Chapter 27 Flashcards by Tyler White

The food we eat serves two main purposes

It fulfills our energy needs

provides the raw materials to build the compounds
our bodies need

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Before either of these processes can take place, food—
carbohydrates, fats, and proteins—must be

broken down into small molecules that can be absorbed through the intestinal walls

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Complex carbohydrates Examples

Di and Polysaccharides

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Complex carbohydrates in the diet are broken
down by

enzymes and stomach acid to produce monosaccharides

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Also comes from the enzymatic breakdown of glycogen that is stored in the liver and muscles until needed

Glucose

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Once monosaccharides are produced, they can be used either to

build new oligo- and polysaccharides

Or Provide energy

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The specific pathway by which energy is extracted from monosaccharides is called

Glycolysis

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Ingested fats are hydrolyzed by _______ to ______ which are absorbed through the _________

Lipases

Glycerol

Intestine

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The specific pathway used by the cells to obtain energy from fatty acids is
called

b-oxidation

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Proteins are hydrolyzed by

HCl in the stomach

Digestive enzymes (Pepsin)

Intestines ((trypsin, chymotrypsin, and carboxypeptidases)

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The nitrogen of the amino acids is catabolized through

oxidative deamination

urea cycle

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The carbon skeletons of the amino acids enter the common catabolic pathway as either

a-ketoacids (pyruvic, oxaloacetic, and a-ketoglutaric acids)

acetyl coenzyme A

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The first steps of glucose metabolism

energy is consumed rather than released At the expense of 2 molecules of ATP later converted into ADP

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Efficiency is achieved because

A minimal number of chemical
steps are required

Energy-producing factories of the body are localized in the mitochondria

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Third step of glycolysis

a second phosphate group is bonded to yield fructose 1,6-bisphosphate

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glucose is ….

Phosphorylated

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First step of glycolysis

glucose 6-phosphate is formed

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second step of glycolysis

after isomerization to fructose 6-phosphate

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The first 3 steps in glycolysis is called the _______ Process

Activation

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The biochemical pathway
that breaks down glucose to
pyruvate

Glycolysis

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Step 4 in glycolysis

The C6 compound, fructose 1,6-bisphosphate, is broken into two C3 fragments

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Step 5 in glycolysis

glyceraldehyde 3-phosphate is oxidized to 1,3-bisphosphoglycerate

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The two C3 fragments in equilibrium

glyceraldehyde 3-phosphate

dihydroxyacetone phosphate

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Step 6 in glycolysis

The phosphate from the carboxyl group is
transferred to ADP, yielding ATP and 3-phosphoglycerate

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The hydrogen of the aldehyde group is removed by the ___ _________

NAD+ coenzyme

Step 7 in glycolysis

Isomerization

Step 8 in glycolysis

Dehydration

Step 9 in glycolysis

phosphoenolpyruvate loses its remaining phosphate and yields pyruvate and another ATP molecule

the “payoff” step

Step 9

Two ATP molecules produced (one for each C3 fragment) represent

the net yield of ATPs in glycolysis

Step 9 is catalyzed by an enzyme...

pyruvate kinase

This enzyme plays a key role in the regulation of glycolysis

pyruvate kinase

when plenty of ATP is available, glycolysis is...

Shut down

All of these glycolysis reactions occur in the________ outside the _________ Because they occur in the absence of __,

Cytoplasm Mitochondria O2

when ATP is scarce and AMP levels are high, the glycolytic pathway is...

Speeded up

The end product of glycolysis is_______

Pyruvate

Step 10 of glycolysis certain bacteria and yeast, pyruvate undergoes _____________ to produce _______

Decarboxylation Ethanol

glucose 6-phosphate can be shunted to the.... in step 19

Pentose phosphate pathway

The acetyl CoA then enters the _____ _____ _____ in Step 13

Citric acid cycle

Pyruvate goes through an ________ __________ in the presence of _________ _in Step 12 to produce _________

oxidative decarboxylation coenzyme A acetyl CoA

Pentose phosphate pathway can produce _____ and _______ in step 20

NADPH Ribose

______ is needed in many biosynthetic processes, including synthesis of unsaturated fatty acids cholesterol, and amino acids as well as photosynthesis

NADPH

When is glucose 6-phosphate is used in the pentose phosphate pathway

when the body needs these synthetic ingredients more than energy

needed for the synthesis of RNA

Ribose

ribose 5-phosphate can be channeled back to glycolysis through

glyceraldehyde 3-phosphate

NADPH is badly needed in red blood cells as a defense against

oxidative damages

main agent used to keep hemoglobin in its reduced form

Glutathione

an insufficient supply of NADPH leads to

Destruction of Red blood cells causing severe anemia

Most energy production takes place in ______ _______ cells

Skeletal muscle

__ ATP molecules are produced for each NADH+, H+ produced in the cytoplasm, as is the case in the mitochondria

When we construct the energy balance sheet, we use___ ____ molecules for each NADH+, H+ produced in the cytoplasm

