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A&p2 > Metabolism > Flashcards

Metabolism Flashcards

1
Q

Carbs: uses in body

A

■ 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

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2
Q

Liver makes _% of cholesterol

A

85%

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3
Q

Lipids: uses in body

A

■ 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

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4
Q

All-or-none rule

A

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

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5
Q

4 types of nitrogen compounds

A

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

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6
Q

Nitrogen balance occurs when

A

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

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7
Q

(+) nitrogen balance

A

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

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8
Q

(-) nitrogen balance

A

■ When excretion exceeds ingestion
-Starvation or muscle wasting

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9
Q

7 minerals required in moderate amounts

A

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

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10
Q

Fat-soluble vitamins

A

■ 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

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11
Q

Vitamin A

A

■ 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)

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12
Q

Vitamin D (calciferol)

A

■ 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.

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13
Q

Vitamin E (tocopherol)

A

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

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14
Q

Vitamin K (aquamephyton, antihemorrhagic vitamin)

A

■ 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

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15
Q

Vitamin reserves

A

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

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16
Q

Water-soluble vitamins

A

■ Are components of coenzymes

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

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17
Q

Bacterial inhabitants of intestines produce small amounts of:

A

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

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18
Q

Vitamin C- Absorbic Acid

A

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

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19
Q

B-complex vitamins

A

■ 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

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20
Q

Metabolism

A

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

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21
Q

Anabolism

A

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

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22
Q

Catabolism

A

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

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23
Q

Cellular respiration

A

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

24
Q

3 stages in processing nutrients

A

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

25
Q

Cellular respiration

A

■ 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

26
Q

Oxidation

A

Gain of oxygen or loss of hydrogen atoms

27
Q

Oxidation-reduction (redox) reactions

A

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

28
Q

Dehydrogenases

A

Removal of hydrogen atoms

29
Q

Oxidases

A

Transfer of oxygen

30
Q

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

A

vitamin B derivatives

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

31
Q

NAD (coenzyme)

A

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

32
Q

FAD (coenzyme)

A

■ 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

33
Q

Metabolic pathway

A

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

34
Q

Allosteric regulation of enzymes

A

■ 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

35
Q

2 mechanism of ATP synthesis

A

1) Substrate-level phosphorylation
2) Oxidative phosphorylation

36
Q

Substrate-level phosphorylation

A

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

37
Q

Oxidative phosphorylation

A

■ 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

38
Q

Carb metabolism

A

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

39
Q

Complete glucose catabolism requires these 3 pathways

A

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

40
Q

Glycolysis

A

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

41
Q

3 major phases of glycolysis

A

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

42
Q

Sugar activation

A

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

43
Q

Sugar cleavage

A

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

44
Q

Sugar oxidation and ATP formation

A

■ 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

45
Q

Final product of glycolysis

A

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

46
Q

For glycolysis to continue…

A

NAD+ must be present to accept hydrogen atoms

47
Q

Glycolysis: supply of NAD+ limited

A

■ 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

48
Q

Glycolysis: fate of lactic acid

A

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

49
Q

Krebs cycle (citric acid cycle)

A

-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

50
Q

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

A

-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)

51
Q

Coenzyme A (CoA): Krebs cycle

A

■ 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

52
Q

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

A

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

53
Q

Electron transport chain and oxidative phosphorylation

A

-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

54
Q

Cyanide

A

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

55
Q

Chemiosmosis and (OP)

A

■ 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

56
Q

ATP production-summary

A

■ 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

A&p2 (21 decks)

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