Anatomy and Physiology Chapter 18: Nutrition and Metabolism

How does digestion aid in the break down of complex carbohydrates?

Breaks them down to monosaccharides, which are small enough to be absorbed into the blood stream

Carbohydrates

are organic compound and include the sugars and starches

Fats contain more than twice

as much chemical energy as carbohydrates or proteins

Disaccharides

(double sugars) simple carbohydrates, milk sugar, cane sugar, beet sugar, and molasses

Polysaccharides

(many sugars) a complex carbohydrate, such as starch from plant foods and glycogen from meats.

Lactose

(milk sugar) the disaccharide synthesized when the breasts are actively secreting milk.

Monosaccharides

(simple sugar) honey and fruit

Plant carbohydrates that provide fiber:

Hemicellulose, pectin, and lignin

How are fructose and galactose converted into glucose ?

Liver enzymes catalyze the reactions

Use of undigestiable cellulose

Most passes through the alimentary canal largely unchanged. Provides bulk (fiber or roughage) against which the muscular wall of the digestive system, moving along intestinal contents

What do foods containing starch and glycogen have?

Nutrients including valuable vitamins and minerals

Cholesterol

-abundant in liver and egg yolk and, to a lesser extent in whole milk, butter, cheese, meats -foods of plant origin do not contain cholesterol

Saturated Fats

-contain no double bonds between the carbons of their fatty acid molecules -mainly found in foods of animal origin: meat, eggs, milk, and lard -palm and coconut oils -risk factor for cardiovascular disease in excess

Glycogen (glycogenesis)

-excess glucose that is polymerized -liver and muscles store as a glucose reserve -broken down to yield glucose (glycogenolysis) when it is required to supply energy

Monounsaturated Fats

-fatty acid contains one double bond -olive, peanut, and canola oils, are the healthiest

Unsaturated Fats

-fatty acid molecules with double bonds in their carbon chains -seeds, nuts, and plant oils

Triglycerides

-most common dietary lipids are fats -consist of three fatty acid molecules and glycerol molecule -found in plant and animal based foods

Lipids

-organic compounds that include fats, oils, and fat like substances such as phospholipids an cholesterol -supply energy for cellular processes and help build structures, such as cell membranes -provide a variety of physiological functions; fats mainly supply energy

How do cells obtain energy ?

-oxidize fatty acids to obtain energy -neurons: normally, require a continuous supply of glucose for survival, under prolonged starvation, other fuel sources are available for neurons

Carbohydrate Requirement

-provides primary source of fuel for cellular processes -varies with individual energy requirements -the physically active require more than the sedentary -intake of at least 125-175 grams daily to avoid protein breakdown and metabolic disorders from excess fat use -200-300 grams daily is average

Hydrolysis

-triglyceride molecule must undergo before releasing energy -when digestion breaks triglycerides down into fatty acids and glycerol -after absorption products are carried by the lymph to the blood, then on to tissues

What does the body do with excess glucose ?

Reacts to form fat (lipogenesis), which is stored in adipose tissue.

What do cells use carbohydrates for?

Starting materials for synthesizing such vital biochemicals as the 5-carbon sugars ribose and deoxyribose

ribose and deoxyribose

Sugars required for the production of the nucleic acids RNA and DNA.

Monosaccharides absorbed from the digestive tract

fructose, galactose, and glucose

Cellulose

is a complex carbohydrate abundant in our food it provides the crunch to celery and the crispness in lettuce.

How is glucose used in cellular fuel

is it oxidized in glycolysis

A temporary decrease in glucose supply..

may seriously impair nervous system function.

Gluconeogenesis

When foods do not provide an adequate supply of carbohydrates, the liver may convert some noncarbohydrates, such as amino acids from proteins or glycerol from fats, into glucose

Beta oxidation

When the resulting fatty acid portions can form molecules of acetyl coenzyme A

Lipids in foods are:

phospholipids, cholesterol, and fats (triglycerides)