Digestion

Nutrition and Digestion



Why do all living things need food?

How do they get food?

How do they break it down so it can enter their cell(s)?

How does the food get to every cell in multicellular

organisms?

Producers vs consumers



 Autotrophs: Make own food

 Chemosynthesis (Archaea)

 Photosynthesis (Protists, plants)



 Heterotrophs: Cannot make own food

 Intracellular (within cell, Amoeba,

Paramecium)

 Extracellular (outside cell, molds, Hydra)

Let’s See…



 Autotrophs

More…

 Heterotrophs

Which are the

autotrophs?

The

heterotrophs?

The

decomposers?

 Intracellular digestion – takes place

inside a cell



 Extracellular digestion –large pieces of

food are partially broken outside cells:

 Within a special cavity, or

 Outside the organism entirely

Amoeba









Intracellular

digestion?

Or extracellular?

Paramecium



How does the food

get to the oral

groove?

What forms around

the food?

How is it digested?

How are wastes

expelled?

Mold

 Rhizopus- bread mold –

llike other fungi secretes

enzymes into food to

digest – then absorbs

nutrients.

Is it a producer? Or consumer?



How will the Venus

flytrap digest this fly?

Is this intra- or

extracellular

digestion?

Animals – Two-Way Traffic





 One opening to body; food enters and

waste exits same way

 Hydra





Intra- or extracellular?

Both

Food is Daphnia, a

small crustacean







Basal disc

Animals - One-way digestive tract

One Way Traffic cont.



 Two openings to body/digestive tract

 Mouth takes in food, anus expels waste



 Thorough, efficient digestion



 Earthworm, human, birds –

 complex multi-cellular animals

Earthworm digestion

How is surface area increased?



 How is the increased

surface area of the

intestine an

adaptation?

Earthworm

 Mouth – ingests & moistens food

 Pharynx – muscular contractions pull food from mouth

 Esophagus – muscular contractions push food to crop

 Crop – storage organ

 Gizzard – gravel & muscular contractions grind food to

small particles

 Intestine – enzymes digest food into small molecules

which are absorbed through intestinal walls.

 Anus – expels undigested material or “castings"

Physical vs. Chemical Digestion



 Physical  Chemical

 Food is broken down  Enzymes cause

into smaller pieces – large molecules

increasing surface break down into

area for chemical smaller molecules

digestion that can pass

through the plasma

membrane

Food intake patterns



 Chunk feeders

 Take in food in large pieces

 Require structures for physical/mechanical

digestion, e.g., teeth, gizzard

 Require enzymes to provide chemical

digestion, e.g., amylase, pepsin, lactase

Food intake patterns



 Filter feeders

 Feed on microorganisms and/or nutrients

floating in water

 Sessile or slow-moving



 Take water into body; filter out food; expel

water

 Include bivalves (clams, oysters) and

baleen whales

Sponges



 Cells with flagella draw water through pores

=food particles are filtered out

Clams, oysters, mussels

Human nutrition



 Complex molecules  Simple nutrients

– require digestion  Vitamins

 Proteins  Minerals

 Fats  Water

 carbohydrates

Human nutrition & digestion









Old version New version

Human nutrition









Do water, vitamins and minerals

need to be digested?

Why not?

Human Digestive System

Mouth– physical and chemical

digestion

 Teeth grind food into smaller pieces to

increase surface area

 3 pairs of Salivary glands secrete saliva

 Moistens food

 Starch amylase maltose

(polysaccharide) (disaccharide)

Pharynx & Esophagus



 Peristalsis – contractions of smooth

muscle move food to stomach

Stomach



Physical digestion:

Churning

Chemical digestion:

Pepsin + hydrochloric

rugae acid break protein down

into polypeptides.

Storage: Releases

chyme slowly into small

Mucous layer protects

intestine pH = 2

stomach from digestion!

Small intestine





Digestion is

completed –

Fats are

emulsified by

bile and then

digested by

lipase.

Nutrients are

absorbed

through walls of

villi into

bloodstream

Accessory Glands









Pancreas secretes pancreatic fluid Liver produces bile which is

containing enzymes: stored in the gall bladder

(emulsifies fats)

Trypsin – proteins to peptides

Amylase – starch to maltose

Lipase – fats to fatty acids +

glycerol

Large intestine





Water and salts

are reabsorbed.

What can be

dangerous

about having

diarrhea?

Feces stored in

anus rectum –

eliminated

through anus.

Enzymes in digestion