NAME __________HUN 1201 Nutrition

Metabolic WorksheetChapter 7 Assignment

This Metabolic Worksheet is designed to enhance your understanding of the metabolicpathways that the human body uses to produce energy from the foods that we eat.

To complete the worksheet, simply click on each blank and type in your answers. Savethe completed worksheet to your computer and submit it to the Chapter 7 Assignmentdropbox.

Carbohydrate (Glucose) In The Energy Pathways

A. GLYCOLYSIS: The breakdown of glucose to pyruvate to energy

There are __________ carbons in a glucose molecule. One glucose molecule willproduce __________ pyruvate molecules consisting of __________ carbons each.The metabolic pathway that breaks down glucose to pyruvate is known as__________, which occurs in the __________ of the cell and the process is__________, which means “without oxygen.” Limited energy in the form of__________ is produced during glycolysis.

B. THE LACTIC ACID CYCLE: An alternate anaerobic pathway to energyproduction.

If enough oxygen is NOT available, especially during high-intensity exercise,pyruvate converts to __________, which accumulates in the __________ due tolimited availability of oxygen and limited clearance of __________. When musclesrelax, circulating blood carries lactic acid to the __________, which will then convertit to __________. The conversion of lactic acid to glucose is known as the__________.

C. THE TRICARBOXYLIC ACID (TCA) CYCLE: The aerobic pathway toenergy production.

If enough oxygen is available to the cell, pyruvate converts to a 2-carbon compoundknown as __________. The “CoA” part of acetyl CoA is a coenzyme that comesfrom the B vitamin, __________. If enough oxygen is available to the cell and thecell needs more ATP (energy), acetyl CoA enters the __________ . Other names forthe TCA cycle include __________ and __________. The TCA cycle occurs in the__________ of the cell and the process is __________, which means “with oxygen.”

If pyruvate continues through the energy pathway, two of the three carbons inpyruvate combine with coenzyme A to become __________ and the third carbon isexpelled as __________. Pyruvate can convert to __________ or __________, butacetyl CoA cannot convert to __________ or __________.

Acetyl CoA will proceed through the TCA cycle ONLY if the cell needs more__________. Acetyl CoA that does not enter the TCA cycle will be converted andstored as __________. When acetyl CoA enters the TCA cycle, it converts to severalother compounds that produce __________, __________, and provides __________atoms. The TCA cycle provides __________ atoms for the electron transport chain toproduce __________ and __________.

D. THE ELECTRON TRANSPORT CHAIN (ETC): The pathway to abundantenergy production

When acetyl CoA converts to other compounds in the TCA cycle, __________ atomswith their energetic __________ are removed from those compounds. The ETCoccurs in the __________ of the cell and the process is __________, which means“with oxygen.”

The transfer of hydrogen to the ETC is made possible because of __________ madefrom B vitamins. As hydrogen with electrons is passed down the ETC, it releasesenergy which is captured in __________. At the end of the ETC, very low-energyhydrogen atoms combine with oxygen to form __________. The number of__________ atoms that enter the ETC determines the amount of __________ that willbe produced.

Fat In The Energy Pathways

When dietary fat is needed for energy, the 3-carbon backbone of the triglyceridemolecule, known as __________, enters the energy pathway between the compounds__________ and __________. The __________ portions of a triglyceride are takenapart, 2 carbons at a time, through a process known as __________. A fatty acid thatcontains 20 carbons will yield __________ acetyl CoA molecules.

The 2-carbon fragments of a fatty acid can enter the energy pathway only as__________ compounds that can enter the TCA cycle ONLY if the cell needs more__________. Acetyl CoA from triglyceride that is not used for ATP (energy) will beconverted and stored as __________. If acetyl CoA from triglyceride enters the TCAcycle, the process continues through the __________ to produce abundant ATP(energy) and water.

When a triglyceride molecule breaks down into its basic units, __________ can beused to make glucose, but __________ cannot be used to make glucose.

Protein In The Energy Pathways

Before protein can enter the energy pathway, enzymes must first __________(remove nitrogen groups from) the amino acids. The process produces the compound__________ that can then be used to make other amino acids or excreted as__________.

An amino acid that can enter the energy pathway between glucose and pyruvate isreferred to as a __________ amino acid. An amino acid that can enter the energypathway as acetyl CoA is referred to as a __________ amino acid. Amino acids thatconvert to pyruvate can “go up” to make __________ or “go down” to make__________. Amino acids that convert to acetyl CoA will enter the TCA cycleONLY if the cell needs more __________. Amino acids that convert to acetyl CoAcannot be used to make __________. After acetyl CoA enters the TCA cycle, theprocess continues on through the __________ as described previously for dietarycarbohydrate and fat.

Just like dietary carbohydrate and fat that is used for energy, dietary protein can alsoprovide __________ atoms that will enter the electron transport chain to produce__________. If ATP (energy) is NOT needed from amino acids, they will beconverted and stored as __________.

Summary Of Energy Metabolism

All dietary carbohydrate, fat, and protein can break down to the common compound__________ that can enter the TCA cycle. Acetyl CoA enters the TCA cycle only ifthe cell needs more __________. Most of the ATP (energy) made is produced in thepart of the energy pathway known as the __________.

Abundant ATP (energy) comes from the dietary fat because fat provides more__________. The more hydrogen atoms provided, the more __________ will beproduced. If eaten in excess of the body’s needs, all dietary carbohydrate, fat, andprotein will be converted and stored as __________.