NUTRITION AND THE DIGESTIVE SYSTEM

- NUTRITION: group of processes by which the

organism gets and transforms the nutrients that

its cells need.

- NUTRIENTS are chemicals present in the

food that the cells need for:

➢Energy: ENERGETIC NUTRIENTS

➢Building and repairing structures (growth, cell renovation): BODY

BUILDING NUTRIENTS

➢Regulating the chemical reactions in the cell (metabolism):

PROTECTIVE or REGULATORY NUTRIENTS

NUTRIENTS + O

2

ENERGY + CO

2

+ H

2O

+ UREA(excretory chemicals)

NUTRIENTS

FOOD

Digestive System

Circulatory System

O2

O2

AIR

CO2

CO2

Circulatory System

(ALVEOLI: gas exchange)

Respiratory System

UREA

URINE

URINE

(KIDNEY)

Circulatory System

Excretory System

CELL

Do you agree with it? Why?

Have you ever heard this statement?

Types of Nutrients:

1.- Macronutrients (=needed in larger qualities)

1.1.- Carbohydrates:

- mainly ENERGETIC (4kcal/g)

- simple carbohydrates or sugars like sucrose, fructose and glucose

are quickly digested and absorbed: first source of energy for the cells

- complex carbohydrates like starch or glycogen need a longer

digestion: energy store for the cells

- cellulose (fiber) is a complex carbohydrate. It is not energetic

BUT regulatory

- we can get them from fruits and vegetables (sugars), bread, cereals,

rice and pasta (complex)

1.2.- Lipids:

- They have the three functions of nutrients:

- Fats are the most abundant lipids. They are ENERGETIC nutrients

(store energy in the adipose tissue) (9kcal/g)

- Other lipids (eg. cholesterol, phospholipids) are part of the cell

membranes, so they are BODY-BUILDING nutrients (=for growth and

repair).

- Some lipids are vitamins (A, D, E, K) or hormones (steroids), so they

have a REGULATORY function.

- We can get them from oils, butter, cheese...

1.3.- Proteins:

- They are basically BODY-BUILDING nutrients, but they also have some

REGULATORY functions. When the cell has no carbohydrates or lipids, they

can be used to get energy (4kcal/g).

- We get proteins from meat, fish, eggs...

1.4.- Water:

- It is the most abundant component in our body.

- It has REGULATORY functions:

- refrigerates the body (regulates body temperature)

- transports substances

- helps to remove wastes

- is where metabolism happens

- We get water from liquid foods (water, juices, milk), fruits and vegetables...

2.- Micronutrients (=needed in small amounts)

2.1.- Minerals:

- Some have a BODY-BUILDING function: Ca and P form the bones.

- Others have a REGULATORY function:

- Fe forms the hemoglobin.

- Ca, Fe, Mg are needed for several metabolic

reactions to happen

- oligo-elements are minerals that are present in

less than 0.1% in the body, but are essential for its

normal function: Fe, F, I.

- We get them mainly from fruits and vegetables.

2.2.- Vitamins:

- They may be lipids or proteins.

- They have a REGULATORY function.

- Only small quantities are needed in the organism,

but we cannot produce them, so we have to get them

in the diet.

- Some of them are water-soluble: group B and C.

(excess is easily eliminated through urine or sweat)

- Others are fat-soluble: A, D, E, K

(excess accumulates in the liver and may have

damaging effects)

- We get vitamins from fruit and vegetables.

Nutrients (mainly carbohydrates and lipids) are the fuel the cell uses to

get energy in the Cellular Respiration that happens in mitochondria.

The units we use to measure ENERGY are:

- calorie (cal): amount of energy needed to increase 1ºC the temperature of

1g of water

1Cal=1kcal=1000cal

- joule (j): unit in the IS

1J=0,24cal

1cal=4,18j

Remember which are the most energetic nutrients?

Which of the following meals is more energetic? Does it mean it is healthier?

The energy that one person needs a day (Daily Energetic Requirements)

depends on:

The Basal Metabolic Rate (BMR) is the amount of energy that one

person needs while completely at rest. It depends on the person's age,

sex, height and weight.

Why do we need energy while we are resting?

The Physical Activities that the person does.

So we can calculate the energy we need in a day:

DER = BMR+PA

FOOD PYRAMID:

What are GMO?Genetically Modified Organisms are organisms whose genes have been

altered by using genetic engineering techniques in order to get some

characteristic.

Genetically Modified Foods are plants or animals that have incorporated a

gene from a different species, to get a new feature: tastier and bigger

tomatoes, decaffeinated coffee grains, plague-resistant corn, drought-

tolerant crops, etc.

These genetically modified tomatoes contain anti-oxidants that help to prevent cancer.

http://www.dailymail.co.uk/sciencetech/article-1080695/Purple-super-tomato-fight-cancer.html

Golden Rice is a transgenic rice enriched with vitamin A to help prevent blindness caused by a deficiency in this vitamin.

A BALANCED DIET is the diet that allows a person to keep

healthy and do the physical activities he/she usually does.

To achieve this we should choose foods in the right amount

and of the right group.

Diet must provide the calories and nutrients that the person needs, especially the essential nutrients (proteins, minerals, vitamins).

Origin of calories: 55-60% of the calories must come from carbohydrates, 30-35% from fats, and only 5-10-5 from proteins.

Animal proteins must be less than 40%

More plant oils and oily fish than animal fats (rich in cholesterol)

Enough fiber to regulate the function of the intestine; enough water and minerals.

The diet must be as varied and enjoyable as possible.