2 ATP

The biochemical pathway for the breakdown of glycogen to glucose

Glycogenolysis

the main storage form of the chemical energy of lipids

triglycerides

The first step in glycerol utilization is an activation step. The body uses one ATP molecule to form....

glycerol 1-phosphate

The biochemical pathway that degrades fatty acids to acetyl CoA by removing two carbons at a time and yielding energy

b-oxidation

The glycerol phosphate is oxidized by NAD+ to

dihydroxyacetone phosphate

proposed that the body utilizes fatty acids as an energy source by breaking them down into fragments

Franz Knoop 1904

In the general case of lipid catabolism, this activation occurs in the _____

Cytosol

The fatty acid oxidation occurs inside the ___________, so the acyl group of acyl CoA must pass through the __________ membrane.

mitochondrion mitochondrial

In the first oxidation, two hydrogens are removed, creating a _______ ______ ____between the alpha and beta carbons of the acyl chain

Trans double bond

the acyl group transporter

Carnitine

Step 1 of B oxidation

convert ATP to AMP and inorganic phosphate

Step 2 of B oxidation

dehydrogenation

Step 3 of B oxidation

the double bond is hydrated. An enzyme specifically places the hydroxyl group on C-3, the beta carbon

A secondary alcohol is oxidized to a ______ at the beta carbon

Ketone

Step 4 of B oxidation

The second oxidation; dehydrogenation The two hydrogens and electrons removed are transferred to the NAD+

Step 5 of B oxidation

the enzyme thiolase cleaves the terminal C2 fragment from the chain

a typical and quite abundant fatty acid the C18 saturated fatty acid.

stearic acid

After the B oxidation cycle is over, The cycle then starts again with __________, which is now two carbon atoms shorter

the remaining acyl CoA

Produced from malate, but it is also produced by the carboxylation of phosphoenolpyruvate (PEP) Essential for the continuous operation of the citric acid cycle

Oxaloacetate

The liver is able to condense two acetyl CoA molecules to produce

acetoacetyl CoA

When the acetoacetyl CoA is hydrolyzed, it yields __________, which can be reduced to form b-hydroxybutyrate

acetoacetate

These two compounds, together with smaller amounts of acetone, are collectively called A collective name for acetone, acetoacetate, and b-hydroxybutyrate; compounds produced from acetyl CoA in the liver that are used as a fuel for energy production by muscle cells and neurons

ketone bodies

The proteins of our foods are_________ to amino acids in __________

Hydrolyzed Digestion

Unlike carbohydrates and fats, however, they cannot be stored, so excess amino acids are ....

Catabolized for energy production

Nitrogen catabolism in the liver occurs in three stages:

Transamination Oxidative deamination The urea cycle

The exchange of the amino group of an amino acid and a keto group of an a-ketoacid

Transamination

In the first stage, transamination, amino acids transfer their amino groups to....

a-ketoglutarate

The second stage of nitrogen catabolism is the _________ -_________ of glutamate, which occurs in the mitochondrion

Oxidative deamination

The reaction in which the amino group of an amino acid is removed and an a-ketoacid is formed

Oxidative deamination

A cyclic pathway that produces urea from ammonia and carbon dioxide

Urea cycle

In the third stage, the NH4+ is converted to urea through the ____ _____

Urea Cycle

Step 1 of the urea cycle

NH4+ is condensed with CO2 in the mitochondrion to form an unstable compound, carbamoyl phosphate

Step 2 of the urea cycle

Carbamoyl phosphate is condensed with ornithine

Step 3 of the urea cycle

A second condensation reaction in the cytoplasm takes place between citrulline and aspartate, forming argininosuccinate

Step 4 of the urea cycle

the argininosuccinate is split into arginine and fumarate

Step 5 of the urea cycle

arginine is hydrolyzed to urea and ornithine

The ornithine reenters the _________, completing the cycle

mitochondrion

After transamination of amino acids to glutamate, the alpha amino group is removed from glutamate by....

oxidative deamination

Those amino acids that yield a carbon skeleton that is degraded to pyruvate or another intermediate capable of conversion to glucose (such as oxaloacetate) are called ....

glucogenic

example of a ketogenic amino acid

ketogenic

amino acids are both glucogenic and ketogenic—for example...

phenylalanine