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A&P II Ch.25: Metabolism

Terms in this set (47)

metabolism
all chemical reactions that occur in the body
-provide energy for sustaining life processes
-serve as building blocks for synthesis of more complex molecules (such as structural components of cells)
-be stored for future use (ex: glycogen in liver, triglycerides in adipose tissue)
nutrient molecules from food absorbed by the GI tract must be metabolized so that they can... (3)
catabolism
chemical reactions in the body that break down complex molecules into smaller ones, releasing energy (exergonic)
anabolism
chemical reactions in the body that combine simple molecules and monomers to form the body's complex structural and functional components, requiring energy (endergonic)
oxidation reactions
-biological reactions that involve the removal of electrons from an atom/molecule, usually in the removal of hydrogen atoms
-results in a decrease in the potential energy of the atom/molecule
-aka dehydrogenation reactions
reduction reactions
biological reactions that involve the addition of electrons to an atom/molecule; results in an increase in potential energy of the atom/molecule
oxidation-reduction reactions
coupled reactions that occur as one molecule loses electrons (oxidation), and another molecule simultaneously gains electrons (reduction)
NAD & FAD (nicotinamide adenine dinucleotide & flavin adenine dinucleotide)
two coenzymes that carry hydrogen atoms, used in oxidation reactions bc hydrogen cannot remain free in a cell (aka "oxidizing agents")
glucose, fructose, galactose
carbohydrates are absorbed in the form of what 3 monosaccharides?
glucose
what monosaccharide is most commonly used in cells (fructose & galactose are converted to this in the liver)?
cellular respiration
the oxidation of glucose in order to produce ATP;
process that releases energy by breaking down glucose and other food molecules in the presence of oxygen
biological oxidation
the removal of hydrogen atoms (2 at a time ie 2 protons and 2 electrons)
glycolysis
anaerobic cellular respiration that occurs in the cytoplasm of a cell in which one glucose molecule is oxidized and two molecules of pyruvic acid are produced, as well as two molecules of ATP and two energy-containing NADH + H+
phosphorylation
the addition of a phosphate group to each glucose molecule after it enters a cell; requires one molecule of ATP and the enzyme hexokinase to "activate" the glucose
lactic acid (lactate)
in anaerobic conditions, pyruvic acid is converted into ___, which then rapidly diffuses into the blood and travels to hepatocytes, which convert it back into pyruvic acid
acetyl coenzyme A
in aerobic conditions, pyruvic acid from glycolysis is converted into ___
-decarboxylation (loss of a CO2 molecule by pyruvate dehydrogenase)
-dehydrogenation (loss of hydrogens picked up by NAD -- aka oxidation)
-acetyl group (remainder) attaches to coenzyme A, forming acetyl coenzyme A
in aerobic conditions, what three changes occur to pyruvic acid before it enters the Krebs cycle?
Krebs cycle (citric acid cycle)
second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions
Electron Transfer chain
-3rd stage of cellular respiration
-a series of compounds that transfer electrons from electron donors to electron acceptors via redox reactions, and couples this electron transfer with the transfer of protons (H+ ions) across a membrane, creating an electrochemical proton gradient that drives ATP synthesis
-generates the most ATP of all CR stages
cytochromes
electron carrier proteins that play a key role in electron transport chains; receive H+ (and electrons) from NADH, which combine with O2 to form H2O
the cristae & inner membrane of mitochondria
where do the Electron Transfer Chain reactions occur?
-2 from glycolysis
-34 from Krebs cycle
-2 from electron transport chain
total ATP generation formula from CR per one glucose molecule
glycogenesis
conversion of glucose into glycogen (aka animal starch) in the liver, under the influence of insulin (from pancreas)
glycogenolysis
-conversion of glycogen back into glucose
-occurs only in the liver because this is the only place where the enzyme phosphatase is located
-occurs between meals
-stimulated by epinephrine and glucagon (hyperglycemic hormones)
gluconeogenesis
creation of glucose from a new source, such as amino acids, fatty acids, and glycerol; occurs primarily in liver, and stimulated by cortisol and glucagon
lipogenesis
conversion of glucose or amino acids into fats
lipoproteins
spherical particles with an outer shell of proteins, phospholipids, and cholesterol molecules created in the liver and intestine surrounding an inner core of triglycerides and other hydrophobic lipids so that they can be transported in blood
-some oxidized to produce ATP
-some stored in adipose tissue throughout body & liver
-few used as structural molecules or to synthesize other substances (phospholipids, lipoproteins, thromboplastin, myelin sheaths, etc.)
what are the 3 possible fates of lipids in the body?
adipose tissue
where are triglycerides stored?
lipases
adipose cells contain ___ that catalyze the deposition of fats from chylomicrons/VLDLs by hydrolyzing their triglycerides into fatty acids and glycerol; the fatty acids are then taken up by adipocytes for synthesis and storage as triglycerides
(catalyzes lipolysis)
lipolysis
the process of splitting triglycerides into fatty acids and glycerol
epinephrine, norepinephrine, hGH
what are 3 hormones that stimulate lipolysis?
converted into glyceraldehyde 3-phosphate (G-3P), then either converted into glucose (if ATP supply in cell is high), or converted into pyruvic acid to enter the catabolic pathway/Krebs cycle (if ATP supply is low)
what happens to glycerol after it is split from triglyceride molecules during lipolysis?
they are broken down via beta oxidation in the mitochondrial matrix whereby 2 carbons are removed at a time; the 2-carbon fragments can then be converted to acetyl CoA, which can enter the Krebs cycle or can be converted to glucose
what happens to fatty acids after they are split from triglyceride molecules during lipolysis?
ketone bodies
substances created by hepatocytes by condensing excess acetyl CoA molecules (2 at a time), so that they can then leave the cells into the bloodstream and be used in cells elsewhere through the Krebs cycle
(the hepatocytes cannot use the substances themselves, however, because they lack the enzymes to revert them back into acetyl CoA)
acetone & acetoacetic acid
2 forms of ketone bodies
ketosis
an excess of ketone bodies
insulin
what hormone stimulates lipogenesis?
glyceraldehyde 3-phosphate and acetyl coenzyme A
what are 2 possible intermediate links in lipogenesis? (from glucose --> triglycerides)
a carboxyl group & an amino group
all amino acids contain ___ & ___
hGH and insulin
the active transport of newly-absorbed amino acids into body cells is stimulated by ___ and ___
they are immediately re-synthesized into proteins (that can function as enzymes, hormones, structural elements, transportation molecules, or contractile elements in muscles); very little is converted into glucose/triglycerides for energy
what happens to amino acids after they enter body cells?
they must be deaminated (-NH2) and dehydrogenated (oxidized)
what must happen to amino acids before they can enter the Krebs cycle?
it is converted to urea (a non-protein nitrogen waste) via the ornithine cycle
what happens to NH2 from the deamination of amino acids in hepatocytes?
glucose, fatty acids, and ketone bodies
what can amino acids be converted to?
hGH, thyroxine, insulin
what hormones stimulate protein synthesis? (3)
DNA and RNA; on ribosomes of cells
what is protein synthesis directed by? where is it carried out?
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