NUTRIENTS + O

2

ENERGY + CO

2

+ H

2O

+ UREA(excretory chemicals)

NUTRIENTS

FOOD

Digestive System

Circulatory System

O2

O2

AIR

CO2

CO2

Circulatory System

(ALVEOLI: gas exchange)

Respiratory System

UREA

URINE

URINE

(KIDNEY)

Circulatory System

Excretory System

CELL

DIGESTIVESYSTEM

STAGES OF DIGESTION:

- INGESTION

- DIGESTION

- ABSORPTION

- ASSIMILATION

- DEFECATION

DIGESTION means breaking down the large, insoluble food molecules into small

soluble molecules (nutrients) that can be absorbed into the bloodstream and used

by the cells.

Digestion can be:

MECHANICAL: breaking down food into smaller pieces through physical

processes (chewing in the mouth, churning in the stomach, etc)

CHEMICAL: involves the use of special chemicals called ENZYMES that speed

up the digestion of large molecules into smaller ones.

MECHANICAL DIGESTION:

PERISTALSIS: contraction of the digestive tract's muscular walls (oesophagus, stomach, small intestine)

CHEWING:

CHEMICAL DIGESTION:

ENZYMES are chemicals present in the digestive juices, that break down molecules

into smaller ones

ANATOMY OF THE DIGESTIVE SYSTEM:

- DIGESTIVE TRACT: a long tube (aprox. 9 m long) that goes from the MOUTH to

the ANUS (Mouth-Pharynx-Oesophagus-Stomach-Small Intestine-Large Intestine)

- GLANDS: that produce digestive juices (containing digestive enzymes and other

chemicals) and pour them into the different organs of the digestive tract (Salivary

Glands, Gastric Glands, Pancreas, Liver, Intestinal Glands)

- Some sphincters or valves regulate the movement of the digesting food from one

organ to the next one.

ANATOMY OF DIGESTIVE SYSTEM

STRUCTURE OF THE DIGESTIVE SYSTEM

ANATOMY OF DIGESTIVE SYSTEM

DIGESTION STARTS IN THE MOUTH:

- Mechanical Digestion: Chewing

- Chemical Digestion: Salivary Glands (Parotids,

Sublingual, Submaxilary) produce SALIVA, that

contains:

- AMYLASE: digests carbohydrates

- Mucus

- Lysozyme

- Deglutition: bolus goes down from mouth to the

pharynx and oesophagus. This movement is helped by

gravity and peristalsis.

DIGESTION IN THE STOMACH:

- Mechanical Digestion: Peristalsis

- Chemical Digestion: Gastric Glands in the inner walls produce GASTRIC

JUICE, that contains:

- PEPSIN: an enzyme that digests proteins

- Hydrochloric Acid (HCl) needed for the pepsin to work

The bolus enters the stomach through the cardia, and

leaves it through the pylorus, that communicates with

the small intestine (duodenum)

DIGESTION IN THE SMALL INTESTINE:

- Mechanical Digestion: Peristalsis

- Chemical Digestion: 3 digestive juices act in the small intestine:

- The PANCREAS produces PANCREATIC JUICE and pours it into the

duodenum when the chyme enters it.

- The LIVER produces BILE, and stores it in the GALLBLADDER. Bile

is poured into the duodenum when the chyme arrives.

- The INTESTINAL GLANDS in the small intestine

walls produce INTESTINAL JUICE

- The LIVER produces BILE.

- Bile is stored in the GALLBLADDER until the food enters the small intestine. Then it

is poured into the duodenum.

- Bile has NO ENZYMES but it helps digestion by EMULSIFYING the fats (=breaking

them down in small droplets so they are easier to digest)

- The PANCREAS produces PANCREATIC

JUICE. This is poured into the duodenum when

the chyme arrives.

- PANCREATIC JUICE contains:

- sodium bicarbonate to neutralize the acidity of the chyme (it comes from the

stomach)

- enzymes to digest proteins, lipids and carbohydrates:

TRYPSIN and CHYMOTRYPSIN are proteases: breaks down proteins into

amino-acids

AMYLASE is a carbohydrase: breaks down starch into glucose

LIPASE breaks down lipids into fatty acids and glycerol

- In the SMALL INTESTINE 3 digestive juices finish the

digestion of the nutrients: bile, pancreatic juice, and

INTESTINAL JUICE.

- INTESTINAL JUICE contains enzymes that digest

carbohydrates, lipids and proteins.

- When digestion has finished, all the large molecules in our food are transformed into

smaller molecules:

Water, vitamins and minerals do not need to be digested.

AFTER DIGESTION... ABSORPTION- Digested food molecules have to pass through the wall of the small

intestine into the bloodstream, which carries them to the cells.

To make absorption easier, quicker and

more efficient:

- the small intestine's wall is very thin (only

one-cell thick)

- the inside wall of the small intestine has a

very big surface area thanks to tiny villi,

that contain the capillaries that absorb the

nutrients.

And with the undigested part of the food... EGESTION/DEFECATION

- The part of the foods that have not been absorbed in the small intestin, as well as

water, vitamins, minerals... enter the LARGE INTESTINE, where 3 processes

happen:

1) WATER is reabsorbed in the large intestine, going into the blood capillaries.

Minerals and vitamins are also absorbed here.

2) FAECES are formed with undigested food, fiber

and water. Faeces advance through the large intestine

thanks to the contractions of the intestinal walls, and

are finally released through the ANUS. This is called

EGESTION.

3) Some bacteria live in our large intestine

(INTESTINAL FLORA), and produce some vitamins

(K) that we can also absorbe and use.

LARGE INTESTINE:

1) REABSORPTION OF WATER

2) FORMATION OF FAECES AND EGESTION

3) VITAMIN SYNTHESIS BY THE INTESTINAL

FLORA