Chapter 5: Absorption and Transport

Which statements correctly describe the principles of water absorption in the body? -Absorption of water is closely associated with the absorption of sodium. -The small intestine is responsible for absorbing most of the water in the body. -The largest percentage of water absorbed in the body comes from fluid that has been ingested. -Most of the water remaining when chyme enters the large intestine is absorbed in the first half of the colon. -Water moves in and out of the cell from an area of higher to lower solute concentration across a semipermeable membrane.

-Absorption of water is closely associated with the absorption of sodium. -The small intestine is responsible for absorbing most of the water in the body. -Most of the water remaining when chyme enters the large intestine is absorbed in the first half of the colon.

Hepatic Portal Circulation

-All blood leaving the stomach, intestines, pancreas, and spleen passes through the hepatic portal vein to the liver before it enters the general circulation. -This blood is partially deoxygenated and rich in newly absorbed nutrients from digested food. -Nutrients undergo further processing by liver cells before they are taken to other cells and tissues in the body. -The liver metabolizes carbohydrates, lipids, and proteins into biologically useful substances. -The segment of circulation from the intestines to the liver is called the portal circulation.

Anabolic Protein synthesis

-Amino acids are joined through peptide bonds to form functional and structural proteins -Process occurs when an increase in protein synthesis is required, in time of growth or tissue repair -Glucagon, growth hormones, gonadotropins, and thyroxine all stimulate the synthesis or protein; steroid hormones initiate gene expression and protein synthesis.

Catabolic Glycolysis

-Breakdown of glucose to yield pyruvate and ATP -this pathway is used by cells to extract energy from sugars, mainly glucose, in the form of ATP -Insulin is released in response to high blood glucose levels -Insulin facilitates the entry of glucose into the cell and increases the production of the critical glycolysis enzymes -Occurs whenever energy is require in the body

Protein degradation

-Breakdown of protein to yield single amino acids -Cortisol, a stress hormone, breaks down muscle protein, which leads to an increase of glucose in the blood -Occurs when the body has immediate energy needs, and liver stores cannot meet those needs due to a limited supply of amino acids -Protein is broken down into amino acids and nitrogen is removed

Catabolic Lipolysis

-Breakdown of triglycerides into glycerol molecules and individual fatty acids for energy use -Insulin regulates adipose tissue lipolysis through the control of the activity of hormone-sensitive lipase -Glucagon stimulates fat breakdown, helping to raise blood glucose levels -Cortisol breaks down carbohydrates and fats for energy -Occurs when the body runs out of energy sources during fasting or strenuous physical exercise

Lacteals

-Chylomicrons leave the basement membrane and enter the lacteals for transfer to the lymphatic circulation and eventually the blood circulation

Vascular system

-Consists of veins, arteries, and a network of small capillaries that absorb nutrients in the small intestine -Supplies the body with nutrients, oxygen, and other vital substances -Most of the products of digestion are water-soluble, meaning they can be absorbed directly from the small intestine into the blood (venous system).

How are the structures in the small intestine involved in the absorption of nutrients?

-Epithelial cells of the villi help transport nutrients into the blood. -Structures increase the total surface area through which nutrients can be absorbed. -A network of small blood vessels located on each villus takes up nutrients into the blood.

Which substances are transported through the lymphatic system? -Proteins -Fatty acids -Cholesterol -Chylomicrons -Carbohydrates

-Fatty acids -Cholesterol -Chylomicrons

Anabolic Lipogenesis

-Fatty acids are formed from acetylcoenzyme A -The process takes place in the cytoplasm of fat and liver cells when macronutrient levels exceed energy needs -Fatty acids are combined with glycerol to form triglycerides for storage in adipose tissue -Insulin stimulates lipogenesis

Anabolic Gluconeogenesis

-Glucose is formed from noncarbohydrate precursors derived from protein and fat -Process occurs when the intake of glucose-containing foods is insufficient and the body must make glucose for energy from other sources. -Glucagon and glucocorticoids stimulate gluconeogenesis

Anabolic Glycogenesis

-Glycogen is formed from glucose -Glycogen is stored in the liver and skeletal muscle cells for future use -The process is prompted by glucose levels that exceed immediate energy needs. -Insulin promotes the conversion of glucose to glycogen

Catabolic Glycogenolysis

-Hydrolysis of glycogen to glucose -Glycogen is produced by the a cells of the pancreas to stimulate the breakdown of glycogen in the liver into glucose -When the body requires maintenance of blood glucose levels, such as during fasting

Place the structures in the order through which water-soluble nutrients pass after they are absorbed.

-Intestinal capillaries -Hepatic portal vein -Liver

Which statements correctly describe the function of the hepatic portal vein in portal circulation? -It bypasses the general venous circulation. -It provides the liver with nutrient-rich blood from digested food. -It provides a route to the lymphatic system before nutrients enter the general circulation. -It allows oxygenated blood to pass through the liver before it enters the general circulation. -It allows the liver to perform many vital metabolic functions such as transforming nutrients into substances that can be readily utilized in the body.

-It bypasses the general venous circulation. -It provides the liver with nutrient-rich blood from digested food. -It allows the liver to perform many vital metabolic functions such as transforming nutrients into substances that can be readily utilized in the body.

Which statements correctly describe facilitated diffusion? -It does not require a carrier. -It is a passive transport method. -It requires the aid of a protein in the membrane. -It does not require a protein carrier to move small particles across the mucosal cell wall. -It involves movement from a higher nutrient concentration to a lower concentration.

-It is a passive transport method. -It requires the aid of a protein in the membrane. -It involves movement from a higher nutrient concentration to a lower concentration.

