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 Food is broken down into smaller pieces – increasing surface area for chemical digestion Chemical Enzymes cause large molecules break down into smaller molecules 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 – require digestion Proteins Fats carbohydrates Simple nutrients Vitamins Minerals Water

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 acid break protein down into polypeptides. Storage: Releases chyme slowly into small intestine pH = 2 Mucous layer protects stomach from digestion! rugae

Small intestine Digestion is completed – Fats are emulsified by bile and then digested by lipase. Nutrients are absorbed through walls of villi into bloodstream

Pancreas secretes pancreatic fluid containing enzymes: Trypsin – proteins to peptides Amylase – starch to maltose Lipase – fats to fatty acids + glycerol Liver produces bile which is stored in the gall bladder (emulsifies fats) Accessory Glands

Large intestine Water and salts are reabsorbed. What can be dangerous about having diarrhea? Feces stored in rectum – eliminated through anus. anus

Enzymes in digestion