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A/P I Chapter 25

Terms in this set (44)

Metabolism refers to
all of the chemical reactions that occur in the body
Two types of metabolism
Catabolism and Anabolism
Catabolism
is the chemical reactions that break down complex organic molegucles into simpler ones

catabolic reactions are exergonic (they produce more energy than they consume)

Important sets of catabolic reactions occur in glycolysis, krebs cycle, and the electron transport chain

40% of energy released during catabolism is used for cellular function; the rest converted to heat
Anabolism are
chemical reactions that combine simple molecules and monomers to form the body's complex structural and functional components

Ex. Anabolic reactions are the formation of peptide bonds between amino acids during protein synthesis, building of fatty acids into phospholipids that form the plasma membrane bilayer and th elinkage of glucose monomers to form glycogen

Reactions are endergonic; (they consume more energy than they produce)

Molecule synthesized in anabolic reaction has a limited lifespan, ecept it will be broken down and its atom recycled into other molecules or excreted from the body
ATP
participates most in energy exchanges

couples energy releasing catabolic reactions to energy requiring anabolic reactions

Both catabolic/anabolic reactions can occur at the same time

The energy currency of a living cell

About a billion molecules of ATP per cell

ATP consists of adenine molecule, ribose molecule, and three phosphate groups bond to each other.

ATP links anabolic/catabolic reactions

When terminal phosphate group is split off ATP, adenosine diphosphate (ADP) and a phosphate group are formed. Which then during the catabolic reaction combine ADP and the phosphate group to resynthesize ATP

Some of the energy released during oxidation reaction is captured when ATP is formed. A phosphate group is added to ADP with an input of energy to form ATP. This addition of phosphate group called phosphorylation increases its potential energy

ATP is made by Aerobic Respiration
Phosphorylation use three mechanism to generate ATP
Substrate level phosphorylation-generate ATP by transferring high energy phosphate group from an intermediate compound a substrate, directly to ADP.

Occurs in cytosol in humans

Oxidative phosphorylation-removes electrons from organic compounds and passes them through a series of electron acceptors called electron transport chain, to molecules of O2.

Occurs in Mitochondrial

Photophosphorylation occurs in chlorophyll containing plant cells or certain bacteria that contain other light absorbing pigments.
Oxidation is
the removal of electrons from an atom or molecule

Results in a decrease in the potential energy of the atom or molecule

Dehydrogenation reactions because oxidation involve the loss of hydrogen atoms

Example conversion of lactic acid to pyruvic acid
Reduction is
the opposite of oxidation

It is the addition of electrons to a molecule

Results in increase in the potential energy of a molecule

Example conversion of pyruvic acid into lactic acid
Oxidation/reduction are always coupled
Each time one substance is oxidized, another is reduced. Paired reaction is called oxidation reduction or redox reaction

Oxidation is usually a exergonic reaction. Compounds with many hydrogen atoms such as glucose contain more chemical potential energy than oxidized compounds. Which is why glucose is a valuable nutrient
Carbohydrate Metabolism
Polysaccharides/disaccharides are hydrolyzed into Monosaccharides glucose, fructose and galactose during digestion of carbohydrates

Hepatocytes (liver cells) convert most of the remaining and all of galactose to glucose.

Carbohydrate metabolism is really glucose metabolism

Negative feedback systems maintain blood glucose at 90 mg/100 ml of plasma, a total of 2-3 g of glucose normally circulates in the blood
Fate of Glucose
Body's preferred source for synthesizing ATP, depends on the body's need.

-ATP production: glucose is oxidized to produce ATP

-Amino acid synthesis: Cells can use glucose to form several amino acids that then can be incorporated into proteins

-Glycogen synthesis: Hepatocytes/muscle fibers can perform glycogenesis. Total storage of glycogen is about 125 g in the liver and 375g in skeletal muscles

-Triglyceride synthesis: hepatocytes can trasnform the glucose to glycerol and fatty acids that are used for lipgenesis (the synthesis of triglycerices) which are then put in the adipose tissues.

Before it can be used it has to pass through the plasma membrane and enter the cytsol
Glucose Catabolism
Oxidation of glucose to produce ATP AKA is cellular respiration
Cellular respiration has four sets of reactions
Glycolysis- reactions in which one glucose molecule is oxidized/two molecules of pyruvic acid are produced

Formation of acetyl coenzyme A: a transition time that prepares pyruvic acid for entrance into the Kreb Cycle

Kreb Cycle reactions: oxidize acetyl coenzyme A and produce CO2, ATP, NADH = H+ and FADH2

Electron transport chain reaction: Oxidize NADH +h+ and FADH2 and transfer their electrons to electron carriers

Glycolisis doesn't required oxygen, is can occur under aerobic or anaerobic conditions. Kreb cycle/electron transport require oxygen and referred to as aerobic respiration

If O2 is not available pyruvic acid is converted to a lactic acid. The remaining steps of cellular respriaton do not accur.
Acetyl Coenzyme A
Derived from pantothenic acid (b vitamin)

Enzyme pyruvate dehydrogenase in the mitochondrial converts pyruvic acid to 2 carbon fragment called an acetyle group by removing the cO2. Which is called decarboxylation
Krebs Cycle
Once decarboxylated the remain acetyl group attached to CoA is ready to enter Krebs cyle

Name after found also know as the citric acid cycle

Mitochandrial reactions occur a series of oxidation reductin reactions (which transfer chemical energy) and decarboxylation reactions that release CO2.

Everytime the CoA enters the cyle it make a complete turning starting with production of citric acid and end with formation of oxaloacetic acid.

Glucose makes two turns

Formation of NADH and FADH is the most important outcome of the kreb cylcle because these reduced coenzmes contain the energy originally stored in glucose and then in pyruvic acid.
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