Biochem Ch 14 Digestion

Hydrolysis of the ____ bonds in triacylglycerols yields products including ____

1. ester 2. fatty acids

Hydrolysis of the _____ bonds of carbohydrates yields _____

1. glycosidic 2. monosaccharides

Order of digestive system

1. ingestion of food into the body 2. the physical and chemical breakdown of food into small molecules 3. the absorption of small molecules derived from food by cells 4. the elimination of waste materials from the body

Carbohydrate digestion begins in the_____ with the enzyme _____

1. mouth 2. salivary amylase

Hydrolysis of the ____ bonds of proteins produces ____

1. peptide 2. amino acids

Fat digestion begins in the ______ with the enzyme _____

1. small intestine 2. pancreatic lipase

Nucleic acid digestion begins in the _____ with the enzyme ______

1. small intestine 2. pancreatic nuclease

Protein digestion begins in the ___ with the enzyme ____

1. stomach 2. pepsin

The low pH in stomach is maintained by the

ATP dependent H+ pump

Micelles are important for lipid absorption across the plasma membrae, but lipids are assembled into ______ for transport through the lymph system

Chylomicron

What are the three stages of turning food into energy?

Digestion (from macromolecules in food into small molecules) Processing of the small moleclues into key molecules in metabolisms (ex: acetyl-CoA) Citric acid cycle and oxidative phosphorylation (production of ATP, CO2, H2O)

Beneficial role of lipids in the body?

Lipids support the function of cell membranes Lipids provide insulation under the skin

Dietary fat is primarily transported from the gut to the _____ then to ______ where they are distributed to the ______

Lymph system Blood Tissues

The pancreas releases ______ to neutralize the acid produced in the stomach

NaHCO3

Pancreas as both endocrine (secretion to blood) and exocrine (secretion to extracellular lumen) organ has important roles in digestion and energy homeostasis. Explain.

Pancreas secretes a host of digestive enzymes (exocrine) to aid in digestion, also insulin (endocrine) to control glucose intake

Why does a person who has achlorydria have difficulty digesting proteins?

Pepsinogen cannot be converted to pepsin in the absence of hydrochloric acid

What is caloric homeostasis?

The condition when energy expenditure of an organism is equal to the energy intake

Why must food molecules be chemically broken down into smaller component molecules by the body?

They need to be broken down into monomers to build new polymers that the body can use They need to be broken down into molecules small enough to cross the cell membrane

Choose the true statements about protein digestion and hydrolysis. a. In the small intestine chymotrypsin attacks peptide bonds b. Enzymes present in saliva initiate the process of protein digestion c. Free amino acids are passively absorbed through the intestinal wall d. Pepsin causes the hydrolysis of some of the peptide bonds in proteins e. pancreatic juices are more acidic than gastric juices

a. In the small intestine chymotrypsin attacks peptide bonds d. Pepsin causes the hydrolysis of some of the peptide bonds in proteins

Starch is a common carbohydrate that is found in vegetables and grains. Which statement describes the structure of starch? a. Starch is a polymer of glucose b. Starch is a polymer of cellulose c. Starch is a monomer of glucose d. Starch is a polymer of mannose

a. Starch is a polymer of glucose

Choose all sources of free amino acids in the human body a. dietary protein b. gluconeogenesis c. lipogenesis d. protein turnover e. biosynthesis of amino acids

a. dietary protein d. protein turnover e. biosynthesis of amino acids

All of the following are pancreatic proteases except a. pepsin b. chymotrypsin c. trypsin d. carboxypeptidase e. elastase

a. pepsin

What mechanism prevents pepsin from digesting the stomach's own cells? a. pepsin only becomes active after HCl exposes the active site b. the acidic environment of the stomach denatures pepsin c. bicarbonate solution from the pancreas protects the stomach lining d. stomach cells are not affected because they produce anti-pepsin

a. pepsin only becomes active after HCl exposes the active site

An orally taken proton-pump inhibitor (like Omeprazole) would likely have the following side effect: a. protein not being digested b. nucleic acid hydrolysis c. loss of ATP production d. pepsin activation e. decreasing levels of bile salts

a. protein not being digested

the gall bladder secretes

bile salts (to facilitate digestion of fats)

The pancreas releases _____ to buffer the pH of the stomach juices a. HCl b. a strong base to counter the strong acid c. NaHCO3 d. pepsin e. ATPase-activating protein

c. NaHCO3

ATP is produced from

complete oxidation

Enteropeptidase converts

inactive trypsinogen into active trypsin

the pancreas secretes

sodium bicarbonate (NaHCO3) (to neutralize the acid)

Chylomicrons

water-soluble lipoproteins synthesized from phospholipids in epithelial cells and transported to the lymphatic system

Had cholecystechtomy and removal of gallbladder. Limit intake of?

Cheese

How do microvilli impact nutrient absorption in the small intestine?

