NUTR 445 FINAL EXAM

Question 1

Functional Categories of Proteins

Answer 1

Integral and Peripheral (receptors), (channels), (cell adhesion molecules), (enzymes)

Question 2

Covalent Modification

Answer 2

1. Addition or hydrolytic removal of phosphate groups to or from the enzyme (glycogenesis- creation of glycogen from glucose) (glycogenolysis- breakdown of glycogen to produce glucose)
2. Cleavage (enzymes are synthesized as inactive proenzymes (zymogens), activate the proenzymes by hydrolyzing them)

Question 3

Allosteric Enzyme Modification

Answer 3

Another site besides the catalytic site (modulators bind to allosteric sites and influence the activity of the regulatory enzymes)
Can either be inhibited or increased depending on the negative or positive modulator (phosphofructokinase- citrate is the negative modulator of phosphofructokinase in the TCA cycle)

Question 4

Induction

Answer 4

Changes in the concentration of certain inducible enzymes by increasing enzyme synthesis (caused by steroid hormones or thyroid hormones), dietary changes impact

Question 5

Oxidoreductases (dehydrogenases, reductases, oxidases, peroxidases, hydroxylases, and oxygenases)

Answer 5

Enzymes catalyze all reactions in which one compound is oxidized and another is reduced.

Question 6

Transferases Included in this group of enzymes are transketolase, transaldolase, trans methylase, and transaminases.

Answer 6

Enzymes that catalyze reactions not involving oxidation and reduction in which a functional group is transferred from one substrate to another.
The transaminases (α-amino transferases), which figure so prominently in protein metabolism, are located primarily in the mitochondrial matrix.

Question 7

Hydrolases (esterases, amidases, peptidases, phosphatases, and glycosidases)

Answer 7

Enzymes catalyze the cleavage of bonds between carbon atoms and some other kind of atom by adding water. Digestive enzymes fall within this classification, as do those enzymes contained within lysosomes.

Question 8

Lyases (decarboxylases, aldolases, synthetases, cleavage enzymes, deaminases, nucleotide cyclases, hydrases or hydratases, and dehydratases)

Answer 8

Enzymes that catalyze cleavage of carbon–carbon, carbon–sulfur, and certain carbon–nitrogen bonds (peptide bonds excluded) without hydrolysis or oxidation-reduction. Citrate lyase, which frees acetyl-CoA for fatty acid synthesis in the cytosol, is a good example of an enzyme belonging to this classification.

Question 9

Isomerases (racemases, epimerases, and mutases)

Answer 9

Enzymes that catalyze the interconversion of optical or geometric isomers. Phosphohexose isomerase, which converts glucose-6-phosphate to fructose-6-phosphate in glycolysis (occurring in the cytosol), exemplifies this particular class of enzyme.

Question 10

Ligases

Answer 10

Enzymes catalyze the formation of bonds between carbon and a variety of other atoms, including oxygen, sulfur, and nitrogen. Forming bonds catalyzed by ligases requires energy that usually is provided by the hydrolysis of ATP. An example of a ligase is acetyl-CoA carboxylase, which initiates fatty acid synthesis in the cytosol. Through the action of acetyl-CoA carboxylase, a bicarbonate ion is attached to acetyl-CoA to form malonyl-CoA, the initial compound formed in the synthesis of fatty acids.

Question 11

Diagnostic Capability Criteria

Answer 11

The enzyme must have a sufficiently high degree of organ or tissue specificity.

A steep concentration gradient of enzyme activity must exist between the interior and exterior of the cells under normal conditions. This makes small increases in serum activity detectible (assuming the laboratory assay is sensitive).

The enzyme must function in the cytosol of the cell so that it leaks out whenever the plasma membrane suffers significant damage.

The enzyme must be stable for a reasonable time period in the vascular compartment.

Question 12

Diffusion

Answer 12

Direct transport from high concentration to low concentration

Question 13

Facilitated Diffusion

Answer 13

Passive transport (use of transport proteins or channels to move molecules from high concentration to low concentration)

Question 14

Active Transport

Answer 14

Against concentration gradient, (low concentration to high concentration, requires energy input from the cell)

Question 15

Endocytosis

Answer 15

Cells engulf extracellular material and transport it into the cell by forming a membrane-bound vesicle (carrying nutrients, signaling molecules, and pathogens)

Question 16

Energy Release and Consumption

Answer 16

Release- Energy is released as heat (by means of the combustion of flammable substances or can be preserved in the form of other chemical energy) —-> Energy cannot be created or destroyed (just transformed)
New high-energy bonds are a usable source of energy driving energy-requiring processes in the form of ATP—> 40% of the chemical energy from combustion is conserved

