Chapter 23 Module Questions

Describe the source of intestinal gas.

intestinal gas, or flatus, is generated by bacterial activities in the colon when indigestible carbohydrates stimulate bacterial gas production

Identify when most of the CO2 is released during the complete catabolism of glucose.

occurs during the citric acid cycle

List the molecular products from a glucose molecule after glycolysis.

pyruvate, ATP, NADH

Compare metabolism with cellular metabolism.

Metabolism is all chemical reactions in body, whereas cellular metabolism is all chemical reactions within cells

How do the absorptive and post-absorptive states maintain normal blood glucose levels?

during the absorptive state, insulin prevents a large surge in blood glucose after a meal by stimulating the liver to remove glucose from circulation, during the post-absorptive state, blood glucose begins to decrease, triggering the release of glucagon, which stimulates the liver to release glucose into the circulation

Explain the role of glycogen in cellular metabolism.

glycogen is synthesized from excess glucose molecules by the liver and muscle cells, and serves as an intracellular glucose reserve

Describe the role of hydrogen ion channels play in the generation of ATP.

hydrogen ion channels are passageways for the diffusion of hydrogen ions from the inner membrane space of the mitochondria to the matrix. This movement of hydrogen ions powers the production of ATP by ATP synthase.

What molecule forms the common substrate for the citric acid cycle?

2-carbon molecule, CH3COO-, which is attached to coenzyme A to form acetyl-CoA

Explain when glycolysis is important in cellular metabolism.

ATP produced anaerobically through glycolysis is important during peak levels of physical activity, in red blood cells, or when a tissue is temporarily deprived of oxygen

What molecule plays a key reactant role in both ATP production from fatty acids and lipogenesis?

Acetyl-CoA is a reactant molecule in ATP production and in the synthesis of most types of lipids

Define Nutrient pool

All of a cell's organic building blocks

Define beta-oxidation.

Beta-oxidation is fatty acid catabolism that produces molecules acetyl-CoA

Distinguish between catabolism and anabolism.

Catabolism is breakdown of organic material, anabolism is synthesis of new organic material

Why do cell's engage in Catabolism?

Cell's carry out catabolism to release energy for use in cell growth, cell division, and tissue-specific activities

Why do cells make new compounds?

Cells make new compounds to maintain and repair structures, support growth, and build up nutrient reserves

Explain the process of metabolic turnover.

Continual breakdown and synthesis of organic material from nutrient pool

Where are the cytochromes located in a mitochondrion?

Cytochromes are embedded in the inner mitochondrial membrane

Why is digestion important?

Digestion is important because cells throughout the body rely on the organic molecules from the food we eat for energy production and to replenish the intracellular nutrient pool.

Identify the fates of fatty acids.

Fatty acids may becomes a source of energy or a component of triglycerides, glypolipids, phosolipids, prostaglandins, cholesterol, and steroids

Describe the roles of LDL and HDL.

LDLs or VLDLs deliver cholesterol to body tissues, and HDLs absorb unused cholesterol from body tissues, returning it to the liver where it may be packaged into new LDLs or excreted with bile salts in bile

What is the difference between a micelle and a chylomicron?

Micelles are lipid-bile salt complexes (containing fatty acids, glycerol, and monoglyerides) formed in the intestinal lumen. Chylomicrons are lipoproteins formed in intestinal epithelial cells and contain newly synthesized triglycerides, cholesterol, and other lipids surrounded by phosolipids and proteins

Where does nutrient absorption occur?

Most nutrient absorption occurs in the small intestine, primarily in the jejunum.

Most of the absorbed nutrients enter into which blood vessel?

Most nutrient enter into a branch of the hepatic portal vein and are transported to the liver

What two coenzymes transfer hydrogen atoms to the electron transport system?

NAD and FAD

Define absorptive state and post-absorptive state.

The absorptive state, lasting about 4 hours, is the period following a meal, when nutrient absorption is under way. The post-absorptive state, lasting about 12 hours, is the period when nutrient absorption is not under way and the body relies on internal energy reserves to meet demands

Describe the role of CCK release and its effects on proteins.

The arrival of acidic chyme in the duodenum triggers the release of inactive pancreatic proenzymes. Enteropeptidase, released from the duodenum, converts the pancreatic proenzyme trypsinogen into the proteolytic enzyme, trypsin. Trypsin then converts other porenzymes to yield chymotrypsin, carboxypeptidase, and elastase. Each of these enzymes attacks peptide bonds that link specific amino acids while ignoring others. As a results, they break down into a mixture of dipeptides, tripeptides, and amino acids

Briefly describe the citric acid cycle and explain its role.

The citric acid cycle is the reaction sequence that occurs in the matrix of mitochondria. In the process, organic molecules are broken down, carbon dioxide molecules are released, and hydrogen atoms are transferred to coenzymes that deliver them to the electron transport system.

Identify the processes by which the amino groups is removed.

amino acids group is removed by deamination or transamination

Explain why carbohydrates are preferred over proteins and lipids as an energy source.

carbohydrates are preferred energy source because lipids and proteins are more important as structural components of cells and tissues

Define oxidative phosphorylation.

generation of ATP within mitochondrion in a reaction sequence that requires coenzymes and consumes oxygen

When and how do ketone bodies form?

ketone bodies from during the post-absorptive state when lipids and amino acids are broken down in the liver. The increased concentration of acetyl-CoA that results from their breakdown forms ketone bodies. Ketone bodies are not catabolized by liver cells, and they diffuse into the circulation

Define nutrition.

nutrition is the absorption of nutrients from food

What happens to the ammonium ions that are removed from amino acids during deamination.

the ammonium ions combine with carbon dioxide to dorm urea (in the urea cycle), which is ultimately excreted in the urine

What does the liver do with the chylomicrons it receives?

the liver aborbs chylomicrons removes the triglycerides, combines the cholesterol from the chylomicron with recycled cholesterol, and alters the surface proteins. Newly synthesized complexes are released into the bloodstream as LDLs or VLDLs

If vitamins do not provide a source of energy, what is their role in nutrition?

vitamins play an important role in metabolic pathways by serving as coenzymes

Identify the two classes of vitamins.

water-soluble and fat-soluble