Microvilli provide a large surface area which allows for more efficient nutrient absorption within the small intestine

Secretin stimulates the release of

sodium bicarbonate from the pancreas

The limit dextrin is material not digested by amylase due to the ______ bond

a-1,6-glycosidic

Dietary proteins must be denatured for efficient digestion. Why?

By destroying the three-dimensional structures of the proteins, they become easily accessible and thus efficient substrates for the digestive enzymes

Match process Digestive tract Cell cytoplasm Mitochondrion with location it occurs: Major catabolic reactions Oxidative phosphoylation Nutrient absorption

Digestive tract - nutrient absorption Cell cytoplasm - major catabolic reactions Mitochondrion - oxidative phosphorylation

What properties of lipids make their digestion more complicated than that of carbohydrates and proteins? How are lipids made accessible for digestion?

Lipids are hydrophobic and do not dissolve in water, rather they form emulsions (lipid droplets dispersed in water). Bile salts from gall bladder insert into the emulsion and make the lipids in the droplet more accessible by lipase, thus readily digested. The fatty acids resulted are carried into the intestine cell membrane by micelles.

Why is digestion required for fuel metabolism even though no useful energy is harnessed in the process?

Through digestion macromolecules (proteins, lipids, complex carbs) in food can be turned into small molecules (amino acids, fatty acids, simple carbs) that can be taken up by cells of the body

A(n) ______ is an inactive enzyme that must be partially digested to attain full enzymatic activity

Zymogen or proenzyme

Why are most digestive enzymes produced as zymogens?

Zymogens are not active thus they will not cause damage to the tissues from which they are secreted.

What is a zymogen?

a protein that is inactive form of an enzyme an inactive substance that is converted into an enzyme when activated by another enzyme

Which of the following pancreatic zymogens are directly activated by trypsin? a. prolipase b. procarboxypeptidase c. proelastase d. chymotrypsinogen

a, b, c, and d

Which of the following statements is true regarding the digestion of starch and cellulose by humans? a. Cellulose contains alpha linkages, which humans lack the enzymes required to hydrolyze b. Humans lack the enzymes required to hydrolyze the beta linkages in cellulose c. Humans have the enzymes required to hydrolyze the beta linkages in starch d. Humans are able to digest both starch and cellulose

b. Humans lack the enzymes required to hydrolyze the beta linkages in cellulose

The result of lipase activity in digestion is a. phospholipid head group hydrolysis b. monoacylglycerol and two free fatty acids c. bile-salt formation d. hydrolysis of membrane proteins e. emulsion formation

b. monoacylglycerol and two free fatty acids

Select the chemical that converts procarboxypeptidase into carboxypeptidase a. insuin b. trypsin c. secretin d. pepsin

b. trypsin

ribonuclease function

breaks down RNA into nucleotides

pancreatic amylase function

breaks down starch into oligosaccharides and disaccharides

pancreatic lipase function

breaks down triglycerides into fatty acids and monoglycerides

Complex carbohydrates are absorbed a. as acetyl CoA b. as starch or glycogen c. as they are converted to glucose and simple sugars d. as short four glucose residues e. after the digestion of alpha-1,6 bonds by amylase

c. as they are converted to glucose and simple sugars

Which of the following is released by the upper intestine that increases zymogen secretion? a. secritin b. pepsin c. cholecystokinin d. bile salts e. enteropeptidase

c. cholecystokinin

Whic of the enzymes are used in the activation of trypsinogen? a. chymotrypsin b. fibrin c. enteropeptidase (enterokinase) d. trypsin

c. enteropeptidase (enterokinase) d. trypsin

Which of the following lipids must be obtained in the diet? a. endogenous glycogen b. endogenous sterols c. essential fatty acids d. essential polysaccharides

c. essential fatty acids

Pepsin requires _____ to become active a. low pH b. partial denaturation of protein c. zymogen activation d. all of the above

d. all of the above

Which of the following enzymes activates trypsin? a. zymogenase b. pepsin c. trypsinase d. enteropeptidase e. carboxypeptidase

d. enteropeptidase

Which of the following statements describes the role of the liver in digestion? a. produces insulin, which regulates blood glucose levels b. produces digestive enzymes that aid carbohydrate digestion c. produces gastric juice, which aids digestion in the stomach d. produces bile, which aids lipid digestion

d. produces bile, which aids lipid digestion

the acidic environment of the stomach (pH ~2)

denatures proteins

Glucose transport takes place by a. active transport using the sodium gradient b. active transport using ATP as the energy source c. passive transport using the glucose gradient d. secondary active transport using the potassium gradient e. secondary active transport using the sodium glucose cotransporter

e. secondary active transport using the sodium glucose cotransporter

Cholecystokinin (CCK) stimulates the secretion

of bile salts from the gall bladder

The acid environment of the stomach denatures proteins

rendering them more susceptible to proteolytic digestion in the small intestine