bio 156 chapter 5 powerpoint

8/14/2019 BIO 156 Chapter 5 Powerpoint

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BIO 156

Chapter 5


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An Introduction to Nutrition


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A healthy dietconsists of:

Breads, cereals,

rice, and pasta.

Plenty of fruitsand vegetables

Meat and milk

products. but in

lesser amounts.

Minimal fat


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Macronutrients are needed in large quantity and include water,

carbohydrates, lipids, and proteins.

Water

is involved in many chemical reactions in the body.

helps maintain body temperature and a constant level ofnutrients and wastes in body fluids.

Carbohydrates

are a major source energy

belong to three groups:

monosaccharides, disaccharides, and

polysaccharides


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Lipids

are a source of energy but also play a structural role

Triglycerides (fats and oil) provide energy and

insulation. Phospholipids and steroids are part of the plasma

membranes of cells.

Triglycerides with many double bonds in their fatty acid

side chains (the polyunsaturated fatty acids) lower onesrisk of developing atherosclerosis.

Triglycerides high in saturated fatty acids, found inanimal fats, tend to increase atherosclerosis.


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Amino Acids and Protein. Proteins in food are broken down to amino acids which

are used to make proteins such as enzymes and

hormones.

Amino acids the body cannot synthesize are known asessential amino acids.

Amino acids the body can synthesize are known as

nonessential amino acids.


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Choices


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The Digestive System


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Physical breakdown of food occurs in the mouth

Chewing breaks food into smaller pieces

Saliva performs at least five functions:

liquefies the food

kills or neutralizes some bacteria dissolves substances so they can be tasted

begins to break down starch molecules

cleanses the teeth


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Teeth must be kept clean to prevent plaque and cavities.

Each tooth consists of:

enamelthe hard outer layer

dentina softer layer

pulpthe inner region filled with nerves and blood

vessels

Bacteria that live on the teeth secrete a sticky, acidic

material called plaque.


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The tongue plays a key role in swallowing.

The tongue pushes food to the back of the oral

cavity into the pharynx.

The tongue contains taste receptors on its uppersurface.


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The epiglottis keeps

food from entering the

trachea.

Food entering the

pharynx triggersthe swallowing

reflex, which

forces the food

into the

esophagus.


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The esophagus transports food to the stomach via

peristalsis


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The stomach stores food, releasing it into the small

intestine in spurts.

Gastric glands in the stomach produce

hydrochloric acid

Pepsinogen

The food is turned into chyme before it is

released.


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Chyme leaves the stomach and enters the small intestine.

The stomach contents are emptied in 26 hours. As chyme and protein leave the stomach, gastric gland

secretion declines.

The small intestine serves as a site of food digestion andabsorption.

The small intestine consists of three parts:

the duodenum, jejunum, and ileum.


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Digestion in the small intestine requires enzymes from

two sources.

the lining of the intestine

the pancreas

produces enzymes and sodium bicarbonate essential

for the digestion.

The digestive enzymes of the pancreas flow into the

duodenum.


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The liver carries out hundreds of important functions.

The liver stores minerals, vitamins, glucose, and lipids

The liver produces an emulsifying agent, bile, which

plays a key role in the digestion of fat.

Bile is transported to the gallbladderuntil it is needed


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The intestinal epithelium, the

lining of the intestine, is

specially modified for

absorption.

The lining of the small

intestine is folded.

On the surfaces of the

folds are fingerlike

projections known as

villi and microvilli.

The microvilli are thetiny hairlike projections

found on the villi

themselves.


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The large intestine is the site of water resorption.

It consists of four regions:

the cecum, appendix, colon, and rectum

It also absorbs sodium and potassium as well asvitamins produced by intestinal bacteria.

It transports the waste, or feces, to the outside of the

body.


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Choices


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bio 156 chapter 5 powerpoint

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