Digestion and Nutrition

Chapter 30 (M)

Food and Nutrients

Food Any substance, either raw or processed which is meant for human consumption

Nutrients The components of food that the body can use for growth, repair and energy

How Nutrients are Obtained

Heterotrophs get nutrients in various ways

Types of Nutrients

Carbohydrates Proteins Fats Vitamins Minerals Water

Food as Fuel Carbohydrates, fats and proteins are

all used to generate ATP Fats9 Calories/gm, Proteins and

Carbs 4Calories/gm 1 Calorie (kilocalorie)= 1000 calories Basic Calorie need 2200 for female

teens, 2500 males

Essential nutrients Must be ingested, cell can’t construct

theseEssential Fatty Acids Linoleic AcidEssential Amino Acids 8 AAVitamins water soluble (can be

excreted) and fat soluble( excess might cause damages), reqd for enzyme function

Minerals reqd, but large amts can cause damage

Nutrition and a Balanced Diet Balanced Diet provides nutrients in

adequate amounts and enough energy to maintain a healthful weight

Balancing your dietFood labelsFood guide pyramid

The Food Guide Pyramid

The Food Guide Pyramid Number of calories depends on:

Age Sex Size Whether or not you are a pregnant or breastfeeding woman Whether you have a chronic illness

The National Academy of Sciences recommends the following calorie categories: 1,600 calories - Many sedentary women and some older adults 2,200 calories - Children, teenage girls, active women and

many sedentary men. Women who are pregnant may need around 500 calories more

per day and an additional 300 calories for breast-feeding 2,800 calories - Teenage boys, active men and very active

women The Food Guide Pyramid can be extremely useful - whether

you want to gain weight, lose weight or maintain your weight. Eating a healthy diet is a little easier if you base your choices on the Food Pyramid.

MyPyramid USDA's newest food pyramid guide

 Encourages consumers to make healthier food choices

To get regular exercise  Food groups are arranged in vertically

bands, instead of horizontal ones Band width indicates portion size The wider the band, the more food from

that group should be eaten.

The Digestive System

Converts food into small molecules that can be used by all cells of the body

Food is processed in four phases by the digestive system

Stages of Food Processing

1. Ingestion: eating or drinking2. Digestion : Breaking food into

smaller molecules• Mechanical • Chemical (Enzymes)

3. Absorption: nutrient molecules enter blood, the circulatory system transports it through out the body

4. Elimination: undigested material passes out of the body

The Digestive System Functions like a series of tube like

organs which pass through the body from the mouth to the anus Alimentary Canal

Alimentary Canal can be about 30’ long

Accessory organs Pancreas, Liver, Gallbladder secrete enzymes that are released into the food tube

Digestion in the Mouth

It all begins in the mouth . . .

Teeth, tongueSalivary glands

MucusAmylase

Only carbohydrates are digested here

SWALLOWING AND PERISTALSIS

GLOTTIS AND EPIGLOTTIS

Peristalsis

Rhythmic muscular contractions propel a bolus of food

The human digestive system

Digestion in the Stomach Muscular organ Acts as a

reservoir where food is prepared for digestion in the SI

Produces Gastric Juices

Stomach Functions1. Food Storage2. Mechanical Digestion3. Chemical DigestionSecretions:1. Mucus2. EnzymePepsinogen3. HCL

CHYME semi-fluid food mixture leaves.

Protection from Self-Digestion

Protective liningMain enzyme -Pepsin is inactive Pepsinogen when secreted

Digestion in the Stomach Pepsinogen Comes in contact with

HCl Pepsin Pepsin converts proteins into

peptones Acidity of Gastric juices kills some

bacteria that enters with food Gastric Juices stimulated by

psychological and chemical means Peristaltic process of moving chyme into

the SI takes place for 6hrs

Small Intestine

Digestion in the Small Intestine Main stage of Digestion As chyme enters the SI secretes juices that

are alkaline and neutralizes the acidity SI maltase,lactase,sucrase breaks

disaccharides Liver secretes bile emulsifies fats Dipeptidases dipeptides into AAs Pancreas

Trypsin & Chymotrypsin break down proteins

Amylase converts starch into maltoseLipase breaks fats

Process is complete in about 4 hrs

PancreasSecretes HormonesSodium bicarbonateDigestive enzymes

LipaseTrypsinogenAmylase

Secretes Blood clotting

enzymesStores glycogenBile

Stored in gall bladder

Emulsifies fat

Liver

The structure of the Small Intestine

1. Anatomy:2. Functions

a. Reclaim waterb. Synthesis of vitamins by E. coli

FecesRectumAnus

DiarrheaConstipation

LARGE INTESTINE = COLON

Can you name the parts and tell what they do?