Question 17

Free Energy

Answer 17

Potential energy inherent in the chemical bonds of nutrients (capable of doing work at constant temperature and pressure)

Question 18

Exothermic Reactions

Answer 18

Reaction in which the reactants have more free energy than the products (gives off energy as heat)- downhill reaction

Question 19

Endothermic Reactions

Answer 19

Reaction in which the products have more free energy than the reactants (therefore requires energy)- uphill reaction

Question 20

Transition State

Answer 20

Energy level at which reactant molecules have been activated and can undergo an exothermic reaction

Question 21

Activation Energy

Answer 21

Energy introduced into the reactant molecules to activate them to the transition state so that an exothermic reaction can take place

Question 22

Functions of the GI Tract

Answer 22

Ingestion, Digestion (Mechanical and Chemical), Absorption, and Excretion

Question 23

Layers of the GI Tract

Answer 23

Mucosa, Submucosa, Muscularis Externa, and the Serosa

Question 24

Primary Organs of the GI Tract

Answer 24

Oral cavity, pharynx, esophagus, stomach, small intestine, and the large intestine

Question 25

Accessory Organs of the GI Tract

Answer 25

Salivary Glands, Liver, Gallbladder, and the Pancreas

Question 26

Three Salivary Glands

Answer 26

Parotid Gland, Submandibular Gland, and the Sublingual Gland

Question 27

Salivary A-Amylase

Answer 27

Released by the salivary glands to breakdown a (1,4) glycosidic bonds of starch in the mouth

Question 28

Lingual Lipase

Answer 28

Secreted by the lingual serous glands on the tongue and in the back of the mouth (hydrolyzes dietary triacylglycerols after food has been swallowed and is in the stomach)

Question 29

Function of Mucus

Answer 29

In the saliva, lubricates food and coats/protects the oral mucosa

Question 30

Neck (mucous) cells

Answer 30

Secrete mucus

Question 31

Parietal (oxyntic) cells, which secrete hydrochloric acid and intrinsic factor

Answer 31

Secrete HCl and intrinsic factor

Question 32

Chief (peptic) cells, which secrete pepsinogen and gastric lipase

Answer 32

Secrete pepsinogen and gastric lipase

Question 33

Enteroendocrine cells

Answer 33

Secrete a variety of hormones

Question 34

Macronutrient Digestion in the Mouth

Answer 34

1. Mechanical breakdown, moistening, and mixing of food with saliva
2. Saliva is released from the salivary glands (parotid, submandibular, and sublingual)
3. Salivary A-Amylase (hydrolyzes a (1,4) glycosidic bonds in starch)
4. Lingual lipase (Secreted from the lingual serous glands, hydrolyzes dietary triacylglycerols after food has been swallowed and is in the stomach)
5. Mucus (Lubricates food and coats/protects the oral mucosa)

Question 35

Saliva Contains

Answer 35

Water, electrolytes, mucus, enzymes, antibacterial/antiviral proteins, R protein, solutes)

Question 36

Macronutrient Digestion in the Stomach (Proteins)

Answer 36

1. Gastroesophageal Sphincter
2. Gastric Juice (the enzyme pepsin is initially secreted as a zymogen called pepsinogen)
3. Pepsinogen is secreted into the gastric lumen by chief cells (stimulated by acetylcholine or an acid)
4. Pepsinogen is activated to pepsin by HCl or previously formed pepsin
5. Pepsin acts as a protease (an enzyme that hydrolyzes proteins) —-> specifically acts as an endopeptidase (hydrolyzes the peptide bonds within proteins)

Question 37

Macronutrient Digestion in the Stomach (Triacylglycerols)

Answer 37

1. Gastric chief cells secrete gastric lipase (an enzyme that hydrolyzes fatty acids from glycerol third carbon in triacylglycerols)
2. Responsible for 20% of lipid digestion

Question 38

Macronutrient Digestion in the Stomach (Starch)

Answer 38

Salivary a-amylase from the mouth retains some activity in the stomach before it is inactivated by the low pH of the gastric juice

Question 39

The cardia region

Answer 39

Lies below the gastroesophageal sphincter and receives the swallowed food (bolus) from the esophagus.

Question 40

The fundus region

Answer 40

Lies adjacent or lateral to and above the cardia.

Question 41

The body region (the larger central region)

Answer 41

Serves primarily as the reservoir for swallowed food and is the main production site for gastric juice.

Question 42

The antrum or pyloric region (the lower distal 1/3 of the stomach

Answer 42

Provides strong peristalsis to grind and mix food with the gastric juices (which form chyme, a thick, semi liquid mass of partially digested food) and to empty the chyme into the duodenum.