Microvilli

-Known as brush border cells -extremely small hair-like projections -greatly increase the total absorbing surface area of the small intestine

Hepatocytes

-Liver cells perform many vital metabolic processes. -They produce lipids such as cholesterol, phospholipids, and lipoproteins. -Their function is to regulate blood levels of substances such as cholesterol and glucose, helping to maintain body homeostasis.

Villi

-Small, finger-like projections cover the mucosal surface -Increasing the area of exposed surface

Put the steps in the process of pinocytosis in chronological order.

-The droplet binds to the cell membrane. -A pocket is formed in the cell membrane. -A vesicle is formed, trapping fluid inside the cell. -The droplet of fluid is transported through the cell.

When glycogen reserves are full, excess energy from carbohydrates is stored as _____ in the _______ __________

-fat -adipose tissue

Through the process of digestion, fats are broken down into _____________ and ____________.

-glycerides - fatty acids

Excess carbohydrates are stored as ______ in the ______ and _________

-glycogen -liver -muscles

Primary anabolic pathways in the body include:

-glycogenesis -lipogenesis -protein synthesis -gluconeogenesis

Excess lipids are stored as ____________ in the _________ _________

-triglycerides -adipose tissue

The total length of the small intestine is approximately

22 feet.

Glucose uses ATP to move into the cell.

Active transport

Which type of transport occurs when particles move against their concentration gradient?

Active transport

Which chemical compounds represent the end products of the electron transport chain?

Adenosine triphosphate (ATP) and water

Which statement describes the process of anabolism?

Anabolism refers to the formation of complete molecules from smaller building blocks.

In what part of the gastrointestinal tract is chyme formed?

Antrum

Catabolism

Breaking down of molecules

Which description defines glycogenolysis, a metabolic function of the liver?

Breaking down stored glycogen into individual glucose units

Which condition is a food allergy that can affect the normal functioning of the gastrointestinal tract?

Celiac disease

Which statement describes the absorption of fat into the lymphatic system?

Chylomicrons leave the basement membrane of the enterocyte and enter the lacteals.

In which section of the gastrointestinal tract does the absorption of water take place?

Colon

Where does intestinal gas form in the gastrointestinal tract?

Colon

Amino acids are transferred into epithelial cells via special proteins.

Facilitated diffusion

When digestion is complete, to which product are carbohydrates reduced in otder to be absorbed into the body?

Galactose

Which genetic disease affects approximately 1 in every 30,000 ti 60,000 live births and can cause fatal brain and liver damage it not treated?

Galactosemia

Which genetic disease causes complications for patients despite rigorous treatment?

Galactosemia

Which hormone is released to increase the catabolism of glycogen?

Glucagon

Formation of glucose from noncarbohydrate sources

Gluconeogenesis

Which statement differentiates gluconeogenesis from glycogenesis?

Gluconeogenesis uses noncarbohydrate sources, whereas glycogenesis uses glucose molecules.

Formation of glycogen from molecules of glucose

Glycogenesis

Release of glucose from glycogen

Glycogenolysis

Catabolsim of glucose to release ATP

Glycolysis

Where are the lacteals found?

In the villi of the small intestine

Which network of nerves, extending from the esophagus to the anus, is located in the gastrointestinal (GI) wall?

Intramural nerve plexus

A deficiency of which substance causes an intolerance to milk and dairy products?

Lactase

Which statement correctly describes the transport of fat-soluble nutrients?

Lipids are absorbed through lacteals in the villi walls and released directly into the lymphatic system.

Formation of fatty acids from acetyl-CoA

Lipogenesis

Breakdown of lipids into fatty acids

Lipolysis

Where does the breakdown of fat being, and which enzyme is involved in the breakdown?

Mouth, lipase

What is the function of the mucous glands that line the esophagus?

Moving food toward the stomach

Which gastrointestinal secretion lubricates and protects the tissues that line the gastrointestinal (GI) tract and helps moisten the food mass?

Mucus

Water moves into the blood.

Osmosis

Which term refers to the movement of intestinal muscles that slowly pushes the food mass forward, sometimes with long, sweeping waves over the entire length of the intestine?

Peristaltic waves

In which absorption process in the small intestine does the cell engulf large molecules in order to absorb them?

Pinocytosis

Breakdown of protein into amino acids

Protein degradation

Which anabolic process utilizes steroid hormones?

Protein synthesis

In response to a low pH in the duodenum, which hormone stimulates the pancreatic release of bicarbonate to increase the pH to an alkaline environment?

Secretin

Which small intestinal movement results in the progressive chipping of a food mass into soft lumps, mixing it with gastrointestinal secretions?

Segmentation rings

Fatty acids enter the cell

Simple diffusion

Nutrients that do not need the help of a specific protein channel to move across a mucosal cell wall are transferred by which process?

Simple diffusion

Fatty materials have to pass through the lymphs before entering the bloodstream for which reason?

They are not water soluble.

Catabolic reactions release energy in the form of

adenosine triphosphate (ATP)

Through the process of digestion, protein is hydrolyzed into individual

amino acids

This rate of energy consumption while at rest is called the___________ ___________ __________ and is the energy required to fuel vital body functions.

basal metabolic rate

Through the process of digestion, carbohydrates are broken down into

glucose, fructose, and galactose.

Through the process of digestion, food particles are broken down into

monomers

Anabolism

process by which energy is used to transform smaller molecules into larger, more complex molecules that make up the body's cells.

The electron transport chain is the stage of catabolism that

yields the most energy; electrons are transferred from high-energy molecules (generated by the TCA cycle) to release ATP and water.