholesterol transporters ⬆️cholesterol

Question 68

HDL

Answer 68

Cholesterol scavengers ⬇️cholesterol

Question 69

Ammonia

Answer 69

Ammonia is a waste product in the body that is produced when the intestines break down protein from food. Ammonia➡️urea (excreted in urine)

Question 70

Transamination

Answer 70

a chemical reaction that moves an amino group from an amino acid to a keto acid, creating new amino acids and keto acids

Question 71

Deamination

Answer 71

a process that removes an amino group from a molecule, converting it to ammonia

Question 72

Lipogenesis➕ by

Answer 72

Insulin

Question 73

Absorbative state

Answer 73

⬆️glucose Insulin need

Question 74

Postabsorbative state

Answer 74

⬇️glucose Coordinated by: -glucagon -epi -glucocorticoids -GH