Chapter 17: Nutrition & Metabolism Flashcards
metabolism
all chemical reactions that occur in the body
catabolism
breakdown of organic molecules that releases energy for synthesizing ATP or other high-energy compoundsonly captures about 40% of the released energy; the rest escapes as heattend to process carbohydrates first, then lipids; amino acids are a last resort and seldom broken down
anabolism
synthesis of new organic molecules through the formation of new chemical bondsrequires more amino acids than lipids and relatively few carbohydrates
metabolic turnover
continuous removal and replacement of cellular structures
four primary reasons for cellular anabolism
•to perform structural maintenance/repairs•to support growth•to produce secretions•to build nutrient reserves
structural/functional/storage components
triglycerides, glycogen, proteins
nutrient pool
fatty acids, glucose, amino acids; source of organic molecules for both catabolism and anabolism
complete catabolism of glucose
produces 36 ATP, 34 of which are produced within the mitochondria
glycolysis
anaerobic process in which glucose is broken down into 2 molecules of pyruvic acid; 2 net ATP are producedrequires glucose, cytoplasmic enzymes, ATP/ADP, and NADfirst step of ATP production; takes place in cytosol
pyruvic acid
creating during glycolysis; accumulation leads to lactic acid buildupcan also be used to synthesize glucose
nicotinamide adenine dinucleotide (NAD)
a coenzyme that removes hydrogen atoms during glycolysis
coenzyme
organic molecules usually derived from vitamins that must be present for a given enzymatic reaction to occur
aerobic metabolism
cellular respiration; mitochondrial activity responsible for ATP productionwaste products are water and carbon dioxiderequires oxygen
anaerobic metabolism
does not require oxygenproduces lactic acid
2 mitochondrial pathways
TCA cycle and electron transport system
tricarboxylic acid (TCA) cycle
“citric acid cycle” or “Krebs cycle”reaction involving a molecule of pyruvic acid which takes place within mitochondria; primary function is to remove hydrogen atoms from organic molecules and transfer them to coenzymes in the electron transport system produces CO2 as waste product; only immediate benefit is formation of 1 GTP per cycle, which equates to 1 ATP per cycle (2 cycles per glucose = 2 ATP per glucose)
guanosine triphosphate (GTP)
high-energy compound created in Krebs cycle; readily converted into ATP
coenzyme A
CoAinvolved in reaction between NAD and pyruvic acid which yields CO2, NADH, and acetyl-CoA
acetyl-CoA
consists of two-carbon acetyl group bound to CoAcannot be used to make glucose because the reaction that removes the carbon dioxide molecule between pyruvic acid and acetyl-CoA cannot be reversedused in lipogenesis to make steroids and nearly all fatty acids
citric acid
produced by adding acetyl group to four-carbon molecule
acetyl group
CH₃CObinds to CoA to form acetyl-CoA and is transferred to a four-carbon molecule to create citric acid
flavine adenine dinucleotide (FAD)
coenzyme which transfers hydrogen ions from citric acid cycle to electron transport system
electron transport system (ETS)
embedded within the inner mitochondrial membrane; comprised of cytochromesdoes not produce ATP directly; merely creates necessary conditions for its productionleads to creation of 95% of cell’s ATP through chemiosmotic conversion of ADP
cytochromes
series of protein-pigment complexes that make up electron transport chain
coenzyme Q
transfers the electrons of hydrogen atoms generated by Krebs cycle to the first cytochrome of the ETS
matrix
Innermost compartment of the mitochondrion
intermembrane space
the fluid filled space between the inner and outer mitochondrial membranes; H+ ions are pumped here by ETS using energy from electron movement
ATP synthase
enzyme located in inner mitochondrial membrane; chemiosmosis of H+ ion passing through generates ATP
chemiosmosis
movement of ions down their electrochemical gradient across a semipermeable membranein metabolism: kinetic energy of H+ ion passing through ATP synthase is used to attach a phosphate group to ADP, forming ATP
lactic acid
created from accumulation of pyruvic acid produced during glycolysis (anaerobic metabolism)
gluconeogenesis
synthesis of glucose from noncarbohydrate (protein or lipid) precursor sourcesfatty acids and many amino acids cannot be used for gluconeogenesis because their breakdown produces acetyl-CoA
glycogen
used to store glucose in liver and skeletal muscle because it is insoluble and therefore does not affect cell’s tonicity
lipolysis
lipid catabolization; lipids are broken down into pieces that can be converted into pyruvic acid or channeled directly into the TCA cyclesproduces more ATP per carbon molecule than glycolysis, but it takes longer to access lipid reserves and it is limited by the availability of oxygen
triglyceride
lipid made of three fatty acid molecules and one glycerol molecule
beta-oxidation
catabolism of fatty acids in which enzymes break them into two-carbon fragments; these fragments then enter the TCA cycle or combine to form ketone bodiescell generates 144 ATP from breakdown of one 18-carbon fatty acid molecule
ketone bodies
short carbon chains made during lipid and amino acid catabolismmetabolized by body cells, who convert them into acetyl-CoAexample is acetone